DERR-2024-012477

THIRD FIVE-YEAR REVIEW REPORT FOR KENNECOTT (NORTH ZONE) SUPERFUND SITE SALT LAKE COUNTY, UTAH
Prepared by Utah Department of Environmental Quality Division of Environmental Response & Remediation Salt Lake City, Utah --------------------------------- Aaron Urdiales, Director Superfund and Emergency Management Division

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Table of Contents
LIST OF ABBREVIATIONS & ACRONYMS ......................................................................................... ii
I. INTRODUCTION ................................................................................................................................... 1 Site Background ...................................................................................................................................... 2 FIVE-YEAR REVIEW SUMMARY FORM ......................................................................................... 3 II. RESPONSE ACTION SUMMARY ...................................................................................................... 3
Basis for Taking Action .......................................................................................................................... 3
Response Actions .................................................................................................................................... 4 Status of Implementation ........................................................................................................................ 4 IC Summary Table ................................................................................................................................ 11 III. PROGRESS SINCE THE LAST REVIEW ....................................................................................... 12
IV. FIVE-YEAR REVIEW PROCESS .................................................................................................... 15
Community Notification, Involvement & Site Interviews .................................................................... 15 Data Review .......................................................................................................................................... 16 Site Inspection ....................................................................................................................................... 18 V. TECHNICAL ASSESSMENT ............................................................................................................ 26
VI. ISSUES/RECOMMENDATIONS ..................................................................................................... 34
OTHER FINDINGS.............................................................................................................................. 39 VII. PROTECTIVENESS STATEMENT ................................................................................................ 40 VIII. NEXT REVIEW ............................................................................................................................... 41 Appendices
APPENDIX A - REFERENCE LIST APPENDIX B – SITE MAP
APPENDIX C – SITE INSPECTION CHECKLIST APPENDIX D – SITE INSPECTION PHOTOS APPENDIX E – STATE PERMIT REVIEW APPENDIX F – PUBLIC NOTICE & INTERVIEW FORMS Tables
Table 1.0: List of OUs……………………………………………………………………………………1
Table 2.0: Summary of Planned and/or Implemented ICs………………………………………………11 Table 3.0: Protectiveness Determinations from the 2019 FYR and the 2022 FYR Addendum………...12 Table 4.0: Status of Recommendations from the 2019 FYR and the 2022 FYR Addendum…………...13 Figures
Figure B-1: Site Vicinity & Institutional Controls Map …………………………………..…Appendix B

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LIST OF ABBREVIATIONS & ACRONYMS AOC Administrative Order on Consent Agencies EPA & UDEQ
ARAR Applicable or Relevant and Appropriate Requirement
BLL Blood Lead Level CAMU Corrective Action Management Unit CDC Centers for Disease Control and Prevention CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations COC Contaminant of Concern DAQ Utah Division of Air Quality DERR Utah Division of Environmental Response & Remediation DOGM Utah Division of Oil, Gas, and Mining DWQ Utah Division of Water Quality EC Environmental Covenant
EPA United States Environmental Protection Agency Region 8
ESD Explanation of Significant Difference FFS Focused Feasibility Study FYR Five-Year Review
GWPP Groundwater Protection Program HQ Hazard Quotient IC Institutional Control
KUALs Kennecott Unrestricted Action Levels mg/kg Milligrams per Kilogram mg/L Milligrams per Liter MOU Memorandum of Understanding NCP National Oil and Hazardous Substances Pollution Contingency Plan NPL National Priorities List O&M Operation and Maintenance O,M&R Operation, Maintenance, and Replacement
OU Operable Unit PM Project Manager PRP Potentially Responsible Party RA Risk Assessment RAGS Risk Assessment Guidance for Superfund RAO Remedial Action Objective RI Remedial Investigation ROD Record of Decision RPM Remedial Project Manager RSL Regional Screening Level RTK Rio Tinto Kennecott
SLCO Salt Lake County
SLCOHD Salt Lake County Health Department
USGS United States Geological Survey μg/dL Microgram per Deciliter
μg/L Microgram per Liter µg/Kg Microgram per Kilogram µg/m3 Microgram per Cubic Meter
UDEQ Utah Department of Environmental Quality
UPDES Utah Pollution Discharge Elimination System
UDNR Utah Department of Natural Resources
UU/UE Unlimited Use and Unrestricted Exposure

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I. INTRODUCTION
The purpose of a Five-Year Review (FYR) is to evaluate the implementation and performance of a remedy to determine if the remedy is and will continue to be protective of human health and the environment. The methods, findings, and conclusions of reviews are documented in five-year review reports such as this one. In addition,
FYR reports identify issues, if any, found during the review and document recommendations to address them. The Utah Department of Environmental Quality (UDEQ), Division of Environmental Response and Remediation
(DERR) prepared this FYR pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Section 121, consistent with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) (40 Code of Federal Regulations (CFR) Section 300.430(f)(4)(ii)), and considering policy of the United States Environmental Protection Agency Region 8 (EPA). This FYR has been prepared because hazardous substances, pollutants, or contaminants remain at the site above levels that allow for unlimited use and unrestricted exposure (UU/UE1). This is the third FYR for the Kennecott (North Zone) Superfund Site (Site). The triggering action for this statutory review is the completion date of the previous FYR.
The Site consists of seven Operable Units (OUs) addressed in this FYR.
Table 1.0 List of OUs Operable
Unit
Description
8 Includes the footprint of the RTK Waste Water Treatment Plant and Sludge Ponds, which were a former industrial wastewater treatment plant operation.
13 Includes the Garfield Smelter, associated facilities, and waste management areas, both historic and current.
14 Includes the historic and current refining facilities, associated facilities, and the footprint of waste management areas.

1 For the RTK sites, site specifc UU/UE action levels were established in 2015, please refer to Section I Site Background for more information.
The Kennecott North Zone Operable Units Risk Statements
Human Exposure Risk: On January 17, 2024, the EPA issued Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities that lowered recommended regional screening levels for lead-
contaminated soils in residential areas. The EPA and DERR will evaluate how this change may impact the cleanup that was conducted or is planned at the Kennecott North Zone site and determine if additional investigation and/or cleanup is needed. The EPA and DERR will share information on planned activities and results as they become available. Ecological Exposure Risk: Ecological exposure risks are in part addressed by the collection of groundwater with elevated
selenium concentrations at artesian springs and containment of such in Rio Tinto Kennecott’s (RTK’s) Process Water Circuit, ongoing management of wetland habitat for waterfowl, shoreline, passerine, and piscovorebirds, and careful selection of plant seed during reclamation efforts. Remedy protectiveness requires modification of certain selected remedies to address applicable contaminants of concern, threshold limits, and necessary response actions.

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Operable
Unit
Description
15 Includes the active North Tailings Impoundment and Arthur Step-Back Repository, along with the reclaimed South Tailings Impoundment, the footprints of the Bonneville Crushing and Grinding Mill, Magna Mill (North Concentrator), Arthur Mill, historic and current power plants and associated facilities and waste management areas. 19 Includes the Oquirrh Mountain Range and associated drainages, in both Salt Lake and Tooele Counties.
22 Includes portions of the Great Salt Lake and South Shoreline, associated wetlands, including springs and ponds, all located north and/or down gradient of the refining and smelting operations, and the Tailings Impoundment at the Kennecott North Zone.
23 Includes the groundwater in the bedrock, principal and shallow aquifers underlying OUs 8, 13, 14, 15, and 22.
Pursuant to the 2002 Record of Decision, OU9 was previously provided a no further action status. OUs 18 and 24 are both South Zone operable units and were recently evaluated in the 2021 South Zone FYR Report. This FYR was performed by Mazie Cox, DERR project manager (PM). Participants included Douglas Bacon, EPA Remedial Project Manager (RPM), Maggie Ogden, EPA Remedial Project Manager (RPM), Dave Allison (DERR), and Scott Everett (DERR). Participating staff from Rio Tinto Kennecott (RTK) included Teresa Cockayne, Kate Ruebelmann, Erdenebayar Naran, Chad VonHatten, and Bryn Howell. The review began on 5/23/2023.
Site Background
The Site is an industrial area at the north end of the Oquirrh Mountains and the south shore of the Great Salt Lake, next to the City of Magna. Interstate Highway 80, state highways, and rail lines pass through the Site. See June 17, 2014, FYR and Figure B-1 (Appendix B) for the approximate locations of the areas included in the OUs
addressed by this FYR and a more detailed description of the setting for each OU. Since 1906, the Site has been used to process copper, lead, zinc, molybdenum, arsenic, gold, and silver-bearing ores. The EPA became involved at the site in 1971. The early environmental dispute involved stack emissions at the Smelter. The next area of interest for the EPA was the treatment of smelter wastewater, which identified arsenic as a contaminant of concern. In 1990, cleanups began using federal Superfund funding, and negotiations began about the overall environmental cleanups needed. The full extent of contamination, the types of hazardous material present, and the total cost of cleanup for the Site were unknown at the time, which led the EPA, on January 18, 1994, to propose the Site to the National Priorities List (NPL). Pursuant to a September 1995 Memorandum of Understanding (MOU) between RTK, the EPA and
UDEQ, RTK agreed to complete numerous cleanup projects. In return, the EPA agreed to defer finalizing the listing of the Site on the NPL, and the UDEQ - Division of Water Quality (DWQ) agreed to use its groundwater authorities to regulate discharges from RTK’s active operations and waste management operations. Site contaminants of concern (COCs), as defined in the September 2002 Record of Decision (ROD) and the 2017 Explanation of Significant Differences (ESD), vary slightly across OUs based on the media type. The COCs are
arsenic, cadmium, lead and selenium for OUs 8, 13, 14, 15, 19 and 22 where remedial action is addressing soil, sediment, surface water, macroinvertebrate tissues, and solid mine waste, and the COCs are arsenic, selenium and sulfate for OU23 where remedial action is addressing contaminated groundwater. The overall site-cleanup strategy adopted in the September 2002 ROD was to address surface materials that posed a potential threat to industrial workers and wildlife resources through removal actions. This was to be followed by addressing long-term potential threats to workers and wildlife through treatment of groundwater, cleanup of currently inaccessible mining wastes following facility closure, and mapping of buried wastes for use by future
land use planners and developers. Detailed remedy descriptions, remedy implementations, and operational and

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maintenance (O&M) activities are summarized in Section II Response Actions for each OU and in the documents listed in Appendix A.
FIVE-YEAR REVIEW SUMMARY FORM
II. RESPONSE ACTION SUMMARY

Basis for Taking Action
The September 2002 ROD for all OUs with solid mine waste issues at the Site states that receptors at risk for exposure are industrial workers during their lunch hour or after work, construction workers, occasional visitors, and a few ranchers. An EPA contractor conducted a Human Health Risk Assessment which resulted in producing preliminary remediation goals detailed in the document entitled Final Preliminary Remediation Goals for
Addressing Risks to Human Health from Exposure to Chemicals in Kennecott Soils (December 20, 1999). A risk assessment task force composed of toxicologists and health professionals from the EPA, UDEQ, Utah Department of Health, Salt Lake County Health Department (SLCoHD), stakeholders from the communities, and RTK aided in the evaluation of the assumptions used in the risk assessment. The primary COCs in soils were lead and arsenic for human health and selenium for ecological impacts. Cadmium was later added to the list of human health
COCs. The September 2002 ROD recognized that groundwater contamination does not pose a current human health risk
because all of the water rights in the area are owned by RTK and the water is not used for culinary (i.e. drinking water) purposes. Due to the proximity to the Great Salt Lake, groundwater is not likely to be used for culinary purposes because of the high total dissolved solids (TDS) concentrations. The June 2014 FYR noted that there is
SITE IDENTIFICATION
Site Name: Kennecott (North Zone)
EPA ID: UTD070926811
Region: 8 State: UT City/County: Salt Lake County
SITE STATUS
NPL Status: Proposed
Multiple OUs? Yes Has the site achieved construction completion? No
REVIEW STATUS
Lead agency: State
Author name: Mazie Cox
Author affiliation: UDEQ
Review period: 5/23/2023 – 8/19/2024
Date of site inspections: 5/23/2023 – 2/20/2024
Type of review: Statutory
Review number: 3
Triggering action date: 8/19/2019
Due date (five years after triggering action date): 8/19/2024

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no current human exposure because groundwater is not a current or potential drinking water source. However, portions of the Site’s aquifers are potential sources of drinking water under both the State of Utah and Federal
groundwater classification schemes. UDEQ identifies the Smelter and Refinery areas as an area of potential drinking water as noted in the Aquifer Classification from the Utah Groundwater Protection Program, Plates 1-3. The EPA generally considers any groundwater with TDS <10,000 milligrams per liter (mg/L) to be potential drinking water. Additionally, wildlife exposures can be reduced to acceptable levels by diversion of the seeps and springs from sensitive habitats and treatment of the groundwater before discharge into the environment. As of this current FYR, revisions are pending to address groundwater use in the future, and modifications to the selected remedy for OU23 will be covered in a future decision document. The September 2002 ROD recognized that based on ecological risk assessments for the Site, with a focus on terrestrial receptor risk in OU19 and aquatic receptor risks in OU22, action was needed. A Site Biological Technical Advisory Group (BTAG) was formed to advise the EPA about the sensitive habitats and risks. Specific
to the uplands and mountain areas (OU19), the EPA concluded that soil removal in any of these areas was not advisable based on the fact that actions were unlikely to produce any long-term benefits and could destroy valuable wildlife habitat in the process. It was determined that the use of seeds of plant species known to uptake
selenium should be prevented during revegetation efforts. Specific to the OU22 North Zone Wetlands (NZW), it was determined that actions were required to address avian bird risks. Monitoring was implemented in the NZW to assess the success of the previous removal actions in the habitat. Monitoring to date has been inconclusive, and
as of this current FYR, revisions are pending to address the scope of the monitoring program by shifting the focus of such. The modifications to the selected remedy for OU22 will be covered in a future decision document. For more information on the basis to take action please review the September 2002 ROD and June 2014 FYR.
Response Actions
The overall site cleanup strategy adopted in the September 2002 ROD was to address surface materials that posed
a threat to industrial workers and wildlife resources through removal actions. This was to be followed by addressing long-term threats to workers and wildlife through treatment of groundwater, cleanup of inaccessible mining wastes following facility closure, and mapping buried wastes for use by future land-use planners and
developers. The principal threats, that were accessible, were addressed by a previous emergency response action under the EPA’s removal authority. These actions removed and/or capped soils, sediments, sludges and solid mine waste (with elevated COCs) to prevent ongoing contribution to groundwater contamination. Major
components of the selected remedies included (as cited in the September 2002 ROD):
• In-situ treatment of selenium-tainted groundwater coupled with the collection of contaminated spring and
well water for industrial use;
• Demolition of unneeded facilities, characterization of underlying soils, and removal of contaminated soils
to an engineered repository;
• Continued use of the Arthur Step-Back Repository to store contaminated soils following demolition
activities and/or following facility closure;
• Development of a monitoring plan to evaluate progress toward ecological improvement; and
• Mapping of locations of buried wastes and locations where future unrestricted land use is not appropriate.
Detailed remedy descriptions, remedy implementations, and O&M activities are summarized below for each OU .
Status of Implementation
OU-specific remedy descriptions, remedy implementation statuses, and O&M requirements are summarized below for each OU for which the September 2002 ROD specified further action. OU8 Waste Water Treatment Plant and Sludge Ponds

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Remedy Description: Remedial actions described in the September 2002 ROD for OU8 were to prevent groundwater contamination through the removal or capping of leachable materials, elimination or containment of
contaminated materials that washed down into sensitive wetland habitats, and the elimination or prevention of exposure of contaminants to wildlife, especially wetland birds. In addition to previous cleanups during the early removal actions, additional remedial actions were required under the September 2002 ROD. Groundwater monitoring is required as part of the remedy at OU23 North End Groundwater to evaluate the effectiveness of groundwater source control measures in the sludge pond area (OU8). RTK is required to provide maps showing
locations of buried wastes above the EPA’s action levels for industrial land use and unrestricted land use.
Remedy implementation: In 2001, cleanup actions were taken at OU8 including the demolition of the Waste Water Treatment Plant (WWTP), soil characterization and removal at the WWTP site, and sludge removal from five sludge storage ponds (i.e. A, B, C and C+, and D). Water treatment sludges removed from Ponds A, B, C and C+, and D were placed in the Arthur Stepback Repository. Please see the September 2002 ROD for further specified actions for the WWTP and Sludge Ponds. Ponds A and D were specifically located within the North Zone Wetlands Habitat (OU22). The storage of sludge in these ponds contributed directly to groundwater and surface water impacts. With the removal of the sludge from Ponds A and D, both surface water and groundwater impacts were mitigated. These locations also began backfill with groundwater and became surface water ponds in the OU22 NZW. Surface water monitoring (along with monitoring of sediment, macroinvertebrate tissue and, recently, other biological media including bird eggs) has continued since 2003 at OU22 under an approved work plan (amended in 2008, 2014, 2020). Results of the monitoring are discussed below in Section IV Data Review. Groundwater monitoring continues as part of the remedy at OU23. Results of monitoring are discussed below in Section IV Data Review. The monitoring in OU22 and OU23 is in part assessing the successfulness of the
removal of the sludge at OU8. Maps of the geographic boundaries of OU8 have been provided to the Agencies. The map will require ongoing refinement to account for where soils are located above the site-wide unrestricted land use action levels (refer to the Agencies Technical Memorandum dated December 29, 2015).
O&M: RTK has, to date (since the initial removal action), managed soils exceeding the cleanup standards listed under the September 1996 Administrative Order on Consent (AOC) pursuant to September 2002 ROD and 2017 Explanation of Significant difference. Soil management is performed under the 1996 AOC work plan and the pending Site Wide Operational Soils Management Plan (Site Wide OSMP, previously entitled the Future Encountered Soils (FEW) Plan). Depending on whether construction projects are located in areas with soils exceeding the site-specific, unrestricted land use or industrial land use action levels, the soils are managed either on site or placed into the Arthur Step Back Repository (OU15). Ongoing O&M (i.e, land use control and soil management) is performed by RTK under the August 2019 Site-Wide Management Plan for Waste Left in Place (2019 Site Wide WLIP) for inactive areas of the North Zone and the pending Site Wide OSMP for active operational areas (as stated under the 2017 ESD). Ongoing groundwater monitoring is discussed under OU23, and wetlands monitoring is discussed under OU22. OU13 Smelter and Acid Plants, OU14 Refinery, OU15 Mills and Tailings Pond
Remedy Description: The September 2002 ROD included the following elements under the remedies selected for OU13, OU14 and OU15:
• Following facility closure and demolition, soils in the area are to be characterized and removed as needed to the Arthur Step-Back Repository, the on-site landfill for contaminated waste. Generated RCRA wastes
must be recycled or removed to an approved off-site facility.
• Soils to remain in place that exceed the unrestricted land use standards are to be covered with at least 18 inches of clean fill, graded and re-vegetated. If leachable soils with COCs remain in place, an engineered cap to reduce infiltration is required.
• RTK should provide maps showing locations of buried wastes above the EPA’s action levels for industrial land use and unrestricted land use. Maps of the geographic boundaries of the operable unit have been provided to the Agencies. The maps will require ongoing refinement to show where soils are located above the site-wide unrestricted land use action levels (refer to 2017 ESD).

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• OU13 only: Further CERCLA response action for any residual contaminated groundwater may be required at the Former Acid Tank Farm to prevent the migration of sulfuric acid and its residues from entering the wetland.
• OU14 only: Further CERCLA response action may be required at the former Precious Metals Plant at the time of facility closure. At a minimum, the current cap over the former metals plant must be extended to cover the remaining wastes currently inaccessible underneath the current tank house of the new refinery.
• OU15 only: RTK can use the Arthur Step-Back Repository (ASR) as a corrective action management unit (CAMU). Following the closure of site facilities, decommissioning and final remediation, the entire repository will be closed permanently, and RTK will enter into an Environmental Covenant (EC) for the area. A supplemental repository may be designed and constructed if the remaining capacity of ASR is exceeded.
Remedy implementation: RTK has implemented and continues to implement the general removal actions specified in the September 1996 AOC work plan. Discrete soil management projects took place under the AOC and its amendments. Post-removal action sampling determined that the action levels under the September 1996
AOC work plan were attained and are protective of current land use. Groundwater monitoring is occurring as part of the remedy at OU23. Maps of the geographic boundaries of these OUs have been provided to the Agencies. The maps will require ongoing refinement to show soils located above the site-wide unrestricted land use action
levels (refer to the 2017 ESD). In 2009, a new release of low pH solutions took place at the Acid Tank Farm Loading Station located at the east
end of the Smelter, OU13. Based on characterization data, the Division of Water Quality (DWQ), DERR and the EPA agreed that groundwater would be monitored where surface water quality can be influenced by the release of acidic solutions and increased metals (i.e. selenium) concentrations. DWQ has continued to oversee RTK’s corrective action required under the Smelter Groundwater Discharge Permit in response to the release. O&M: RTK operates and maintains the Arthur Step-Back Repository under the requirements of Rio Tinto
Kennecott Copper – Environmental Land and Water Ground Arthur Stepback Repository Operations and Maintenance Plan Kennecott North Zone Site (2018 ASR O&M Plan) dated June 2018. Ongoing post-Final Remedial Design (RD) Remedial Action (RA) Consent Decree (CD) O&M addressing soil and solid mine waste management for the broader OUs will be conducted by RTK via the 2019 Site Wide WLIP or the pending Site Wide OSMP.
As part of this current Five-Year Review, RTK submitted the Arthur Stepback Repository Summary for Third Five-Year Review, Kennecott North Zone (ASR Summary Report). RTK has deposited a total of 1,270 cubic yards of material in the ASR since the beginning of 2020. The site-wide small soil management projects were the source of the majority of deposited material, with a total of 922 cubic yards. A total of 4,365,631 gallons of leachate has been removed from the repository, equaling 13.4 acre-feet. The leachate was collected from the sumps
constructed at the Arthur Stepback Repository as part of the facility leachate collection system. RTK installed three monitoring wells (NET1490, NET1491 and NET1492) down-gradient of the ASR to detect possible impacts to groundwater from the repository’s operations. During 2019-2023, monitoring well NET1491 detected selenium concentrations above the groundwater protection levels established by DWQ and listed in the GWPP Discharge Permit UGW350011. RTK identifies this exceedance as an isolated incident as the selenium concentrations were lower in subsequent analyses.
Active processing facilities and reclamation of the inactive portions of these OUs are conducted in compliance with permits issued by DWQ, the Division of Air Quality (DAQ), and the Division of Oil, Gas, and Mining (DOGM). Under the 1995 MOU, the active processing operations, waste management activities, and closure of these facilities should maintain compliance with these permits where applicable. The use of these permits to regulate the active operations and manage legacy waste of interest to CERCLA is currently under re-evaluation
under the pending State Permit Gap Assessment. Refer to Appendix E for reports from the state and county permitting authorities concerning RTK’s compliance with other permit limitations over the past five-year period.

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OU19 Smelter Fallout Remedy Description: The September 2002 ROD included the following elements under the remedy selected for
OU19:
• Map areas where the concentrations of the COCs exceed land use standards or pose an increased risk of observable effects to either ecological or human receptors.
• During re-vegetation efforts in the canyons, prevent the use of plants that can up-take selenium.
• Areas that have the potential to pose a threat dependent upon future land use will be segregated and scheduled for appropriate response action at the time of future land use change.
• If the canyon areas are mined for sand, gravel and/or topsoil, no material above the site-wide unrestricted land use action levels can leave the site. On-site use of material must be appropriate for the land use.
Remedy implementation: Maps of the geographic boundaries of the operable unit have been provided to the Agencies. The map will require ongoing refinement to account for soils located above the site-wide unrestricted land use action levels (refer to the 2017 ESD). RTK avoids the intentional use of seed mixes that include plant species that can concentrate selenium and, therefore, posing a risk to herbivore and omnivore species. Pursuant to the 2019 Site Wide WLIP an EC will be placed on the land once RTK intends to divest its interest in its ownership. To date, an EC has not been placed on the land in OU19. O&M: RTK maintains the canyons south and east of the Smelter as open space and sources of borrow material for
on-site projects. Prior to the shipment of borrow material around the Site, RTK monitors the soils for metals concentrations (though formal work plans do not exist) to ensure the soil metal concentration is protective of the intended land use where it will be placed on site. RTK also restricts the use of seeds of plants that can uptake
selenium. The 2019 Site Wide WLIP and the pending Site Wide OSMP restrict seed use, as well, address sampling protocols for the soils when excavated by RTK.
An active gravel pit operation, Black Rock Gravel Pit, is operating in OU19 (specifically in the lower portion of Black Rock Canyon located west of the smelter). Pursuant to the remedy selected under the September 2002 ROD for OU19, RTK is responsible for ensuring extracted materials (i.e. sand, gravel) above the site-specific unrestricted action levels (refer to the December 29, 2015, Technical Memorandum) are not taken off site during proposed sand and gravel operations. In 2021, RTK had the operator coordinate with the UT DERR to submit a soil management plan to ensure that excavated material did not contain arsenic or lead concentrations above the site-specific unrestricted land use action levels. Please refer to Section IV Site Inspection for further information on the Black Rock operations. OU22 Great Salt Lake, Shoreline Wetlands, and OU23 North End Groundwater For purposes of this five-year review, OU22 and OU23 are discussed together due to their hydraulic
interconnectedness and because the groundwater for OU23 is the subject of an ongoing Focused Feasibility Study (FFS).
Remedy Description: The selected remedy for OU22 in the September 2002 ROD is focused on response action and protection measures necessary to reduce or prevent avian exposure risks from elevated concentrations of COCs located in the North Zone Wetlands (NZWs). This includes monitoring and analysis of water, sediment and
macroinvertebrate tissue. The remedy included provisions to suspend monitoring after meeting specific macroinvertebrate selenium concentration requirements and options to take a surface water pond(s) in the NZWs out of service by converting the habitat. The selected remedy also requires ongoing macroinvertebrate sampling when macroinvertebrate selenium concentrations exceed 5 mg/kg and/or 10 mg/kg. In addition to monitoring, RTK is required to initiate efforts to complete a selenium source assessment and abate such which could include further sediment removal. The OU23 remedy requires ongoing monitored natural attenuation of the delineated selenium and arsenic plumes underlying the Smelter (OU13) and Refinery (OU14), ongoing assessment of seeps and springs, and capturing groundwater when it surfaces. Furthermore, Garfield Well #5 was to be used to extract the refinery selenium

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plume along its leading edge and the selected remedy required in-situ treatment of groundwater with elevated selenium upon closure of the smelter and refinery.
Remedy implementation: At OU22, RTK has monitored concentrations of COCs in water, sediment and macro-invertebrate tissues collected from established monitoring locations in the nesting and foraging habitat within the NZWs. Some of the initial monitoring locations (2003 North Zone Wetlands Monitoring Plan) were suspended based on analytical results documenting selenium concentrations of less than 5 milligrams per kilogram (mg/kg) (September 2002 ROD) in the macroinvertebrate tissue samples for a period of three years as recently as 2009. In 2008 (and repeated in 2014, 2017, 2020, 2022 and 2023), RTK voluntarily began monitoring bird eggs to assess selenium concentrations for three feeding guilds (shorebirds, waterfowl and passerines) and in 2022 added a fourth feeding guild (piscovore). Selenium is a teratogen affecting the survival of the chicks of the resident and migratory avian community that use the NZW habitat for nesting and foraging. Because of the effect on the chick
from selenium, the Utah Division of Water Quality (DWQ) and relevant literature recognize the whole egg as the appropriate media to be sampled. The October 2022 FYR Addendum noted that a review of the bird egg data collected through 2022, determined when the selenium egg data from four feeding guilds (waterfowl, shoreline,
passerine and piscovore) using the NZW are combined, a linear regression of the overall geomean selenium concentration documents an increasing concentration trend. When the geomean linear regression assessment is completed for each of the four feeding guilds, selenium concentrations increased for one (shoreline) while
selenium concentrations decreased for the other two (waterfowl, passerine). Two years (2022 and 2023) of limited bird egg selenium data for the piscivore avian species does not support a linear regression trend analysis at the time of this report. Since 2008, surface water quality data has documented elevated concentrations of arsenic in portions of the NZWs exceeding the DWQ surface water quality standard for Class 3D water of 150 parts per billion (ppb) (UAC R317-2-14). Utah’s Class 3D surface water quality standards are protective of waterfowl, shorebirds, and other water-oriented wildlife not included in classes 3A, 3B, or 3C, including the necessary aquatic organisms in their food chain. Though the NZWs have not been classified, the Class 3D standards could be applied as a protection threshold, given the avian use of the NZWs and that under UAC R317-2-13, unclassified waters are presumptively classified as Class 3D.
The selected remedy for OU22 and the NZWs does not have a protection threshold limit for arsenic nor does it specify that arsenic is a COC. It is anticipated that a modified remedy will address this. Under a decision document, both UAC R317-2-13 and UACR317-2-14 could be listed as Applicable or Relevant and Appropriate Requirements (ARARs) to adopt a protection threshold limit for arsenic in the NZWs. After a decision document is finalized, a long-term Sampling and Analysis Plan and Quality Assurance Project Plan (SAP/QAPP) would be
required to cover ongoing sampling of surface water in the NZWs to monitor arsenic concentrations. A modified remedy would also include response actions, if the protection threshold limit for arsenic is exceeded, under an operation, maintenance and replacement (O,M&R) plan.
Since 2010, RTK, the EPA, and UDEQ have investigated the historic footprint of a test causeway dike, constructed of copper tailings in 1965, located on the southern shore of the Great Salt Lake. By 1968, the tailings
dike was considered a failure because the tailings construction material did not hold up to erosion. Today, not much remains of the tailings dike but for some armoring rock, transit pipe supports, and in some locations, oxidized tailings in the subsurface along the surface of the southern shore. Based on the nature and extent of
ecological risk screening completed by RTK, the Agencies determined there is a potential for ecological exposure risk. However, the tailings’ dike habitat is small and bird surveys found limited use by avian receptors. The Agencies have, on an interim basis, determined that the tailings dike should continue to undergo FYR assessments in the future to observe changes in use activities by potential ecological receptors and the public. This review found no use changes. The habitat remained limited with sparse vegetative cover north of the start of the tailings dike (see Section IV Site Inspections for more detail).

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In 2009, Garfield Well #5 was investigated as it had not fully contained the selenium plume. It was determined that Garfield Well #5 was not intact, portions of the casing had been corroded, and it was sealed and abandoned
pursuant to the Utah Department of Natural Resources’ (UDNR) well-abandonment regulations, managed by the Division of Water Rights (DWR). In 2009, RTK evaluated, through a pilot study, an in-situ bioremediation project at the smelter to reduce selenium in groundwater from selenite to selenate. The pilot project was determined to be unsuccessful due to the difficulty of keeping the selenium-reducing microbe community sustained and because it mobilized arsenic before establishing a selenium reduction zone. Since 2003, RTK has performed ongoing monitoring, assessment, capture and control of groundwater at artesian springs. Groundwater with selenium concentrations greater than 50 µg/L (human health) is captured at the surface and managed in RTK’s Process Water Circuit. The selected monitored natural attenuation remedy for OU23 has not progressed in the time frame originally modeled and reported on in the 2000 Remedial Investigation (RI) Feasibility Study (FS). Since 2010, RTK updated the original OU23 RI (completed in 2013) and completed an FFS in 2020 focused on
the refinery portion of OU23, which remains under review by the EPA and DERR.
The groundwater contaminant source zones at the refinery continue to be evaluated by RTK, to refine the fate and transport pathways of groundwater into the NZWs, as the FFS report continues to be developed by RTK. The FFS report will require EPA approval. O&M: RTK continues to monitor the NZWs and the groundwater aquifers underlying the Northern Oquirrh Mountains around OU13, OU14, OU15 and OU22. Monitoring of the NZWs continues under the 2003 monitoring plan, as amended in 2008, 2014 and 2020, which includes enhanced biological (i.e. bird eggs, fish tissue, etc.) monitoring. Groundwater monitoring is completed under the site-wide Groundwater Characterization
and Monitoring Plan (GCMP) (which was last updated in 2016 as overseen by the DWQ GWPP). The GCMP has been used for all groundwater monitoring associated with DWQ GWPP permits.
RTK has performed monitoring of bird eggs on a voluntary basis to date. The collection and analysis of bird egg samples is not part of the existing selected remedy. The bird egg monitoring performed to date has not achieved the collection of a statistically representative number of eggs to support conclusive trend assessments for selenium in bird eggs in the NZWs. RTK continues to implement ongoing monitoring of water, sediment and macroinvertebrate samples collected from the NZWs. It should be noted that though there are remedial action benchmarks for selenium concentrations in the macroinvertebrate samples, there are no threshold limits for arsenic in surface water. Samples to date have demonstrated elevated arsenic concentrations in the surface waters of the NZWs. Please refer to Section IV – Data Summary for more information. Groundwater monitoring data has demonstrated that groundwater in OU23 has not responded as predicted in the 2000 RI/FS. Since 2010, a re-evaluation of the RI and FS (resulting in a RI Update report (2013) and FFS report) has evaluated further alternatives to address the delayed attenuation of metals in the groundwater system. Monitoring since 2018 has also suggested the nature and extent of the arsenic plume underlying the Smelter has expanded beyond what the conceptual site model denoted in 2000 (refer to Section VI – Data Summary for more
information). The September 2002 ROD did not include a concentration limit for arsenic or selenium in groundwater under the selected remedy. The selected remedy did not focus on a direct consumption pathway for the impacted groundwater, as an institutional control (IC) was selected to prevent such. The selected remedy
requires capture of groundwater, when the groundwater daylights at various artesian springs and seeps, and management the water in RTK’s Process Water Circuit (refer to Section V – Technical Assessment for more information). Short-term monitoring at OU22 is currently taking place (as noted) under the 2003 monitoring plan, as amended in 2008, 2014 and 2020 (to add bird egg sampling). Ongoing monitoring at OU23 continues (as noted) under the GCMP that was last updated in 2016 with oversight by the DWQ GWPP. ARARs: The September 2002 ROD identified the applicable or relevant and appropriate requirements (ARARs). Certain state ARARs identified in the September 2002 ROD are applicable or relevant and appropriate for future response work when facilities are decommissioned or the active mine shuts down. Other ARARs pertain to the

10
control of fugitive emissions under the Utah Air Conservation Regulations and the generation, transport and disposal of hazardous waste under the Utah Hazardous Waste Regulations. All ARARs listed in the four site-
related RODs were re-evaluated, and the Agencies’ review culminated in a March 16, 2016, Technical Memorandum that included a comprehensive list of the ARARs that apply to the selected remedies. Site-Specific Action Levels: Site-specific land use action levels have been selected in the September 2002 ROD for the various operable units of the Site where soils are elevated for metals of concern. Similarly, groundwater protection or site-specific cleanup levels for groundwater have been selected for OU22 and OU23 where
groundwater daylights. The Agencies’ December 29, 2015, Technical Memorandum summarizes all applicable site-specific developed action levels for soils and groundwater contaminants. Institutional Controls: The selected remedies for OUs 8, 13, 14, 15, 19 and 22 include the use of ICs that RTK implements (pursuant to the 2017 ESD) under the 2019 Site Wide WLIP and the pending Site Wide OSMP. The 2019 Site Wide WLIP requires RTK to place on a property’s deed, an EC prior divestment of property ownership when soils contain COC concentrations above the site wide unrestricted land use action levels. As part of the selected remedy (September 2002 ROD) for OU23, RTK is required to place a drilling restriction over the impacted aquifer area to prevent consumption of the mining-influenced groundwater. Lastly as noted in the 2017 ESD, property in private ownership with soils containing concentration of COCs above the site wide unrestricted land use action levels is managed by the Salt Lake County Health Department and the Salt Lake County Metro Service District when building permits and excavation permit applications are submitted during redevelopment. The instrument for these ICs are provided in Table 2 below.

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IC Summary Table 2: Summary of Planned and/or Implemented ICs
Media, engineered controls, and areas that do not support UU/UE based on current conditions
ICs Needed
ICs Called for in the Decision Documents
Impacted Parcel(s) IC Objective
Title of IC Instrument Implemented and Date (or planned)
Groundwater Yes Yes
The extent of groundwater impacts underlying and emanating from RTK facilities
Restrict installation of groundwater wells
Pursuant to Utah Code Sections 57- 25-101 to 57-25- 114 RTK intends to file a drilling restriction environmental covenant (to be appended to the Site-wide Management Plan for Wastes Left in Place)
Soil, sediment, and solid mine waste left in place Yes Yes Operable Units 8, 13, 14, 15, 19
Limit land use to industrial and open space unless further response work is initiated under oversight by the Agencies
Pursuant to Utah Code Sections 57- 25-101 to 57-25- 114 RTK intends to file an EC restricting land-use change environmental (to be appended to the 2019 Site Wide WLIP)
Soil, sediment, and solid mine waste left in place Yes Yes Operable Units 8, 13, 14, 15, 19
When property is divested by RTK in these operable units,
local jurisdiction land planners will ensure soils are managed using local land use ordinances
Salt Lake County Health Department pursuant to Title 9, Chapter 9.5, will coordinate with UDEQ to ensure (as needed) soils are managed during building and excavation projects.
Notes: a. Administrative rule accessible at: https://le.utah.gov/xcode/Title57/Chapter25/57-25.html

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III. PROGRESS SINCE THE LAST REVIEW This section includes the protectiveness determinations and statements from the last five-year review as well as the recommendations from the last five-year review and the current status of those recommendations.
Table 3: Protectiveness Determinations from the 2019 FYR and the 2022 FYR Addendum
OU # Protectiveness Determination Protectiveness Statement
8, 13, 14, 15,
and 19
Short-term Protective The remedies at these operable units are protective of human
health and the environment for the short term. In non-operational areas, wastes (soils, sediments, solid mine waste with concentrations of the contaminants of concern above site-wide
unrestricted land use action levels) left in place are managed by the current land owner (RTK) under their Site-Wide Management Plan for Wastes Left in Place. In operational areas, a similar site-
wide management plan is still pending. Under both management plans the development of discrete project related soil management plans, updates to mapping, inspections and reporting, maintenance of covers and engineered caps, seed control and land use management does and will take place. Post-mine closure and divestment of land holdings will require these locations to be managed under a functional soils ordinance vested with local land planners to ensure proper management of soils, sediments and solid mine wastes exceeding the site-wide unrestricted land use action levels during proposed land use changes.
22, 23 Not Protective Given the uncertainties concerning the fate and transport of selenium in the groundwater system underlying the Refinery complex, the inability of the current capture system to effectively manage the selenium-impacted groundwater, the rising concentrations of selenium in bird eggs, and the lack of evaluation of appropriate measures to reduce the toxicity and leaching potential of source material, the selected remedies for OU22 and OU23 are currently not protective. For the remedy to be protective, the increasing trend in selenium in bird eggs and arsenic in surface water needs to be addressed. This will involve source control alternative development under the OU23 FFS;
short-term additional bird egg sampling in the NZW; continued monitoring of surface water, sediments, and macroinvertebrates in the NZW; and approval and implementation of a long-term
sampling and analysis program including a quality assurance project plan for OU22.

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Table 4: Status of Recommendations from the 2019 FYR and the 2022 FYR Addendum
OU # Issue Recommendations Current Status
Current Implementation Status Description
Completion Date (if applicable)
8, 13, 14, 15 and 19 In 2016, Salt Lake County's governance
structure was changed, which affected Salt Lake County’s ability to address pre-screening of land
disturbance projects in areas of the Kennecott North Zone with waste left in place exceeding the site-
wide unrestricted land use action levels. Though these
operable units will be subject to environmental covenants implemented by RTK while the properties
are held by RTK, upon cessation of operations and property divestment, institutional controls as in the Salt Lake County Health Department’s listed
in Title 9 Chapter 9.5 will need to be implemented including as noted pre-screening projects to assess the need for further information.
DERR should coordinate with the
Salt Lake County Health Department to address solutions to the pre-screening issue
and implementation of their ordinance.
Ongoing DERR has been coordinating with the
Salt Lake County Health Department through regular meetings to discuss
solutions to the pre-screening issue and implementation of the ordinance. This
coordination will be ongoing until an
appropriate solution has been agreed upon and will continue to ensure the solution is
being implemented as intended.
NA
8, 13, 14,
15, 19
As noted in the 2017 ESD,
RTK will update the GIS maps which are to
document where soils, sediments, and solid mine waste with concentrations of contaminants of concern
above site-wide unrestricted use action
levels are located, and update such on a minimum of every five years.
RTK should continue
to perform the map update role by
incorporating data into the GIS database to develop refined boundaries where
these soils, sediments, and solid mine wastes
are left in place and provide updates by the next review in the form of institutional
control boundary data layers.
Under
Discussion
At the time of this
current FYR, the Agencies have
requested an updated GIS map layer from RTK. The submission of the updated GIS
map layer is pending.
NA

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OU # Issue Recommendations Current Status
Current Implementation Status Description
Completion Date (if applicable)
8, 13, 14, 15, 19 In operable units where there are active operations, the management of soils along with maintenance of engineering controls,
implementation of ICs, inspections, and reporting on maintenance actions is not covered under an active operations and maintenance plan.
RTK will complete the pending Site Wide OSMP, which in part, will cover maintenance of
engineering controls, implementation of proprietary institutional controls, development of site-specific work plans to
address further soil management, and control of seeds of plants capable of up-taking selenium.
Ongoing The pending Site Wide OSMP is undergoing further revision by RTK.
NA
22 The current selected remedy does not include a
protection threshold limit for selenium in bird eggs or a surface water standard for arsenic.
The EPA and DERR need to revise the
remedy to incorporate a selenium protection threshold for bird eggs and a surface water standard for arsenic.
Ongoing An updated remedy will be documented
in a decision document.
NA
22 It is unclear if the increasing trend of selenium in the bird eggs is a statistically significant
trend due to the small sample size.
Additional bird egg samples need to be collected.
Ongoing RTK continues to collect bird egg samples.
NA
22 Long-term monitoring of
bird eggs and other media in the NZW under a revised remedy requires an SAP/QAPP to ensure
statistically significant data is collected.
RTK, the EPA, and
DERR need to collaborate and approve long-term SAP/QAPP monitoring.
Ongoing A long-term
SAP/QAPP will be developed upon issuance of a revised remedy in a decision
document.
NA
22 & 23 The groundwater plumes in
the North Zone groundwater contain elevated concentrations of arsenic. Surface water in
the NZWs also contains elevated concentrations of
arsenic. Arsenic is currently not a contaminant of concern under the selected remedy.
The EPA and DERR
need to revise the remedy to incorporate a surface water protection standard for
arsenic, and a cleanup standard for arsenic in
the groundwater.
Ongoing An updated remedy
will be documented in a decision document.
NA

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OU # Issue Recommendations Current Status
Current Implementation Status Description
Completion Date (if applicable)
23 The refinery selenium plume is not decreasing under the MNA remedy. Further short- and long-term site management
alternatives need to be selected to ensure plume reduction.
EPA and DERR need to assess alternative source control and plume management response actions, and
then modify and update the remedy decision document.
Ongoing Currently, the Agencies and RTK are engaged in evaluating revisions to the draft FFS.
NA
IV. FIVE-YEAR REVIEW PROCESS

Community Notification, Involvement & Site Interviews
A public notice was made available in the Salt Lake Tribune newspaper on February 25, 2024 (see Appendix F).
The notice stated that the Five-Year Review was starting and invited the public to participate. The results of the review and the report will be made available at the Site information repository located at DERR, 195 North 1950 West, 1st Floor, Salt Lake City, Utah, and at http://eqedocs.utah.gov.
The DERR conducted community interviews with RTK project managers; the Utah Division of Forestry, Fire, and State Lands; Salt Lake County Health Department; City of Magna; Great Salt Lake Audubon stakeholders; Physicians for a Healthy Environment; and Ivan Weber, a concerned citizen and consultant. Teresa Cockayne and Erka Naran, RTK Project Managers: The RTK Project Managers discussed the ongoing soil and groundwater remediation at the Site. The RTK Project Managers provided an update on RTK’s operations, remediation efforts, and regulatory compliance. Both highlighted the ongoing collaboration with regulatory agencies, the importance of environmental controls, and the company's commitment to completing the remediation process. Marisa Weinberg, Division of Forestry, Fire, and State Lands (FFSL): The FFSL expressed their concern about the potential ecological and hydrological connections between the Superfund site and the Great Salt Lake, particularly concerning groundwater and bird populations. They also mentioned their concern about the potential
for toxic minerals from the Site to contribute to lake bed dust generated off the Great Salt Lake. The FFSL mentioned that the broader community interested in the conservation of the Great Salt Lake has general concerns about the impact of contaminants on water quality, bird ecology, and the overall health of the Great Salt Lake.
They discussed their involvement in the site planning efforts at Black Rock and the need for continued transparency and collaboration between RTK and stakeholders.
Hayley Shaffer and Neil Offerman, the Salt Lake County Health Department (SLCoHD): SLCoHD Staff conducts routine inspections of the SLCo permitted landfills on the Site, and has not received any complaints or observed violations in the past five years. They also discussed regular communication with other agencies and have not encountered any issues or received any complaints from the public regarding the Site. Eric Barney, Mayor of Magna: Mayor Barney expressed concerns about the lack of transparency and communication from RTK regarding the Site. The Mayor highlighted issues such as the expansion of the Tailings Impoundment facility, dust generated off the Tailings Impoundment, access to the mountains, and the impact of the railway on the community. The EPA and state representatives acknowledged the need for better communication and offered to schedule regular meetings to address the Mayor's concerns and provide updates on the Site's activities.
The Great Salt Lake Audubon and Physicians for a Healthy Environment: The meeting focused on discussing the environmental impact and management of the Site, with particular attention to the selenium and arsenic
contamination affecting local wildlife and water quality. Stakeholders, including representatives from Audubon

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and environmental groups, expressed concerns about public awareness, dust from tailings, and the potential cumulative effects of contaminants. Suggestions for improvement included more rigorous monitoring of the food
web, better community engagement, and proactive measures from RTK to mitigate ecological and human health impacts.
Ivan Weber, concerned citizen and environment consultant: Mr. Weber responded to the public notice and requested participation to learn more and to share his professional experience regarding remediation strategies and the Site. Mr. Weber advocated an urgency in every category and scale to prevent pollution and contaminants introduced into the environment.
Data Review
There have been no large- or small-scale soil cleanup projects at the Kennecott North Zone (OU8, OU13, OU14, OU15, OU19 and OU22) operable units over this five-year review period. Previous soil action levels (summarized
in the December 2015 Technical Memorandum issued by the EPA and DERR) are still applicable. As noted
above, the EPA’s January 2024 Updated Soil Lead Guidance recommends new residential lead soil screening levels. As a result of the updated guidance, site-specific unrestricted, residential and recreational use action levels
for lead warrant a re-evaluation. Pursuant to the 1995 MOU and the September 2002 ROD, active operations, waste management activities, and
closure of facilities should comply with UDEQ permits issued by various state and local agencies for the operating facilities operating in the operable units. This will prevent active operations from exacerbating existing legacy mine waste being addressed under the CERCLA selected remedies. The EPA and DERR reviewed RTK’s compliance with permits issued by the UDEQ and the SLCoHD for active operations and determined RTK maintained compliance with its permit requirements except for concerns raised by DWQ’s GWPP (Appendix E). The DWQ GWPP permit for the Tailings Impoundment (OU15) complex (#UGW350011) had a number of compliance issues related to the groundwater monitoring wells. In its operation and maintenance summary report for the Arthur Stepback Repository (also covered by the GWPP permit for the Tailings Impoundment), RTK notes a compliance well was out of compliance with the GWPP permit selenium limitation. There are other issues under the GWPP permit for the Tailings Impoundment that are noted in Section V and VI. These compliance issues are currently being evaluated by DWQ (under a source area assessment) and should be re-evaluated in the next five-
year review. Refer to Appendix E for reports from the permitting authorities as it pertains to RTK’s compliance with permit and bonding limitations for active operating facilities in the Kennecott North Zone. This report includes a review of relevant, site-related documents referenced in various sections. Appendix A provides a
complete list of documents reviewed. Ongoing monitoring of the OU22 NZWs continued from 2019 to 2024. Reporting of annual monitoring data is
not currently required as part of the selected remedy. Reporting of future monitoring is currently being discussed. As part of the monitoring, surface water, sediment, macroinvertbrate tissue, bird eggs and, on an opportunistic basis, fish tissue and other biological media (such as amphibians, reptiles samples) are collected. Though a suite of metals analysis is performed, to date, the Agencies focus on selenium concentrations in the macroinvertebrate tissue samples, selenium in the bird eggs, and arsenic in the surface water. An evaluation of reported surface water data determined that maximum concentrations of arsenic (a pending COC) for surface water remained consistent in each respective monitored pond (Pond 4, 6, 7, 8, 10 – Japanese Spring), spring or canal (Jones Spring, Kessler Spring, No Name Spring, and Smelter Return Canal). Surface water average maximum arsenic concentrations remained below the DWQ’s Class 3D water quality limit for arsenic (150 µg/L, microgram per liter) in Ponds 8 (60.67 µg/L), 10 – Japanese Springs (10.33 µg/L), Jones
Spring (5.67 µg/L), Kessler Spring (9.00 µg/L), No Name Spring (17.67 µ/L), and Smelter Return Canal (46.67 µg/L). Only a limited number of samples have been reported to date. Based on the limited dataset, three Ponds – 4 (189.00 µg/L), 6 (1153.33 µg/L), and 7 (266.33 µg/L) were determined to have average maximum concentrations
of arsenic in excess of the DWQ’s Class 3D water quality limit for arsenic.

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As noted in Section II, the need for remedial action is premised on selenium concentrations in the macroinvertebrate tissue samples collected from the monitored ponds, springs and canals. Macroinvertebrate
tissue samples were collected in the same locations as the water and sediment samples were collected. Selenium concentrations in the macroinvertebrate tissue samples are compared against the current selenium threshold limits of <5.00 mg/Kg (if consistently below 5.00 mg/Kg, monitoring can cease), >5.00 mg/Kg (if 5 mg/Kg or higher, monitoring continues), >10.00 mg/Kg (monitoring frequency increases and source inputs are evaluated). Monitoring continued during this five-year review period. Average maximum selenium macroinvertebrate tissue concentrations per pond (4 – 27.6 mg/Kg, 6 – 12.31 mg/Kg, 7 – 12.80 mg/Kg, 8 – 14.83 mg/Kg, 10 – 22.97 mg/Kg), spring (Jones – 15.30 mg/Kg, Kessler – 24.75 mg/Kg) and canal (Smelter Return – 69.27 mg/Kg) were above the 10 mg/kg macroinvertebrate tissue selenium concentration limit consistently during the five-year review period. Similar to the surface water arsenic data, the data sets were limited in terms of the number of samples reported. RTK continued monitoring but also assessed abatement strategies for the increased arsenic and
selenium concentrations. However, during the Five-Year Review period, RTK did not propose further remedial action to address the increasing concentrations of selenium in the macroinvertebrate tissue samples.
Reviewing the existing data for water, sediment and macroinvertebrate tissue concentrations for arsenic, selenium and other metals, and comparing from year to year, the concentrations in each media sampled are quite variable. To date this has hindered the development of a trophic transfer ratio for each pond, spring and canal comprising
the NZW. The September 2002 ROD selected remedy requires the development of trophic transfer ratios. The annual data variability has hindered an understanding of the potential for impacts from selenium in the various media of concern that the resident and migratory avian community encounter during their foraging activity. In 2008 (and repeated in 2014, 2017, 2020, 2022 and 2023), RTK voluntarily began monitoring bird eggs to assess selenium concentrations for three feeding guilds (shorebirds, waterfowl and passerines) and in 2022 added a fourth feeding guild (piscivore). These four feeding guilds are comprised of the resident and migratory avian community using the NZW. Continued bird egg monitoring is important since bird eggs are currently recognized as the end point of concern to evaluate potential selenium exposure threats to the resident and migratory avian community. The EPA is evaluating options to modify the OU22 selected remedy to include bird egg monitoring and threshold limits for potential response action.
As noted, RTK has been monitoring bird eggs in the NZWs since 2008 under work plan amendments reviewed
and approved by the EPA and DERR. Under the work plan amendments, RTK has compared bird egg selenium
concentrations against a 12.5 mg/kg dry weight whole egg selenium benchmark. RTK derived the benchmark from the DWQ protection standard for the Gilbert Bay area of the Great Salt Lake, which is intended to protect avian receptors that use that saline habitat. The September 2002 ROD does not include a bird egg threshold limit for selenium. It is important to note, that the geomean calculation for each guild is affected by the total number of eggs
collected for each feeding guild. The EPA’s Biological Technical Advisory Group (BTAG) has advocated that 12 eggs is the minimum number of eggs that should be collected to calculate a statistically representative geomean for each feeding guild. With the statistical representativeness of the bird egg data in question (because the 12 egg
minimum per feeding guild – per year has not been met), there are questions about the statistical significance of the linear regression trends. The selenium concentrations detected to date in the bird eggs collected indicate that there is a selenium source to the NZWs and the exposure assumptions, toxicity data, cleanup levels, and remedial
action objectives need to be reevaluated. Please refer to Section IV – Data Evaluation for further information. Evaluation of bird use survey data collected since 2008 has documented species diversity issues, including annual changes in the predominant species using the wetland. Based on an increase in the number of species in this feeding guild, it is warranted to include a fourth feeding guild (piscivores) for bird egg sampling and analysis. Bird egg collection to date for the Shorebirds has consistently collected enough eggs (n=12.33 versus the required n=12) to support a geomean evaluation. Though concentrations have remained below 12.5 mg/Kg, there is an

18
increasing trend for selenium concentrations when the annual geomean concentrations are evaluated using a linear regression.
Bird egg collection to date for the Waterfowl has not collected enough eggs (n=6.17 vs n=12) consistently to support a geomean evaluation. However, the eggs which have been collected have demonstrated geomean concentrations above the DWQ 12.5 mg/Kg bird egg selenium standard. The limited geomean data collected to date has demonstrated a downward trend, but again, the limited number of eggs collected raises questions about the statistical representativeness of the data. Bird egg collection to date for the Passerine feeding guild has not collected enough eggs (n=4.33 vs n=12) consistently to support a geomean evaluation. One annual geomean concentration was determined to exceed the DWQ 12.5 mg/Kg bird egg selenium standard. The limited geomean data collected to date has demonstrated a downward trend. However, the number of eggs collected raises questions about the statistical representativeness
of the data. As for the newest feeding guild, piscivores, only two years’ worth of egg collection has taken place so far.
Current egg collection totals have been below the necessary egg collection total (n=7.5 vs n=12) necessary to support a geomean evaluation. Geomean concentrations have remained below the pending threshold limits, but with only two years’ worth of limited (and questionable statistical representativeness) data no concentration trend
has been assessed. The bird egg selenium concentration data suggests that there is the potential for selenium exposure to the resident and migratory avian community using the NZW. Further data, that is statistically representative, is required to further assess the exposure potential. For OU23, groundwater monitoring data was collected during the 2010 to 2012 RI Update (reported in 2013). This effort was to advance the understanding of why the aquifer and the arsenic and selenium-impacted groundwater were not responding to the selected MNA remedy, as predicted in the 2000 RI. Since the RI Update, RTK has continued to monitor the groundwater in OU23 as part of their implementation of groundwater monitoring in response to the site-wide Groundwater Characterization and Monitoring Plan (GCMP), last updated
in 2016 under the authority of the DWQ GWPP. In 2018, RTK updated the isoconcentration projections for the arsenic and selenium plumes underlying the Smelter and Refinery, which comprise the areas of impacts in OU23. The smelter selenium plume had extended north to SH-201 where it was discharging in a series of seeps and springs. The smelter arsenic plume was contained underneath the smelter south of SH-201. In 2018, the arsenic plume at the refinery was still underlying the facility while the selenium plume maintained its extended reach underlying the southern portion of the NZW of OU22. Arsenic mobility is a function of the redox conditions in
the aquifer; if the aquifer is in an oxidated state (and arsenic is oxidated, i.e. arsenate), arsenic is less mobile. Interesting to note, selenium mobility is equally a function of the redox conditions but in the opposite direction of the redox curve. As an aquifer converts to a reduced state, selenium is mobilized. The refinery arsenic and selenium plumes continue to be the focus of the ongoing evaluation and revision of the 2020 FFS for OU23, in part, due to an incomplete evaluation of upgradient source material and the deeper groundwater flow path underlying the NZWs. RTK recently provided a figure projecting arsenic concentrations in groundwater underlying and emanating from the smelter facility, past SH-201 and underlying a large portion of the NZW. The aquifer redox conditions, arsenic plume boundaries, and determination of whether the arsenic is background or anthropogenic raises questions regarding the accuracy of the conceptual site model and information gathered in the 2000 RIFS.
Site Inspection
The purpose of the site inspection is to observe the current conditions of the property and to assess remedy elements. The following is a summary of the issues identified during the inspection. The site inspections took place from May 2023 to February 2024. The site inspections were performed by Mazie Cox, UDEQ Project Manager, joined by RTK personnel, Teresa Cockayne, Kate Ruebelmann, Chad VonHatten, and Bryn Howell.
Site inspection photos are provided in Appendix D.

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OU8: Waste Water Treatment Plant (WWTP) and Sludge Ponds
The site inspection consisted of observing the WWTP and Sludge Ponds B, C and C+ (or C Extension), and determining if the covers were stable. The footprints of the WWTP and Sludge Ponds B, C and C+ are owned by RTK. The footprints have seen very little disturbance since buildings and other infrastructure were demolished, cleaned up, and reclaimed. The soils are stable and not subject to erosion. No dust was observed during the inspection. Soil mobilization is not anticipated because of successful vegetation and ongoing management of the area. Sludge Ponds A and D have been converted into the surrounding wetland habitat of the OU22 NZW. Sludge Pond B appeared stable and well-vegetated with grasses and forbs. Sludge Ponds C and C+ appeared to be stable and well-vegetated. During the inspection, the sides of a reclaimed ingress/egress road were showing signs of vegetation cover established across the whole footprint. Two-thirds of the WWTP footprint is vegetated with
grasses and native forbs, while the western one-third remains barren of vegetation and is used as a staging area. OU13: Smelter and Acid Plants
OU13 is owned by RTK and supports the smelting process facilities for the copper concentrate from the Bingham Canyon Mine. The facilities on site include a third-generation Smelter and support facilities including an acid tank storage farm and loading station, cooling and smokestack towers, slag pot cooling staging area and a slag mill,
various rail spurs, and water reservoirs. A portion of the facility is leased to Praxair for compressed gas production. The site also contains material staging pads. The northern boundary of the site has a series of seeps located between the western and eastern extent of the OU13 boundary. The site inspection consisted of observing the Smelter facility, the integrity of capped facilities, and the surrounding land. The overall Smelter footprint appeared to be in good condition. Transport corridors were covered with either asphalt or concrete. The dirt roads behind the Smelter were graded and did not show any signs of recent releases. Previously removed and reclaimed facilities, which have asphalt covers, were stable. The Slag Pot Cooling Area and Mill are operational areas. The cooling area is covered with asphalt. Slag appeared along roadways and at both the northern and eastern boundaries of the cooling area. The footprints appeared to be in good shape. The West Process Water Reservoir and East Process Water Reservoir were full of water and below the height of their embankments. Visible sections of liners appeared to be intact.
The surface soils along the south side of State Highway (SH)-201 appeared to be stable. Past projects by UDOT and sampling by RTK have found material with elevated arsenic concentrations located along the south side of SH-201 in front of the Smelter (which was removed to the established site-specific industrial land use action
levels specified under the work plan). The Black Rock Tailings Pond is covered with soil and partially vegetated (side slopes are more vegetated than the top surface). Some opportunistic sampling to determine the nature and extent of soil/solid mine waste has been performed to assist with informing closure requirements, but a full characterization to determine the nature and extent of solid mine waste has yet to be completed. At the Acid Tank Farm Loading Station, DWQ reported the groundwater extraction system is functioning as required and there are no issues with the implementation of ongoing corrective action (see Appendix E). The surface area around the Praxair facility and directly over the groundwater extraction system was observed and found to be covered with asphalt.
Established monofills at the smelter, permitted by the Salt Lake County Health Department, have been operated in compliance with the permit limitations since 2019 (see Appendix E).

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OU14: Refinery OU14 is owned by RTK and supports the refining processes for RTK’s final copper product as well as the
refining operations for various precious metals. The facilities located on site include the Refinery electrolytic tank house, copper cathode production warehouse, precious metals extraction facility, and various rail spurs. The site also contains the footprints of two capped historic operational areas, the Electrolytic Pond (EP Pond), and the Old Precious Metals building. The site inspection consisted of walking around the Refinery complex and observing areas where infrastructure has been removed. Rail services support the operations and transport of packaged products. Generally, the overall facility appeared to be in good condition. The Refinery complex is covered with asphalt and/or covered by the foundations of structures. Stormwater collects around the facility boundary. The facility structures on site appeared in good condition.
On March 18, 2020, a 5.7 magnitude earthquake hit with an epicenter 3.7 miles north-northeast of Magna, near the RTK Tailings Complex. The earthquake caused damage to the Refinery complex, including the release of process fluids at the refinery storage tank area. Specifically, the storage tank for hydrochloric acid at the Refinery
experienced a leak near the flange connection of a distribution pipe. Reportedly, the release of hydrochloric acid was captured by the primary containment system. There is the potential that some of the release fluid could have impacted localized soils underlying the surrounding asphalt and concrete surface covers. The release took place in
an area that is already monitored due to an existing arsenic and selenium plume underlying the Refinery (OU23). Remaining damages to the Refinery complex are mostly cosmetic damages. Several windows were noted as missing from areas of the tank house. RTK noted that repairs to the refinery have been occurring since the 2020 earthquake. RTK was not aware of any further structural damage to the refinery complex due to the earthquake. As part of this inspection, a walk-through of a portion of the tank house basement was conducted. A specialty resin is applied to the tank house subfloor and, upon inspection, was determined to be in fair condition. Evidence of spills from the electrolytic tanks were observed on the subfloor (see Photos 12-14). Additionally, a large crack was observed in the floor (Photo 14). According to RTK, sections of the subfloor have had maintenance updates over the past two years; however, at this time it is unclear which areas of the subflooring have been updated, and the total percentage of the basement flooring that has been refinished with new resin is unknown. While there is
no current evidence of exposure risk to the environment at this time, monitoring of the tank house subfloor should continue and be evaluated again during the next five-year review period. The engineered cap constructed over the footprint of the historic precious metals plant was intact and well-vegetated, and no intrusions were observed. The 2014 FYR noted tire tracks that ran over the top of the cap. No evidence of tire tracks or animal burrowing was observed during this inspection. The cap is enclosed by chain-
link fencing on the south, west and east elevations (adjacent to active operations). Access to the cap area is significantly limited. The engineered cap constructed over the footprint of the historic electrolytic pond was intact, well-vegetated and stable. An O&M plan is needed to require maintenance for covers and caps, as one is currently not available. All rail spurs around the Refinery and the rail yard appeared stable. Rail bedding material (historic smelter slag) appeared stable on the corridor, aged but not migrating. OU15: Mills and Tailings Pond The historic and active operations in OU15 were and are implemented by RTK and its predecessors, and the footprints are currently owned by RTK. OU15 includes the historic and active footprints of the South Tailings Impoundment, North Tailings Impoundment, Arthur Stepback Repository, Diving Board Tailings Pond, Bonneville Crushing and Grinding facility, Magna Floatation Mill, Arthur Mill, RTK Power Plant, and Magna Reservoir. Other historic support facility footprints, various pipelines, rail spurs/sidings, and wetland mitigation
areas are located within the boundaries of OU15. The site inspection consisted of driving around the facilities and inspecting surface soils, observing excavation activities, inspecting covers, and observing facilities undergoing demolition. Portions of OU15 are used for the disposal of solid mine waste, management of mining-influenced

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water, and power production. The reclaimed mill footprints are used as open space and buffer to active rail and power generation operations.
Established soil covers remain intact and stable, and re-vegetation efforts of previously removed sites have been intermittently successful. No soils were observed migrating off-site and no dust was observed. The reclaimed surface of the Arthur Mill appeared stable and well-vegetated. No run-off channels or rills were observed. Portions of the facility, though buried, are quite noticeable (for example, the large buried tailings thickener located along the southwest boundary of the mill footprint). These areas potentially have solid mine waste and soils with metals buried at depth (minimal sampling post-demolition was performed in the 1990s). The reclaimed surfaces of the Bonneville Crusher & Grinding footprint appeared stable and no erosion, channels, or rills were observed on hillsides. Voluntary re-vegetation has increased but is still not a complete cover due to
high cobble material with low topsoil content. The Bonneville facility footprint is located at a higher elevation, which is also suspected to be acting in part to hinder vegetation efforts.
The surface soils around the Magna Mill footprint were stable. A fairly cobbled soil was used for reclamation efforts and the re-vegetation effort has been partially successful. Closer to the frontage road, near the northern portion of the facility, the footprint slopes at a steeper angle, and vegetative success is more limited. The lack of
topsoil and high cobble content of the material is suspected to be the reason for the limited vegetation. Along the west boundary of the Magna Mill footprint, the vegetated, reclaimed arroyo cut by a spill circa 2008-09 was still visible. The soils are stable, and as noted, the relaxed channel is well-vegetated. The Magna Process Water Pond embankments were well armored with rip-rap. No evidence of spills or releases was observed. The Utah Power Plant (UPP) became a non-operational facility in 2018. Demolition of the UPP began in 2020. At the time of the site inspection, the UPP building was standing, and the exterior stacks and towers had been removed. The demolition of the power plant is occurring under the state authority, Utah Division of Air Quality (DAQ), under an approved demolition plan. After the demolition of the building has been completed and pursuant
to the selected remedy for OU15, further CERCLA response work must be initiated. Post demolition remedial action will include characterizing the overall footprint, assessing potential future land use, and implementing soil management to ensure soils on site comply with the intended land use. The remedial action may lead to soils above the site-wide unrestricted land use action level being left in place, which would require the facility footprint to be subject to the requirements listed in the 2019 Site Wide WLIP. The future remedial action at the UPP should be evaluated during the next five-year review period.
The South Tailings Impoundment was found to be stable, with well-vegetated areas. A few deciduous trees have been planted; otherwise, there are some scrub oak and other brush species across the top surface of the reclaimed impoundment. The southern extent of the South Tailings Impoundment (STI) was observed to be barren, with limited vegetation. RTK reported that a pilot study is occurring on the southern extent of the STI to determine which vegetation can successfully grow. Due to the acidic nature of the soils present at the STI, re-vegetating has proven to be difficult. As the study continues, RTK will attempt to re-vegetate the southern extent of the STI. Other than established roadways along the top surfaces and embankments of the impoundment, there was no other evidence of vehicular activity along the reclaimed surfaces. There was no dust observed during the inspection. Slag from the Copperton High and Low rail lines was disposed of at the Tailings Landfill. The Tailings Landfill appeared to be partially vegetated from voluntary seeding. Parallel to the Tailings Landfill containing the rail bed
slag, RTK was installing a pipeline resulting in the management of tailings impoundment material within the corridor of the pipe. The excavated tailings were stable in the staging areas, showing no signs of erosion or dust generation. The North Tailings Impoundment is the active tailings disposal facility and the outer embankments appeared stable. No dust was observed during the inspection. Observations of the interior pond on the North Tailings
Impoundment were made from the tailings decant barge. The southern embankment (north portion of the South

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Tailings Impoundment) was observed to be stable with no erosional gullies observed. California gulls were observed sitting on a buoy boom attached to the decant barge. Plans for a future expansion of the North Tailings
Impoundment, with the addition of a southeast tailings impoundment, are currently proposed by RTK. Approval of a future expansion is not part of an existing CERCLA remedy. The U.S. Army Corp of Engineers retains regulatory oversight under its Section 404 Authority under the Clean Air Act. The Agencies requested a copy of the Environmental Impact Statement (ESI) once finalized and will receive periodic updates from the lead permitting program (DWQ GWPP) to ensure protective controls are in place and remain effective for addressing the potential for future releases to groundwater. Additionally, DERR is completing the pending State Permit Gap Assessment to assess the potential need for further CERCLA response and oversight of these areas. As reported by the DWQ UPDES program, RTK has had several violations of their UPDES permit over the past five years. As noted in the compliance review (Appendix E) RTK has violated its permit between 2019 and 2024; however, RTK maintained overall good standing. RTK regularly maintains contact and works with DWQ to
resolve outstanding violations and updates DWQ of any upcoming violations. The most recent formal enforcement action between DWQ and RTK was a warning letter issued in 2018 (outside of this five-year review period). The permitting authorities' compliance motoring information for the past five years is included in
Appendix E. As reported by the DWQ GWPP, the Tailings Impoundment permit (#UGW350011) has been in renewal for
approximately two years. The renewal package was submitted in time for the administrative extension of the permit, allowing for the longer renewal period. The current compliance status for the Tailings Impoundment is mixed. Most of the wells are in compliance with their current compliance limits. Four wells are currently out of compliance and are as follows:
• NEL532B has exceeded the TDS limit for the well since July of 2021 with a brief drop back into
compliance in the 4th quarter of 2022 before continuing to be out of compliance as of April 2024.
• NET1386B has exceeded its compliance limit for sulfate since January 2021.
• NEL1382C has exceeded the compliance limit for pH since January 2021 with a brief period of
compliance for the 2nd and 3rd quarters of 2023 before entering out of compliance status again as of April
2024
• NET646A has exceeded the arsenic compliance limit since June 2021.
The DWQ reported that RTK has submitted a Source Area Assessment for the exceedances in the above-noted compliance wells around the Tailings Impoundment. The report is currently under review by the DWQ. The DWQ also noted some possible concerns with the integrity of the impoundment. Historically, the Bonneville clay drainage blanket located beneath the Tailings Impoundment has been considered a “natural liner” and has prevented tailings water from entering the shallow groundwater aquifer. The DWQ reported that currently available data denotes a 20-foot settlement of the drainage blanket beneath the Tailings Impoundment complex.
There is information to suggest that the interaction between the base of the Tailings Impoundment and the surrounding groundwater may be different from our current understanding. There is the potential for impacts to areas of OU22 that surround the impoundment and to OU23 west of the Tailings Impoundment. The integrity of
the Tailings Impoundment should be reviewed during the next Five-Year Review Period. As reported by the SLCoHD, RTK has maintained compliance with its permit limits for the tailings landfills for
on-site solid waste disposal (see Appendix E). The Arthur Step-back Repository (ASR) is the active facility that receives contaminated soils and solid mine waste that results from the CERCLA response actions at the Site. CERCLA response actions to remove soils and solid mine waste and dispose of such in the ASR were implemented previously pursuant to the 1996 Administrative Order on Consent for North Facilities Soils, the 1996 AOC work plan and, more recently, pursuant to the pending Site Wide OSMP. During the inspection, no material was being placed into the ASR. The ASR is permanently capped with a high-density polyethylene liner and soil cover on its east half. The soil cover is well-

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vegetated with grasses and forbs that have shallow roots. The west portion of the ASR is temporarily capped with a high-density polyethylene liner. Stormwater was observed ponded on the west end of the ASR, which is allowed
under the 2018 ASR O&M Plan. DWQ’s GWPP reported that though the facility is not specifically permitted under the tailings impoundment permit, monitoring of wells downgradient of the facility is in compliance with established compliance limits (see Appendix E). The Diving Board Tailings area was not in use at the time of the inspection. The surfaces of the embankments and the interior slopes and base of the impoundment were well-vegetated. No signs of spills or releases were observed around the facility. The facility is operated by RTK in compliance with the tailings impoundment groundwater protection permit (GWPP) (see Appendix E). Its current use is to collect contact stormwater from the former North Concentrator and the south side of the South Tailings Impoundment and acts as a capture area for the Magna Reservoir. DWQ’s GWPP notes that underlying shallow groundwater is impacted by elevated arsenic concentrations above Utah’s groundwater quality standard. Monitoring has demonstrated seasonal cycling of
concentrations above the groundwater standard. Upward hydraulic gradients in the area protect the underlying principal aquifer. A source assessment determined minimal risk to human health based on current conditions. DWQ has the lead under the permit to continue to oversee the monitoring of this facility.
OU19: Smelter Fallout The canyons comprising this OU (Little Valley, Kessler, and Blackrock) are owned by RTK. Portions of these
canyons support surface water control features (check dams, sedimentation basins) as well as the footprints of historic and current mining support facilities including smokestacks, process water reservoirs and tanks, permitted monofills, and rail spurs/sidings. The canyons are managed by RTK as open space but also for support of localized wildlife. The site inspection consisted of driving and walking into the canyons located downwind of the smelter (OU13) and refinery (OU14). Little Valley is well-vegetated and the surface soils are stable. The sedimentation/flood control dams and step terraces located in Little Valley were in good condition. Wildlife was observed on two occasions in the upper portion of Little Valley (deer, elk, coyotes). Kessler Canyon is well-vegetated and soils are stable. Steeper side slopes in the upper reaches of the canyon are less vegetated, and there were signs of erosion. The flood control dams were stable, and down-gradient slopes were well-vegetated with grasses and forbs. No evidence of erosion was observed along the canyon floor. Black Rock Canyon is well-vegetated along the canyon floor, and lower side slopes are stable. Steeper side slopes
are relatively void of vegetation, potentially due to a lack of soil or because of the slope grades. Side slopes in Black Rock are rocky with exposed bedrock surfaces. No running water was observed on the surface in any of the three canyons. The lower portion of Black Rock Canyon is currently under active gravel mining operations and is
identified as the “Black Rock Sand & Gravel” pit and is operated by Geneva Rock. Geneva Rock has leased a large majority of Black Rock Canyon; however, only 12 acres are currently cleared for mining with extensions planned in the future. The gravel pit was inspected in February 2024. The gravel pit operations generally cease during the winter season. Beginning under an approved Impacted Soils Work Plan dated May 2022, the 12-acre area was characterized and soils with elevated lead and arsenic were identified. Soil with elevated concentrations of lead (500 mg/kg) and arsenic (50 mg/kg) was identified between 0 inches and 6 inches below the surface. Initially, the top 6 inches of soil was clean-cut and removed from the 12-acre area. After removal of the top 6 inches of soil, visual “dark patches” could be seen on the surface and further contaminated soil was identified using X-ray fluorescence (XRF). An additional cut of soil was taken, averaging 12 inches in total removed and ranged from around 6 to 18 inches. Soils with elevated lead (>500 mg/kg) and arsenic (>50 mg/kg) levels were removed and placed in a repository area which is located west of the active mining area. Post-removal soil samples were then collected from the exposed surface within the 12-acre boundary, and concentrations were all below the site wide
unrestricted land use action levels or KUALs (2022 Impacted Soils Work Plan). A total of 7 post-removal samples were collected. Each sample consisted of 5 aliquots with aliquots spaced approximately 150 feet apart. Samples were analyzed for Total Arsenic and Total Lead concentrations. Laboratory analysis resulted in lead
levels that ranged from 8.62 mg/kg to 89.0 mg/kg and arsenic levels from 11.2 mg/kg to 46.7 mg/kg.

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The repository was re-vegetated with seeds that do not uptake selenium in November 2022. Signage is posted
adjacent to the repository. The active mining area had established boundaries identified through signage and fencing. A representative of Geneva Rock notified DERR at the time of the site inspection that vehicles and associated gravel mining equipment are restricted from accessing the areas outside of the 12-acre portion of land to prevent the tracking of potentially contaminated soils outside the boundaries of Black Rock Canyon. There is no evidence that elevated soils have left Black Rock Canyon, and the associated repository appears to be generally well-vegetated. Some areas of soil and gravel were noted in the repository. The repository is located behind locked fencing and is only accessible through RTK-owned roads. OU22: Great Salt Lake, Shoreline Wetlands, and OU23 North End Groundwater Portions of OU22 and OU23 are on, encompassed by, or underlying property owned by RTK. OU22 includes wetlands around the tailings impoundment and north of the smelter and refinery (i.e. North Zone Wetland –
NZW) in addition to a portion of the Great Salt Lake and its southern shoreline. Of significant interest is the NZWs, an approximately 2000-acre wetland situated between Interstate 80, State Highway 201 and State Highway 202. The NZWs include a series of artesian springs (Hansen, Japanese, Kessler, No-Name, Jones (Jones
Canal), Adamson, and Spitz) along with surface ponds 2, 4, 5, 6, 7 and 8. The site inspection included general observations of the NZW habitat, including qualitative observations on water levels and bird use. In general, water levels were observed to be elevated in 2023. In the Spring of 2023 Northern Utah received higher than
normal precipitation and runoff from snow melt. This lead to higher water levels measured in the NZW ponds. Nesting populations change from year to year and depend on many factors including water levels and yearly climatic changes. The artesian springs, which provide surface water to the NZW habitat, were inspected in June 2023. The springs discharge groundwater (OU23) from the underlying impacted aquifer into the surface waters of the NZWs. Management of the groundwater being discharged is part of the selected remedy for OU23; however, it also continues to daylight and influence the NZWs habitat. Water levels in the springs begin to reduce in the June/July timeframe and can be variable. Japanese Springs and Hansen Springs, located in the western and central quadrants of the NZW, were also inspected. Both were producing water, which generally flows north. Japanese Springs is located on the south side of State Highway 201, west and north of the Slag Mill at the smelter; Hansen Springs is
a series of springs and seeps located south of the western third of Pond 8. The surface area of Hansen Springs was covered with slag in the mid-2000s to act as a drainage blanket and to control surface ponding of the spring and seep waters. The slag cover material was observed to still be intact with limited expression and ponding of
daylighting groundwater. The embankments of the ponds at Japanese Springs were well vegetated, whereas the Hansen Springs area was not well vegetated due to the lack of suitable soils available for growth. Standing water was observed at Hansen Springs. Little to no bird usage was observed at the time of the inspection.
No Name Springs was observed to be well-vegetated, and there was no observed bird use. Given the elevated water level at the time of the inspection, a high flow of water was observed at No Name Springs. Jones Springs (and Canal), located near OU8 along the west embankment of South Tailings Impoundment, was observed to be flowing. Water was directed to RTK's Pump Station #4 to direct the water into the process water circuit (a requirement of the current OU23 selected remedy). The ponded areas adjacent to the process water circuit were observed to be well-vegetated. The water levels were observed to be high. The southernmost pond in the NZWs, Pond 2, is between State Highway 201 and the Smelter Return Canal, just north and west of the intersection of State Highway 201 and 202. Water flowing from Kessler Springs can flow into Pond 2 which is predominantly a ditch surrounded by a thick cover of phragmites. RTK currently collects
groundwater daylighting at Kessler Springs, sending a large portion of the flow to their water process circuit via Pump Station #4. Approximately 250 gallons per minute is diverted to RTK's biotreatment plant, which reduces selenium concentrations by bio reduction, where selenite is reduced to selenate. The biotreatment plant is a pilot
study. Pond 2 did not have any observed water in its alignment next to Kessler Springs. Pond 2 was observed to be well-vegetated.

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Ponds 4 (a series of adjacent small ponds, 4A, 4B and 4C) and 5 are located in the southeast quadrant of the North Zone Wetland. Pond 4 was previously drained in 2009 and the shoreline and open water habitat was reduced by
conversion to upland and introduction of phragmites to fill in the shoreline. Pond 5 was completely drained and filled in to prevent surface water ponding in 2009; thus, it was converted to an upland habitat. The OU22 North Zone Wetlands 2023 Monitoring Report – Draft (OU22 NZW ‘23 MR), submitted by RTK notes that bird use at Site 4A and Site 4C was significantly lower in 2023 versus 2022, although water levels appeared very similar to 2022. According to surveys, bird usage at Sites 4A and 4C in 2023 was half that observed in 2022 but still greater than usage in the seasons before 2020. A total of 7 species were observed using Site 4C in 2023, including many of the same species that were identified at the Site in 2022. Ponds 6 and 7 are located in the east central quadrant of the North Zone Wetland habitat located near the existing slag rail buttress. Pond 6 consists of four adjacent ponds (6A, 6B, 6C and 6D). Pond 6 tends to be ephemeral, and surface water levels tend to reduce as summer progresses. Pond 7 consists of two ponds (7A and 7B) which tend
to dry up as the summer season progresses. In 2009 both Pond 6 and 7 had their drainage systems configured to facilitate drainage of surface water to Pond 8. The surrounding surface and shorelines of Ponds 6 and 7 were well-vegetated with various wetland grasses, including Phragmites. The OU22 NZW ‘23 MR notes a slight decrease in
bird use at Site 6D from 2022 to 2023. With 12 species observed throughout the season versus 15 species surveyed in 2022. At Site 6D, bird use appeared higher throughout May, with slightly lower use beginning in mid-June. Water levels at Site 6D were relatively high near the beginning of the season, beginning to dry out in mid-
July. Pond 8 is the terminal basin for the NZWs. It is in the north central quadrant of the habitat, parallel to Interstate 80. The UPDES Discharge Outfall #004 is located in the northwestern quadrant of Pond 8 with a flow control gate managed by RTK. Pond 8 represents the largest surface water body in the North Zone Wetlands and water levels were generally observed to be elevated compared to previous years. Pond 8 includes shoreline and open water habitat frequented by many of the observed avian species using the overall NZWs, including American Avocets, Black-necked Stilts, American Coots, Mallards, and both Red-winged and Yellow-headed Blackbirds. Dozens of birds were observed using the small islands located throughout Pond 8. The OU22 NZW ‘23 MR notes that Pond 8 had the most diverse habitat in the North Zone Wetlands, as well as the most significant number of birds using it (89% of birds observed). Three species, double-crested cormorants, Canada geese, and California
gulls, were observed in large numbers during each survey at Pond 8, and they dominated the bird counts. Nesting habitat for Cormorants and gulls is abundant at Site 8D, where the birds form large nesting colonies on rock islands. Canada geese nest near the pond, and after their goslings hatch, they bring them to the pond to forage and loaf. However, gulls were observed regularly flying toward the southeast, where they were likely doing much of their foraging, and cormorants were observed flying to and from the NZW during each survey, possibly foraging in other wetlands.
Based on surveys (OU22 NZW ’23 MR), bird usage of Pond 7/8 in 2023 was roughly half that in 2022 but comparable to numbers surveyed before 2022. The number of individuals using the area was highest in early May and mid-June, tapering off later in July. This might suggest breeding occurred later in the season, and bird use decreased after young fledged from nests. Higher water levels were observed across the Site, particularly at Pond 8. Pond 7/8 had an abundance of shallow pools throughout the season, with higher numbers of shorebirds and waterfowl. No development activity was observed at the south shoreline of the Great Salt Lake. The shoreline supports local recreation by the public interested in seeing the Great Salt Lake. There is a commercial business venture that uses the Saltair Pavilion (located just north of I-80 and SH-202) for concerts and gatherings. In addition, there is also
the Great Salt Lake Marina (located west of the Salt Air Pavilion) which supports local boating activity on the lake as well as a Utah Parks installation. The Great Salt Lake Marina was landlocked at the time of the Site Inspection. Limited use of the area by the public was observed during the inspection. As noted in the September 2002 ROD the shoreline is generally supportive of recreational use by the public. An historic causeway is located on the shoreline about ¼ mile northeast of the Saltair Pavilion. The 1960s-era
causeway is approximately 1 mile long and extends from the Interstate-80 frontage road and terminates near the

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Great Salt Lake waterline (depending on the elevation of the Great Salt Lake). The causeway is constructed of copper tailings and has subsequently eroded over the years by wave action in the Great Salt Lake. The copper
tailings used to construct the dike can be detected approximately 2 to 6 inches below the lake bed sands along the causeway alignment. The noted wave action over time disbursed the copper tailings unevenly. No changes in use or recent intrusions into the material located in the causeway were observed during the site inspection. Little to no vegetative cover was observed on the causeway. Salt-tolerant vegetation was observed on approximately 1/3 of the causeway that is closer to the frontage road. Vegetation ceases for the remaining approximately 2/3 of the causeway as the causeway gets closer to the Great Salt Lake. OU23 consists of multiple arsenic and selenium plumes in groundwater underlying the refinery (OU14) and smelter (OU13) facilities. The arsenic and selenium in the groundwater is elevated above potentially relevant groundwater and surface water standards of the DWQ (refer to the site background section). The impacted groundwater is only visible at springs located along State Highway 201 and in the NZWs habitat in OU22,
immediately north of the plumes (refer to the site inspection observations discussed in OU22). No notable standing water was observed during the inspections of OU13, OU14 and OU15.
The groundwater at OU23 is only visible when it surfaces at the various artesian springs located north of the Smelter (OU13) and Refinery (OU14) complexes, and via seeps in the NZWs (e.g. Hansen Springs). During the inspection, Japanese Springs and Hansen Springs were observed. Both were producing water, which was flowing
north. The embankments of the ponds forming Japanese Springs were well vegetated, whereas the Hansen Springs area was not well vegetated due to the lack of suitable soils for growth (the remedy to prevent water production was the placement of non-leachable slag over the area). No Name Springs in the east portion of OU13, just south of SH-201, was observed to be well vegetated and did not have any observed bird use. Water flow rates were observed to be high since the inspection took place during May and the snow melt/runoff season. Water flow at Kessler Spring was being collected and diverted in part to RTK’s pilot selenium bio-treatment plant. RTK’s operational testing has observed selenium reduction efficiencies of 97%, reducing selenite to elemental selenium through microbial digestion. The remaining water collected at Kessler Springs was being delivered to RTK’s process water circuit. Pond 2, which is a discharge channel from Kessler Springs, did not have any observed water in its alignment. Jones Springs, near OU8, continues to be directed into RTK’s process water circuit, piped to Pump Station #4 located on the reclaimed footprint of the waste water treatment plant facility located in OU8. V. TECHNICAL ASSESSMENT
OU8 Waste Water Treatment Plant and Sludge Ponds QUESTION A: Is the remedy functioning as intended by the decision documents? The remedy is functioning as intended by the September 2002 ROD. No new contaminants of concern or contaminant sources have been identified since the September 2002 ROD and the commencement of the RA. Pursuant to the 2017 ESD, RTK has the option to clean up soils on its property (pursuant to the pending Site Wide OSMP) to the current applicable land use action level given the current land use or clean up soils to the site wide unrestricted land use action levels which includes lead (at 500 mg/kg). Cleaning soils to the site wide unrestricted land use action level for lead means the land can be used without restriction, including potential residential land use. The September 2002 ROD also noted that during the extraction of sand and gravel (borrow material) for off-site shipment and use, such extracted material has to comply with the site wide unrestricted land use action levels
including lead (500 mg/kg). This allowance could result in the use of extracted material during residential and recreational (i.e. playground) redevelopment projects.
Further action by RTK, EPA, and UDEQ is necessary to support the long-term protectiveness remedy (see Question C).
QUESTION B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives (RAOs) used at the time of the remedy selection still valid?

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The current soil cleanup levels selected in the September 2002 ROD and 2017 ESD were based on the estimated risks defined in the December 20, 1999 Final Preliminary Remediation Goals Report for Addressing Risks to
Human Health from Exposures to Chemicals in Kennecott Soils (December 1999 PRG). There have been changes to the exposure assumptions and toxicity information for lead since the December 1999 PRG document was issued. In addition the site wide unrestricted land use action level for lead (500 mg/kg) is above the screening values published in EPA’s January 17, 2024 guidance. On January 17, 2024, the EPA Office of Land and Emergency Management (OLEM) released the “Updated Residential Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities” (2024 Updated Soil Lead Guidance), which updates the residential soil lead screening level (RSL) and removal management level (RML) for the CERCLA and RCRA programs and provides additional guidance for setting residential lead preliminary remediation goals (PRGs) and cleanup levels. The 2024 Updated Soil Lead Guidance recommends that regions use the most current version of the Integrated Exposure Uptake Biokinetic model, with 5 µg/dL as the
95th percentile target blood lead level and site-specific environmental data (e.g., lead concentrations in various media and bioavailability) to develop PRGs and cleanup levels for residential land use. If an additional source of lead (e.g., lead water service lines, lead-based paint, non-attainment areas where the lead concentrations exceed
NAAQS) is identified, 2024 Updated Soil Lead Guidance recommends 3.5 µg/dL as the 95th percentile target blood lead level. The 2024 Updated Soil Lead Guidance also recommends that the EPA region adjust PRGs and cleanup levels to account for uncertainty, technical limitations (i.e., detection/quantification limits), and site-
specific soil lead background. QUESTION C: Has any other information come to light that could call into question the protectiveness of the
remedy? The September 2002 ROD did not require site maintenance procedures and ICs to ensure soils exceeding the site-wide unrestricted land use action levels are appropriately controlled. Post-removal data document concentrations of arsenic that exceed the site-wide unrestricted land use action level of 50 mg/kg. Administrative controls are still needed to ensure soils exceeding the site-wide unrestricted land use action levels are managed in the future. As required by the 2017 ESD, the 2019 Site Wide WLIP requires the placement of an EC by RTK on property in an OU that they intend to divest ownership within. The 2019 Site Wide WLIP is one of two administrative controls that the 2017 ESD requires RTK to create and implement. The second administrative control (for
portions of the OUs that include an operating facility) is the pending Site Wide OSMP (previously entitled the FEW Plan). The pending Site Wide OSMP will cover pending ICs to ensure soil management in the future in the form of an EC. The pending Site Wide OSMP will also cover maintenance for soil covers or engineered caps,
and it will restrict the use of seeds of plants capable of up-taking selenium. The 2019 Site Wide WLIP and pending Site Wide OSMP will be included under a future sitewide consent decree (CD). OU13 Smelter and Acid Plants, OU14 Refinery, and OU15 Mills and Tailings Pond QUESTION A: Is the remedy functioning as intended by the decision documents? The remedy is functioning as intended by the September 2002 ROD. No new contaminants of concern or contaminant sources have been identified since the September 2002 ROD and the commencement of the RA. Pursuant to the 2017 ESD, RTK has the option to clean up soils on its property (pursuant to the pending Site Wide OSMP) to the current applicable land use action level given the current land use or clean up soils to the site wide unrestricted land use action levels which includes lead (at 500 mg/kg). Cleaning soils to the site wide unrestricted land use action level for lead means the land can be used without restriction, including potential residential land use. The September 2002 ROD also noted that during the extraction of sand and gravel (borrow material) for off-site shipment and use, such extracted material has to comply with the site wide unrestricted land use action levels
including lead (500 mg/kg). This allowance could result in the use of extracted material during residential and recreational (i.e. playground) redevelopment projects.
Further action by RTK, EPA, and UDEQ is necessary to support the long-term protectiveness remedy (see Question C).

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QUESTION B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives (RAOs) used at the time of the remedy selection still valid?
The current soil cleanup levels selected in the September 2002 ROD and 2017 ESD were based on the estimated risks defined in the December 20, 1999 Final Preliminary Remediation Goals Report for Addressing Risks to Human Health from Exposures to Chemicals in Kennecott Soils (December 1999 PRG). There have been changes to the exposure assumptions and toxicity information for lead since the December 1999 PRG document was issued. In addition the site wide unrestricted land use action level for lead (500 mg/kg) is above the screening values published in EPA’s January 17, 2024 guidance. On January 17, 2024, the EPA OLEM released the “Updated Residential Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities” (2024 Updated Soil Lead Guidance), which updates the residential soil lead screening level (RSL) and removal management level (RML) for the CERCLA and RCRA programs and provides additional guidance for setting residential lead preliminary remediation goals (PRGs) and cleanup levels.
The 2024 Updated Soil Lead Guidance recommends that regions use the most current version of the Integrated Exposure Uptake Biokinetic model, with 5 µg/dL as the 95th percentile target blood lead level and site-specific environmental data (e.g., lead concentrations in various media and bioavailability) to develop PRGs and cleanup
levels for residential land use. If an additional source of lead (e.g., lead water service lines, lead-based paint, non-attainment areas where the lead concentrations exceed NAAQS) is identified, 2024 Updated Soil Lead Guidance recommends 3.5 µg/dL as the 95th percentile target blood lead level. The 2024 Updated Soil Lead Guidance also
recommends that the EPA region adjust PRGs and cleanup levels to account for uncertainty, technical limitations (i.e., detection/quantification limits), and site-specific soil lead background.
QUESTION C: Has any other information come to light that could call into question the protectiveness of the remedy? The September 2002 ROD did not require site maintenance procedures and ICs to ensure soils exceeding the site-wide unrestricted land use action levels are appropriately controlled. Post-removal reports provided by Kennecott in the late 1990s, as a function of the work required by the 1996 AOC for north-end soils, document concentrations of arsenic and lead exceeding the site-wide unrestricted land use action levels of 50 mg/kg and 500 mg/kg, respectively, and the industrial land use action level for selenium of 13,972 mg/kg. Administrative controls are still needed to ensure soils exceeding the site-wide unrestricted land use action levels are managed in
the future. As required by the 2017 ESD, the 2019 Site Wide WLIP requires the placement of an EC by RTK on property in an OU that they intend to divest ownership. The 2019 Site Wide WLIP is one of two administrative controls that the 2017 ESD requires RTK to create and implement. The second administrative control (for portions of the OUs that include an operating facility) is the pending Site Wide OSMP (previously entitled the FEW Plan). The pending Site Wide OSMP will cover pending ICs to ensure soil management in the future in the form of an EC. The pending Site Wide OSMP will also cover maintenance for soil covers or engineered caps, and
it will restrict the use of seeds of plants capable of up-taking selenium. The 2019 Site Wide WLIP and pending Site Wide OSMP will be included under a future sitewide CD. Active processing and waste management operations are regulated by a series of state permits, which function in conjunction with CERCLA-selected remedies to ensure existing CERCLA legacy issues are not exacerbated. The ability of the permits to address (in part) CERCLA legacy waste issues has been under assessment since the 2019 FYR through a State Permit Gap Assessment, which is still pending completion by the UDEQ. This assessment is also evaluating the closure requirements of state permits to determine if at closure CERCLA legacy waste issues will be addressed. OU19 Smelter Fallout
QUESTION A: Is the remedy functioning as intended by the decision documents? The remedy is functioning as intended by the September 2002 ROD. There is an active gravel pit, Black Rock Sand & Gravel pit, located in Black Rock Canyon that has been operational since at least 2023. Pursuant to the September 2002 ROD, RTK is responsible to prevent the transport of contaminated soils above the site wide unrestricted land use action levels off-site from Black Rock Gravel pit. No evidence suggests that contaminated soil is being transported off-site. RTK should continue to monitor the management of soils within the Black Rock

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Sand & Gravel pit. No new contaminants of concern or contaminant sources have been identified since the September 2002 ROD and the commencement of the RA.
Pursuant to the 2017 ESD, RTK has the option to clean up soils on its property (pursuant to the pending Site Wide OSMP) to the current applicable land use action level given the current land use or clean up soils to the site wide unrestricted land use action levels which includes lead (at 500 mg/kg). Cleaning soils to the site wide unrestricted land use action level for lead means the land can be used without restriction, including potential residential land use. The September 2002 ROD also noted that during the extraction of sand and gravel (borrow material) for off-site shipment and use, such extracted material has to comply with the site wide unrestricted land use action levels including lead (500 mg/kg). This allowance could result in the use of extracted material during residential and recreational (i.e. playground) redevelopment projects. Further action by RTK, EPA, and UDEQ is necessary to support the long-term protectiveness remedy (see
Question C). QUESTION B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives
(RAOs) used at the time of the remedy selection still valid? The current soil cleanup levels selected in the September 2002 ROD and 2017 ESD were based on the estimated risks defined in the December 30, 1999 Final Preliminary Remediation Goals Report for Addressing Risks to
Human Health from Exposures to Chemicals in Kennecott Soils (December 1999 PRG). There have been changes to the exposure assumptions and toxicity information for lead since the December 1999 PRG document was issued. In addition the site wide unrestricted land use action level for lead (500 mg/kg) is above the screening values published in EPA’s January 17, 2024 guidance. On January 17, 2024, the EPA OLEM released the “Updated Residential Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities” (2024 Updated Soil Lead Guidance), which updates the residential soil lead screening level (RSL) and removal management level (RML) for the CERCLA and RCRA programs and provides additional guidance for setting residential lead preliminary remediation goals (PRGs) and cleanup levels. The 2024 Updated Soil Lead Guidance recommends that regions use the most current version of the Integrated Exposure Uptake Biokinetic model, with 5 µg/dL as the 95th percentile target blood lead level and site-specific
environmental data (e.g., lead concentrations in various media and bioavailability) to develop PRGs and cleanup levels for residential land use. If an additional source of lead (e.g., lead water service lines, lead-based paint, non-attainment areas where the lead concentrations exceed NAAQS) is identified, 2024 Updated Soil Lead Guidance
recommends 3.5 µg/dL as the 95th percentile target blood lead level. The 2024 Updated Soil Lead Guidance also recommends that the EPA region adjust PRGs and cleanup levels to account for uncertainty, technical limitations (i.e., detection/quantification limits), and site-specific soil lead background.
Ecological Risk: Ecological risk assessment assumptions are still valid.
QUESTION C: Has any other information come to light that could call into question the protectiveness of the remedy? The September 2002 ROD did not require site maintenance tools and ICs to ensure soils exceeding the site-wide unrestricted land use action levels are appropriately controlled. Post-removal data document concentrations of arsenic and lead exceed the site-wide unrestricted land use action levels of 50 mg/kg and 500 mg/kg, respectively, and the industrial land use action level for selenium of 13,972 mg/kg. ICs are still needed to ensure soils exceeding the site-wide unrestricted land use action levels are managed in the future. As required by the 2017 ESD, the 2019 Site Wide WLIP requires the placement of an EC by RTK on property in an OU that they intend to
divest ownership. The 2019 Site Wide WLIP is one of two administrative controls that the 2017 ESD requires RTK to create and implement. The second administrative control (for portions of the OUs that include an operating facility) is the pending Site Wide OSMP (previously entitled the FEW Plan). The pending Site Wide
OSMP will cover pending ICs to ensure soil management in the future in the form of an EC. The pending Site Wide OSMP will also cover maintenance for soil covers or engineered caps, and it will restrict the use of seeds of plants capable of up-taking selenium. The 2019 Site Wide WLIP and pending Site Wide OSMP will be included
under a future sitewide CD.

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OU22 Great Salt Lake, Shoreline Wetlands, and OU23 North End Groundwater
QUESTION A: Is the remedy functioning as intended by the decision documents? OU22 - As noted in Section IV Data Review annual monitoring data collected during the five-year review period is inconclusive and does not support a determination that the remedy is functioning. Whether it be the lack of understanding the fate and transport of selenium in the NZW via trophic transfer ratios, not having a remedy that incorporates pertinent protection threshold levels for the pertinent COCs, or not having a thorough evaluation of potential sources of the COCS, these limitations hinder a functionality determination. Please see the following paragraphs for more detail. Though each pond, spring and canal that is monitored has demonstrated consistent concentrations of COCs in the media monitored under the selected remedy (i.e. water, sediment, and macroinvertebrate tissue), these concentrations are variable across each pond, spring and canal located in the North Zone Wetland (NZW) habitat.
Review of the annual maximum concentrations for COCs demonstrates some variability in each singular pond, spring, and canal. The statistical relevance of the variance is not well understood. Trophic transfer ratios have not been successfully developed across the monitored media, limiting the ability to understand the potential for
impacts to the resident and migratory avian community via direct contact, indirect consumption of water and sediment, and the dietary pathway through the consumption of macroinvertebrates (focal aspects of the remedial action objectives for the selected remedy). The habitat factors influencing the inability to calculate trophic transfer
ratios is still not well understood and warrants further investigation. Without the trophic transfer ratios, it is difficult to fully assess the effectiveness of response actions implemented to prevent ecological exposures associated with the elevated concentrations of COCs exhibited in the NZW (i.e. arsenic and selenium). The selected remedy does not include arsenic as a COC, and surface water concentrations of arsenic in the ponds, springs, and canals located in the NZW at times exceed the DWQ surface water quality standard for Class 3D waters. The Utah Class 3D standards are protective of waterfowl and their habitat, in addition to being the presumptive surface water quality standards for surface waters not classified by the DWQ; the NZW surface water is not classified. With the underlying groundwater system connectivity to the NZW habitat, arsenic concentrations in surface water could potentially be linked to the arsenic-impacted groundwater in OU23 (as is also potentially the case for the selenium-impacted groundwater). The selected remedy requires revision to ensure arsenic
concentrations in surface water continue to be monitored and compared to a selected threshold limit to ensure direct contact and consumption of surface water with elevated arsenic concentrations does not impact the avian receptor community. As it pertains to selenium in the NZW habitat, its mobilization is not well understood and the potential impacts to the resident and migratory avian community via the dietary pathway is not clear. Macroinvertebrate tissue
concentrations sampled over the five year review period have been variable, both in each individual pond, spring and canal of the NZW and across the entire habitat. A review of annual maximum concentrations documents (in each pond, spring and canal) periodic exceedances of the selected remedy threshold limit of 10 mg/Kg dry weight macroinvertebrate tissue concentration. Exceedance of this threshold limit indicates the remedy is not performing as expected and requires further source assessment for the selenium, which has been ongoing along with annual monitoring. Another issue affecting the ability to evaluate if the remedy is functioning effectively, to ensure avian receptors are protected from COCs in the NZW habitat, is that the pertinent end receptor (resident and migratory birds) and the pertinent sampling media (bird eggs) are not required to be monitored as it pertains to selenium concentrations in the habitat and food web. Decisions on functionality and protectiveness are to be made based on
macroinvertebrate tissue concentrations, which are quite variable and inconsistent, as noted above. Selenium is a teratogen affecting the hatchability and survivability of the chicks for the avian community. Based on literature and the DWQ water quality standard for Gilbert Bay of the Great Salt Lake (a similar habitat to the NZW area), whole bird eggs are the more direct media to be monitored to understand if avian receptors are being exposed to and affected by selenium in the habitat. Without the requirement to monitor bird eggs against an applicable protectiveness threshold limit and without a statistically relevant monitoring data set, whether the remedy (i.e.,

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removal of sediments with elevated selenium concentrations, and ongoing monitoring) is functioning to protect the avian receptors cannot be assessed.
The selected remedy requires modification to add bird egg selenium monitoring with protection thresholds and surface water arsenic monitoring with protection thresholds that are appropriate to protect the avian community. Ongoing monitoring in the NZW to continue the collection of water, sediment and macroinvertebrate samples for the assessment of trophic transfer ratios and potential water quality standards for selenium and continued assessment of potential selenium impacts to the resident and migratory avian community will require a long-term operation, maintenance and replacement plan (O,M&R Plan) incorporating a sampling and analysis plan (SAP) and quality assurance project plan (QAPP) for annual monitoring of the NZW. OU23 – The selected remedy of monitored natural attenuation is still under re-evaluation to assess why the plumes have not responded as predicted under the 2000 RIFS for OU23. The underlying groundwater plumes
(arsenic and selenium) at the refinery complex underwent an RI update between 2010 – 2012 (previously reported in 2013) and currently have an FFS report under review and revision. The EPA and DERR have identified concerns about source area dispersion/mobilization, gradient flow paths, and effectiveness of the capture system
and discharge locations of groundwater at the surface. Evidence still suggests a deeper groundwater flow path that has not been fully assessed. Once approved, the FFS report will be used to support modifications to the OU23 Remedial Action Objectives and the OU23 Selected Remedy. These revisions will require an updated decision
document (e.g., ROD Amendment, ESD). Monitoring data continues to demonstrate elevated concentrations of arsenic, selenium and sulfate in the groundwater underlying and emanating from the refinery and smelter facilities. Recent 2024 modeled isoconcentrations of arsenic in groundwater underlying the smelter facility have raised question about aquifer conditions (such as the redox potential and previously understood plume boundaries) and the conceptual site model for OU23. Groundwater monitoring data was last updated in 2018 and warrants an update to understand if the existing conceptual site model for OU23 is still valid. The last time the conceptual site model was updated was in 2018 as part of the RI Update and FFS for the groundwater underlying the refinery. The OU23 aquifer is currently classified by the State of Utah and Federal government as a source of drinking
water and the EPA’s National Contingency Plan (NCP) has the presumptive requirement to restore impacted aquifers to beneficial use, as determined by the EPA and local regulations (see 40 CFR § 300.430(a)(iii) (A)). The NCP also notes that “use of institutional controls shall not substitute for active response measures (e.g., treatment and/or containment of source material, restoration of ground waters to their beneficial uses) as the sole remedy unless such active measures are determined not to be practicable, based on the balancing of trade-offs among alternatives that is conducted during the selection of remedy" (see 40 CFR § 300.430(a)(iii)(D)). The selected
remedy for OU23 does not incorporate any requirements for groundwater quality standards to be met directly in the plume via treatment. Without a requirement for containment and potential treatment, the selected remedy of monitored natural attenuation (which has been shown to not be responding as modeled) may not attain concentration limits of the COCs to facilitate consumption. In addition the selected remedy does comply with the presumptive requirement under the NCP to restore impacted aquifers to the classified beneficial use. Groundwater that currently daylights in springs and seeps north of the refinery and smelter is captured and piped into RTK’s Process Water Circuit pursuant to the selected remedy. The groundwater commingled with other process water is managed in the North Tailings Impoundment. The North Tailings Impoundment is operated by RTK under a UPDES permit for surface discharge to the Great Salt Lake and a GWPP permit issued by the DWQ. The DWQ GWPP permit for the North Tailings Impoundment has been under review during this five-year review
period. The DWQ GWPP has raised concerns due to increasing concentrations of permit-restricted COCs at monitoring wells around the tailings impoundment. The DWQ GWPP has requested RTK to evaluate the reasons for the increasing concentration trends of the permit-restricted COCs. The persistent observations of elevated arsenic and selenium concentrations in the groundwater; increasing or at least consistently elevated concentrations observed in the NZW habitat (which OU23 underlies); effectiveness of
the groundwater capture along the reported discharge front noted in the conceptual model; and the potential

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expansion of the arsenic plume underlying the Smelter, supports the existing concerns about the effectiveness of the selected remedy. Revisions to the selected remedy should be considered once updates to the OU23 conceptual
site model and alternative assessments are completed for both the refinery and smelter portions of OU23. Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives (RAOs)
used at the time of remedy selection still valid? OU22 –As noted above under Question A, the RAOs for OU22: (1) eliminate or reduce the concentrations of hazardous substances in wetland habitats to reduce exposures to wildlife and (2) eliminate or reduce the concentrations of hazardous substances discharged into the Great Salt Lake. The RAOs for OU22 were focused on selenium concentrations in the dietary and surface water pathways that could lead to exposure risk to the resident and migratory avian community using the NZW and adjacent Great Salt Lake habitats. Arsenic was not considered under the selected remedy. Ongoing voluntary monitoring has reported elevated arsenic concentrations in the surface water, sediment and macroinvertebrate tissues samples. As noted in Section IV – Data Review, and
above in Question A, arsenic concentrations have been detected above the DWQ water quality standard for arsenic in Class 3D waters (150 µg/L). The remedy needs to be revised to add arsenic as a COC, establish applicable threshold limits to measure potential exposure risks to the resident and migratory avian community in
the NZW, and to ensure discharges of surface water from the NZW to the Great Salt Lake (via the UPDES outfall #004) do not exceed arsenic limits listed in the DWQ UPDES permit.
Also noted in Question A for OU22, the selected remedy focused on the dietary pathway to assess the potential for exposure risk from selenium concentrations mobilized in the NZW habitat. Based on literature and the DWQ water quality standard for selenium in the waters of Gilbert Bay of the Great Salt Lake, whole bird egg concentration of selenium is the more applicable media to sample for assessment of impairment to the resident and migratory avian community. The lack of trophic transfer ratios to equate the dietary pathway to actual bird egg concentrations further hinders the ability to assess whether the selected remedy is protective and if the RAOs are being met. The OU22 selected remedy needs to be reevaluated and potentially modified to establish bird egg threshold limits for selenium; selection of response actions to take if the threshold limits are exceeded; add arsenic as a COC; set a threshold limit for arsenic in surface water; and require further assessment to develop trophic transfer ratios to understand how to more effectively control the input and mobilization of arsenic and selenium in the NZW habitat.
Monitoring in OU22, including the voluntary assessment of bird eggs, continues to demonstrate exposure assessments missed the inclusion of arsenic as a COC and that the transport of arsenic and selenium in the NZW habitat may lead to exposure risks in the avian community. Previous investigations failed to assess all potential input pathways of arsenic and selenium, including deeper aquifer mobilization pathways for the selenium plume at the Refinery. Recent evidence on potential arsenic concentrations in groundwater mobilized from under the
Smelter facility may also indicate an expanded arsenic plume (and be a potential source to elevated arsenic observed in the OU22 NZW habitat surface water data). OU23 –The RAOs for OU23: (1) Minimize or remove the potential for on-site (wetlands and Great Salt Lake) ecological risk to receptors of concern by limiting the migration and uptake of constituents of concern in excess of risk-based concentrations for sensitive species; (2) Minimize or remove the potential for on-site human risk via ingestion by limiting exposure to ground water containing constituents of concern exceeding risk-based concentrations for human health or drinking water MCLs; and (3) Minimize or remove the potential for on-site ecological risk via artesian flow and springs into the Garfield wetlands to receptors of concern by limiting the migration of constituents of concern in excess of risk-based concentrations for sensitive species, have not been attained.
The selected remedy presumed that the aquifer would not be accessed for the production of drinking water. However, pursuant to Section 40 CFR 300.430(a)(1)(iii)(F) of the NCP, the EPA expects to return usable groundwaters to their beneficial uses wherever practicable, within a timeframe that is reasonable given the particular circumstances of the site. When restoration of groundwater to beneficial uses is not practicable, the EPA expects to prevent further migration of the plume, prevent exposure to the contaminated groundwater, and
evaluate further risk reduction. Simply applying a drilling restriction over the aquifer impacted in OU23 will not

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comply with this expectation. The originally-selected remedy did not require extraction and treatment of the impacted groundwater (thus exposure assumptions and risk, for human health and ecological, was not fully
evaluated). The current effort to re-evaluate alternatives, in light of the RAO’s goal to protect human health and comply with expected aquifer restoration requirements of the NCP, should result in the evaluation of alternatives that restore the aquifer to applicable cleanup levels for all COCs. The capture of groundwater as artesian flow at the springs in OU22 may be incomplete. The ongoing re-evaluation of the original 2000 RI/FS at OU23 must include a re-evaluation of the conceptual site model to assess if further alternative assessment is warranted at both the Smelter and Refinery portions of OU23. The re-evaluation should also develop cleanup levels for arsenic and selenium in the groundwater to ensure concentrations are appropriately managed. Question C: Has any other information come to light that could call into question the protectiveness of the
remedy? The selected remedies for OU22 and OU23 (in part) rely on DWQ permits issued by the UPDES and GWPP
programs to manage discharges to the Great Salt Lake (i.e. UPDES Outfall #004 from Pond 8 of the NZW) and
active operations above and near OU22 and OU23 (i.e. tailings impoundment). As noted in Section IV – Data
Review and in Question B, there have been compliance issues reported under both respective permits. DWQ
notified the EPA that available data denotes a 20-foot settlement of the drainage blanket beneath the tailings
impoundment. The information available suggests that the interaction between the base of the tailings
impoundment and the surrounding groundwater may be different from DWQ’s, DERR’s, and the EPA’s current
understanding and that further evaluation is necessary.

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VI. ISSUES/RECOMMENDATIONS
Issues/Recommendations
OU(s) without Issues/Recommendations Identified in the Five-Year Review:
None

Issues and Recommendations Identified in the Five-Year Review:

OU(s): 8, 13, 14, 15, and 19 Issue Category: Institutional Controls
Issue: In 2016, Salt Lake County's governance structure was
changed, which affected Salt Lake County’s ability to address pre-screening of land disturbance projects in areas of the Site with waste left in place exceeding the site-wide unrestricted land use action levels. The Site OUs (except for OU9) are predominantly subject to RTK’s administrative controls (2019 Site Wide WLIP and the pending Site Wide OSMP) while the OUs and property therein remain in RTK ownership. Upon cessation of operations and property divestment RTK is required under the 2019 Site Wide WLIP to place an EC over the property if soils contain metals above the site specific unrestricted land
use action levels. However, the EPA and DERR have agreed that the SLCoHD institutional control listed in Title 9 Chapter 9.5 is also applicable if an EC is not placed or complied with (2017 ESD explains the applicability of the SLCoHD IC). Based on the Salt Lake County governance change the SLCoHD IC is currently not being implemented effectively which raises concerns about its usefulness as a backup IC.
Recommendation: DERR will coordinate with the SLCoHD
to determine the resource limitations that are hindering the implementation of the Title 9 Chapter 9.5 ordinance and ongoing
communications between SLCoHD and other local agencies overseeing redevelopment. DERR will provide a
recommendation (via a technical memorandum) to the EPA on how best to resolve the impediments to the ordinance’s implementation. Solutions should include the development of educational material to assist the public’s understanding of how to comply with the ordinance. In addition, DERR will coordinate
with the EPA on the development of a site wide ordinance
implementation plan for all applicable OUs and provide such to SLCoHD and other local agencies overseeing redevelopment. The milestone date is set pursuant to this solution focused work. DERR will also audit the implementation of the SLCoHD ordinance and report on such in future FYRs.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
No Yes State EPA/State 6/30/2027

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OU(s): 8, 13, 14, 15, and 19 Issue Category: Operations and Maintenance
Issue: In operable units where there are active operations, the management of soils along with maintenance of engineering controls, implementation of ICs, inspections, and reporting on maintenance actions is not covered under an active operations and
maintenance plan.
Recommendation: RTK will complete the pending Site Wide OSMP which in part will cover maintenance of engineering controls, implementation of ECs, development of site-specific work plans to address further soil management and control of seeds of plants capable of up-taking selenium.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP EPA/State 1/15/2026

OU(s): 8, 13, 14, 15, and 19 Issue Category: Operations and Maintenance
Issue: RTK is required to update maps pursuant to the 2017 ESD at a minimum of every
five years. RTK has not updated the maps
Recommendation: RTK will coordinate with the EPA and DERR and update previously provided GIS maps supporting local institutional controls. GIS data shall be provided in an electronic format (in compliance with EPA data requirements and guidance
for spatial data).
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP EPA/State 5/30/2025

OU(s): 8, 13, 14, 15, and 19 Issue Category: Remedy Performance
Issue: On January 17, 2024, the EPA issued the Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities that lowered the recommended
regional screening levels for lead-contaminated soil in residential areas.
Recommendation: In accordance with the guidance, the EPA should determine whether further investigation is warranted and if the current unrestricted land use action
level for lead is still applicable.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes EPA/State EPA/State 8/19/2029

OU(s): 15 Issue Category: Remedy Performance
Issue: RTK is required to comply with State Permitting Authorities including GWPP permit limitations as part of the selected remedy for OU15. Monitoring of compliance wells has identified several exceedances of discharge limits over the past five years.
Recommendation: RTK has submitted a Source Area Assessment to DWQ, which DWQ is reviewing. DWQ will collaborate with DERR during their evaluation of the RTK

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Source Area Assessment. DERR will provide a technical memorandum to the EPA with recommendations on the need for further CERCLA response at OU15 based on the results of DWQ’s evaluation of the source area assessment and contaminant increases in compliance wells at OU15.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes State EPA/State 12/30/2026

OU(s): 15 Issue Category: Changed Site Conditions
Issue: The integrity of the Tailings Impoundment and the underlying natural clay layer
on which the impoundment is constructed has been questioned by the DWQ GWPP.
Recommendation: DWQ is currently evaluating the integrity of the natural clay liner during renewal of the tailings impoundment GWPP permit. DWQ will collaborate with DERR during its evaluation. Issues with the integrity of the liner and recommendations on potential further response action under the selected remedy for OU15 will be reported by
DERR to the EPA in a technical memorandum.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes State EPA/State 12/30/2026

OU(s): 22 Issue Category: Remedy Performance
Issue: The current selected remedy does not include a protection threshold limits for
selenium in bird eggs or arsenic in surface water. Both selenium and arsenic concentrations in the NZW habitat have been variably increasing in the media that is (in
part) voluntarily sampled by RTK under the 2003 monitoring plan as amended in 2008, 2014 and 2020.
Recommendation: The EPA and DERR will revise the OU22 remedy in a decision
document to incorporate a selenium protection threshold for bird eggs and a surface water standard for arsenic and require monitoring and trend assessment for both (in compliance with applicable EPA guidance for data gathering).
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes EPA/State

EPA/State 9/30/2026

OU(s): 22 Issue Category: Remedy Performance
Issue: Current arsenic and selenium concentration trends in surface water and bird eggs, respectively, in samples collected under the 2003 wetland monitoring plan and the 2008 enhanced biological monitoring plan (as amended in 2014 and 2020) do not support a conclusion that response actions to date in the wetland habitat are protective.
Recommendation: RTK will continue short-term bird egg collection (along with the collection of water, sediment and macroinvertebrate tissue samples) under a short-term sampling and analysis plan (SAP) and quality assurance project plan (QAPP), in compliance with applicable EPA Guidance. The short term SAP/QAPP should maximize

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efforts to collect a statistically representative number of samples necessary to support assessment of protectiveness and evaluate effects on collecting enough samples to be statistically representative.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP EPA/State 11/30/2025

OU(s): 22 Issue Category: Remedy Performance
Issue: The EPA and DERR are preparing modifications for the OU22 selected remedy to add arsenic as a COC, require bird egg monitoring, and select protection threshold
limits for selenium in bird eggs. These additions to the remedy will allow RTK, the EPA and DERR to assess whether arsenic and selenium concentrations trends in surface water and bird eggs (respectively) are protective of the avian receptors using the wetland habitat. Once a decision document is issued for modifying the OU22 selected remedy, a long-term monitoring plan is needed, that complies with applicable EPA guidance, to provide monitoring procedures and assess protectiveness of the modified selected remedy.
Recommendation: Following issuance of decision document modifying the OU22
selected remedy, RTK will submit to the EPA and DERR a final long-term monitoring
plan for the NZW in OU22.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP EPA/State 4/30/2027

OU(s): 22 Issue Category: Remedy Performance
Issue: On January 17, 2024, the EPA issued the “Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities” (2024 Updated Soil Lead Guidance), which lowered recommended regional screening levels for lead-contaminated soil in residential areas. As noted in footnote 1 of the Updated Soil Lead Guidance, residential areas include areas where children have unrestricted access to lead-
contaminated soil, including, but not limited to playgrounds, parks, and other recreational areas and green ways. Portions of OU22, especially along the Great Salt Lake shoreline, currently receive recreational use. The scope of a previous study and spatial representativeness of collected lead data for beach material should be re-evaluated to reassess exposure assumptions.
Recommendation: In light of the Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities, the previous exposure assumptions, toxicity data, cleanup levels, and RAOs need to be reevaluated for the recreational areas along the Great Salt Lake beaches and shoreline.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes EPA/State EPA/State 8/29/2029

38

OU(s): 23 Issue Category: Operations and Maintenance
Issue: The OU23 selected remedy (i.e. monitored natural attenuation, capture and containment of impacted groundwater at seeps and springs) does not require reporting monitoring results. Reporting on an annual basis to document the progress of the selected remedy and responsiveness of the plumes to the selected remedy, is necessary. RTK has
not consistently reported on the progress of the selected remedy on a voluntary basis.
Recommendation: RTK will provide to the EPA and DERR an annual monitoring report for OU23 and revise such in the future based on further remedy modifications under decisions documents EPA and DERR complete.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP

EPA/State 11/14/2025

OU(s): 23 Issue Category: Remedy Performance
Issue: The Refinery selenium and arsenic plumes have not decreased in concentration under the MNA remedy, as predicted in the 2000 RIFS. In 2010 RTK initiated an update
to the 2000 RI (completed in 2013) and a FFS (submitted to the EPA and DERR in 2020). The EPA and DERR have outstanding concerns with the FFS pertaining to evaluation methodology and the scope of alternatives assessed. Reduced response by the plumes to
the selected remedy could warrant further response action, including efforts to attain the presumptive requirements of the NCP to restore the impacted aquifer to beneficial use.
Recommendation: RTK will collaborate with the EPA and DERR and complete the
pending FFS for the Refinery plumes.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP

EPA/State 1/27/2026

OU(s): 23 Issue Category: Remedy Performance
Issue: Recent projections of arsenic concentrations in groundwater underlying and emanating from the Smelter facility suggest the extent of potential arsenic impacts are not well understood and raises questions about the conceptual site model and modeling performed in the 2000 RIFS.
Recommendation: RTK will initiate an effort to update current aquifer conditions and
the conceptual site model for the Smelter portion of OU23, collaborate with the EPA and
DERR and complete an RI Update for the Smelter portion of OU23.
Affect Current Protectiveness Affect Future Protectiveness Party Responsible Oversight Party Milestone Date
Yes Yes PRP EPA/State 1/27/2026

39
OTHER FINDINGS
In addition, the following are recommendations that were identified during the FYR and may improve the performance of the remedy, but do not affect current protectiveness:
• OU9 – Magna Soils
OU 9 was determined to be protective in the 2014 FYR. The 2014 FYR stated that the “no further action remedy at OU9 is protective of human health and the environment because no unacceptable exposures were found during site assessment studies and exposure conditions have not changed.” At that time, no further five-year reviews were required because average soil concentrations of the contaminants of concern were less than the current site-wide unrestricted land use action level for lead (500 mg/kg). On January 17, 2024, the EPA issued Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities that lowered recommended regional screening levels for lead-contaminated soil in residential areas. In accordance with the updated guidance, the new recommended screening levels (200 mg/kg and 100 mg/kg lead) and other site-specific information will be used to determine whether further investigation is warranted and whether additional response actions are necessary. Based on the guidance, the decisions for OU9 Magna soils should be re-evaluated.
• OU14 – Refinery Moderate spills and cracks were observed in the Tank House subfloor of the Refinery complex during the site inspection. Historical releases underneath this facility have been noted (September 2002 ROD) to have contributed to groundwater impacts. Previous potential releases specifically from the Tank House
subfloor basement have not been delineated. During the inspection, there was no indication of an active release observed. These findings will be discussed with RTK personnel to evaluate ways to reduce/eliminate accidental releases in the future. The subfloor should be inspected during the next five-year review period.
• OU15 Mills and Tailings Pond The City of Magna has raised concerns about dust generated off the Tailings Impoundments (South and North) complex which blows over their community, carrying potential elevated metals concentrations.
The September 2002 ROD selected a remedy for OU15 requiring compliance with permits issued by the DAQ (dust control), DWQ GWPP and UPDES programs (groundwater and surface water protection), and DOGM (reclamation). It is recommended in light of the dust concerns that DERR include an assessment
of the air quality permits for the Tailings Impoundments (North and South) (and other DAQ permitted facilities at the Site) under the pending State Permit Gap Assessment to ascertain if further CERCLA response action is necessary.

• OU15 – Mills and Tailings Pond As part of this current Five-Year Review, the CERCLA agencies evaluate the performance of RTK and their compliance with the respective State Permitting Authorities. The DWQ reported that RTK’s current compliance status under their UPDES permit is mixed, but on average has maintained compliance with the UPDES limitations. RTK’s ongoing compliance will continue to be evaluated during the next Five-Year Review period and DERR will coordinate with DWQ on potential UPDES permit non-compliance matters on an annual basis to assess if there is a potential impact to the protectiveness of the selected remedy.
• OU22 - Great Salt Lake, Shoreline Wetlands, and OU23 - North End Groundwater The September 2002 ROD selected ongoing monitoring as part of the selected remedies for OU22 and OU23. Since 2003, monitoring in OU22 has proceeded under a series of short-term monitoring plans; the original in 2003 subsequently updated in 2008, 2014 and 2020. Monitoring in OU23 has continued under the site-wide groundwater characterization and monitoring plan, GCMP (last updated in 2016). The GCMP document was first used by the DWQ GWPP for its groundwater permits at operating facilities in
the operable units of the Kennecott North Zone. Subsequently, in the 1990s, the EPA agreed on its use for

40
the groundwater monitoring at OU23 and other OUs. Reporting on annual monitoring data is not currently a requirement and has been performed to date voluntarily pursuant to mutual agreement by
RTK, the EPA and UDEQ. Annual monitoring and reporting of such should be addressed as the remedies
for OU22 and OU23 are reevaluated. Following any modifications to the OU22 and OU23 selected
remedies, long-term monitoring plans will need to be developed in accordance with the EPA’s guidance
for all sampling and monitoring activities.
• OU22 – Great Salt Lake, Shoreline and Wetlands Review of previous characterization and monitoring data for the NZWs suggests that lead concentrations in sediments (since the initial removal work in the NZW from 1999 to 2001) could exceed potentially applicable ecological screening levels recommended by the Site’s BTAG. The recommended ecological screening levels include the Probable Effect Concentration (PEC or LOEL) and Threshold Effect Concentration (TEC or NOEL) screening levels of 128.0 mg/Kg and 35.8 mg/kg respectively (as noted in January 2000, Development and Evaluation of Consensus-Based Sediment Quality Guidance for
Freshwater Ecosystems, D.D. MacDonald – C.G. Ingersoll, T.A. Berger). From the same referenced document, potentially applicable cadmium screening levels for sediments are 4.99 mg/Kg - PEC and 0.99 mg/Kg - TEC respectively. An assessment of sediment lead and cadmium (a site-wide COC)
concentrations from the monitoring data collected at the NZWs to date (both maximum and mean concentrations) should be compared against these potentially applicable ecological screening levels to ascertain if lead and cadmium are at concentrations in sediment that could impact receptors in the North
Zone Wetlands.
• OU23 – North End Groundwater If the EPA determines that the OU23 selected remedy requires modifications, this will likely require a reassessment of the current groundwater classifications and the related ARARs. A 1997 Directive - The Role of CSGWPPs in EPA Remediation Programs, suggests that the EPA GW classification system should be used and that most of the north zone is expected to be a potential source of drinking water using that classification scheme (See USEPA. 1986. Guidelines for Ground-Water Classification Under the EPA Ground-Water Protection Strategy. Final Draft. December). This suggests that the highest beneficial use of the groundwater is drinking water and that restoration is expected under the NCP. The applicability of the federal, state groundwater classification and use standards will require re-assessment.
VII. PROTECTIVENESS STATEMENT

Protectiveness Statement(s)
Operable Units: 8, 13, 14,
15, and 19
Protectiveness Determination:
Protectiveness Deferred
Protectiveness Statement: A protectiveness determination of the remedy cannot be made at this time until further information is obtained. Further information will be obtained by applying the 2024 Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities and using the recommended lowered screening levels to determine whether further investigation is warranted and
whether additional response actions are necessary for the remedy to remain protective. It is expected these steps could take approximately five years to complete, after which a protectiveness determination will be made using the information received through application of the 2024 Updated Soil Lead Guidance for CERCLA sites and RCRA Corrective Action Facilities.
Operable Units: 22 and 23 Protectiveness Determination: Not Protective
Protectiveness Statement: Given the uncertainties concerning the fate and transport of selenium in the groundwater system underlying the Refinery complex, the uncertainties concerning the concentrations

41
and transport of arsenic in the groundwater system underlying and emanating from the Smelter complex, the inability of the current capture system to effectively manage the selenium-impacted groundwater, continued and increasing concentrations of selenium in bird eggs, and the lack of evaluation of appropriate measures to reduce the toxicity of the leaching potential of source material,
the selected remedies for OU22 and OU23 are currently not protective. For the remedy to be protective, the increasing trends of selenium in bird eggs and arsenic in surface water need to be evaluated to understand their significance. Threshold limits for bird eggs and surface water are needed along with the addition of arsenic as a COC. Ongoing short-term bird egg monitoring in OU22 needs to continue to develop a statistically representative data set for bird eggs. The monitoring should be performed under a short-term SAP/QAPP for monitoring on the NZW (including bird eggs) developed
in accordance with EPA Guidance. Following any modifications to the OU23 selected remedy, a long-term monitoring will need to be developed in accordance with the EPA’s guidance. The completion of the OU23 Refinery FFS is necessary to understand how to best modify the selected remedy to address further source control and management. Recent projections of arsenic concentrations in groundwater underlying and emanating from the Smelter facility suggest the extent of potential arsenic impacts are not well understood and raises questions about the conceptual site model and modeling performed in the 2000 RIFS. RTK needs to initiate an effort to update current aquifer conditions and the conceptual site model.
VIII. NEXT REVIEW The next five-year review report for the Kennecott North Zone Proposed Superfund Site is required five years from the completion date of this review.

APPENDIX A
REFERENCE LIST

REFERENCE LIST Arthur Stepback Repository Summary for Third Five-Year Review, Kennecott North Zone. Prepared by Rio Tinto Kennecott July 2024. Black Rock Canyon, Phase I Mining Boundary Impacted Soil Management. Prepared by Geneva Rock.
September 13, 2022. Compilation of Soil and Groundwater Action Levels Technical Memorandum. Prepared by Utah Department of Environmental Quality and U.S. Environmental Protection Agency. December 29, 2015 Development and Evaluation of Consensus-Based Sediment Quality Guidance for Freshwater
Ecosystems, D.D. MacDonald – C.G. Ingersoll, T.A. Berger, January 13, 2000.
Explanation of Significant Differences. Kennecott North Zone Site & Kennecott South Zone Site. Magna and Copperton, Utah. U.S. Environmental Protection Agency & Utah Department of Environmental Quality, August 2017. Final Preliminary Remediation Goals for Addressing Risks to Human Health from Exposure to Chemicals in Kennecott Soils. December 30, 1999. First Five-Year Review Report for Kennecott North Zone Superfund Site. Prepared by the Utah Department of
Environmental Quality and U.S. Environmental Protection Agency. June 17, 2014. Memorandum of Understanding – Kennecott Utah Copper Corporation, Utah Department of Environmental
Quality, U.S. Environmental Protection Agency. May 20, 1995. Record of Decision. OU8, 9, 13, 14, 15, 18, 19, 22, 23, 24 Kennecott North Zone and Kennecott South Zone Site.
Magna & Copperton, Utah. EPA & UDEQ. September 26, 2002. Rio Tinto Kennecott Copper – Environmental Land and Water Ground Arthur Stepback Repository Operations and Maintenance Plan Kennecott North Zone Site. Rio Tinto Kennecott Copper. June 2018. Second Five-Year Review Report for Kennecott North Zone Superfund Site. Prepared by the Utah Department of Environmental Quality and U.S. Environmental Protection Agency. August 19, 2019. Site-Wide Management Plan for Wastes Left in Place. Kennecott North Zone and South Zone Sites. Prepared by Rio Tinto Kennecott – Environmental, Land, and Water. August 12, 2019.
Utah Division of Natural Resources. Plate 1 Total-Dissolved-Solids Concentration Map for the Basin-Fill Aquifer, Salt Lake Valley, Salt Lake County, Utah. Scale 1:75,000. Aquifer Classification: Utah Ground Water Quality Protection Program. https://deq.utah.gov/wp-content/uploads/Salt-Lake-Valley-Plate-01-
Aquifer-Large.jpg Utah Division of Natural Resources. Plate 2 Ground-Water Quality Classification Map for the Basin-Fill Aquifer,
Salt Lake Valley, Salt Lake County, Utah. Scale 1:75,000. Aquifer Classification: Utah Ground Water Quality Protection Program. https://deq.utah.gov/wp-content/uploads/Salt-Lake-Valley-Plate-02-Aquifer-Large.jpg
Utah Division of Natural Resources. Plate 3 Potential Contaminant Source Map for the Basin-Fill Aquifer, Salt

Lake Valley, Salt Lake County, Utah. Scale 1:75,000. Aquifer Classification: Utah Ground Water Quality Protection Program. https://deq.utah.gov/wp-content/uploads/Salt-Lake-Valley-Plate-03-Aquifer-
Large.jpg

Appendix B
Site Map

&(
&(
&(
&(
&(
TAILINGSIMPOUNDMENT
UTAH POWERPLANT
COPPERTONCONCENTRATOR
SMELTER REFINERY
SMELTERFALLOUTAREAS
NORTH ZONE WETLANDS / NORTH ZONE GROUNDWATER
µ1:130,000
0 1 2 3 MI
0 2.5 5 KM
DATE: 4/5/2024 12:32:32 PM
CREATED BY: TERESA.COCKAYNE
FIGURE 4-1 NORTH ZONE OUS
NAD 1983 STATEPLANE UTAH CENTRAL FIPS 4302 FEET
© 2024 RIO TINTO KENNECOTT
OU22: GREAT SALT LAKE WETLANDS
OU8: WWTP AND SLUDGE PONDS
OU9: MAGNA SOILS
OU13: SMELTER AND ACID PLANTS
OU15: MILLS AND TAILINGS POND
OU19: SMELTER FALLOUT
OU23: NORTH END GROUNDWATEROU14: REFINERY
KENNECOTT NORTH ZONE SITE

Appendix C
Site Inspection Checklist

C-2
Five-Year Review Site Inspection Checklist
I. SITE INFORMATION
Site name: Kennecott North Zone Date of inspection: May 2023 to February 2024
Location and Region: Salt Lake County, Utah 8 EPA ID: UTD070926811
Agency, office, or company leading the five-year review: DERR Weather/temperature: Variable – Cold, Cloudy, Foggy to Hot, Sunny
Remedy Includes: (Check all that apply)
X Landfill cover/containment X Monitored natural attenuation
□ Access controls □ Groundwater containment
X Institutional controls □ Vertical barrier walls
X Groundwater pump and treatment
X Surface water collection and treatment
X Other: Surface water monitoring, soils management
Attachments: □ Inspection team roster attached □ Site map attached
II. INTERVIEWS (Check all that apply)
1. O&M site manager: Teresa Cockayne Principal Advisor - Remediation March 5, 2025 Name Title Date Interviewed X at site □ at office □ by phone Phone no. ______________
Problems, suggestions; □ Report attached ________________________________________________
__________________________________________________________________________________
2. O&M staff ____________________________ ______________________ ____________ Name Title Date Interviewed □ at site □ at office □ by phone Phone no. ______________
Problems, suggestions; □ Report attached _______________________________________________
__________________________________________________________________________________

C-3
3. Local regulatory authorities and response agencies (i.e., State and Tribal offices, emergency response office, police department, office of public health or environmental health, zoning office, recorder of deeds, or other city and county offices, etc.) Fill in all that apply.
Agency ____________________________ Contact ____________________________ __________________ ________ ____________ Name Title Date Phone no. Problems; suggestions; □ Report attached _______________________________________________
__________________________________________________________________________________ Agency ____________________________ Contact ____________________________ __________________ ________ ____________ Name Title Date Phone no. Problems; suggestions; □ Report attached _______________________________________________
__________________________________________________________________________________ Agency ____________________________ Contact ____________________________ __________________ ________ ____________ Name Title Date Phone no. Problems; suggestions; □ Report attached _______________________________________________
__________________________________________________________________________________
Agency ____________________________ Contact ____________________________ __________________ ________ ____________ Name Title Date Phone no.
Problems; suggestions; □ Report attached _______________________________________________
__________________________________________________________________________________
4. Other interviews (optional) □ Report attached.

C-4
III. ON-SITE DOCUMENTS & RECORDS VERIFIED (Check all that apply)
1. O&M Documents □ O&M manual X Readily available X Up to date □ N/A
□ As-built drawings X Readily available X Up to date □ N/A
□ Maintenance logs X Readily available □ Up to date □ N/A
Remarks____Pending site operation & maintenance plans are in development for operational soils
management, as well as clarified remedies for OU22 and OU23. _______________
2. Site-Specific Health and Safety Plan X Readily available □ Up to date □ N/A
□ Contingency plan/emergency response plan □ Readily available □ Up to date □ N/A
Remarks__Current health and safety, and contingency plan is in the 1996 AOC work plan.
3. O&M and OSHA Training Records □ Readily available □ Up to date X N/A
Remarks__________________________________________________________________________
4. Permits and Service Agreements
X Air discharge permit □ Readily available X Up to date □ N/A
X Effluent discharge □ Readily available X Up to date □ N/A
□ Waste disposal, POTW □ Readily available □ Up to date □ N/A
X Other permits_DOGM & SLCo □ Readily available X Up to date □ N/A
Remarks____See Appendix E for an evaluation of RTKC’s compliance with permits.
5. Gas Generation Records □ Readily available □ Up to date X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
6. Settlement Monument Records □ Readily available □ Up to date X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
7. Groundwater Monitoring Records X Readily available □ Up to date □ N/A
Remarks__________________________________________________________________________
_________________________________________________________________________________
8. Leachate Extraction Records X Readily available □ Up to date □ N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
9. Discharge Compliance Records X Air X Readily available □ Up to date □ N/A
X Water (effluent) X Readily available □ Up to date □ N/A
Remarks_See Appendix E for permit compliance. _______________________________
10. Daily Access/Security Logs □ Readily available □ Up to date X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________

C-5
IV. O&M COSTS
1. O&M Organization □ State in-house □ Contractor for State
X PRP in-house □ Contractor for PRP
□ Federal Facility in-house □ Contractor for Federal Facility
□ Other__________________________________________________________________________
_________________________________________________________________________________
2. O&M Cost Records □ Readily available □ Up to date X N/A
□ Funding mechanism/agreement in place
Original O&M cost estimate____________________ □ Breakdown attached
Total annual cost by year for review period if available From__________ To__________ __________________ □ Breakdown attached
Date Date Total cost From__________ To__________ __________________ □ Breakdown attached
Date Date Total cost From__________ To__________ __________________ □ Breakdown attached
Date Date Total cost
From__________ To__________ __________________ □ Breakdown attached
Date Date Total cost
From__________ To__________ __________________ □ Breakdown attached
Date Date Total cost
3. Unanticipated or Unusually High O&M Costs During Review Period Describe costs and reasons: __________________________________________________________ _________________________________________________________________________________
V. ACCESS AND INSTITUTIONAL CONTROLS X Applicable □ N/A
A. Fencing
1. Fencing damaged □ Location shown on site map □ Gates secured □ N/A
Remarks___See “B” below
B. Other Access Restrictions
1. Signs and other security measures □ Location shown on site map X N/A
Remarks___Access to the RTKC operable units covered in this review is controlled by RTKC security personnel, in part using fencing, remote access-key entry gates (overall site is not fenced, critical operational areas as well as portions of OU22 – wetlands).

C-6
C. Institutional Controls (ICs)
1. Implementation and enforcement Site conditions imply ICs not properly implemented □ Yes X No □ N/A
Site conditions imply ICs not being fully enforced □ Yes X No □ N/A
Type of monitoring (e.g., self-reporting, drive by) _Self reporting, drive by observing infractions
Frequency _By the PRP – monthly, by UDEQ – annually if not more frequent Responsible party/agency Currently while property is held in ownership – PRP
____________________________________________________________ Contact ____________________________ __________________ ________ ____________
Name Title Date Phone no.
Reporting is up-to-date □ Yes □ No X N/A
Reports are verified by the lead agency □ Yes □ No X N/A
Specific requirements in deed or decision documents have been met X Yes □ No □ N/A
Violations have been reported □ Yes X No □ N/A
Other problems or suggestions: □ Report attached
___________________________________________________________________________ __As noted in the report, environmental covenants are pending for the operable units which will be used to implement proprietary institutional controls. IC restrictions are being met already. _____________
2. Adequacy □ ICs are adequate □ ICs are inadequate X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
_________________________________________________________________________________
D. General
1. Vandalism/trespassing □ Location shown on site map X No vandalism evident
Remarks__________________________________________________________________________ _________________________________________________________________________________
2. Land use changes on site X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
3. Land use changes off site X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
VI. GENERAL SITE CONDITIONS
A. Roads X Applicable □ N/A
1. Roads damaged □ Location shown on site map X Roads adequate □ N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________

C-7
B. Other Site Conditions
Remarks ______________________________________________________________
VII. LANDFILL COVERS X Applicable □ N/A
A. Landfill Surface
1. Settlement (Low spots) □ Location shown on site map X Settlement not evident
Areal extent______________ Depth____________
Remarks____________________________________________________________
__________________________________________________________________
2. Cracks □ Location shown on site map X Cracking not evident
Lengths____________ Widths___________ Depths__________
Remarks____________________________________________________________ __________________________________________________________________
3. Erosion □ Location shown on site map X Erosion not evident
Areal extent______________ Depth____________
Remarks__________________________________________________________________________ _________________________________________________________________________________
4. Holes □ Location shown on site map X Holes not evident
Areal extent______________ Depth____________ Remarks__________________________________________________________________________ _________________________________________________________________________________
5. Vegetative Cover X Grass X Cover properly established X No signs of stress
□ Trees/Shrubs (indicate size and locations on a diagram)
Remarks: Generally, vegetative covers are well established at the partially closed, closed, operational landfills, repository, and capped facilities. The cap on the Old PM Building in OU14 is not completely re-vegetated; however, it is entirely fenced off inside RTKC’s secured perimeter.
6. Alternative Cover (armored rock, concrete, etc.) X N/A
Remarks__________________________________________________________________________ _________________________________________________________________________________
7. Bulges □ Location shown on site map X Bulges not evident
Areal extent______________ Height____________ Remarks__________________________________________________________________________
_________________________________________________________________________________
8. Wet Areas/Water Damage X Wet areas/water damage not evident

9. Slope Instability □ Slides □ Location shown on site map X No evidence of slope instability
Areal extent______________ Remarks_____________________________________________
_________________________________________________________________________________

C-8
B. Benches □ Applicable X N/A
(Horizontally constructed mounds of earth placed across a steep landfill side slope to interrupt the slope in order to slow down the velocity of surface runoff and intercept and convey the runoff to a lined channel.)
C. Letdown Channels □ Applicable X N/A
(Channel lined with erosion control mats, riprap, grout bags, or gabions that descend down the steep side
slope of the cover and will allow the runoff water collected by the benches to move off of the landfill cover without creating erosion gullies.)
D. Cover Penetrations X Applicable – Non-observed □ N/A
E. Gas Collection and Treatment □ Applicable X N/A
F. Cover Drainage Layer □ Applicable X N/A
G. Detention/Sedimentation Ponds □ Applicable X N/A
H. Retaining Walls □ Applicable X N/A
I. Perimeter Ditches/Off-Site Discharge □ Applicable X N/A
VIII. VERTICAL BARRIER WALLS □ Applicable X N/A
IX. GROUNDWATER/SURFACE WATER REMEDIES X Applicable □ N/A
A. Groundwater Extraction Wells, Pumps, and Pipelines X Applicable □ N/A
1. Pumps, Wellhead Plumbing, and Electrical X Good condition □ All required wells properly operating □ Needs Maintenance □ N/A
Remarks___Observed the Arthur Step-back Repository extraction wells and monitoring system. They were observed to be in good condition at the time of the Site Inspection.
2. Extraction System Pipelines, Valves, Valve Boxes, and Other Appurtenances □ Good condition X Needs Maintenance
Remarks: RTKC reported to the Agencies that the extraction pipeline to the Arthur Step-back
Repository will need to be replaced. It does not affect the current protectiveness and should be evaluated during the next Five Year Review period.
B. Surface Water Collection Structures, Pumps, and Pipelines X Applicable □ N/A
1. Collection Structures, Pumps, and Electrical X Good condition □ Needs Maintenance
Remarks__________________________________________________________________________
_________________________________________________________________________________

C-9
C. Treatment System □ Applicable X N/A
D. Monitoring Data
1. Monitoring Data
X Is routinely submitted on time □ Is of acceptable quality
2. Monitoring data suggests:
□ Groundwater plume is effectively contained □ Contaminant concentrations are declining
Remarks: Groundwater is contained in part. A complete and thorough understanding of the plume,
including the full depth and a detailed understanding of the plume’s movement is not fully understood
at this time. MNA is the selected remedy with collection of water at seeps and springs.

E. Monitored Natural Attenuation
1. Monitoring Wells (natural attenuation remedy) □ Properly secured/locked X Functioning X Routinely Sampled X Good condition
□ All required wells located □ Needs Maintenance □ N/A
Remarks: See Appendix E for Utah’s DWQ permit compliance communique. Groundwater monitoring is performed by RTKC and reviewed by the Utah DWQ and Agencies as outlined under the active Groundwater Protection Permits, pending O&M plan for OU23 and the site wide applicable Groundwater Characterization and Monitoring Plan (GCMP).
X. OTHER REMEDIES
N/A
XI. OVERALL OBSERVATIONS
A. Implementation of the Remedy
Describe issues and observations relating to whether the remedy is effective and functioning as designed. Begin with a brief statement of what the remedy is to accomplish (i.e., to contain contaminant plume, minimize infiltration and gas emission, etc.). The selected remedies were intended in part to protect site workers from potential exposure to soils with elevated metals, require the demolition and characterization of facilities upon decommissioning to attest to the potential to support future land uses, and to manage groundwater inputs to the wetland habitat to reduce potential exposures to the resident avian receptors. The site inspection found remedy elements functioning, work progressing to advance the focused feasibility study for OU23 and monitoring of the Garfield Wetland progressing. No facilities were decommissioned over the past five years but there have been small scale soil management projects, which have complied with applicable site requirements. IC implementation is still in progress.
B. Adequacy of O&M
Describe issues and observations related to the implementation and scope of O&M procedures. In particular, discuss their relationship to the current and long-term protectiveness of the remedy. O&M is adequate, although formal plans are still pending for operational soils and the pending clarifications to the selected remedy for OU22 and OU23.

C-10
C. Early Indicators of Potential Remedy Problems
Describe issues and observations such as unexpected changes in the cost or scope of O&M or a high frequency of unscheduled repairs, that suggest that the protectiveness of the remedy may be compromised in the future. None
D. Opportunities for Optimization
Describe possible opportunities for optimization in monitoring tasks or the operation of the remedy. RTKC continues to study its pilot treatment plant addressing selenium in groundwater collected at the
Kessler Springs to adjust to bio treatment technology to increase efficiency. The pilot study was implemented by RTKC is not a required remedy element but will be evaluated to for use as a groundwater management tool in the future.

Appendix D
Site Inspection Photos

SITE INSPECTION PHOTOS OUs 8, 13, 14, 15, 19, 22, and 23
Operable Unit 8 – Wastewater Treatment Plant and Sludge Ponds

Photo 1 – Western extent of Pond C. Note the patch of Phragmites (arrow). Localized groundwater is fairly shallow, day-
lighting in seeps located throughout OU8 and OU22.

Photo 2 – Eastern extent of Pond C. Note some revegetation and gravelly consistency of side slope soils.

Photo 3 – View of Pond C from the northwestern boundary looking toward the southeast. Note the revegetation and the
gravelly slopes (arrow).

Photo 4 – View of the WWTP Footprint. The area is currently used by RTKC for staging for construction in the North
Zone. Pond B can be seen in the background (arrow).

OU13 Smelter and Support Facilities

Photo 5 – The RTKC Outokumpu Smelter Facility from the Bonneville Lake Shoreline Bench and saddle adjacent to
Black Rock Canyon. RTKC’s efforts to revegetate the canyons in the air shed of the smelter have been ongoing (both
actively and passively) since the mid-1980s.

Photo 6 – Areas of the canyons (OU19) have been impacted from historic smelter fallout (OU13). The main
contaminations of concern are lead and arsenic. This photo shows the impacts (black staining present on boulders and
ground).

Photo 7 – The western extent of the Smelter facility includes the footprint of the suspected Black Rock Tailings Pond (red
outline), Slag Pot Cooling Area, Slag Mill, West Process Water Ponds, and the Japanese Springs area (Pond 10 of OU22)
[orange arrow]. Pond 9D of the North Zone Wetlands and the Great Salt Lake Marina and Shoreline can be seen in the
background.

Photo 8 – Pictured is the western extent of the suspected Black Rock Tailings Pond (red outline). The location is
suspected to be the historic footprint of the Tailings Pond as described in the 2005 Oquirrh Mountain Mining document.

Photo 9 – Pictured is the Smelter Landfill located south of the Smelter Facility. The Smelter Landfill is used by RTKC for
municipal solid waste and construction waste. Wastes are sampled prior to deposition into landfill.

Photo 10 – Located approximately 0.4 miles from the base of the Smelter Smokestack is the Smelter Reservoir (arrow)
used for water storage (held for processing, fire suppression, etc.). The Reservoir is comprised of three lined cells; water
held is not impacted from mineral processing operations.

OU14 – Refinery

Photo 11 – View of the western extent of the Refinery (Tank House). RTKC reported some superficial damage to the
Refinery Building after the 2020 Magna Earthquake. Reportedly, maintenance to the exterior of the Refinery building has
occurred and will continue to manage the damage to the buildings.

Photo 12 – View of the basement under the Tank House of the Refinery. The basement is a reinforced concrete floor with
an epoxy coating to prevent the release of spills from the electrolytic basin ducts. Note the blue staining on the wall with a
path along the flooring.

Photo 13 – Several areas of staining were noted throughout the basement area.

Photo 14 – Large crack in the flooring was noted in the basement area (white outline). Blue Electrolyte staining was
observed around the crack (red arrows).

Photo 15 – Pictured is the capped Old Precious Metals Building.

Photo 16 – The approximate area of the building footprint of the Old Precious Metals Building. The area is located behind
locked fencing limiting access to the area. Little to no disturbances to the ground surface were observed at the time of the
Site Inspection.

Photo 17 – View of the capped EP Repository. The capped EP Repository is well-vegetated. RTKC frequently
monitors for the presence of burrowing animals in the capped area. There was no evidence observed at the time of the
Site Inspection that animals have been using this area. The ground was undisturbed and appeared well-vegetated.
OU15 Mills, Tailings Ponds, Power Plant
Bonneville Crushing and Grinding Facility Footprint

Photo 18 – Pictured is the remediated/reclaimed footprint of the Bonneville Crushing and Grinding Facility footprint.
Since the last review, the vegetation growth has increased through here. There are still areas of gravel (arrows). Soils are
stable and not mobilizing.

Photo 19 – This photo shows the limited revegetation success.

Photo 20 – Pictured is the Utah Power Plant and associated water reservoirs and the rail line that is currently in use.
Demolition to the UPP began in 2018 (see the Site Inspection, OU15 Section in the report for more detail). The tailings
impoundment can be seen in the background, and the Great Salt Lake can be seen behind that.

Photo 21 – Pictured is the signage for the Arthur Step-Back Repository. Signage notes that only preapproved soils are
allowed to the enter the repository. Vehicular access to the repository is restricted via a locked gate.

Photo 22 – View of the western capped end of the repository. The capped portion was observed to have pooled water
present. No visible tears or rips were observed at the time of the Site Inspection.

Photo 23 – Pictured are temporarily placed soils for disposal sitting atop the HDPE liner.

Photo 24 – View of the South Tailings Impoundment. Pictured is the Revegetation Pilot Study (outline). Various species
of plants have been planted along the STI and the success of growth is monitored. There has been limited success at
revegetating the STI.

Photo 25 – View of the STI from the boundary between South Tailings and North Tailings.

Photo 26 – View of the North Tailings Impoundment

Photo 27 – Pictured is the Tailings Decant Barge platform located on the water off the central portion of the NTI’s
southern embankment.

Photo 28 – Pictured is the equipment located on the Tailings Decant Barge.

Photo 29 – Pictured is the West Cyclone Station.

Photo 30 – View of the western slope of the STI. Note the sparse vegetation.

OU19 – Smelter Fallout (Canyons Downwind of the Smelter)

Photo 31 – View of a portion of Little Valley. Historically, the canyons downwind of the Smelter were impacted by
Smelter fallout, causing sparse vegetation growth. Note the sparse vegetation in the foreground of the photo.

Photo 32 – View towards upper Little Valley. Note the corrals located in the photo (arrows). Little Valley is utilized by
local cattle drivers and is used periodically for grazing.

Photo 33 – View of Black Rock Canyon. Black Rock Canyon is the canyon to the west of the Smelter.

Photo 34 – View of the southern extent of the Black Rock Gravel Pit, which is operated under a land lease (lessor –
RTKC, lessee – Geneva Rock).

Phot 35 – View of the northern extent of the Black Rock Gravel Pit.

Photo 36 – View of the gravel operations equipment located at the base of the gravel mine.

Photo 37 – Gravel piles ready for export off of the site.

Photo 38 – View of the temporary repository to the west of the active gravel pit operations. The top 6”-1’ of topsoil was
removed from the gravel mine area and deposited here. Revegetation occurred in 2022. Note soil and gravel present
intermixed with vegetation.

Photo 39 – Signage located adjacent to the repository. The repository is located behind locked fencing within private
property and access to the public is well limited.

Photo 40 – View of Kessler Canyon, south of the Smelter. Note the limited vegetation and sparse tree line.

OU22 & OU23 – Great Salt Lake, Shoreline, and Wetlands and Northend Groundwater

Photo 41 – View of the eastern extent of the North Zone Wetlands. This photo is depicting the access road that traverses
Pond 7A. Access drives within OU22 were built up using slag.

Photo 42 – View of Pond 8. Pond 8 is the terminal basin of the North Zone Wetlands for surface water day-lighting from along the range front and from
groundwater in the shallow and principal aquifers underlying the North Zone Facilities (OU23). The basin has water year round and presents diverse habitat from
open water, shoreline, and upland habitat for a diverse community of waterfowl, shoreline, and passerine birds. Selenium concentrations vary greatly in the
samples collected to date of water, sediment, and macro-invertebrate tissue as well as in whole egg samples. This variability is both temporal (varying from year
to year) to geographical (varying from established sampling locations along the shoreline). No annual patterns have been able to be determined to date.

Photo 43 – View of Pond 8 from the “Black Beach”. The “Black Beach” was created by laying slag down in OU22.

Photo 44 – Standing on a berm looking towards Pond 9A.

Photo 44 – View of invasive Phragmites that overtake several wetland areas within OU22.

Appendix E
State Permit Review

Mazie Cox <[e-mail]>
North Zone Five Year Review
Mazie Cox <[e-mail]>Thu, Feb 1, 2024 at 8:35 AM
To: Hayley Shaffer <[e-mail]>
Hello Hayley,
I am working to complete the CERCLA Agencies’ Third Five Year Review for the Kennecott North Zone due in August 2024. Thisreview covers the Operable Units
· OU8 Waste Water Treatment Plant and Sludge Ponds
· OU13 Smelter and Acid Plants
· OU14 Refinery· OU15 Mills and Tailings Pond
· OU19 Smelter Fallout
· OU22 Great Salt Lake, Shoreline Wetlands
· OU23 North End Groundwater

In a number of these OUs there are operating facilities which require compliance with a Salt Lake County issued operating permit
(landfills and other permitting facilities) located at the Kennecott North Zone. I am seeking an acknowledgement from the Salt Lake
County Health Department in divisions that have issued these permits that since August 2019, Kennecott has maintained compliancewith the permit requirements and if issues arose, what was done to correct the issue and has Kennecott returned to a state of
compliance.

If there are individuals you are aware of that would be better to answer these questions (permitting authorities), please feel free toforward this email to them or let me know and I can forward this their way. I am including an example of a response from years past
for guidance. Please let me know if you have any questions regarding this request.

Best,
Mazie Cox
Environmental Scientist | Superfund NPL
P: [phone]
Hours: Monday - Thursday 8:00 - 5:00, Friday 7:30 -
12:00
environmentalresponse.utah.gov
Emails to and from this email address may be considered public records and thus subject to Utah GRAMA
requirements.
Permiting Facilities Response Examples.pdf
304K
Mazie Cox <[e-mail]>
North Zone Five Year Review
Neil Opperman <[e-mail]>Tue, Feb 6, 2024 at 2:21 PM
To: "[e-mail]" <[e-mail]>
Cc: Hayley Shaffer <[e-mail]>
Hello Mazie!

Hayley asked me to reach out to you with a response about the landfill permits that Kennecott holds with the Salt Lake County Health Department.
Below are the Salt Lake County Health Department permits issued for Kennecott landfills and any comments/issues that were documented during the
inspections since August 2019:

Landfill Establishment #Location Inspection Results
Est #35-0011803 Bingham Canyon Tire Monofill (located by Bingham Canyon
Mine)
No violations observed
Est #35-0011806 Concrete Monofill (located above Smelter)No violations observed
Est #35-0011807 Smelter Landfill (located above Smelter)No violations observed
Est #35-0011805 Tailing Impoundment Landfill (located in/by Tailings Pond #1)No violations observed

No formal enforcement action was taken against Kennecott during the time of August 2019 – Current. Kennecott has maintained a good compliance
history for their landfill permits that they hold with the Salt Lake County Health Department over the last 5 years. Additionally, there has been no
complaints received by the Department with regards to any of the 4 landfill permits that Kennecott holds. Based upon the multiple inspections
conducted during this time and no complaints received during the same time frame, it appears that Kennecott is in compliance with Salt Lake County
Health Regulation #1 which governs landfills and waste processing facilities within the county.

Please note that the only permitted landfill that likely does not fall in the “North Zone” is the Bingham Canyon Tire Monofill seeing how it is on the
southern end by the Bingham Canyon open pit mine. I included it just in case it is needed as well.

Hope this helps!

Take care,

Neil Opperman, MS, LEHS
Environmental Health Scientist
W Q H W B
O 385-468-3862
M 385-226-0481
[e-mail]
SaltLakeHealth.org

From: Mazie Cox <[e-mail]>
Sent: Thursday, February 1, 2024 8:36 AM
To: Hayley Shaffer <[e-mail]>
Subject: North Zone Five Year Review

Hello Hayley,

I am working to complete the CERCLA Agencies’ Third Five Year Review for the Kennecott North Zone due in August 2024. This review covers theOperable Units

· OU8 Waste Water Treatment Plant and Sludge Ponds
· OU13 Smelter and Acid Plants
· OU14 Refinery
· OU15 Mills and Tailings Pond
· OU19 Smelter Fallout
· OU22 Great Salt Lake, Shoreline Wetlands
· OU23 North End Groundwater

In a number of these OUs there are operating facilities which require compliance with a Salt Lake County issued operating permit (landfills and other
permitting facilities) located at the Kennecott North Zone. I am seeking an acknowledgement from the Salt Lake County Health Department in divisionsthat have issued these permits that since August 2019, Kennecott has maintained compliance with the permit requirements and if issues arose, whatwas done to correct the issue and has Kennecott returned to a state of compliance.

If there are individuals you are aware of that would be better to answer these questions (permitting authorities), please feel free to forward this email tothem or let me know and I can forward this their way. I am including an example of a response from years past for guidance. Please let me know if you
have any questions regarding this request.

Best,

Mazie Cox
Environmental Scientist | Superfund NPL
P: [phone]
Hours: Monday - Thursday 8:00 - 5:00, Friday 7:30 -
12:00
environmentalresponse.utah.gov
Emails to and from this email address may be considered public records and thus subject to Utah GRAMA
requirements.

Mazie Cox <[e-mail]>
Kennecott North Zone Five Year Review - August 2024
Mazie Cox <[e-mail]>Thu, Feb 1, 2024 at 8:31 AM
To: David Jamison <[e-mail]>, Jennifer Berjikian <[e-mail]>, Kim Coburn-Groenewold <[e-mail]>
Good morning,

I am working to complete the CERCLA Agencies’ Third Five Year Review for the Kenneco North Zone due in August 2024. This review covers theOperable Units
· OU8 Waste Water Treatment Plant and Sludge Ponds· OU13 Smelter and Acid Plants· OU14 Refinery
· OU15 Mills and Tailings Pond· OU19 Smelter Fallout· OU22 Great Salt Lake, Shoreline Wetlands
· OU23 North End Groundwater

In a number of these OUs there are operang facilies which require compliance with a State of Utah issued operang permit. I am seeking anacknowledgement from the State agencies which have issued these permits that since August 2019, Kenneco has maintained compliance withthe permit requirements and if issues arose, what was done to correct the issue and has Kenneco returned to a state of compliance.

If there are individuals you are aware of that would be beer to answer these quesons, please feel free to forward this email to them or let meknow and I can forward this their way. I am including an example of a couple of responses from years past for guidance. Please let me know if you
have any quesons regarding this request.

Best,
Mazie Cox
Environmental Scientist | Superfund NPL
P: [phone]
Hours: Monday - Thursday 8:00 - 5:00, Friday 7:30 -
12:00
environmentalresponse.utah.gov
Emails to and from this email address may be considered public records and thus subject to Utah GRAMA
requirements.
Permiting Facilities Response Examples.pdf
304K
Mazie Cox <[e-mail]>
Kennecott North Zone Five Year Review - August 2024
Jennifer Berjikian <[e-mail]>Mon, Apr 1, 2024 at 9:07 AM
To: Mazie Cox <[e-mail]>
Hi Mazie,
Attached is information regarding Kennecott violations for the last five years. The most recent formal enforcement action that I could find was from
2018, so just outside the 5-year window. Let me know if there's anything else you need.
Kennecott UPDES Violation Info
Thanks!
Jen
Jennifer Berjikian
Environmental Scientist | Individual Permit Section
M: [phone]
waterquality.utah.gov
Emails to and from this email address may be considered public records and thus subject to Utah GRAMA
requirements.
[Quoted text hidden]
Effluent exceedances
Outfall Parameter Report Monitoring period Effluent limit Value Percent Violation
Outfall 010 Zinc, total [as Zn]MX MO AV 3/31/2020 0.323 0.481 49
Outfall 012 Solids, total suspended DAILY MX 3/31/2019 30 32 7
Outfall 012 Solids, total suspended DAILY MX 4/30/2019 30 33 10
Outfall 012 Solids, total suspended DAILY MX 12/31/2019 30 48 60
Outfall 012 Solids, total suspended DAILY MX 4/30/2020 30 35 17
Outfall 012 Solids, total suspended DAILY MX 10/31/2020 30 32 7
Outfall 012 Solids, total suspended DAILY MX 2/28/2021 30 47 57
Outfall 012 Solids, total suspended DAILY MX 12/31/2021 30 35 17
Outfall 012 Solids, total suspended MX MO AV 2/28/2022 20 99 395
Outfall 012 Solids, total suspended DAILY MX 2/28/2022 30 271 803
Outfall 012 Cyanide, total [as CN]MX MO AV 1/31/2022 0.1 0.174 74
Non-reporting violations
Parameter Outfall Monitoring Period Date Received Days Late Discharge?
pH Outfall 002 3/31/2019 8/13/2019 107 No Discharge
pH Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Solids, total suspended Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Solids, total suspended Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Oil & Grease Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Cyanide, total [as CN]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Cyanide, total [as CN]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Arsenic, total [as As]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Arsenic, total [as As]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Cadmium, total [as Cd]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Cadmium, total [as Cd]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Copper, total [as Cu]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Copper, total [as Cu]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Lead, total [as Pb]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Lead, total [as Pb]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Zinc, total [as Zn]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Zinc, total [as Zn]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Selenium, total [as Se]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Selenium, total [as Se]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Floating solids, waste or visible
foam-visual Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Flow, in conduit or thru treatment
plant Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Solids, total dissolved Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Solids, total dissolved Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Mercury, total [as Hg]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Mercury, total [as Hg]Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Oil and grease visual Outfall 002 3/31/2019 8/13/2019 107 No Discharge
Oil and grease visual Outfall 011 3/31/2019 8/13/2019 107 ---
Selenium, total [as Se]Outfall 012 10/31/2020 4/27/2021 149 ---
Selenium, total [as Se]Outfall 012 11/30/2020 4/27/2021 119 ---
Selenium, total [as Se]Outfall 012 12/31/2020 4/27/2021 88 ---
Mazie Cox <[e-mail]>
Kennecott North Zone Five Year Review - August 2024
David Jamison <[e-mail]>Mon, Apr 22, 2024 at 10:08 AM
To: Mazie Cox <[e-mail]>
Cc: Jennifer Berjikian <[e-mail]>
Maize,
My apologies for this taking me so long to get to. Attached are my comments on the current compliance of the north end permits and any issues of
gaps in coverage of the permit that I am aware of. Let me know if you have any questions or need anything clarified.
Thanks,
David M. Jamison
Environmental Scientist III | Division of Water Quality -
Individual Permitting Section
P: [phone]
waterquality.utah.gov
Emails to and from this email address may be considered public records and thus subject to Utah GRAMA
requirements
On Wed, Mar 27, 2024 at 3:27 PM Mazie Cox <[e-mail]> wrote:
[Quoted text hidden]
North end 5-year review comments.docx
14K
Tailings Impoundment UGW350011
The tailings permit has been in renewal for approximately two years. The renewal package was
submitted in time for administrative extension of the permit allowing for the long renewal period. The
renewal has factored in the potential east tailings expansion project, though it is not certain that the
expansion will be included in the permit immediately following this renewal period. The current
compliance status of tailings is mixed. Most of the wells are in compliance with their current compliance
limits. The following wells are out of compliance:
NEL532B has exceeded the TDS limit for the well since July of 2021 with a brief drop back into
compliance in the 4th quarter of 2022 before continuing to be out of compliance through today.
NET1386B has exceeded its compliance limit for sulfate since January of 2021.
NEL1382C has exceeded the compliance limit for pH since January 2021 with a brief period of
compliance for the 2nd and 3rd quarters of 2023 before entering out of compliance status again through
the present.
NET646A has exceeded the arsenic compliance limit since June of 2021.

Kennecott Utah Copper has submitted a Source Area Assessment for the exceedances in the above
noted compliance wells around the tailings impoundment. The report is currently under review before
being sent back to KUC with comments. In addition to the exceedances and source area assessment
additional information has been found and reviewed as part of the permit renewal process which has
raised some possible concerns for the integrity of the impoundment. The fundamental concept of the
tailings impoundment being constructed on top of the natural Bonneville clay with a drainage blanket
under the north zone berm wall with the toe ditch to collect water, is that it is discharge minimizing. This
discharge minimizing design was intended to limit or prevent tailings water from entering the shallow
groundwater without a minimum of several feet of clay to restrict its flow and preferential pathways to
direct tailings water back into the process water circuit through the clarification canal.
A review of the Kennecott North Tailings Impoundment Annual Report for 2022 to the Utah Department
of Natural Resources, Division of Water Rights was completed for an assessment of the physical changes
to the impoundment since construction. The report includes a discussion of settlement plates and
drilling to verify the elevation of the drainage blanket feature located at the base of the north
impoundment berm wall. Figure B.07 and the discussion on page 10 of the report indicate a possible
settlement of the berm of 20 feet. If it is confirmed that 20 feet of settlement have occurred at the berm
wall and the drainage blanket is now located at a depth 20 feet lower than it was initially placed, it
would indicate that the former discharge minimization design would now be potentially responsible for
creating a pathway for tailings water and tailings to have direct interactions with the shallow
groundwater immediately underlying and adjoining the tailings impoundment. This also has potential
implications for operable unit 22 surrounding the impoundment and the plume associated with
operable unit 23 west of the tailings impoundment.
DWQ currently has meetings planned to discuss the potential east tailings expansion and the possible
issues with the tailings design and BAT before the end of April 2024. DWQ will keep DERR and EPA up
dated on developments with the permit as it pertains to our agreement to use the permits to prevent
impacts to CERCLA Operable Units from active operations.

Smelter UGW350008
All wells in compliance, BAT intact, CAP for acid spill and maintenance (pumping) of acid collection
trench is in compliance.

Magna Reservoir UGW350015
All wells in compliance. Several leaks detected over the last permit term. All were repaired and
notifications were made appropriately. A construction permit was issued for the alteration of the outlet
from one of the ponds.
Appendix F
Public Notice & Interview Forms

North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone
EPA ID: UTD070926811
March 5, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox,
UDEQ-DERR, and Missy Haniewicz, US EPA Region
8.
Person Contacted
Name: Teresa Cockayne, Principal Advisor –
Remediation, and Erka Naran, Principal Advisor
Water Quality.
Organization: Rio Tinto Kennecott
Address:
Rio Tinto Kennecott
4700 Daybreak Parkway
South Jordan, Utah 84009
Phone: [phone]

1. Is your organization/department aware of the Kennecott North Zone Superfund site and the
actions underway to address environmental contamination? Teresa Cockayne, principal
advisor for remediation at Kennecott and the regulatory partner with DERR and EPA, oversees
the soil and groundwater remediation on-site. Ms. Cockayne stated that she has been with
Kennecott since 2012, and has been in her current role for three years.

Erdenebayar (Erka) Naran said he joined Kennecott (Utah) in 2022, after leaving a Rio Tinto
project in Mongolia, Republic of China, and has been with Rio Tinto for 11 years. Mr. Naran said
his background is in water treatment engineering and supports the Rio Tinto remediation team
at the North Zone site.

2. What’s your overall impression (your general sentiment) of the actions performed at the
Kennecott North Zone Superfund Site? Ms. Cockayne said that a portion of the North Zone site
is still operational and the smelter, refinery, and tailings impoundment, are the major
operations. The non-operational areas include the wetlands, groundwater, and portions of OU
15. Ms. Cockayne and her team have worked to begin the demolition of the Utah Power Plant
(UPP) in the last five years. The demolition of the UPP has been a big project, and Ms. Cockayne
states that RTK has voluntarily cleaned up this site pre-closure. The UPP project started in 2019
and continues through today. Ms. Cockayne stated that the UPP structures still exist with plans
to remove any hazardous materials and demo the building. Ms. Cockayne stated that once the
building is demoed, RTK will conduct soil remediation through the CERCLA process.

Ms. Cockayne stated that for Operable Units (OU) in active operations, including the Smelter
and the Refinery, there are management plans in place like the soil management plan. If RTK
does any ground disturbances on site, Ms. Cockayne’s team will test the soils to ensure that
there is not any contamination encountered. Ms. Cockayne stated that there are work plans also
for OU22, Great Salt Lake Wetlands, and OU23, North End Groundwater.

Ms. Cockayne stated that RTK has been monitoring these sites since the early 2000s. Ms.
Cockayne stated that since 2003, controls have been in place, and there are regular inspections
on the rest of the sites. Mr. Naran stated that Kennecott is moving cleanup efforts forward and
how to progress. Mr. Naran stated “We have a lot of obligations trying to solve these projects
and do the right things. We understand what happened and all of our major facilities are
permitted with a comprehensive groundwater quality network. We also make sure there's no
additional contamination from the current operation, and have a genuine interest to do the
right thing and come up with remediation solutions for these sites.”

3. Does your office conduct routine communications and/or activities (site visits, inspections,
reporting activities, participation in meetings, etc.) for the Kennecott North Zone Superfund
Site? If so, please briefly summarize the purpose and results of these communications and/or
activities over the past several years. Ms. Cockayne stated that RTK meets with DERR and EPA
(the Agencies) at least monthly to ensure that RTK is staying on track with projects and
compliance. She stated that when there are any outstanding reports or action items, RTK and
the Agencies meet to take care of them within a selected time frame to make sure that we're
hitting our milestones. Ms. Cockayne stated that RTK has an established reporting schedule with
the Agencies and has two soil management plans in place: the Waste Left in Place Plan and the
Operations Soil Management Plan. She stated that these two work plans cover the entire site
and the North Zone in particular.

Ms. Cockayne stated, “If we do any work under these plans, we submit a report to the Agencies.
With OU22, the North Zone wetlands, we have a monitoring requirement and provide a report
to the agencies as well. We also produce an annual report.”

Regarding outside stakeholders, Ms. Cockayne said, “We have communications and try to be
transparent with our external stakeholders by participating in different community meetings.
For instance, there are several meetings surrounding the Great Salt Lake or the wetlands
environment. We also submit a lot of technical reports as part of the permitting UPDES permit,
groundwater discharge permits, and monitoring data around the facilities in the North End,
that's all public.” “We conduct and address public comments and consultation”, which Ms.
Cockayne says is “a part of our community engagement”. Mr. Naran said, “There are also Water
Rights meetings and we are engaged with the communities to be transparent with what we're
doing.”

The RTK team stated that they participate with community interest groups like the Great Salt
Lake Advisory Council as there is a lot of public focus on the Great Salt Lake. Ms. Cockayne said,
“We are internally taking a look at what those risks are as the Great Salt Lake continues to shrink
and what can Kennecott potentially do to make sure that the wildlife and the habitats are
protected. We have begun altering water rights to contribute to the Great Salt Lake and
potentially help as our shorelines increase.”

4. Are you aware of any community concerns regarding the Kennecott North Zone Superfund
Site or its operation and administration? If so, please give details. Ms. Cockayne and Mr.
Naran were not aware of any specific community concerns regarding the North Zone site. Ms.
Cockayne said that with RTK’s proximity to the Great Salt Lake, there is a high concern with
Kennecott's operations. Ms. Cockayne stated that Kennecott has discharge permits and controls
in place so that no groundwater, soils, or other hazards are released into the environment. She
stated that the perimeter of the RTK property is fenced and any hazardous substances are
controlled, either through capping or placement into a repository.

Mr. Naran said “With community concerns regarding consumption and recent years of
conservation activities, we wanted to decrease our work consumption. Kennecott is involved in
providing water back to the Great Salt Lake initiating a Water Rights donation. We donated
18,000-acre feet of water to the Great Salt Lake last year. During this sensitive discussion about
the Great Salt Lake, we want to be part of that campaign to help where we can. To reduce our
water consumption, we have some water targets to decrease water consumption. Kennecott
has lots of initiatives happening internally to find benefits and a friendly approach to help. It's a
win, win campaign and so we wanted to reduce our water consumption.”

5. Over the past five years, have there been any complaints, violations, or other incidents (e.g.,
vandalism, trespassing, or emergency responses) at or related to the Kennecott North Zone
Superfund Site requiring your office to respond? If so, please give details of the events and
results of the response. Ms. Cockayne and Mr. Naran said there haven’t been any incidents or
emergency responses at the North Zone site within the last five years. Ms. Cockayne said
Kennecott is in proximity to about a million people in the Salt Lake Valley and very close to the
metropolitan area. She stated, “Of course, RTK is going to have some vandalism and some
trespassing from time to time. Any business would address these items and strive to keep
everybody safe, and that RTK does have controls in place.”

Ms. Cockayne said the facilities themselves are under security, so there isn’t any public access.
Kennecott takes care of the issue right away if fences are breached and repairs the fence as
quickly as possible and puts up signage to let people know that they are on Kennecott property.
“So, we might see some breaches in a fence every now and then, or a few trespassers, but
again, those items are addressed and we have security in place. So we try to raise public
awareness that there is potential for these hazards and to put these controls in place to keep
everybody safe,” Ms. Cockayne said.

6. Do you feel well informed about the site’s activities and progress over the last five years? Do
you know how to contact the Environmental Protection Agency if you have questions or
concerns about the Kennecott North Zone Superfund Site? Ms. Cockayne said they have seen
some positive changes in regulator relations with DERR and EPA. There have been some shifts in
project management and Ms. Cockayne feels like it's been a positive change. “We have a really
good relationship with DERR and EPA to not only be transparent but also make some progress
on the protectiveness of the site,” said Ms. Cockayne. She also said she could call either DERR or
EPA at any time to discuss matters.

Ms. Cockayne said, “Honestly, there is always a worry when people transition to different
positions. We have had a lot of movement on our internal teams and with some new people on
the team and have had some people leave the team. With our agencies, we've had a transition
and still have that body of knowledge. Our new regulators at DERR and EPA have really stepped
up with their site knowledge and you would expect a gap or delay in projects, but I haven't seen
that at all. It's been a very positive transition.”

7. Over the past five years, have there been any changes in your department’s policies or
regulations that might impact the Superfund Site from a perspective of land use, water rights,
redevelopment, and site management? Ms. Cockayne said there have been some changes in
EPA guidance and that RTK is adapting to those changes and understanding what the guidance
says. Ms. Cockayne stated that the guidance documents are centered primarily around soil
management plans, sampling analysis plans, and how they are submitted. “It's been a step in
the right direction and helped us think more thoroughly about our sampling analysis plans.
Following the data quality objectives process or EPA crosswalk guidance hasn't been a negative
thing, it's just been adapting to that change,” said Ms. Cockayne.

8. Over the past five years, have there been any changes in land use surrounding the Kennecott
North Zone Superfund Site? Are you aware of potential future changes in land use? Ms.
Cockayne said the demolition of the power plant will take a couple more years to complete and
remediation and reclamation of that site. She said that she doesn’t anticipate a land use change
at this time. Kennecott will retain that land until closure; so for now, it will remain an industrial
site.

“What the future holds I’m not quite sure. We have encroaching development all over the Salt
Lake Valley and so we have seen some changes in land use. No land transactions on the North
End of the property, but it's mostly been in our nonoperational buffer lands,” stated Ms.
Cockayne.

9. Do you have any comments, suggestions, or recommendations regarding the site’s
management or operation (institutional controls)? If so, what types of future problems do
you think (1) could occur; or (2) would concern you and/or your department? Ms. Cockayne
said, “We are working with the Agencies on the revised remedies for Operable Units 22 and 23.
So with this, will come new work plans and operations and maintenance plans to, hopefully,
provide some positive changes to the sites. We have other plans and permits in place where we
are ensuring that these remedy objectives are being obtained. It is taking some time and we
would like the progress to move and a little bit faster because we have been working on these
plans for quite some time. But with the changing in roles, I see it as a positive change. It
provides a new set of eyes on these plans and also provides a new interest in completion of
these plans.”

Mr. Naran said, “The challenge has been the timing of completion of these plans and the
communications with the agencies and our environmental consultants, we’re still working to get
these plans in place. Kennecott is doing what we can do for the given situation and an
opportunity. Rio Tinto is a global company and we don't do shortcuts and want to do the right
thing and complete the remediation. The Rio Tinto team is doing and trying to make progress in
the right direction. It's time to accelerate the process, all the plans are submitted and we're
ready to engage with you for progress and moving things forward.”

North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone
EPA ID: UTD070926811
March 15, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox,
UDEQ-DERR, and Maggie Ogden and Missy
Haniewicz, US EPA Region 8.
Person Contacted
Names:
Heather Dove, President, Great Salt Lake Audubon,
Emily Hamel, Ecologist, National Audubon -Saline
Lakes Program
Heidi Hoven, National Audubon’s Gillmor Sanctuary &
Lee Creek Sanctuary,
Max Malmquist, National Audubon’s Saline Lakes,
Dr. Brian Moench, President, Utah Physicians for a
Healthy Environment
Deeda Seed, Center for Biological Diversity
Organizations:
The Great Salt Lake Audubon and Associates

Address:
Great Salt Lake Audubon
P.O. Box 520867 Salt Lake City, Utah 84152-0867
Phone: [phone]

1. Is your organization/department aware of the Kennecott North Zone Superfund site and the actions
underway to address environmental contamination? None of the Group was aware this area was a
Superfund Site. The Audubon members said they have a significant presence in the Lee Creek Natural
Area and the Great Salt Lake State Park, participating in cleanups and conservation efforts. The Audubon
members said they do have people out there and that the Gilmore Sanctuary is a National Audubon
property and the Lee Creek natural area is also owned and managed by Audubon. The Audubon has a
heavy presence both from the national and the local chapters in this area of the North Kennecott Zone.
Environmental groups are active in the area, conducting surveys and monitoring bird populations. Dr.
Brian Mensch, President of Utah Physicians for a Healthy Environment, expressed concern about the
human health consequences of activities in the area.

The Five-Year Review report process was explained to the group by the EPA and UDEQ. It was explained
that the EPA is required to conduct a five-year review of superfund sites, involving site visits, record
examination, stakeholder outreach, and protective statements for the report which will be completed and
made available to the public by the end of the year. A detailed overview of the Kennecott North Zone was
provided by the EPA and UDEQ, including operable units (OUs), contaminants of concern (arsenic, lead,
selenium), and the status of various cleanup and management efforts. The discussion included the history
of the site, the regulatory framework, and the ongoing and future remediation efforts.

2. What’s your overall impression (your general sentiment) of the actions performed at the Kennecott
North Zone Superfund Site? The Audubon Group said initial concerns were raised about the impact of the
site on the environment. Particularly with the Great Salt Lake, wildlife, and human health, including the
effects of dust from tailings and the proximity to populated areas.

Dr. Brian Moench expressed concerns about the human health consequences of activities in the area and
the organization's eagerness to understand and mitigate potential impacts along the Salt Lake Valley and
the rest of the Wasatch Front.

Are you aware of any community concerns regarding the Kennecott North Zone Superfund Site or its
operation and administration? If so, please give details. The Group had environmental and community
concerns regarding the North Kennecott Superfund Site area. There was a discussion about the
importance of the area for bird populations, including nesting snowy plovers, and the impact of
contaminants on wildlife. The Audubon said the need for more focus on food webs and the implications of
contaminant flow into the Great Salt Lake ecosystem requires active attention and response. The Group
said the importance of considering the cumulative effects of contaminants on wildlife and human health
should be an important consideration from Kennecott and regulators. Concerns were raised about the public's lack of awareness regarding the site's activities and the potential
health impacts on nearby communities, including children. Community concerns about dust from tailings
and potential health impacts on nearby communities were expressed. There are communities very close
by, possibly breathing in the stuff that's blowing off the tailings and evaporating from the ponds.
Especially during aggressive dust storms driving along the highway, both the dust and the tailings near the
lake kind of meet in the middle.

The Audubon said they wanted to pass along a text from Liz Waite, a former Utah House legislator and
West Valley City resident regarding the Kennecott North Zone. Ms. Waite said, “Every time I drive past the
site location I reflect on the immense area and probable impacts, observe the activities, and note the
miles of roads, trucks, and huge blooms of water sprayed over the areas,” Ms. Waite is impressed by the
size of the site as said “I realize the relative dimensions of the big trucks and those water blooms spraying
out on dirt, especially on days of notable drought conditions.” Ms. Waite said, “the bottom line for me
always is that my downwind neighborhood population is 26% school-aged kids, plus
additional percentages for their younger siblings and young parents”.

3. Do you feel well informed about the site’s activities and progress over the last five years? Do you know how to contact the Environmental Protection Agency if you have questions or concerns about the
Kennecott North Zone Superfund Site? The Group said they don't think the public is very informed about
this site in general. The Audubon said they want to talk to the Great Salt Lake Collaborative and ask them
to do some articles about North Kennecott because they think that “everybody needs to know about
this”. The Audubon Group said the general public doesn't know and they weren’t aware of the detail and
wonder what's going on over there. The Group said, “We're so close, right across the street. I think
everybody knows the landmark, the smokestack tower, but do they know the extent of the cleanup
work?”

4. Over the past five years, have there been any changes in your department’s policies or regulations that might impact the Superfund Site from a perspective of land use, water rights, redevelopment, and site
management? The Group couldn’t think of any policy changes over the last five years and that most of
the legislative sessions have focused on mineral extraction and conservation of the Great Salt Lake.
However, since the last Five-Year Review, the Utah Legislature in 2021, helped Kennecott to transfer their water right and donate 21,000 acre-feet of water to Farmington Bay for next 10 years. Max Malmquist,
Engagement Manager for National Audubon’s Saline Lakes, said he is updating the agreement with
Kennecott this year to extend the agreement.

Dr. Moench said regarding land management, “Kennecott is one of the main landowners in the inland
port area. Those of us in the environmental community who have been actively opposing the inland port
for the last six years have been focused on Kennecott as a landowner and, therefore, a contributor to
what we see as a real problem in terms of fostering development there that will be bad for the lake on
multiple fronts.”

5. Do you have any comments, suggestions, or recommendations regarding the site’s management or
operation (institutional controls)? If so, what types of future problems do you think (1) could occur; or
(2) would concern you and/or your department? Participants expressed a desire for more transparency and community engagement from Kennecott and that there is a need for greater public awareness of the
site's activities and impact. There was acknowledgment from the Group of the unique challenges posed
by the site's proximity to the Great Salt Lake and the importance of considering the ecological and human
health impacts in the context of the lake's declining levels. The Audubon Group's suggestions for future
site management should include a shift towards a more rigorous food web focus in contamination studies
and the possibility of Kennecott creating conservation easements in the inland port area.

Dr. Moench said a number of studies have shown that communities that live in close proximity to these
huge mining operations suffer as much human health and ecological damage as is actually greater than
the economic value of what these mines are extracting. “Now, given that we're not asking to shut
down Kennecott, but if part of the point is to judge public perception, I think Kennecott needs to
understand that that sort of impact on the community and even more so as the Great Salt Lake tends to
shrivel up. A good portion of the population can identify that much of the heavy metal contamination of
the Great Salt Lake and therefore the dust that we all fear will be blown across the Wasatch Front as the
lake continues to shrivel originated from Kennecott's operations. So, we are going to try and make a more
public push to have Kennecott be a better citizen. And an example would be instead of trying to maximize
the dollar value of your land holdings in the inland port area, turn it into a conservation easement,” said
Dr. Moench.
Some next steps were asked of participants on the call and provided contact information for further
discussion and involvement. The possibility of adding National Audubon representatives to the Technical
Review Committee was discussed. Also requested was the possibility of scheduling additional meetings
focused on specific questions and concerns. After the Five-Year Review report is finished, it is to be
shared with all participants when it becomes public.
North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone EPA ID: UTD070926811
February 27, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox, UDEQ-
DERR, and Maggie Ogden and Missy Haniewicz, US
EPA Region 8.
Person Contacted
Name: Marisa Weinberg, Great Salt Lake Coordinator Organization: Division of Forestry, Fire & State Lands
Address:
Utah Department of Natural Resources -Division of
Forestry, Fire & State Lands
1594 W North Temple St #3520, Salt Lake City, UT
84116
Phone: [phone]

1. Is your organization/department aware of the Kennecott North Zone Superfund site and the actions
underway to address environmental contamination? Marisa Weinberg is the Great Salt Lake Coordinator
for the Division of Forestry, Fire, and State Lands (FFSL) within the Utah Department of Natural Resources
(DNR). FFSL is responsible for forest health, responding to wildland fires, and managing sovereign lands in
Utah. Ms. Weinberg said she has been with the Division for five years and working on Great Salt Lake
issues for most of that time which includes involvement regarding the North Kennecott Superfund Site.

2. What’s your overall impression (your general sentiment) of the actions performed at the Kennecott
North Zone Superfund Site? Ms. Weinberg said, “The bed of the Great Salt Lake is where FFSL’s
management and jurisdiction begin. Due to the North Kennecott Superfund Site's close proximity to the
south shore (the meander line), it’s in FFSL's interest to understand any North Kennecott connections
ecologically and hydrologically that may impact the Great Salt Lake. This includes any related groundwater
conditions or affected bird populations near the Superfund site.” Ms. Weinberg said, “How everything
from vegetation to sediments, and weather patterns are connected in abiotic and biotic ways where it
would affect our jurisdiction. Also, lake bed dust and FFSL Management land areas not submerged are an
increasing concern. Preventing any contribution of toxic metals (arsenic or selenium) from the North
Kennecott site would be of concern.”

3. Does your office conduct routine communications and/or activities (site visits, inspections, reporting
activities, participation in meetings, etc.) for the Kennecott North Zone Superfund Site? If so, please
briefly summarize the purpose and results of these communications and/or activities over the past
several years. Ms. Weinberg said the FFSL does participate with the North Kennecott Technical Review
Committee Meetings for site developments and information but does not have any specific Division
reporting responsibilities for this area at this time. Ms. Weinberg said, “Their office is not comprised of
engineers or science-based staff which is why they rely upon our partners to help us best inform the
science hydrologically to design their management accordingly.” Ms. Weinberg said, “They do not have
any regular meetings with Kennecott directly. If there has been cause to meet, Kennecott has been more
than willing to meet with us. An example would be some site planning with Black Rock and an entrance
road into the area.” Ms. Weinberg said, “From access to providing roadbase, Kennecott has been a good
partner getting work done at Black Rock.”
4. Are you aware of any community concerns regarding the Kennecott North Zone Superfund Site or its
operation and administration? If so, please give details. Ms. Weinberg said, “Most people within the
community have the same concerns regarding how contaminants make their way into the Great Salt Lake.
And how contaminants are affecting water quality, toxic dust plumes, and how they affect bird ecology
and microbialites. Additionally, how contaminants leaching into the whole system are general concerns
for the Great Salt Lake community.” Ms. Weinberg said, “People keep a close watch on the Lake and
everything that’s being done and pay attention. Especially for mineral extractors, the general impression
from the public is a negative history of having affected the air and water quality in the past are general
sentiments from meetings with the public interactions we’ve been involved with.”

5. Over the past five years, have there been any complaints, violations, or other incidents (e.g., vandalism, trespassing, or emergency responses) at or related to the Kennecott North Zone Superfund Site
requiring your office to respond? If so, please give details of the events and results of the response.
Ms. Weinberg said there hasn’t been any incident related to the Kennecott site that has been reported.
“The south shore of the Great Salt Lake has had a history of issues of vandalism and crime activities just
because of the accessibility to the area. It’s right off of I-80 and Salt Air, where it’s easy to walk to the
shoreline and to Black Rock,” said Ms. Weinberg. Ms. Weinberg said, “Their office has done a lot to
remediate the area by removing graffiti and installing a gate to limit traffic areas. Salt Air holds concerts,
and people have set fires and want to camp which are not allowed.” Ms. Weinberg said those activities
are better monitored and things have become better. “We do have Departmental Staff with eyes on the
ground with a Harbor Master who lives at the marina full-time and recently added a Law Enforcement
officer with the ability to patrol the shoreline more actively,” Ms. Weinberg stated.

6. Do you feel well informed about the site’s activities and progress over the last five years? Do you know
how to contact the Environmental Protection Agency if you have questions or concerns about the
Kennecott North Zone Superfund Site? Although relatively new to the TRC, Ms. Weinberg said they value
their partnership with DEQ and feel comfortable reaching out when we have questions or concerns. The
transparency in the past year, which Ms. Weinberg has been involved with, has been great. “We are
basically land managers and rely heavily on our partnerships to keep us involved with activities
surrounding the lake” Ms. Weinberg said.
7. Over the past five years, have there been any changes in your department’s policies or regulations that
might impact the Superfund Site from a perspective of land use, water rights, redevelopment, and site
management? Ms. Weinberg said, “There is recent legislation (House Bill 513) that could impact the
North Zone Kennecott site indirectly regarding mineral extraction and how water could be replaced and
not affect PH or other chemical balances. FFSL and the UDEQ-Division of Water Quality are working on
rules to implement processes primarily addressing mineral extraction which could impact any hydrological
connections to the North Zone even though they are upland of the Lake. Kennecott may not be directly
involved right now but in the future, as these connections are more understood could be an issue of
concern in the future.”

8. Over the past five years, have there been any changes in land use surrounding the Kennecott North
Zone Superfund Site? Are you aware of potential future changes in land use? Ms. Weinberg said DNR is
planning with Water Resources to dredge the marina for search and rescue boat access for the Lake.
There is nothing that would impact the Kennecott area only the land adjacent to the site.

9. Do you have any comments, suggestions, or recommendations regarding the site’s management or operation (institutional controls)? If so, what types of future problems do you think (1) could occur; or
(2) would concern you and/or your department? Ms. Weinberg said, “It’s great to learn about all the
work going on at the North Zone site and close the data gaps to increase their efforts. As far as future
concerns.” Ms. Weinberg said they are “Continually learning about how the hydrological connections and
the upland areas may be related and just want to make sure the contaminants are not adversely affecting
the lake. Transparency and keeping us in the loop, the research going on, and how we can be involved in
sharing our data with their data is valuable and helps ensure we’re all on the same page and help each
other.”
North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone
EPA ID: UTD070926811
March 14, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox, UDEQ-
DERR, and Maggie Ogden and Missy Haniewicz, US
EPA Region 8.
Person Contacted
Name: Eric Barney, Magna Mayor Organization: Magna Metro Township
Address:
8952 West Magna Main Street
Magna, UT 84044
Phone: [phone]

1. Is your organization/department aware of the Kennecott North Zone Superfund site and the actions
underway to address environmental contamination? Mayor Eric Barney said he recently became mayor
at the beginning of the year and served as a city council member prior to becoming mayor. Magna has a
population of nearly 30,000 and is located to the northeast of the Oquirrh Mountains and directly south
of the Great Salt Lake. “I'm aware that there is a tailings impoundment and mining operations happening to the north of us. I was not aware that it was classified as a Superfund site and was not aware of any
cleanup efforts that have been done,” Mayor Barney stated.

2. What’s your overall impression (your general sentiment) of the actions performed at the Kennecott
North Zone Superfund Site? Mayor Barney said the population of Magna has shifted significantly as far as
connections to or employment history with Kennecott as it is today. “It would not be unreasonable to say
that very few residents in Magna now actually are employed by or work for Rio Tinto. There is also some
sentiment of skepticism and concern about Kennecott and the way they have managed some of their
operations. Particularly as it surrounds an expansion of the tailings impoundment and how that was
handled. There were public meetings advertised, canceled, and then re-advertised and the public input
was diminished by the changes,” Mayor Barney stated. Mayor Barney said he doesn’t know what was
communicated in the past about Magna's feelings towards Kennecott but he thinks that we will find my
perceptions and feelings are a little more questioning, concerned, and skeptical.

3. Does your office conduct routine communications and/or activities (site visits, inspections, reporting
activities, participation in meetings, etc.) for the Kennecott North Zone Superfund Site? Mayor Barney
said there are not any regularly scheduled communications or briefings with Kennecott or the North Zone
Superfund Site. Mayor Barney said Kennecott has attended City Council Meetings on request and the last
time was for questions regarding the tailings impoundment.

4. Are you aware of any community concerns regarding the Kennecott North Zone Superfund Site or its operation and administration? If so, please give details. Mayor Barney said he has experienced concerns
with the tailings impoundment dust. There are a lot of questions and upset residents wondering if the
tailings impoundment is safe after a grading project on the south side of the impoundment that remained
unvegetated for a long time. “Every time a north wind blows, we get a little bit of a dust storm over
Magna, so there are questions or concerns about what is in that dust. This is the oldest part of the tailings
impoundment, so arguably it's probably the least clean for reason. One would suspect that practices in
the past were less effective than they are today,” said Mayor Barney. Mayor Barney said his questions
were about what is in the tailings impoundment and the answers from Kennecott contractors were more
about the intention of the impoundment.

Mayor Barney stated that a few weeks later, Kennecott did come to us and say, ‘We hope you noticed on
the south face we did apply soil stabilizer’. “I believe it's a polymer of some sort to kind of lock the dry soil
in place on that south face,” said Mayor Barney. Mayor Barney said “I don't know to the extent or how
effective it is. We still get dust when the North wind blows whether that dust is coming from that hillside,
or further back in the impoundment, or from the Great Salt Lake bed. I don't know, but multiple residents
have expressed these concerns.”

Mayor Barney said, “The railway that runs along the entire West boundary of Magna is also a concern.
We have a new D.R. Horton housing development which abuts almost directly to the railway. The
understanding is what is being transported in those rail cars is sulfuric acid. This is a safety issue if a spill
or derailment and precautions are in place is a real concern.”
5. Over the past five years, have there been any complaints, violations, or other incidents (e.g., vandalism,
trespassing, or emergency responses) at or related to the Kennecott North Zone Superfund Site
requiring your office to respond? If so, please give details of the events and results of the response.
Mayor Barney said, “The only incident I can think of is the request for expansion of the tailings
impoundment. The lack of transparency about the meetings and unwillingness of Kennecott contractors
to provide a detailed chemical composition of the soils and water for transparency reasons.”

6. Do you feel well informed about the site’s activities and progress over the last five years? Do you know
how to contact the Environmental Protection Agency if you have questions or concerns about the Kennecott North Zone Superfund Site? Mayor Barney said, “I don't feel like we're informed at all. To my
knowledge, there hasn’t been an active effort on Kennecott's part to communicate plans and what the
future holds. We're just watching from a distance and I do think there is an opportunity here to be
more transparent. Now, maybe Kennecott has made efforts and maybe the information was given to the wrong person. I will give them the benefit of the doubt but I’m not getting the information I’d like.”

7. Over the past five years, have there been any changes in land use surrounding the Kennecott North
Zone Superfund Site? Are you aware of potential future changes in land use? Mayor Barney said,
“We're landlocked by Kennecott properties on three of our four sides and West Valley City on the
other. Our only opportunity for expansion and development is through the annexation of Kennecott
properties. We've made our intentions clear on which of those properties we would like to have first dibs
on. Also, the D.R. Horton development was leveraged for annexation with West Valley if Magna did not
accommodate Kennecott's demands.”

Mayor Barney said, “This experience is really disenfranchising and very actually, almost hostile. I get
you're a private property owner, you're running a business, and sometimes you want to liquidate your
properties, but it just leads to skepticism and frustration. This is not necessarily ideal for what our goals
and long-term plans were but we had to accept because Kennecott deemed it so. Does that make sense?
We did have to make some concessions to D.R. Horton and then now we have a neighborhood that abuts
to a railway that's running. As a municipality, we lost a voice because we were being threatened for lack of better terms. We do it their way or we don't do it at all, right?”

Mayor Barney said, “A land use issue less about an environmental hazard and more about access. We
have a lot of residents, especially the new ones that move in and misunderstand access to what
historically or typically in Utah you would think of mountain ranges as public access, a public
resource. And oftentimes people are surprised that you have no access to those mountains, surrounding
Magna as it ends here. You don't go past it. So, there is a little bit of resentment and heartburn towards
Kennecott that areas of the Oquirrh’s that are not being utilized for active mining and they seem intent on
restricting access.”

“We feel like this could be a real resource and value added to our residents and a way to promote
economic growth and development of Magna in general, a great, really underutilized resource. They have
been willing to work with our neighbors to the south and have released lands and trails near the
Butterfield Canyon area.” Mayor Barney said.

Mayor Barney said, “We recognize they're a private property owner and we want to be good neighbors
too, but maybe there is a way they could be a better neighbor and figure out a way to open up some of
this resource for public use. That might be a nice thing.”

Mayor Barney said, “Although the Kennecott properties are not necessarily in Magna boundaries proper,
our Magna boundary does like kind of snake around the tailings pound and then it opens up and engulfs
the shore of the Great Salt Lake and out into the Great Salt Lake.”

“The Marina, Saltair, and Great Salt Lake State Park are all within Magna boundaries and grossly
underutilized resources for Magna. We're looking to capitalize more on those resources in the future
economically. But they are surrounded by a Superfund Site. So, perception is often people's reality. If
good data and good information can clear the air of suspicion and accusation, then that makes things a lot
easier for us to move our intentions forward with some of our long-term goals for growth and
development,” Mayor Barney said.

8. Do you have any comments, suggestions, or recommendations regarding the site’s management or
operation (institutional controls)? If so, what types of future problems do you think (1) could occur; or
(2) would concern you and/or your department? Mayor Barney said, “I think transparency is the biggest recommendation. Honesty, clarity, transparency, and what that looks like to me is active communication
from Kennecott Rio Tinto. I don't feel like I should have to reach out to Rio Tinto to ask them what they're
doing around my community. I feel like they should be a good steward and a good neighbor and be
transparent and open with us instead of just at the request”. Also, “trust” said Mayor Barney. “Be honest
with us, be transparent, and if you have nothing to hide there should be no fear there. And obviously,
Kennecott is heavily regulated and I understand what regulations look like and the burden of meeting
regulators requirements. I can sympathize with Kennecott in that regard, but I just feel like transparency,
honesty, openness, and an active effort to do so does go a long way.”

Mayor Barney said, “Although the Kennecott properties are not necessarily in Magna boundaries
proper. Our Magna property does like kind of snake around the tailings pound and then it opens up and
engulfs the shore of the Great Salt Lake and out into the Great Salt Lake.”

Mayor Barney said, “The Marina, Saltair, and Great Salt Lake State Park are all within Magna boundaries
and grossly underutilized resources for Magna. We're looking to capitalize more on those resources in the
future economically. But they are surrounded by a Superfund Site. So, perception is often people's
reality. If good data and good information can clear the air of suspicion and accusation, then that makes
things a lot easier for us to move our intentions forward with some of our long-term goals for growth and
development. Kennecott will place billboards up on 201 (highway) really quickly after the tailings
expansion advertising how necessary copper is for America and helping America. This is great but are you
taking care of us because we're your neighbor?” Mayor Barney said that he wants Kennecott to be a good
steward of the properties they have around them and to “not kill us with your toxic waste”.
North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone EPA ID: UTD070926811
March 6, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox, UDEQ-
DERR, and Missy Haniewicz, US EPA Region 8.
Person Contacted
Name: Hayley Shaffer, Supervisor – Water Quality &
Hazardous Waste Bureau
Neil Opperman, Environmental Health Scientist
Organization: Salt Lake County Health Department –
Environmental Health Division
Address:
788 East Woodoak Lane (5380 South)
Murray, UT 84107
Phone: [phone]

1. Is your organization/department aware of the Kennecott North Zone Superfund site and the
actions underway to address environmental contamination? Hayley Shaffer is the Supervisor for the
Water Quality & Hazardous Waste Bureau and Neil Opperman is an Environmental Health Scientist for the
Salt Lake County Health Department (SLCoHD). The SLCoHD is the local health department for Salt Lake
County and the Environmental Health Division monitors all environmental contamination including
Superfund Sites within the County. Shaffer said her section oversees annual inspections of three landfills
within the North Zone Kennecott Superfund Site. The SLCoHD Environmental Division works together with other County Divisions, and through notifications, the county building permit processes and
ordinances help monitor construction in areas located in the Kennecott North Zone. They also mentioned
that although they do not have a formal role in the Community Planning and Development Division, if a
property owner or developer wants to build in the area, it would go through the planning department
with notification of their Division. The SLCoHD coordinates these Institutional Controls with UDEQ if there
were construction in cleanup areas requiring additional oversight.

2. What’s your overall impression (your general sentiment) of the actions performed at the Kennecott
North Zone Superfund Site? The SLCoHD staff said there were no indications of any issues and have not
received any complaints from the community with the North Zone locations they inspect. The SLCoHD
Staff said they check to make sure only the permitted material goes into the appropriate landfill. One
landfill is small and located at the North Tailings Impoundment pond area, and the concrete and smelter
landfills are located above the smelter smokestack area. The respective landfills are limited to what is
placed there and in general, refuse is tested before placement. The SLCoHD Staff said Kennecott does a
really good job and is contracted with Clean Harbors to dispose of any material indicating a positive hit
and not meeting landfill permit standards. Similarly, to municipal landfill requirements, these landfills
must maintain daily cover and depths standards as well as stormwater controls. The SLCoHD also receives
semi-annual groundwater sampling results from Kennecott which are sent to UDEQ.

3. Does your office conduct routine communications and/or activities (site visits, inspections,
reporting activities, participation in meetings, etc.) for the Kennecott North Zone Superfund Site? The
SLCoHD Staff said their yearly permit inspection reports are sent to Kennecott who then provides the
results to the regulators, the Utah Department of Environmental Quality, Division of Solid and Hazardous
Waste.

4. Over the past five years, have there been any complaints, violations, or other incidents (e.g.,
vandalism, trespassing, or emergency responses) at or related to the Kennecott North Zone Superfund
Site requiring your office to respond? If so, please give details of the events and results of the
response. The SLCoHD staff said they have been overseeing Kennecott for the past two years and have
not encountered any issues or received any complaints from the public regarding the site. The SLCoHD
reviews landfill permit inspections at the North Zone and records did not show any violations over the last
five years. No complaints were reported to their office with regard to the North Zone area either. SLCoHD
Staff said they checked with their Emergency Response Team and also did not find any incidents requiring
a response from their Department over the last five-year period within the North Zone Site.

5. Do you feel well informed about the site’s activities and progress over the last five years? Do you know how to contact the Environmental Protection Agency if you have questions or concerns about the
Kennecott North Zone Superfund Site? The SLCoHD Staff said although they were relatively new to their
current positions, they had been very well informed on cleanup sites within the County by UDEQ. There
were monthly meetings with Storm Water and UDEQ to outline the communication channels and to
provide a good direction. The SLCoHD Staff said being more familiar and having dealt with the UDEQ
Project Manager would probably call them before reaching out to EPA.

6. Over the past five years, have there been any changes in your department’s policies or regulations
that might impact the Superfund Site from a perspective of land use, water rights, redevelopment, and
site management? SLCoHD staff said other than staffing changes everything, regulations, and permit
fees, have all stayed the same.

7. Over the past five years, have there been any changes in land use surrounding the Kennecott North
Zone Superfund Site? Are you aware of potential future changes in land use? The SLCoHD staff is not
aware of any changes in land use which is primarily industrial. There is active development on the west
side of Salt Lake City including discussions on a new prison and Inland Port which may encroach on
Kennecott properties in the future.

8. Do you have any comments, suggestions, or recommendations regarding the site’s management or
operation (institutional controls)? If so, what types of future problems do you think (1) could occur; or
(2) would concern you and/or your department? The SLCoHD Staff said they do not have any problems
or concerns at the moment and with more time on the job would be able assess future issues. The SLCoHD Staff expressed satisfaction with the site's management and operation and did not have any
significant concerns or recommendations.

North Zone Kennecott Superfund Site
Five-Year Review
Interview of Local Agencies

Site Name: Kennecott North Zone
EPA ID: UTD070926811
March 12, 2024
Type of Contact: Teleconference Call Contact Made By: Dave Allison and Mazie Cox, UDEQ-
DERR, and Maggie Ogden and Missy Haniewicz, US EPA
Region 8.
Person Contacted
Name: Ivan Weber Organization:
Local Citizen, Weber Sustainability Consulting
Address:
953 E. 1st Avenue
Salt Lake City, Utah 84103
[e-mail]

1. How long have you lived in the area? Ivan Weber has lived in Salt Lake City for nearly 50 years and has a
consulting business named Weber Sustainability Consulting. Mr. Weber said he has lifelong interest in
local environmental issues and the science community and had a professional working history for
Kennecott at one time. Mr. Weber said he responded to the site Five-Year Review public notice in the Salt
Lake Tribune newspaper. Mr. Weber said he wanted to learn more about the current Kennecott North
Zone activities, share his concerns, and share his environmental experience with his time at Kennecott.

2. Are you aware of the Kennecott North Zone Superfund site and the work that was completed to
address historical environmental contamination? Mr. Weber said he was familiar with the North Zone
site and was employed in environmental management for Kennecott’s Environmental Engineering
Projects Group (EEPG), from 1992-2001, as a contract employee. Mr. Weber was Editor and Archivist for
KUCC-EEPB, the primary documents gathering and editing group for environmental issues, including both
South and North administrative and regulatory facilities. Mr. Weber worked on South Zone projects with
documentation management on the Bingham Creek groundwater contamination remediation, Large and
Small Bingham Reservoir construction, and QA/QC documentation. Mr. Weber also worked on
phytoremediation research and development, post-remediation, land use planning and development
projects while with Kennecott.

3. What’s your overall impression (your general sentiment) of the work that was completed at the Kennecott North Zone Superfund Site? Mr. Weber said although he may not have an overall impression
of the North Zone remediation history, his experience has shown an interconnectedness with every
chemical introduced in the environment affecting ecology and human health in ways we need to
understand. Mr. Weber said over the decades and centuries to come, there should be an urgency in every
category and scale to prevent pollution and contaminants introduced into the environment. “It's
important to comprehend watershed-wide hydrology and airshed-wide air quality awareness to make
policy to align proper mine closure plans,” said Mr. Weber.

4. What would you say are the effects that site operations had on the community surrounding the
Kennecott North Zone Superfund Site. Mr. Weber’s Kennecott background working with and
investigating selenium-related issues, like those at the North Kennecott Zone, is an advocate for adequate
science and applications of appropriate scientific methods to resolve problems. Mr. Weber said examples
of inadequacies of selenium ecotoxicology in both wildlife and public health exposures seem not to have
been registered through previously deliberate scientific methodologies and institutions. Mr. Weber cited
the literature work of Joseph Skorupa on Selenium ecotoxicology as one example. Mr. Weber said
challenging conventional research is important that find dramatic differences in embryo tissue levels of
Selenite and Selenate, compared to respective levels in water where those embryos occur. Mr. Weber
said Skorupa’s findings on bioaccumulation of selenium in tissue say there may be more than meets the
eye regarding the selenium standard Utah uses today.

5. Are you aware of any community concerns regarding the Kennecott North Zone Superfund Site and its administration? If so, please give details. Mr. Weber said the Great Salt Lake is a known challenge within
the scientific community. Mr. Weber said we are compelled to think about what the meaning of global
climate change could be to this place, to our air particularly and to our water quality. Mr. Weber said also
has both personal and public health concerns but especially public health. Mr. Weber said he wonders if
his personal health issues are caused partially or wholly by his near-lifetime of mining-generated heavy
metals exposures.

6. Do you have any additional comments, suggestions, or recommendations regarding the Kennecott
North Zone Superfund Site? Mr. Weber said his concerns are related to the scientific methodology and
how we ask questions about longer-term and broader scale to address a rapidly growing urban
environment. Mr. Weber said he is hopeful for the future with his industrial ecological attitude and takes
a positive optimistic approach to problem-solving.

“Are human health studies being conducted with sufficient bases to explore such detail? What will
current sciences do to cope with political processes that prohibit science, administrative agencies such as
EPA and UDEQ, books, journals, libraries, on-line communications and repositories, as currently
threatened by elections that may afflict us all in approximately eight months?” said Mr. Weber.

“Please allow me to boil down my comments to these two core points, both relating to the proportional,
overall reduction of water resources in the watershed, effectively concentrating Kennecott contaminants over an astonishingly brief timeframe: Population growth in the watershed has exploded since settlement
in 1847, growing to at least three million people by the present (2018), and projected to grow to at least
five million people by 2040. Given the powerful disinclination for regional administrative bodies. The
greater reduction of water in the Great Salt Lake, as observed during the basin’s 1.5 century, is estimated
in the geographic world to continue past the present 50%. The division of administrative segments into
the seven that are subject to public notice severely discourages public awareness of the physical,
geochemical concentration of Kennecott contaminants versus urban and other industrial contamination in
the region.” said Mr. Weber.

“Until UDEQ/DERR and the U.S. EPA engage in the serious quantification of contaminant proportions
compared to environmental resources in this intensely rapid-growing population area, there can be little
or no seriousness to critical review of Kennecott/Rio Tinto’s operations and categories of effluent, either
from these North Superfund Sites or from the counterparts at the South Zone,” said Mr. Weber.