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HomeMy WebLinkAboutDWQ-2024-008093RENEWAL OF GROUND WATER DISCHARGE PERMIT NO. UGW350011 STATEMENT OF BASIS Kennecott Utah Copper LLC (Permittee)Tailings Impoundment Magna, Utah November 2024Basis for Permit Renewal / ModificationThis Ground Water Discharge Permit No. UGW350011 (Permit) is being renewed in accordance with Utah Admin. Code R317-6-6.6 and Utah Admin. Code R317-6-6.7. The Permit was initially issued to Kennecott Utah Copper in 1996 in accordance Utah Admin. Code R317-6-6.4. Previous renewals of the Permit were issued in 2001, 2006, 2011 and 2017. This is the fifth renewal of the Permit. Permittee submitted a timely renewal application on April 6, 2022. Summary of Changes from Prior Permit East Tailings Expansion: Permittee will expand the tailings impoundment area by approximately 173 acres adjacent to the east of the South Tailings Impoundment. The project extends the east toe of the South Tailings Impoundment by about 1,000 ft to the east. East Tailings Expansion will be raised in conjunction with the North Tailings Impoundment, which will be raised to elevation 4,500 feet consistent with the previously permitted design. The East Tailings Expansion is designed to an elevation of 4,440 feet, consistent with the South Tailings Impoundment elevation. Compliance Schedule: The following items are included in the permit compliance schedule: Facility Closure Plan - At any time during the effective period of this Permit, Permittee shall submit within 180 days of written request by the Director, a revised closure plan for the Facility. The currently approved preliminary closure plan for the Facility is contained within “Reclamation and Water Management Plan, Kennecott Utah Copper Corporation, Bingham Canyon Mine” submitted in March 2003. Within three years of mine closure, Permittee shall submit a final set of engineered drawings and plans that clearly define the scope of the final closure for the North Tailings Impoundment and the South Tailings Impoundment and the East Tailings Expansion. The plan shall provide details on all aspects of closure and closure monitoring which are related to or have an impact on surface water or ground water quality, including all pre- and post-mine closure water sources. For any issues that require further study prior to finalizing aspects to the closure plan, details on what each study will include, and a schedule with milestones for each segment of the study shall be included in Permittee's revised plan. Evaluations - Permittee shall conduct the following evaluations and provide the following information to evaluate the performance of the discharge minimization design of the facility and to provide an updated understanding of water quality underlying the facility:Discharge Minimization, Bonneville Clay, and Embankment Drainage System Information and Investigation- Within one (1) year of the issuance of this Permit, Permittee shall submit to the Division the following information:Compilation of previously submitted reports of the Bonneville clay investigations, including applicable updates, if any are identified.An overview of the North tailings embankment drainage system design and analysis of its effectiveness in maintaining design phreatic surface levels in the embankment including phreatic surface level over time.Compilation of previously submitted reports of the Hydrogeology for the North impoundment and East tailings expansion areas, including applicable updates, if any are identified. Calculate the depth of equilibrium for the impoundment hydraulic head and upward groundwater flow.Following the submission of the previously identified information the Director may require an investigation to show the physical integrity and continuity of the clay and drainage features based on a review of the provided information. Molybdenum Sampling- Based on the processing and recovery of molybdenum and molybdenum ore at the locations which send waste materials to the Facility, Permittee shall sample permit compliance wells for molybdenum during routine groundwater monitoring for four semi-annual sampling events following issuance of this Permit. The results shall be included in the semi-annual monitoring reports. Based on the results of the sampling the Director may establish a molybdenum permit specific standard and permit limit based on Utah Admin Code R317-6-2.2. Blasting Compounds Study and Sampling- Within one (1) year of the issuance of this Permit, Permittee shall begin to sample the compliance monitoring wells, tailings water and tailings slurry on a semi-annual basis for blasting residue of any explosives used in the mine for a period of two years. The sampling shall include Total inorganic Nitrogen (TIN). The tailings slurry at the north splitter box and the decant pond will be sampled for total petroleum hydrocarbons (TPH) semi-annually for a period of two years. If petroleum hydrocarbons are detected in the decant pond and tailings slurry the Director may require the compliance monitoring wells to be sampled for TPH. Results for TIN and TPH sampling shall be included in the regular groundwater monitoring reports.Hydrostatic Equilibrium Calculation and Brine Mixing Zone Location – Within two (2) years of the issuance of this Permit, Permittee shall provide DWQ with a report detailing the calculation of the equilibrium depth of hydraulic head pressure versus natural upward flow in the subsurface below the facility as well as detailing the depth and geographic location of the mixing zone between saline waters below The Great Salt Lake and the freshwater system underlying the facility. Plan Review - Review the Assessment of Acidification Potential Plan to ensure reporting of the pH meter data from the north splitter box to the division with acidification potential reporting. Collect and report the meteoric rainfall data for the neutralization process. If the plan requires an update to include reporting of the pH meter data, the permittee shall submit an updated plan to the Division.Permittee may install additional monitoring wells to serve as potential replacement or supplemental monitoring wells on the east side of the southeast corner of the South Impoundment to gain more information on groundwater for this area. In addition, Permittee may install additional monitoring wells to serve as potential replacement or supplemental monitoring wells related to the construction of the East Tailings Expansion. If new wells are installed at the discretion of the Permittee, Permittee shall submit all relevant well construction details as required in the Permit. For this renewal/modification, the authorized waste stream inflow materials have not changed. Since Permittee has requested renewal as well as met the applicable criteria in Utah Admin. Code R317-6, the Permit is being renewed for another five-year term. Basis for Specific Permit Conditions1.Corrective Action - The Utah Administrative Rules for Ground Water Quality Protection (Utah Admin. Code R317-6) require applicants to submit a Corrective Action Plan or other response measures to remedy any violation of ground water quality standards resulting from discharges. The Permit has a compliance condition that allows the Director to call for a Contamination Investigation and Corrective Action Plan to be submitted and made a part of the Permit should future data indicate that clean-up of contamination at the Facility site is needed. 2.Assessment of Acidification Potential - Ongoing analysis and testing is required to assess the potential for the tailings material to acidify using Net Acid Generation (NAG) testing. Permittee shall provide an annual report that compiles the results of each year’s sampling and analysis.3.Operational Monitoring Plan - A water quality summary and analysis is required to assess long-term changes to water quality over the life of the Facility. The quality of interstitial waters within the tailings, waters that are decanted from the top of the impoundment and other outflows such as seeps, and characterization of inflows will provide information that will assist in predicting potential impacts from the impoundment as well as track changes over time. Permittee shall provide an annual report that compiles the results of each year’s sampling and analysis.4.Permit Renewal/Modification Application Items - This condition requires the following items to be included in the request for permit renewal to be submitted 180 days prior to permit expiration in the year 2029:1) Maps of the potentiometric surface for both the Shallow and Principal Aquifer systems in order to observe temporal changes to these aquifer systems near the impoundment, and;2) Monitoring results for radionuclides and uranium in wells NET1386A&B and NET1393A&B. 5.Closure Plan - Any proposed changes to the current closure plan based on ongoing characterization of tailings mineralogy, impoundment surface oxidation, internal pore water chemistry, or other data, shall be submitted to the Director for review and approval. BackgroundPermit HistoryTo assure adequate ground water quality protection, the Tailings Impoundment (Facility) was designed to employ discharge minimization and control technology with ground water monitoring to prevent any impairment of present and future beneficial uses of the ground water. Ground water monitoring is the primary compliance monitoring method for the Facility. Permittee performs general monitoring of the well network to develop a data base and identify ground water quality trends. Compliance monitoring is performed at selected wells located outside the impoundment footprint. Most well locations are situated to characterize the influence of the tailings disposal on ground water. Compliance monitoring wells are listed in Table 1 of the Permit. In addition, the locations of the compliance monitoring points are shown Appendix B of the Permit. The compliance monitoring parameters are listed in Permit Part I, Section E. Description of Facility The Facility is located in portions of Sections 1, 2, 3, 10, 11, 12, 13, 14, 15, 23 and 24 of Township 1 South, Range 3 West; Sections, 5, 6, 7, 8, 9, 17, 18, 19, and 20 of Township 1 South, Range 2 West; Sections 31of Township 1 North, Range 2 West; and Sections 35 and 36 of Township 1 North, Range 3 West. (40º 45.449’ N 112º 7.574’ W) The Facility has operated since 1906 for the storage of tailings from concentrators processing ore from the Bingham Canyon mine. The Facility has undergone numerous changes and expansions to accommodate increases in the volume of materials. The original 1,350-acre impoundment was located in the western portion of the Magna impoundment area. Around 1914, the original impoundment was enlarged to the east by approximately 1,466 acres. By the early 1990's, the footprint of the South Impoundment had reached approximately 5,700 acres with a height of over 220 feet, storing 1.5 billion tons of tailings. The South Impoundment currently does not receive new tailings materials but could receive tailings in an upset or management-designated situation. The North Impoundment Completion will raise the northern perimeter of the South Impoundment to 4500 ft in elevation using cyclone tailings underflow with a modified centerline construction method over the remaining life of the Facility. The change in final height of the impoundment is permitted by the Utah State Engineer. In 1995, Permittee added approximately 3,300 acres adjacent to and north of the existing impoundment to enable continuity of Bingham Canyon Mine operations. This expansion also allowed for a seismic upgrade of the impoundment. Beginning in 1999, tailings deposition began transitioning from the South Impoundment to the North Impoundment. The current discharge into the North Impoundment ranges up to approximately 200,000 tons per day of tailings from the Copperton Concentrator. Projects associated with ongoing management of waste stream materials permitted for the tailings that do not affect the tailings mineralization, surface oxidation of the impoundment or pore water chemistry do not require Director review and approval. South Impoundment - Draindown water from the South Impoundment is collected in the Clarification Canal, the West C7 ditch and from drainage north into the North Impoundment. When necessary, the water in the clarification canal can be discharged through UPDES permitted discharge points. Some seepage from the South Impoundment enters the Shallow Aquifer system. The seepage rate may gradually decrease over time due to the establishment of a vegetative evapotranspiration cover. The South Impoundment is underlain by the Bonneville Clay; a thick, laterally extensive, low-permeability lacustrine deposit. Sedimentation Pond - The Sedimentation Pond, located east and adjacent to the South Impoundment, was constructed during the North Tailings Impoundment expansion activities. The Sedimentation Pond was used to settle out sediment (tailings) and direct tailings from flows associated with tailings impoundment water management. The Sedimentation Pond also serves as an emergency overflow location for tailings in the event of power failure and for longer term closure-related activities. The Sedimentation Pond is no longer needed for settling out tailings, so the pond has been partially filled with coarse tailings and it is anticipated to be filled entirely as part of the East Tailings Expansion project. Sedimentation Pond is pumped to the Clarification Canal for use as process water. The Sedimentation Pond is underlain by the low permeability Bonneville Clay. East Tailings Expansion (ETE) –The ETE will add 173 acres of disturbance on land without previous tailings deposition. The new disturbance is adjacent to the east side of the of the existing South Impoundment. The area includes part of the existing South Impoundment (approximately 327 acres) and process water facilities (approximately 39 acres, i.e., Clarification Canal and Sedimentation Pond). The ETE also includes some undeveloped land east of the Clarification Canal. The project area is roughly bounded by 2400 South (S) on the south, C-7 Ditch (adjacent to S. 8000 West) on the east, and portions of the existing tailings facility on the west and north. The ETE is mostly within Sections 8, 17, and 20 of Township 1 South, Range 2 West. Elevations range from about 4,400 feet at the top of the ETE to 4,220 feet on natural terrain on the east side of the ETE. The addition of material from the ETE at the toe of the slope will buttress the slope and the use of finger drains will increase the dynamic Factor of Safety of the South Impoundment. The project will consist of constructing the ETE Impoundment, relocating infrastructure, and raising the North Impoundment. The ETE will be adjacent to the South Impoundment and is underlain by Bonneville Clay, a thick, laterally extensive, low-permeability lacustrine deposit that also underlies the existing North and South Impoundments. A drainage blanket will also be constructed underneath the ETE. A toe ditch around the proposed expansion will also be added and monitoring wells currently adjacent to the south impoundment will be relocated to the east. North Impoundment - The North Impoundment is underlain by the Bonneville Clay, a thick laterally extensive low-permeability lacustrine deposit. This contiguous stratum represents the top layer of a several hundred-foot-thick sequence of fine-grained lacustrine sediments. Tailings are deposited into the North Impoundment in slurry form from a discharge system that deposits tailings into the interior as well as through a peripheral system fed by two cyclones. Cyclones direct overflow (fine-grained material) to the interior and the underflow (coarse material) to the embankment. An underdrain consisting of a blanket drain and finger drains composed of crushed slag were constructed in the base of the embankment to promote horizontal seepage of water under the embankment and into the perimeter toe drain collection ditch. Water is also removed from a decant pond and recycled back to the Copperton Concentrator. When necessary, the water can be discharged through a UPDES permitted discharge point. Some seepage from the North Impoundment enters the Shallow Aquifer system. Diving Board - The Diving Board area is located immediately south of State Road 201 and west of 9180 West. This area is a small earthen impoundment designed to retain tailings discharges resulting from temporary upsets and stormwater from adjacent areas including the south side of the South Impoundment. Drainage from this area is collected via a ditch and channeled to the Clarification Canal. The Diving Board is underlain by the Bonneville Clay, a low-permeability lacustrine deposit. Waste Stream Inflows - Waste stream inflows authorized under the Permit for placement in the Facility are:Copper tailings from the Copperton Concentrator;Slag tailings from the slag concentrator at the Smelter;Smelter process waters; Wastewater effluent slurry from the Hydrometallurgical Plant at the Smelter;Mine leach water, south-end groundwater and meteoric contact water that have been treated (via mixing over distance) in the tailings pipeline;Wastewater effluent from the Reverse Osmosis treatment of sulfate-contaminated waters; Neutralized acid-mine contaminated waters;Barneys Canyon pit dewatering and heap leach pad and other drain-down waters;Construction, maintenance and non-hazardous trash (Salt Lake Valley Health Department Permit: 35-0011805 covering footprint of Tailings Impoundment);Treated effluent from the sewage treatment plant; and non-process impacted storm water;Leakage collection system water from the Arthur Stepback Repository (CERCLA CAMU);These materials enter the Facility at the following discharge points:West Cyclone StationEast Cyclone stationNorth Impoundment Single Points DischargeNorth Impoundment Peripheral DischargeThe majority of materials placed in the Facility is copper tailings. Following settlement of a Natural Resources Damage Claim, the State of Utah has approved a plan to clean up contaminated ground water in the Southwest Jordan Valley area of Salt Lake County. Over the 40 years following the settlement, extraction and treatment of ground water from contaminated zones will remove contaminants and provide municipal-quality drinking water to the public. By removing contaminated water from the underlying aquifer, the project will also improve ground water quality and prevent further migration of the contamination in the valley. In the absence of a better disposal option for contaminants removed from the treated water, the treatment concentrates will be introduced into the tailings pipeline for disposal in the Facility. Site Hydrogeology Three aquifer systems exist in the vicinity of the Tailings Impoundment: Bedrock system associated with the Oquirrh Mountains; Confined Principal Aquifer; and, Unconfined Shallow Aquifer. The Bedrock Aquifer is comprised of highly fractured Paleozoic carbonate rocks. Recharge to this system is principally from precipitation from the Oquirrh Mountains to the south. The flow-path through this aquifer travels from the fractured bedrock into the Principal and Shallow Aquifers or is discharged as spring water along bedrock contacts at the base of the mountains. Water quality of the Bedrock Aquifer is generally Class II ground water (TDS less than 3,000 mg/l). The Principal Aquifer is a confined system which includes a gravel zone and lacustrine deposits. The gravel zone was most likely derived from the local mountains during an extensive low lake cycle. Many high-yield water supply wells near the Oquirrh Mountains are completed in the gravel zone of the Principal Aquifer. The lacustrine zone consists of clay, silt, and interbedded fine sand. Ground water flow direction for the Principal Aquifer is north toward the Great Salt Lake. Measured water levels in the Principal Aquifer wells located around the perimeter of the Facility are above the water levels in adjacent nested Shallow Aquifer wells, indicating an upward hydraulic gradient throughout the vicinity of the North and South Impoundments. The majority of Principal Aquifer wells located along the perimeter of the North and South Impoundments are flowing under artesian conditions. Ground water quality in the Principal Aquifer is generally better than the Shallow Aquifer, with TDS values ranging from approximately 700 to 30,000 mg/l. The higher TDS values correlate with proximity to the Great Salt Lake. The Shallow Aquifer system consists of interbedded lacustrine Bonneville Clay, silt, and fine sand. The exact depth of this system varies but is approximately the upper 35 to 50 feet of saturated sediments. The potentiometric surface for the Shallow Aquifer system depicts lateral flow in a northerly direction toward the Great Salt Lake. An upward hydraulic gradient from the underlying Principal Aquifer exists for the majority of well nests completed in both the Shallow and Principal Aquifers. Localized confining conditions exist in the Shallow Aquifer within the Facility area. The majority of the Shallow Aquifer wells located along the northern perimeter of the North Impoundment are flowing under artesian conditions. The hydraulic head in the Tailings Impoundment is higher than the hydraulic head in the Shallow Aquifer, resulting in downward vertical gradients with a potential for discharge of tailings water into the shallow aquifer system. Ground water quality in the shallow lacustrine unit is Class III Limited Use and Class IV Saline Ground Water, with TDS values up to approximately 70,000 mg/l in the vicinity of the Great Salt Lake. Following the issuance of the Tailings Impoundment Groundwater Discharge permit in 1996, water quality around the Facility has changed, with some wells exhibiting long-term increasing trends and others exhibiting decreasing trends in TDS, metals, sulfate, and dissolved ions. Factors which may influence changes in water quality around the facility include lower lake levels, increased facility hydraulic head, settling of the impoundment, integrity of facility discharge minimization designs over time, and changes to regional groundwater flow system. Background Ground Water QualityAssessing background ground water quality is a complex task for the area around the Facility because several complicating factors impede measurement or estimation of true background. The abandoned Morton Salt operation and the Chevron Phosphate operation are within the footprint of the North Impoundment. These operations may have impacted ground water quality and may complicate the ability to observe impacts from tailings. In addition, given the nearly century-long history of operations, impacts from the Facility have probably already occurred. Considering the aforementioned complicating factors, Ground Water Protection Levels for the Permit are established using existing ground water quality on a well-by-well basis. This approach ensures that the existing ground water quality will be protected by not allowing significant degradation from existing concentrations. Several compliance monitoring wells are relatively close to the bedrock contact and indicate Class II ground water quality. These wells are assigned protection levels consistent with Class II ground water. Ground water in the majority of the compliance monitoring wells is classified Class III ground water and they are assigned protection levels consistent with this classification. Compliance wells completed in Class IV ground water are assigned protection levels equal to the greater of the Utah Ground Water Quality Standards or the background value plus two standard deviations, with the exception that TDS limits are not imposed for Class IV Saline ground water. The basis for assigning protection levels (except TDS) to Class IV waters that are in close proximity to the Great Salt Lake is to protect wetland systems that exist in proximity to the lake and serve as habitat for shore birds and other aquatic species. These protections levels also ensure monitoring and protection for Class IV ground water from degradation due to constituents other than dissolved ions and TDS, such as dissolved metals. Background concentrations of arsenic in excess of Utah Ground Water Quality Standards have been observed in the Principal and Shallow Aquifer in the Tailing Impoundment area. In most of the Class III and Class IV wells, the background value for arsenic exceeds the Ground Water Quality Standard of 0.05 mg/l. Protection levels for arsenic were established in accordance with Utah Admin. Code R317-6-6.7. Sample results from these wells routinely exceed the background value due to normal variation around the mean; probable out of compliance is defined by concentrations which exceed the ground water protection levels listed in Permit UGW350011 Table 1. Permittee conducts Synthetic Precipitation Leaching Procedure (SPLP) analyses of tailings material to describe the toxicity of the tailings. SPLP analysis has not revealed any toxicity concerns. The interstitial waters in the tailings have been characterized and do not appear problematic to the water quality of aquifers underlying the Facility. To assure that the waste streams deposited into the Facility do not contain materials that differ markedly from those waste streams that have been characterized, the Permit identifies those waste streams at Part I.D (Permitted Inflow Waste Streams). There is a provision that allows Permittee to request a variance from this standard for incidental situations that would not impact overall water quality of aquifers underlying the Facility. Compliance Monitoring ProgramThe facility has been designed to employ discharge minimization and control technology with groundwater monitoring to prevent any impairment of present and future beneficial uses of the groundwater. Ground water monitoring is the primary compliance monitoring method for the Facility. Permittee performs general monitoring of the well network to develop a data base and identify ground water quality trends. Compliance monitoring is performed at selected wells located outside the impoundment footprint. Most monitoring wells are situated to characterize the influence of the tailings disposal on groundwater. Compliance monitoring wells are listed in Table 1 of the Permit. A semi-annual compliance monitoring program is required by the Permit. Protection Levels have been established following the specific rule of Utah Admin. Code R317-6-4. The following parameters were selected for compliance monitoring based on their high concentrations in the process water compared to concentrations in shallow ground water: Alkalinity Calcium Chloride Dissolved Metals Magnesium Potassium Sodium SulfateTDSThe compliance monitoring well network is currently comprised of multiple well locations. Most locations contain nested or paired wells: one screen interval in the upper Shallow Aquifer and one screen interval completed in the Principal aquifer. A few wells were installed with a C completion which is deeper than the initial Principal Aquifer completion. The perimeter of the South and North Impoundment is approximately 14 miles long. The multiple locations comprise a well frequency of about one well location per mile of embankment. Compliance monitoring wells will be relocated to the perimeter of the proposed ETE due east of the existing placement consistent with the existing facility. Permittee utilizes a discharge minimization approach and ground water monitoring to assess if any impacts occur. Discharge minimization is achieved by utilizing a natural clay beneath the Facility to impede the downward flow of tailings waters. The clay consists of the upper portion of the Bonneville Clay, which has been mapped at an average thickness of 8 feet and is continuous throughout the approximate 10,000-acre area of the South Impoundment, North Impoundment, and ETE. Measured vertical hydraulic conductivities for this segment of the Bonneville Clay range from 3 x 10-7 cm/sec to 4 x 10-8 cm/sec, which meets the requirements of Utah Admin. Code R317-6-6.4(A)(3) and (C)(3). Potential Impacts to Water QualityThe tailings facility is located on the Bonneville clay in a regional groundwater discharge area which are both barriers to contaminant transport in preventing groundwater impacts. However, there is still a need to evaluate potential impacts to the shallow groundwater. As the impoundment is continuing to be raised as planned, DWQ requestsa calculation of the depth of equilibrium for the impoundment hydraulic head and upward groundwater flow as is referenced in the November 5, 1993 Tailings Impoundment Groundwater Discharge Permit Application. Understanding the downward hydraulic pressure of the impoundment relative to the upward pressure of groundwater is necessary. The average concentrations of common constituents in the key waters associated with the tailings when compared to the concentrations in the Shallow and Principal Aquifers are summarized in Table S-1 of this Statement of Basis document.While the concentrations in Table S-1 are average values and some individual values may vary significantly, it is anticipated that the overall water quality of the Shallow and Principal Aquifers will not be degraded by water from the impoundment. Water from the impoundment will continue to be sampled semi-annually throughout the term of the Permit to provide a check on the quality of the water.One of the most important technical issues associated with the Facility is the long-term potential for acidification of the tailings materials. The chemical reactions associated with oxidation of sulfides results in production of acid, which if not neutralized could, over time, acidify the tailings materials. Should this happen, leaching of metals and other constituents that are not mobile in neutral pH conditions may occur.Permittee conducts static and kinetic testing of tailings materials to predict the potential for the tailings to acidify over time. Results to date indicate a low potential for the fine fraction tailings (overflow) to become acidic. The coarse fraction (underflow) can acidify under conditions mentioned above. To assure that signs of acidification are not occurring through the life of the impoundment, Permittee is required to monitor the interstitial water within the tailings and to perform analysis of the copper tails inflow to the Facility on a semiannual basis. Surface sites on the impoundment exterior are also sampled and analyzed for acidification potential on a semi-annual basis.The North Impoundment covers the abandoned Chevron Phosphate operation, which left a phosphogypsum tailings pile (gypstack) in the northwestern corner of the expanded impoundment. Downward hydraulic gradients could move gypstack pore fluids into the Shallow Aquifer and toward the toe drain. Hydraulic conductivity modeling has estimated a very slow rate of travel in the mine tailings and aquifer. The area is underlain by the Bonneville Clay. Two monitoring well pairs were installed to detect effects, if any, from burial of the phosphogypsum tailings. These wells have many years of background monitoring to establish background levels of radionuclides. Monitoring frequency occurs once every five years, until such time that detections of radionuclides and uranium may exceed Utah Ground Water Quality Standards.Some constituents which the permittee monitors for compliance can have natural sources, like the Great Salt Lake or the former evaporation salt mining operations, which existed in the footprint of the current Facility. If an out-of-compliance status exists for a well and the constituent which has exceeded its protection level has the potential for a natural source, Permittee may submit a permit modification request with Permittee’s Source Assessment, which documents and explains how the exceedance is the result of a natural change. The Division will review the Source Assessment and request for modification on a well by well basis, with the Director determining if a new protection level is granted based on a review of the data.Permit Reference Documents Assessment of Acidification Potential v.20 Compliance and Operational Monitoring Plan v.20 Pipeline Inspection Plan v.2017Table S-1Water Quality Summary of Aquifers and Potential SourcesConstituent Mean Concentrations in Bedrock Aquifer1,5Average Concentrations in Shallow Aquifer1Average Concentrations in Principal Aquifer2Average Concentrations in Tailings Pore Waters 3Average Concentrations in Clarification Canal 4pH 7.257.57.6 6.937.38TDS 1,77922,373 6,573 5,6157,941Sulfate 3971,9003601,5812,958Arsenic 0.0160.0430.071 0.1070.028Barium 0.0660.137 0.1270.0160.099Cadmium 0.0020.002 0.0010.0040.006Chromium 0.0070.0040.004 <0.01<0.01Copper 0.0160.118 0.032 1.4690.028Lead 0.0020.0010.001 0.0050.007Selenium 0.0050.005 0.006 0.0130.012 Silver <0.002 0.002 0.001 <0.005 <0.005Zinc 0.0230.022 0.022 0.2440.038All concentrations in mg/l 1, 2 Arithmetic mean concentrations are based on available analyses from permit origination 1995. The mean incorporates non-detections, assuming that the reporting limit is the concentration.3 Tailings pore water is represented by 5 Kennecott South Tailings operational, wells(NET2596, TLT887, TLT2452, TLT2575A, TLT2575B ) inception through 2021. 4 The clarification canal is represented by Kennecott sample location CLC452average 2006-2021.