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Home My WebLink AboutDERR-2024-010537 SITE INSPECTION WORK PLAN 900 South 200 West Solvents Salt Lake County, Utah UTN000821040 February 2023 SITE INSPECTION WORK PLAN 900 South 200 West Solvents Salt Lake County, Utah UTN000821040 Utah Department of Environmental Quality Division of Environmental Response and Remediation Prepared by: Wes Sandlin Approved: _______________________________________ Date: _________ Wes Sandlin, Project Manager Approved: _______________________________________ Date: _________ Thomas Daniels, Site Assessment Section Manager Approved: _______________________________________ Date: _________ Ryan Dunham, Site Assessment Manager, EPA Region 8 . ' 4 ) ' $ ) — 4 @ G v A ? A B @ D w @ F ˜05/18/2023 05/18/2023 05/23/2023 Site Inspection Work Plan i 900 South 200 West Solvents – UTN000821040 TABLE OF CONTENTS 1.0 INTRODUCTION ................................................................................................................................. 1 2.0 OBJECTIVES ....................................................................................................................................... 1 3.0 BACKGROUND INFORMATION..................................................................................................... 1 3.1 Site Location and Description ............................................................................................................ 1 3.2 Site History and Previous Investigations ............................................................................................ 2 3.3 Physical Conditions ............................................................................................................................ 4 3.3.1 Hydrogeology .............................................................................................................................. 4 3.3.2 Hydrology .................................................................................................................................... 4 3.3.3 Geology ....................................................................................................................................... 4 3.3.4 Meteorology ................................................................................................................................ 5 4.0 PRELIMINARY PATHWAY ANALYSIS ........................................................................................ 5 4.1 Waste/Source Characteristics ............................................................................................................. 5 4.2 Groundwater Pathway Analysis ......................................................................................................... 6 4.2.1 Groundwater Pathway Data Gaps ............................................................................................... 6 4.3 Soil and Subsurface Vapor Intrusion Pathway Analysis .................................................................... 6 4.3.1 Subsurface Vapor Intrusion Pathway Data Gaps ........................................................................ 6 4.4 Surface Water Pathway Analysis ....................................................................................................... 7 4.5 Air Pathway Analysis ......................................................................................................................... 7 5.0 FIELD PROCEDURES ........................................................................................................................ 7 5.1 Concept of Operations ........................................................................................................................ 7 5.1.1 Schedule of Work ........................................................................................................................ 8 5.1.2 Safety ........................................................................................................................................... 8 5.1.3 Site Access and Logistics ............................................................................................................ 8 5.2 Sampling Locations ............................................................................................................................ 8 5.3 Sampling Methods .............................................................................................................................. 9 5.3.1 Soil Gas Sampling ....................................................................................................................... 9 5.3.2 Groundwater Sampling ................................................................................................................ 9 5.4 Investigation Derived Waste ............................................................................................................ 10 5.5 Analytical Parameters ....................................................................................................................... 10 6.0 QUALITY CONTROL PROCEDURES .......................................................................................... 10 7.0 CHAIN-OF-CUSTODY ..................................................................................................................... 10 8.0 DATA REDUCTION, VALIDATION, AND REPORTING .......................................................... 10 9.0 REFERENCES .................................................................................................................................... 11 Site Inspection Work Plan ii 900 South 200 West Solvents – UTN000821040 LIST OF FIGURES Figure 1: Site Location Figure 2: Detailed Site Map Figure 3: Conceptual Site Model Figure 4: Proposed Sampling Locations LIST OF TABLES: Table 1: Data Quality Objectives Table 2: Sample Locations, Descriptions, and Rationale Table 3: Sample Analysis Checklist LIST OF APPENDICES Appendix A: Site Health and Safety Plan Appendix B: Consent for Access to Property Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 1 1.0 INTRODUCTION Under authority of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, the Superfund Amendments and Reauthorization Act (SARA) of 1986, and in accordance with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), the Utah Department of Environmental Quality (UDEQ), Division of Environmental Response and Remediation (DERR) has prepared this Abbreviated Site Sampling Work Plan (Work Plan) as part of the Site Inspection (SI) of the 900 South 200 West Solvents site, UTN000821040, (herein referred to as the “Site”) in Salt Lake City, Salt Lake County, Utah. This SI will be conducted under a cooperative agreement between the DERR and the United States Environmental Protection Agency, Region 8 (EPA). The DERR completed a Preliminary Assessment (PA) for 900 South 200 West in May 2021. This PA was initiated because chlorinated solvents, including tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene (1,1-DCE), cis-1,2-dichloroethene (cis-1,2-DCE), trans-1,2-dichloroethene (trans-1,2-DCE), and vinyl chloride (VC) have been detected in soil, groundwater, indoor air, and soil gas at the Site since 1999. Information used to prepare this Work Plan was obtained from the PA report, field observations during site visits, and from additional sources cited within this document. 2.0 OBJECTIVES The findings outlined in the subsequent report will provide information to help support decisions regarding the need for further action at the Site. The specific objectives of this Work Plan are to: • Collect additional Site information, including sampling data necessary to fill observed data gaps regarding Site contamination; • Identify the levels of chlorinated solvents in groundwater, soil gas, and indoor air at businesses and residences near the Site; • Identify potential targets that may be affected by Site contamination, as well as other targets that may be impacted by the migration of the contamination via the suspected exposure pathways; and • Determine if continued assessment work under CERCLA or other authority is warranted. 3.0 BACKGROUND INFORMATION Information pertaining to the history and current status of the Site was obtained from the Preliminary Assessment - 900 South 200 West Solvents (Sandlin 2021), several historical reports, and various field observations. 3.1 Site Location and Description The Site is located in a mixed-use urban setting within Salt Lake City, Salt Lake County, Utah that contains both residential and commercial real estate (Figure 1). The approximate center of the Site is located at 40.7494047 N, 111.896997 W. The Site includes a vacant, former dry- cleaning facility (the Facility) at 906 South 200 West (now demolished), and nearby parcels along West 900 South Street, 200 West Street, Washington Street, and 300 West Street (Figure Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 2 2). The Site is bordered to the south and southwest by residential developments. The intersection at 900 South 200 West houses a Utah Transit Authority TRAX rail line and passenger station. Other nearby properties include single family homes, coffee shops, restaurants, and other small businesses. 3.2 Site History and Previous Investigations The lot at 906 South 200 West is currently vacant but operated as a large dry cleaning facility from 1920‒2015 when the most recent occupant, Henrie’s Dry Cleaners, closed (Weston Solutions, Inc. 2016a; Wasatch Environmental, Inc. 2018b; Weston Solutions, Inc. 2016b). Two underground storage tanks (USTs) containing a dry-cleaning solvent mixture (Stoddard solvent) and an oil-water separator were previously used at the Facility. Those tanks were found to be leaking and were removed in 1990 along with impacted soil in 1992 (SITEX Environmental, Inc. 1992; Wasatch Environmental, Inc. 2018b; 2018b). The Preliminary Site Cleanup Report by Sitex Environmental, Inc. (SITEX Environmental, Inc. 1992) documented that minor residual ethylbenzene and xylene contamination remained following the excavation and off-site disposal of soil contaminated with Stoddard solvent. The leaking underground storage tank (LUST) release was granted regulatory closure in 1996. During a 1999 Phase II Subsurface Investigation, Granite Environmental, Inc. collected a soil sample on the Facility property that contained PCE at a concentration of 300 µg/kg. This sample was the first confirmation of a chlorinated solvent release and impact at the Facility. Since then, the Facility has been assessed through a series of environmental sampling initiatives conducted by several environmental firms, including the following: • Environmental Resources Management (ERM) prepared an unpublished Indoor Air Sample Analytical Summary in 2015. • Weston Solutions, Inc. (Weston) prepared a Phase I Environmental Site Assessment in August 2016. • Weston prepared an Updated Phase I Environmental Site Assessment in April 2017. • Weston prepared a Phase II Environmental Site Assessment Addendum in March 2017. • AECOM Technical Services, Inc. prepared an Additional Subsurface Investigation in May 2017. • Wasatch Environmental, Inc. (Wasatch Environmental) prepared a Potential Tetrachloroethene Source Area Report in April 2018. • Wasatch Environmental prepared a Phase I Environmental Site Assessment in May 2018. • Wasatch Environmental prepared a Source Area Investigation in May 2018. • Wasatch Environmental prepared an Additional Site Characterization Report in April 2019. • Wasatch Environmental prepared an Additional Site Characterization Report in September 2020. These studies identified chlorinated solvents within soil, groundwater, and soil gas at concentrations exceeding relevant U.S. EPA Regional Screening Level (RSL), Maximum Contaminant Level (MCL), and Vapor Intrusion Screening Level (VISL) benchmarks. Wasatch Environmental identified two source areas for chlorinated solvent contamination at the Facility Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 3 (Wasatch Environmental, Inc. 2018c). A smaller source area (North Source Area) was identified in association with the Stoddard solvent UST basin near the northwest corner of the Facility, and a larger source area (South Source Area) was identified in association with a drum storage area and dry cleaning equipment located near the west-central portion of the Facility (Figure 2) (Wasatch Environmental, Inc. 2018c; 2020). Groundwater samples collected at the Facility between April 2018 and June 2020 measured PCE, TCE, 1-1,DCE, cis-1,2-DCE, trans-1,2-DCE, VC, and benzene at concentrations exceeding MCLs by wide margins (Wasatch Environmental, Inc. 2020). Additionally, these concentrations exceeded residential VISL target groundwater concentrations, which are groundwater concentrations that could theoretically produce hazardous indoor air conditions based on specific chemical properties. Furthermore, groundwater samples collected from properties to the west of the Facility measured PCE, TCE, cis-1,2-DCE, and VC above MCLs and residential VISL target groundwater concentrations (AECOM Technical Services, Inc. 2018; Wasatch Environmental, Inc. 2020)—indicating that the contaminant plume is migrating from the Facility to nearby residential and commercial properties. Soil samples collected near the South Source Area in 2018 and 2019 measured PCE and TCE at concentrations exceeding RSLs for industrial soils (Wasatch Environmental, Inc. 2020). Benzo(a)pyrene was detected above the RSL for residential soils in 2017 (Weston Solutions, Inc. 2017a). Soil gas samples collected near the north and south end of the Facility measured PCE, TCE, VC, chloroform, and benzene above residential VISL target sub-slab/near-source gas concentrations, which are soil gas concentrations that could theoretically produce hazardous indoor air conditions based on specific chemical properties (Weston Solutions, Inc. 2017a). Additionally, soil gas samples collected approximately 75 feet (ft) to the south and southwest of the Facility measured chloroform above the residential VISL target sub-slab/near-source concentration (Wasatch Environmental, Inc. 2019). Indoor air samples collected from the Facility in 2015 measured PCE above the commercial indoor air RSL (ERM 2015). The property at 906 South 200 West was in the Voluntary Cleanup Program (VCP) from 2018‒ 2019 when the applicant, Urban 9th, LLC, withdrew from the program and sought oversight and regulation through the DWMRC. In February 2021 the DWMRC approved a Corrective Action Plan (CAP) and Baseline Risk Assessment and Work Plan for the property, which includes in- situ soil mixing of the North and South Source Areas with zero-valent iron (ZVI), ZVI injection borings down to 59 ft below ground surface (bgs) at the North and South Source Areas, ZVI permeable reactive barriers from 9‒29 ft bgs along the northern, western, and southern boundaries of the property, and follow-up soil and groundwater sampling (Wasatch Environmental, Inc. 2021b; 2021a). The CAP will attempt to remediate contamination within the 906 South 200 West property boundary and reduce migration from the source areas; however, it will not be able to address the full extent of contamination across the Site. In 2021 the property at 906 South 200 West was sold to new developers whom are proceeding with the CAP. In June 2022 the in-situ soil mixing of the North and South Source Areas, the ZVI injections, and the installation of the permeable reactive barriers were completed. Follow-up soil sampling by Wasatch Environmental confirmed that contaminants in the North and South Source Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 4 Areas were measured below residential soil RSLs following remediation (Wasatch Environmental, Inc. 2022). Wasatch Environmental plans to take groundwater samples by the end of 2022 in order to measure the efficacy of the ZVI injections and the permeable reactive barriers. Presently, the Facility building has been demolished, and the property owners plan to proceed with the construction of a multi-story apartment complex housing commercial real estate on the ground floor. The 2021 PA concludes that chlorinated solvents have migrated from the Facility to neighboring properties and may put nearby workers and residents at risk to hazardous indoor air conditions as a result of soil vapor intrusion (Sandlin 2021). This SI Work Plan was prompted to delineate the current plume boundaries, identify potential targets, and assess the risk the soil vapor intrusion poses to properties near the Facility. 3.3 Physical Conditions 3.3.1 Hydrogeology Hydrogeology in the Salt Lake Valley generally consists of a relatively deep unconfined aquifer (principal aquifer) near the mountain fronts that becomes confined closer to the valley center due to relatively shallow deposits of silt and clay (Thiros 2003). The primary recharge area to the principal aquifer is along the Wasatch front, with secondary recharge available through the leakage of shallow groundwater where layers are thin and/or discontinuous. Shallow groundwater, either perched locally on top of confining layers or laterally continuous, forms a shallow aquifer in the valley. The distinction between shallow and deeper aquifers is not clear in the secondary recharge area. In the Salt Lake Valley, groundwater tends to flow from the Wasatch front, towards the Jordan River to the west, and subsequently to the Great Salt Lake to the northwest (Thiros 2003). Well logs and cone penetration tests conducted at the Site suggest there are at least three aquifers at the Site: a shallow aquifer (11‒15 ft bgs), an intermediate aquifer (20‒30 ft bgs), and a deep aquifer (50‒60 ft bgs). Hydraulic gradients are 0.015 ft/ft to the northwest for the shallow aquifer, 0.005 ft/ft to the west-northwest for the intermediate aquifer, and 0.002 ft/ft to the southwest in the deep aquifer (Wasatch Environmental, Inc. 2020). The intermediate and deep aquifers also have an upward vertical hydraulic component (Wasatch Environmental, Inc. 2020). 3.3.2 Hydrology The Site is situated in the northern portion of the Salt Lake Valley at an elevation of 4,246 feet above sea level, on relatively flat ground. Surface water at the Site is largely captured by an engineered urban storm water system that routes water to the Jordan River, about one mile to the west. From there, the Jordan River flows approximately 12 miles north to the Great Salt Lake. 3.3.3 Geology The Site resides near a geological contact of young floodplain and stream deposits (Quaternary age), and mixed lacustrine (lake deposits), alluvial (hillslope deposits), and marsh deposits (Quaternary age) (McKean 2020). These units include moderately- to well-sorted sands, silts, Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 5 clays, clayey silts, gravels, and pebbles (McKean 2020). Well logs from the Site corroborate this geology, describing interbedded layers of gravelly sands, coarse- to fine-grained sands, gravelly silts, and low- to non-plastic clays and silts. 3.3.4 Meteorology Salt Lake City normally has a semi-arid continental climate with four well-defined seasons (National Oceanic and Atmospheric Administration 2019). Summers are hot and dry with relatively low humidity (Western Regional Climate Center 2016). July is the warmest month, with an average maximum temperature of 92.8 ºF (Western Regional Climate Center 2016). Winters are cold, with average annual snowfall approaching 60 inches (Western Regional Climate Center 2016). January is the coldest month, with an average minimum temperature of 20.4 ºF (Western Regional Climate Center 2016). Average annual precipitation in Salt Lake City is 16.10 inches (National Oceanic and Atmospheric Administration 2019), with a two year 24- hour rainfall of 1.5 inches (Hershfield 1961). 4.0 PRELIMINARY PATHWAY ANALYSIS 4.1 Waste/Source Characteristics A former Stoddard solvent UST basin and a drum storage area at the Facility were identified as sources for chlorinated solvent contamination (Wasatch Environmental, Inc. 2018c; 2020). Visual inspections of the Facility reported cracked concrete floors, visible staining, and corroded iron sewer lines at the South Source Area, which may explain how contaminants were discharged to the subsurface. The chemicals of concern at the Site include PCE, TCE, 1-1,DCE, cis-1,2-DCE, trans-1,2-DCE, VC, and benzene. These chemicals are highly toxic chemicals that are known to have effects on organ functions, fetal development, and immune and nervous system function. Exposure to vapors may result in dizziness, headaches, nausea, unconsciousness, and death. Long-term exposure can cause liver and kidney damage. With the exception of cis-1,2-DCE, all of these substances are known carcinogens (Center for Disease Control 2021). Reductive dechlorination facilitated by the presence of petroleum hydrocarbons in the soil (naphthalene) may be occurring at the Site. TCE, DCE, and VC are all partial degradation products that can be produced as PCE is biodegraded under anaerobic conditions (Minnesota Pollution Control Agency 2006; Watts 2006). This explanation is consistent with currently available data and suggests that the concentrations of those degradation products, which are more hazardous than PCE alone, will continue to increase over time. The vertical and lateral extents of the contaminant source areas have been defined at the Site— existing locally, beneath the Facility, and contaminated soils were remediated in 2022 (Wasatch Environmental, Inc. 2020; 2022). The migration of contaminants within groundwater is ongoing and the current boundaries of the plume are undefined. Further investigation is required to delineate the plume and assess the risk that soil vapor intrusion poses to nearby workers and residents. Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 6 4.2 Groundwater Pathway Analysis There are ten municipal drinking water supply wells located within a four-mile radius of the site, serving three water supply systems with a total user population of 137,599. The municipal groundwater well closest to the Site is Salt Lake City’s 4th Avenue well, located upgradient ~1.8 miles north-northeast of the Site (Utah Division of Drinking Water 2019). The total completed depth of this well is 464 feet bgs. The closest downgradient well is the Taggart #16 well, located approximately 2.9 miles to the southwest. The depth of this well is 736 feet bgs. There are 1,479 known underground Points of Diversion (PODs) located within four miles of the Site; some of which list “domestic” as at least one of the well uses. The closest downgradient PODs are located 1.3 miles west of the Site (Utah Division of Water Rights 2020). Currently available data definitively indicates the presence of groundwater contamination and suggests the transport of contaminants through groundwater. Known drinking water resources are distant, and likely outside the range of this contamination. Downgradient PODs could potentially be impacted by the groundwater plume, but it is doubtful that the PODs are currently being used for drinking water, as municipal water is readily available. The primary concern is that contaminants in shallow groundwater may volatilize and expose targets via subsurface vapor intrusion. 4.2.1 Groundwater Pathway Data Gaps The lateral extent of groundwater contamination in the shallow, intermediate, and deep aquifers was defined in 2020; however, the migration of the plume is ongoing and current plume boundaries are undefined. In order to delineate the current boundaries of the groundwater plume and determine the risk of subsurface vapor intrusion to potential targets, additional groundwater sampling is needed at surrounding properties. 4.3 Soil and Subsurface Vapor Intrusion Pathway Analysis In 2022, contaminated soils from the two source areas were treated by in-situ soil mixing with ZVI and left in place in accordance with the Corrective Action Plan. Follow-up sampling by Wasatch Environmental determined that following treatment, the soil met residential RSLs (Wasatch Environmental, Inc. 2022). The risk of exposure to contaminants in the soil through dermal contact or ingestion are low. The primary pathway of concern at the Site is the subsurface intrusion of vapors from VOCs in groundwater plumes that have migrated to properties northwest, west, and southwest of the Facility. Once volatilized, VOCs can escape through interstitial spaces between soil particles and move upward through both soil and building materials, becoming concentrated in indoor air and harming the people who live or work in these conditions. The number of people living or working at nearby buildings is unclear, but approximately 3,163 people live within one-quarter mile of the Site and are potential targets to subsurface vapor intrusion (U.S. Census Bureau 2010). 4.3.1 Subsurface Vapor Intrusion Pathway Data Gaps Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 7 In 2019, Wasatch Environmental collected two subsurface soil gas samples—one to the south of the Facility and one to the southwest of the Facility—to assess the risk of subsurface vapor intrusion to nearby residents. Chlorinated solvents were detected well below residential target sub-slab/near-source VISLs at these locations (Wasatch Environmental, Inc. 2019). This data is very limited and may not reflect the current conditions across the Site. Further soil gas sampling is needed to determine the risk of subsurface vapor intrusion to potential targets. 4.4 Surface Water Pathway Analysis Surface water at the Site flows to nearby storm drains and runs about one mile west to the Jordan River, which then flows twelve miles north towards wetland areas and the Great Salt Lake. There are no surface-derived drinking water sources within 15 downstream miles (Utah Division of Drinking Water 2019). Portions of the Site fall within the 500-years flood hazard area (FEMA 2012). The likelihood of exposure to contaminants via surface water is low because surface water at the Site is ephemeral and not likely to interact with contaminant sources. 4.5 Air Pathway Analysis The Site area is largely covered with asphalt or concrete with little opportunity for persons to be exposed to contaminants through ambient air. The nearest residential buildings are located 25 yards to the south of the Facility, and new apartments are being constructed roughly ten feet west of the Facility. There does not appear to be an active or ongoing release at the Site through the air exposure pathway, and there is little potential for exposure to occur. 5.0 FIELD PROCEDURES 5.1 Concept of Operations Site sampling activities will comply with the Data Quality Objectives (Table 1) as described in the DERR Quality Assurance Project Plan (QAPP) (Palmer et al. 2020) and environmental sampling collection procedures as outlined in the EPA’s Contract Laboratory Program Guidance for Field Samplers (U.S. EPA 2014). A Conceptual Site Model has been completed to evaluate the potential pathways for contaminant migration and to assist in the selection of appropriate sampling locations (Figure 3). The scope of the investigation includes the advancement of nine direct-push borings for the collection of 10 soil gas samples (including one field duplicate), and the collection of up to 24 groundwater samples from fourteen existing monitoring wells and four temporary monitoring wells (including two field duplicates and three trip blanks). The proposed sample locations are shown in Figure 4. Any changes to proposed locations (due to access issues, etc.) will be documented in the field notes and noted in the analytical results report. For purposes of quality assurance/quality control (QA/QC), field duplicate samples will be collected from each matrix as an external check on laboratory procedures. Each day of sampling, a groundwater trip blank will be included as further QA/QC verification. Additional volumes of groundwater will be collected for internal laboratory QA/QC purposes. Since temporary and disposable sampling equipment will be used at each sampling location, a rinsate sample will not be necessary. All samples will be analyzed for VOCs. Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 8 5.1.1 Schedule of Work Sampling is tentatively scheduled to begin in Spring of 2023 and is expected to take four to five days to complete. The scheduling of sampling activities will be finalized upon EPA’s approval of this Work Plan. An initial reconnaissance of the Site will be conducted prior to the first day of the sampling event during which alternate sample locations may be determined. A 21-day turnaround for the sample analyses will be requested for the EPA Contract Laboratory Program (CLP) analytical services. 5.1.2 Safety Sampling personnel will be careful to avoid direct contact, dermal contact, inhalation, or ingestion of on-site materials. Proper safety protection will be worn at all times during sampling. Sampling will be conducted in Level D protective clothing. A Site Health and Safety Plan (HASP) has been prepared by the Project Manager and will be reviewed by all team members prior to going on-site. The HASP will be retained in the Site file in the DERR offices. A copy of the HASP form is included in Appendix A. All on-site personnel will meet the Occupational Safety and Health Administration (OSHA) training requirements and be qualified to work at uncontrolled hazardous waste sites. 5.1.3 Site Access and Logistics Site access and logistical functions will be arranged by the Project Manager in advance of sampling. Provisions for Site access will be arranged and the landowners will be asked to sign a DERR “Consent for Access to Property” form (Appendix B). Landowners will be notified of their right to obtain split-samples if requested. Coordination with the EPA contract laboratory and the local health department will be arranged prior to Site activities. Sampling equipment and supplies will be arranged by the Project Manager. The adjacent property to the west of the Facility is currently under construction and it is unclear how this will affect access to the proposed sample locations. Prior to the sampling event, the Project Manager will visit the Site to see if sample locations are accessible. If necessary, the Project Manager may move sample locations and will make note of the change in their field notes. The Project Manager will ensure that any change in location will not affect the ability of the sampling event to meet the Data Quality Objectives. 5.2 Sampling Locations A total of 10 soil gas samples and up to 24 groundwater samples will be collected in the field for this SI. A biased sampling approach using analytical data from previous reports was used to identify sample locations. Soil gas and groundwater samples will be collected from 906 South 200 West and nearby residential and commercial properties to delineate the groundwater plume and assess the risk the soil vapor intrusion poses to nearby residents and employees. A background sample for groundwater (MW-103) and soil gas (SG-02) will be collected at a location upgradient of the waste source areas to establish ambient soil gas and groundwater conditions. The selected soil gas and groundwater sample locations are shown in Figure 4. Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 9 Further description of the proposed sampling for the Site is included in the Tables section of this Work Plan. The following is a summary of the information presented in these tables: • Table 1 lists data quality objectives • Table 2 lists sample locations, descriptions, and rationale • Table 3 is a sample analysis checklist that indicates the laboratory parameters for the analyses of each sample 5.3 Sampling Methods 5.3.1 Soil Gas Sampling Prior to soil gas sampling, Blue Stakes of Utah will be called to locate subsurface utility lines. For soil gas collection, the drill rig will bore down to six feet bgs. Polyethylene or Tygon tubing will be placed down the boring and connected to an evacuated and metered vacuum canister. The hole will be sealed at the surface with wet bentonite or other inert material, and the sampling system will be purged of at least three sample chain volumes. Once purged, the canister will collect soil gas for one hour. The valves on the sample canisters will then be closed, and each canister will be labeled appropriately. Soil gas samples will be sent to a selected CLP laboratory and analyzed for VOCs in accordance with EPA Method TO-15. Following soil gas collection, each boring will be backfilled to the surface and any concrete or asphalt will be patched. Direct push drive probes, collection tubing, and vacuum canisters will be dedicated to each sampling location to prevent potential cross-contamination between locations. 5.3.2 Groundwater Sampling Groundwater sample collection from temporary monitoring wells will proceed after soil gas sample collection. The drill rig will proceed to 15 feet bgs. PVC wells will be inserted into the boring with wells screens from 5‒15 feet bgs. Coarse grained sand will then be poured between the well and the boring. Groundwater sample collection from existing monitoring wells may proceed before or after soil gas sample collection because the existing monitoring wells are not located close enough to the proposed soil gas sample locations to affect the integrity of soil gas samples. Groundwater sampling from all wells will utilize low-flow sampling and purging methods. A peristaltic pump and dedicated, disposable tubing at each sample location will be used. New high-density polyethylene (HDPE) tubing will be used for each well, the inlet of which will be placed within the top foot of the water column. Water quality parameters (pH, temperature, conductivity, and turbidity) will be measured using a Horiba U-51 Multiparameter Meter, calibrated prior to use according to manufacturer’s specifications. Using depth to water and total depth of well measurements, the casing volume of water for each well will be calculated. Wells will be purged until one of the following criteria is met: • Groundwater quality parameters of pH, temperature, conductivity, and turbidity readings have stabilized to within 10% over three consecutive readings; • Three casing volumes have been purged; or Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 10 • The well no longer produces. Groundwater samples will be conveyed in 40 mL amber glass vials sealed with a polypropylene or phenolic open-top screw cap and a PTFE septum, and preserved to a pH of 2 with hydrochloric acid. Each vial will be filled with no observable headspace or air bubbles to minimize the potential for volatilization, labeled for identification, and stored in an iced cooler to 4 degrees Celsius (4 ºC) after collection. Groundwater samples will be sent to a selected CLP laboratory and analyzed for VOCs in accordance with EPA Method 8260D. When all soil gas and groundwater collection is complete, all soil gas and temporary monitoring well borings will be backfilled to the surface with soil cuttings and/or bentonite, and any asphalt or concrete will be patched at the surface. 5.4 Investigation Derived Waste Disposable sampling equipment will be double bagged and disposed of as non-hazardous. Excess sample material will be returned to the sample location or disposed of according to accepted protocol. All hazardous materials generated, if any, will be disposed of in accordance with applicable federal, state, and local requirements, and in accordance with the U.S. EPA Office of Emergency and Remedial Response’s “Management of Investigation-Derived Wastes During Site Inspection” (U.S. EPA 1991) guidelines. 5.5 Analytical Parameters Chain-of-Custody forms will be developed using SCRIBE software. Samples will be shipped as environmental samples via strict chain-of-custody to a contract laboratory registered under EPA’s Certified Laboratory Program and analyzed under Routine Analytical Services for the target compound list constituents and media as listed in the Sample Analysis Checklist (Table 3). 6.0 QUALITY CONTROL PROCEDURES QA/QC samples will be collected as a check of proper sample collection, field decontamination procedures, and laboratory procedures. Samples will be handled and preserved as outlined in the QAPP (Palmer et al. 2020). Every effort will be made to ship samples to the laboratory the day after the field sampling activity. Samples collected from the Site for QA/QC purposes include field duplicates from each matrix, a groundwater trip blank prepared with de-ionized water before departure to the field each day, and laboratory matrix spike/matrix spike duplicates (MS/MSD) for groundwater. 7.0 CHAIN-OF-CUSTODY Samples will be handled and delivered to the CLP laboratory in accordance with chain-of- custody protocols within appropriate holding times as defined by the QAPP (Palmer et al. 2020). 8.0 DATA REDUCTION, VALIDATION, AND REPORTING The data package delivered from the CLP laboratory will be validated by an EPA contractor. Following receipt of the validated analytical data, the project manager will prepare the Site Inspection – Analytical Results Report (SI-ARR). The analytical data in the validation package Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 11 will be compared to the appropriate benchmark values in the Superfund Chemical Data Matrix, and background, or ambient, conditions. The project manager will prepare an assessment of whether the Site should be recommended for further action through CERCLA or alternate authority. All data and observations collected as part of this SI will be included in the draft SI- ARR and submitted to the EPA Region 8 for review and approval. 9.0 REFERENCES AECOM Technical Services, Inc. 2018. “Former Henrie’s Dry Cleaners, Additional Investigation Report, 906 South 200 West, Sat Lake City, Utah 84101.” Center for Disease Control. 2021. “Toxic Substances Portal | ATSDR.” 2021. https://wwwn.cdc.gov/TSP/index.aspx. ERM. 2015. “Unpublished Indoor Air Sample Analytical Summary Data Table and Sample Location Map, Henries Cleaners 906 South 200 West.” FEMA. 2012. “Digital Flood Insurance Rate Map, Salt Lake County and Incorporated Areas, Panel 282 of 625.” Hershfield, David M. 1961. “Rainfall Frequency Atlas of the United States for Durations from 30 Minutes to 24 Hours and Return Periods from 1 to 100 Years.” Technical Paper 40. Washington, D.C.: USDA. McKean, Adam P. 2020. Geologic Map of the Salt Lake City South Quadrangle, Salt Lake County, Utah. Utah Geological Survey. https://doi.org/10.34191/M-283DM. Minnesota Pollution Control Agency. 2006. “Guidelines: Natural Attenuation of Chlorinated Solvents in Ground Water,” 51. National Oceanic and Atmospheric Administration. 2019. “2019 Local Climatological Data Annual Summary with Comparative Data, Salt Lake City, Utah (KSLC).” Palmer, Elizabeth, Muhammad Slam, Kim Viehweg, and Joseph Katz. 2020. “Quality Assurance Program Plan for Environmental Data Operations for the CERCLA Branch, Final Plan - Revision No. 8.” Utah Division of Environmental Response and Remediation. Sandlin, Wes. 2021. “Preliminary Assessment - 900 South 200 West Solvents.” Salt Lake City, UT: Utah DERR. SITEX Environmental, Inc. 1992. “Preliminary Site Cleanup Report, Vogue Cleaning, 906 South 200 West, Salt Lake City, Utah.” Thiros, Susan A. 2003. “Hydrogeology of Shallow Basin-Fill Deposits in Areas of Salt Lake Valley, Salt Lake County, Utah.” https://doi.org/10.3133/wri034029. U.S. Census Bureau. 2010. “2010 U.S. Census Bureau Data.” Utah Automated Geographic Reference Center. Site Inspection Work Plan 900 South 200 West Solvents – UTN000821040 12 U.S. EPA. 1991. “Management of Investigation-Derived Wastes During Site Inspection.” ———. 2014. “Sampler’s Guide- Contract Laboratory Program Guidance for Field Samplers.” Washington, D.C.: Office of Superfund Remediation and Technology Innovation, U.S. EPA. Utah Division of Drinking Water. 2019. “Public Drinking Water Source Database.” Salt Lake City, UT: Utah Division of Drinking Water. Utah Division of Water Rights. 2020. “Water Rights Points of Diversion Database, Utah State Geographic Information Database Layer Name:Wrpad.Shp.” Wasatch Environmental, Inc. 2018b. “Phase I Environmental Site Assessment, Former Henries Dry Cleaning, 906 South 200 West, Salt Lake City, Utah 84104 [Sic].” ———. 2018c. “Source Area Investigation, Former Henrie’s Dry Cleaner, 906 South 200 West, Salt Lake City, Utah.” ———. 2019. “Additional Investigation Report, Edison Building, 933 South Edison Street.” ———. 2020. “Additional Investigation Report, Edison Building, 933 South Edison Street, Salt Lake City, Utah.” ———. 2021a. “Baseline Risk Assessment and Work Plan for the Phase II Risk Assessment - Former Henrie’s Dry Cleaner 906 South 200 West Salt Lake City, Utah.” ———. 2021b. “Corrective Action Plan, Former Henries Dry Cleaner, 906 South 200 West, Salt Lake City, Utah (Under Review).” ———. 2022. “Contained-Out Request - Henries 9th South.” Utah DWMRC. Watts, Peter. 2006. Tetrachloroethene. Concise International Chemical Assessment Document 68. Geneva: World Health Organization. Western Regional Climate Center. 2016. “SALT LAKE CITY INTL AP, UTAH - Climate Summary.” 2016. https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?ut7598. Weston Solutions, Inc. 2016a. “Phase I Environmental Site Assessment for Henrie’s Dry Cleaners, 906 South 200 West, Salt Lake City, Utah, 84101.” ———. 2017a. “Phase II Environmental Site Assessment Addendum for Henrie’s Dry Cleaners, 906 South 200 West, Salt Lake City, Utah.” ———. 2016b. “Phase II Environmental Site Assessment for Henrie’s Dry Cleaners, 906 South 200 West, Salt Lake City, Utah.” FIGURES TABLES APPENDIX A Site Health and Safety Plan APPENDIX B Consent for Access to Property