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Home My WebLink AboutDERR-2024-004390 24001739.001A/SLC23L159279 Page 1 of 2 October 12, 2023 © 2023 Kleinfelder www.kleinfelder.com 849 West Levoy Drive, Suite 200, Taylorsville, UT 84123‐2544 p | 801.261.3336 October 12, 2023 Kleinfelder Project No.: 24001739.001A Mr. Doug Young SOJO118, LLC 6150 South Redwood Road, Suite 150 Taylorsville, UT 84123 Ms. Mazie Cox Environmental Scientist Utah Department of Environmental Quality Division of Environmental Response & Remediation 195 North 1950 West Salt Lake City, UT 84116 SUBJECT: Addendum No.1 to Final Soil Management Plan Bastian Ditch Shallow Flood Plain Soils Olympia Development Unincorporated Salt Lake County, UT Dear Doug and Mazie: This letter presents an alternative procedure for addressing soils impacted with elevated concentrations of arsenic and/or lead at the Olympia Development located within the Kennecott Operable Unit (OU) 5. At the time the original Soil Management Plan (SMP) was prepared, the remediation plan included shallow soil mixing to reduce levels of lead and arsenic to concentrations below the Unrestricted Land Use Standard prior to placing the soil back into the excavation as fill material. Since the SMP was approved and initiation of Site work, the soils have increased in moisture content to the point where soil mixing will not be effective to meet remediation targets. As discussed in our phone calls on October 9 and 11, 2023, the remediation plan for the shallow soils has changed to excavating the impacted soils and relocating these soils to parcels within the Olympia Development that are designated as open spaces or parks; therefore, the SMP requires an addendum to address this change. This addendum updates Section 1.4 to change the proposed remedial action to soil excavation and on‐site relocation, replaces the procedures presented in Section 4.2 relative to soil removal, and replaces the sampling procedures presented in Section 5.2 to present details for stockpile characterization sampling. These updates are presented in the following sections. Section 1.4 – Proposed Remedial Action and Regulatory Decisions Due to increasing moisture content and the fine‐grained nature of the soil present within the Bastian Ditch Shallow Flood Plain, the previously approved remediation strategy of soil mixing is no longer considered an effective method to remediate the shallow soils. Based on the results from previous site investigations, the concentrations of lead and arsenic are below the OU 5 Recreational Land Use Standards (283 milligrams per kilogram [mg/kg] – arsenic and 2,207 mg/kg – lead); therefore, it is 24001739.001A/SLC23L159279 Page 2 of 3 October 12, 2023 © 2023 Kleinfelder www.kleinfelder.com KLEINFELDER 849 West Levoy Drive, Suite 200, Taylorsville, UT 84123‐2544 p | 801.261.3336 proposed to excavate the impacted shallow soils and relocate them to parcels within the Olympia Development that are designated as open spaces or parks. Cleanup activities for other metals‐impacted areas within the Olympia Development, including the Bastian Ditch channel, will be addressed in future soil management plans. Section 4.2 – Impacted Soil Excavation Shallow soils within the Bastian Ditch flood plain with lead and/or arsenic concentrations greater than the Unrestricted Land Use Standards (50 mg/kg – arsenic and 500 mg/kg – lead) will be excavated from within the floodplain footprint. Soil excavation will be accomplished by removing the impacted soils and placing them in temporary stockpiles with heavy equipment such as a grader, dozer, or a track hoe fitted with a flat blade. The stockpiles will be sampled for laboratory analysis of total lead and arsenic concentrations to confirm compliance with the Recreational Land Use standards. The post‐removal ground surface will be field screened using an x‐ray fluorescence (XRF) analyzer and sampled to confirm removal of the impacted soil. When laboratory analytical results indicate the stockpiled soils meet the Recreational Land Use Standards, the soils will be transported and spread on the ground surface within the areas designated as open spaces or parks. As indicated in the approved SMP, the coordinates of the shallow impacted‐soil footprint were identified during Kleinfelder’s Phase II investigation. Those coordinates will be used to locate the impacted soils in the field with the aid of a hand‐held global positioning system (GPS) unit. Excavation of shallow soils will not extend into the Bastian Ditch channel and will not encroach within 10‐feet of the former ditch alignment. As the impacted soils are removed, field personnel will monitor the freshly exposed ground surface to direct the impacted soil removal. Soils with XRF readings indicating the metals concentrations are likely to exceed the applicable cleanup action level (i.e. with metals concentrations greater than 70% of the Unrestricted Land‐Use Standards—350 mg/kg lead and 35 mg/kg arsenic), will be considered “impacted” and removed and placed in temporary stockpiles. This method will identify the depth extent of soils with elevated metals in those areas where the depth extent has not yet been fully characterized and allow for their removal. Soil removal and stockpiling will continue vertically and horizontally within the floodplain until concentrations remaining on the freshly exposed ground surface are less than 70% of the Unrestricted Land Use level, based on XRF readings. Field personnel will communicate with the excavator operator regarding areas that require soil removal based on XRF readings. Pin flags, lathe, paint, or other tools may be used to mark the ground surface to visually indicate whether XRF readings are above or below the removal action levels. Soil that is temporarily stockpiled pending receipt of analytical results will be stabilized using water or other soil stabilizer to mitigate dust generation. The stockpiled soils will be placed directly onto the ground surface; the soil below the stockpiles will be over‐excavated by a minimum of 6 inches when the stockpile is removed to ensure all impacted soil is accounted for. 24001739.001A/SLC23L159279 Page 3 of 3 October 12, 2023 © 2023 Kleinfelder www.kleinfelder.com KLEINFELDER 849 West Levoy Drive, Suite 200, Taylorsville, UT 84123‐2544 p | 801.261.3336 Section 5.2 – Characterization Soil Sampling In order to confirm that the stockpiled soils meet the Recreational Land Use Standards, characterization samples will be collected for laboratory analysis. Due to the total volume of soil to be excavated (approximately 25,000 cubic yards), characterization samples will be collected at a rate of one sample per 250 cubic yards and will consist of a composite sample comprised of 10 aliquots. Each aliquot will be collected at random locations across the soil stockpile and at a depth of approximately 6‐inches below the surface of the stockpile. The stockpile characterization samples will be analyzed for total lead and arsenic, using EPA method SW846‐6010. Sample handling, labeling, and documentation will be conducted in accordance with the SOPs included in the approved SMP. Please do not hesitate to contact me if you have any questions or concerns with the amended procedures. Sincerely, KLEINFELDER Mike Gronseth, PE, PG, PMP Senior Project Manager