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January 31, 2024 <br />Risk-Based Evaluation for Reuse of Stockpile Material for the Proposed Treatment <br />Wetland Project – City of San Leandro Water Pollution Control Plant <br /> <br /> 20240131-Terraphase-SanLeandro-TreatmentWetland-Risk-TM-DRAFT.docx Page 9 of 10 <br /> <br />exposure to lead in the stockpiled soil, alone, during construction of the treatment wetland would not <br />result in blood lead concentrations that would exceed CalEPA DTSC’s risk management goal. The <br />exposure concentration for sludge is slightly higher than this screening level indicating that construction <br />worker exposure to lead in sludge, alone, during construction may result in blood lead concentrations <br />that could exceed CalEPA DTSC’s risk management goal. <br />The exposure duration of the Project is assumed to be approximately 6 months. This corresponds to an <br />exposure frequency of 125 days. As noted by USEPA (2016), a constant lead intake rate over a duration <br />of 90 days is needed to achieve a blood lead concentration that is sufficiently close to steady-state. <br />Infrequent and non-continuous exposures to lead would not be expected to result in adequate exposure <br />to attain blood lead concentrations that would be of concern. Given the specifics of this Project, it is <br />reasonable to assume that only about half of a construction worker’s exposure will be to sludge (e.g., <br />~60 days of exposure). As a result, while the lead exposure concentration in sludge is greater than <br />CalEPA DTSC’s screening level of 500 mg/kg, the exposure of a construction worker to this specific- <br />media would not be of a long-enough duration to result in a blood lead concentration that would be of <br />concern. Further, the exposure concentration estimated assuming exposure to lead in both stockpiled <br />soil and sludge (combined) is 440 mg/kg. This concentration is less than the screening level of <br />500 mg/kg. <br />Overall, these results demonstrate that lead concentrations in stockpiled soil and sludge will not pose an <br />unacceptable lead exposure to workers supporting the construction of the Project. <br />References <br />California Environmental Protection Agency (CalEPA), Department of Toxic Substances Control (DTSC). 2015. <br />Preliminary Endangerment Assessment Guidance Manual. October. <br />_____. 2019a. Recommended DTSC Default Exposure Factors for Use in Risk Assessment at California Hazardous <br />Waste Sites and Permitted Facilities. April 9. <br />_____. 2019b. HERO HHRA Note Number: 10, Toxicity Criteria. February 25. <br />_____. 2022a. HERO HHRA Note Number: 4, Guidance for Screening Level Human Health Risk Assessments. <br />March 29. <br />_____. 2022b. HERO Lead Spread 9 – Information for Users. March. <br />California Environmental Protection Agency (CalEPA), Office of Environmental Health Hazard Assessment (OEHHA). <br />2020. Cancer Risk and Noncancer Hazard Index – Fact Sheet for Contaminated Sites in California. November. <br />Fugro Consultants, Inc. 2016. Water Quality Assessment, WCPC Contaminated Soil Relocation Project, San Leandro <br />Water Pollution Control Plant, San Leandro, California. May 19. <br />Jones C.A., and C.N. Baxter. 2004. Thomomys bottae (Rodentia: Sciurognathi). Mammalian Species. 742:1-14. <br />LSA. 2020a. Biological Assessment. San Leandro Treatment Wetland Project for Pollution Reduction, Habitat <br />Enhancement, and Shoreline Resiliency. San Leandro, Alameda County, California. Submitted to City of San <br />Leandro Public Works – Water Pollution Control Plant. Prepared by LSA, Pt. Richmond, California. Project No. <br />TER2001. March 2020.