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g. �M Appendix A. Responsiveness Summary Martin Metals Finishing Inc. (Former) Stockton, California Response to Department of Toxic Substances Control (DTSC) Comments for CDIM's Preliminary Endangerment Assessment (PEA) and Supplemental Site Investigation (SSI)Work Plan (Work Plan), Martin Metal Finishing Inc. Stockton California, dated July 25, 2022. Comment I Response Andrew Leavitt, P.G., Senior Engineering Geologist, Geological Services Branch (GSB)—PEA Comments 1. The GSB generally agrees with the findings and Comment acknowledged. conclusions of the PEA. The limited analytical data collected between 1984 and 1989 suggest the potential for an unauthorized release of COPCs as a result of MMF's historical on-Site operations. 2. The GSB also concurs with CDIM's conclusion Comment acknowledged. that MMF's historical on-Site operations included the use of solvents, and therefore, a potential vapor intrusion threat exists from impacted soil vapor for the existing on-Site building. 3. Page 13, Section 2.8—CDIM's third conclusion in These conclusions are not included in the PEA Work the PEA states, "Based on a review of historic data Plan, and the conclusion addressed in this comment (Table 2)and limited receptors (Section 2.6), the will be reassessed in the PEA Report following the past releases do not appear to pose a threat to collection of new data. public health or the environment." Upon review of the analytical table for sediment and soil presented in Table 2, the GSB does not agree with this conclusion. • For total chromium, copper, and zinc, the DTSC's Human and Ecological Risk Office (HERO) Note 3 does not currently have a screening level (SL). In lieu, CDIM evaluated concentrations of these three metals against Terrestrial Habitat ESLs. Several detected concentrations of all three metals exceed these ESLs. This would indicate that there is a threat to the environment. It should be noted that the GSB recommends using the DTSC's HERO Note 3 SLs going forward. • Three of detected concentrations of lead in sediment and soil exceed the DTSC's HERO Note 3 SL of 320 mg/kg. This indicated a potential threat to both human health and the environment. Additionally, several sludge samples contained elevated concentrations of lead. While there is no SL established for"sludge,"the potential exists Page A-2