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Ms. Elena Reyes, City Manager January 10, 2017 City of Manteca Page 2 of 3 Former Police Firing Range (DTSC) to evaluate arsenic as a COPC; arsenic concentrations exceeding 12 mg/kg will trigger establishment of a site-specific background concentration. Mr. Richard Day (email dated November 23, 2016) indicated that background concentrations would be determined for this site and excavation confirmation samples will meet or be less than background and RSLs; the EHD approves the latter regarding arsenic. The soil removal action will address soil identified in Geocon's SIR, as exceeding the 80 mg/kg cleanup goal for lead-impacted soil. The proposed excavation margins are as defined on Figure 3 in the SIR, which depicts the areas with soil identified as California hazardous waste for lead surrounding the area with soil identified as RCRA hazardous waste for lead. The remedial action will entail excavation of soil on the firing range floor to a depth of 1.5 feet below surface grade increasing to 3 feet below and penetrating 3 feet into the impact berms. Screening of the soil by X-Ray Fluorescence (XRF) will be conducted during the excavation to direct additional soil removal as necessary. It is estimated that 490 cubic yards (780 tons) of excavated soil will be classified as California hazardous waste and 660 cubic yards (1,050 tons) will be classified as RCRA hazardous waste and will be handled as such and disposed of at Clean Harbors in Buttonwillow, California, a disposal facility for both RCRA and California hazardous wastes. To meet the soil profiling requirements of the receiving facility for the excavated soil, prior to excavation of impacted soil, approximately 7 to 8 additional soil samples (one per 250 tons)will be collected and analyzed for total lead by EPA Method 60106, WET soluble lead by EPA Method 7420 and TCLP soluble lead by EPA Method 1311 to use with existing data to profile the soil in accordance with the disposal facility requirements. Following excavation, confirmation soil samples will be collected to demonstrate successful removal of soil impacted by COPCs at concentrations exceeding their respective RSLs. First the excavation floors and sidewalls will be screened utilizing XRF to detect lead exceeding the RSL. Discreet soil samples will then be collected at 25-foot intervals from the top of the excavation sidewall and from 25-foot by 25-foot square grids on the excavation floor. Soil sampling will be deterministic, addressing soil with maximum XRF readings or other indication of potential impact. It is anticipated that approximately 52 confirmation soil samples will be collected, 27 from the excavation floor. All samples will be analyzed for total lead by EPA Method 6010B, and 25% of the samples will also be analyzed for the CAM 17 metals by EPA Methods 6010B and 7471A, and polynuclear aromatic hydrocarbons (PAHs) by EPA Method 8270C/SIM. All method detection limits (MDLs) are sufficiently low to ensure RSLs are not exceeded, as are all practical quantification limits (PQLs) except for thallium with a PQL above its RSL; detections of thallium less than its PQL will be J-flagged. Soil sampling locations will be marked with a flag and the locations of any samples that exceed the RSL for any COPC will undergo additional excavation to remove such impacted soil and the excavation sidewall or floor will be resampled and analyzed. The EHD has been informed (R. Day email 29 December 2016) that soil not identified as exceeding the cleanup goals of any COPC, including portions of the berms, will be utilized for fill in the excavation and that 8 to 10 soil samples would be collected outside the excavation to confirm the excavation limits. The EHD further notes that the SREW indicates that the excavated area will cover approximately 16,604 square feet of the anticipated former firing range site legal description of an estimated 200 feet by 300 feet (60,000 square feet), leaving approximately 43,396 square feet of the former firing range unexcavated and mostly unsampled.