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December 28, 2016 City of Manteca Attn: Elena Reyes, City Manager 1001 W. Center Street Manteca, CA 95337 Subject: Soil Remedial Excavation Work Plan (SREW) Approval Letter Former City of Manteca Police Firing Range 2516 W. Yosemite Avenue Manteca, CA 95336 The San Joaquin County Environmental Health Department (EHD) has received and reviewed Soil Remedial Excavation Work Plan, Former Police Firing Range, Manteca, California (SREW), dated December 2016, prepared by Pacific Edge Engineering, Inc. (Pacific Edge) for Innovative Construction Solutions (ICS) on your behalf. In addition, the EHD met with a representative of Geocom Consultants, Mr. Richard Day, to discuss modifications to the previous work plan, Remedial Action Plan, Former Police Firing Range, Manteca, California (RAP), dated August 2016, also prepared by Pacific Edge, to limit its scope to those actions specified in California Health and Safety Code Section 101480 under which the EHD can provide regulatory oversight. In the SREW, Pacific Edge stated the goal of the proposed removal action is to place the Site in a condition that allows it to be permanently used for its planned use without any significant risk to human health or any significant potential for future environmental damage. The removal action proposed for the site includes excavation and offsite disposal of soil with chemicals of potential concern (COPCs) concentrations that exceed proposed cleanup goals. The cleanup goals proposed are the United States Environmental Protection Agency (EPA) Regional Screening Levels (RSLs), which are risk-based screening levels protective of human health, but that for lead is the California Human Health Screening Level (CHHSL). Based on the Geocon report Site Investigation Report, Former Police Firing Ra ge, Manteca ( California, (SIR) dated October 2015, Pacific Edge identified the following COPCs nd proposed cleanup goals, in milligrams per kilogram (mg/kg) for each: antimony — 31 mg/kg; copper - 3,100 mg/kg; lead — 80 mg/kg; tin — 47,000 mg/kg; and zinc — 23,000 mg/kg. With the exception of lead and possibly arsenic, none of the other metals are thought to be present at concentrations that exceed their respective RSL. As the previous agricultural land use and natural background arsenic concentrations may cause arsenic concentrations to exceed its RSL of 0.67 mg/kg, Pacific Edge proposes to utilize the screening concentration of 12 milligrams per kilogram (mg/kg) used in the Schools Program by the California Department of Toxic Substances Control (DTSC) to evaluate arsenic as a COPC; arsenic concentrations exceeding 12 mg/kg will trigger establishment of a site- specific background concentration. r{'J 3r« prry I