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' 2.0 CLEANUP GOALS ' Potential contaminants onsite are associated with use of the Site as a firing range. The following Chemicals of Potential Concern (COPCs)and proposed cleanup goals(cleanup goals based on ' USEPA 2016 Regional Screening Levels, Residential Exposure Scenario, modified for lead by DTSC Human Health Risk Assessment Note #3 (DTSC 2014)) were identified in the SREW: ' ➢ Antimony 31 mg/kg ➢ Copper 3,100 mg/kg ' ➢ Lead 80 mg/kg ➢ Tin 47,000 mg/kg ➢ Zinc 23,000 mg/kg ' Lead concentrations in the Site assessment samples exceeded the proposed residential cleanup goal in the upper foot of the firing range floor and up to three feet in the impact berm(XRF readings and metal detection findings indicate that bullets penetrated the berm to a depth of 2.5 ' to 3 feet). ' Arsenic was identified in the SREW as a potential COPC at the Site. The SREW stated that if the proposed arsenic confirmation data was equal to or less than 12 mg/kg,then arsenic would ' not be considered a COPC. SJCEHD's conditional approval letter also required comparison of arsenic confirmation data to site background data. Geocon collected perimeter samples2 March 16, 2017 outside the excavation area after the initial excavation activities were completed. Arsenic concentrations in Pacific Edge's March 16,2017 excavation confirmation samples ranged from 0.27J mg/kg to 1.6 mg/kg. Arsenic concentrations in Geocon's March 16, 2017 perimeter data ranged from 1.6 mg/kg to 2.5 mg/kg. Arsenic is not considered a COPC as the ' confirmation samples were below the SREW proposed 12 mg/kg and equal or below Geocon's perimeter data. 1 1 1 2 Arsenic"background"data summarized on Geocon's Table 3 - Summary of CAM-17 Metals and Tin Results included in their August 25,2017 Former Police Firing Range,Documentation of Observations and Confirmation ' Sampling. PACIFIC EDGE ENGINEERING 1 Closure Report_final.doc (949)470-1937;(949)470-0943(FAX)