ARCHIVED REPORTS - GROUNDWATER MONITORING WELL INSTALLATION AND LIMITED SOIL SAMPLING

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in KLEINFELDER The WQGs are based on the "California Environmental Protection Agency Regional Water Quality Control Board, Central Valley Region, A Compilation of Water Quality Goals", dated August 2003. Maximum contaminant levels (MCLS) are a part of the drinking water standards adopted by the California Department of Health Services (DHS). The United States Environmental Protection Agency (USEPA) also adopts MCLS under the Safe Drinking Water Act. DHS' drinking water standards must be at least as stringent as those adopted by the USEPA. Primary MCLS are derived from health .based criteria (i.e. cancer risk). Secondary MCLs are ' derived from human welfare considerations (i.e. taste, odor, laundry staining). The soil samples collected during the advancement of the soil borings for monitoring wells ' showed detectable concentrations of arsenic, barium, chromium, cobalt, copper, nickel, vanadium, and zinc. Each of the noted detected concentrations were below the Preliminary Remediation Goals (PRGs) and may be considered to be naturally occurring background ' concentrations. 7.2. RECOMMENDATIONS 1) Kleinfelder recommends the excavation of affected soils for disposal off-site to a depth of approximately 2-feet in the areas of near surface contamination as indicated on Plate 2. Kleinfelder recommends the excavation of affected soils to a depth of 4-1/2-feet in the area of ' the concrete pad (B-1, B-2, B-3) and the depth of approximately 6-feet near B-6 also indicated on Plate 3. The excavated soils should be disposed of at an approved waste facility designated to handle such waste. Kleinfelder can aid the client with this task for an additional fee. ' 2) Confirmation soil samples should be collected and analyzed for TTLC and STLC concentrations from the bottoms of the excavated areas of the site to determine if the vertical extent of lead contamination reaches greater depths. 3) Kleinfelder recommends that the soil cuttings generated from the installation of the ' monitoring wells and previously contained in 55-gallon drums and stored on site be emptied to the ground surface and spread on site as the soil sample analyses did not show levels of the detected concentrations at or above the applicable PRGs. Regulatory agency consent with this recommendation should be sought prior to dispersal of the drummed contents. Kleinfelder can aid the client with dispersal of the drummed soils for additional fees. 4) A copy of this report should be forwarded to the San Joaquin County Environmental Health Department (EHD) for their review and comment. ' This report is subject to the "Limitations" presented in Chapter 7 of this report. Any other party (other than First Service Properties or regulatory agencies having enforcement jurisdiction for this ' site) who would like to use this report shall notify Kleinfelder, Inc. of such intended use by requesting permission from Kleinfelder in writing. 42I62.E01 /ST04R854 Page 21 of 22 ' Copyright 2004,Kleinfelder,Inc. July 1,2004