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California gional Water Quality Cc ',rol Board d <br /> QL_�N Central Valley Region <br /> W; Katherine Hart, Chair 2"�°��:=�' <br /> Linda S.Adams 11020 Sun Center Drive#200, Rancho Cordova, California 95670-6114 Arnold <br /> Secretary for Phone(916)464-3291 • FAX(916)464-4645 Schwarzenegger <br /> Environmental http://www.waterboards.ca.gov/centraIvaIley Governor <br /> Protection <br /> 6 July 2010 <br /> Mr. Robert Gray <br /> JUL Q 7 1010 <br /> Pacific Gas and Electric Company ENVIRONMENT HEALTH <br /> Environmental Remediation PERMIT/SERVICES <br /> 3401 Crow Canyon Road Room 176G <br /> San Ramon, CA 94583 <br /> EXCAVATION AND SAMPLING WORK PLAN, C-51 TANK SITE, PACIFIC GAS AND <br /> ELECTRIC COMPANY MCDONALD ISLAND COMPRESSOR STATION, ZUCKERMAN <br /> ROAD, NEAR HOLT, SAN JOAQUIN COUNTY <br /> The California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff reviewed the 1 June 2010 Excavation and Sampling Work Plan for the <br /> C-51 Tank Site, at McDonald Island Compressor Station, near Holt, San Joaquin County <br /> (Site). The Work Plan was prepared on your behalf by ARCADIS. <br /> The purpose of the Work Plan is to document the results of soil sampling conducted in April <br /> 2010 following the excavation and removal of petroleum-impacted soils at the Site, which was <br /> was intended to delineate the horizontal and vertical extent of impacts in soil. The post- <br /> excavation soil sampling results included occurrences of Total Petroleum Hydrocarbons (TPH) <br /> as gasoline, diesel, and motor oil above Regional Water Quality Control Board, San Francisco <br /> Bay Region Environmental Screening Levels (ESLs), at four locations, at depths to 8 feet <br /> below ground surface. Based on these data, the Work Plan proposes additional soil removal, <br /> confirmation soil samples, and groundwater sampling. <br /> In the Work Plan, ARCADIS proposes two excavations around the three borings where soil <br /> TPH concentrations exceeded ESLs. Confirmation soil samples will be collected from side <br /> walls and bottoms of each of the two planned excavations. <br /> I have reviewed the Work Plan and have the following specific comments. <br /> 1. The Work Plan specifies excavation of soils around borings C51-SB02 and C51-SB13 to <br /> one foot below impacted soil, and excavation around C51-SB04 to two feet below <br /> impacted soil. Please provide the rationale for the difference in excavation depths at <br /> these two locations. <br /> 2. A temporary well point (651-TW-01) is proposed for the collection of a single <br /> groundwater sample. The proposed location of this well point is approximately 12 feet <br /> from the edge of the excavation around C51-SB02, and 22 feet from the edge of the <br /> excavation around soil boring C51-SB04. Please explain why this location was chosen, <br /> including whether it is likely to intercept potential impacts to groundwater from the original <br /> release of petroleum products. <br /> California Environmental Protection Agency <br /> pZaRecycled Paper <br />