SITE INFORMATION AND CORRESPONDENCE

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California Ronal Water Quality Qntrol Board Central Valley Region Peter M.Rooney Sacramento Main Office Ed J.Schnabel 3ecretaryfor Internet Address: httpi//www.swrcb,mgov/-rwgcb5ftme.htrnl 0Chair Environmenial 3443 Routier Road,Suite A,Sacramento.California 95827-3003 Protection h Phone(915)255-3000•FAX(915)255-3015 TO: Gordon L. Boggs FROM: Mark R. List UST Program Manager Engineering Geologist DATE: 28 December 1998 SIGNATURE: 1 SUBJECT:. FILE REVIEW FOR CLOSURE CONCURRENCE, MARKET STREET -PARKING STRUCTURE,b4 SOUTH SUTTER STREET, STOCKTON, SAN JOAQUIN COUNTY At the request of the San Joaquin County Environmental Health Division (SJCEHD), a file review was completed to determine if Regional Board staff agree with the SJCEHD determination of no further action required at this site. This information was obtained during my review of the Regional Board casefile for the Market Street Parking Structure site. Background: One 1,200-gallon underground storage tank(UST, Tank#4)was discovered in February 1989, during excavation activities associated with new construction at the site. One soil sample collected at approximately 8.5 feet below ground surface, at the east end of the UST revealed 110 mg/Kg total petroleum hydrocarbons as diesel, however,BTEX were not detected above laboratory reporting limits. San Joaquin County Environmental Health Division requested overexcavation and confirmation sampling be completed at the Tank#4 location. Three other USTs and an oil/water separator were removed from the site during 1988, and the County did not require further investigation at these locations. OnA 0 March 1989,-the Tank#4 area was overexcavated to approximately 14 feet bgs. A lens of gray soil with a"sewage-type odor" was encountered betweenx l 1 and 13 feet below grade:"This unidentified' material was also noted in the excavation's north sidewall. Confirmation soil samples.were collected from the floor of the excavation at 14 feet bgs, and from the north sidewall at 13.5 feet bgs. The analytical laboratory reported that all TPH and BTEX constituents were below detection'limits, however, the lab indicated a.late eluding C15-C28 hydrocarbon in the sidewall sample. The late eluding hydrocarbon could not be quantified and may be associated with the gray stained soil. Following the overexcavation activities, the Market Street Parking Structure was completed. On'28 February 1994, the County placed the site in the Local Oversight Program and requested:site characterization. Between 1994 and 1998, several meetings were held to discuss proposed site activities, funding, and access constraints. Sampling of the nearby groundwater monitoring well, associated with the 145 South Sutter Street site, was non-detect for petroleum constituents. This well is located approximately 50 feet,from the former Tank#4 location. ,Groundwater is encountered at 30 feet bgs or deeper at the site. California Environmental Protection Agency Qd Recycled Paper