SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

"0 � ` I�EMORANDUilM Cal/EPA • — a p ' = � CALIFORNIA REGIONAL WATER QUALITYE CONTROL BOARD ` f4a�'q pYUJTY CENTRAL VALLEY REGION (916)255-3000 • CALNET 8-494-3000 •'�FAX`(916}255-3015 Pete Wilson,Governor E xt TO: Gordon L. Boggs - E FROM Patzacia A. Anderson DATE: 23 January 1998 SIGNATURE:! L� €f SUBJECT: REVIEW FOR NO FURTHER ACTION, FORMERi TOWN& COUNTRY CHEVRON, 13336 EAST HWY 88,LOCKEFORD, SAN JOAQUIN COUNTY : j Based an my review of the case file, concerning the above site, I have noted the following: Background: In July 1991, a 10,000-gallon regular.gasoline tank!ra 550-gallon waste oil tank, and two (a 5,000-gallon and a 7,000-gallon) unleaded gasoline tanks, and 400 ft of associated product pipelines were removed from the above site. Discolored soil and petroleum'oclors were noted in the pit beneath . the gasoline tanks and waste oil tank pit. No odor or discoloration was noted beneath the product pipelines. Soil samples, collected beneath the pipelines, were�nondetect for petroleum contaminants; however, samples, collected from the pits had significant petroleum contamination. Contaminated soil was excavated from the areas of the formergaso.1ine and waste oil tanks. In August 1991, soil samples were collected from the bottom of the waste oil�l 'tank excavation at 7.5 feet below ground surface (ft bgs), and.from the bottom of the gasoline tank excavation at 13 - 14 ft bgs. The pits were backfilled with pea gravel and the stockpiled contaminated soil;was sampled and disposed off-site. The gasoline tank pit was not covered with asphalt, so rain water entered the pit, recharging the aquifer, r and.leaching contaminants from the soil. ,. : T ;I %J!1 l ',:, s 'I In August 1997, a soil boring was advanced near the waste oil tank excavation to 17 ft bgs, and five soil borings were advanced to between 20 and 30 ft bgs in the gasoline tank excavation area. These soil borings along with geologic logs from nearby wells shows that;sandy clay and clayey sand deposits extend from the surface to 23.ft bgs. These clay and sand beds overly clayey.sand and sandy silt ' �.—deposits that extend to.30 ft bgs,,where}`saprol tic',.:deposits-areaencountered: This.�`saproIitic'_' deposit: �-- may correspond to clay beds in the regional wells, and is not a'saprolite that grades immediately into bedrock. At greater depths, geologic logs from regional wells show brittle/sandy clay with occasional clay, and rock deposits, or gravel and sand deposits with occasional!sandy or silty clay deposits to the depth of the regional water table. Based on the relationship of the depth of the first encountered ground water with the final water level, some of the regional wells installed into the aquifer beneath the clay bed appear confined while others appear unconfined. This indicates theE:clay bed is an aquiclude and can not ; prevent contamination of the water table, which occurs at 70 - 100 ft,;bgs. - Soil samples were collected from the bottom of the waste oil pit, at#7i 5 ft bgs,and at 5.ft intervals while advancing the boring. The analytical results of these samples showsthatcontaminated soil remains from 7.5 to 9 ft bgs with 530 mg/kg TPH-oil to 91 mg/kg TPH-g, and 0.1.49 mg/kg EX and 1.08 mg/kg TEX, respectively. No PCBs or chlorinated solvents were detected. All of the detected metals were below the Total Threshold Limit Concentration Values (TTLC). The sarniples,'at 13 ft figs were nondetect for petroleum contaminants. However, the samples at 16 ft bgs had 0.009 mg/kg toluene and 0.017 mg/kg ° Our mission is to preserve and enhance the quality of Cal fornia's water resources,and ensure their proper allocation and efficient use for the benefit of present and future generations. r Recycled Paper