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,MEMORANDU,I' I Cal/EPA
<br /> CALIFORNIA REGIONAL WATER QUALITY;aCONTROL BOARD
<br /> { CENTRAL VALLEY REGION r a
<br /> (916)255-3000 + CALNET 5-494-3000 e,FAX(916)255-3015 . Pete Wilson CO1e1 Or
<br /> 13 y
<br /> lr TO: Gordon L. Boggs FROM:, Patricia A. Anderson
<br /> DATE: 23 January 1998 SIGNATURE:
<br /> SUBJECT: REVIEW FOR NO FURTHER ACTION, FORMER TOWN& COUNTRY CHEVRON,
<br /> 13336 EAST HWY 88,L0CSEFORD, SAN JOAQUIN COUNTY
<br /> Based on my review of the case file, concerning the above site, I have noted the following: ,..
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<br /> Background: In July 1991, a 10,000-gallon regular gasolin tank,-a'550-gallon waste oil tank, and two
<br /> (a 5,000-gallon and a 7,000-gallon) unleaded gasoline tanks, and 400 ft of associated product pipelines
<br /> were removed from the above site. Discolored soil and petroleum`odors were noted in the pit beneath
<br /> the gasoline tanks and waste oil tank pit. No odor or discoloration;was noted beneath the product
<br /> pipelines. Soil samples, collected beneath the pipelines,were noridetect for petroleum contaminants;
<br /> however, samples, collected from the pits had significant petroleum contamination.
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<br /> Contaminated soil was excavated from the areas of the former gasoline and waste oil tanks. In August
<br /> 1991, soil samples were collected from the bottom of the waste oil tank excavation at 7.5 feet below
<br /> ground surface (ft bgs), and from the bottom of the gasoline lank`excavation at 13 - 14 ft bgs. The pits
<br /> were backfilled with pea gravel and the stockpiled contaminated soil was sampled and disposed off-site.
<br /> The gasoline tank pit was not covered with asphalt, so rain water€entered the pit, recharging the aquifer,
<br /> and leaching contaminants from the soil. Is
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<br /> In August 1997, a soil boring was advanced near the waste oil tank excavation to 17 ft bgs, and five soil
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<br /> borings were advanced to between 20 and 30 ft bgs in the gasoline;tank excavation area. These soil
<br /> borings along with geologic logs from nearby wells shows that sandy clay and clayey sand deposits
<br />` extend from the surface to 23 ft bgs. These clay and sand betas overly clayey sand and sandy silt
<br /> -- _ deposits that extend-to 30,_ft bgs'.where `saprolitic';.deposits are.encountered. This "saprolitic'wdeposit
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<br /> correspond to brittle/sandy clay beds in the regional wells that extend to the depth of the regional water
<br /> table. Based on the relationship of the depth of the first encountered ground water with the final water
<br /> level, some of the regional wells installed into the aquifer beneath the clay bed appear confined while
<br /> others appear unconfined. This indicates the brittle/sandy clay bed is an aquitard and can not prevent.
<br /> contamination of the water table, which occurs'at 70 - 100 ft bgs kI
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<br /> Soil samples were collected from the bottom of the waste oil pit,�at 7.5 ft bgs, and at 5 ft intervals while
<br /> advancing the boring. The analytical results of these samples shows that contaminated soil remains from
<br /> 7.5 to 9 ft bgs with 530 mg/kg TPH-oil to 91 mg/kg TPH-g,"and F0,149 mg/kg EX and 1.08 mg/kg TEX,
<br /> respectively. No PCBs or chlorinated solvents were detected. All:of the detected metals were below the
<br /> Total Threshold Lieut Concentration Values (TTLC). The samples at 13 ft bgs were nondetect for
<br /> petroleum contaminants. However,the samples at 16 ft bgs had 0:009 mg/kg toluene and 0.017 mg/kg
<br /> Our mission is to preserve and enhance the quality of California's water resources,and
<br /> ensure their proper allocation and efficient use for the benefit of present and future generations.
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