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Delta <br /> //nEnvironmental <br /> on uta ts,Inc. <br /> 3300 Data Drive, Suite 100 <br /> Rancho Cordova,CA 95670 <br /> 916/638-2085 <br /> FAX 916/638-8385 <br /> ' k A 9 Rye 1 <br /> January 15, 1991 J A N 9 8 i X91 <br /> ENV[i]k, —Til <br /> Ms Darlene Reuss <br /> Environmental Health Division <br /> San Joaquin Local Health District <br /> 1601 East Hazelton Avenue <br /> Post Office Box 2009 <br /> Stockton, California 95201 <br /> Subject Problem Assessment Report <br /> Shell Service Station <br /> 7700 Moreland Court, Stockton, California <br /> 'lop Shell WIC No 204-7524-4107 <br /> Delta Project No 40-88-146 <br /> Dear Ms Reuss <br /> Enclosed is a copy of a Problem Assessment Report (PAR), prepared by Delta Environmental <br /> Consultants, Inc (Delta), for the subject site Chemical analyses of a soil sample collected from the <br /> former storage tank location, and a soil sample collected from a former product line trench detected <br /> concentrations of total petroleum hydrocarbons (TPH) greater than 1,000 parts per million Based on <br /> these analyses and the fact that depth to ground water was unknown, the San Joaquin County <br /> Environmental Health Division had requested that a hydrogeologic investigation be conducted at the <br /> site The PAR presents the results of site investigations conducted at the site The results indicate that <br /> the ground water table is greater than 70 feet below site grade, the site is underlain by clay soils, and <br /> concentrations of TPH to soil appear to be restricted to depths less than 15 to 20 feet beneath two small <br /> areas at the site Also, chemical analysis of a ground water sample collected from the on-site water <br /> supply well did not detect petroleum hydrocarbons <br /> It is Delta's opinion, based on data collected from the site, that the concentrations of TPH detected in <br /> soil samples near the former product line and storage tank locations are confined to a small volume of <br /> soil and that the geology of the site (clayey soils) inhibits the vertical migration of petroleum <br /> constituents It is our opinion that the small quantity of soils containing petroleum hydrocarbons does <br /> not present a threat to ground water which is greater than 70 feet below the surface Dispersion, of the <br /> petroleum constituents will occur as they migrate through the soils toward the ground water Also,the <br /> clay soils beneath the site will likely attenuate petroleum hydrocarbons Furthermore, natural <br /> biodegradation through time will decrease the existing petroleum concentrations Consequently,Delta <br /> is recommending that no further action be taken at the site <br />