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PUBhIC HEALTH SERVICES oPa� N <br /> SAN JOAQUIN COUNTY N: <br /> JOGI KHANNA M.D.,M.P.H. A <br /> Health Officer <br /> (`q�iPOR a�S <br /> P.O. Box 2009 (1601 East Hazelton Avenue) Stockton,California 95201 <br /> (209) 468-3400 <br /> April 18, 1990 <br /> Bill Keller <br /> Genstar Western Stone Products <br /> P.O. Box 3171 <br /> Modesto, CA 95353 <br /> RE: Genstar West. Stone Prod. In Reply Refer to Site Code: 1393 <br /> 8181 W. lith <br /> Tracy, CA 95376 <br /> We have reviewed the January 24, 1990 Problem Assessment Report <br /> of Soil and Groundwater Contamination prepared by Waterwork for <br /> the above referenced site. Three monitoring wells were installed <br /> and sampled during the reporting period. Laboratory results <br /> reported 0. 88 and 0. 32 parts per billion toluene in MW #1 and MW <br /> #2 , respectively. The monitoring data indicates the groundwater <br /> gradient is "generally northwest at approximately 0. 003 ft/ft. " <br /> MW #1 is located upgradient from the originally documented <br /> contamination source and MW #2 is over seventy (70) feet <br /> northeast of the former tank location. <br /> Based on the above information, the proposal to conduct only <br /> quarterly monitoring is unacceptable. Field observations and <br /> tank pull analytical lab results show high levels of hydrocarbon <br /> contamination (110, 000ppb TPHD) in the area of the former 1000 <br /> gallon diesel tank. Additional sampling of the existing <br /> monitoring wells should be done to verify the analytical results <br /> and additional measuring of the groundwater should be done to <br /> verify the gradient direction. <br /> A monitoring well should be installed within 10 feet of the tank <br /> area in a downgradient location after the above sampling and <br /> measurements are completed. After this well is installed, a <br /> quarterly monitoring program should be implemented. <br /> Submit an addendum to your Problem Assessment Report with the <br /> above information by May 15, 1990. <br /> A Division of San Joaquin County Health Care Services <br />