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STATE OF CALIFORNIA PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD-- <br /> CENTRAL VALLEY REGION <br /> 3443 ROUTIER ROAD, SUITE A <br /> SACRAMENTO, CA 95827-3498 E <br /> PHONE: (91 361-56006 E E i <br /> FAX: (91361-5686 <br /> 6) 5686 <br /> AUG t 9 199119 August 1991 ENVIRONMENTAL HEALTH <br /> Ms. Laurie Cotul 1 a PERMIT/SERVICES <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton, CA 95201 <br /> ORCHARD SUPPLY HARDWARE, 8715 WEST GRANT LINE ROAD, TRACY, SAN JOAQUIN COUNTY <br /> We received your letter, dated 16 July 1991, requesting closure certification <br /> for Orchard Supply Hardware in Tracy. Our review of the file shows that: <br /> 1. A gasoline underground storage tank was removed in 1986. During an <br /> environmental site assessment three monitoring wells were installed at <br /> the site in March 1990. Depth to water in MW-1 and MW--2 was reported at <br /> about 8.5 feet and at about 11 feet in MW-3. Well MW-3, nearest the <br /> former tank location was the only well that contained ground water <br /> contamination at 130 ppb TPHg. Re-excavation of the former tank site <br /> and MW-3, which was within the excavation, was completed in August 1990. <br /> The remainder of MW-3 was properly abandoned in January 1991. Well MW- <br /> 313 was installed near the northern edge of the excavation at the same <br /> time. Depth to water in MW-3B was reported at about 12 feet. <br /> 2. The "Soil Excavation and Aeration" report, dated 19 October 1990, with <br /> an addendum, dated 29 October 1990, stated that approximately 1650 cubic <br /> yards of soil were excavated and aerated. After the first stage of <br /> excavation, soil samples were collected from the sidewalls near the base <br /> of the excavation at about 10.5 feet. Contaminants in five soil samples <br /> ranged from 60 ppm to 1100 ppm Oil and Grease hydrocarbons. Apparently <br /> additional lateral excavation (over--excavation) occurred towards the <br /> northeast. However,it is unclear from either the report or the addendum <br /> whether the excavation was extended vertically below 10.5 feet. <br /> 3. The three existing wells, MW-1, MW-2, and MW-313, have had non-detectable <br /> levels of contamination since they were installed. However, the boring <br /> log for Well MW-3B indicated soil contamination of 770 ppb Total <br /> Recoverable Hydrocarbons at 4 feet and 20 ppb at 9 feet. The fractions <br /> of hydrocarbons were not identified. Five borings were then drilled <br /> around MW-3B in an effort to determine the extent of remaining soil <br /> contamination. The analyses of the soil samples revealed non-detectable <br /> levels of contamination in all five borings. <br /> Therefore, at this time we cannot concur with site closure because of soil <br /> contamination in MW-3B and lack of information about possible contamination <br /> remaining in the soil after excavation. Orchard Supply Hardware must present <br /> a precise description of the over-excavation activities before closure may be <br /> considered, including the following information: <br />