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STATE OF CALIFORNIA _ PETEWILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL <br /> OARD CENTRAL VALLEY REGION Z.- <br /> 3443 ROUTIER ROAD, SUITE A s <br /> SACRAMENTO, CA 95827-3098 <br /> PHONE: (918) 361 .7 <br /> FAX: (916) 361-568686 RCt # MU <br /> AUG 1 . 9 1991 <br /> 19 August 1991 ENVIRONMENTAL HEALTH <br /> Ms: Laurie Cotulla PER MIT/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 /> 3B 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 AW-3B, 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 170 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-36 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. I <br /> { <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 />