SITE INFORMATION AND CORRESPONDENCE FILE 1

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5cNT BY:Xerox Telecopier 702' 4- 3-92 ; 3:53PM i ;# 2 a INVITATION FOR BIDS SI'Z'E CLEANUP FOR RUIZ GROCERY IN TRACY Consulting engineers, geologist, and other professional firms experienced in the field of underground storage tank corrective action work are being invited to submit bids to develop and im- plement a Corrective Action Plan (CAP) to clean up gasoline pol- luted soil and groundwater at- Ruiz Grocery, 4491 West Durham Ferry Road, ,Tracy CA. Bids shall include the consultants, pro- poBed CAP. All technical reports prepared during site investiga- tions will be made available upon request. A. Objective The objective of the work is to clean up the gasoline polluted soil and groundwater at Ruiz Grocery, 4491 West Durham Ferry Road, Tracy CA 95376, to the established cleanup levels as deter- mined by the leaching potential as defined State Leaking Under- ground Storage Tank (LUST) Manual for total petroleum hydrocar- bons (TFH) gasoline in soil and Non Detection (ND) for dissolved benzene in the groundwater ( 1 part per billion (ppb) is the Maxi- mum Contaminant Level (MCL) for dissolved benzene in groundwa- ter) . B. Background Ruiz Grocery, owned and operated by Wilibaldo and Stella Ruiz, is located on an approximately 650 ft. x 700 ft. parcel of land at the northeast corner of Aird Road and Durham Ferry Road 7 .5 miles southeast of Tracy, CA. The store is located in a converted gas station. Gasoline was retailed from one dispensing Island con- taining two 1, 000 gallon underground storage tanks containing leaded and unleaded gasoline. The entire site is covered with structures, concrete, or blacktop (See Attachment 1) . Three monitoring weals have been drilled on the property. Total petroleum hydrocarbons (TPH) as gasoline were detected in MW-1 and MW-2 at concentrations of 140 and 6400 ppb, respectively, in September 1991 . Concentrations of benzene were detected in MW-1 and MW-2 at 2 . 3 and 710 ppb, respectively. MW-2 had the highest concentration levels of 700 ppb, 130 ppb, and 1300 ppb of Toluene, Ethylbenzene, and Xylenes, respectively, while MW-3 concentration levels were btlow detection limits of the laborato- ry. The groundwater appeared to be approximately ten ( 10 ) feet below the ground surface with`a northeast gradient of approxi- mately 0 . 005 foot per foot. ` The San Joaquin County Public H }alth Services Environmental Health Division (PHS/EHD) is t / lead regulatory agency (LRA) , and will continue in the role roughout the cleanup unless the case is referred to the Region' Water Quality Control Board. Presently, Ms . Mary Mcays of, t LRA has approved Delta Environmental ' s recommendation to excavate soils to the depth of 11 feet and then aerate on site. However, the approval to aerate —1002753,XTC/==xH/w 75159-18437MM/04/03/92/3