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it � � JJ CALIFORNIA GEOPHYSICAL GROUP , INC . P . O . Box 578341 , Modesto , CA 95357 Tel : (209) 527- 1247 April 12 , 2000 Fax : (209) 527-4810 Public Health Services San Joaquin County a 304 East Weber Ave. 3`d Floor APSnfll Stockton , CA 95202 ENVIRGfvfVj fu ! r.JEALTF{ R__Rfvli 1"/SC 1 iCc RE : Work Plan Darpetro, Inc. USA Service Station 749 E . Charter Way Stockton , CA Site No. 1060 On January 10, 2000 , the EHD sent a letter requesting further work at this site. We submitted a work plan on February 29, 2000, which was rejected . This work plan will define the work. On August 5, 1999, we reported the drilling of two wells. One of the wells VW-7 was drilled to a depth of 80 feet in order to define the depth of contamination . Unfortunately, the contamination at 80 feet was 24 ug/Kg of Benzene , 43 ug/Kg of Ethyl-benzene, 94 ug/Kg of xylene and 5.9 mg/Kg of TPH . San Joaquin County requires that two samples taken 5 feet apart have non-detectable readings in order to define the depth of contamination. The San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has requested another boring drilled near well VW-7 to define the contamination below 80 feet. We are planning to drill a boring near vapor well VW-7 to a depth where two consecutive soil samples are free of contamination. The boring will be performed by Precision Sampling , their drilling License Number is C-57-636387 . The boring will be performed with a CPT drilling rig and the boring will be about 11 /2 inch in diameter. This boring is within 10 feet of well VW-7 and we will obtain a CPT log to a depth of 100 feet. The CPT log will help us understand the lithology, especially below the water table. Samples of soil will be obtained, starting at 85 feet and tested every 5 feet until two succeeding samples are found free of contamination. This boring will be B- 2 , see Figure 1 . Another boring (13-3) will be drilled with a CPT rig to a depth of 100 feet. The log obtained will inform us of the lateral extent of lithologic units under this site. This rig will obtain a sample of the soil gas at 20 feet below the surface (bgs) . This sample may help us understand if the tanks near this boring are leaking . Sampling in wells MW-3 and MW-2 in October 1999 and February 2000 indicate that the MtBE is increasing in these wells. This may be coming from a tank leak or it may be contaminated water migrating from off site. The soil gas sample will be placed in a tedlar bag and delivered to the laboratory. A soil sample will betaken at the water table and at 60 feet bgs . Water samples will be taken at the water table and every 10 feet until we reach 60 feet bgs. Both CPT borings will be abandoned by backfilling with hydrated cement. The laboratory testing will be performed by Excelchem Environmental Labs of Roseville, CA with a mobile laboratory. The soil and water will be tested as follows: Tests Chemicals Detection Limits