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(y: <br /> s . <br /> id <br /> CALIFORNIA GEOPHYSICAL GROUP, INC. <br /> 12973 Cree Court,Poway CA 92064 <br /> Tel:486-1323 • 679-11 14 <br /> s <br /> K� 1 of 6 Pages <br /> I <br /> �a SITE ASSESSMENT <br /> Gasco Service Station <br /> 749 E. Charter Way <br /> -� Stockton, CA <br /> I , <br /> February 9, 1990 <br /> SITE HISTORY <br /> On November 14, 1989 the following tanks were removed from the <br /> site in accordance with the Tri-Regional Recommendations: <br /> 1 8,000 Gal. Unleaded Gasoline <br /> 1 5, 000 Gal. Super Unleaded Gasoline <br /> r,. <br /> 2 5,000 Gal. Unleaded Gasoline <br /> A total of 8 soil samples were taken two under each tank and <br /> analyzed for THP, and BTX&E. The lab results previously <br /> reported varied from 1. 9 to 3600 PPM for `fPH. Therefore, it was <br /> resolved that the site is a Case # site and in a Categcry #1 <br /> area with the water table located at about 39 feet below the <br /> surface. <br /> I <br /> The excavation site was backfilled with the original soil plus <br /> soil from a new excavation. The site was then remodeled and <br /> Placed back in service. <br /> On Dec. 19, <br /> 1989 an Electromagnetic Induction survey was <br /> conducted on the site to aid the investigation of the areal <br /> extent of the plume and assist in locating the ground water <br /> �•� monitoring wells. <br /> A work plan for assessing the contamination of the site was sent <br /> t� <br /> the the San Joaquin Local Health Department of Dec. 29, 1989 <br /> along with a well drilling permit. The plan was accepted and a <br /> special well permit was issued on Jan. 19, <br /> k" Drilling and sampling according to the work plan began on <br /> 22, and finished on Jan 26, 1990. This report addressesthen. <br /> data acquired and analyzed according to the work plan. <br /> GEOLOGY <br /> The site and all nearby terrain are underlain by non-marine, <br /> fine-grained sediments which are tentatively Fissigned to thr, <br /> Modesto Formation of Pleistocene age. (USGS Bulletin 1470 <br /> Marchand and Alwordt, 1881) . <br /> Although the Modesto is typically <br /> composed of coarser--grained material such as sands and gravels <br /> it is reasonable, on the basis of stratigraphic position, to <br /> consider these finer-grained sediments to be the distal <br /> of the large alluvial fans which make up the Modesto.of <br /> 4 <br />