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HORIZON ENVIRONMENTAL INC. Specialists in Site Assessment Remedial Testing Design and Operation August 13, 1997 Mr Kenneth Earnest g;gXJYTJ Ultramar Inc 525 West Third Street AUG 2 0 1997 Hanford, California 93230 ENVIRONMENTAL HEALTH Subject Results of Remedial Testing PERMIT/SERVICES Beacon Station No 419 2350 Waterloo Road, Stockton, California Mr Earnest At the request of Ultramar Inc (Ultramar), Honzon Environmental Inc (Horizon) has prepared this letter report which presents the results of remedial testing at the above- referenced site (Figure 1) The purpose of the aquifer pumping tests was to evaluate aquifer characteristics of the shallow water-beanng zone beneath the site, and to evaluate the potential of groundwater pumping as a remedial option for the recovery of petroleum hydrocarbon-impacted groundwater from beneath the site The work was performed as outlined in the January 23, 1995, Work Plan for Hydrogeologic Testing and Additional . Subsurface Assessment at Beacon Station No 419 prepared by Acton, Mickelson, van Dam, Inc (AMV) The site is an operating gasoline service station located on the southwestern corner of the intersection of Waterloo Road and Sierra Lane in Stockton, California Site facilities include a station building, two gasoline product dispenser islands located east of the station building, and three underground gasoline storage tanks (USTs) located toward the eastern property boundary There are currently five groundwater monitoring wells, MW-1 through MW-5, at the site Locations of these and other pertinent site features are shown on the Site Plan (Figure 2) Previous environmental work at the site was performed by Horizon and others This previous work included drilling three onsite soil bonngs (SB-1 through SB-3) in March 1991, the removal and replacement of the UST's in October 1993, drilling three soil bonngs and the installation of three onsite 4-inch inside diameter (ID) groundwater monitoring wells (MW-1 through MW-3) in July 1994, and drilling three soil bonngs and the installation of two onsite 4-inch ID groundwater monitoring wells (MW-4 and MW-5) and one offsite 2- inch ID groundwater monitoring well (MW-6) in May 1996 Gasoline hydrocarbons were found to be present in soil and groundwater during these previous investigations Groundwater was found to be present at a depth of approximately 70 feet below ground . surface (bgs) in July 1994 and between 53 to 57 feet bgs in May 1996 The subsurface water-bearing zone previously encountered beneath the site consisted predominantly of silty sand (SM) with interbeds of sandy to clayey silt (ML) and sandy to silty clay (CL) 5011 Golden Foothill Parkway Suite 7 • EI Dorado Hills CA 95762 • (916)939-2170 • FAX(916)939-2172 PO Box 5283 9 Bakersfield CA 93388 • (805) 589-8389 • FAX(805)589-1456