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v INTRODUCTION GHH Engineering, Inc. (GHH) is currently providing West Lane Fuel (West Lane)professional engineering services to assist them with environmental issues pertaining to their site located at 3300 N. West Lane, Stockton, California, as shown on Figur.fMror hJay s site. This orkplan has authorized GHH to prepare thus Additional Assessment Workplan (AA ) been prepared for submittal to the San Joaquin County Environmental Health Department (County), the lead regulatory agency overseeing environmental issues at the site. BACKGROUND AND SITE HISTORY Site Description The site is currently a retail convenience store located on the northwest corner of West Lane and Alpine Avenue, 3302 West Lane, Stockton, CA. The property is asphalt paved and houses one rectangular-shaped office/store building and two former dispenser island locations as shown an Figure 2. The site formerly contained three underground storage tanks (UST). Location maps for the UST's were unavailable. According to the USGS Stockton West Quadrangle map, the site is approximately 19-feet above Mean Sea Level (MSL). The closest surface water body is the Calaveras River, located approximately 3,500-feet north of the subject site. Geology and Hydrogeology Geologically, the property is underlain by the Quaternary Modesto Formation and the deeper Quaternary Riverbank formation, both of which consist mainly of arkosic alluvium derived mainly from erosion of the Sierra Nevada Mountains to the east. Both the Modesto and Riverbank formations are part of the Great Valley sedimentary sequence of rocks which fill the large Great Valley sedimentary basin which was originally derived as a forearc basin between the Sierran are to the east and the subduction zone to the west. Stockton is located within the San Joaquin Valley which consists of the southern two thirds of the Great Valley province. The northwesterly flowing San Joaquin River and its tributaries are the main drainage feature of the San Joaquin Valley. Groundwater is present at the site at approximately 50 feet below ground surface(bgs). During the drilling of three borings(SB-2 through SB-4), the dominant material encountered included silt, silty sand, and fine-grained sand. Groundwater was encountered at approximately 54-feet bgs in each of the three borings. Although no site specific gradient information has been gathered at the site, groundwater flow direction is most likely to the west, towards the confluence of the Calaveras and San Joaquin Rivers or to the southeast towards a California Service Well (477)located less than 1000-feet southeast of the site.