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I Field Report f Monitoring Well Installation of MW-4 Grantline Plaza Tracy, California s On July 2, 1991, ROY F. WESTON INC. (WESTON) conducted furthF work on the site investigation at the Grantline Plaza site at 350 West Grantline Road in Tracy, California. ;I This investigation was performed to gain additional information on the potential presence of petroleum hydrocarbon compounds in groundwater and soils at the site. All work was completed as detailed in the WESTON Groundwater Investigation Work Plan dated June 25, 1991. A single boring was drilled at the site and a monitoring well was installed within the boring. This well was designated MW-4. 'Three shallow soil borings were also drilled at separate locations oh the same day with one soil sample collected from each boring. The locations of-the well:and soil borings were measured to the nearest foot with respect to permanent"onsite structures and are shown on Figure A-1. The boring,for MW-4 was drilled to a total depth of.20 feet below ground surface (BGS) using hollow stem auger techniques, This well was positioned in a location downgradient from the former UST and adjacent to the storm sewer line. This position was selected to assess the potential that petroleum compounds may have migrated along the storm drain line fill materials. Soil returned to the surface as cuttings was used to describe the types of sediments present. A lithologic log for the soil bo.ing is presented at the end of this report.:':The three shallow borings designated SB-1, SB-2, and SB-3 were located to assess the,fill materials 1:} at the northwest end of the former UST location and 2) along the underground 'lines running south to north along the alley west of the restaurant building. ` All devices used to drill the borings (including augers, bits, etc.) or to collect coil samr:,es (drive sampler) were decontaminated prior to and after use on each hole. Auge.- flights and bits were decontaminated by steam cleaning, whereas all smaller tools (i.e. hand augers) were washed in an alconoxlwaler mixture with stiff bristle brushes, rinsed in potable water and finally spray-rinsed with distilled water. All water that had been used for decontamination was containerized into labeled 55-gallon drums. All cuttings and soil brought tothe surface during the drilling was also placed into labeled 55-gallon steel drums. All drums were left onsite pending ana,ytical results from collected samples. Soil samples were collected from each of the soil borings SB-1, SB-2, and SB-3. The drill rig was used to penetrate the six inch thick asphalt for S13-1 and SB-2. Each of the borings was advanced to 4.5 feet below ground surface (BGS) using a stainless steel hand auger. Thisdepth was chosen because it is situated in fill materials found just above the water table (within the damp capillary fringe zone) at all three locations. A stainless steel drive sampler lined with a brass tube was then utilized to collect an undisturbed sample from 4.5 to 4.8 feet BGS.; Each sample tube of soil was then removed from the 'drive sampler and capped with teflon lined plastic end caps. These end caps were then secured to the tube via plastic electrical tape. The sample was then A - 1