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\../ •..� Field Report Monitoring Well Installation Grantline Plaza Tracy, California On February 27 and 28, 1991, ROY F. WESTON INC. (WESTON) conducted a site investigation at the Grantline Plaza site at 350 West Grantline Road in Tracy, California. This investigation was performed to gain information on the possible presence of petroleum hydrocarbon compounds in groundwater at the site. All work was completed as detailed in the WESTON Work Plan dated November 27, 1991. Three soil borings were drilled at the site and monitoring wells were installed within these borings. The wells were designated MW-1, MW-2 and MW-3. All well locations were measured to the nearest foot with respect to permanent on-site structures and are shown on .=figure A-1. Borings MW-1, MW-2 and MW-3 were drilled to a total depth of 20 feet below ground surface (BGS) using hollow stem auger techniques. Soil returned to the surface as cuttings was used to describe the types of sediments present. Lithologic lags for the soil borings are presented at the end of this report. All devices used to drill the borings (including augers, bits, stainless steel knife, etc.)were decontaminated prior to first use and between uses for each sample. Auger flights and bits were decontaminated by steam cleaning, whereas all smaller tools were washed in an alconox/water 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 to the surface during the drilling was also placed into labeled 55-gallon steel drums. All drums were left on-site. Monitoring wells were installed in all borings. The monitoring wells installed are of four inch diameter schedule 40 PVC. Fifteen feet of screened section (0.02 inch slot size)was placed in each well. In monitoring well MW-1, the screen was placed from 3.5 to 18.5 feet BGS and a screw-on end cap was placed below this. A sant,, pack (#3 sand) was placed from the total depth of the boring (20 feet BGS) to 2.5 feet BGS. The screened zone of monitoring well MW-2 is 4.0 to 19.0 feet BGS with a screw-on end cap at the bottom. The sand pack (#3 sand) was placed from 20 to three feet BGS. The screened zonr, of monitoring well MW-3 is from 4.0 to 19.0 feet BGS with a screw-on end cap at w the bottom. The sand pack (#3 sand) was placed from 20 to three feet BGS. In each hole, a one foot thick layer of bentonite chips was laid on top of the sand pack and saturated with water. Concrete was used to seal each hole above the bentonite plug and at the surface to support a flush mounted locking Christy box. The well casing of each well was capped with a four inch locking cap. All well casing (blank and screened pipe) A - 1