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.: � ,.R «!ran:. dn?.a. .-ate,,ydu,`iia'>r-W' �ir,,K'', •§ -.,,:;7`.""u'.ad�Ji:,t7;y �s3wE- . g�Li�" R MY i and screened intervals were determined in the field based on data collected at thio time the wells were drilled. Each well was completed with a minimum of 15 feetof 0.020-inch,slotted well screen positioned to straddle the water table with five feet of screen above and at least 10 feet below she unsaturated/saturated interface. The assembled well pipe was installed through the 6.25 Ill augers and a#2/16 quartzite sand, a size compatible with the well screen slot size, was backfilled through the annulus. The filter pack was constructed to extend at least two feet above the top of the well screen. Above the filter pack,bentonite pellets were tremied to forth a 2.0 to 2.5 feet thick bentonite seal. Potable water was then added downhole to hydrate the bentonite. A bentonite/cement grout was then backfilled from the top of the bentonite seal to ground surface. The PVC casing was completed with a vented locking rap and covered by a flush mounted, steel protective curb box. The curb box was grouted in place to limit disturbance to the PVC well pipe. At least twenty four hours after completion of each monitoring well,the drilling contractor developed the wells using surge and bail techniques. Development continued until each well produced clear, sediment-free water. Between well locations, all downhole equipment was thoroughly steam cleaned, rinsed with isopropyl alcohol and rinsed with distilled water to prevent well cross- contamination. Groundwater Sampling and Analysis On September 23, 1991, approximately 72 hours after the wells were developed, groundwater samples from the three newly installed monitoring wells were collected. Groundwater was removed from each monitoring well until at least three well volumes had been evacuated and until field parameters of temperature, pH, and electrical conductivity were stabilized. The samples were sent to DHS certified hazardous waste laboratory and analyzed for BTEX by EPA Method 602, TPHD and TPHG by the DHS/LUFT Method (Modified EPA Method 8015), and total fecal coliform(requested by SJCPHS/EHD). A chain-of-custody record (Appendix B) accompanied the groundwater sample shipment from selection and preparation of the appropriate container at the r. laboratory, to the sample collection site and back to the laboratory. Each sample was individually labeled, recorded in the field notebook, immediately packed in ice, sealed inside an insulated shipping container and shipped by overnight courier to the laboratory. Groundwater Elevation and Product Thickness Measurements Prior to sampling, each well was checked for depth to water and free product thickness using an electric water level meter/free product interface probe. None of - the wells contained free product. All monitoring wells were surveyed to a single Fixed surface datum on site (later converted to an approximate elevation above sea level) in order to create an accurate groundwater elevation map establishing -- groundwater flow to be in a southerly direction (Figure 4). Hydraulic gradient across the site is notably flat (0.002 ft/ft) in the direction of groundwater flow. All elevation survey data are summarized in Table 1, LML/SY132.21/WS3 REV 0 4 r�