ARCHIVED REPORTS_XR0006692 - Laserfiche WebLink

Home Browse Search

Third Quarter,2002 Quarterly Groundwater Monitoring Report Canepa's Car Wash,Pacific Avenue.Stockton,CA Page 2 • FIELD OBSERVATIONS On July 1, 2 and 3, 2002, Condor representatives made field observations at the 12 site monitor wells (MW-1 through MW-11 and MW-12d), and at the nine soil vapor extraction (SVE) wells. Field observations included water level measurement (Table 1, below), appearance of samples (color, clarity, and presence of petroleum product sheen or phase in samples), and collection of water quality field parameters. Field observations are included in the field forms, attached. GROUNDWATER ELEVATIONS AND GRADIENT The locations and top of casing elevations of the monitor wells were surveyed on November 26, 2001. The well locations are referenced to the NAD 83 datum and the well elevations are referenced to the NAVD 88 vertical datum from NGS benchmark JS 1384. Groundwater elevation contours for the shallow monitor wells (MW-1 through MW-11) are shown on Figure 2, attached. The groundwater gradient is approximately 0.004 ft/ft to the east-northeast as measured between monitor wells MW-6 and MW-3. A hydrograph of historic groundwater elevations is attached as .Figure 3. It should be noted that well screens for shallow monitor wells MW-I through MW-8 were drowned. Table 1 Groundwater Elevation Data (July 1,2002 Well Casing Well Collar Depth to Groundwater Screen WELL Elevation Water Elevation Interval (feet) (feet) (feet) (feet-bgs) MW-1 50-70 15.48 33.93 -18.45 MW-2 50-70 15.29 33.65 -18.36 MW-3 50-70 15.53 34.27 -18.74 NIW-4 50-70 15.83 34.36 -18.53 MW-5 50-70 14.71 33.36 -18.65 MW-6 45-65 14.89 32.94 -18.05 bIW-7 45-65 15.80 34.10 18.30 MW-8 45-65 15.31 34.07 -18.76 MW-9 25-45 14,84 33.54 -18.70 NIW-10 2545 14.72 32.67 -17.95 MW-11 25-45 15.12 33.32 -18.20 NIW--12d 100-110 14.99 33.54 -18.55 LABORATORY ANALYTICAL RESULTS The groundwater samples collected from the monitor and SVE wells were analyzed for BTEX, TPH-G, and MTBE by Excelchem Laboratories, Inc. of Roseville, California. The current monitor well groundwater analytical results included in Table 2, on the following page, are generally consistent with the historical results (Attachment C). The SVE well groundwater analytical results are generally consistent with historical results, except the BTEX concentrations detected in samples collected from SV- I and SV-9 are lower and the MTBE concentrations detected in samples collected from SV-4 and SV-9 are much higher than previously detected. Benzene and MTBE iso-concentration contour maps are • included as Figure 4 and Figure 5, respectively, in Attachment A. The highest concentrations of BTEX constituents, MTBE and TPH-G were generally detected in the samples from the SVE wells, and a petroleum sheen was noted on the groundwater purged• water from SV4. The groundwater sample �s -- i«1 CONDOR