ARCHIVED REPORTS XR0008615 - Laserfiche WebLink

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1- INTRODUCTION 0 Exxon Retail Site (RS) 7-0137 is located at 1605 South El Dorado Street, Stockton, California, on the southwest corner of Second and South El Dorado streets The site is an active service ' station that has three double-walled fiberglass gasoline underground storage tanks (USTs) The site currently contains seven groundwater monitoring wells (MWI--MW7) and two vapor extraction wells (VEW1 and VEW2) The seven groundwater monitoring wells (Figure 1) are ' sampled quarterly Groundwater sampling at Exxon RS 7-0137 has been conducted regularly since 1992 A soil f vapor extraction system operated at the site from November 1995 to February 1996, which extracted soil vapor through five wells (VEW I, VEW2, MW2, MW3, and MWS) and abated the petroleum hydrocarbons with a catalytic oxidizer unit The catalytic oxidizer unit was removed in March I996, following a decline in the concentrations of extracted hydrocarbon vapors On 16 October 1996, the seven groundwater monitoring wells were purged and sampled ' Samples were analyzed for petroleum hydrocarbons 2. SUMMARY OF RESULTS The depth to water in each well was measured prior to purging and sampling Liquid-phase hydrocarbons (LPH) were not detected in any of the wells Groundwater elevations at the site ranged from 24 30 to 23 20 feet below mean sea level Groundwater elevations have decreased approximately 1 27 feet since the previous gauging on 24 April 1996 The approximate / groundwater flow direction was to the southeast at a gradient of approximately 0 002 Gauging J data and calculated groundwater elevation's from 16 October 1996 are presented in boldface type ' in Table 1, along with previous gauging data, and shown in Figure 1 Field documents are included as Appendix A After the depths to water were measured, each groundwater monitoring well was purged with a 2-inch PVC pipe attached to a vacuum pump until at least three casing volumes of groundwater were removed from it Samples were collected with factory-cleaned disposable polyethylene bailers The samples were poured into 40 ml glass VOA vials, which were then preserved in an ice-filled cooler A field-prepared sampling equipment rinse blank and a laboratory-prepared trip blank were stored and transported in the cooler with the groundwater samples The samples were handled and transported under chain of custody The groundwater samples were delivered to Sequoia Analytical and analyzed for Total Petroleum Hydrocarbons as gasoline (TPH-g) by Cal EPA-modified EPA Method 8015 and for benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Method 8020 Table I lists the analytical results for this quarter (in boldface type) and for all previous quarterly samplings TPH-g was detected in the samples collected from MW2, MW3, and MW5, at concentrations of 52,ug/L, S7µglL, and 130µg/L Xylenes were detected in the sample collected from MW3, at a concentration of 17 µglL Benzene was detected in the sample collected from MW6, at a concentration of 2 4 gg/L No TPH-g or BTEX compounds were detected in the samples WP61 70137 Q1096TX 3 I 1