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1. INTRODUCTION
<br /> Former Exxon Retail Site (RS) 7-3942 is a vacant site located at 4444 North Pershing Avenue,
<br /> Stockton, California, on the southeast corner of the intersection of North Pershing Avenue and
<br /> Rosemarie Lane Three grades of gasoline and used oil were stored in four underground storage
<br /> 1 tanks, which were removed in July 1986
<br /> l� A Shell service station and a 7-11 food and gasoline service store are located on the southwest
<br /> and northwest corners, respectively, of the intersection of North Pershing Avenue and Rosemarie
<br /> Lane Previous laboratory analyses have consistently identified TPH-g and BTEX in
<br /> groundwater samples collected from MW8 and MW9, which are located adjacent to the Shell site
<br /> and the 7-11 site, upgradient and cross-gradient of former Exxon RS 7-3942
<br /> On 19 October 1995, groundwater from nine monitoring wells (MW 1, MW2, MW4, MW5,
<br /> MWS-MW 10, MW 12, and MW 13), four recovery wells (RW 1, RW2, RW3, and RW4), two
<br /> piezometers (PI and P2), two soil vapor extraction wells (V2 and V3), and one infection well
<br /> (IW 1) was purged and sampled Monitoring wells MW3, MW6, and MW7 were not sampled on
<br /> 19 October, as there was insufficient water to make well purging possible Figure 1 shows the
<br /> locations of all wells on and off the site, except MW 11, and the locations of former site facilities
<br /> Figure 2 shows the vicinity of former Exxon RS 7-3942 and the locations of all offsite wells
<br /> it
<br /> 2. SUMMARY OF RESULTS
<br /> On 19 October, wells were monitored for the presence of liquid-phase hydrocarbons, using an
<br /> optical interface probe The depths to water ranged from 24 37 feet to 29 97 feet below ground
<br /> surface The approximate groundwater flow direction on 19 October was to the north-northeast,
<br /> with a gradient of approximately 0 008 (Figure 3), which is consistent with previous groundwater
<br /> monitoring data for the site Groundwater elevations have decreased approximately 0 5 feet
<br /> since the previous quarter Groundwater elevation data for 19 October are presented in boldface
<br /> type in Table 1, along with previous data Field documents are included as Appendix A
<br /> After the depths to water were measured, the wells MW 1, MW2, MW4, MW5, MW8-MW 10,
<br /> p (
<br /> MW 12, MW 13, RW 1-RW4, P 1, P2, IW 1, V2, and V3) were purged by a vacuum truck and
<br /> sampled At least three well casing volumes of purge water were removed from each well After
<br /> purging, groundwater samples were collected with factory-cleaned disposable polyethylene
<br /> bailers Groundwater samples were collected in 40-m1 VOA vials The vials were labeled and
<br /> stored in an ice-filled cooler and transported under chain of custody Groundwater samples, a
<br /> field-prepared rinse blank, and a laboratory-prepared trip blank were submitted to Sequoia
<br /> Analytical, where they were analyzed for Total Petroleum Hydrocarbons as gasoline (TPH-g) by
<br /> DHS-modified EPA Method 8015 and for benzene, toluene, ethylbenzene, and xylenes (BTEX)
<br /> and methyl t-butyl ether (MTBE) by EPA Method 8020
<br /> The analytical results for the samples collected on 19 October are presented in boldface type in
<br /> Table 1, along with previous data The laboratory analytical report and chain-of-custody
<br /> documentation are included as Appendix B
<br /> WP61 73942Q1095 3 I
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