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c <br /> ATC Associates Inc. <br /> 1117 Lone Palm Avenue, Suite B <br /> Modesto,California 95351 <br /> 209-579-2221 <br /> %TC Fax: 209-579-2225 <br /> ASS O C I ATE S INC. <br /> computer modeling results are presented in ATC's Addendum to Additional Site Evaluation and <br /> Request for No Further Action for Fayette Manufacturing Corporation, dated November 4, <br /> 2002. <br /> On April 5 and 8, 2004, an additional subsurface investigation consisting of three Geoprobe soil <br /> borings (GP-1, GP-2 and GP-3) and one cone penetrometer test boring (CPT-1) was conducted <br /> to evaluate the vertical extent of impacted soil in the vicinity of the former USTs and possible <br /> lateral migration of impacted groundwater between wells MW-4 and MW-5. The results were <br /> submitted in a Summary Report on Additional Subsurface Investigation, dated August 11, 2004. <br /> On January 10 and 17, 2005, ATC supervised the installation of two groundwater monitoring <br /> wells (MW-7 and MW-8). The wells were installed hydraulically downgradient with respect to the <br /> locations of the former USTs and are the most northerly monitoring wells at the site. A low <br /> concentration of xylenes in the groundwater sample collected from MW-7 was the only analyte of <br /> interest detected in groundwater samples collected from these wells on January 26, 2005. Refer to <br /> ATC's First Quarter 2005 Groundwater Monitoring Event and Well Installation Report, dated <br /> �-' April 20, 2005, for additional information. <br /> MONITORING WELL SURVEY, SAMPLING,AND GROUNWATER GRADIENT <br /> EVALUATION <br /> On April 1, 2005, Condor Earth Technologies, Inc. (California-certified Land Surveyor No. 7698) <br /> surveyed the locations and elevations of MW-1 through MW-8. The surveyed well casing <br /> elevations are indicated in Table 1. <br /> ATC personnel performed the latest quarterly groundwater monitoring of eight monitoring wells <br /> on October 20, 2005. Field work consisted of measuring depth-to-water levels in all wells, <br /> collecting groundwater samples from all wells, and submitting groundwater samples for <br /> laboratory analyses. Water level measurements were collected from groundwater monitoring wells <br /> MW-1 through MW-8. The depth to water ranged from 7.43 to 9.11 feet below top of well <br /> casings. The water level data were used to develop the groundwater elevation contour map <br /> (Figure 3). Shallow groundwater flow beneath the site was generally toward the north during the <br /> monitoring event. The average hydraulic gradient on October 20, 2005, was calculated to be <br /> approximately 0.002 ft/ft or approximately 11 feet/mile. The data indicate a groundwater gradient <br /> that is generally consistent with previous groundwater gradients observed at the site. A summary <br /> of groundwater monitoring data is presented in Table 1. Groundwater elevations are referenced to <br /> feet above mean sea level. <br /> sAEnviromnenW\I7861\rcports\4gmr2005.doc 3 ATC Associates Inc. <br />