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Mr Kyle Christie February 27, 1996 Page 2 • Field and Analytical Methods EMCON personnel measured depth-to-water and product thickness (when present), purged each well to be sampled, and collected groundwater samples at the site Depth-to-water measurements and a check for free product were made prior to purging Before sampling, the wells were purged of a minimum of three well casing volumes or until evacuated using a pump or bailer Each well was sampled using a disposable bailer All groundwater samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons as gasoline (TPH-G) by U S Environmental Protection Agency (EPA) Method 503018020, and 8015 Modified Field data sheets and chain- of-custody documentation are included in Exhibit A Results and Discussion The general groundwater flow direction beneath the site on October 26, 1995, was to the north and northeast under a hydraulic gradient of approximately 0 004 (Figure I) Since groundwater monitoring began in April 1987, the general groundwater flow direction has ranged from north to east at this site The hydraulic gradient measured this quarter is within the range of previously reported gradients Depth-to-water on October 26, 1995 ranged from 9 28 feet below the top of the well casing (TOC) in well ATR-8 to 13 40 feet below TOC in well ATRA Since the last quarterly monitonng event (July 27, 1995), water-level elevations in all the measured monitoring wells have increased an average of 0 I9 feet Summaries of depth-to-water measurements and calculated groundwater elevations are presented in Table 1 Table 2 presents past and present groundwater flow directions and hydraulic gradients for this site Benzene and TPH-G were not identified in wells ATR-1, ATR-2, ATR-5, ATR-6, ATR-7, ATR-9, and TEX-1 Benzene was identified in wells ATR-4 and SMW-1 at concentrations of 7 micrograms per liter (pg/L) and 640 µg/L, respectively TPH-G was also identified in wells ATR-4 (600 fig/L), and SMW-1 (7,600 pg/L) These results are consistent with previous results Analytical results of groundwater samples are summanzed in Table 3 The complete laboratory report for the sampling event is presented in Exhibit A Figure 2 presents TPH-G and BTEX concentrations for the third quarter 1995 sampling event Site Remediation A soil vapor extraction and treatment/air sparging (SVET/AS) system has been constructed at this site An Authonty-to-Construct permit (Permit No N-3413-1-0, issued March 10, 1995 and expiring March 10, 1997) has been obtained from the San Joaquin Valley Unified Air Pollution Control District for operation of the SVET/AS SUET/AS system source testing was completed on December 15, 1995 Based on the results of the source testing, operation of the system began on January 6, 1996 Use or disclosure of data continued on this sheet is subject to the restriction specified at the beginning this document S 8 of 2043\REPORT514TH95QTR DOC