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Mr Kyle Christie y rt October 31, 1995 Page 2 s�t benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons as gasoline (TPH-G) by U S Environmental Protection Agency (EPA) Methods 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 August 10, 1995 was to the south under a hydraulic gradient of approximately 0 002 (Figure 1) The hydraulic gradient was somewhat flatter in the area of the soil vapor extraction wells Wells W-2A and W-213 are not used for contounng because they are screened in different zones than the other wells r Since groundwater momtonng began in 1988, the general groundwater flow direction has ranged from southwest to southeast at this site The hydraulic gradient measured this quarter is within the range of previously reported gradients Depth-to-water on August 10, 1995 ranged from 63 03 feet below the top of the well casing (TOC) in well W-8 to 65 90 feet below TOC in well W-9 Water-level elevations in all monitoring wells except W-9 decreased an average of 3 64 feet since the last quarterly monitoring event (May 18, 1995) The water-level elevation in W-9 increased 3 45 feet since May 18, 1995 However, the water-level elevation for well W-9 on May 18, 1995 is anomalous, and direct comparisons between the May 18, 1995 data and any . other data are not accurate Monitonng wells W-4 and W-2A were dry this quarter Summaries of depth-to-water measurements and calculated groundwater elevations are presented in Table I Table 2 lists past and present groundwater flow directions and hydraulic gradients for this site BTEX and TPH-G were not detected in any of the sampled wells, except W-213 Total xylenes were detected in well W-213 at 0 7 micrograms per liter (pg/L) The presence (or absence) of total xylenes in this well will be monitored in future sampling events 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 shows TPH-G and BTEX concentrations for this sampling event Status of Site Remediation This section provides a description of the remediation system and discusses the effectiveness of the remediation system operation Description The remediation system at ARCO Facility 434 consists of a soil vapor extraction and treatment system (SUETS) A ground water extraction and treatment system (GWETS) which was formerly in use at the site, was shut down on April 19, 1993, due to nondetectable concentrations of hydrocarbons in the groundwater The GAC vessels have been removed for use at another ARCO facility, and the effluent piping from the GWETS to the industrial sewer • was disconnected The connection point to the industrial sewer was capped to prevent any Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 2065\REPORTS\3RD95QTR DOC