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f Mr Chuck Carmel rt t P4 March 23, 1994 Page 2 All groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G) and benzene, toluene, ethylbenzene, and xylenes (BTEX) by U S Environmental Protection Agency (EPA) Methods 5030/8020/DHS LUFI' Quarterly Monitoring Results and Discussion The General groundwater flow across the site is to the south with an average hydraulic gradient of 0 004 Water level data are listed in Table I Table 2 shows past and present hydraulic gradients and groundwater flow directions Figure 1 illustrates groundwater contours and the groundwater flow direction Well W-2B was not used for contouring, as this well is completed in a deeper zone than the other wells Well W-2A was not used in contouring because this well contained only a small amount of water that likely has collected in the end cap and is not representative of the water table surface The current south flow direction and gradient of 0 004 are within the ranges previously reported On November 16, 1993, the depth to water ranged from 62 94 feet to 65 93 feet Water levels in the monitonno wells increased an average of 2 86 feet between August 23, 1993, and November 16, 1993 • Current and historical analytical results are summarized in Table 3 The complete laboratory reports, including chain-of-custody documentation, for the quarterly sampling are presented in Exhibit B BTEX and TPH-G were not detected in any of the samples, the detection limits for the BTEX constituents and TPH-G are 0 5 and 50 mtt,rogiams per liter, respectively 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 Station 434 consists of a groundwater extraction and treatment system (GWETS) and soil vapor extraction and treatment system (SVETS) The GWETS consists of one groundwaterextraction well (E-1) with a designed pumping capacity of 1 gallon per minute Treatment of the extracted Groundwater is accomplished with two granular activated carbon vessels, each having 1,000-pound capacity Groundwater is extracted from the well via a submersible pump Discharge of the treated groundwater is to the city industrial sewer system under Wastewater Discharge Permit No 151 issued by the City of Lodi Public Works Department Installation and start-up of the GWETS occurred in October 1992 The GWETS was shut down on April 19, 1993, due to nondetectable concentrations of hydrocarbons in the water Use or disclosure of data contained on this sheet is subject to the restrtction spectJied at the beginning of this docionew 74�ATEP0RTSI.\0V93QTR RPT