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Mr Chuck Carmel September 7, 1994 Page 2 Quarterly Morutoring Results and Discussion The general groundwater flow across the site is to the south with an average hydraulic gradient of approximately 0 006 Water-level data are listed in Table 1 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 southerly flow direction and gradient of 0 006 are within the ranges previously reported On June 23, 1994, the depth-to-water ranged from 62 07 feet to 64 91 feet Water-levels in the monitoring wells decreased an average of 2 43 feet between March 22, 1994, and June 23, 1994 with the exception of well-2A Well-2A, which has been dry since August 1993, registered a water-level at -20 30 feet This indicates a positive change in the water-level since the last measurement The reason for this change is unclear The next quarter's water-level measurements will be used to verify this change 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 A Benzene and TPH-G were detected in wells W-2A and W-3 The detection limits for benzene and TPH-G are 0 3 and 10 micrograms per liter (Pg/l), 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 groundwater extraction 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 sheer is subject to the restriction specified at the beginning of this document 13MREP0RTS\v';D94QTR RPT