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y Mr Chuck Carmel y October 14 1993 Page 2 rlop 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 LUFT Quarterly Monitoring Results and Discussion The general groundwater flow across the site is to the South-southwest with an average hydraulic gradient of 0 003 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-213 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-southwest flow direction and gradient of 0 003 are within the ranges previously reported On May 25, 1993 the depth to water ranged from 61 95 feet to 64 67 feet Water levels in the monitoring wells increased an average of 0 69 feet between February 22, 1993 and May 25, 1993 Current and historical analytical results are summarized in Table 3 The complete laboratory reports for the quarterly sampling and the sampling of W-12 are presented in Exhibit A 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 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 remediatton 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 (gpm) Treatment of the extracted groundwater is accomplished with two granular activated carbon (GAC) 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 nondeteLtable concentrations of hydrocarbons in the water The SVETS consists of eight Soil vapor extraction wells (VE-1 VE-2 VE-3 VE-4, VE-5 VE-6, VE-7 and VE-8) and a soil vapor treatment system The soil vapor treatment system Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 7846\REP0RTS\MAY93QTR RPT Brown and Caldwell L 3fiSU,017LS