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Chevron Products Company Page 1 firmer Chevron Service Station #9-5775, 301 West Kettleman Lane. Ladi. California _„_ �_- Mav 15.2002 INTRODUCTION SECOR International Incorporated (SECOR), on behalf of Chevron Products Company (Chevron), presents operating data for the groundwater extraction (GWE) system at 301 Kettleman Lane, Lodi California (Figure 1). Chevron discharges treated groundwater at the subject site under City of Lodi Wastewater Discharge Permit #310. This report presents April 2002 data collected between March 29 and April 30, 2002. GROUNDWATER EXTRACTION SYSTEM Extraction and treatment of groundwater was initiated on July 3, 2000. The GWE consists of extraction wells EX -1, EX -2 and EX -3 (Figure 2). These wells are equipped with submersible pumps connected through mechanical piping to a series of granular activated carbon (GAC) vessels prior to an industrial sewer discharge point. Pumping through the wells from areas affected by petroleum hydrocarbons prevents migration of these hydrocarbons off-site. A treatment system schematic is shown on Figure 3. To assess effectiveness of the GWE system, process samples were collected weekly during this reporting period. Sample locations include an influent port (INFL), prior to the first GAC vessel, between the first and second GAC vessels (MID -1), between the second and third GAC vessels (MID -2), and prior to discharge (EFFL) to the industrial sewer. During these sampling events, INFL, MID -1, MID -2, and EFFL samples were • analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethyl - benzene, and total xylenes (BTEX compounds), methyl tertiary butyl ether (MtBE), tertiary amyl methyl ether (TAME), ethanol, methanol, ethylene dibromide (EDB), and 1,2-dicholoethane (1,2 -DCA). Maximum concentrations of detected constituents are presented below. Current and historical analytical results are presented as Table 1. Sampling Port Maximum Constituent Concentration (gg/1) Aril 3 through April 30, 2002 MtBE I TBA EtBE TAME Ethanol Methanol INFL 150 <5.0 12 1.3 <5.0 <100 MID -1 <0.50 <5.0 <0.50 <0.50 <5.0 <50 MID -2 <0.50 <5.0 <0.50 <0.50 <5.0 <50 EFFL <0.50 <5.0 <0.50 <0.50 <5.0 <200 Explanations: < indicates the constituent was not present at or above the method reporting limit shown Between March 29 and April 30, 2002, the GWE system discharged a total of 389,424 gallons of treated groundwater over a period of 32 days (Table 2). As of April 30, 2002, the GWE system has treated a total of 2,345,247 gallons. Calculated discharge rates during the April monitoring period ranged from 6.59 to 10.41 gallons per minute (gpm). During the April monitoring period the system extracted approximately 0.1 pounds of TPHg, 0.001 pounds of benzene, and 0.5 pounds of MtBE. To date, the system has extracted approximately 7.7 pounds of TPHg, 0.2 pounds of benzene, and 83.1 pounds of . MtBE. Plots of GWE system mass removal trends and influent groundwater TPHg, benzene, and MtBE concentrations versus time are shown on Figures 4 and 5 ]AChevron1957751Periodic Monitoringl0 & M\Reports\Monthly\Discharge Repons120021April 20021April 2002 DR.doc