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Beacon Station No. 3641 July 27, 2005 Stockton, California Quarterly Groundwater Monitoring/Remediation System Report groundwater level and purge data were recorded on the Doulos Groundwater Level Data and Sampling Information Sheets (Attachment B). Groundwater samples were collected from the wells MW-2, MW-4, MW-6, MW-9 through MW-13 and VW-7. The groundwater samples were submitted, under chain-of-custody documentation, to Kiff Analytical (Kiff), a California-certified analytical laboratory (ELAP No. 2236) located in Davis, California and were analyzed for total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene, toluene, ethylbenzene and total xylenes (BTEX), and the fuel oxygenate methyl-t-butyl ether (MTBE) by Environmental Protection Agency (EPA) Method 8260B. Groundwater samples collected from monitoring wells MW-9 through MW-13 were also analyzed for 1,2-dichloro ethane (DCA) by Environmental Protection Agency (EPA) Method 8260B. Results of Groundwater Monitoring Depth-to-groundwater measurements were subtracted from the surveyed TOC elevations to calculate groundwater elevations. Groundwater elevation data, summarized in Table 1, were used to construct a groundwater elevation contour map (Figure 2). Groundwater level data indicate flow in the immediate underground storage tank area was northwestward under an gradient of approximately 0.005. Analytical data are summarized in Table 1. TPHg, benzene and MTBE concentration data were used to construct isoconcentration maps (Figures 3, 4 and 5). The analytical report is contained in Attachment C. GeoTracker Electronic Data Deliverables The analytical electronic data deliverable (EDD) is uploaded by Kiff. The groundwater well measurement file EDD (GEO_WELL) for this quarterly monitoring event has been uploaded by Horizon. The GEO_WELL file upload confirmation sheet is contained in Attachment D. Vapor Extraction System Monitoring Construction for a vapor extraction system (VES) and an air sparging system was conducted in late 2004. The San Joaquin Valley Air Pollution Control District (APCD) issued a Authority to Construct permit in October 2004. Final equipment connections were made and final system preparations were conducted during first quarter 2005. Operation of the. VES was initiated on March 4, 2005. Final inspection of the VES was conducted by the APCD on May 19, 2005. Horizon submitted the Authority to Construct Inspection Report on June 21, 2005. Issuance of the Permit to Operate is expected during third quarter 2005. The location of the remediation system compound is shown on Figure 6. The VES consists of a positive-displacement blower rated at 250 cubic feet per minute (cfin), a ThermTech Vac 25 thermal/catalytic oxidizer and other associated equipment as shown on Figure 7. The VES is set up to extract vapors from vapor extraction wells VW-1 through VW-8. Soil vapor flow from each well is controlled by individual valves. The air sparging system consists of a 7.5 cfin and 641 gmrQ205.doe Project No. 1641.48 2 HORIZON ENVIRONMENTAL INC.