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Fortner Beacon Station No 12474 November 2, 2005 Stockton California Quarterly Groundwater Monitoring/Remediation Status Report y� ti collected from wells MW-13, MW-15, MW-16, MW-17 and VW-1 were also analyzed for 1,2-dichloroethane (DCA) and 1,2 dibromoethane (EDB) by Environmental Protection Agency(EPA) Method 8260B 'Groundwater-Monitoring Results=_ - Depth-to-groundwater measurements were subtracted from the surveyed TOC elevations to calculate groundwater elevations Groundwater elevation data, as summanzed in Table 1, were used to construct the groundwater elevation contour map shown on Figure 2 The groundwater flow direction in the dispenser island area vaned from northeastward to southeastward under a gradient of approximately 0 002 Groundwater-analyticalresults are summan— -mTablc 1-13enzene concentration data were used to construct an isoconcentration map as shown on Figure 3 Analytical reports are contained in Attachment C Historical groundwater level and analytical data collected prior to 1998 are summarized in Tables 1 and 2 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 modified 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 3, 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 The APCD issued Permit to Operate N-4941 on August 18, 2005 The Iocation of the remediation system compound and underground piping is shown on Figure 4 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 5 The VES is set up to extract vapors from vapor extraction wells VW-1 through VW-7 Soil vapor flow from each well is controlled by individual valves The air sparging system consists of two 7 5 cfin compressors and other associated equipment as shown on Figure 5 The air sparge system is set up to sparge air to sparge well AS-1 and monitoring wells MW-2 and MW-12 Air sparging was initiated on June 27, 2005 The VES reporting period for this report is June 27 to September 27, 2005 The VES operated for a total of approximately 52 days during this reporting penod Influent and effluent vapor samples were collected ^on�v_July 6, August �Y2, a'n,�d,. September 13, 2005 Analytical reports are contained iii-Attachment t�J =Vapor:-extraction system dare-hut'miai tzed-in Table 2-- - Dissolved Oxygen concentiations and Oxidation Reduction Potential data are summarized in Table-3 The average influent flow during the first quarter was approximately 82 standard cubic feet per minute Approximately 15,731 pounds of TPHg and 62 pounds of benzene were removed by the VES through the end of the third quarter reporting period • 474gmr Q3o5 Piojtc.t No 147448 2 HORIZON ENVIRONMENTAL INC