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Former Beacon Station No 12474 June 7,2005 Stockton California Results of Additional Groundwater Assessment • MW-15 and MW-16 locations were proposed in Work Plan Addendum dated December 22, 2003 In July 2002, Horizon proposed to initiate soil vapor extraction at the site for remediation of the vadose zone to an effort to begin removal of secondary source hydrocarbons prior to completion of the final subsurface investigation Horizon applied to the San Joaquin Valley Air Pollution Control District (APCD) for an Authority to Construct (ATC) permit for a soil vapor extraction system (VES) in April 2003 and was issued ATC permit No N-4941-1-1 in October 2004 Installation of a VES served by a ThermTech VAC 25 catalytic oxidizer was completed in the fourth Quarter 2004 The VES was inspected by APCD personnel in May 2005 and is currently being operated by Horizon Issuance of the Permit to Operate is pending APCD approval of the inspection VES performance data from March 3 through May 19, 2005 indicates approximately 12,088 pounds of TPHg have been extracted from the subsurface k'A' '' Quarterly groundwater monitoring has been conducted at the site since 1993 Quarterly groundwater monitoring data collected from 1998 through first quarter 2005 are summarized in Table 3 ADDITIONAL SITE INVESTIGATION The purpose of the additional groundwater investigation was to evaluate the lateral and vertical extent of petroleum-hydrocarbon impacts in soil and especially of lead scavenger 1,2-dichloroethane (DCA) in groundwater The work conducted included the drilling and installation of five groundwater monitoring wells Gregg Drilling and Testing, Inc (Gregg Drilling, license No C57-485165) of Martinez, California was retained to provide drilling and well construction services Well permit SR# 0036534 (Appendix A) was obtained from the SJCEHD to allow installation of the wells i AddtnIGWassmnt Project No 1474 15 3 HORIZON ENVIRONMENTAL INC