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I OHMS Mr James L Barton July 27, 2005 Page 7 concentrations had reduced with the May 2005 influent sample but later learned that the May sample was inadvertently collected while open to dilution air ENSR field personnel collected a Inew series of samples on June 17, 2005 The influent concentration from the June 17th sampling event was 33 ug/L for TPHg, consistent with other recent sampling events ISince starting the SVE system in October 1999, the system has operated for a total of 8,235 hours and has removed approximately 8,767 pounds of petroleum hydrocarbons from soil I and groundwater ENSR intends to continue to monitor the system on a weekly basis utilizing a field instrument for monitoring concentrations of VOCs ENSR collects samples for laboratory analysis from the vapor streams (influent, midfluent, and effluent) on a monthly basis to Icalculate mass flow rates and destruction efficiencies Summaries of SVE system operational parameters, destruction efficiencies, and mass flow rates are presented in Tables 4 through 9 I ENSR has excluded the May sample data from this report as it was determined that the sample was diluted and, therefore, not representative of the vapor well influent stream ENSR will continue to collect vapor samples from the SVE system on a monthly basis to calculate mass removal ' Air Sparge System Status The AS system was started in October of 1999 as specified by CAO No 5-00-707 and operated continuously until October of 2003 Corresponding with the SVE system discontinuing operation, rthe AS system was allowed to operate every other week The AS system was returned to continuous operation corresponding with the restart of the SVE system on September 24, 2004 After the unscheduled shut down of the SVE system on November 30, 2004, the AS system was returned to operating every other week on December 6, 2004 ENSR returned the AS system to continuous operation after the SVE system was inspected and approved on February 17, 2005 The AS system has operated for approximately 17,688 hours since remediation at this site began in October 1999 through the most recent sampling date Remediation Svstem Effectiveness ENSR updates charts every quarter for groundwater monitoring wells MW-2, MW-3, MW-4, MW-6, MW-8D, MW-9/9R, MW-11, MW-12, and MW-25D for groundwater elevation and concentrations of TPHg and benzene These charts are included as Appendix H Each well has demonstrated overall decreases in dissolved concentrations of petroleum hydrocarbons . ENSR believes that continued improvements to, and operation of, the AS and SVE remediation ® Celebrating 35 Years of Excellence in Environmental Services