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Ceologicaf?ecFinics Inc. *Former Moresco Property %mI Page 3 Report- Remedial Action Project No.: 251.3 February 6, 1998 filter pack surrounded and extended two feet above the 0.040" screened interval and was topped by a two foot granular bentonite transition seal installed on top of the filter pack and hydrated. A surface seal was achieved by pumping a neat cement grout(augmented with<4% bentonite) via a tremie tube. ` 2.1.5 Thermal Oxidizer Installation The Authority to Construct was issued on October 21, 1997 for the vapor extraction remedial system. Geological Technics Inc. installed the Thermal Oxidizer at the end of October and La completed the piping from the extraction well and recharge wells. The TO was started and tested for efficiency in early November. Arrangements were made for inspection by the SJVUAPCD and SJC PHS/EHD. LM 2.2 Thermal Oxidizer Efficiency Testing Startup and adjustments of the system were finished by the end of November and an inspection by the San Joaquin Valley Unified Air Pollution Control District (SNUAPCD) was conducted on November 12, 1997. At this time the VETS was drawing off of the air recharge wells to add oxygen to the subsurface and to dry out the soil. Lab results of samples taken on November 12 indicated the Thermal Oxidizer was meeting required efficiency standards. A letter was sent to SJVUAPCD along with the lab results and a. calculations on December 4, 1997. The calculations show that the TO was meeting efficiency standards. This letter is included in Appendix E. The TO was switched to pull off of VEW-1 on November 16, 1997. The vapor concentrations were allowed to equilibrate and influent and effluent air samples were collected on November 19, 1997. The calculations show that the TO was meeting efficiency standards. The data and calculations are included in Appendix B. u Another permit requirement is the bimonthly monitoring of influent and effluent vapor concentrations by a district approved detection device. GTI uses an OVM, whid'h is a field portable photo ionization detector that uses a 10.0 eV lamp, to detect compounds with ionization potential below 10.0 eV (hydrocarbon range). A copy of the soil vapor extraction monitoring log is included in Appendix C. +.� 2.3 Radial Influence Testing On December 30, 1997 GTI personnel mobilized to the site to conduct a radial influence test of L. the vapor extraction system. This test was designed to determine the effective distance from the vapor extraction pipes that the gasoline is being removed. To do this vacuum gauges were attached, at the manifold,to the air recharge wells. In summary, it was determined that there was good cross site influence. The vacuum readings measured in each of the recharge wells was as follows: • AR-1 2.4"of H2O • AR-2 1.2" of H2O +- • AR-3 2.3" of H2O This indicates sufficient vacuum past the edges of soil plume.