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cimlogicat recknics lac. 1 Page 5 Sinclair&Thompson Property Soil Gas Survey Report +r January 29,2007 In a letter dated March 15, 2006, Ms Duncan recapped the worked performed at the site and suggested the data be used to proceed with evaluation of the site for closure. After some discussion via email it was determined the site may need to be evaluated for risk from vapor Lo intrusion. In a letter dated May 17, 2006, Ms Duncan proposed the option of either requesting closure (if no further data was required) or conducting a soil gas survey to determine the risk of vapor intrusion. L. GTI submitted the Active Soil Gas Investigation Work Plan on August 18, 2006. Ms Duncan in a letter dated August 29, 2006 approved the work plan, with a minor modification. The budget was approved and permits obtained during the first part of the fourth quarter. The project was delayed twice due to rain, as the sampling event required at least three consecutive days of clear weather. The work proposed in the August 2006 Active Soil Gas Investigation Work Plan was performed on January 5, 2007. The following report documents the activities and analytical L. results of the soil gas survey. 3.0 SAMPLING ACTIVITIES AND RESULTS 3.1 Summary of Activities 3.1.1 Boring Clearance GTI obtained a Well Permit (SR# 48873) from the San Joaquin County Environmental v Health Department on November 13, 2006. The permit is included as Appendix A. ' The subsurface was cleared of utilities by marking the area with white paint and notifying Underground Services Alert (USA) of proposed work. No public utilities were found within 200 feet of the soil gas investigation area. The locations of the septic and liquid propane ' lines that service the residence were known and avoided. 3.1.2 Obstacles and Delays Weather was the largest obstacle to performing the scope of work outlined in the August Lo 2006 Active Soil Gas Investigation Work Plan. The investigation was postponed twice due to an active rain season. �. 3.2 Soil Gas Sampling and Analysis 3.2.1 Sampling Locations and Rationale �• Five locations were proposed for a soil gas investigation in an effort to determine the presence and concentration of gasoline related constituents in the vapor phase. An additional location was sampled to delineate the extent of the vapor phase constituents detected in SG-1. The soil gas survey locations (SG-1 thru SG-6) are shown on Figure 2. r. Lo