SITE INFORMATION AND CORRESPONDENCE_FILE 2

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r • August 2000 — Two shallow wells (MW-5 & MW-6) and one deep well (MW-105) installed, Geological Technics Inc. (GTI) • May 2002 - Two shallow wells (MW-7 & MW-8) and two deep wells (MW-104 & MW- 106) installed, GTI. • October 2005- Eleven Cone Penetrometer Test (CPT) boreholes advanced with depth discrete soil and groundwater sampling, GTI. • 1992 to 1998—intermittent monitoring/sampling of wells MW-1 through MW-4. • 2000 to present - quarterly groundwater monitoring & sampling of all site monitoring wells. • GTI conducted a set of bioventing, biosparging, soil vapor extraction and dual phase extraction tests on-site between November 26 and December 14, 2007 to find the best remedial methodology to address the residual diesel contamination in groundwater and soil. Four pairs of shallow/deep, injection/extraction well sets were installed to facilitate the bioventing test, and one deep air sparge well was installed for the biosparging test. • The results of the tests conducted during the above mentioned 20-day period was reported by GTI on March 5, 2008. SJCEHD in response to this report directed GTI to do further tests on Dual Phase Extraction (DPE) methodology as it appears more effective than bioventing and biosparging and the previous pilot test failed to quantify TPH-Gasoline and TPH-Diesel in the extracted soil vapor. • Geological Technics Inc. prepared a Pilot Test work plan dated October 30, 2009 in response to the San Joaquin County Environmental Health Department (SJCEHD) directive in their correspondence dated October 17, 2008. Geological Technics Inc. • Geological Technics Inc. prepared the Revised Pilot Test work plan dated January 23, 2009 in response to the San Joaquin County Environmental Health Department (SJCEHD) directive in their correspondence dated December 31, 2008. The Revised Pilot Test work plan was approved in their correspondence dated March 23, 2009. *Pre-2001 data from Wm.J.Hunter&Associates documentation. THE DATA COMPILED DURING THE COURSE OF THIS INVESTIGATION INDICATE THAT THE SOIL AND GROUNDWATER WERE IMPACTED WITH DIESEL RANGE PETROLEUM HYDROCARBONS. In GTI's September 17, 2003 "Pilot Test for Soil Vapor Extraction" work plan we proposed a pilot test utilizing high vacuum (>25 inch Hg) soil vapor extraction (SVE). In an April 27, 2004 letter the SJC PHS/EHD denied the work plan on the basis that SVE was not applicable to diesel contamination and directed that a Site Conceptual Model (SCM) be developed. GTI staff subsequently met with SJC PHS/EHD staff on June 3, 2004 to discuss the site. The challenge of remediating diesel contamination in low permeability soils was discussed at the meeting. It was agreed that our SVE work plan and additional site characterization would be set in abeyance while SJC PHS/EHD would contact the Regional Water Quality Control Board (RWQCB) for guidance on remedial technologies. In a June 17, 2004 email correspondence, SJC PHS/EHD stated that RWQCB staff proffered that bioventing technology was utilized by the Air Force to address diesel releases. The email also included links to relevant technology websites. Geological TechAics 11tc. April 16,2009