Laserfiche WebLink
Geological Technics/ac. 1%� S%=P� <br /> WW Confirmation GW Sampling WP <br /> Project No.770.2 <br /> February 28,2011 <br /> March 1988—UST excavation deepened to 29 feet below grade surface(bgs). Excavation <br /> was filled with clean backfill. <br /> �..• April 1992—Three groundwater monitoring wells installed (MW-1 through MW-3), Wm. J. <br /> Hunter&Associates. <br /> May 1996—A single soil boring(LB-1)to 80 feet bgs installed, Lush Geosciences. <br /> September 1997- Well MW-4 installation, Wm. J. Hunter&Associates. <br /> *Pre-2001 data from Wm. J. Hunter&Associates documentation. <br /> August 2000—Two shallow wells (MW-5 & MW-6) and one deep well (MW-105) installed, <br /> Geological Technics Inc. (GTI) <br /> May 2002 -Two shallow wells (MW-7 &MW-8) and two deep wells (MW-104 &MW-106) <br /> installed GTI. &,/ 3,7-oo 5' <br /> Octobe,N05 Eleven Cone Penetrometer Test(CPT)boreholes advanced with depth discrete <br /> soil and groundwater sampling, GTI. <br /> 1992 to 1998—intermittent monitoring/sampling of wells MW-1 through MW-4. <br /> 2000 to present—quarterly/semi-annual groundwater monitoring& sampling of all site <br /> monitoring wells. <br /> The data compiled during the course of this investigation indicated that the soil and <br /> groundwater were impacted with diesel range petroleum hydrocarbons. <br /> In GTI's September 17, 2003 "Pilot Test for Soil Vapor Extraction" work plan GTI proposed <br /> a pilot test utilizing high vacuum (>25 inch Hg) soil vapor extraction (SVE). In an April 27, <br /> 2004 letter the SJC PHS/EHD denied the work plan on the basis that SVE was not applicable <br /> to diesel contamination and directed that a Site Conceptual Model (SCM)be developed. GTI <br /> staff subsequently met with SJC PHS/EHD staff on June 3, 2004 to discuss the challenge of <br /> remediating diesel contamination in low permeability soils. It was agreed that the SVE work <br /> plan and additional site characterization would be set in abeyance while SJC PHS/EHD <br /> would contact the Regional Water Quality Control Board (RWQCB) for guidance on <br /> remedial technologies. In a June 17, 2004 email correspondence, SJC PHS/EHD stated that <br /> RWQCB staff proffered that bioventing technology was utilized by the Air Force to address <br /> diesel releases. The email also included links to relevant technology websites. <br /> Upon review of the relevant data and updating the SCM with the October 2005 CPT <br /> investigation, GTI recommended that a pilot test be performed for evaluating a combination <br /> of bioventing with low flow biosparging at the Site. This would involve injecting air into the <br /> y subsurface to stimulate aerobic biodegradation of the petroleum hydrocarbons. The test <br /> would involve the installation of injection wells with associated infrastructure to sparge air <br /> into the subsurface and monitor air flow rates, pressure, vacuum and other parameters. The <br /> objective of the pilot tests would be to obtain enough data to design a treatment system to <br /> address the entire soil and groundwater plumes. <br /> -- GTI developed our June 9, 2006 "Bioventing with Biosparging Pilot Test" to meet this <br /> objective. The work plan also included provisions for performing a soil vapor extraction <br /> Geological Technics/tic. 2 <br /> 7702 Confirmation GW Sampling 2-25-1 l.doc <br />