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Geological Technics Inc. V Page 2 Additional Pilot Test Work Plan Project No.770.2 October 30,2008 • 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. �- i *Pre-2001 data from Wm.J.Hunter&Associates documentation. The data compiled during the course of this investigation indicate4that the soil and igroundwater are impacted with diesel range petroleum hydrocarbons. 2.0 SITE CONCEPTUAL MODEL A Site Conceptual Model (SCM) dated August 23, 2004 was developed and submitted for regulatory review. In accordance with the SJC PHS/EHD directives the SCM was updated to ' reflect new data obtained from additional field investigation. GTI submitted our April 20, 2006 "Site Conceptual Model (March 2006 Revision)" to reflect the new information obtained by the installation of eleven CPT borings on October 28 - November 3, 2005 The following sections summarize the geology, hydrogeology and contaminant distribution at the site. 2.1 Geology • The geology of the site consists primarily of alternating layers, lenses and interstratified beds of clays, silts and sands. Units containing gravels are less frequent. Fine grained Y g �' q sediments dominate over course grained sediments. • Figures 4 and 5 provide a geologic interpretation of the units observed in the borehole logs. Note: The cross sections were developed using data gathered by different individuals utilizing different methodologies. Therefore, they need to be looked at as one of several possible interpretations of actual site conditions.) The cross sections include lithologies divided into fine grained units (slits and clays) or coarse grained units (sands ( ' and gravels). See Figure 3 for cross section locations. • Figure 4: Geologic Cross-Section A - A' illustrates the subsurface from the southwest to northeast sections of the subject area. The section displays the predominantly fine grained soils at the site. A significant sand layer is present.in_the location,of-wells M.W-4 &_MW,7 .at a.de th of 40 -_45_feet b s. We redrew the cross section to keep the data � I