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NO FURTHER ACTION REQUEST COLBERG BOAT WORKS JUNE 2002 The results of the investigation were documented in Apex's report titled Results of Subsurface Investigation dated August 21, 1997 Colberg has been monitored quarterly for petroleum hydrocarbon constituents in the groundwater since July 1997 In September 1998, Apex submitted a remediation plan entitled Workplan for Pilot Test and Feasibility Analysis for removal of hydrocarbons from groundwater An Addendum to Workplan for Pilot Testing and Feasibility Analysis was resubmitted in January 1999, Prior to acceptance of the remediation plan,the County requested a mass balance calculation to determine whether remediation was necessary In April 1999, Apex submitted a report entitled Mass Balance for Remaining TPH G Upon review of the report,the County determined that the extent of contamination had not been delineated east of MW-3 � 11 Based on the response of the County,Apex submitted a Workplan far Additional Subsurface Investigation and Site Characterization dated June 9, 1999 On September 29, 1999,Apex personnel unplemented the Workplan and installed five geoprobes at the site to establish the extent of petroleum impacted groundwater east of monitoring well MW-3 The data obtained from the investigation was incorporated into a report entitled Estimated Mass of Petroleum Hydrocarbon Constituents Remaining in Groundwater, and submitted to the County on February 8, 2000 . GHH assumed environmental consulting responsibility for the site in May 2000 The County responded to the February 2000 Apex report in February 2001 by requesting additional soil and groundwater investigation east of MW-3 and soil boring SB-21 as shown on Figure 2 In April 2001,GHH submitted an Additional Assessment Workplan proposing installation of 6 geoprobes to complete the investigation requested by the County,which the County approved in the same month On January 8, 2002 GHH installed the 6 geoprobes (SB-25 through SB-30),which are incorporated into the Site Conditions and Site Characterization sections of this report A bibliography of all reports completed to date are contained in Appendix B SITE CONDITIONS Geology Regionally,the property is located within the Central Valley province - a large elongated northwesterly trending trough containing a thick accumulation of sedimentary rocks ranging in age from Jurassic to recent The Central Valley is divided into the Sacramento and San Joaquin basins with the dividing point between the two at the Mokolumne River Stockton is located within the northern portion of the San Joaquin Basin The Stockton fault, a northeasterly- trending fault zone,which crosses the valley at roughly right angles Just south of Stockton, is the . only signaficant structural feature m the area 2 i`