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No Further Action Request . ID Section 1 0 Former American Forest Products Facility URS Project No 17322736 Page 1-1 • 10 INTRODUCTION This report constitutes a request for no further action for the former American Forest Products Facility, 2801 West Lane, Stockton, California (site), based on existing data presented in previous closure request reports and additional data collected during 2005 to delineate the downgradient extent of the groundwater contaminant plume The principal field tasks described in this report are two rounds of downgradient groundwater assessment and a field survey for water supply wells within approximately 2,000 feet of the site The objective of the groundwater assessment was to further delineate the downgradient extent of 1,2- dichloroethane (1,2-DCA) in groundwater The work described herein was completed in accordance with the requirements presented by San Joaquin County in its letter of May 5, 2005, included as Appendix A of this report, in order to provide data demonstrating limited extent and stability of groundwater contaminants as a basis for site closure 11 BACKGROUND Two underground storage tanks were excavated and removed from the site in 1988 (Figure 1) Associated piping was excavated and removed from the site in 1991 Soil impacts were partially remediated in 1990 Groundwater monitoring of began in 1990, Table 1 provides construction details of monitonng wells A series of closure request reports document characterization of hydrocarbon impacts at the site via a series of investigations that began in 1985 (Dames & Moore, 1994, URS, 2001, 2002a, and 2005b The 2002 closure request, in particular, was based on data that indicated the site met the regulatory criteria provided at that time in Appendix B of the Tri-Regional guidance for designation as a "low-risk groundwater site"These cntena are as follows The leak has been stopped and sources removed or remediated, • The site has been adequately characterized, • The dissolved plume is not migrating, and chemical concentrations are not increasing with time, No water wells, deeper aquifers, surface water, or other sensitive receptors are likely to be impacted, and The site represents no significant risk to human health or safety ' The closure request reports demonstrate that these criteria have been met at the site with respect to the hydrocarbon impacts Data indicate the dissolved hydrocarbon plume is degrading and that the plume is not migrating Well surveys have not identified water wells in the vicinity that could be impacted by the plume, and the site does not pose a significant risk to water resources or human health and safety In discussions with Regional Water Quality Control Board (RWQCB) staff on February 13, 2002, the agency indicated it agreed that closure criteria were met with the exception of delineation of the extent of 1,2-DCA impacts in groundwater To fill that data gap, URS presented a work plan (URS, 2002b) proposing a direct-push sampling program at eight locations in the vicinity and downgradient of the former waste oil tank (Figure 2) The 2002 1,2-DCA work plan also provided for a cessation of quarterly . groundwater monitoring while the results of the investigation were being evaluated the San Joaquin E\1Proiects\URS\AFP\2005 DCA Investigationl IP Investigation Report\AFP 2005 Report WP TE-Rev02 doc