ARCHIVED REPORTS_XR0008223 - Laserfiche WebLink

Home Browse Search

Closure Request Addendum Report 3 1,2-DCA Investigation July 22,2002 Former American Forest Products Site,Stockton,California Page 3 of the wells where 1,2-DCA was previously detected. 1,2-DCA was not detected in samples from locations along the downgradient perimeter(HP-6,HP-7 and HP-8). r' PCE was reported at three of five sampling locations, all situated on the downgradient fringe of the study area The concentrations ranged from 2.3 µg/]L(HP-6/50)to 4.4µg/L(HP-7/50). PCE has not been detected in previous samples collected from existing monitoring wells. 4.0 DISCUSSION AND CONCLUSIONS Only two VOCs, 1,2-DCA and PCE, have been detected at the site. The lateral distribution of 1,2-DCA is limited to a small area within a sixty-foot radius of the northeast comer of the former maintenance facility. 1,2-DCA has never been detected in the upgradient monitoring wells, indicating again the impacts have a limited areal distribution. Concentrations of 1,2-DCA are `= extremely variable within the area with detections. Concentrations at three of the locations are below or near the EPA MCL of 5 pg/L, indicating that impacts are minimal. The decline in 1,2-DCA concentrations with depth at location HP-1 is duplicated at the well cluster DMW-5 and DMW-6, where i historical data consistently indicate that the higher concentrations are reported in samples collected closer to the water table. These data indicate that a zone of higher impacts does not appear to be located at depth. PCE appears to be limited to the perimeter of the study area, as shown in Figure 3. PCE has never been detected at locations upgradient of BP-6,BP-7, or BP-8, suggesting that the PCE does not appear to be related to the 1,2-DCA detections. The reported PCE concentrations are below the EPA MCL of 5 µg/L, s indicating that the detected PCE represents a minimal impact. Based on the available data, site closure is recommended. The VOCs detected in groundwater have a very �.` limited areal extent, and most concentrations are below the EPA MCLs. There do not appear to be any water wells in the vicinity that could be impacted by the limited zones of VOC impacts. (see Appendix B). T.1 The site does not appear to represent a significant threat to water resources, or human health and safety. fv 5.0 REFERENCES California State Water Resources Control Board,2000. Water Quality Goals, August. URS,2001. Closure Request Report,Former American Forest Products Stockton Facility, Stockton,California, July 3 L URS, 2002. Work Plan for 1,2-DCA Investigation, Former American Forest Products Stockton Facility, Stockton, California, April 2. y GAAMREPORMCA_Final_rpt.doc