SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

4 Phase 3 will consist of groundwater sampling from CPT borings completed in both the Upper Horizon and Middle Horizon within private properties to define the lateral extent of the groundwater trichloroethene(TCE)plume(target date: 15 May 2001).This activity will require right-of-entry agreements with landowners,which will be acquired by the Sacramento District U.S. Army Corps of Engineers,real estate office(CESPK-RE). Therefore,the CPT groundwater sampling effort on private properties will be performed in a separate effort following the domestic potable well sampling and the Bird/Lovely Road CPT groundwater sampling efforts,which are both targeted for approximately 15 February 2001. Background and Site-Specific Sampling Efforts Results of the sampling effort of the recently installed groundwater monitoring wells and CPT probes on the Robertson Property(LM 154 through LM 158 CPO383 through CPO398)east of the DDJC- Tracy Annex (see Radian memo to CEHNC dated 3 May 2000), show TCE detected in the Upper Horizon(from 7.9 to 9.8 micrograms per liter[pg/Ll)at levels exceeding regulatory guidelines (maximum contaminant level [MCL]for TCE is 5 pg/L).Table 1 shows the results of the CPT sampling effort conducted in October 1999 and monitoring well results from the 1QOO sampling event.The monitoring wells,CPT borings,and associated analytical results are shown on the attached site map. The monitoring wells were installed east of the previously]mown northeasterly extent of the TCE groundwater plume to monitor the effectiveness of capture by the existing OU 1 extraction wells located along Banta Road.The CPT borings and groundwater sample collection were performed to provide additional monitoring points for tracking the movement of the TCE plume.Based on the results from these investigation activities, additional groundwater samples are required to determine the northeastern extent of the groundwater plume. Phase 1 —Four principle land owners have been identified as necessary contacts for the sampling of private domestic potable wells within the potential TCE groundwater plume area: the Robertson family(this private well is already being sampled as part of the on-going groundwater monitoring program), the McClellan family,the Graham family, and the Union Pacific Railroad Company(see address information page and site map figure).A letter of request will be sent to landowners by the DDJC department of public relations asking for locations of potable wells on their property and for authorization to conduct water sample collection from the wells.Following property owner agreement, samples from private wells will be collected and analyzed by an off-site laboratory. Phase 2—Additional groundwater investigations will be performed along Bird Road to the east and Lovely Road to the north.These investigations will consist of collecting groundwater samples from CPT borings installed in both the Upper Horizon and Middle Horizon at proposed locations P-1 through P-7(see site map). Samples will be analyzed by an off-site laboratory.These proposed CPT locations have been selected in an effort to characterize the lateral extent of TCE groundwater contamination northeast of DDJC-Tracy.Permanent groundwater piezometers will be installed along the perimeters of Bird Road and Lovely Road(to be performed under a separate effort)to monitor residual TCE levels and support the WES modeling effort. If groundwater contamination is found by this investigation,the boundary condition piezometers for the WES modeling effort may be required to be moved further east than Bird Road and Lovely Road;final locations will be based on investigation results and input from WES.Therefore,proposed piezometer locations shown on the site map may be moved based on groundwater results from CPT locations P-I through P-7. 2