WORK PLANS - Laserfiche WebLink

Home Browse Search

logo Additional Groundwater Investigation Work Plan rr 419 S.Main Street,Manteca,CA June 25,2003 Page 3 plume at the site. This work plan addresses the work necessary to adequately define the extent of the %" contaminant plume. Detailed site background information is included in Appendix B. 3.0 CPT AND DIRECT PUSH BORINGS This section includes a description of the site preparation and CPT and direct push boring procedures to be used for collecting groundwater samples. Laboratory analytical results of the groundwater samples will be used to determine the lateral and vertical extent of groundwater contamination at the site. 3.1 SITE PREPARATION Condor will complete boring permit applications and an encroachment permit application and obtain the required permits from the SJCEHD and the City of Manteca prior to the commencement of fieldwork. Condor will schedule and coordinate all field activities through the property owner (Boyett), the SJCEHD, L and the City of Manteca. The proposed boring locations will be marked with white paint and Underground Service Alert (USA) will be notified at least 72 hours in advance of the fieldwork to locate, identify, and mark underground utilities in and near the work area. However,because companies contacted by USA may not identify utilities past private property lines and into the site, it is the responsibility of Boyett to locate, identify, and mark any utilities on their property. 6W Condor will supervise the advancement of four deep CPT boring pairs (eight borings total—two at each of two locations) and five shallow direct push (hydropunch) borings to further investigate the lateral and vertical extent of groundwater contamination at the site. Prior to commencement of each day of fieldwork, a +� tailgate safety meeting will be held and a site specific Health and Safety Plan will be discussed with, and presented to, all field personnel for their signatures. 3.2 CPT BORING PROCEDURES CPT boring pairs will be advanced at four locations to an anticipated depth of approximately 125 feet bgs. Two CPT boring pairs will be advanced to evaluate the vertical extent of groundwater contamination in the `" immediate vicinity of the USTs. A third CPT boring pair will be advanced to evaluate the vertical extent of groundwater contamination in the predominant down-gradient direction of the USTs in the vicinity of monitor well MW-7. The fourth CPT boring pair will be advanced to evaluate the vertical extent of groundwater contamination at the anticipated leading down-gradient edge of the plume. The boring immediately west of the site property boundary is located on private property. The proposed CPT boring pair locations are shown in Figure 3, Appendix A. It is possible that the borings will meet refusal before the anticipated total depth is reached. At each CPT boring pair location, the first boring of each pair will be used to investigate the lithology of �+ the site at that location. An electric piezocone will be pushed downward into the subsurface by the CPT rig. Measurements of the cone bearing pressure, sleeve friction, and dynamic pore water pressure will be recorded at approximately two-inch intervals to provide a nearly continuous geophysical log. The lithologic �+ interpretations from the CPT borings will be compared and correlated to identify potential horizons that are laterally extensive and relatively conductive of groundwater(clean sand) and/or potential horizons that may act as relative groundwater flow barriers (clay and silt) i.r The second boring at each pair location will be advanced within a few feet of the first boring to collect discrete groundwater grab samples from horizons identified in the geologic logs from the first borings. N4� CONDOR r