WORK PLANS FILE 2 - Laserfiche WebLink

Home Browse Search

�.✓ or Staintec 76(Former BP)Service Station No. 11192 March 10, 2011 Page 5 water supply well located 1,100 feet northwest of the site. In April 2001, GRI conducted a well search and sensitive receptor survey (SRS) within a '/2-mile radius of the site. Based on the available data supplied by the California Department of Water Resources (DWR), three municipal wells were identified within the '/2-mile radius of the site. The closest well was located approximately 1,000 feet north-northwest of the site. A 500-foot radius, door-to-door SRS was also conducted, which involved the distribution of questionnaires to residences and businesses within the site area. None of the returned questionnaires indicated the presence of a water supply well within 500 feet of the site (GRI, Monitoring Well Installation Report dated September 26, 2001). Smith Canal is located approximately 1,300 feet south of the site, and the Calaveras River is located approximately 3,500 feet north of the site. Both of these surface water bodies are channeled, flow generally to the southwest, and drain into the Stockton Deep Water Channel (GRI, Groundwater Monitoring Well, CPT, and Ozone Microsparge System Installation Report dated May 9, 2003). PROPOSED SCOPE OF WORK The proposed scope of work detailed below includes an initial CPT investigation consisting of up to four borings off-site along Elmwood Avenue, and two borings on-site. The results of the CPT investigation will be used to determine the need for additional monitoring wells, as appropriate. The need and location of the monitoring wells will be addressed after the first phase of the investigation. The investigation areas are detailed below, and the proposed locations are shown on Figure 1. Three off-site CPT borings (CPT-4, CPT-5, and CPT-6) will be pushed along Elmwood Ave to provide stratigraphic and groundwater data for the three shallowest water-bearing intervals at the following approximate depths: A Zone - 15 to 20 ft bgs; B Zone - 35 ft bgs; and C Zone - 60 ft bgs, and deeper zones indentified in the 2002 CPT investigation (97 to 100 ft bgs and 121 to 124 ft bgs). If other potential water-bearing zones below the depth of the C Zone are identified in the field, samples will also be collected from these zones. Groundwater samples will be collected at these depths from separate boreholes advanced adjacent to each CPT boring with the exception of the A Zone at CPT-6. Due to the proximity of A Zone monitoring well MW-9 to CPT-6, additional A Zone data is not warranted at this location. CPT-4 will be the first location investigated during the mobilization, and groundwater samples from this location will be analyzed by the lab on a two-day turnaround time. The data from CPT-4 will be discussed with the SJCEND, COP, and BP, and a decision regarding the need for the additional boring (CPT-9)will be made prior to the completion of the field investigation. Two on-site borings (CPT -7 and CPT-8) will be pushed to collect stratigraphic and groundwater data at depths greater than the existing well network can provide, allow comparison to the data from previous CPT investigation conducted in 2002, and provide upgradient delineation. CPT-7 will be located adjacent to the existing C Zone well (MW-11, screened from 68.5 to 78.5 ft bgs), and will be pushed to a maximum depth of 140 ft (or refusal). Groundwater samples will be collected at water bearing depths identified at CPT-3 in 2002 (approximately 97 to 100 ft bgs and 121 to 124 ft bgs); samples from additional depths may be collected based on data obtained in the field. CPT-8 will be located in the west-central portion of the site to provide upgradient delineation information, and will also be pushed to approximately 140 ft bgs (or refusal). Groundwater samples will be collected from CPT-8 at the approximate known hydrologic intervals for A, B, and C described above, and the deeper intervals as described for CPT-7. A summary of the planned field work is presented below. Field and laboratory procedures are included in Attachment B. 11192 CPT Investigation WP 3-2011.doc