ARCHIVED REPORTS_XR0004448 - Laserfiche WebLink

Home Browse Search

Groundwater Investigation,Monitor well Destruction and Installation,and Interim Remediation Pump Test Report Boyett Petroleum,419 S.Main St,Manteca,CA January 30,2004 Page 11 4.2 DRILLING PROCEDURES ' A Condor geologist was on site to supervise the work. Prior to commencement of fieldwork, a tailgate safety meeting was held and a site-specific Health and Safety Plan was discussed with, and presented to, all field personnel for their signatures. ' The initial scope of work consisted of the destruction of monitoring wells MW-4 and MW-5; the installation of a replacement monitoring well for MW-4; and the installation of a four-inch extraction well (EW-1) in the northwest corner of the property. The scope of work was modified after results of the CPT investigation indicated that the construction of MW-1 (Figure 6, Appendix A) was potentially allowing for increased vertical migration of petroleum hydrocarbon contamination into the lower groundwater zone. Condor contacted Mr. Wong of the SJCEHD by telephone and requested authorization to destroy ' MW-1 to eliminate the vertical conduit between the upper and lower groundwater zones. In addition, Condor requested authorization to install two four-inch diameter monitoring wells, one screened in the upper groundwater zone and one screened in the lower groundwater zone, in the vicinity of MWA. The ' two wells would be-used to monitor groundwater in the area previously monitored by MWA, and could also be used as groundwater extraction wells. Mr. Wong gave verbal authorization to Condor to destroy MW-I and to install the two additional wells. Consequently, MW-1 was properly destroyed and two four- inch monitoring wells (MW-10 and MW-11) were installed. In addition, the construction of EW-1 was modified from that proposed in the Interim Remediation Work Plan. The proposed construction of EW-1 would have allowed five feet of slotted casing to be above and 20 feet of slotted casing below the static 1 water table level at the time of the well installation. This design would have mimicked the construction of MW-1 by providing a conduit between the upper and lower groundwater zones. Consequently, the design of EW-1 was revised so that the well was screened entirely in the lower water groundwater zone. Drilling • services were provided by West Hazmat Drilling of Anaheim, California. 4.2.1 Monitoring Well Destruction Procedures On October 29, 2003, monitoring wells MWA, MW-4, and MW-5 were destroyed by over drilling the wells with eight-inch outside diameter, continuous-flight, hollow-stem auger and removing all well construction materials. The three monitoring wells were of two-inch FVC construction. Monitoring well MW-1 was installed a total depth of 36.5 feet, MWA was installed to a total depth of 26.5 feet and MW-5 was installed to a total depth of 26.5 feet. The traffic boxes were removed prior to over-drilling the wells. MW-1, MW-4, and MW-5 were over-drilled to 39, 28, and 30 feet bgs, respectively, to ensure removal of all well construction material. Neat cement was tremied into the boreholes from the bottom of the borehole to the surface, and an asphalt cap, approximately six inches thick, was placed to the ground surface. The traffic boxes and the well construction materials were removed from the site. ' The hollow-stem auger and other down-hole equipment were decontaminated between borings by steam cleaning to prevent cross-contamination. Stearn cleaning rinsate was placed in DOT-approved 55-gallon drums, sealed, labeled, and left on site where they will remain pending laboratory analyses and disposal. ' 4.2.2 Monitoring and Extraction Well Installation Procedures Three groundwater monitoring wells (MW-4R, MW-10, and MW-11) and one groundwater extraction ' well (EW-1) were installed on October 30, 2003 (Figure 2,.Appendix A). The well borings were drilled using a ten-inch outside diameter, continuous-flight, hollow-stem auger. Monitoring well construction graphics are included as part of the geologic boring log for each well (Appendix B) and construction ' .A..,. A, AAAV AA1Vl21LVA111� auu QlWaction wells are provided in 1 able 4, on the following page. ' '� CONDOR