Laserfiche WebLink
3.0 FIELD ACTIVITIES <br /> 3.8 Backfilling and Site Restoration <br /> Backfill soil was obtained from the Allen Quarry borrow area, located approximately 12 <br /> miles northeast of Lodi,California near the corner of Peltier and Tully Roads. According to <br /> the quarry attendant, the backfill material was derived from previously undeveloped <br /> pasture land. Two four-point composite soil samples were collected and analyzed for the <br /> same parameters as outlined in Section 3.7.2. All of the soil samples were non-detect for <br /> BTEX and petroleum hydrocarbons, except for TPH-d.TPH-d was detected at <br /> concentrations of 5.8 and 5.5 mg/kg in Allen Quarry#1 and#2,respectively.The low-level <br /> detections of diesel could be attributed to residual fuel from on-site equipment such as <br /> bulldozers and other vehicles.The results of the analysis are summarized in Table 4. <br /> The excavation was first backfilled by placing 3/4-inch drain rock from the bottom of the <br /> excavation to a depth of about 5 feet bgs. Following placement of the drain rock,a geotextile <br /> fabric was placed. Backfill soil was then moisture-conditioned to meet the optimum <br /> moisture conditions and placed above the geotextile fabric in loose 12-inch lifts to match <br /> surrounding grades.Backfill lifts were not compacted to specific engineering standards as <br /> engineered compaction would not be consistent with the surrounding agriculture land use. <br /> Because engineering backfill standards were not applied,any future development of the <br /> area with new structures,utilities or foundation systems would require a geotechnical <br /> engineering investigation and evaluation in order to prescribe appropriate pre-construction <br /> recompaction and foundation design requirements,as appropriate. <br /> The remaining active features at the site (located in the southern portion of the site) are a <br /> concrete valve vault and aboveground valve stem stations connected to the remaining active <br /> gas lines. The existing valve stem stations will be retained as an easement by PG&E.An <br /> outline of the final site layout is illustrated on Figure 5. <br /> 3.9 Monitoring Well Installation <br /> In a letter dated December 30,2004,PG&E requested CVRWQCB approve the installation of <br /> one new shallow groundwater monitoring well (MW-7) and the abandonment of three <br /> offsite perimeter wells (MW-1,MW-3 AND MW-5).Groundwater at the site and the <br /> effectiveness of the soil removal activities will be monitored at new well MW-7 and at <br /> existing onsite monitoring well MW-4 and piezometer PZ-1. <br /> The proposed location of the new well (MW-7) is presented on Figure 5. MW-7 will be <br /> located near former well PZ-3 and will be installed just south of the footprint of the former <br /> production fluids tank in the southwestern corner of the station. This well will be installed <br /> within two months of receiving CVRWQCB approval. <br /> SFO1(THORNTON COMPLETION REPORT_6-21-05.DOC) 3-7 <br />