FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

GROUP REQUEST FOR BID (REVISED SCOPE) Project: Well Decommissioning PG&E McDonald Island Gas Storage Facility McDonald Island, CA RFB Release Date: June 5, 2009 RFB Response Date: No later than 9:00 a.m. June 9, 2009 General Scope of Work: Contractor shall provide material, equipment and personnel for decommissioning of wells at site. Site Background and Drilling Conditions: The site is located about eight miles west of Stockton. Pond 3 at the site was used for disposal of barite drilling muds and brines from installation of natural gas storage wells. Pond 3 was clean closed in 1994 and was backfilled, graded and vegetated with native vegetation. Groundwater monitoring occurred at the site from 1986 to 2008. 11 monitoring wells (MW), 9 piezometers (P), one well point(WP), 5 temporary piezometers(TPZ)and 4 water supply wells(CSD, TCD, WSD and ZFD)were monitored at various times throughout this period. Two attached figures labeled 1-2 show the approximate locations of these wells. Based on evaluations completed in 2008, the Central Valley Regional Water Quality Control Board (RWQCB) agreed with the conclusion that site groundwater and soil in the Pond 3 area currently have background concentrations of the former constituents of concern and are therefore no longer contaminated. RWQCB rescinded the Waste Discharge Requirements for the site in April 2009 and the agency is now allowing decommissioning of the wells. The wells that will be decommissioned include all MW, P, WP and TPZ wells(a total of 26 wells). The attached Table 1 provides known well construction details. Survey coordinates are available for all wells except P-6A. Additional details (borehole diameter, packing materials, etc.)are currently not available. The P-6A riser has been destroyed and the piezometer does not have visible surface features. If this piezometer is not located before work commences, contractor shall attempt to locate it by removing soil around its approximate location. Also, wells MW-1 RD, MW-3 and MW-9 have mounds of soil up to 5 feet in elevation around their casings that were left in place after pond closure. The total volume of this soil is estimated to be less than 4 cubic yards. These soils were analyzed for former constituents of concern at the site(sodium, chloride, barium and sulfate) and were found to have concentrations of barium and sulfate elevated above background concentrations but below hazardous waste characteristic criteria. The contractor shall remove the soil from around the well casings, and the casings shall be cut to ground level, before decommissioning begins. The soil shall be stockpiled at a location designated by PG&E pending PG&E disposal at a Class III landfill. Wells shall be decommissioned in accordance with San Joaquin County Environmental Health Department (SJCEHD) standards found at the following link: http://www.si-og v.orci/ehd/docs/odfNVell%2OSt2ndards.pdf. Because the site is no longer contaminated, SJEHD will allow the wells to be decommissioned by pressure grouting rather than overdrilling. Currently little vegetation exists within the former Pond 3 area. The backfill material in this area has a powdery consistency at the surface and readily compresses, which makes walking and equipment movement across this Page 1 of 3