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3 2 1 Groundwater Table Monitoring Well Construction A C-57 licensed drilling contractor will use a truck-mounted hollow stem auger drillling rig to drill 8- inch diameter soil borings for the installation of the four groundwater table monitoring wells All of these proposed wells will consist of approximately 15 feet of two-inch diameter, Schedule 40, flush-threaded and machine-slotted (fl 020-inch) polyvinyl chloride (PVC) well screen Since groundwater is anticipated at approximately 20 feet bgs, the well screen interval will span from approximately 12 to 27 feet bgs Blank PVC casings will thread into the tops of the well screens and extend to the surface This proposed construction is consistent with the construction of the three existing monitoring wells ' Filter packs of Monterey#3 graded and washed sand will be placed around the well screens and approximately two feet above the tops of the screened intervals (i e , 10 feet bgs) The wells will be surged and purged by the driller, following the placement of the sand packs and prior to the installation of the well seals Periodic surging and purging of each well will continue until at least five well volumes have been removed Overlying the sand packs two feet of hydrated bentonite chips will be placed within the annular spaces between the boreholes and the well casings Over the hydrated bentonite, surface seals of neat cement grout will be installed The tops of the wells will be secured with water-tight locking caps and traffic-rated, flush-mount street boxes 322 Cased Second-Groundwater Monitoring Well Construction The deep monitoring well will be installed to investigate the sandy gravel groundwater-bearing zone, identified in SB-1 at a depth of between approximately 43 feet bgs Prior to installing the deep monitoring well, a conductor casing will be installed to prevent cross-contamination from the overlying first groundwater-bearing zone A C-57 licensed drilling contractor will use a truck-mounted hollow stem auger drillling rig to drill a 15-inch diameter soil boring to a depth of 40 feet bgs for the installation of a 10-inch diameter steel conductor casing As shown on the soil boring log for SB-1 (Appendix B), the base of the conductor would be set within a silty clay aquiclude The annular space between the bore hole and conductor casing will be filled with neat cement, placed with a tremae pipe, and the cement will then be allowed to set for at least 24 hours before continued drilling and installation of the deep groundwater monitoring well 10