ARCHIVED REPORTS_XR0003239 - Laserfiche WebLink

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2 2 1 Monitoring Well Construction, Development and Elevation Survey Mitchell Drilling installed all four wells to total depths of approximately 35 feet bgs All four wells were constructed with 20 feet of two-inch diameter, Schedule 40, flush-threaded and machine- slotted (0 020-inch) PVC well screen, spanning from 15 to 35 feet bgs Blank PVC casings were threaded into the tops of the well screens and extended to the surface Mitchell Drillinginstalled filter packs of Monterey#3 graded and washed sand within the annular P Y spaces between the well screens and boreholes, and two feet above the tops of the screened intervals (i e , 13 feet bgs) The driller surged and purged the wells, following the placement of the sand packs and prior to the installation of the well seals Periodic surging and purging continued until the amount of suspended sediment in the groundwater decreased and stabilized and/or until at least five well volumes had been removed ' Overlying the sand packs, Mitchell Drilling placed two-foot layers of hydrated bentonite chips within the annular spaces between the boreholes and the well casings Over the hydrated bentonite, surface seals of neat cement grout were installed The tops of the wells were secured with water-tight caps and traffic-rated, flush-mount street boxes On August 12, 2002, Morrow Surveying (Land Surveyor License#5161) surveyed the newly- installed wellheads Morrow Surveying located the wells and other site features, and measured ' the elevations of the tops of the well casings to the nearest 0 01-foot, referenced to City of Stockton Benchmark#27 The surveyor's report is included as Appendix B 1 2 2 2 Soil Sampling and Analysis During the drilling of MW-1 and MW-2, undisturbed soil samples were collected at 5-foot intervals using a modified California split-spoon sampler lined with two-inch diameter by six-inch long brass or stainless steel sample sleeves With the rig tower down during the drilling of MW-3 and MW-4, soil samples were collected at the surface from the drill cuttings Given that soil samples were previously collected from near the former dispenser at Geoprobe boring G-1, the soil encountered during the drilling of MW-3 was not contained for laboratory analysis A Ramage Environmental geologist logged each of the soil samples for hydrogeologic and lithologic characteristics ' according to the Unified Soil Classification System and screened each sample for organic vapors using a PID c= 8