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rl � <br /> ATTACHMENT A <br /> FIELD AND LABORATORY PROCEDURES <br /> Exploratory Drilling <br /> The soil borings for well installations were drilled using 8-inch hollow-stem auger drilling <br /> equipment to depths of approximately 28 feet below ground surface (bgs) or approximately <br /> 10 feet into first groundwater One Geoprobe® boring using direct push technology was <br /> continuously advanced and sampled to a depth of 39 feet bgs Borings were logged by an IT <br /> geologist using the Unified Soil Classification System and standard geologic techniques Soil <br /> samples for logging from the augured borings were collected at 5-foot depth intervals using a <br /> California-modified split-spoon sampler The sampler was driven a maximum of 18 inches <br /> using a 140-pound hammer with a 30-inch drop All soil samples for chemical analyses were <br /> retained in brass liners, capped with Teflon squares and plastic end caps, and sealed in clean <br /> Zip-lockkTM-style bags The samples were placed on ice for transport to the laboratory <br /> accompanied by chain-of-custody documentation All down-hole drilling and sampling <br /> equipment was steam-cleaned following the completion of the soil boring Down-hole <br /> sampling equipment was washed in a tri-sodium phosphate or alconox solution between <br /> samples <br /> The borehole created by the Geoprobe® was backfilled with neat cement utilizing a tremie <br /> pipe from the bottom to the surface <br /> Groundwater Monitoring Well Installation <br /> Four borings were converted to groundwater monitoring wells by installing 2-inch diameter, <br /> flush-threaded, Schedule 40 PVC casing with 0 020-inch factory-slotted screen Approxi- <br /> mately 20 feet of screen was placed in the bottom of the boring An RMC 43 sand pack, or <br /> equivalent, was placed in the annular space across the entire screened interval, and will <br /> extend approximately 2 feet above the top of the screen for the well A 2 to 3 foot bentonite <br /> transition seal was placed atop the sand pack, and a Portland cement seal will extend from the <br /> bentonite transition seal to the ground surface The Portland cement seal was emplaced by <br /> r <br /> tremie pipe in one continuous operation from the bottom of the interval to the top <br /> 9110051BISOLGW A - 1 March 17,1999 <br />