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14 May 1999 <br /> AGE-NC Project No 97-0343 <br /> Page 4 of 6 <br /> be covered with Teflon sheets, capped and sealed with tape Each preserved sample sleeve: will be <br /> labeled with the boring location,depth,time and date Appropriately sealed and labeled samples will <br /> be placed on ice in a chilled container and transported under chain-of-custody to a DHS-certified <br /> laboratory <br /> Soils encountered in the borings will be visually classified by an AGE geologist in accordance with <br /> the Unified Soil Classification System (USCS) Additionally, soil samples with be field-screened <br /> for the presence of volatile organic compounds using an organic vapor meter equipped with a photo- <br /> ionization detector (FID) precalibrated to isobutylene <br /> 33 SOIL BORING ABANDONMENT <br /> Borings not completed as wells will be permanently sealed to prevent vertical migration of <br /> contaminants Soil borings will be abandoned by backfilling with portland cement from the total <br /> depth to surface grade A tremmie pipe will be used for backfilling bonngs exceeding 25 feet in <br /> depth or where ground water is present in the boring <br /> 3 4 MONITORING WELL COMPLETION <br /> Following completion of drilling a pilot boring northeast of the former UST cluster area, a 2-inch <br /> diameter Schedule 40 PVC 0 010-inch slotted well screen and casing will be installed A 20-foot <br /> section of well screen will be installed, extending approximately 15 feet below and 5 feet above the <br /> top of the ground water table The filter pack material, consisting of pre-washed #2/16 Lonestar <br /> sand,will then be added extending from the bottom of the borehole to approximately two feet above <br /> the screened interval Following placement of the filter pack, the well will be surged to assist in <br /> settling the filter pack Additional sand will be added if settling of the filter pack occurs <br /> A bentonite seal will be placed above the filter pack from 43 to 35 5 feet bsg The bentorute seal will <br /> beformed by pouring bentonite chips into the annulus and allowing them to settle on the filter pack <br /> Bentonite chips will be hydrated in approximate two-foot lifts using five gallons of water <br /> Approximately 0 5 feet of filter pack sand will be placed on the bentonite, and a second screened <br /> interval will be installed from approximately 35 to 15 feet bsg, with blank casing extending to the <br /> ground surface A sand filter pack will thenbe installed as described above up to a depth of <br /> approximately 13 feet bsg A nominal 1 to 2-foot bentonite seal will be placed over the filter pack, <br /> as described above,[o minimize the potential of grout penetration into the screened section of the <br /> well The bentonite chips will be allowed to hydrate for a minimum of 20 minutes prior to grouting <br /> The remaining annular space will be filled to near the ground surface with a portland cement gro <br /> Advanced GcoEnvironmcntai,im <br />