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G1 (11 28 January 2005 AGE-NC Project No 96-0232 Page 3 of 8 vapor meter equipped with a photo-ionization detector(PID Thermo Environmental 580B, 10 0 eV, calibrated to isobutylene)and were visually described on boring logs in accordance with the Unified Soil Classification System(USCS) A boring log for MW-20 is included with Appendix B General lithology beneath the site is depicted in cross sectional view E-E'on Figure 3 2 4 EQUIPMENT DECONTAMINATION The hollow stem augers were steam cleaned prior to bore hole advancement Sampling tools and brass sleeves used for sample collection were thoroughly washed with a solution of Alconox, and were thoroughly rinsed with clean tap water prior to each sampling run At the conclusion of field activities,all rinseate generated from decontaminating the equipment was placed in properly labeled DOT-approved model 17H 55-gallon drums and was stored on-site in an area lacking public access 2 5 MONITORING WELL COMPLETION Soil boring MW-20 was dual-completed as a ground water monitoring well utilizing two separate sets of 2-inch diameter, schedule 40, blank polyvinylchlonde (PVC) well casing and perforated, 2-inch diameter PVC well casing (0 020-inch slot) The deepest section of well casing(MW-20B) was first installed by placing the entire well casing assembly through the hollow stem of the augers to the total depth of the boring Then the filter pack (No 3 Lonestar Lapis Luster sand)was placed adjacent to the screened casing, from the bottom of the boring to a point approximately two feet above the top of the screen, the augers were incrementally raised as the sand was slowly poured down the annulus between the well casing and the inner wall of the hollow stem auger Following filter pack placement, a surge block was inserted into the well casing and was alternately raised and lowered(surged)repeatedly for approximately 20 minutes to settle the filter pack Thereafter,3/s-inch diameter coated bentonite pellets (Pell Plug TR-30) were slowly poured down the annulus to form a transition seal above the bottom well casing assembly and filter pack, the transition seal was allowed to hydrate for a minimum of 30-minutes before well construction activities continued Following the 30-minute hydration period, the uppermost section of well casing (MW-20A) was installed by placing the entire well casing assembly through the hollow stem of the augers The filter pack was placed adjacent to the screened casing from the bottom of the well casing assembly to a point approximately two feet above the top of the screen Following filter pack placement, the uppermost well casing assembly was surged for approximately 20 minutes Afterwards, approximately three feet of bentonite chips (transition seal) were placed above the filter pack hydrated with clean tap water, then the remaining annular space was backfilled with portland type II cement (grout seal) An as-built monitoring well-construction diagram is included as Figure 5 Advanced GeoEnvi ron mental,Inc