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I� I 7.0 EXCAVATION OF SOIL BORINGS AND SOIL SAMPLING Environeering, Inc. will oversee three (3) additional soil borings and installation of groundwater monitoring wells in the area of the former diesel USTs excavation site. The soil borings, as well as the conversion to groundwater monitoring wells, will be supervised by a registered geologist who will prepare boring logs and the necessary boring permits will be obtained as needed. These borings will be of continuous core technique and advanced using a nominal 8-inch diameter truck mounted hollow-stem auger. With continuous core technique, the auger will be inserted into the ground and the soil samples collected and extracted to provide a continuous core sample. The soil samples can then be taken from any depth. Evacuated soils will be monitored for the presence of petroleum hydrocarbons using a portable photoionization detector (PID), as well as by observing and smelling the material for field- evident petroleum hydrocarbon contamination. Soil cuttings will be placed in DOT-approved 55-gallon steel drums, properly labeled and left onsite pending laboratory results. - For the scope of this work, the investigation will continue to a depth of 50 feet until two (2) -I consecutive samples do not show contamination by field measures, with soil sampling at 5 foot intervals starting at 15 feet below grade. A minimum of four (4) samples will be selected for analysis for TPHg, TPHd, TPHo, BTEX and MTBE, at least two (2) of which will be from the saturated zone. In addition, a groundwater sample will be secured for analysis for TPHg, TPHd, TPHo, BTEX, MTBE, TBA, DIPE, ETBE and TAME. Two (2) borings (MW-1 and MW-3) will be converted to 2-inch groundwater monitoring wells, constructed of 2-inch flush threaded Schedule 40 PVC casing, up to a maximum 20 feet of 0.01-inch or 0.02-inch factory-slotted well screen. The top of the screen will extend iup to 3 feet above the encountered groundwater level to account for seasonal fluctuations. The well casing will be inserted through the augers to a point a few inches above the borehole terminus where it will be suspended until the well is secured within the sand pack. Sand (#2 or#3) will be poured through the augers in one- to two-foot lifts up to about two feet above the top of the perforated casing. One- to two-feet of bentonite pellets will be placed above the sand, and activated with tap water. This bentonite plug will be set above the filter material to prevent the grout from entering the filter pack. The seal will be finished Environeering, Inc. Project No. 98-012.01 8 i ._