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�. W-101 Harlen Knoll February 2, 1990 Page 2 Shallow groundwater at the site was encountered at a depth of 12 feet below the asphalt- covered surface of the Ford Dealership. Regional groundwater flow direction is believed to be to the northeast. Based on this information, Murray & Associates proposes that a monitoring well (MW-1) be placed northeast of the former waste oil tank within 10 feet of the excavation. The remaining two wells will be placed on the property at the locations shown on Figure 1. WELL INSTALLATION Murray & Associates proposes to install all three groundwater monitoring wells down to a depth of 25 feet. The wells will be installed using a 10-inch diameter hollow-stem auger drilling rig. The wells will be constructed with 15-feet of factory slotted well screen located at the 7 to 22-foot depth interval. This will result in the screened intervals being placed so that 10 feet of screen will be below and 5 feet of screen will be above the water table. All three wells will use 4-inch diameter Schedule 40 PVC blank casing and slotted screen. Filter pack material and slot size will be engineered based on soil samples collected from the soil/water interface at the base of the tank excavation. Each well will be constructed by installing flush-threaded casing and slotted screen down through the hollow stem of the auger. Filter pack material will be placed by backfilling the annulus between the borehole wall and the well screen as the auger is retracted. Filter pack material will be placed to extend 2 feet over the top of the well screen. A 2-foot layer of bentonite pellets will be installed above the filter pack in the same manner as the filter pack material was placed. The bentonite seal will then be allowed to hydrate for approximately 30 minutes. Following hydration of the seal, a cement/bentonite grout will be pumped into place and will extend from the top of the seal to the surface. The well will then be completed below grade with the installation of a traffic rated. Figure 2 provides an example of the typical well to be installed during this phase of the investigation. Surveying Upon completion of all three wells, the areal location and casing elevation of each well will be surveyed and added to the existing site plan. Casing elevations will be used to obtain accurate groundwater elevations, and thus, flow direction. A total station surveying unit will be used to obtain the location and elevation data. Well Development Well development for the two new wells will be accomplished by swabbing the inside of each well with a surge block in a plunger-like fashion and then pumping the wells with a