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j Stewart's Beacon Property Phase lI-Greund Water Assessment Proposal Page: 2 3.0 PROPOSED WORK PLAN Geological Technics proposes to install four monitoring wells. location of each proposed monitoring well is shown in the Site Map(Figure 2). The placement of these monitoring wells were chosen to best define the plurnes'dimensions. Since ground water gradient is to the north, geoxind water contamination will also move in that direction. The north boundary of Stewart's r roperty is only 90 feet from the tank. Monitoring well#1 was placed 50 feet north of the tank, leaving 40 feet between known contamination and the property boundary. Geologic,a!Tmhrdrs proposes to place these monitoring wells north of Stewart's property in hopes That the outer limits of the contamination can be found with a minimurn expenditure. Monitoring well#4 should be placed at least 120 feet down gradient(north)of the tank. MW#6 wit!be placed to the west of MW#4 in an arc corresponiing wit; MW#4. If slgnific:t contandnation is dztec.ed in any of these wells,additional wells may have to be installed to identify the.limits of the plume- These two monitoring wells(installed into the first aquifer)w- be constructed as follows. a Each well will extend to the bottom of the first aquifer and will be seated into the lower bounding clay layer at about 2C feet clef.,. The well casing infill be of 2-inch threaded joint PVC casing,factory periorated wish 0.04-inch slots. Perforations will extend no higher then 5 feet „ ✓ tt�;ow ground surface. The filter pack will be composed of medium aquarium sand and will extend from the buttom of the well through the perforated zone to about 1 foot above the perforations. An annular seat compose of bentonite will be plate above the filter pack. A surface seal of concrete will be placed above the annular sial and the well will be secured with a locking well cap ard water tight well cover. Figure 4 illustrates the general construction plan of these shallow mcaitoring wells. A hollow stem auger drill rig will be used for installation. ' r ! During drilling,soil samples will be collected to characterize the strata and correlate this work with the previous investigation. The monitoring well designed to test the second aquifer(MW#5)will be placed north of the tank,outside the upper aquifers contamination plume. Therefore,the location of this well will not be finalized until after the other wells have been installed and tested. If contamination does not occur in MW 44,it will be located adjacent to MW 44 as shown in Figure 3. In constructing this well,the upper aquifer will be caseL,•cfore drilling through the aquitard into the second aquifer(Figure 5). A large diameter hole will be drilled to a depth o`.xbout 21 feet using a 10-inch auger. The depth may vary slightly depending on the ground surface elevation and the depth of the interface between the sand(first aquifer)and the clay (aquitard)layer. Stewart's property has 2 to 3 feet of fill on its north side to level the property. After this hole has been bored,the auger will be removed and an 8-inch PVC casing (schedule 80)will be installed into the hole. The casing will be driven info the aquitard a distance of 1 foot forming a water-tight seal. This will isolate the upper water layer from the drill hole and prevent an interchange of ground water between the two aquifers. continue.down-through.the.second_aquifer_with.a.7.25-inch hollow_stem auger._______._.__— Continuous split spoon sampling will be performed through the second aquifer into its lower bounding day layer. Into this hole a 2-inch monitoring well will be installed. It will be N111 1111 mill Ing �� .