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WESTERN 6E0-ENGINEERS � PROTOCOL FOR GROUNDWATER MONITORING WELLS Water samples taken during tank removal at the Desert Petroleum site showed gasoline type contaminants (see Table 1 and Figure 3) . Therefore remediation is required, beginning with the installation of groundwater monitoring wells. The primary purpose for monitoring well installction is to provide groundwater access for sampling equipment and monitoring instruments to enable identification and quantification of various constituents if present. Well construction will depend on the chemical composition of the groundwater system and contaminants present. Monitoring wells will be installed using accepted pricedures and materials of construction. Much of the data --equired to determine groper groundwater monitoring well installatio:-i will be obtained from subsurface soil borings. General Requirements In the placement of groundwater monitoring wells, considerations must J_ be given to the location and type of the contaminant, the contaminantJ point source(s) , the groundwater gradient, flow direction, flow velocity and location of surface obstructions such as private business, private residences and other demographic considerations. Construction materials selected, and well design will also depend on ; the above parameters, but may be influenced by many other factors. These include water and soil corrosivity, pH, suseptibility of casing material to degradation from contaminants in or on the groundwater, the w,r probability of the well being used for pumping or injecting remedial fluids , and the length of time the well is expected to be used. i All groundwater- monitoring and/or remedial wells installed at the Desert Petroleum site, a former Mobil Oil Corporation service station, will include consideration of all of these parameters. A 7-7/8 inch hollow--stem auger will be used to drill each groundwater well. Each well wilt be drilled to a depth of approximately 26 feet, or about 10 feet below the present water table. Well Resign Groundwater wells will be constructed of polyvinyl chloride (PVC) casing and slotted pipe. Fifteen feet of factory--machine--slotted casing will be fatted with a cap and placed at the bottom of, each of 1 the borings. The blank pipe will be connected to the slotted pipe and extended to approximately 6 inches below the ground surface of each of the borings. A locking, protective well covering will then be installed slightly above the paving surface. All lengths of pipe , both slotted and blank, will be connected by threaded joints. Details of well design parameters are listed in Table 2.