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lIfINICX_�-IfRNf8 Mr. Charles Leubner 6 February 1998 Page 3 Based on information provided by Mr. Harlin Knoll of PHS/EHD regarding groundwater levels and construction details of monitoring wells in the vicinity of Stagg High School, it is estimated that MW-1 will extend to an approximate depth of 30 to 40 feet below ground surface. The boring will be drilled until a clay layer is encountered or to a maximum depth of ten feet below the top of the shallow aquifer. Qualitative Field Screening To provide a preliminary indication of possible contamination, a portable organic vapor detector will be used to monitor for the presence of organic vapors in soil collected from the borings. This field screening method consists of filling a Zip Lock plastic bag to about one-third it's capacity with soil and sealing the container. After allowing sufficient time for the soil vapor to equilibrate with headspace, the bag will be opened enough to allow for insertion of an organic vapor analyzer probe. The field monitoring will be conducted using an OVA equipped with a flame ionization (FID) or a photoionization detector (PID). The concentration of organic vapors detected by the OVA will be recorded on the boring log. Field screening will also include documenting visual indications for the presence of contamination, such as staining, discoloration, and/or chemical sheens. Monitoring Well Construction The monitoring well will be constructed with two-inch diameter Schedule 40 PVC casing and well screens. The well will be constructed to provide 5 feet of screen above the saturated zone and 10 feet below the saturated zone. Using the hollow stem augers as a tremmie pipe, sand will be poured in the annulus between the well casing and the auger to form the filter pack around the screened interval. The sand will be extended two to four feet above the top of the screen. Three feet of 3/8 inch bentonite pellets will be placed above the filter pack as part of the annular seal. These pellets will be hydrated with distilled water and allowed to sit for approximately 30 minutes. The remaining annular space will be filled with a cement slurry mixture containing less than 5% bentonite. The well will be completed by placing a locking cap over the PVC well casing beneath the ground surface. A water resistant flush-mounted steel security cover will then be installed at the ground surface. The monitoring well will be developed by hand bailing and surging to set the filter pack. Water will be removed until it is free from sediments. A minimum of ten well volumes of water will be removed from the well. Upon completion of well development and after allowing for the aquifer to equilibrate at least 48 hours, the monitoring well will be sampled. Immediately prior to sampling,