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of small-sized material (silt and clay) in most of all recorded shallow sand sections at the site, a value of 0.25 was tentatively chosen for the effective porosity. Reference Head Unless the regional flow field is developed from boundary conditions, WhAEM2000 requires the head specification at one point within the model domain. Since useful boundary conditions are not available for this application, head was specified 500 feet southeast of Well A, a location not affected by pumping of the extraction well(s). Regional Gradient Unless the regional flow field is developed from boundary conditions, WhAEM2000 requires the specification of the direction and magnitude of the regional gradient at one point within the model domain. A northwesterly flow direction and an average gradient of 0.001 were assigned to the aforementioned point, 500 feet southeast of Well A,based on the review of recent and historical contours of equal groundwater elevation. Storativity The storativity of an aquifer is inconsequential for the solution of a steady- state problem. Therefore, it is not an input parameter. 5.2.2 Preliminary Capture Zone Results An extraction scenario was developed which uses one extraction well that would replace MW l. The new extraction well would be located at the northwest corner of the North Pond and is anticipated to have higher well yield than presently observed in MW 1 due to different well design as described below. Specifically, the preliminary capture zone scenario included one extraction well located at the northwest corner of the North Pond that was pumped at a rate of 25 gpm for 10 years. Input parameters are summarized in Table 5-1. The capture area is shown with particle path lines overlying the chloride isocontours (Figure 5-2). Particles located at the ends of the path lines will travel to the extraction well within 10 years. The capture zone extends beyond the salt-affected area to the north, east, and southeast; thus, shallow groundwater in these areas is indicated to be captured within the simulated 10-year period. As commonly observed with other groundwater remediation programs involving extraction,the duration of cleanup is likely to extend beyond that estimated with a simulated capture zone analysis due to preferential movement of the groundwater within the shallow zone in response to extraction at the planned extraction well site. 5.3 Test Well/Extraction Well Construction Following the completion of the evaluation monitoring program, a test well/extraction well (EWI)will be constructed. The preliminary location for EWl is near the northwest corner of the North Pond and will be completed in the shallow zone. EW 1 will be designed to perform a constant rate test to determine shallow zone aquifer characteristics in the vicinity of the ponds and also to serve as a future extraction well for groundwater remediation. The well will replace MWl as an extraction well, and MW 1 will be used as a corrective action monitoring location. A description of the aquifer testing program is described below. © LUHDORFF" & SCALMANINI CONSULTING ENGINEERS 9