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from irrigation, and infiltration from septic systems. In addition, a sewage lagoon located in the Beaz Creek drainage about 3,500 feet upstream from Highway 50 reportedly contributed approximately 20,000 gallons per day of recharge to groundwater (RGI, 1999). Groundwater occurs in the limestone and the sandstone units. Field observations of cuts in limestone indicate that the groundwater flows primarily under perched conditions along shaley interbeds in the undisturbed Fort Hays and Smoky Hill Limestones. Vertical flow through these formations occurs along fractures and joints until shale layers are encountered directing the flow horizontally. This movement occurs until groundwater reaches incised stream channels or the Codell Sandstone, which appears to be the regional aquifer. Where the limestone formations have been mined out, the groundwater flows vertically down to the Codell Sandstone where unconfined water table conditions exist. Further vertical movement of the groundwater is impeded by the underlying Blue Hill Shale. The limestone beds of the Niobraza Formation dip approximately four degrees to the southwest. The direction of groundwater flow appears to generally follow the dip of the lithologic units in the area (Figure 4). Depth to groundwater has been determined from a series of wells and piezometers that have been installed at the site over time (Table 1). For the azea of the quarry that has previously been mined, depth to groundwater ranges from approximately 108 feet below ground surface (bgs) in monitoring well MW-8 to between 4 and 5 feet bgs in piezometer P2 (Table 2). The depth to groundwater below the top of the Codell sandstone ranges from approximately 4 to 5 feet in piezometer P2 to as much as 25 feet in MW-8. Groundwater elevations and the direction of groundwater flow aze affected by faulting that occurs throughout the site. The barrier, or "damming", effect of the faults can be observed from the variations in groundwater flow direction which indicate a change in flow direction on either side of a NE-SW trending fault that reportedly runs through the site (Figure 4). In 1998, RGI performed aquifer slug tests to estimate the hydraulic conductivity, K, of the aquifer. The slug tests were performed in MW-5, which was completed in the Codell Sandstone. Analysis of the slug test data was performed using the Bouwer and Rice (1976) method (RGI, 1999). Results of the analyses indicated that K of the sandstone is on the order of 1x10 to 4.Sx10b cm/s (0.3x10"2 to 1.3x10"2 fUd). The long recovery times after purging of monitoring wells (on the order of hours to days) also supports a low hydraulic conductivity for the Codell Sandstone unit. According to data collected by RGI (1999) the average gradient, i, of groundwater across the site is approximately 0.014. K-S (2001) indicates that ground water on the north side of the fault is flowing generally south with an average gradient of 0.029, while groundwater on the south side of the fault is flowing to the southwest with an average gradient of 0.015 (Figure 4). The porosity, TI, of sandstone ranges from about 5 to 15 while the effective porosity, Y)e, of sandstone ranges from about 0.5 to 10% (Domenico and Schwartz, 1998). Using an effective porosity of 5% and the relation: v=Kxi/fl° Groundwater velocity in the Codell Sandstone is approximately 0.3 to 1.3 fUyr. The volume of groundwater from the Codell Sandstone dischazging to the Arkansas River can be determined from: Q . yxAxfln where A is the cross-sectional area of the sandstone at the river. Assuming a sandstone thickness of 25 ft, a length along the river of 2,000 ft, and an effective porosity of 5%, goundwater flow into the Arkansas River BLASLAND, BOUCK 8 LEE, INC. 12/131°2 engineers & scienils l5 2-2 Gowdwe4r Monitorin8 Plan Il.dot