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Comparison of Groundwater Seepage Modeling in Approximate Original Contour and Geomorphic Valley Fill Design Nathan C. DePriest Excess spoil generated during surface mining in southern West Virginia is generally placed in headwater valleys. Known as valley fills, these structures are designed to move water rapidly through constructed drains to maximize geotechnical stability using the conventional design method termed Approximate Original Contour (AOC). Seepage from valley fills tends to be elevated with respect to calcium, magnesium, alkalinity and sulfates and there is evidence that, in high concentrations, these ions can contribute to stream degradation. New fluvial geomorphic principals are being researched to aid in reclamation alternatives to AOC designs. Geomorphic designs have proven successful in semi-arid regions; however, there has been little research performed into the application of this approach for eastern surface mining reclamation. This research investigated the differences in seepage quality and quantity between the AOC method and geomorphic designs on a permitted valley fill in southern West Virginia. The computational modeling involved geomorphic design for a proposed valley fill in southern West Virginia using commercial software. A comprehensive seepage analysis was then developed using a finite element method numerical model for assessing the groundwater flow characteristics of the fill rock for a 10 year time period. A resultant slope stability analysis was also performed. These analyses were performed for both the AOC and geomorphic fill designs. Differences in seepage and slope stability for the AOC and geomorphic fill were presented and discussed as a comparison of the two designs. Analysis criteria were chosen as a way to compare the results of the two fills in order to investigate if an advantage for one fill design was apparent. If an advantage of one fill was apparent, the magnitude of the advantage was quantified using a percent change in results. The results projected that higher water velocities (decreased residence times) occurred through mine spoil reclaimed according to the geomorphic fill design. Shorter hydraulic transit times through the spoil are expected to result in lower ionic concentrations in discharge water. The geomorphic fill had an advantage in the behavior of groundwater seepage for the majority of the time frame of the transient analysis, as well as in regards to slope stability. The geomorphic fill had peaks in advantage in water velocity at the toe of 1291.1% at year 3 and 1646.6% at year 7, peaks in advantage in water flux at the toe of 405.4% at year 3 and 1141.7% at year 7, peaks in advantage in maximum hydraulic velocity of 482.1% at year 3 and 1273.7% at year 7, and a peak in advantage in storage of2 4.3% in year 6 . For each of these criteria, the magnitude of the advantage for the geomorphic fill was much higher than the magnitude of any advantage for the AOC fill. This advantage was a result of the geomorphic fill moving water through the fill at a faster rate. This advantage in seepage could translate into an advantage in contaminant transport by water having less contact time with the fill material.