2010-10-22_PERMIT FILE - M2010071 (3)

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from Google Earth was coordinated with the model coordinates and the model plan view boundaries were set to 6,000 feet by 6,000 feet. The topographic mapping of the reservoir, topographic mapping by the U.S. Geologic Survey and known ground surface elevations at several locations away from the reservoir complex were used to develop ground surface elevations for the model. After developing the surface topography, ground surface elevations were summarized in a spreadsheet and imported into the model. The bedrock surface elevations were generated from the data in the geotechnical report in Appendix B to generate the bedrock surface imported into the model. Two layers were used for the model. Layer No. 1 was the soils over the bedrock and Layer No. 2 the bedrock. The soils over the bedrock in the vicinity of the reservoir complex were man-placed fills, the wind blown clays, silts and fine sands and the alluvium. The bedrock was claystone. The ground water was in the alluvium over the bedrock. CTL T elected to use a two layer model because it was judged . better to assign average engineering properties to the alluvium because its natural variability was infinite and the permeability of the claystone was many magnitudes less than the alluvium. The field and laboratory studies done for the geotechnical report in Appendix B included measuring engineering properties of the alluvium and the bedrock. After reviewing these studies CTL T assigned a hydraulic conductivity to each of the two layers. Layer No. 1 was assigned a hydraulic conductivity of 1 x 10-4 cm/s (0.28 ft/day) and Layer No. 2 was assigned a hydraulic conductivity of 1 x 10-6 cm/s (0.0028 ft/day). Generally, these hydraulic conductivities were consistent with field and laboratory measured values as well as values for similar subsurface conditions and soil/bedrock types. Boundary Conditions Every groundwater flow model requires an appropriate set of boundary conditions to represent the exchange of flow between the model and the external • system. The "Boundaries" menu item in Visual MODFLOW is divided into two McLAUGHLIN WATER ENGINEERS, LTD. 8 GOOSE HAVEN RESERVOIR COMPLEX EXPANSION CTL I T PROJECT NO. FC04797.002-145