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The following maps were generated (Note: because of the large size and draft nature of the maps, they <br />are not presented in this memo but are kept in DOW'S project file): <br />Well Location Map: This map highlights the wells that discharge more than 50 gpm. This map can be <br />used to estimate where constant head boundaries or ground water streamlines may be located. This <br />information is needed in determining model boundary locations. In addition, this map can be used to <br />identify possible calibration wells in the study area. <br />Aquifer Base Elevation Map: This map shows the elevation of the base of the aquifer. Only data from <br />wells that were known to penetrate the aquitard (clay, brule, or shale) were used in preparing this map. <br />Preliminary contours were generated by hand. The aquifer base surface is highly variable but generally <br />dips to the southeast with a deep valley feature noted just north of the highway. This topographic valley <br />probably indicates an old river channel. <br />A comparison of the topography of the aquifer base was made to the USGS map 4 . The Tamarack Model <br />GIS adds over 50 data points to the data used to generate the USGS map. The new data points do not <br />radically change the character of the aquifer base but provide additional detail. The USGS map is based <br />on less data and therefore is more uniform. <br />The data fields identifying the Ground Elevation and the Base of Aquifer can be saved in a separate file. <br />Contour surfaces can be generated using other software such as SURFER and imported into VISUAL <br />MODFLOW. This data can then be used by VISUAL MODFLOW to generate Layer 2 thickness and <br />model grid information <br />• <br />Layer 2 Elevation Map: This ma provides the data for the elevation for the to of Layer 2. . <br />Y P pp p Y <br />Preliminary contours were generated by hand. These contours indicate that Layer 1 topographic surface <br />is more variable and dips slightly to the southeast. As described for the Aquifer Base, this data can be <br />used to generate Layer 1 thickness and model grid information. <br />• <br />Hun:, R.T, P.A. Schenieder and others, 1972, Hvdrogeologic Characteristics of the Valley -Fill Aquifer In the Julesburg <br />Reach of the South Platte River Valley, Colorado USGS Open -File Report 73 -125. <br />9 <br />