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SPDSS Phase 3 Task 44.2 Denver Basin Region <br />Water Level Technical Memorandum <br />FINAL <br />To: Ray Alvarado, CWCB <br />From: Camp Dresser and McKee, Inc. <br />Mark McCluskey, Jessica Poceta, Nathan Smith, and Gordon McCurry <br />Subject: SPDSS Groundwater Component Phase 3, Final Task 44.2 <br />Denver Basin Bedrock Water Level Technical Memorandum <br />Date: November 28, 2006 <br />Introduction <br />The groundwater component of the South Platte Decision Support System (SPDSS) includes <br />compiling and evaluating available relevant data to support the Decision Support System (DSS) <br />for the South Platte River watershed and to add the data to HydroBase, the State of Colorado's <br />hydrological database. The SPDSS groundwater study area is presented in Figure 1. For the <br />purposes of the SPDSS, the groundwater study area is divided into two hydrologic regions. The <br />Denver Basin Region includes the bedrock aquifers of the Denver Basin. The South Platte <br />Alluvium Region consists of the unconsolidated deposits of the South Platte River mainstem, <br />extending downstream from just below Chatfield Reservoir to the Nebraska state line at <br />Julesburg, and consists of the unconsolidated deposits of the tributaries to the South Platte <br />River. The South Platte Alluvium Region also includes the alluvium overlying the Denver Basin <br />bedrock aquifers in Water Divisions 1 and 2. <br />The current definition of the Denver Basin aquifers was established in 1985 with promulgation <br />of the Denver Basin Rules, 2 CCR 402-6 (Division of Water Resources [DWR] 1985). The four <br />principal bedrock aquifers of the Denver Basin are, from top to bottom, the Dawson, Denver, <br />Arapahoe, and Laramie-Fox Hills Aquifers. The Dawson and Arapahoe Aquifers have been <br />subdivided by the Colorado DWR into Upper and Lower units based on the presence of lower <br />permeability claystone and shale layers in their respective northern extents (Figure 2). <br />Of note is an area in the northwest corner of the Denver Basin region referred to by the DWR as <br />the Complex Area. This is a portion of the Denver Basin with extensive faulting and vertical <br />displacement in which geologic and water level data should be viewed with some caution due <br />to the geologic complexity. Contours for the Laramie-Fox Hills and Arapahoe Aquifer are not <br />shown for this area. Information on the characteristics of the Laramie-Fox Hills Aquifer in this <br />Complex Area can be found in a report by Kittleson (2004). <br />This work was undertaken for the Colorado Water Conservation Board (CWCB) and the <br />Colorado DWR, under Tasks 38, 39 and 44 of Phases 1, 2 and 3 of the SPDSS by Camp Dresser & <br />McKee (CDM). Tasks 38 and 44 of the SPDSS include the collection, analysis, and mapping of <br />SPDSS Phase 3 Task 44.2 TM -Final <br />11/28/2006 <br />