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Q <br />Deliverables: <br />~`~ <br />• Minutes for each meeting documentation the USGS progress, handouts, and any concerns <br />identified by the Contractor. <br />Task 48: Pre-Development Alluvial Groundwater Modeling <br />Objective: <br />The objective of this task is to create apre-development groundwater flow model for the alluvial <br />aquiferfrom Chatfield Reservoir to the Stateline. Phase 3 activities will include development of <br />the conceptual model of flow using the data-centered approach, delineating the model extent, <br />layering and gridding, defining initial aquifer properties, boundary conditions and non-pumping <br />.fluxes, and simulating pre-pumping groundwater conditions. Future phases of SPDSS are <br />expected to include post development estimates of pumping, agricultural return flows, calibration <br />and potential alternatives simulations. The USGS groundwater flow model MODFLOW will be <br />used. <br />Discussion: <br />In Phase 3 a detailed, pre-development groundwater model for the alluvial groundwater system <br />from Chatfield to the Stateline will be developed. The model domains will include all major <br />tributaries that overlie the Denver Basin Region such as Plum Creek, Cherry Creek, Sand Creek, <br />Box Elder Creek, Bebee Draw, Kiowa Creek, Bijou Creek anal Lost Creek . Major drainages that <br />will not be modeled include those that drain from the western. foothills like Bear Creek, Clear <br />Creek, St. Vrain Creek, Big Thompson Creek and the Cache la Poudre River, smaller tributaries <br />such as Lone Tree Creek, Crow Creek, and Camp Creek. These will be incorporated into the <br />model as a flow boundary condition. In addition, the alluvial aquifer systems located in the <br />Upper Big Sandy and Upper Black Squirrel Designated Basins will not be included in the SPDSS <br />alluvial groundwater model. <br />Estimates ofpost-development diversions, pumping, surface water flows, deep percolation, etc. <br />are being developed by other SPDSS contractors outside this contract and are not expected to be <br />available in Phase 3. Even without these items significant progress in modeling the South Platte <br />alluvium can be obtained bypreparing apre-development ground water model. Conceptually, the <br />pre-development model will represent conditions in the alluvial aquifer before there. was <br />significant surface water or groundwater development. It is anticipated that this will represent <br />early 1900's conditions. This pre-development model is expected to be enhanced to include post <br />development activities in a later phase. <br />SPDSS Groundwater SOW, Phase 3 14 <br />