Environmental Assessment for the Tamarack Groundwater Recharge Project

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groundwater recharge projects to provide dependable water supplies that will benefit many fish and wildlife species including federally listed threatened and endangered species along the Platte River Basin in Colorado and Nebraska. This proposal involves the construction of up to 35 wells, approximately 13 miles of pipeline and up to 41 small ponds located in natural depressions (see Figures 2 and 3). The wells will pump up to 30,000 acre - feet of water into the ponds annually. A portion of this water will return back to the South Platte River during times of shortage to provide flows to benefit native fish species in Colorado, and incidentally providing flows for T &E species in central Nebraska, as agreed to by the State of Colorado in Tab 3A of the Cooperative Agreement. The depositing of up to 30,000 acre -feet of water annually in the 41 designated upland sites on the TRSWA and PESWA will create a significant amount of new wetland habitats. Alluvial flows back to the river are also projected to create or enhance similar wetland type habitats below the pumping sites. A small artificial stream approximately one -third of a mile long will also be constructed along with a series of small ponds that will be used as an emergency water supply for the artificial stream and for maintaining proper water temperatures for the native fish. 2) NO ACTION ALTERNATIVE If the project is not constructed, none of the above described features will be built. Further, none of the benefits to Colorado T &E species, Federally listed T &E species, or other wildlife benefits will be realized. The State of Colorado will be limited in its ability to fulfill its commitments under Tab 3A of the Cooperative Agreement. IV. AFFECTED ENVIRONMENT SOILS The proposed pond sites and majority of pipelines on the TRSWA will be located in deep, excessively drained soils on upland sandhills. These sand deposits parallel the river to the south and have slopes that are gently rolling to strongly rolling. Permeability of these soils is very rapid. Effective rooting depth is 60 inches or more. The available water capacity is low. Surface runoff is slow, the soil blowing hazard is high, and the erosion hazard is slight. Valent loamy sands and Dailey loamy sands are the prominent soil types. Soils near the proposed wells are mostly deep, somewhat poorly drained soils on low terraces and bottom lands. Permeability is slow. Effective rooting depth is 60 inches or more. Available water capacity is moderate. Surface runoff is slow, and erosion hazard is slight. A fluctuating water table occurs between 12 and 24 inches during winter and spring months. A moderate saline condition is common. Soil types here include, Westplain silty clay loam, Westplain- Alda complex, Manter loamy sand, and Fluvaquentic Haplaquol.