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<br />-. .!-rF,~~', <br />~ <br /> <br />"ii <br /> <br />c <br /> <br />A. Location <br />The proposed reservoir site is located approximately 3 miles northeast of the Town of Sedgwick, <br />Colorado, Figure 1 represents the proposed site, which includes portions of Section 3 and Section <br />10, Township 11 North, Range 46 West, in the County of Sedgwick, State of Colorado. The site is <br />bounded to the north by the Peterson Ditch, to the east by Sedgwick County Road 21, to the south by <br />U.S. Highway 138 and the Sedgwick Bar State Wildlife Area, and to the west by Sedgwick County <br />Road 59, The site consists of approximately 425 acres, which is presently pasture land and irrigated <br />cropland. <br /> <br />e <br /> <br />The site is approximately 15 miles upstream of the Julesburg Gage which is the designated <br />measuring point for compact deliveries, The pro];lOsed site location was chosen based on proximity <br />to the gage, There is similar land adjacent to this site which could potentially be used for an <br />expanded project. This site offers the main advllIltage of direct proximity to both the Peterson Ditch. <br />and the GASP wells located adjacent to the South Platte River, <br /> <br />B. Project Scope . . <br />The feasibility study was to identify and address known environmental, constructional, or operational <br />constraints that would affect the completion of the proposed reservoir, The constraints that were <br />evaluated included review of the geotechnical information of the on-site materials and their <br />engineering properties as related for dam construction, Geologic information for the underlying <br />formations was compared to existing USGS data, Groundwater information including depth and <br />formation transmissivity was calculated from field tests and compared to existing USGS information. <br />Preliminary survey data was collected for the reservoir site, the Peterson Ditch and the GASP wells, <br />A records review was done for the GASP wells and phone interviews were completed with Canfield <br />Drilling of Fort Morgan, Colorado on current conditions of these wells and their capabilities for _ <br />being used in this project. The U,S. Army Corps of Engineers was contacted on 404 permit . <br />questions, A field meeting was held with the Corps to determine the requirements for a permit. A <br />preliminary opinion of probable cost was compiled using construction costs of known projects of <br />similar scope, lIIld conducting interviews with COntractors experienced in this type of project, <br /> <br />Two alternate types of reservoirs were studied at the feasibility level. The two reservoir alternatives <br />that were studied were (1) a conventional reserv()ir, with releases controlled by an outlet structure, <br />and (2) a recharge reservoir, in which releases aCcrue to the stream system through enhanced <br />grouudwaterrecharge. The reservoir alternatives were studied in regards to diversions into the <br />reservoir, deliveries back to the river, size and layout of the reservoir, and the effectiveness of <br />increasing flows in the South Platte River during target periods, Historically the flows in the river <br />during the period April 1- October 15 have dropped below the benchmark flow of 120 cfs. A flow <br />rate below 120 cfs at the state line is not necessarily a compact violation, but the potential for <br />interruptions in water diversions needs to be minimized to give more certainty for water users, <br /> <br />An off-channel reservoir is one that does not dam a flowing stream. This study site has no <br />discernible drainage basin due to the flat nature of the area, There are three irrigation canals that lie <br />upstream from the property that intercept drainage. Due to the lack of grade change across the site a <br />ring dike will be required to form the reservoir, A ring dike simply means that a dam will be <br />constructed around the entire perimeter because of the lack of topographic relief, Plate I is a <br />preliminary plan layout of the reservoir based on the assumptions outlined in this report. <br /> <br />The dam geometry would use a 6h: 1 v slope on the upstream side and a 3h: 1 v slope on the _ <br />downstream side, The sffallow upstream slope Was chosen in lieu of a steeper slope with imported.. <br />riprap protection, The shallow slope will help dissipate wave energy and reduce shoreline erosion, I <br /> <br />2 <br />