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This is a digital document from the collections of the Wyoming Water Resources Data System (WRDS) Library. For additional information about this document and the document conversion process, please contact WRDS at [email protected] and include the phrase “Digital Documents” in your subject heading. To view other documents please visit the WRDS Library online at: http://library.wrds.uwyo.edu Mailing Address: Water Resources Data System University of Wyoming, Dept 3943 1000 E University Avenue Laramie, WY 82071 Physical Address: Wyoming Hall, Room 249 University of Wyoming Laramie, WY 82071 Phone: (307) 766-6651 Fax: (307) 766-3785 Funding for WRDS and the creation of this electronic document was provided by the Wyoming Water Development Commission (http://wwdc.state.wy.us) 51.1248 (Com Creek Irrigation Dist.) FINAL Ef\JVJ RON MENTAL .fJA \.,1v"·~ ..~"'SMEJT\ ..J r V IT " CORN CREEK IRRIGATION PROJECT FINAL ENVIRONMENTAL ASSESSMENT CORN CREEK IRRIGATION PROJECT Prepared by CH2M HILL Denver, Colorado for Corn Creek Irrigation District November 1985 CONTENTS I Purpose and Need for Action I-I Introduction I-I Purpose and Need 1-3 II Alternatives II-I Water Diversion Alternatives II-I Storage Reservoir Alternatives 1I-3 Project Alternatives 1I-6 III Affected Environment III-I Physical Components III-I Biological Components III-7 Socioeconomic Components III-IS IV Environmental Consequences IV-l Teeters Reservoir with Diversion Weir IV-I Teeters Reservoir with Infiltration Gallery IV-29 No-Action Alternative IV-30 v Consultation and Coordination V-I Literature Cited Appendix A. Bird and Mammal Species Lists Appendix B. Hydrology Data Appendix C. Agency Comments on the Draft Environmental Assessment DE/30R/133 ii TABLES 1 Laramie River Flows Upstream of the Confluence with the North Platte River, During 3 Years Selected to Represent Average, Wet, and Dry Years in the Laramie River Basin 1II-3 2 Laramie River Discharge (cfs) and Water Quality Data Upstream of the Confluence with the North Platte River 1II-4 3 Glendo Reservoir Storage Data 1I1-5 4 Guernsey Reservoir Storage Data 1II-6 5 Monthly North Platte River Flows at Whalen Diversion Dam During 3 Years Selected to Represent Average, Wet, and Dry Years in the North Platte River Basin 1II-8 6 North Platte River Water Quality Between Glendo Reservoir and the Wyoming-Nebraska State Line 1II-9 7 North Platte River Discharges Between Glendo Reservoir and the Wyoming-Nebraska State Line III-I0 8 Summary of Water Releases from Storage Reservoirs, Water Withdrawals by CCID, and Resultant Flow Changes Downstream of the CCID IV-5 9 Laramie River and North Platte River Flows During the 37-Year Period 1941 through 1977 IV-6 10 North Platte River Flows with and without the Corn Creek.Project at Selected Sites (with 11,250 ac-ft Replacement Water at Fort Laramie) IV-7 11 North Platte River Flows with and without the Corn Creek Project at Selected Sites (with 11,250 ac-ft Replacement Water at Fort Laramie) IV-9 12 Monthly North Platte River Flows and Expected Depletions at Fort Laramie Due to the Corn Creek Project during Average, Wet, and Dry Years (1,000 ac-ft) IV-13 iii TABLES (continued) 13 Monthly North Platte River Flows and Expected Depletions at the Wyoming-Nebraska State Line due to the Corn Creek Project during Average, Wet, and Dry Years (1,000 ac-ft) IV-14 DE/30R/133 iv FIGURES 1 Location Map I-2 2 Diversion Dam Alternate II-2 3 Infiltration Gallery Alternate II-4 4 Corn Creek Irrigation Project- Teeters Alternate 1I-5 5 Corn Creek Irrigation Project- Glomill Alternate II-7 DE/30R/I33 v Purpose and Need for Action I. PURPOSE AND NEED FOR ACTION A. INTRODUCTION The Corn Creek Irrigation District (CCID) is situated in Goshen County, Wyoming, approximately 20 miles southwest of the City of Torrington (Figure 1). The District extends south of the confluence of the Laramie and North Platte Rivers and includes a corridor through the physiographic area known as Harmony Heights, with the remainder in the Goshen Hole region. The general area drains to the southeast and ranges in elevation from 5400 feet at the upper end to 4200 feet at the southeast boundary. The Corn Creek Reservoir Association was formed in 1966 and was later reorganized as the Corn Creek Irrigation District, according to the laws of the State of Wyoming. The District has the power of eminent domain and the authority to levy such taxes as necessary to repay any loans and operating costs. The District boundaries encompass approximately 70,000 acres. The land use within the District is approximately 40 percent dry cropland and 60 percent rangeland. The District has defined over 15,000 acres of privately owned land within their boundaries that would receive irrigation water from the proposed project. On July 24, 1974, the Corn Creek Reservoir Association and Basin Electric Power Cooperative on behalf of the Missouri Basin Power Project (MBPP) entered into a contract which guarantees the delivery of 22,500 acre-feet (ac-ft) annually to Corn Creek. The contract is for a firm annual supply of water, and there are no allowances for a reduction in supply during drought periods. Although the water is generally assumed to be sup plied from storage in Grayrocks Reservoir, the contract only requires that MBPP allow sufficient water to pass through Grayrocks and down the Laramie River to make the primary water rights for 22,500 ac-ft available to the Corn Creek Irrigation District (15,000 ac-ft between April 1 and Sep tember 30 and 7,500 ac-ft between October 1 and March 31). In addition to the firm supply from Grayrocks Reservoir, there are two other proposed water supplies for the project. The second supply is the supplemental water right for 10,100 ac-ft/year from the Bureau of Reclamation's (USBR) Glendo Reservoir. The Glendo Reservoir supply is available in all years except during an extended drought lasting over 3 years (CH2M HILL, 1983). This supply will have to be con tracted from the USBR, and negotiations are currently I-I 'Tq GUERNSEY WYOMING '\ PROJECT LOCATION-+- !'.' 1 i )"{ll I~ it \., j ! I I 'I I .1 '\: H I N I;. " .. j . i,,,\.-,./.) (J~~( 'i, 'j;, fC I~. ~ i ~ 1~(1 1:,"';: . 'i .. , i ; I 'i "'i I; i I TO C fEYENNE CH2M FIGURE 1 IIHllL LOCATION MAP underway. The third supply is the possibility of a direct flow diversion from the Laramie River. However, use of this right would be subordinate to all senior rights and is not expected to produce a viable firm yield on an annual basis. A filing has been submitted to the State Engineer for this right and would be of use only under extreme hydraulic con ditions. The proposed project consists of a surface water diversion system, a pump station on District-owned land at the conflu ence of the Laramie and North Platte Rivers capable of pump ing 75 cubic feet per second (cfs), a reservoir to store winter diversions and to provide pressure head, a main pipe line to deliver water to the project area, and distribution laterals to provide water to each land parcel. CH2M HILL was retained by the Wyoming Water Development Com mission (WWDC) in November 1982 to perform an investigation which would develop and evaluate the economic feasibility of a conceptual plan that would allow for the delivery of water to approximately 15,000 acres in the CCID. Within the scope of these services, an evaluation of the irrigation potential of the soils was conducted and preliminary design criteria were developed. Various alternative configurations and de signs were evaluated and it was determined that the project is feasible from an engineering standpoint (CH2M HILL, 1983). When both direct and indirect benefits are considered, the project also is economically feasible with a benefit/cost ratio of 1.84. A 50-year evaluation period was selected to calculate the benefit/cost ratio, and costs were discounted using the 7-7/8 federal discount rate. B. PURPOSE AND NEED The area economy is primarily agricultural. For example, 85 percent of the business trade in the Torrington area is based on agriculture. Mean annual precipitation for the region is about 14 inches, but ranges from less than 8 to more than 22 inches. Spring rains are usually sufficient to start crop growth, but normally the precipitation during August and September is very low. Without irrigation water some dry land wheat cropping is practical, but most of the area is limited to use as rangeland. The growth of the area's economy, therefore, is limited as ~ong as agriculture is primarily dryland crops and rangeland, with the resultant fluctuating crop yields. Existing irrigation developments in neighboring areas have demonstrated that favorable crop production is possible when a full and assured water supply is available. Goshen County currently has about 150,000 acres of land under irrigation, and the CCID development would add another 10 percent to that total. Development of irrigation service to new lands I-3 in the area by CCID would not only help stabilize and improve agricultural production, but it would enhance the tax base and the economic growth potential of the area. Conversion of rangeland to Class 2 irrigated land increases the tax valuation of the property significantly. The January 1953 stipulation to the original (1945) North Platte Decree issued by the u.s. Supreme Court mandated that 15,000 ac-ft of Glendo Reservoir water be allocated annually for irrigation in southeastern Wyoming, specifically within the area between Guernsey Reservoir and the Wyoming-Nebraska state line.