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Final Report (Contract for Services No RV052301/F) to Wyoming Water Development Commission for the Alpine Spring Irrigation Supply Project
Oct 1, 2001
INTRODUCTION Background The Alpine Water and Sewer District was formed in the early 1970’s and thereafter in 1974 the Mill Creek Springs system was installed to serve as a water source for the town. In the summer of 1998, the water supply was contaminated with E. coli. The EPA required the town to remove the spring from the distribution system unless the spring water was treated. Costs to treat the spring water were determined to be excessive and the town removed the spring from its water distribution system. The town is now looking for ways to put this water to beneficial use by irrigating its 55 acres of parks and other green areas. Use of the spring water would reduce the demand on the town’s current potable water supply and distribution system. The spring collection system is located at the confluence of two drainages near Little Jenny Lake approximately 1 ½ miles southeast of Alpine. (See Topographic map, Appendix D) There are a total of 24 springs, seven of which provide the majority of the water, in the Little Jenny Lake area that are developed through a series of perforated 6-10 inch PVC pipes and spring boxes. The pipes and boxes are buried approximately 5 feet deep and are set in such a manor as to facilitate drainage of the area and to divert the water into a 50,000 gallon concrete tank. The 8-inch PVC transmission line runs from the tank to a fire hydrant located on the Southeast end of the town of Alpine. Elevation drop from the spring area to the fire hydrant is 229 feet, providing a static pressure at the hydrant of 99.1 psi. This point will be the beginning of the irrigation distribution system. Water flows from the spring vary during the course of the year. Water rights information indicates that 1.17 cfs was the measured tank inflow. Flows are at their lowest during September and February. During the summer of 2000, which was a drought year in the area, there were reported flows of 18,000 gallons/day in late August and September. During dry periods there will be a need for supplemental water to adequately irrigate the 55 acres of parks and greenways. Soils in the area are classified as Hobacker gravelly loam. The soil is alluvium material created as a result of the three nearby rivers. The Hobacker gravelly loam is typically a highly drained soil that will require a short duration and short interval irrigation design. Sprinkler irrigation applications are well suited for these types of soils. Project Objectives The Rio Verde Engineering (RVE) team focused on those project items that were defined during the scoping meetings on June 20 and on July 12, 2001. Scoping Meeting Results Rehabilitate Little Jenny Lake to provide wildlife/stock water Use Potable Water System to supplement Raw Water Irrigation Supply from the Spring Area. Look at Fire Flow capabilities from the Spring Area Look at irrigation water supply line to 55 acres of existing and proposed parks and green areas. The spring area, potential pipeline routes within the town limits, and potential areas of irrigation were surveyed using GPS equipment. Plans were developed for the Little Jenny Lake Spring Area to rehabilitate the existing dike in order to improve the efficiency of the tank and springs and to provide water for wildlife. Irrigation requirements were determined based on local soil types and the areas to be irrigated. WATERCAD Water Distribution Modeling Software by Haested Methods was used to model many different physical scenarios of water distribution systems. Three of those scenarios were chosen as viable alternatives and these alternatives along with cost estimates using three types of pipe material were presented to the Town of Alpine. The alternative selected was a system that would provide Fire Flow down the main line of the system. The Fire Flow alternative involved a 10-inch HDPE main line with 8 and 4-inch secondary lines. Preliminary designs and cost estimates were completed using this alternative. Permit requirements and the USFS Lease/Use Agreement were evaluated and assessed. An economic analysis was performed based on the design costs, potential funding sources and grant loan scenarios. Environmental report consists of responses from letters and maps sent to different agencies. Final project reports are due on November 1, 2001. Key project personnel will assist the WWDC in holding an informative public hearing in the Town of Alpine to present the results of the study.
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