IVINS – The Ivins City Tuacahn Upper Detention Basin Project is completed. After more than 15 years of planning, analyses, environmental evaluations, design and finally for the past three months construction, the Tuacahn Detention Dam is now completed. The earthfill dam is 18 feet tall by 650 feet in length and provides 26 acre-feet of detention volume for a 677-acre drainage area.
The dam was constructed by Ivins City to reduce flooding in the Tuacahn Wash. In September of last year, the large flood that caused the failure of Laub Pond Dam in Santa Clara highlighted the need for the project. The city had been pursuing the planning, design and construction of the dam since 1998, as outlined in St. George News previous report on the project, but after finally overcoming several environmental and engineering obstacles, the project lacked some necessary funding. This recent flood increased the priority of funding the dam despite the City’s limited resources.
The dam is situated in the amazing scenery of the Tuacahn canyon within the boundaries of Snow Canyon State Park and in the midst of highly sensitive habitat for the threatened desert tortoise. In this context, the design of the dam incorporated several additional features. The dam has a meandering centerline to provide a more natural look. The rock armoring has been buried with a soil cover that will be revegetated with grasses and forbs to better conceal the appearance. The construction of the dam was confined to a small envelope to minimize disturbance of habitat. A large diameter (60-inch) outlet was installed to allow smaller floods to flow through with minimum inundation behind the structure while still providing the needed benefits during larger events.
An additional constraint on the project was that the construction had to be confined to the period of tortoise inactivity which is defined by the habitat administrators as a 10-week period between Dec. 1 and Feb. 15. The contractor, JP Excavating, worked diligently and was successful at completing the project in the necessary timeframe with two days to spare.
The project provides added flood protection to approximately 80 existing homes in Ivins City. That number could easily double in the future as the City develops. Santa Clara City will also have similar benefits in protecting existing and future homes and developments, especially while the Laub Pond Dam is not in place. With the Tuacahn Wash crossing Center Street, which is considered a major arterial, protecting this critical arterial from flooding benefits nearly all of the approximately 7,000 residents in Ivins. In addition, the Tuacahn Wash crosses Pioneer Parkway in Santa Clara, which is another major arterial street, and is expected to benefit an even greater population. Also, undeveloped properties in Ivins will become more viable. Some of these properties are considered prime commercial, which could provide Ivins with an economic boost.
Ivins City in a statement released yesterday gave special thanks to all the agencies involved in the project including Snow Canyon State Park, Red Cliffs Desert Reserve, Utah Division of Wildlife Resources, U.S. Fish and Wildlife Service, U.S. Army Corps of Engineers, Utah Division of Water Rights, State Engineer, Tuacahn Center of the Arts, design engineer Alpha Engineering, environmental consultant JBR, geotechnical consultant RBG Engineering, and Ivins City Public Works all of whom played a critical role in the completion of the project.
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