South Platte River Basin: Chatfield Reservoir Reallocation Project comment period now open

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Here’s the release from the U.S. Army Corps of Engineers:

The Corps of Engineers, Omaha District (Corps) is pleased to announce the release of the Draft Chatfield Reservoir Storage Reallocation Feasibility Report /Environmental Impact Statement (FR/EIS) on June 8, 2012.

The U.S. Army Corps of Engineers proposes to reallocate 20,600 acre-feet of storage from the exclusive flood control pool to the conservation pool at Chatfield Reservoir. Chatfield Reservoir is well placed to help meet this objective for the following reasons: the reservoir provides a relatively immediate opportunity to increase water supply storage without the development of significant amounts of new infrastructure; it lies directly on the South Platte River (efficient capture of runoff); and it provides an opportunity to gain additional use of an existing federal resource.

The FR/EIS has been prepared by the Corps under the authority of Section 808 of the Water Resources Development act of 1986, in sponsorship with the Colorado Water Conservation Board (CWCB). The study provides a comprehensive evaluation and comparison of water supply alternatives and their associated impacts and benefits. Based on the analysis presented in the FR/EIS, the Corps recommends reallocating 20,600 acre-feet of storage from the exclusive flood control pool to the conservation pool at Chatfield Reservoir for purposes of M&I water supply. Implementation of the tentatively recommended plan would reallocate storage from the flood control pool to the conservation pool, effectively raising the top of the conservation pool by 12 feet. This reallocation of storage would help meet part of the growing demand for water in the Denver Metro by using existing federal infrastructure, and lessen the dependence on non-tributary ground water.

The tentatively recommended plan meets all federal National Economic Development goals by providing average year yield of 8,539 acre-feet at less cost than other alternatives for water supply. The plan also balances environmental and recreational needs by requiring mitigation to offset impacts to terrestrial based effects (wetland and riparian habitats, including Preble’s jumping mouse critical habitat), and modification of recreational facilities affected by increasing the top of the conservation pool. The reallocation of flood storage to water supply storage would primarily result in greater and more frequent reservoir pool fluctuations at Chatfield Reservoir, but the impact on downstream flood frequency is negligible.

The FR/EIS is available online at http://www.nwo.usace.army.mil/html/pd-p/Plan_Formulation/GI/GI_Chatfield.html.

From The Denver Post (Bruce Finley):

A massive draft environmental impact statement sets out the engineers’ proposals for mitigating impact and opens a public comment period…

The proposed mitigation is designed to compensate for the loss of a cottonwood-studded shoreline and stretches of free-flowing river within Chatfield State Park. Other work would offset lost habitat for the Preble’s meadow jumping mouse, a federally-protected endangered species, and replace park facilities, including a boating marina. The U.S. Army Corps of Engineers project would flood about 587 acres of 5,400-acre Chatfield State Park, with water levels rising by up to 12 feet. More than 1.6 million people visit the park each year, spending about $9.5 million.

Metro Denver communities dependent on water from underground aquifers and agricultural producers favor the re-allocation of the reservoir storage – a way to meet growing demands for water while using existing federal infrastructure. Gov. John Hickenlooper and state water-supply planners have supported this $100 million Chatfield Reservoir Reallocation Project. Some conservationists are also supportive because it may be less harmful than other possible water supply projects…

The federal engineers’ tentatively recommended plan would provide an average annual yield of 8,539 acre-feet of water at less cost than other alternatives for water supply.

More Chatfield Reservoir coverage here and here.

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