Energy policy — hydroelectric: Aspen’s new Castle Creek plant

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Here’s a letter to the editor — running in the Aspen Times — written by Phil Overeynder, Utilities and Environmental Initiatives Director, City of Aspen, explaining the benefits of the new hydroelectric plant approved in 2007 by Aspen voters, along with the City’s committment to instream flow in Castle Creek:

In the near future we plan to provide additional information about this important and environmentally responsible project. What Aspenites gained in approving this project on the 2007 ballot is the annual production of 5.5 million kilowatt-hours of environmentally responsible electricity. That power production will prevent more than 5,000 tons of carbon dioxide from entering the atmosphere every year. This represents more than 25 percent of the remaining carbon emissions resulting from power generation for Aspen’s electric utility.

The production of clean, renewable energy at the Castle Creek Hydroelectric Project will depend on the use of water drawn from Castle Creek. There is simply no way around this basic fact. However, the city is doing its best to limit the impact on Castle Creek. The only change the hydroelectric project will make in the city’s water use regime is that a portion of the water diverted by the city will return to the creek at a point approximately three-fourths of a mile downstream of the present point of return, which is below Thomas Reservoir. The new point of return will be at the Castle Creek Bridge.

From the beginning of the Castle Creek Hydroelectric Project, the city of Aspen has been aware of the critical importance of maintaining a viable, healthy stream in Castle Creek. The Colorado Water Conservation Board’s (CWCB) decreed instream flow right for Castle Creek is 12 cubic feet per second (cfs), and is decreed for the purpose of protecting the natural environment.

This is a fairly junior water right. To help assure that Castle Creek actually receives this instream flow, which applies to all of Castle Creek, the city has already voluntarily committed to operate its own, more senior, water rights in a way that will support the 12 cfs instream flow. The city currently honors this commitment, and the proposed Castle Creek Hydroelectric Project will not alter this commitment. This means it is possible that, under certain conditions, the flow in Castle Creek upstream of the hydroplant will be 12 cfs. Historical low stream flow conditions in Castle Creek (generally reaching the lowest values in late winter) have averaged in the range of 20 cfs. When the hydroplant is operating in times of low flow in Castle Creek, flows in the reach of the creek between the hydroplant intake and the plant may be reduced to 12 cfs instead (the value established by the CWCB as necessary to protect the natural environment).

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