Aspen officials approve feasibility study for Woody Creek reservoir
The city of Aspen is eying the gravel pit in Woody Creek to be a potential reservoir to store water in anticipation of future drought conditions in a world of climate change.
Aspen City Council on Tuesday approved a feasibility analysis contract with Deere & Ault Consultants, Inc. for nearly $150,000 to determine whether the gravel pit would work geologically as a reservoir.
The city purchased 63 acres surrounding the gravel pit in 2018 for almost $2.7 million with the idea that it would build one or more reservoirs on that property.
“One of the storage options is that when the gravel pit stops operating the city would use it, but it’s not clear whether that’s feasible,” said Raquel Flinker, the city’s interim utilities portfolio manager.
The Vagneur gravel pit is owned and operated by Elam Construction. The city does not have a formal agreement with Elam Construction, or its parent company, Kilgore Companies, to someday use the Woody Creek gravel pit as a reservoir, but a company official expressed support for the concept in 2017, according to the nonprofit news source Aspen Journalism.
An engineering study conducted for the city by Deere & Ault in the fall of 2017 found that a range of reservoirs could be built on the Woody Creek parcel and the adjacent gravel pit site, according to Aspen Journalism.
In one scenario, up to 8,000 acre-feet of water could be stored in a reservoir located on both the city’s new property and the gravel pit at a cost of $81 million. The city parcel sits on a deep layer of gravel, which would require excavation to store water, according to Aspen Journalism.
Another possibility is that Elam Construction would use the city’s land for excavation and the municipal government would use the deep gravel pit for its reservoir, said Tyler Christoff, the city’s director of utilities.
The city also is looking into storing water underneath government-owned property in what’s called an “in-situ reservoir” in which water fills the void in between sand and sediment.
Flinker and Christoff said the city is embarking on an integrated water resource plan that will explore all options for storage and land.
“We want to have a parallel path going forward,” Christoff said. “We are trying to explore the whole gamut of options.”
Currently, the city has less than a day of storage during peak summer use at its Leonard Thomas Reservoir, which has a capacity of 9 acre-feet, according to Flinker.
Today, the city’s primary source of stored water is snowpack, which varies significantly from year to year.
Aspen uses direct flow rights from Maroon and Castle creeks, which are diverted to the Leonard Thomas Reservoir located at the city’s water treatment facility, treated, and then delivered to Aspen customers, according to Flinker.
After public outcry and legal wrangling surrounding Aspen’s attempt to keep its rights to build dams on Castle and Maroon creeks, the city in 2017 announced its intention to transfer its conditional water storage rights to Woody Creek and other potential sites around the valley.
The city’s search for alternative water storage locations outside of the Maroon and Castle Creek valleys intensified after it filed two “diligence” applications in Div. 5 Water Court in October 2016 to maintain its storage rights, according to Aspen Journalism.
The applications were met with opposition from four property owners, four environmental groups, Pitkin County and the U.S. Forest Service.
The city’s conditional storage rights, which were filed on in 1965, were predicated on the city someday storing 4,567 acre-feet of water behind a 155-foot-tall dam on upper Maroon Creek and storing 9,062 acre-feet of water behind a 170-foot-tall dam on upper Castle Creek, according to Aspen Journalism.
Whether the city needs that much water storage, or even the 8,000 acre-feet in Woody Creek, is not yet known.
The integrated water resource plan, which will look at Aspen’s storage needs 50 years out, is aimed at answering that question, Flinker said.
There are other potential sites that the city is considering for reservoirs, whether above or below ground, including North Star Nature Preserve, Moore Open Space, Aspen Golf Course, Zoline Open Space and Cozy Point Ranch.
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