Chatfield Storage Reallocation Project update

Proposed reallocation pool — Graphic/USACE

From The Castle Rock News-Press (Alex DeWind):

The $130 million project, called the Chatfield Storage Reallocation Project, approved in 2014will allow water storage for eight municipal water providers and agricultural organizations across the Denver metro area and northeast Colorado. Construction is expected to begin late this year and will take up to two years to complete.

“The ability to store in that much space gives Highlands Ranch new surface water supplies,” said Rick McCloud, water resources manager of Centennial Water and Sanitation District in Highlands Ranch, one of eight participants. “We can use that water instead of non-tributary (non-renewable) groundwater.”

Chatfield Reservoir Mitigation Co., formed in 2015 to implement the project, hosted a May 30 open house at ThunderRidge High School in Highlands Ranch for the public to learn about upcoming changes at Chatfield Reservoir and the surrounding state park, which is a major recreational draw for Front Range residents.

The following are five things to know about the reallocation project.

History

In 1975, the U.S. Army Corps of Engineers built Chatfield Reservoir at the confluence of the South Platte River and Plum Creek to control flooding following the disastrous 1965 flood.

The main purpose of the reservoir, which currently has the ability to store more than 350,000 acre-feet of water, is flood control, but it also provides space for multiuse water and maintains fisheries and wildlife habitat.

In response to a growing demand for water — the Statewide Water Supply Initiative, commissioned by the state Legislature, estimates by 2030 Front Range water demand will exceed supply by 22 percent — the corps determined Chatfield Reservoir could accommodate additional storage space.

“We are taking advantage of an existing federal structure,” said Colleen Horihan, the corps’ project manager.

Who will benefit

The project is a partnership among eight water providers and environmental organizations: Colorado Water Conservation Board, Centennial Water and Sanitation District, Central Colorado Water Conservancy District, Castle Pines North Metro District, Colorado Parks and Wildlife, Castle Rock, Center of Colorado Water Conservancy District and Castle Pines Metro District.

Participants will fund upward of $130 million over the next two years for construction of the project. Each provider will receive a varying amount of the additional 20,600 acre-feet of storage space for surface water in Chatfield Reservoir once the reallocation is complete.

The project allows participants to have access to renewable water supplies at an existing water storage reservoir, according to Chatfield Reservoir Mitigation Co. It also provides renewable water supplies for paying customers in several communities, such as Highlands Ranch, Castle Pines and Castle Rock.

Recreational impact

In order to prepare for the reallocation project, many recreational facilities will be modified in phases starting this fall. Most modifications include moving and elevating public areas for increased flood protection and updating existing structures, including picnic structures and bathrooms. A list of detailed designs is available at chatfieldreallocation.org/recreation.

Chatfield Reservoir Mitigation Co. encourages park users to follow the project on Facebook and Twitter and to ask questions and receive updates on closures and construction schedules.

“Social media channels are critical platforms,” said Ben Waymire, social media consultant of the project. “These are channels for residents to engage.”

Environment

On-site and off-site environmental mitigation will be done at Chatfield State Park to address impacts of storing more water in the reservoir, according to Chatfield Reservoir Mitigation Co.

Mitigation will include an adaptive tree-management plan for the reservoir to remove dead trees and debris along the shoreline and to identify a long-term tree-monitoring program. A $424,000 budget is set aside for pre-construction weed control. Off-site mitigation is being explored for bird and Preble’s meadow jumping mouse habitats. Depleted water channels and wetlands will be restored using vegetation and structures.

“We are creating more wetland habitat than we are impacting with the project,” said Barbara Biggs, project manager.

Timeline

The reallocation project will begin in fall of this year and is expected to be complete by 2020, after which the reservoir will be able to store up to 20,600 acre feet of additional water.

Construction will be done in 12 phases, starting with the north boat ramp of the reservoir, to minimize impact on Chatfield State Park — the most visited state park in Colorado with more than 1.6 million visitors per year, according to the mitigation company. The final phase will be wetland and bird habitat mitigation of Mary Gulch, an eastern tributary of the South Platte River.

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