Ongoing #SouthPlatte Basin water storage projects

From The Sterling Journal-Advocate:

There already are six projects being pursued in the South Platte Basin to extend the water supply. These are not included in the recent South Platte Storage Survey, but have been considered and under way for some time:

Northern Integrated Supply Project (NISP) map July 27, 2016 via Northern Water.

• The NISP/Glade project — The Northern Integrated Supply Project is a proposed water storage and distribution project that will supply 15 Northern Front Range water partners with 40,000 acre-feet of new, reliable water supplies.

Map from Northern Water via the Fort Collins Coloradan.

• Chimney Hollow Reservoir — A 360-foot high dam that will hold 90,000 acre feet to help supply the thirsty Thompson Valley urban area. The water will come from the Windy Gap Project, a diversion dam and pumping station completed in 1985 to provide extra irrigation and municipal water out of the Colorado River. The water originally was stored in Grand Lake, but when that is full, the water cannot be stored. Chimney Hollow, also known as the Windy Gap Firming Project, solves that problem.

Reservoirs NW of Fort Collins

• Halligan reservoir enlargements — Halligan Reservoir near Fort Collins is about 100 years old. Its capacity is about 6,400 acre feet of water and the City of Fort Collins wants to add 8,125 acre feet to the reservoir by raising its dam about 25 feet.

• Milton Seaman Reservoir enlargement — Greeley originally had wanted to expand Seaman Reservoir in conjunction with Halligan, but because of diverging goals Greeley withdrew from the joint project. The expansion of Seamon now is targeted for design in 2028 and construction by 2030.

Gross Dam enlargement concept graphic via Denver Water

• Gross Reservoir enlargement — Gross Reservoir is one of 11 reservoirs supplying water to the City of Denver and surrounding urban areas. It is on the city’s Moffat System, which diverts water from the Western Slope to the metro area. Denver Water has proposed raising the dam height by 131 feet, which will allow the capacity of the reservoir to increase by 77,000 acre feet.

Proposed reallocation pool — Graphic/USACE

• Chatfield Reallocation Plan — The U.S. Army Corps of Engineers has determined that Chatfield Reservoir, built primarily for flood control after the 1965 South Platte River flood, can accommodate an additional 20,600 acre feet of water storage for water supply without compromising its flood control function. This additional storage space will be used by municipal and agricultural water providers to help meet the diverse needs of the state. No actual construction is required, but the legal, environmental, and engineering concerns of allowing the reservoir to hold more water all have to be satisfied.

@audubonsociety files lawsuit over Chatfield Reallocation Project

Proposed reallocation pool — Graphic/USACE

From (Marc Stewart):

“Swim, or hike, or watch birds, if you have a boat you can go boating,” said Polly [Reetz].

Yet the couple fears a construction project to build additional areas to hold water will ruin the place in the near future.

It’s a project that supporters argue is necessary in order to store water in a state that is in the midst of a population boom and a drought.

“I think aesthetically, it’s going to be a very different kind of park with mud flats instead of this rich riparian vegetation,” said Gene.

Along with the Audubon Society, they fear that by getting rid of the green space around the reservoir, all of nature will be hurt… including the animals.

“When you destroy the habitat, or alter it, so that it’s no longer usable for them, there really isn’t any other place to go, because other areas are already full too,” said Polly.

Which is why the Audubon society has gone to court.

They want a judge to throw out a previous decision allowing the project to move forward, saying among other things, that it violates the Clean Water Act.

A hearing will take place in September.

The Army Corps of Engineers is not commenting as the case is in litigation

“Audubon recognizes the region is growing, and so were not against developing additional water supplies,” said Gene [Reetz]. He is pushing for more water conservation and alternative storage sites other than Chatfield.

Chatfield Reservoir: The best dam flood solution, period – News on TAP

The South Platte River flood of 1965 led to the construction of Littleton’s popular water recreation destination.

Source: Chatfield Reservoir: The best dam flood solution, period – News on TAP

Gilcrest: Chatfield Storage Reallocation Project open house, September 6, 2017

Proposed reallocation pool — Graphic/USACE

From The Greeley Tribune:

Representatives for the Chatfield Storage Reallocation Project will host an open house from 5:30-7:30 p.m. Sept. 6 in the cafeteria at Valley High School, 1001 Birch St. in Gilcrest.

Final designs for the recreational facilities changes and environmental mitigation projects for Chatfield Reservoir and the surrounding Chatfield State Park will be on display. Another display will show the agricultural benefits of the project, according to a release issued Saturday from the Chatfield Mitigation Co. The workings of the environmental pool to help time releases of the stored water also will be illustrated with a display.

The $134 million project will allow Chatfield to store up to 20,600-acre feet of additional water.

Representatives from consultant firms working on the designs, the U.S. Army Corps of Engineers, Colorado Water Conservation Board, Colorado Parks and Wildlife and the participating water districts all will be there to answer questions.

Update on chatfield storage reallocation project

Proposed reallocation pool — Graphic/USACE

From The Denver Post (Joe Rubino):

After more than a decade of discussion and planning, the Chatfield Storage Reallocation Project is set to begin later this year. The more than two-year construction effort will prepare the reservoir to accommodate an additional 20,600 acre feet of water to meet a variety of municipal, agricultural and industrial needs. Currently, the reservoir holds about 27,000 acre feet of water. Eventually it will hold up to another 20,600 acre feet of water and the the water level could rise as much as 12 vertical feet, officials said.

Beginning in winter and continuing through spring, the swim beach and north boat ramp will be reconstructed to accommodate the future shoreline. By the end of 2019, many other features of the park, including the marina, day use areas and South Platte bridge will be visited by construction crews and earth movers.

The park will remain open throughout construction. Higher water levels will change features along the reservoir’s shore…

The project will cost an estimated $160 million, said Tim Feehan, general manager of the Chatfield Reservoir Mitigation Co., whose eight partners — including Castle Rock, Centennial Water and Sanitation District and the Castle Pines Metropolitan District — will pay that tab in proportion to the amount of water storage each will be granted. Of that, $140 million has already been set aside in escrow.

Groundbreaking awaits final design approval from the Army Corps of Engineers, which built, owns and leases the reservoir to Colorado Parks and Wildlife for recreational use, Roush said. Preliminary designs and a tentative construction schedule are available online at, a project website created by Chatfield Reservoir Mitigation Co.

The swim beach is scheduled to close for reconstruction in late fall and reopen for use by Memorial Day weekend 2018. The beach and park perimeter road will be moved to the west, away from the present shoreline, to accommodate greater water fluctuations, effectively creating another 200 feet of beach area at low water. The parking lot will be expanded and the shower, restrooms and other features will be rebuilt. The north boat ramp also is scheduled to reopen to use by next Memorial Day weekend.

“A lot of the work is going to be done over the wintertime when the visitation is down and when the swim beach is closed and when the boat ramps are closed,” Roush said. “It’s about minimizing the time when the users would not be able to use those areas.”

@CFWEwater — Barr Milton Urban Waters Tour

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I rode along with the Barr Lake and Milton Reservoir Watershed Association and the Colorado Foundation for Water Education on their Urban Waters Tour of the South Platte River last Wednesday. These rides are educational and fun and well worth the time. It was great to meet some new folks from the water community. Thanks to Amy Conklin for organizing the ride.

We started at Johnson Habitat Park where the Greenway Foundation has located their SPREE outdoor school. We learned about efforts to increase the volume of water in the river through the Chatfield Reallocation Project which will provide environmental flows through the City of Denver. Joe Shoemaker, Jr. explained the genesis of the Greenway Foundation and how the area we were in was one of Denver’s dumps during his youth. The educational effort was in full swing with young students plying the waters for macro-invertebrates and other life.

A representative from Trout Unlimited conveyed his excitement about landing big carp from the river. He also told us that a fisherman recently pulled a 24 inch rainbow from the river just upstream from the park.

Further downstream at Weir Gulch the focus was on widening the channel to more a more natural flood plain to help manage stormwater and improve river and riparian health. The South Platte through here, back in the day, was a braided, meandering stream with a flood plain that was sometimes as wide as a mile.

A Denver Parks representative explained the big project at Confluence Park — the replacement of the original structures from the first project in the South Platte revitalization effort. Kudos to the contractor that stayed with the project as their profit dried up due to the discovery of coal tar on site. The Denver representative said that the company believed in the project and the benefits to the community.

The last stop was at the site of Globeville Landing Park. There was a lot of construction going on to build an outfall for stormwater management. Denver is building their Platte to Park Hill Project to mitigate flooding caused by construction and development over the years.

I highly recommend these tours. You’ll learn a lot, get a bike ride in, and meet some interesting folks. The South Platte River through Denver is a great ride. What a success story.

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.


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

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.”


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.


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.