Project Overview

Current Status of Windy Gap Firming Project
Northern Water’s Municipal Subdistrict and the 12 Windy Gap Firming Project participants continue making progress as the project moves closer to design and construction.

After the Subdistrict submitted the WGFP's 401 water quality certification application to the Colorado Department of Public Health and Environment, the CDPHE conducted a public comment period, evaluated the application, and then issued the WGFP's 401 water quality certification in March 2016.
Section 401 of the federal Clean Water Act requires that the state provide the U.S. Army Corps of Engineers with a certification that the project will comply with applicable water quality standards. Staff forwarded the CDPHE's 401 water quality certification to the Corps, which is now considering issuing a Section 404 wetlands permit for the WGFP. Final design and construction of Chimney Hollow Reservoir can begin once the Corps has issued the 404 wetlands permit.

Design work is anticipated to take two years, and project construction another three to four years.

Windy Gap Firming Project Reaches Milestone
Video: Dec. 19 Record of Decision Signing Ceremony  

On December 19, 2014, following years of effort, the U.S. Bureau of Reclamation, Northern Water and its Municipal Subdistrict signed a new Windy Gap carriage contract. Simultaneously, Reclamation issued a Record of Decision for the Windy Gap Firming Project, enabling continued progress to design and construct Chimney Hollow Reservoir.

To view the Record of Decision, Final Environmental Impact Statement and other associated documents, please visit Reclamation's Windy Gap Firming Project EIS page.

News Releases:
 Chimney Hollow Reservoir Receives Final Approval
 Northern Water: Reservoir Project Moves Forward
 USBR: Reclamation Signs Record of Decision
The WGFP is a collaborative proposal between 11 Northeastern Colorado water providers and the Platte River Power Authority. The WGFP would improve the Windy Gap Project’s reliability by constructing a new storage reservoir for Windy Gap water at Chimney Hollow near Carter Lake.

Windy Gap Project Overview
The Windy Gap Project was first proposed in 1967 by the cities of Boulder, Estes Park, Fort Collins, Greeley, Longmont and Loveland. Built between 1981 and 1985 and located on the West Slope near Granby, Windy Gap consists of a diversion dam on the Colorado River, a pump plant and a 6-mile pipeline to Lake Granby, the largest storage reservoir in the Colorado-Big Thompson Project system.
During wet periods when Lake Granby is full, the Windy Gap Pump Plant cannot operate due to the absence of reservoir storage for Windy Gap Project water. If constructed as proposed, Chimney Hollow Reservoir would fill this new storage space need.
New Windy Gap Carriage Contract
Northern Water’s Municipal Subdistrict is coordinating the Windy Gap Firming Project on behalf of the project’s 12 participants. As part of the WGFP’s ongoing permit phase, the Subdistrict and Reclamation negotiated a new carriage contract to transport Windy Gap Project water through the C-BT Project facilities to Chimney Hollow Reservoir. The new contract was signed in December at Northern Water’s Berthoud headquarters. 


Grand County 1041 Permit
The firming project reached a major milestone when the Grand County Board of County Commissioners approved a 1041 permit and several related agreements in late 2012. 

The permit and agreements create a package that greatly exceeds the project's required mitigation by providing significant voluntary benefits, including improvements to the Colorado River, additional water supply for West Slope water providers, and long-term commitments to Grand Lake and the Colorado River.

How Water Is Reshaping the West – Nova Next/Rocky Mountain PBS, November 11, 2015

The site of the proposed Chimney Hollow Reservoir with
Carter Lake on the right. View the Chimney Hollow Reservoir map.

Project Answers 12 Participants' Need for Water Supplies
 The Windy Gap Firming Project would benefit 10 cities, two water districts and a power provider. Northern Water's Municipal Subdistrict is coordinating the permitting process for these residential providers, who face a serious lack of water supply as the region continues to grow.
Project Participants
Map shows the locations of the12 participants in the Windy Gap Firming Project.
Click map to view it.
Dedicated Storage
The firming project would meet a need recognized about 25 years ago by Windy Gap participants: a dedicated reservoir to store Windy Gap water.

Because of the project’s junior water rights, Windy Gap water cannot be diverted in years of low runoff. Conversely, during some wet periods storage space in Lake Granby is not available for Windy Gap water, which has a lower priority than C-BT Project water.
Chimney Hollow Reservoir would change the project’s reliable annual yield from zero acre feet of water to about 30,000 acre-feet, improving the reliability of water deliveries to participating water providers and, ultimately, the water users they serve. 

Chimney Hollow Reservoir
The 90,000 acre-foot Chimney Hollow Reservoir would be located southwest of Loveland and just west of Carter Lake, which holds about 112,000 acre-feet of water. 
The reservoir would be filled using Windy Gap’s original 1980 water rights decrees with appropriation dates of 1967, 1976 and 1980, and diversions would adhere to previously-agreed-upon limits.

Environmental Review

Because the Windy Gap Firming Project would move water through federally-owned Colorado-Big Thompson Project facilities, it must go through National Environmental Policy Act review. NEPA’s primary purpose is to identify potential project impacts and define strategies to mitigate them.
Federal and State Review The lead federal agency for the firming project’s NEPA process is the U.S. Bureau of Reclamation, which owns most C-BT Project facilities. Reclamation must publish extensive documents detailing the reasons for, operations of, and potential impacts of a project; address public comment; and then issue a decision. 

At the state level, the firming project required a fish and wildlife mitigation plan, which received unanimous acceptance from state officials in mid-2011, after public comment and collaborative, multi-agency development. The mitigation measures' goals include maintaining healthy stream temperatures for fish, providing flushing flows for stream habitat, offsetting water quality impacts and revegetating after construction.

The mitigation plan became part of the federal review process through inclusion in the firming project's Final Environmental Impact Statement, which Reclamation published in November 2011.

The state also approved the Municipal Subdistrict's separate voluntary plan to offer enhancements, or benefits, to the river, including increased funding for future stream restoration and habitat-related projects.

Learning by Doing
More than $10 million is earmarked for Grand County Learning By Doing (LBD) projects through Inter-Governmental Agreements among LBD parties. Agreements with Denver Water and Northern Colorado Water Conservancy District spell out conditions for the funding and timing through permitting and other milestones, as well as earmarking funds for specific activities (stream temperature, aquatic life, riparian vegetation health, etc.). Additionally, Denver Water and Northern Water have agreed to release water at critical times and to allow their water collection systems to be used to benefit the environment. These and other resources bode well for keeping Grand County's home waters healthy and flowing.

County Permit and Cooperative AgreementsAt the end of 2012, the firming project made significant progress with the issuance of a Grand County 1041 permit from the county's board of commissioners.

Issuance of the permit also signaled the go-ahead for several related agreements, which were the culmination of nearly four years of cooperation, negotiation, formal reviews and public comment sessions involving the Municipal Subdistrict, Grand County, the Colorado River District, the Middle Park Water Conservancy District, the Northwest Colorado Council of Governments, and others, including Trout Unlimited.

The cooperative agreements address environmental enhancements, or voluntary benefits, the Municipal Subdistrict will provide, including:

  • Stream habitat restoration
  • Investigation of a bypass around or through Windy Gap Reservoir and contribution of $2 million if constructed
  • Water quality studies on Grand Lake, Shadow Mountain Reservoir and Lake Granby
  • Additional water supplies to Grand County
  • Additional water supplies to the Middle Park Water Conservancy District
  • Efforts to protect the Colorado River and enhance its habitat
  • Efforts to support endangered species and recreation

Brochure: The Windy Gap Firming Project and the Environment 
Fact Sheet: Windy Gap Bypass Agreement

The Colorado River below the Windy Gap Project
The Colorado River below the Windy Gap Project: mitigation included maintaining minimum streamflows.

Historic Mitigation
The original Windy Gap Project, which was built in the 1980s, included years of efforts to determine mitigation measures for direct project impacts, in addition to negotiations for voluntary enhancements. The resulting mitigation measures included funding to benefit endangered fish species as well as water and wastewater treatment facilities.

Voluntary enhancements included a $10.2 million payment to the West Slope in lieu of building Azure Reservoir and water supplies for the Middle Park Water Conservancy District.

Participants' Conservation Efforts
Firming project water providers recognize the importance of conservation. The participants have diversified, substantive conservation programs that they continue to evaluate and strengthen.
The providers have already made significant progress by reducing water consumption by more than 25 percent since 1988. They accomplished this through supply-side measures such as improving facility efficiency, as well as on the demand side, by implementing metered billing and outdoor watering limitations.

Despite these efforts, conservation measures alone cannot meet future residential water demands. The firming project’s participants are expected to see a combined 2050 population exceeding 825,000 people – more than double what they had in 2005.

With this population increase comes increased need. Water demand projections for the participants show a shortage in supply of 64,000 acre feet in 2030 and 110,000 acre feet by 2050.

To address this shortage, participants are relying on multiple approaches, including conservation, reuse and additional supplies –including the firming project.


Chimney Hollow Reservoir would be located just west of Carter Lake, a Colorado-Big Thompson Project reservoir southwest of Loveland. Larimer County would oversee reservoir recreation, including fishing and non-motorized boating, as well as land-based recreation.
Chimney Hollow, with its varied vegetation and wildlife habitat, has been a priority for Larimer County’s Open Lands Program since 1997. Larimer County and Northern Water's Municipal Subdistrict jointly purchased the property in 2004. The Subdistrict contributed $4 million for 1,600 acres for the Chimney Hollow Reservoir site. Larimer County contributed $3.8 million to protect an additional 1,840 acres as open space.
Blue Mountain Conservation Area
The open space is part of Larimer County's Blue Mountain Conservation Area, which encompasses more than 9,000 acres. This area is a critical east-west corridor for migrating elk, black bear, bobcat and other wildlife. The open space will include about 10 miles of trails for hiking, biking and horseback riding.
For details on plans for recreation, visit Larimer County’s Chimney Hollow Open Space Web page. 

Larimer County holds tours of the future Chimney Hollow Reservoir open space west of Carter Lake.

Documents & Maps

Fact Sheet: Windy Gap Firming Project 
Brochure: The Windy Gap Firming Project and the Environment
Fact Sheet: Windy Gap Project Bypass Agreement

Articles, News Releases & Correspondence

State Backs Windy Gap Water Storage Project - Coloradoan

How Water Is Reshaping the West – Nova Next/Rocky Mountain PBS, November 11, 2015

Chimney Hollow Reservoir Project Moves Forward - December 19, 2014

USBR Signs Record of Decision for Windy Gap Firming Project - December 19, 2014

Windy Gap, NISP Essential to Water Manager's Future Plans
KUNC - June 4, 2014

Editorial: Water project proposal needs consideration – Longmont Times-Call, September 25, 2013

Windy Gap Firming Front Range Water Supply Report, U.S. Army Corps of Engineers – June 14, 2013

Windy Gap Firming Gains Grand County's Approval
Northern Water Subdistrict Press Release - Dec. 4, 2012

Trout Unlimited Supports Windy Gap Project
TU press release - Dec. 5, 2012

Agreement puts Colorado River On Road to Recovery
Colorado Trout Unlimited website – December 4, 2012

Windy Gap Firming Permit Brings Chimney Hollow Closer to Reality
The Berthoud Surveyor – January 3 2013

Thumbs Up For Windy Gap Project; Thumbs Down for Moffat
Denver Post – January 10, 2013

Commissioners Approve 1041 Permit for Windy Gap Firming
Sky-Hi News - Dec. 5, 2012

A Victory for Upper Colorado River Conservation
Denver Post – Dec. 5, 2012

Participants Request Governor's Support
Letters - May 23, 2012

EPA wants further review of project
Denver Post - Feb. 17, 2012

Windy Gap Firming Final EIS Released
Northern Water press release -  Nov. 30, 2011

River diversion project closer to reality
Boulder Daily Camera - Dec. 11, 2011

Editorial: Windy Gap Firming Project gets good news
Greeley Tribune - Dec. 7, 2011

Windy Gap Firming Project receives a boost
Greeley Tribune - Nov. 30, 2011

Commission approves water plans
CDOW press release - June 9, 2011

Federal Permitting Process Documents
On December 19, 2014, following years of effort, the U.S. Bureau of Reclamation, Northern Water and its Municipal Subdistrict signed a new Windy Gap carriage contract. Simultaneously, Reclamation issued a Record of Decision for the Windy Gap Firming Project, enabling continued progress to design and construct Chimney Hollow Reservoir.

To view the Record of Decision, Final Environmental Impact Statement and other associated documents, click the links below or visit Reclamation's Windy Gap Firming Project EIS page.

Record of Decision – Windy Gap Firming Project Final Environmental Impact Statement, Dec. 19, 2014
Final Environmental Impact Statement 
Executive Summary 
New Technical Reports 
Published by the U.S. Bureau of Reclamation in 2011, the FEIS details project mitigation measures and addresses public comment received after publication of the previous impact statement.

Draft Environmental Impact Statement
Executive Summary 
Published by Reclamation in 2008, this document describes why the project is necessary and why Chimney Hollow Reservoir is the preferred alternative for both the participants and Reclamation.
Technical Reports  
Prepared by third-party consultants and published between 2006 and 2008, these reports provide additional details on different resource impact analyses for the Draft Environmental Impact Statement.

Purpose and Need Report
Prepared by third-party consultants and published by Reclamation in 2005, this document details the existing and future water needs for each of the 13 water providers participating in the firming project.

State Mitigation Documents
Fish and Wildlife Mitigation Plan
Developed by the Municipal Subdistrict with state biologists, this 2011 state-approved plan details measures to mitigate impacts.

Fish and Wildlife Enhancement Plan
Developed by the Municipal Subdistrict with state biologists, this 2011 state-approved plan details voluntary efforts.

Governor's Letter on Mitigation
Written by Colorado Gov. John Hickenlooper, this 2011 letter says the mitigation plan comprehensively addresses impacts.
Windy Gap Firming Project map Windy Gap Firming Project
Map shows proposed Windy Gap Firming Project west of Carter Lake.
Click map to view it.
Windy Gap Firming Project Participants map Project Participants
Map shows the locations of the12 participants in the Windy Gap Firming Project.
Click map to view it.
Chimney Hollow Reservoir map Chimney Hollow Reservoir
Map showsthe proposed Chimney Hollow Reservoir southwest of Loveland, just west of Carter Lake.
Click map to view it.

Subdistrict Agreements with West Slope Stakeholders
Grand County Resolution to Approve Agreements
This December 2012 resolution affirms commissioners' approval of several agreements between the Municipal Subdistrict and multiple West Slope stakeholders.

Windy Gap Bypass Funding Agreement
Fact Sheet: Bypass Funding Agreement
This agreement addresses funding for the potential construction of a bypass around or through Windy Gap Reservoir. Signatories include Grand County, the Municipal Subdistrict, the Windy Gap Firming Project Water Activity Enterprise, Trout Unlimited and the Upper Colorado River Alliance.

Windy Gap Firming Project IGA
This 2012 agreement specifies benefits the Municipal Subdistrict will provide to West Slope stakeholders. Signatories are to include the Municipal Subdistrict, the Middle Park Water Conservancy District, the Colorado River District and the Northwest Colorado Council of Governments.

IGA for the Learning by Doing Cooperative Effort
This is intended to engage agencies in a cooperative, ongoing process to maintain the aquatic environment in basins upstream of the Colorado River's confluence with the Blue River. Signatories are to include Northern Water, the Municipal Subdistrict, Grand County, Middle Park Water and the Colorado River District. 

Grand County 1041 Permitting Documents
Grand County Resolution to Approve 1041 Permit
This December 2012 resolution affirms commissioners' approval of the firming project's 1041 permit to address project impacts in Grand County.

Grand County 1041 Permit Application
Prepared by the Subdistrict and submitted on behalf of firming project participants in June 2012, this relates to project plans and conditions, such as operation and construction.

Alternatives Reports
Alternatives Report
Prepared by third-party consultants and published by Reclamation in 2005, this identifies a reasonable range of alternatives that could meet project water providers’ needs.
Alternative Plan Formulation Report 
Executive Summary 
Prepared by consultants and published in 2003, this details the pre-National Environmental Policy Act evaluation of 170 methods to potentially accomplish project goals and how they were narrowed down to seven.

Engineering Reports
Chimney Hollow Dam and Reservoir Feasibility Study, GEI Consultants, April 1997

Chimney Hollow Dam and Reservoir Preliminary Design Report, AECOM, March 2014

Windy Gap Firming Contacts

For information about the Windy Gap Firming Project, contact Northern Water staff:

Jeff Drager
Project Manager

Brian Werner
Public Affairs Coordinator

For information about Chimney Hollow open space, contact Larimer County staff:

Rob Novak
Education Coordinator, Department of Natural Resources

Receive Windy Gap Firming Project Updates & Information To get Windy Gap Firming Project updates e-mailed directly to you or your organization, register for a Northern Water Online Account.
Windy Gap Firming Project Questions or Comments
If you have a question or comment about the Windy Gap Firming Project, please complete the required fields below and click the Send button or e-mail any of the people listed on the left side of this page.

Contact Us:
Items with an * are required.