Southern Water Supply Project II

Project Description
Southern Water Supply Project II is a proposed pipeline project that will supply high-quality Colorado-Big Thompson Project and Windy Gap Project water from Carter Lake Reservoir to the City of Boulder, Left Hand Water District, the Town of Berthoud and the Longs Peak Water District. These four entities presently depend in part on seasonally operated open canals which at times are subject to water quality concerns. The new pipeline will provide a year-round secure water supply to these entities.
The current construction cost estimate is $38 million; the total project cost estimate with design and right-of-way costs is $44 million. All costs will be borne by the three project participants. 

The SWSP II will traverse from Carter Lake Reservoir south to the City of Boulder’s Boulder Reservoir water treatment plant, a total distance of 20 miles. The first 12 miles will parallel the existing SWSP pipeline from Carter Lake Reservoir to Saint Vrain Road near the Longmont Municipal Airport. The last 8 miles will go south and west toward the City of Boulder’s water treatment plant. The project will parallel the northern portion of the original 110-mile  Southern Water Supply Project (completed in 1999) before heading south and west towards Boulder Reservoir. The pipeline will be 36-inch and 34-inch diameter steel pipe.

Project Timeline
The Boulder County Commissioners approved a 1041 Permit for the pipeline location and construction through Boulder County in 2012. This process evaluated alternative routes considering the environment, land use and project cost. Design began in 2016 and right-of-way acquisition activities followed. Construction will start in late summer of 2018 and be completed in early 2020.

Project Contacts
Route of the Southern Water Supply Project II pipeline