Project Overview

Southern Water Supply Project II is a raw water pipeline project that will deliver high-quality Colorado-Big Thompson Project and Windy Gap Project water from Carter Lake to the City of Boulder, the Left Hand Water District, the Town of Berthoud and the Longs Peak Water District. These 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 secure, year-round water supply to all four of these entities.

The construction cost is estimated at $38 million; while the total project cost, including design, permitting, administration, management and right-of-way costs is approximately $44 million. All costs are borne by the four project participants.

The SWSP II traverses from Carter Lake south to the City of Boulder’s Boulder Reservoir Water Treatment Plant, a total distance of 20 miles. The first 12 miles parallels the existing SWSP pipeline (constructed in 1995) from Carter Lake to Saint Vrain Road near the Vance Brand Municipal Airport in Longmont. The last 8 miles heads south and west to the Boulder Reservoir Water Treatment Plant. The pipeline is 36-inch and 32-inch diameter steel pipe.

Quick Facts

  • Over 20 miles of steel raw water pipeline
  • Provides improved water quality by sending water through a pipeline instead of an open canal to the project participants (City of Boulder, Left Hand Water District, the Town of Berthoud and Longs Peak Water District)
  • Critical raw water transmission pipeline, and at various times of the year acts as the primary water source for project participants
  • Provides redundancy for the original SWSP pipeline
  • Construction began in 2018 and be completed in 2020