Goose Pasture Tarn Dam Project
CONSTRUCTION
Overview and Cost
Planned Rehabilitation will include:
Replacement of the existing service spillway and emergency spillway with a single overtopping concrete spillway.
Construction of a 2.6-foot raise of the dam crest for flood protection only (the raise will not result in additional reservoir storage capacity).
Construction of a new drainage system designed to safety control seepage through the dam.
Lining of the 54-year old outlet conduit to protect against outlet leaks that could impact dam safety.
The estimated construction cost, excluding engineering and permitting, is in the range of $15 Million to $20 Million. The Town has been selected by FEMA for funding ($10 million) under the Pre-Disaster Mitigation Grant program for the rehabilitation project, contingent on satisfying FEMA requirements. The Town plans to apply for a loan with the Colorado Water Conservation Board (CWCB) for the remaining construction cost.
Reservoir lowering is anticipated to impact residential wells in proximity to the reservoir. The Town is currently performing assessments and developing possible measures to reduce those impacts and will be contacting residents around the reservoir for those efforts.
CONSTRUCTION SCHEDULE
Construction planned from May 2021 to November 2023 (three construction seasons):
Season 1 – May 2021 to October 2021: Initial demolition of spillway structures, and construction of measures to divert reservoir flows during construction. Anticipate completely draining reservoir for about one month in August/September.
Season 2 – March 2022 to October 2022: Spillway, dam embankment, and outlet works construction. Anticipate lowering reservoir about 7.5 feet below the current restricted reservoir level during construction, completely draining the reservoir from September to mid-October, and allowing reservoir to operate at the original level (4 feet higher than the currently imposed restricted level) thereafter.
Season 3 – June 2023 to November 2023: Dam rehabilitation completed. Reservoir will then operate at the original level, 4 feet above the current restricted level.