Denver Water has begun work on a major rehabilitation project at its Antero Dam, on the South Fork of the South Platte River in Colorado.
The earthfill dam is 100 years old, and Denver Water wants to ensure it can operate for another 100 years. The reservoir holds about 20,000 acre-feet of water.
The work will cost $17 million to $20 million and take several years to complete. The entire rehab project is tentatively scheduled to be complete in 2018.
Antero Reservoir has been operating at a reduced capacity since May 2011, when Denver Water lowered water levels to investigate the condition of the dam and as a safety precaution to reduce water pressure and seepage.
Project work is being completed in phases. Phase 1, begun in August 2013 and completed in June 2014, involved building a sand trench to filter normal seepage from the dam. Phase 2 began in May 2014 and was completed in June 2015 and involved grading the embankment and ensuring appropriate drainage. Phase 3 started in August 2015 and is to be completed in November 2016 and involves installation a barrier wall inside the dam. Phase 4, to begin in spring 2017 and be completed in 2018, involves construction of a new spillway and improvements to the outlet works.
Work to drain the reservoir began in June and it is expected to be completely empty by the end of 2015. Water from Antero Reservoir is being recaptured in Marston Reservoir, which feeds Denver Water’s Marston Treatment Plant.
Refilling could begin as soon as spring of 2016. It will take one to four years to refill the reservoir, depending on the amount of snowfall and timing of snow melt.
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