Dillon Dam Syphoning Project Update: 1-27-15

Here's the memo from Denver Water describing plans to resume bottom releases through the gates of the Dillon Dam: 

Good morning,

Denver Water plans to increase Dillon Reservoir’s outflow as we test the reservoir’s newly-refurbished outlet works – the gates that control the flow of water released from the reservoir into the Blue River.

As early as today (1/27), we plan to begin increasing the outflow, which has been steady at about 110 cubic feet per second, by about 35 cfs each hour. During testing, which could last through the end of February, flows will fluctuate between 100 and 500 cfs.  

The project, which restored the 50-year-old gates back to near-original condition, has relied on a temporary siphon system to make releases since late summer when the outlet works went out of service. The siphon system maintained outflows of about 100 to 110 cfs.

Denver Water and contractor Gracon Construction put the refurbished gates back into place in late December. The gates recently passed the first of two phases of testing, and now the facilities surrounding the outlet works – including the tunnel between the gates and the release point into the Blue River – are ready for the second phase of testing.

We are developing a plan to make a series of outflow increases with the need to protect the downstream fishery and structures in mind. These outflow changes are part of a rigorous testing regimen to ensure the gates meet high safety standards.

Increased outflows will also help us safely prepare for the upcoming spring season by lowering Dillon Reservoir’s elevation to create more space before runoff begins.

The temporary siphon system will remain available as a backup until the gates pass these operational tests. We look forward to completing this project soon and returning to normal operations using the outlet works – after they are carefully and thoroughly tested.

If you have any questions, please don’t hesitate to contact us.

Thank you,


Dana Strongin | Public Affairs 
Denver Water | t: 303-607-3132

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