The U.S. Bureau of Reclamation this week will start a yearlong project to fix the intake structure that pumps water from the Animas River to Lake Nighthorse, which officials say was bringing in too much sediment.
Tyler Artichoker, southern facilities maintenance group chief with the Bureau, said it became apparent as Lake Nighthorse was being filled from 2009 to 2011 that the intake structure, located across the river from Santa Rita Park, was not functioning as designed.
The structure features air bladders that are filled and deflated to raise and lower the gates that allow water in. Ideally, the bladders would be inflated and positioned to take water from the surface of the river to minimize the amount of sediment coming into the system.
But issues soon started to arise with the bladders, Artichoker said, allowing for more sediment than planned to enter the system. The structure is still able to operate and handle the sediment, but it does increase operational and maintenance costs to deal with it, he said.
“We just didn’t quite have the control on those gates that was intended,” Artichoker said. “So we were getting quite a lot of sediment into the intake structure, and therefore, into pumps, the auxiliary equipment and into the reservoir.”
Sediment can wear out equipment faster than normal, ruin turbines and bury dam outlets. In worst-case scenarios, water-storage capacity can greatly decrease, though the issue hasn’t risen to that level at Lake Nighthorse, Artichoker said.
“There’s lots of reason to minimize sediment,” he said.
The issue hadn’t taken top priority over the years, Artichoker said, because operators have rarely had to pump water out of the Animas River into Lake Nighthorse since the reservoir has been full. That’s mainly because operators haven’t had to release water out of Lake Nighthorse for downstream users since the reservoir has been fully operational.
“Managers have only had to pump (out of the Animas into Lake Nighthorse) to replace water lost from evaporation, and they’re not doing that on consecutive years,” Artichoker said. “Lake Nighthorse is always at least 95% full, so the amount of pumping has been minimal.”
This year, the Bureau of Reclamation’s budget has allowed for the $6.5 million retrofit.
Artichoker said the contracted crew is mobilizing at the site this week and then will tackle the first phase of the project – putting up a coffer dam in front of the intake to be able to install a new system and gates.
The work will require crews to enter the Animas River, Artichoker said, but the impact to the public should be minimal.
“When constructing the dam, we’ll handle public safety like we did when we built the project, and put up signs to warn boaters to stay left,” he said.
The lion’s share of the work should be done by November, Artichoker said, but the project will likely wrap up in February 2021.
It could be a busy late winter and early spring for work in the Animas River.
The city of Durango hopes to get into the river next month at its intake structure, upstream of the Bureau of Reclamation’s project.
The city’s intake is just above Durango Whitewater Park, alongside Santa Rita Park. A project in summer 2016 to divert more water into the intake caused dangerous human-made rapids, many in the boating community have said.
As a result, the city hopes to do a temporary fix this winter before high flows from spring runoff hit. That project, city officials say, is currently out to bid seeking contractors.