Durango has always relied on the active flows of the Florida and Animas rivers for its water, but with aging infrastructure, mine spills, wildfires and the problems of drought-prone areas, it might be time to tap Lake Nighthorse.
Allison Baker, Durango public works director, told City Council in August that the Colorado Water Conservation Board had identified the Pagosa Springs-Bayfield-Durango corridor as lacking in access to water storage at reservoirs such as Lake Nighthorse outside Durango.
Specifically, reservoirs with municipal water lack the infrastructure to deliver that water to treatment plants and distribution systems, Baker said. This could prove problematic because of rapid growth and development in Durango and other areas, in addition to the four major risk factors that could threaten water supplies at virtually any time.
The proposed solution is a new water pipeline from Lake Nighthorse to Durango’s Terminal Reservoir, on College Mesa, which stores water short term until it is pumped into the city’s treatment facility and made ready for use. The pipeline would allow the city to access its share of water at Lake Nighthorse in the event its access to the Florida or Animas rivers is compromised or those waters become unavailable or unsafe for use.
City Council approved an allocation of $500,000 to the city’s water fund for a feasibility study and a preliminary design report. Justin Elkins, Durango utilities manager, said on Thursday he hopes the study will be completed by the end of the year.
He said the feasibility study is intended to determine if a pipeline from Lake Nighthorse to Terminal Reservoir can be installed and, assuming it can be, what materials would be used and the size of the pipe; where it would be installed; any land-use or zoning obstacles; and how much the project would cost.
The study will also examine if Durango is using its water in the most efficient way or if it will need to adapt in the future, he said.
“From the two watersheds that we draw from – the Animas and the Florida watersheds – we do have statistically significant reduction over the past 20 water years in precipitation, in total runoff, in the watershed’s ability to convert runoff,” he said.
Baker said at the City Council meeting Aug. 2 that the downward trend started in 1980.
“Personally, what I look at more than the trends … is that there is a lot of extreme years where we are extremely high or extremely low (in precipitation),” she said.
One goal of the feasibility study is to figure out a pipeline’s optimal location. The pipeline would have to traverse elevation changes between Lake Nighthorse and Terminal Reservoir.
Elkins said there are essentially two options for a pipeline: One would lead out from Lake Nighthorse down County Road 210. Another option is to direct the pipe out of the southwest side of the lakeacross land belonging to the Bureau of Reclamation.
But that comes with its own set of problems.
“That’s one of the issues that we see right now and why we want to do the feasibility study is to (see) how long will it take us to get federal permits to go out and do construction on Bureau of Rec land,” he said. “And if we do, what will the permits cost?”
Topography isn’t the only challenge for installing a new pipeline, he said. Archaeological sites on Bureau of Reclamation land would require extensive surveying to avoid disruption.
He said a project like this can quickly get complicated, which is why the city is in no rush. He anticipates the pipeline project wouldn’t break ground, if it proves feasible, for at least a few years.
Elkins said that aging infrastructure, wildfires, mine spills and aridification – essentially the watershed becoming drier – are the primary risks for the Florida and Animas watersheds.
“When we’re talking about resiliency in our infrastructure, what we want is the ability to supply water. We need to look at our source of supply,” he said.
Durango’s water rights on the Florida and Animas rivers are strong. Elkins said the city had water rights on the Florida River before Lemon Reservoir was built. But if there were to be an issue with the 9-mile pipeline that delivers water from Lemon Reservoir to Terminal Reservoir on College Mesa, then access to all of that water is lost.
That single pipeline is 70 years old and made of cast iron, he said. Although slip-line repairs are planned for the pipeline, it stands as an example of Durango’s vulnerability to having access to water.
He said the Florida River is the city’s primary source of water because its water is cleaner than water from the Animas River. But if the city loses access to either of those watersheds, it’s suddenly on a ticking clock to find more water because the Terminal Reservoir stores only up to a 10-day supply, or 3,800 acre-feet.
Lake Nighthorse contains about 350 days of water storage, although the actual time that water would last if needed could fluctuate depending on demand, Elkins said.
With peaks in flows and changes in demand, that range of 350 could become 100 if the city is drawing a lot of water in the future, he said.
During the presentation to City Council, Baker said 2021 was a peak year for offline time for the Florida waterline. A leak occurred off Timberline Drive and Florida Road in northeast Durango in December and lasted into January.
The pipeline was offline because of failure for more than 20 days. The previous record high in a single year, in 2016, was just over five days offline, she said.
“The risk to our system is increased by the potential pipeline failure through the Florida (River),” she said.
Wildfires also pose significant risks to Durango’s watersheds. The 416 Fire in 2018 killed more fish in the Animas River than the Gold King Mine Spill in 2015, Elkins said. They are so devastating because they fill water sources with organic carbon, which when mixed with chlorine as is used in the city’s water treatment system, essentially forms carcinogens, or cancer-causing substances.
He said it’s possible to allow water impacted by wildfire debris and ash to settle, but that takes time – time that the Terminal Reservoir with just 10 days of storage might not have.
Mine spills, such as Gold King that released an estimated 3 million gallons of water laced with heavy metals down the Animas River, also punctuate the need for water storage access, Elkins said.