Aging infrastructure, aridification, mine spills and wildfires pose serious dangers to the city of Durango’s water supply, which is mostly the Florida River and to a lesser extent the Animas River.
For several years, the city has been considering a pipeline connecting Terminal Reservoir to Lake Nighthorse, where the city has a water allocation of up to 3,800 acre-feet per year thanks to the Animas-La Plata Project.
A city news release says that based on the average daily demand, the city currently has just over two weeks of water supply storage. Tapping into Lake Nighthorse would increase its water supply storage to over four months.
The city is now considering three alternative locations for the pipeline’s placement, which were analyzed by Durango consulting firm Plummer last year.
Durango Public Works Director Allison Baker said in an email that none of the alternatives have been selected or determined to ultimately be more favorable than other options. However, Plummer did weigh the pros and cons of each alternative presented.
Plummer recommended three connection points, two pump station options and three pipeline placement options in its analysis.
In its analysis, the consultant highlighted its recommended connection point of a currently idle 36-inch valve near Ridges Basin Dam at the lake.
The other options are a connection to an intake structure on the north side of the lake and a connection to the discharge side of a pump in the Animas River.
The city already holds partial ownership of the 36-inch valve near Ridges Basin Dam. But the Southern Ute Indian Tribe, Ute Mountain Ute Tribe and La Plata West Water Authority already have an ownership agreement, and the city would have to pursue ownership in some form or lease the infrastructure there.
The alternative river pump connection comes with what appears to be an insurmountable challenge. Plummer’s analysis said reversing water flow on the Ridges Basin Inlet Conduit, which feeds water from the Durango Pumping Plant to Lake Nighthorse, isn’t practical because “the elevation change exceeds the maximum, physically possible suction lift.”
Because water will need to be pumped up to the College Mesa Water Treatment Plant, the analysis also includes two alternatives for pump stations.
The first alternative is a new pump station on the south side of Larry Valdez Byway called Bear Traps, the analysis said. The pump would connect to the current 30-inch Santa Rita Pipeline and then be transferred to College Mesa Water Treatment Plant. This would reduce the energy demand on pumping up to the treatment plant.
The second alternative taps the existing Santa Rita pump station, which currently pumps water from the Animas River intake to College Mesa Water Treatment Plant, according to the analysis. With this option, Lake Nighthorse would connect to the Animas River intake pipeline, transfer water to the Santa Rita pump station’s wet well, and then into the 30-inch Santa Rita pipeline to the water treatment plant.
The analysis lists three pipeline placement options, recommending the first option, which entails constructing a 2.4-mile long, 48-inch pipe down La Posta Road (County Road 213) and another 5 miles of 30-inch pipe to the Santa Rita pump station.
Although that option is Plummer’s recommendation, the analysis noted the infrastructure would pass through the Southern Ute Indian Tribe reservation boundary where archaeological resources reside.
“This alignment will impact multiple private residents and business owners,” the analysis said. “This is the most expensive alternative; however, it provides an opportunity for a collaborative project with other (Animas-La Plata Project) members.”
The second alternative pipeline route would also utilize the first recommended 36-inch valve connection near Ridges Basin Dam. But this option requires drilling a 30-inch pipeline directly through the mountains toward Bodo Park in Durango.
Drilling through the mountains to the Santa Rita pump station would actually be less expensive than snaking a pipeline down La Posta Road to the pump station, the analysis said. But it has “inherent risks” because it would be the longest horizontally directional drilled pipeline in Colorado.
The third and final alternative proposed is the most cost effective, according to the analysis. It would have the pipeline connect to the north side intake at Lake Nighthorse, the second recommended connection point, and carry water along County Road 210, ending at the Santa Rita pump station.
The city would have to negotiate ownership or a lease for access to the connection.
cburney@durangoherald.com
A previous version of this story attributed the city of Durango’s main water source to the wrong river. It’s primary source of water is the Florida River.
