Visitors to Lake Nighthorse would do well to arrive early and carpool when possible for recreational activities, according to Durango Parks and Recreation, because of construction scheduled to begin promptly after Memorial Day weekend.

Durango Natural Resources Manager Owen Tallmadge said parking availability will not be affected by construction, but visitors should expect delays as a result of narrowed traffic flow through the construction site, which is right by the entrance to the lake.

The scope of construction includes a new ticket booth, storage for equipment, an office for city lake personnel, xeriscaping and a stormwater quality and detention pond. Construction is expected to be completed sometime in December.

But the biggest element of construction is a new and improved motorboat decontamination system, which will help prevent invasive species of mussels, snails and aquatic plants from taking over the lake.

Tallmadge said the decontamination system will be built in an entry station building with hoses funneling to the outside through slots in the wall.

The city entered an agreement with the U.S. Bureau of Reclamation and Animas-La Plata (ALP) Project, which helped construct Lake Nighthorse, in 2017 to manage recreation there, Tallmadge said. That entails ensuring visitors and their motorboats aren’t harboring invasive species such as quagga mussels, zebra mussels, New Zealand Mudsnail and Eurasian Watermilfoil.

The best tools to cleanse a motorboat of mollusks are high-pressure and hot water up to 140 degrees. But the city’s current decontamination unit at Lake Nighthorse – a trailer-mounted pressure washer and water tank – is unable to efficiently regulate water temperature, he said.

If the water is too hot, it can melt boat parts. If it’s not hot enough, it won’t effectively kill invasive organisms.

Tallmadge said staff members are constantly regulating water temperature manually using a burner switch, which slows down decontamination and raises the chances of damaging boats while risking unwelcome mussels safely reaching the water.

“If the lake were ever to become infested with (aquatic nuisance species), the impacts would be devastating,” he said. “The dam and pump infrastructure and the water resources for which the reservoir was built could become severely compromised, but also the lake’s ecosystem and any form of recreation on or in the water.”

Colorado Parks and Wildlife describes zebra and quagga mussels as a “great ecological and financial threat” to Colorado.

“The invasion of these mussels can affect every Coloradan and visitors in some way and the impacts could be devastating,” CPW says on an informational page dedicated to the invasive species.

Zebra and quagga mussels reproduce prolifically, clog water infrastructure, quickly spread to new waters and are “difficult or impossible to eradicate,” according to CPW.

Most recently, Highline Lake northwest of Grand Junction tested positive in September 2022 for adult zebra mussels, according to CPW. The lake is still classified as “infested.”

Highline Lake tested positive for adult zebra mussels in September 2022. Highline Lake is currently classified as “Infested” with zebra mussels.

The new decontamination system will be able to maintain precise temperatures and gallons-per-minute flows for as long as needed to decontaminate motorboats successfully, he said.

Additionally, every system needs maintenance every once in a while. The new system will provide some redundancy between it and the old decontamination unit.

One last improvement is water reuse, Tallmadge said.

With the trailer and water tank unit, water runs off the curb into a gravel pond where it’s absorbed by the ground. He said the new system will recapture the water, filter it and make it reusable for decontamination again or for use in site irrigation.

The planned xeriscaping, for example, will be irrigated with recaptured water, he added.

The trailer-mounted decontamination unit will be used throughout the duration of construction.

Tallmadge said the new decontamination system should be fully operational in time for the 2025 Lake Nighthorse motorboat season, which begins mid-July and lasts through early November until an annual winter wildlife closure closes the park to public recreation.

cburney@durangoherald.com