Mussel infestations threaten Colorado reservoirs |

Mussel infestations threaten Colorado reservoirs

A sign in front of the boat ramp signals boaters to stop for inspection before entering Dillon Reservoir on Friday, July 12, at the Frisco Bay Marina.
Deepan Dutta /

The zebra mussel is a fingernail-sized mollusk causing havoc in waterways across the West. Fortunately for Colorado, the state’s reservoirs are free from the tiny invader, which is native to Russia and Ukraine.

However, worries of a looming infestation are on the rise. Colorado Parks and Wildlife reported this week that the agency had intercepted 51 mussel-infested boats so far in the young boating season — as many as were intercepted in all of 2018, which itself was a record, nearly doubling the previous record of 26 interceptions in a season.

Summit County has been on its guard against mussels for years, after “veligers,” or larvae, of the quagga mussel were detected for the first time two years ago in Green Mountain Reservoir near Heeney.

The reservoir has been “suspect positive” since, spurring an expensive reconstruction of the Heeney Marina to upgrade inspection and launch capabilities. Despite the efforts, other reservoirs usually will insist on decontaminating any boat coming from Green Mountain or other suspect or infested water bodies, particularly Lake Powell in Utah.

Invasive mussels threaten reservoirs by reproducing rapidly, eating all the microscopic food in the water and leaving nothing for other animals, clogging up hydroelectric power turbines and damaging other water infrastructure. What’s worse, once a mussel infestation takes hold, it may be impossible to get rid of without an intensive, multimillion dollar decontamination effort. Billions have been spent to combat the spread of the mussel, but it has not slowed the creeping infestation.

To combat the spread of zebra and quagga mussels, along with other invasive aquatic animals and plants, the state has been bolstering its aquatic nuisance species program.

Last year, the “Mussel-Free Colorado” act was passed into law, devoting money to the program as well as instituting an aquatic nuisance species stamp tax for resident and nonresident boaters.

At the Frisco Bay Marina, inspection standards are stringent as they are in other reservoirs across the state. Marina office manager Jennifer Shimp said Friday that the marina’s inspection station has been busy diligently checking vessels for any sign of aquatic hitchhikers.

“Each and every boat that comes in on a trailer, has a motor, or is a complex vessel with compartments that can’t be dried out efficiently, has to be inspected before getting into the reservoir,” Shimp said.

The inspection station stands between any boat and the ramp into the reservoir, and Shimp said two inspectors are stationed during operating hours to ensure every boat going into the reservoir is cleaned, drained and dried.

Any boat with pockets of water lingering in compartments or crevices may be subject to decontamination, along with boats with unidentifiable bumps, dirt or debris on the hull or other boat parts. Boat motors are a particularly popular area for mussels to use as a Trojan horse, and they get extra scrutiny with flashlights and magnifying glasses, if needed.

If a boat needs to be decontaminated, Shimp said it would be subject to blasts of water heated to 140 degrees, a temperature that would kill any lingering mussels or other unwanted critters.

The length of the inspection and decontamination processes are dependent on the complexity of the vessel and level of infestation. Contaminated boats are quarantined and may take a week or more to be decontaminated.

To expedite reentry of boats taken out of clean Colorado reservoirs, a seal and receipt system allows boat owners to reenter water bodies in Colorado without the need of a full, cumbersome inspection.

“When a boat comes off the water for the day, we’re going to seal off the boat with a wire and a seal that you can’t tamper with,” Shimp said. “If it’s broken, you’ll have to go through the entire intense inspection again. But as long as all the information matches, and the boat comes out of a body water that is clean and clear, boaters can get through this fairly intense inspection quickly.”

For more information about the state’s aquatic nuisance species program, as well as boat inspection and decontamination procedures, visit the Parks and Wildlife website at

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