Mussel spread threatens pipes at Hoover Dam, could cost millions | TahoeDailyTribune.com
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Mussel spread threatens pipes at Hoover Dam, could cost millions

Keith Rogers / Las Vegas Review-Journal
Kobbi R. Blair / Statesman JournalA sneaker covered in quagga mussels is seen in Salem, Ore. The sneaker was submerged in quagga-infested Lake Mead by Sam Chan, an aquatic ecosystem health educator with Oregon State University, to illustrate how they are able to bond to rubber and nylon. According to Chan, quaggas and their cousin, the zebra mussel, are two of the most-feared invasive species in the Pacific Northwest.
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LAS VEGAS – Invasive quagga mussels are adapting well to life in the desert, especially in Lake Havasu, where scientists have determined their reproduction rate is three times faster than when the pesky mollusks infested the Great Lakes years ago.

Leonard Willett, the Bureau of Reclamation’s quagga mussel coordinator for the lower Colorado River dams, said the effort to deal with quaggas, which were discovered last year first in Lake Mead and later downstream of Hoover Dam, still is in the monitoring phase, the first part of what he called the “reactive approach.”

“Reactive approach means you’re going to live with the mussels. You’re going to control them, but you’re going to live with them,” he said in a recent presentation to the Lake Mead Water Quality Forum.



He projected that as the infestation sets in and begins to clog hydroelectric power cooling pipes and other hardware in Hoover Dam’s operations, the maintenance-and-control bill could reach $1 million per year, especially if pipes get plugged with quagga colonies.

That could cause turbines to overheat and shut down until cooling pipes can be reamed of the invasive species.



“This is an evil critter, not good,” Willett said.

“It is going to cause a lot of problems when we’re going to have to install control measures,” he added.

Among the options for controlling the invasion is to use a bacteria product that targets the quagga mussels.

While that method still is being developed, Willett said it looked promising.

Other choices are mechanical filters and using chemicals such as chlorine to kill them, or a combination of filters and ultraviolet light.

At the end of the day, though, there would be shells from dead quaggas to dispose of and discharge permits to obtain.

So far, conditions for quaggas to thrive appear to be more than adequate at Davis Dam at the south end of Lake Mohave, north of Laughlin, Nev.

In October, a colony coated the dam’s exterior penstock gate like carpeting.

A month later, downstream at Parker Dam on Lake Havasu, quaggas covered sampling plates used to monitor them.

“At Parker Dam, there is a lot of colonization. At Parker, there is no hope. They colonize repeatedly,” Willett said.

With warmer year-round temperatures than bodies of water in the Great Lakes, quaggas are able to reproduce six times per year instead of two.

In addition, Havasu has the right mix of food, calcium and dissolved oxygen to sustain colonization.

With that, Willett said, “You’re going to get mussels. I’m not surprised.”

Near Hoover Dam, quaggas have been found more than 200 feet deep in Lake Mead.

Not only do they pose a threat to the cooling pipe system for hydroelectric turbines, but also to the network that supplies domestic water for workers and visitors at the dam.

They prefer to cling to flat, stainless-steel structures where water flows slower than 6 feet per second.

“Mussels really like stainless steel. They don’t like copper or brass,” Willett said.

A cousin of the quagga, zebra mussels, has turned up in Colorado’s Lake Pueblo State Park and in California’s San Justo Reservoir in San Benito County, off the California Aqueduct system.

According to the 100th Meridian Initiative, an organization that tracks the spread of aquatic nuisance species, quagga mussels are native to Ukraine’s Dneiper River drainage.

Like the zebra mussel, they were transported to the Great Lakes in the ballast water of ships in the mid-1980s.

Quagga mussels were discovered Jan. 6, 2007, in Lake Mead’s Boulder Basin.

Biologists believe they hitchhiked on a boat that was launched in the lake.

In a statement posted Jan. 16 on the California Department of Fish and Game’s Web site, Resources Secretary Mike Chrisman said:

“The discovery of zebra mussels in a central California waterway has us very concerned. Like its relative the quagga mussel, this species can cause significant environmental, recreational and economic impacts once established in a body of water. It is important that boaters do everything they can to help stop their spread.”

Jon Sjoberg, supervising fisheries biologist for the Nevada Department of Wildlife in Las Vegas, said his colleagues in California are puzzled how zebra mussels, instead of quaggas, arrived in Central California first after existing previously in the Great Lakes and Midwest regions.

The source is unknown, he said, although there’s speculation that anglers or bait buckets could have transported them, even ducks or waterfowl.

“It’s like they dropped out of the sky,” Sjoberg said.

The threat to Lake Tahoe waters remains real with at least some plans put in place to prevent the invasive mussels from making their way here.

An agricultural inspection station at Interstate 80 in Truckee and four others now looks for quagga and zebra mussels on boats coming into the state. This was made possible through a $2.5 million grant from the California Department of Food and Agriculture.

While the Meyers inspection station on Highway 50 didn’t make the list of inspection stations assigned to look for the invasive species, the Tahoe Resource Conservation District is hiring watercraft inspectors for the upcoming boating season to patrol Lake Tahoe waters. Also, the Tahoe Regional Planning Agency has looked at buying a portable boat wash station, which may be up and running by the end of July.

Zebra and quagga mussels are invasive species that disrupt the lake’s food chains, clog water pipes, and damage boats, docks, and ramps by attaching themselves to underwater surfaces.

– Tahoe Daily Tribune


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