TIMES-NEWS
TWIN FALLS — The Idaho State Department of Agriculture on Tuesday will launch a second round of treatment aimed at eradicating quagga mussels in the mid-Snake River.
The ISDA announced Monday morning that the 10-day comprehensive treatment will take place downriver of Hansen Bridge to Centennial Waterfront Park near Twin Falls, and that river access from the Hansen Bridge to Yingst Grade has been closed to the public.
A copper-based product called Natrix will be used and is the same one that the ISDA used last fall. The 2023 treatment significantly reduced the quagga mussel population in the Snake River, the ISDA said, but in September sampling discovered larval veligers in the river, indicating there is still a population of reproducing adult quagga mussels in the river.
The upcoming treatment is the first of the multi-faceted treatment plan. ISDA is planning a second treatment in November to target quagga mussels in still water and deep pool sections of the river.
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“This treatment plan reflects Idaho’s commitment to using every available tool to combat this threat,” ISDA Director Chanel Tewalt said in the news release. “By combining targeted treatments with ongoing monitoring, we are maximizing our efforts with the ultimate goal of eradication.”
The invasive quagga mussels spread rapidly and clog pipes that deliver water for drinking, energy, agriculture, recreation, and a variety of other uses. Established quagga mussel infestations have major impacts on fish populations, wildlife habitat and damage infrastructure so severely costing hundreds of millions of dollars in actual and indirect costs, ISDA said.
The ISDA has taken aggressive action to fight the mussels, and the Columbia River Basin is the only major river system in the U.S. that doesn’t have an invasive mussel infestation.
Idaho began operating boat check stations in 2009 to try to prevent quagga mussels from entering the state’s waterways, but Tewalt, in interviews with the Times-News, said state officials had actively developed a plan on actions to take if quagga mussels were ever detected.
Natrix is labeled and approved by the Environmental Protection Agency for these kinds of aquatic applications, the ISDA said. The treatment is being applied at one part per million, a rate intended to eradicate mussels but is below the drinking water standard for humans. The copper-based treatment application is occurring across an eight-mile section, less than 1% of the Snake River.
It is not required by product label, but out of caution to minimize exposure, ISDA advises the public to stay out of the dissipation area, from Hansen Bridge to Kanaka Rapids.
The treatment is expected to dissipate to normal river copper levels 18 miles downriver at Kanaka Rapids, the ISDA said. ISDA and the Idaho Department of Environmental Quality will routinely monitor the river from downriver of Hansen Bridge to Kanaka Rapid to evaluate treatment effectiveness and copper dissipation.
For more information, please visit idaho.gov/quagga.
Park closures
In addition, several parks near the Snake River have closed, but only one is slightly related to quagga mussels.
ISDA public information officer Sydney Kennedy said the ISDA does not have jurisdiction over the parks.
The city of Twin Falls announced Friday that Shoshone Falls Park has closed in preparation for reconstruction of sections of the roadway. The closure could last until mid-April, said city spokesman Josh Palmer.
A full closure of the Shoshone Falls Grade, including access to Dierkes Lake Park, will begin Oct. 21, and no public access will be permitted beyond the barricades at the top of the Shoshone Falls Grade near the Wild Rose subdivision, according to a news release.
“We understand this closure may cause inconvenience, and we appreciate the public’s patience as we work to improve the safety and accessibility of this popular destination,” Mayor Ruth Pierce said. “We encourage visitors to enjoy Dierkes Lake Park while it remains open and look forward to welcoming everyone back to a safer roadway to the increasingly popular Shoshone Falls Park.”
Palmer said traffic numbers show the fewest visitors during the winter so now is the least impactful on visitors. The park can still be accessed through the canyon trail system, but sometimes the trails are closed for winter because of ice buildup.
Centennial Waterfront Park will be closed to all vehicles from Monday to Oct. 31 as a paving project gets underway to allow for easier hot wash treatments of boats, kayaks and other vessels to eliminate any possible quagga mussels or larvae.
The project will make it easier for recreationalists who are having their vessels washed or as they wait to have them washed. The ISDA has required watercraft leaving the section of river to be hot washed in order to contain the mussels.
Plans for putting asphalt down in hot wash station areas have been in the works for some time, said Rocky Matthews, director of the Twin Falls County Parks and Waterways Department. Initially, the plan was to have the project completed in two parts, but with the waterway closure, it was decided to be done all at once.
A water retention area has already been dug to hold runoff from the hot washes.
For those still wanting to recreate on the water, Matthews points kayakers to a newly constructed kayak launch on the cove side of Murtaugh Lake.
“It’s a little farther out of the road but they can still get out in the water,” he said.
Twin Falls Park is also closed, as Idaho Power Co. last month began to make improvements to the park, including upgrading the shoreline and parking area and installing a vault toilet. The closure will last until the end of the year.
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