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Corps Extends Comment Period On Dworshak Reservoir Ecosystem Restoration Effort
Posted on Friday, February 24, 2012 (PST)

The U.S. Army Corps of Engineers’ Walla Walla District, announced Feb. 16 that it was extending by 30 days the public comment period on an Environmental Assessment and draft Finding of No Significant Impact for the “Dworshak Reservoir Nutrient Supplementation Pilot Study.”


The comment period extension will now end Saturday, March 17. The Corps extended the public comment period to accommodate wider public input.


The EA is the next step in the Corps’ National Environmental Policy Act compliance, as it plans to resume the reservoir ecosystem restoration pilot study in 2012. Last year, the U.S. Environmental Protection Agency issued a National Pollutant Discharge Elimination System permit to the Corps effective Oct. 15, 2011 after its environmental review and consideration of public comments.


The NPDES permit allows application of liquid fertilizer to west-central Idaho’s Dworshak Reservoir as an ecosystem treatment. The reservoir is created by the Corps’ Dworshak Dam, which has since completed in 1972 backed up the North Fork of the Clearwater River.


Corps officials say that since dam construction, a nutrient-poor reservoir environment has developed with the ratio of nitrogen to phosphorus became increasingly out of balance. Since a pilot project began in 2007 low concentrations of nitrogen fertilizer have been added to the reservoir in spring, summer and fall in order to boost the aquatic species food chain.


Idaho Department of Fish and Game has partnered with the Corps on the project, which is designed to improve the reservoir ecosystem, which in turn should enhance Idaho sport fishing opportunities, the Corp says.


Results during the first four years (2007-2010) of the project were encouraging, according to a Corps fact sheet. Adding nutrients initially influenced the bottom of the aquatic food chain. Monitoring efforts have shown improvement in beneficial forms of edible phytoplankton (algae) that in turn can be eaten by zooplankton (larger microscopic organisms). As the project continued, an increase in zooplankton abundance was observed. That is important since zooplankton is the primary food source for kokanee and other aquatic organisms, the Corps says.


The IDFG reports seeing modest increases in fish size, primarily in weight (the fish are heavier for their size). This is a good sign of ecosystem improvement. The agency notes, however, that in a large reservoir like Dworshak, it takes several years for nutrients to work their way up the food chain. Consequently, this positive response in the fish population is just beginning to be observed.


The Corps fact sheet says there is no evidence that recent nutrient additions at Dworshak have caused blue-green blooms. Blue-green algae have predominated in the Dworshak Reservoir because they compete better under low-nitrogen conditions. Nutrient (nitrogen) addition is expected to promote growth of other species of beneficial algae and reduce blue-green algae. Over time, this could work to delay the onset of blue-green blooms and lessen their severity – a benefit to public health, according to the Corps.


The occurrence of blue-green algae in areas of the reservoir with no nitrogen addition is another indication that the nutrient enhancement program is not the cause of the blue-green blooms.


With the extension, public comments on the Corps EA must be postmarked, faxed or e-mailed to the Corps by March 17, 2012, to be included as part of the public record. E-mail comments should be sent to Faxed comments should be sent to 509-527-7832. U.S. Mail comments should be mailed to U.S. Army Corps of Engineers, Walla Walla District, Environmental Compliance Section, ATTN: John Leier, 201 North 3rd Avenue, Walla Walla, WA 99362-1876.


The EA and draft FONSI documents are available for viewing at the Corps’ website at; Orofino City Hall at 217 First Street, Orofino, Idaho; Clearwater County Courthouse, 150 Michigan Avenue, Orofino, Idaho: and Recorder’s Office, Room 100, Nez Perce County Courthouse, 1230 Main Street, Lewiston, Idaho.


To learn more about the Corps of Engineers and its mission in the Walla Walla District, see the District website at


The Corps says that the project has already gone through rigorous review process, including a series of public meetings starting before the project began operations. Actions were taken to acquire applicable permits and address requirements of other natural resources agencies. Several agencies were consulted by the Corps prior to starting the pilot project, including the Idaho Department of Environmental Quality.


The Corps initially applied for a NPDES permit in 2007, prior to the start of the pilot program. In 2010, the EPA determined that a NPDES permit was required for the project, and nutrient applications were promptly discontinued to allow resolution.


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