The U.S. Army Corps of Engineers maintains it is limited in its authority to look at the effect of Yuba River dams on fish populations.
In a statement issued Friday, the Corps said past congressional decisions in effect make the agency's primary focus to ensure the dams "do not collapse and harm the public."
The response was to claims by three environmental groups last week that Corps biological assessments on Englebright and Daguerre Point dams ignored the affects of the dams on fish.
The South Yuba River Citizens League, Friends of the River and American Rivers joined to decry the Corps assessments.
"Basically, the Corps is saying that Englebright's adverse impacts on threatened fish species have never been its concern," Bob Center, executive director of Friends of the River, said in a statement.
"The Corps would have us believe that its only responsibilities are emptying the trash cans, cleaning up the occasional oil spill and pumping out (portable toilets) at Englebright reservoir campground."
The biological assessments completed by the Corps were in connection with a new biological opinion being done by the National Marine Fisheries Service on Yuba River fish restoration. That follows a judge's order staying a lawsuit by the Yuba County Water Agency challenging a 2012 opinion.
The assessments will be used by National Marine Fisheries to complete the opinion due by May.
They note two categories of activities within Corps responsibility that might affect listed or threatened species — one the inadvertent release of contaminants into the reservoir and the other portable restroom pumping and herbicide application.
The Corps assessment notes that these activities "are not likely to adversely affect listed fish species and critical habitat in the lower Yuba River."
The environmental groups maintain the assessments amount to the Corps shirking its responsibility for the dams affects on salmon, steelhead trout and green sturgeon.
"The mere existence of the dams, as authorized by Congress, is a nondiscretionary activity and is therefore not subject to the consultation requirements in the Endangered Species Act," said the Corps statement.
At the same time the Corps said "we continue to do what we can within our legal authority to improve habitat conditions for species within the river."
The response notes that since 2007, the Corps has added more than 15,000 tons of gravel for spawning habitat. It also states that within the coming weeks it will place "large woody debris" in the river below Englebright to improve habitat.
The Corps statement said the next step "in determining what more can be done to improve fish passage conditions is a Corps reconnaissance study." That study looks at all options for fish passage or other improvements.