ST. LOUIS -- Two years after the U.S. Army Corps of Engineers halted dredging projects in Missouri aimed at restoring habitat for an endangered fish along the Missouri River, Sen. Kit Bond has again raised concerns about the strategy, saying it's environmentally unsound.

When the corps halted its Missouri projects in 2007 because of the state's objections, it went on to Kansas, Nebraska and Iowa, where the agency says it was welcomed as it created Missouri River habitat for the endangered pallid sturgeon. The corps said Monday it eventually will have to return to Missouri, if it's to meet a federal mandate to improve conditions for the pallid sturgeon, which thrived before upstream dams and a stabilized navigation channel changed the Missouri River's flow.

By 2020, the corps must build 20,000 acres of shallow water habitat from Sioux City, Iowa to St. Louis.

But Bond, R-Mo., last week said he would do his best to derail the corps' $70 million funding request for next year's piece of the multiyear Missouri River Recovery Project.

During a Senate hearing, Bond said creating side channels and chutes for the endangered fish requires dumping 548 million tons of farmland soil -- containing 350,000 tons of phosphorus -- into the Missouri River.

Not only does the process waste precious soil, particularly unpalatable in a state that dedicates a special tax that generates $42 million a year for soil-conserving practices, Bond said, it also contributes to low oxygen, or hypoxia, in the Gulf of Mexico.

Mike George, the corps' Missouri River Recovery Program manager, based in Omaha, Neb., said Bond's tonnage numbers for soil and phosphorus are exaggerated, and that the corps is reintroducing sediment -- 60 percent to 80 percent of it sand -- and not moving soil from upland farms. George said the nutrients are a small contributor to the hypoxia problem in the Gulf of Mexico.

The corps came upon its solution by accident, when 1993 flooding created a new channel in the Lisbon Bottoms, 15 miles upriver from Booneville, Mo., that started to produce sturgeon and other species. "This became the template to create natural process," he said.

The new side channels allow some river water to travel more slowly and at a shallower depth to provide more favorable fish habitats. Channels are designed so that further erosion will occur over time, the way river erosion used to occur naturally.

When the corps suspended habitat restoration work in Missouri in 2007, Nebraska, Kansas and Iowa encouraged the agency to step up the program in their states. Eventually, George said, the corps will have to create habitat in Missouri or get new instructions from the U.S. Fish and Wildlife Service.

George said the sturgeon, as well as other fish, seem to be responding to the slower water, which holds more insects and smaller fish to feed on.

The corps has asked the National Academy of Sciences to examine whether sediment dumped into the Missouri River reduces water quality and contributes to hypoxia. Results are expected next summer.

The academy also has been asked to look at nutrient management in the entire Mississippi River Basin, which includes the Missouri, for the Environmental Protection Agency.

George said he awaits the report eagerly.

"Maybe there is a better way to do this," he said.