VERMILLION, S.D. — The Missouri River waters gurgle by quickly, taking small chunks of sand downstream with them.
A year ago, the sand was at the bottom of the river, near the opposite shore. Now, that sand has been dredged out, sent through a pipe beneath the river’s surface and used to add acres to an old sandbar.
The fresh sand and small rocks worn round and smooth from years of tumbling along the river bottom now provide new habitat for endangered shorebirds that depend on the openness of the sandbars to hatch and raise their young.
“What we’ve seen from other projects we’ve done is those sandbars in their first year were the most productive and well-used bars on this stretch of river,” said Tim Fleeger, a U.S. Army Corps of Engineer environmental resources specialist.
The Corps of Engineers showed off nearly $5 million worth of sandbar and other habitat restoration near Vermillion Tuesday, improvements officials said will help save the least tern and piping plover and return a small portion of the river to its original condition.
The three projects include:
— A 74-acre sandbar construction project two miles upstream from the Vermillion-Newcastle bridge.
— A 44-acre sandbar just downstream from the bridge.
— A 15-acre backwater restoration, built in conjunction with the South Dakota Game, Fish and Parks department.
The backwater is 6 to15 feet deep, including deeper holes to protect fish in the winter when the river level is lower. Logs and tree branches are clustered along the shore to provide additional fish habitat. The backwater will also serve as feeding grounds for terns. The habitat is limited in the stretch of river between Gavins Point Dam and Ponca, Neb., Fleeger said.
“We’ll gain some ecosystem benefits,” he said.
Until construction began in October, the backwater area was solid ground. Workers have dredged the area, sucking the sand across the river and depositing in onto the larger sandbar construction site. The sandbars will be finished by early May, in time for the birds to nest. The backwater will be finished by the end of this week.
The larger of the two sandbars already existed, but its size is now nearly tripled to a mile long. The smaller sandbar was shallow and usually is under water during the birds’ nesting season. Both will be built higher so they won’t be submerged or washed away when the river rises.
“In the river there are some sites where sand naturally accumulates. We’re capitalizing on sites nature has chosen,” project manager Kelly Crane said.
Sand from the river bottom is being used to create the second sandbar. Dredging began last week and continues around the clock. Corps engineers have studied the river channel and are making sure their work doesn’t disrupt the river’s flow, even though the channel can naturally shift.
“We want to be affecting the pattern of flow as little as possible,” Fleeger said.
— About 500,000 cubic yards of sand were dredged to enlarge an existing sandbar in the Missouri River. Two-thirds of the sand came from a newly created backwater area, the other one-third from the river bottom.
— The dredge pumps a mixture of about 80 percent water, 20 percent sand during construction. Working around the clock, the dredge can deposit 8,000-12,000 cubic yards of sand on the new sand bar each day.
— The U.S. Army Corps of Engineers requires that dredging can not make the river deeper than its deepest point. To meet that requirement, workers can remove about 4 feet of sediment from the bottom of the river while dredging.