Corps may use dredged sand to bolster Duluth's Park Point beach
The U.S. Army Corps of Engineers is considering using sand dredged from the Duluth-Superior Harbor to resupply rapidly eroding Lake Superior beaches along Minnesota Point.
The erosion problem, spurred by near-record-high lake levels and made worse during the big lake's epic storms, has eaten away hundreds of thousands of cubic yards of sand — reaching so far onto shore that mature trees in the Minnesota Point forest are falling into the lake.
Shipping channels in the harbor are dredged periodically to keep them deep enough for lakers and salties to carry full loads. The dredge material can be sucked off the bottom with giant vacuums and pumped, through tubes, to wherever it's needed — even miles away.
Supporters say adding tons of new sand may be the only way to buffer the beaches along Minnesota Point — also known as Park Point — if Lake Superior levels remain high.
"The life of Park Point beaches and the preservation of the old-growth trees within the natural area on Park Point may depend on it," said Jim Sharrow, director of port planning and resiliency for the Duluth Seaway Port Authority.
The earliest that can happen, however, is next summer when the next maintenance dredging is scheduled to occur. But any action is more likely in 2019, Corps officials noted.
Before then, the Corps and the Minnesota Department of Natural Resources would have to agree on a dredge disposal plan and so-called 401 certification under the federal Clean Water Act.
Marie Strum, chief of the Engineering and Technical Services Division at the U.S. Army Corps of Engineers' Detroit office, earlier this month viewed some of the worst eroding sections of Minnesota Point from a boat and said she was surprised by how much sand had been pulled away from the beach.
"We're just in preliminary discussions with the MPCA and DNR on starting beach nourishment in Duluth again," Strum told the News Tribune. "It was pretty impressive, when we took a boat out there, to see how much sand was gone. There are old-growth pines just crumbling into the lake."
Strum said the Corps already has ongoing environmental authority to add sand along the beach within 3,000 feet of both the Duluth Entry and Superior Entry to help buffer navigation channel walls from the lake's unrelenting forces.
Dredged sand, which the Corps calls beach nourishment (once called dredge spoils) had been used for decades to shore up the Minnesota Point/Park Point beach, especially in the mid-1980s when the lake was at record-high levels. The lake now sits at the highest early winter levels since those records were set, and some residents along the beach have suggested more sand be brought in to create a bigger buffer between the waves and their property. Dredged material was used throughout the 1990s and into the 2000s as well.
But not everyone liked the idea. Some Park Point residents complained that the fine-grain sand from the harbor, when dumped on the beaches, blew into their homes. The Corps eventually stopped using beach nourishment on the lake side of Minnesota Point in 2009 after receiving complaints that the pumping was spurring too much silt or turbidity in the lake. The Minnesota DNR at the time asked the Corps not to use dredged material that contained fine particles of clay, such as from the Nemadji River outlet, saying the silt could cover critical fish spawning beds in the lake.
Strum said the turbidity seen during 2009 was more likely caused by a heavy rainfall pushing clay silt out of the Nemadji River and was coincidental to the dredge sands project.
"We got a lot of bad press at the time. But everything we've seen shows that this (beach nourishment) really doesn't cause much turbidity. No more than a passing ship, and certainly far less than a storm," Strum said. "We are going to have to work slowly and get people on board with this. But there's no doubt that beach nourishment can help the situation there. It helped before until we stopped doing it, and we probably shouldn't have stopped."
Since 2009 the dredged material has been either stored at Erie Pier, the harbor dredge containment area near the Duluth side of the Bong Bridge, or, more recently, used to rebuild shallow-water fish habitat in the harbor. Those projects, including one off the mouth of Miller Creek in Duluth's Lincoln Park neighborhood, proved to cause little or no turbidity or siltation, a study by the U.S. Geological Survey found. The dredge material was used to fill deeper areas to just a few feet deep to create habitat for young fish. More dredged sand is slated to be pumped to near 40th Avenue West to create similar habitat next summer.
Strum said the Corps or other groups could lobby for additional funding to conduct extra harbor dredging in 2018 to provide more sand for Lake Superior beaches.
Dan Breneman, Lake Superior Unit project manager for the Minnesota Pollution Control Agency, said there's also support for using underwater sand berms in the harbor to protect shoreline along that side of Minnesota Point, which has been hammered by high water and wave action.
Supporters of beach nourishment say the sand taken from shipping channels is generally new material that flowed down the St. Louis River. Tests have shown it to have little or no contaminants, unlike the silt in several harbor slips and bays which continues to carry legacy toxic pollutants. That material could not be used for beaches.
"The habitat projects showed that this (sand dredged for shipping channels) really doesn't cause a turbidity problem... and we know that it's clean material," the Port Authority's Sharrow said. "So if we can use the material we have to move anyhow, that's an added benefit and relatively little extra cost."