Expansion of US magnesium channels could stir up toxic sediments of the Great Salt Lake

A proposed canal expansion project has raised strong concerns about plans to siphon water from the shrinking Great Salt Lake.

But a retired US Geological Survey scientist says US Magnesium’s proposal could also have disastrous consequences for the lake floor.

The company wants to extend its two inlets a total of 3.7 miles, resulting in a lot of displaced sediment. That could choke out important microbes and stir up toxins in the water column, according to Robert Baskin, a hydrologist with more than 30 years of experience studying the lake. He outlined his concerns in a lengthy letter he sent to Gov. Spencer Cox late last month.

“MagCorp’s proposed project,” Baskin wrote, using US Magnesium’s old nickname, “would destroy any remaining chance of that.” [Great Salt Lake’s] Ecosystem could recover quickly when lake levels rise again.”

US Magnesium applied to the US Army Corps of Engineers for a dredging permit in August, arguing that the lake’s receding waters are threatening access to the brine, which is used to produce magnesium and other minerals. The project also needs approval from the Utah Division of Water Quality, which has recently received a barrage of dissenting comments.

The plan calls for sediment to be drained over approximately 127 acres of lake bottom to allow the company to continue to siphon lake water at a rate of 100,000 gallons per minute. Its application includes the option to dredge even more if the lake continues to shrink, which Extractor says “may be necessary” over the next three to five years.

The governor’s Public Lands Policy Coordinating Office previously asked the Army Corps to approve the permit application, arguing that U.S. magnesium is an important native magnesium supply.

But after reviewing US Magnesium’s application, Baskin found the proposed dredging activities “unclear, misleading, overt or false,” he wrote, asking why the state supported the idea.

Francisco Kjolseth | The Salt Lake Tribune Small rock-like structures formed by bacteria in the Great Salt Lake have become visible along the north shore of Antelope Island. Older structures dry up and collapse as the water recedes, leaving dry domes. Some of the microbial mounds known as microbialites are collected and studied by researchers.

“I don’t do politics, apart from this letter,” Baskin said in an interview. “I am strictly scientific and try to be as open minded as possible. But apparently mining laws are written to help mining companies.”

Turbidity of the lake’s food web

Baskin has conducted extensive research on the lake’s microbialites – rock formations created by cyanobacteria that are an important part of the life cycle of the saltfly, which in turn feeds millions of migratory birds.

The microorganisms that Baskin calls “bioherms” essentially build their own homes by pulling minerals from the water and adding them together. They need water shallow enough to photosynthesize, but because the Great Salt Lake is so shallow, many have surfaced and dried up, killing their bacterial colonies.

“[Their] houses are [still] there and ready to be repopulated when the lake comes up,” Baskin explained. “But getting the lake to where it floods these now exposed bioherms is going to be very difficult, especially if MagCorp plans to pump 100,000 gallons a.” [minute] from the existing lake.”

Even microbialites that remain submerged are threatened by rising salinity as the lake shrinks and its minerals concentrate. Baskin pointed to the railroad embankment bisecting the lake, making the north arm hypersaline. It killed about 40% of the lake’s microbial colonies, he said, that built up its dome-like and now salt-encrusted rock formations over thousands of years.

(Leah Hogsten | The Salt Lake Tribune) The North Arm of the Great Salt Lake, Thursday, August 4, 2022. The North Arm of the dam is hypersaline, or saturated with salt, and colored pink by the microorganisms in the hypersaline water.

Baskin is also concerned about the mud created by excavating US Magnesium’s canals. Because the water of the Great Salt Lake is brimming with minerals, making it denser than fresh water, the sediment floats and moves around, possibly settling on microbial cells.

“Without light,” he said, “they will not live.”

In its filing, US Magnesium acknowledges that the dredging could have a “temporary impact” on water quality by clouding the lake with sediment in the work area, but claims it will not cause “long-term or permanent deterioration.”

Baskin disagrees.

In his letter to the governor, he included aerial photographs of two previous dredging events around Promontory Point, one near the railroad embankment and one at a marina. They show sediment migrating through the water by waves and currents, he wrote, and in some cases being deposited via microbialites.

(Image courtesy of Robert Baskin) A satellite image shows dredged material placed near a Union Pacific levee, spreading over dark green-appearing microbialites, according to hydrologist Robert Baskin.

(Image courtesy of Robert Baskin) A satellite image of a marina at Promontory Point of the Great Salt Lake shows dredged sediment spilling into the water and appearing as gray streaks, according to hydrologist Robert Baskin.

Carie Frantz, an associate professor of geochemistry and geobiology at Weber State University who also studies the Great Salt Lake microbialites, agreed that sediments stirred up by dredging are a concern.

“I would expect sediments to move long-term and not stay on top of microbialites forever,” Frantz said. “…But that could take years or decades, and in some cases they may never recover if the sediments are deep enough.”

That’s why the structures in Farmington Bay aren’t forming, she said, even though it has a salinity needed to support them. Any sediment that flows into the lake there from rivers like the Weber and Jordan settles in the bay, suffocating the microbialites before they can form.

“You’ll make three feet of dirt in a year,” Frantz said. “And that’s much, much faster than the microbial growth.”

pollution in the lake bed

Baskin is concerned that the potentially toxic material will also be blown up with the sediment. Mercury has been detected throughout the lake. Its southern end is known for problems with selenium, which weakens bird eggs.

Once these pollutants mix in the water column, they could become bioavailable to brine flies, brine shrimp, and the birds that eat them.

And US magnesium itself has documented the release of PCBs and dioxins that can cause health complications for humans, including cancer, liver damage, reproductive problems, and more.

“They’re going to remobilize the materials that are currently trapped under all the mud,” Baskin said.

Because of this, he suggested that the state support the lake’s mineral extraction industries in other ways, such as offering loans or grants to help them stay in business until the waters rise again.

“The damage that will be done … to the environment and to the people on the Wasatch frontline,” Baskin said, “is far greater than the cost of supporting the mining industry with payments … to get it through these low-level years.” “

Baskin said he has not received a response from the governor since sending his letter. Asked for comment, a Cox spokeswoman said she had not seen Baskin’s feedback. However, the governor’s Public Lands Policy and Coordinating Office scaled back its support for US Magnesium Days after news of the canal expansion proposal broke in September.

This article is published by The Great Salt Lake Collaborative: A Solutions Journalism Initiative, a partnership of news, education and media organizations dedicated to educating readers about the Great Salt Lake.

https://www.sltrib.com/news/environment/2022/12/21/great-salt-lake-expert-explains/ Expansion of US magnesium channels could stir up toxic sediments of the Great Salt Lake

Justin Scacco

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