As Great Salt Lake continues to shrink and its salinity increases, Utah regulators have finalized a new rule to limit how much salt mineral companies can return to the lake when salinity reaches a critical limit.
The rule, developed by the Utah Department of Water Quality in response to 2024’s HB 453, prohibits discharges into Gilbert Bay—the lake’s southern arm—once salinity hits or exceeds 150 grams per liter. That threshold marks a tipping point: scientific research shows that brine shrimp, brine flies, and algae—the foundation of the lake’s food web—struggle to survive above it, threatening millions of migratory birds that rely on them.
Mineral operations, which pump brine from the lake to extract materials like lithium and magnesium, could continue discharging only if they meet one of two exceptions. The first allows de minimis discharges that cause a negligible increase in salinity. The second applies to discharges that result in a net salt reduction—meaning more salt is removed from Gilbert Bay than returned. Both exemptions would require a formal waiver, detailed data submission, and public comment.
As of early 2025, Gilbert Bay’s salinity was about 112 g/L, but that number is expected to rise throughout the summer. With the lake forecasted to drop by 1.5 feet this summer, state modeling predicts salinity could reach between 120 and 129 g/L by the fall, depending on lake conditions.
“We’re seeing greater decline every year as time passes… more and more lake level decline during the evaporation season,” Christine Rumsey, a hydrologist at the U.S. Geological Survey, said in the June Great Salt Lake Salinity Advisory Committee meeting.
The rule, approved in May, will be integrated into Utah’s discharge permitting system. Companies will need to monitor salinity and discharge volume, with permits reviewed and updated every five years to ensure compliance.