Ready water source under Storm Lake rife with sulfate

May 09, 2023

By [email protected] | on May 19, 2023

Water for drinking, agriculture, and industry in Iowa largely comes from various aquifers within the state. The aquifer mapping application allows users to click any location in Iowa and view the bedrock aquifers available in that area. (Map courtesy of the University of Iowa)

The Jordan Aquifer's sulfate levels under the Storm Lake area are over four times the Environmental Protection Agency's suggested limit, further complicating use of the water source that's viewed as critical for municipalities and industrial developers.

The aquifer's sulfate levels east of Fort Dodge and north of Hwy. 20 register around 1,100 parts per million, according to Greg Brennan, a hydrogeologist with the University of Iowa's College of Engineering. The EPA recommends, but doesn't strictly enforce, sulfate limits in finished drinking water below 250 parts per million. Concentrations above that standard are known to make water taste saltier and are suspected to cause diarrhea.

"Water in the Jordan is plentiful. Quantity isn't a problem," Brennan said over the phone last week. "In terms of (contaminants), it isn't a problem or it might be a problem, depending how you see it."

For Platinum Crush, heightened sulfate levels in the Jordan Aquifer forced the company to build a 19-mile water line that runs from its facility south of Lake Creek Country Club to the Raccoon River near the intersection of Hwy. 7 and M-50. Officials with the soybean crush plant recently learned that its wastewater effluent contained sulfate levels that were too high to discharge into their preferred water source, the Little Maple west of Alta. Essentially there wasn't enough flow in the Little Maple to dilute the plant's effluent, around 160,000 gallons per day.

The company is expected to draw and recycle up to 430,000 gallons from the Jordan every day, meaning its effluent will contain sulfate concentrations even greater than the water that currently sits in the aquifer. The Iowa DNR hasn't specified the plant's expected sulfate concentrations. A construction permit is under review by the DNR's wastewater engineering bureau.

Brennan said "there isn't an easy answer" to why the Jordan's sulfate concentrations are especially high in Northwest Iowa. Sulfates are ever-present in aquifers, depending on the surrounding geology and their deepness below ground. Buena Vista County Engineer Bret Wilkinson attributed the increased sulfate concentrations to the Jordan's relative deepness under Northwest Iowa. The aquifer is marginally deeper under Northwest Iowa than it sits in neighboring regions, which means the compound accumulates in greater amounts the lower the aquifer sits.

Sulfate concentrations will no doubt create a headache for industrial developers that need as much water as Platinum Crush and don't have the wastewater plant willing to take the effluent.

There isn't enough local capacity in the Dakota Aquifer to accommodate a developer that needs as much water as the soybean crush plant. Storm Lake, Alta and a host of industrial livestock users have tapped much of the aquifer's capacity, according to ISG.

The Jordan Aquifer is the only resource that's plentiful enough for a large industrial user, a prospect local economic development authorities and area municipalities want to lure. It's even a top priority for Storm Lake, which is eyeing additional water capacity for industrial developers. In 2020, Iowa Lakes Corridor was eyeing an acquisition of property near the Storm Lake Industrial Park to facilitate the expansion.

The problem, as Wilkinson explained it, was that municipal wastewater plants can't take effluent like Platinum Crush's because it doesn't have enough organic material to keep the wastewater plant's organic digesters alive. And there's only one river with enough flow to dilute the sulfate: the Raccoon, the subject of the Des Moines Water Works lawsuit of 2015. (The Little Maple River and Storm Lake don't have flows that are sufficient to dilute the crush plant's effluent. Storm Lake was also mulled as an option for the plant's discharge, but it was summarily denied, according to city officials.)

Essentially Buena Vista County sits at the head of two rivers where flows are weakest. Pollutants like sulfate or nitrate aren't easily diluted under low flows.

Julie Sievers, a senior water solutions specialist with the consulting firm ISG, believes the problem will be especially acute with water-hungry industries seeking to use the Jordan. The aquifer's sulfate concentrations underneath Northwest Iowa are over five times the EPA's suggested limit and it's the only source that's plentiful enough to serve an industrial user here.

Removing the sulfates would cost millions. Transporting the effluent to the Raccoon, as evidenced by Platinum Crush, will also cost millions and requires approval by a political subdivision. In Platinum Crush's case, it's the Buena Vista County Board of Supervisors, which was sued in 2015 by Des Moines Water Works over nitrate pollution.

Sievers noted that some cities in Northwest Iowa have found a way to use the Jordan, despite high sulfate concentrations. Estherville and Odebolt rely exclusively on the Jordan. But those communities have established wastewater infrastructure that can emit effluent that complies with DNR regulations.

In the case of new industry, it could much like Platinum Crush and other ethanol plants in Northwest Iowa. It would either need to store its water on site, like Valero Renewable Fuels’ plant in Hartley, or reroute its effluent like Poet Bioprocessing in Arthur. The Hartley ethanol plant maintains six storage lagoons that discharge in the summer; the Arthur ethanol plant's effluent runs nearly 10 miles to Ida Grove.

"It's a case-by-case basis, but it's an open question: what do you do with the concentrated compounds?" Sievers said. "Any time a utility is looking to establish a water use, or some sort of plant business. They need to have the water resources and wastewater disposal options available."

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