Water worries

Future demand raises shortage concerns in Coralville, Marion

Water filters through one of the two 40 foot. tanks at the water treatment plant in Coralville. (Nikole Hanna/The Gazette)
Water filters through one of the two 40 foot. tanks at the water treatment plant in Coralville. (Nikole Hanna/The Gazette)

Iowa doesn’t have water shortages like in western and southern states, but state and local officials say it’s not a given that will always be the case.

That’s why planning needs to happen now to ensure water continues to flow to homes, farms, factories and others, they said.

Iowa is a water-rich state, but “locally, we do have potential issues,” said Mike Gannon, a geologist with the Iowa Department of Natural Resources.

He’s the co-author of a recent report on the Silurian aquifer, a source of groundwater for many communities in Eastern Iowa.

It’s the fifth in a series of studies of aquifers ordered by the Iowa Legislature. The report says increased demands “by agriculture, industries, and municipalities have raised concerns about the future availability of groundwater in Iowa.”

The DNR took a more detailed look at Coralville and Marion, at the request of city officials who are interested in adding more wells that would tap into the Silurian aquifer to get water to their growing populations.

Coralville was warned it may need to limit its future withdrawal from the Silurian aquifer and look for other water sources. In Marion, there’s concern new wells could disturb an underground contamination plume.

An aquifer is water-bearing rock or sediment from which groundwater can be extracted. “Silurian” is the geologic age of this particular aquifer, 417 million to 443 million years old.

Coralville, which gets about 30 percent of its water from the Silurian aquifer, would like to add two new Silurian wells to its two active ones.

Spreading the pumping around would lessen the drop in water levels, Gannon said. New wells also would help the city meet demand during high-use periods if other wells are out of service, said Kevin Callahan, Coralville’s water plant superintendent.

The wells could be ready in a year and a half, Callahan said. The cost is hard to estimate at this point, he said, but it may be $350,000 to $500,000 a well.

The DNR report said if the daily pumping of Coralville’s wells increase 3 percent a year, reflecting the city’s population growth, the water level in the aquifer could drop more than two dozen feet at the existing wells and a few dozen feet near the proposed wells.

That could harm the production rate and water quality of the Silurian aquifer and Coralville may need to limit its future withdrawal and should evaluate alternative water sources, according to the report.

Callahan said other possibilities are shallower aquifers or buying water from another provider, which would be a last resort.

Iowa City is aware of the limitations of the aquifers and gets most of its water from the Iowa River, Public Works Director Rick Fosse said. Cedar Rapids’ water comes from wells in a sedimentary matter associated with the Cedar River.

Gannon and Callahan both said Coralville is in no immediate danger of running out of water, but they agreed it’s an issue that needs to be addressed.

“It’s something that we’re aware of that, down the line, we’re going to have to look at,” Callahan said.

Like Coralville, Marion’s population is growing. Marion gets nearly all of its water from a different aquifer, the Cambrian-Ordovician, more commonly called the Jordan.

State law prohibits the water level in the Jordan aquifer from dropping below 200 feet, and Marion is pushing up against that. The DNR also is reducing how much water Marion can draw from the Jordan aquifer.

The city will complete a new Jordan well this spring, which should give the city plenty of water for 10 to 15 years, said Todd Steigerwaldt, general manager of Marion’s water department.

The city is considering adding three to five Silurian wells to increase water supply capacity.

The effect of these new wells on the Ralston hazardous waste site on Blairs Ferry Road NE will need to be evaluated, the DNR report said. That’s where Rockwell Collins, in the early days of the company, dumped hazardous waste, and there is now a contamination plume underground there.

The Ralston site is not an issue now, but a high-capacity well could create an area of depression that causes groundwater near the plume to move toward city wells, pulling the plume with it, said Gannon.

Steigerwaldt’s biggest concern is long-term use of the Silurian and Jordan aquifers.

A 2009 report said increased use had led to a significant loss of pressure and volume in the Jordan aquifer, which is the state’s most productive source of groundwater. Ethanol plants and geothermal heating and cooling systems were an increasing demand on the aquifer.

Water is a precious commodity, even if people take it for granted, Steigerwaldt said.“Eastern Iowa, as a whole, should be concerned,” he said. 

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