Warning: Mahomet Aquifer water supply has limits

Warning: Mahomet Aquifer water supply has limits

CHAMPAIGN – A proposed ethanol plant in northwest Champaign will take up roughly 10 percent of the remaining local capacity of the Mahomet Aquifer, and Champaign County officials need to start thinking now about future water use, the chief of the Illinois State Water Survey is warning.

Derek Winstanley, chief of the Champaign-based water survey, wrote in an Oct. 27 letter to the city of Champaign that the aquifer can safely support about 16 million or 17 million gallons a day of additional local withdrawal. Current local water usage from the aquifer is 30 million gallons a day.

After the 46 million- to 47 million-gallon-per-day level is reached, the aquifer will start to become depleted, "a potentially serious situation that we advise be avoided," he wrote.

"Once you start dewatering the aquifer, you can get into problems with water quality, you can damage water pumps and have problems with the aquifer itself," Winstanley said. "We don't want to do that. It's not a good idea."

The proposed ethanol plant, which would be built near The Andersons grain elevator complex at Staley Road and U.S. 150, would use an additional 1.8 million gallons a day, taking up roughly 10 percent of the aquifer's remaining capacity.

The Champaign council on Tuesday approved 6-3 an annexation agreement with The Andersons to bring the plant, if it's built, within city boundaries. The Andersons is expected to make a decision about whether to build the plant this winter, possibly by as soon as mid-December.

Winstanley's letter, which was not mentioned during council debate, represents something of a sea change in that it is a stark warning that the Mahomet Aquifer in this area is not a limitless supply of water. He makes reference to that fact in the letter itself.

"The above analysis is, I believe, the first time that a finite capacity to withdraw water from the aquifers in Champaign County has been articulated, so it is not surprising that there has been no discussion about the allocation of limited assets," he wrote.

Winstanley stressed that the water survey is not taking a position on the ethanol plant, merely trying to inform decision-makers and the public about "our current understanding of the aquifers, future water availability, and water demand."

He also refers to the much smaller Glasford Aquifer in the letter, which he said already is dewatered within the city of Champaign.

"We need to get people to look at the longer term and cumulative impact of projects," he said.

The calculations about the capacity of the Mahomet Aquifer are largely based on 50 years of data from a well on Rising Road west of Champaign, Winstanley said. The "head" or water level in the well has declined almost 50 feet in 50 years, to its current level of about 50 feet.

The ethanol plant is expected to cause the level to drop another 3 feet, he wrote. Illinois American Water's west well-field, consisting of 14 high-capacity wells, is relatively close to The Andersons facility, with the closest well one mile to the south of the grain facility.

During council debate this past week, council member Michael La Due cited figures for the Mahomet Aquifer that are on the water survey's Web site, indicating that the entire aquifer – which stretches from Indiana across a 15-county area in Central Illinois – has the ability to safely provide 400 million gallons of water a day, while current usage is about 90 million gallons a day.

Those facts are correct but misleading, Winstanley said. The ability of the Mahomet Aquifer to recharge itself is limited in Champaign County because of the heavy soil and clay in this area. In the western parts of the aquifer, in Tazewell and McLean counties, the aquifer recharges quickly because of sandy soil, he said.

"Although the potential sustainable yield of the entire aquifer is large, water withdrawals in Champaign County already have created a large cone of depression (a lowering of the water table in the aquifer) and reversed the east-to-west flow of groundwater," Winstanley wrote. "Champaign County is a 'hot spot' in need of management attention."

Champaign Mayor Jerry Schweighart, when told of Winstanley's concerns, said: "I hadn't heard that. It is a little more alarming than what else has been said about it."

Council member Marci Dodds, who voted against The Andersons annexation agreement, said she read Winstanley's letter beforehand and that it "troubled me tremendously.

"I have lived in places where water is restricted," Dodds said. "It is not fun to only be able to run your dishwasher on certain days or not to be able to water your lawn."

Dodds said the city, which would provide 10 years of property tax abatements for the ethanol plant, is getting very little benefit in comparison to the resources that will be used.

She is concerned about other potential industrial projects in the area that would be heavy water users, including a possible ethanol plant near Royal and the proposed FutureGen plant, which is looking at sites near Tuscola and Mattoon as well as two sites in Texas.

Meanwhile, Gov. Rod Blagojevich issued an executive order in January that the state should start regional water supply planning. The studies are to be done by the water survey and the Illinois Office of Water Resources, with the Mahomet Aquifer and northeast Illinois to be studied first. Those studies are to be completed by January 2009, and some funding has been committed, Winstanley said.

The Mahomet Aquifer Consortium, a local planning group, has convened and will help the state agencies formulate findings.

"The process is now in place for regional water supply planning, for the first time ever" in Illinois, Winstanley said. "I think we're making great progress."

The Illinois State Water Survey is a division of the Office of Scientific Research and Analysis of the Illinois Department of Natural Resources and an affiliated agency of the University of Illinois. It is the primary agency in Illinois concerned with water and atmospheric resources.

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