Thursday, Sept. 22, 2016 12:09 am
Digging deep on Hunter Lake
Go down 30 feet, Pawnee says
While Pawnee questions the design of Hunter Lake, an engineering firm that has worked for the village questions the need for a 3,000-acre reservoir, which would stretch to the burg south of Springfield.
Mudflats and mosquitoes are Pawnee’s “number one environmental issue,” village attorney John Myers wrote in a Sept. 14 letter to the U.S. Army Corps of Engineers, which must issue a permit and so solicited public comment on the proposed lake.
“The potential for rotting vegetation, odors and insect infestations is obvious, and will significantly degrade the quality of life in the village,” Myers wrote.
One solution, Myers wrote, would involve deepening the southern portion of the proposed lake so that water would stop well short of the village. The lake as designed would have an average depth of less than 15 feet, according to a 16-year-old city plan, half the depth the village says should be considered at the southern end of the proposed reservoir. According to Myers, consultants for Springfield and City Water, Light and Power have considered whether deepening the lake might address potential problems with phosphate pollution.
“Subject to the findings of the ongoing (pollution) study, this problem might well necessitate the southern terminus of the new lake being relocated to New City Road, approximately four miles north of the village, with the new lake being dredged to a depth of 30 feet or so at that location,” Myers wrote.
The pollution study to which Myers refers is part of an effort to obtain a permit from the state Environmental Protection Agency, which must be assured that runoff from surrounding land won’t pollute the lake. Phosphorus is a particular concern, given that excessive levels can trigger algae blooms.
Sanjay Sofa, chief of the Bureau of Water for IEPA, said that he wasn’t familiar with a proposal to deepen the proposed lake as a means of alleviating potential problems with phosphorus and algae blooms. There are many variables, he said, but water depth can play a role, given that algae tends to grow in warm temperatures that can develop in shallow depths.
“I think, in general, shallow depths, they’re more prone to algae blooms than deeper water,” Sofa said.
Ted Meckes, CWLP water division manager, said that the city is aware of the issue.
“The design of the lake has not been fully determined, although digging the entire lake 30 feet deeper would be unrealistic and cost prohibitive,” Meckes worte in an email.
Pawnee “fully supports” relocating the lake so that it doesn’t come anywhere near the village, Myers wrote. The village also suggested widening and dredging Horse Creek, which would be inundated by Hunter Lake, so that a pool of water between five and eight feet deep would be created. And Myers suggested that athletic fields at the school be raised to address flooding concerns; in the past, CWLP has suggested building a berm around the fields.
In a separate letter to the Army Corps of Engineers, which solicited public input on Springfield’s application for a permit, Greene and Bradford, a Springfield engineering firm that has worked as a consulting engineer for Pawnee, said there are better, and cheaper, sources of water for Springfield than Hunter Lake.
CWLP officials have talked about a shortfall of 11 million gallons per day. Considering that the average golf course consumes 300,000 gallons of water per day, more than three million gallons per day could be saved if local golf courses used wastewater effluent for watering, according to the letter from Gary LaForge, a Greene and Bradford engineer.
Beyond conservation, the city should seek water from larger watersheds than the one that feeds Lake Springfield and would supply Hunter Lake, LaForge says in his letter and an interview. The Sangamon River remains untapped, even though it flows at the rate of 24 million gallons a day during dry spells; by contrast, less than a half-million gallons flow through streams that feed Lake Springfield during dry weather, he says. Similarly, LaForge says the city should consider getting water from Salt Creek near Lincoln, where 26 million gallons a day flow during dry conditions.
Horse and Brush creeks, which would feed Hunter Lake, dry up in drought conditions, LaForge says.
“So, the lake that you’re building for a drought condition has no water going into it during a drought,” Laforge said.
Instead of drilling wells near Havana, which the city has billed as an alternative to Hunter Lake, the city should drill near Lincoln and tap into the Mahomet Aquifer, the same underground water supply that would feed Havana-area wells, LaForge wrote.
But George Roadcap, a hydrologist with the Illinois State Water Survey at the University of Illinois, said that the aquifer in the Lincoln area is covered with clay, so it takes longer to recharge than the aquifer near Havana, which is close to the ground surface. If Springfield drew water from wells in the Lincoln area, Roadcap said, that could affect wells that supply water to others.
“There’s quite a bit that needs to be considered,” Roadcap said.
The city should also consider cooperating with water systems that have excess capacity, LaForge wrote. Between the Edinburg, Dawson, Taylorville, the South Sangamon Water Commission and other systems, the region each day can produce as much as four million gallons more than is needed, and Springfield would need just 10 miles of eight-inch pipe to tap in, LaForge says.
LaForge also isn’t convinced that gravel pits near Riverton couldn’t be part of the solution. According to a 2013 study commissioned by the city, the pits could produce 1.6 million gallons of water per day – if more water is taken, wells that supply the South Sangamon Water Commission, Riverton and other communities might go dry. But LaForge said that no one has studied whether there might be sufficient water for everyone if wells for other municipal water systems were drilled deeper.
LaForge agrees that combining options is the best approach.
“We’ve got all kinds of backup systems (in our recommendations),” Laforge said. “They’ve got a dead lake. It’s just a good idea: Diversify.”
Meckes wrote in his email that the Corps of Engineers, which must grant a permit, will look at all options.
“In the past when studied, some of these alternatives would be affected by drought in a similar condition as Springfield, and other alternatives, somewhat more drought tolerant, would not have the additional capacity to supply CWLP the amount of water needed,” Meckes wrote.
Contact Bruce Rushton at email@example.com.