Too much phosphorous in Lake Springfield
Lake Springfield exceeds pollution standards for phosphorous levels, and nitrogen is also an issue, according to a study by a consultant hired to measure pollution levels and propose solutions.
It would cost an estimated $143.5 million to reduce levels of pollutants entering the lake to acceptable levels, the consultant found. Among other things, farming practices should be revised, failing septic tanks should be fixed or replaced, ponds should be created to capture pollution-laden runoff before it can reach the lake and grass should be planted around waterways that convey water to the lake that serves as the city’s source of drinking water.
Money for the study came from City Water, Light and Power and the Illinois Environmental Protection Agency.
By themselves, measures taken in the 169,000-acre watershed would not bring phosphorous levels to acceptable levels, according to preliminary results of the study conducted by Northwater Consulting of Springfield. Thirty percent of the phosphorous found in lake water is coming from sediment already in the lake, the consultant found, and so CWLP should consider dredging the lake. The price tag for addressing pollutants already in the lake is not included in the estimated $143.5 million tab for reducing levels of pollutants entering the lake.
Ted Meckes, CWLP water division manager, said he wasn’t surprised by the consultant’s findings. He noted that the bulk of pollutants are coming from farms, according to the study, and so the biggest improvements lie in reducing the amount of fertilizer used by farmers and changing farming methods. The city is also helping pay to eliminate septic tanks on lakeshore property and hopes to have all homes near the lake connected to sewers within six years or so, he said.
When the city last dredged the lake west of Interstate 55 in the 1980s, CWLP spent $8 million to remove three million cubic yards of sediment, Meckes said. He estimated the same job would cost about $15 million today, and he said the city will likely do it within five to 10 years.
Lake Springfield is not unique, says Jeff Boeckler, senior water specialist with Northwater, which was hired by the Sangamon County Soil and Water Conservation District. Reservoirs that provide drinking water in Illinois almost all exceed the state standard of .05 milligrams of phosphorous per liter of water, he said.
“Virtually every public water supply in the state does not meet that standard,” Boeckler said.
But that doesn’t mean that excessive levels of phosphorus are nothing to worry about. High phosphorous levels can prompt algae blooms that can render water undrinkable. In 2014, a toxic algae bloom fed by phosphorous in Lake Erie poisoned Toledo’s water supply so that tap water was too dangerous to drink for a weekend. Even if algae isn’t harmful to humans, it can remove oxygen from water, which can harm fish. High levels of nitrogen, which, like phosphorous, is found in fertilizer, can also cause health problems, particularly in infants.
The level of phosphorous found in surface water within the watershed between 1999 and 2014 averaged .41 milligrams per liter of water, more than eight times the state standard of .05 milligrams per liter, according to Boeckler’s research. Boeckler said that phosphorous levels within the lake itself also are higher than the state standard. The average concentration of nitrogen was 7.3 milligrams per liter in the watershed; the state standard is 10 milligrams per liter. Meckes and Boeckler agreed that nitrogen levels in the lake are significantly lower, with Meckes putting the level at around two milligrams per liter.
Pollutants can be removed from drinking water, Boeckler said, but there’s a cost.
“If they start consistently getting nitrates over 10 milligrams per liter, they’ll have to build a nitrate treatment facility, which would cost tens of millions of dollars,” Boeckler said. “Phosphorous becomes very difficult to remove after a certain point, and costly.”
To a large extent, cleaning up the lake is a matter of playing catch-up, Boeckler said. When Lake Springfield was created during the 1930s, no one thought about phosphorous or nitrogen, and so pollutants in runoff water poured into the lake, which was able to handle it, but only to a point. The lake acts somewhat like a giant filter, trapping phosphorous in sediment, but as the amount of phosphorous increases, it can be released from sediment through wave action, Boeckler said. It’s difficult to say whether the problem is getting worse over time, he said.
“What we do know is, it’s not meeting the standard, and it’s consistently not meeting the standard, and therefore something needs to be done to improve it,” he said.
Water quality, including phosphorous and nitrogen levels, have long been monitored in the lake, but the Northwater study is an attempt to quantify the amount of pollution caused by farming, septic tanks and other human activity, pinpoint geographic locations where pollutants are coming from and calculate just how much pollution can be kept out of the lake by various methods. The idea is to focus efforts and spend money on projects that will produce the best results.
“Part of the reason the EPA’s funding stuff like this and the reason we funded it is, we want to know what’s going on out there,” Meckes said. “When we spend money, we want to get the best bang for our buck.”
Contact Bruce Rushton at firstname.lastname@example.org.