Bloomington council authorizes $215,000 lake treatment after microcystin detects

The Bloomington City Council on March 24 approved a resolution authorizing a contract to treat planktonic algae in the city’s reservoirs after periodic testing detected microcystin in finished water.

City water staff said the work is intended to reduce cyanotoxin levels, limit taste-and-odor complaints, and prevent a public-health exceedance while the Illinois Environmental Protection Agency (IEPA) continues directed monitoring. The council approved the agreement to hire NorthWater Consulting and aquatic controls partners for an estimated $215,000; the vote was moved by Council Member Ward and seconded by Council Member Hendricks and passed by the council.

Bloomington Water Director Ed Andrews told the council the city has been monitoring microcystin weekly with IEPA’s lab in Springfield and that the first finished-water detect occurred in early March. "We had our first detect in finished water at 0.042 micrograms, which is 14% of the initial regulatory limit," Andrews said, and reported that a subsequent finished-water result rose to about 23% of the limit. Andrews said the IEPA has directed the city to pump from Lake Evergreen while levels are addressed.

Andrews described the chosen treatment as Cutrin Plus applied from a GPS-controlled boat with draped injection lines and metered applications to avoid excessive disruption of the lake. He said the city considered copper sulfate and other approaches, interviewed three firms and selected an operator with published experience. The IEPA algaecide permit for the specific application was approved on March 20, city staff said.

On timing and expected results, Andrews told council members the initial treatment is expected to show effect within about five to seven days, and the program budget includes multiple rounds of treatment. He also noted the city has added powdered activated carbon (PAC) to its plant operations; PAC has increased removal efficiency at the filters, and the city is installing an in-house testing unit to shorten lab turnaround from roughly a week to days.

Council members asked about causes and risks. Andrews attributed the bloom to a confluence of conditions including a warm, low-snow winter, seasonal turnover and low inflow; he said researchers from the University of Wisconsin described similar dynamics. On risks, Andrews said the applied treatment is a targeted, limited-dose approach managed by certified staff and consultants. A city lake manager and vendor will monitor the response and coordinate closely with IEPA.

The council did not record a roll-call tally in the public record beyond the motion and second; staff said the motion passed. Following the vote, the water department planned a technical coordination meeting with the vendor and IEPA and committed to weekly public reporting of finished-water and distribution sampling results.

Clarifying details: staff reported a recent finished-water microcystin detect of 0.042 µg/L (14% of the referenced regulatory limit) and a later weekly finished-water result representing roughly 23% of the limit; Evergreen lake MIB taste-and-odor values and finished-water MIB values were cited in briefings but vary by lab. The city said it will continue pumping from Lake Evergreen while Bloomington reservoir microcystin levels remain comparatively higher.

The council directed staff to proceed with the negotiated agreement and to keep the council and public informed of test results and next steps.