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Bloomington reviews dredging, Mahomet Aquifer and Illinois River as potential supplemental water sources
Summary
City water staff and consultants presented a draft technical summary that outlines three main options to bolster Bloomington—lear water supply — dredging reservoirs, developing the Mahomet Aquifer, and building an Illinois River intake — and recommended updating the city—lear safe-yield estimate before major capital commitments.
City water staff and consultants told the Bloomington City Council Committee of the Whole on June 16 that the city should update its safe-yield estimate and evaluate three principal options for supplemental water: dredging the reservoirs, tapping the Mahomet Aquifer, or building an Illinois River intake.
"Long before the drought of last year, we have been studying what our future water source is going to look like," City Manager Jurgens said as he introduced the staff presentation. Brett Lushin, the city's director of water, reviewed current sources — Lake Bloomington, Evergreen Lake and the Mackinac pumping-pool intake — and noted the plant's rated capacity is 24.5 million gallons per day (gpd) against an average-day use of roughly 10 million gpd.
Bob Cole Hayes of consulting firm Farnsworth, who led the technical review, said safe-yield calculations are statistical and depend on monitoring. "Using a 2009 report from Illinois State Water Survey, the same fields would be 12,000,000 12,700,000 gallons a day," he said, and recommended re-running an updated safe-yield analysis with modern flow monitoring and modeling before committing to large capital projects.
The presentation summarized planning-level estimates and trade-offs for three primary approaches: dredging reservoirs, developing groundwater from the Mahomet Aquifer, and a long-distance surface-water option from the Illinois River.
- Dredging: An updated 2024 bathymetric survey suggests Evergreen Lake could gain about 101 million gallons of storage (roughly six to ten days of drought supply at drought-yield rates), while Lake Bloomington could yield up to about 600 million gallons (approximately 40 to 60 days). The presentation included a rough cost range for dredging Lake Bloomington of about $39 million to $51 million. Consultants stressed dredging could be staged and that it also can benefit water quality.
- Mahomet Aquifer (groundwater): Prior regional studies indicate the Mahomet Aquifer could be developed incrementally and might supply on the order of tens of millions of gallons per day at full build-out (presentations referenced modeling results around 37,000,000 gpd). Staff warned that the larger costs are often for pipeline and transmission to link wellfields to the treatment facility.
- Illinois River (surface water): The Illinois River option would likely require an intake, long transmission routing and significant regulatory review by agencies such as the U.S. Army Corps and the Illinois Department of Natural Resources; presenters listed a high-level planning estimate near $175 million but emphasized that figure needs detailed study and could increase.
Consultants and staff emphasized that the options are not mutually exclusive and that a multigenerational program of investments and system improvements — including continued meter replacements and leak detection — is the prudent path. The presenters recommended the council approve a proposal in the coming months to update the city's safe-yield estimate and to continue feasibility work on the options.
The council did not take any final action on a specific project at the meeting; presenters said staff would bring a formal proposal to fund a safe-yield update for council consideration in the next few months.
