O'Brien Water Reclamation Plant Battery E, Skokie, Illinois

The O’Brien Water Reclamation Plant Battery E project is the largest contract the Metropolitan Water Reclamation District of Greater Chicago has put out to bid, and it’s going into a plant that turns 100 in 2028. Michels Construction holds the $389.9 million contract, which the MWRD board authorized on June 18, 2026. The district broke ground in Skokie on Oct. 8.

Phosphorus is the reason. The plant at 3500 Howard St. treats an average of about 230 million gallons a day for more than 1.3 million people across 143 square miles, and its effluent runs into the North Shore Channel. Illinois EPA phosphorus limits are tightening, and the district wants to hit them by 2027.

Project Scope

Battery E is a fifth activated sludge battery, built to pull phosphorus out biologically instead of relying only on chemical dosing. Bid documents for contract 21-092-3P call for six cast-in-place, two-pass aeration tanks. Each gets two mechanical mixers, an FRP baffle wall, an internal mixed liquor recycle pump and fine-bubble membrane disc diffusers. Downstream sit eight circular final settling tanks, each 112 feet in inside diameter, with sludge collection rake arms, automatic flushing scum removal and perimeter effluent weirs.

That’s a lot of concrete on a tight suburban site.

The new battery also gives the district room to take the four existing batteries offline in turn and upgrade them. That’s the long game here. Battery E isn’t just added capacity. It’s the swing space that makes the rest of the plant’s modernization possible without cutting treatment.

The district’s pre-bid estimate ran from $308 million to $373 million, with bids due Nov. 18, 2025. The award came in about 4.5% above the top of that range. Participation goals are 20% MBE, 10% WBE and 3% VBE. No completion date has been published.

Why It Matters

Nutrient removal is where a growing share of wastewater capital money is going, and the reason is downstream. Phosphorus feeds algal blooms, and the Mississippi basin’s load ends up in the Gulf’s low-oxygen dead zone. MWRD is one of the biggest dischargers in that basin, so other utilities facing their own permit renewals will be watching what this costs and how long it takes.

The price deserves attention. Landing above the engineer’s high number on a contract this large isn’t shocking in the current market for process concrete and mechanical work. But it’s a warning for owners still budgeting nutrient upgrades off older unit costs.

MWRD calls Battery E one of its largest single investments outside the Tunnel and Reservoir Plan. For a district best known for digging Deep Tunnel, that’s a real shift in where the money goes.

Project Team & Details