Davenport faces a potential $224 million price tag to repair its leaky and creaky sewer systems and meet state and federal clean water requirements under an Iowa Department of Natural Resources agreement.

Davenport aldermen will vote on a consent order with the DNR at its meeting Wednesday that lays out a timeline of repairs and requirements through 2026.

Although the consent order is for a combined sewer system shared by Davenport, Bettendorf, Riverdale and Panorama Park, Davenport is responsible for almost 80 percent of the system and the cost of repairs.

The consent agreement lists costs of improvements to meet clean water regulations at

$160.4 million, with Davenport responsible for $127.8 million of that. In addition, the city plans $96.7 million in storm and sanitary sewer repairs in capital improvements. The third phase of the westside diversion tunnel is included in the city’s costs.

The first part of that timeline allows the city to investigate, clean systems and design a repair plan between now and 2018. That was important for the city, Public Works director Mike Clarke said.

The most significant cost is an equalization basin that has been estimated at up to $50 million, but repairs could bring down the basin’s size — and cost. The basin would be built near the sewer treatment plant, 2606 S. Concord St., to contain stormwater runoff.

Clarke compares the equalization basin to a large bathtub that would capture stormwater runoff so it doesn’t overwhelm the sanitary sewer system in times of high maximum capacity.

“We know we’ve got a lot of leaks,” Clarke said. “Let’s fix the leaks and then figure out how big the bathtub needs to be.”

The DNR accepts that repairs need to be done to determine the possible size of the basin.

“Depending on how much extra water you can keep out of your system, it can change whether you build a lagoon that is 30 million gallons or 60 million,” said Paul Brandt, a senior environmental specialist for the DNR.

The DNR has similar consent orders with Muscatine and Clinton that stretch out over several years and millions of dollars, Brandt said.

“Like a lot of towns along the Mississippi River, their infrastructure is getting old and deteriorating,” he said. “If you look at places like Clinton and Muscatine, they are going out that far into the future if not further.”

Public Works crews have already begun smoke tests and dye tests to find problems in the city’s 493 miles of sanitary sewer pipe and 152 miles of storm sewer pipe. They’ve discovered completely blocked storm sewers, and sanitary sewer lines that run into storm sewers. They’ve found cracks and collapses. Last year’s River Drive resurfacing project included 29 sewer repairs.

“These are difficult and challenging projects that are complicated by the age of the system dating back to the 1800s,” Clark said. “There are no new technology practices that we have to create, but there are existing engineering challenges we have to solve.”

The consent order also includes the U.S. Army Corps of Engineers. A 54-inch pipe that collects stormwater from above the Corps’ roller dam and releases it into the river below the dam is completely blocked. The Corps has agreed to clear it for the first time since the early 1980s, paid for through available disaster recovery funding.