The city of Lawrence and the Environmental Protection Agency have been involved in a quiet four-year debate about the adequacy of the city’s lone sewage treatment plant.

The debate is poised to draw a bit more attention.

City leaders are pointing to their dispute with the EPA as a reason city commissioners should seriously consider a five-year plan to raise water and sewer rates by about 28 percent.

“We run the risk of having the federal government insert itself into our operations and planning,” City Manager David Corliss said of a possible outcome if the city doesn’t raise its sewer rates. “I think most communities have found that to be more expensive than just making the improvements on their own.”

At issue is a dispute that has received little, if any, public discussion at City Hall: The city’s sewage treatment plant technically doesn’t have a current operating permit from the state of Kansas.

Since 2008, the EPA has objected to the renewal of the city’s National Pollution Discharge Elimination Permit on the grounds that the plant, at 1400 E. Eighth St., has illegal sewage discharges during heavy rainstorms.

The city is confident that is not the case. It treats the excess stormwater that infiltrates the city’s sewer pipes with a product called Actiflo.

“It does an excellent job of treating it,” said city utility director Dave Wagner, who stressed the city has seen no evidence that raw sewage is being allowed to bypass the plant and flow directly into the Kansas River during storm conditions.

The city, however, is not so confident that the EPA ultimately will see it that way. In a report to city commissioners, city staff members said there are “no clear answers or direction” about how the EPA may resolve the long-standing dispute.

That may end up being a worry for Lawrence ratepayers. The EPA has mandated wet weather improvements in other nearby communities, which has forced those cities to add a special surcharge onto their monthly sewer bills to pay for the ordered improvements.

Residents in Independence, Mo., for example, will have a $9 per month surcharge added to their bills by 2014, and Kansas City, Mo., has been ordered by the EPA to make $2.4 billion worth of wet weather improvements to its sewage system.

“We think that is a possibility, but we don’t think it is a likelihood,” Corliss said of the city eventually being ordered to make improvements by the EPA. “We believe that’s the case because we’re recommending steps to prevent that type of action.”

Those steps, however, involve five years’ worth of rate increases. A new report to city commissioners that would increase rates for a typical residential user by 28.6 percent between now and 2017. The combined water and sewer bill for a typical 4,000 gallon residential user would increase from $47.64 per month currently to $61.30 by 2017.

At the center of the plan is a new sewage treatment plant that would be built on city-owned property south of the Wakarusa River, near the eastern edge of the city. The plant and it is piping system is expected to cost about $65 million.

City officials long have been discussing plans for a new plant, but they mainly have focused on the need for the city to have a second sewage treatment plant to keep up with future growth.

As the city’s population growth has slowed, city commissioners have delayed starting the expensive project. But now city staff members are highlighting the critical role the new plant will play to help alleviate the wet weather problems at the existing plant.

Wagner said the city will reroute much of its existing sewer system to the new plant, which will reduce the size of the wet weather overflows. Currently, there are times that the city’s plant will take on 81 million gallons of stormwater and sewage during a storm, even though the plant has a design capacity of just 65 million gallons per day.

Such an event is usually considered a 10-year storm, and Wagner said it puts tremendous pressure on the plant.

“It is like going 120 miles an hour down a hill in a Volkswagen bug,” Wagner said. “You can manage to do it, but you don’t want to do it very often.”

The city’s plan to reduce wet weather problems also calls for about $14 million worth of work to better seal existing sewer pipes in order to reduce the amount of stormwater that seeps into the pipes.

The recommended rate increases aren’t entirely for sewer projects. City staff members are pointing to several major projects that need to be undertaken for the city’s water system. They include:

• Nearly $4 million to replace the two water tanks atop Mount Oread, which Corliss has nicknamed “Ike” and “Hoover” because one tank was built during the Hoover administration and the other was built during the Eisenhower administration.

• $7.8 million to extend a new main water supply line across the Kansas River into North Lawrence. North Lawrence’s water supply currently relies on a single water line that runs beneath the Kansas River bridge.

• $4.7 million to make improvements to a faulty water intake at the Kaw Water Treatment Plant, one of the city’s two water plants.

“If you talk to a water plant operator, the No. 1 thing they want fixed is that water plant intake,” Wagner said. “We think that is our No. 1 threat to providing water on a reliable basis.

“We’re lucky to have the Clinton plant that can provide all the drinking water we need, but if we lost the Kaw Plant, everybody would have to stop watering their lawns and everything else.”