The EPA wanted a $1 billion solution for Evansville, Indiana’s CSO problem. In the end, utility leaders came to an agreement with the agency on a fix that was a little more than half that cost.

But getting the EPA to buy in to the lower-cost plan, which included constructed wetlands, over the more costly deep tunnel approach wasn’t easy. According to Evansville director of utilities Allen Mounts, it took nearly four years of meetings and negotiations with the EPA before an agreement was reached.

“There was a lot of back and forth,” he says. “The EPA asked us to compile an unbelievable amount of data, from engineering reports to modeling studies. We submitted 23 exhibits. The complexity of the data and the turnover in EPA staff were especially challenging.”

A $1 billion deep tunnel to collect overflow water would’ve brought CSOs in Evansville from 50 per year to zero. The constructed wetlands are part of a $729 million investment over 24 1/2 years that won’t quite meet that threshold, but it will still reduce CSOs to four per year and increase CSO capture rates to 98 percent. The nearly as effective approach at considerably less expense was the reason Evansville pushed for the EPA to accept its alternative solution.

“We simply couldn’t afford it,” Mounts says of the $1 billion tunnel. “But it was a little like having a Chihuahua in a fight with the lions. We negotiated with EPA at the regional and headquarters levels, arguing facts back and forth. We met in Chicago and in Indianapolis. But we weren’t making progress.”

So the utility called on Evansville Mayor Lloyd Winnecke and the Indiana Department of Environmental Management. Mounts says the mayor and the state helped convince the EPA that Evansville’s CSO plan, including what is thought to be the country’s largest constructed wetlands, would do the trick at a cost the utility and its ratepayers could afford.

"Getting the mayor and the state involved finally gave us the momentum to get things resolved," Mounts says. “We made our business case and said we couldn’t afford what we were asked to do.”

The wetlands are expected to be complete some time in 2023.  Measuring 24 acres, they will have the capacity to treat up to 42 mgd of overflow that will be settled, then “polished” with plants like bulrushes, sedges and prairie grass which take up pollutants and filter out metals.

The overall $729 million CSO control plan also includes cleaning up and reducing the size of an unsightly slough that holds CSO now, upgrading wastewater treatment plants, building green infrastructure to control stormwater, as well as numerous sewer and pumping station projects.

“We’re thankful that EPA worked with us to develop a mutually beneficial plan,” Mayor Winnecke said in a press release at the time. “After years of negotiation, we reached an agreement that’s great for our environment and less financially burdensome to the residents of Evansville than what the federal government proposed.”

Read more about Evansville’s CSO control plan in this story featured in the April issue of Municipal Sewer & Water magazine.