Rates for the city’s utility customers may quadruple over the next 10 years to fund federally mandated sewer improvements.

Middletown projects spending $100 million to $150 million in improvements over the next 20 years, according to Interim Public Works and Utilities Director Preston Combs to meet a U.S. Environmental Protection Agency requirement that communities with combined sewer systems develop a long-term control plan to eliminate, or at least greatly reduce, overflows of that system.

There are 60 to 80 overflows annually of untreated sewer water into the Great Miami River — a body of water the city’s economic development department wants to capitalize on in the future.

“We’re looking at a quadrupling of rates probably within 10 years, that would be a good guess,” Combs said.

In 2011, a city resident using 3,000 cubic feet, or 22,500 gallons, of water per quarter paid $111.15, according to the Oakwood Water and Sewer Rate Study. That rated 28th out of 63 sewer providers evaluated in Southwest Ohio.

Middletown has been working since 2000 to have an approved plan, and the last three — in 2000, 2004 and 2007 — have been rejected, and the last plan was deemed too costly and would have raised rates six-fold, Combs said.

Combined sewer systems are designed to collect rainwater runoff, domestic sewage and industrial wastewater in the same pipe. More than 770 communities, which have a combined population of 40 million, live in a community with combined sewer systems, according to the U.S. EPA.

After the water and wastewater is treated, it’s discharged to a body of water.

However, during heavy rainfall, or when a lot of snow melts, the volume of effluent in a combined sewer system exceeds its capacity causing it to overflow into a nearby body of water, such as the Great Miami River.

The combined systems are found in older communities, mostly located in the Northeast and Great Lakes regions and the Pacific Northwest, according to the U.S. EPA.

The city could face a federal law suit if it refuses to develop and implement a control plan, according to Law Director Les Landen.

“The idea here is to try to negotiate a settlement that everybody can live with,” he said. “But keep in mind, the U.S. EPA’s idea of what you can live with may be different than what we have in our mind of what we should have to live with.”

Combs is recommending City Council contract with Brown and Caldwell, a Cincinnati-based environmental engineering firm, to help develop the plan. The contract, which council will vote on tonight, would be for $565,877. A draft must be submitted to the U.S. EPA by November 2013.

“One of the main goals of this project from an EPA standpoint and a community standpoint is to improve the water quality of the Great Miami River,” said Allen Gelderloos, with Brown and Caldwell.

Combs said any rate hikes would be phased in as planned improvements are scheduled in an U.S. EPA-approved plan. Rate increases will pay off the debt incurred as the city borrows money, he said.

This unfunded mandate will have a “huge impact” on the city’s annual budget, Councilman Josh Laubach said.

“The liability here is on the city. In the mean time while the money is borrowed, it’s going to take years to pay that back,” he said. “This has huge long-term effects on us.”

Mayor Larry Mulligan doesn’t expect much financial relief on the mandate from the federal government, even though the city has made requests to seek that relief. He said the city needs to still attempt to seek financial relief, but “through this negotiation process we can try to get some relief.”