Preventing raw sewage from flowing into area rivers might be the right thing to do, but it will not be cheap for City Utilities sewer customers.

Mayor Tom Henry on Tuesday announced a plan to nearly double sewer rates over the next four years to help pay for the city’s federally mandated $240 million sewer-improvement program.

Henry said he understood the difficulty posed by raising rates while the economy founders but said not making the improvements would further hurt the local economy and result in federal penalties.

If the city fails to do the work on the approved schedule, it would face fines from the U.S. Environmental Protection Agency.

“Protecting our rivers is the right thing to do,” Henry said.

The proposal, if approved by the City Council, would increase rates 86 percent by 2013. The first increase, set for July, will raise bills 22.5 percent, which customers will see on August statements.

The average residential customer, who uses 5,000 gallons of water a month, would pay $4.28 more each month under the first increase, $16.30 more a month in 2013.

The increase is to be introduced to the council next week and could be passed by the end of the month. Future annual rate increases are expected to begin each July. Currently, the city dumps more than 1 billion gallons of untreated stormwater and raw sewage into the three area rivers. This happens about 70 times a year when rain floods the city’s older combined sewer system, forcing the excessive mixture of rain and sewage into the rivers.

This year’s heavy rains have already caused sewers to overflow into the rivers more than 50 times, Henry said.

Health officials Tuesday said the pollution can harm fish and other wildlife.

The sewer-improvement plan would decrease the amount of sewage dumped into the rivers by 90 percent through several projects.

The city will spend $61 million to separate storm and sanitary sewers, reducing the likelihood of sewage backups in homes. It will also spend $53 million to improve the sewer plant, including increasing its capacity from 60 million gallons a day to 85 million.

The program includes an education component. The city has started a rain-garden program to encourage residents to create gardens that capture rainwater and prevent it from entering the sewer system.

Kumar Menon, director of City Utilities, said the city will also work with sewer customers – including large industries and private residents – to discuss ways to reduce sewer bills. The city charges sewer rates based on water used by each customer, so the city will try to help cut consumption.

While this would reduce revenues, Menon said, it would also cut costs, so the city would benefit as well.

The rate proposal does not affect Aqua Indiana customers because it is based only on sewer charges.

The city received a $1.5 million grant to help with the work, but Menon said it has been difficult to qualify for grants because the city is told its rates are too low compared with other areas of the country.

Councilwoman Liz Brown, R-at large, was on the clean rivers task force commissioned to examine ways to pay for the projects. Although rate increases are necessary, she said, the group will continue to look for alternative funding sources.

The group’s report supported the creation of a local sales tax to help finance the work, but the tax would require permission from the state legislature.

Menon said that announcing the upcoming series of annual rate increases now will allow people to plan ahead.

But he cautioned it would not be the last increase needed to finance the largest public-works project in the city’s history. He said the city would likely unveil a new rate plan every five years.

The city previously said rates could eventually triple to pay for the work.

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