EAST PROVIDENCE –– Upgrading the city’s wastewater treatment facility to comply with environmental regulations and handle the potential full build-out of East Providence’s waterfront may cost $70 million.

The total is contained in a plan drafted by experts hired by the city and approved last month by the state Department of Environmental Management. The department has been pressuring the city for years to make the improvements.

The City Council had a workshop April 14 and is expected to approve a 300-plus-page request for proposals at its Tuesday night meeting. Those proposals are to include private management of the sewer system, which would still be owned by the city.

Nonetheless, the cost has council members uneasy.

“I know it’s long overdue, but I have concerns about the price tag,” Councilman Bruce DiTraglia said. He questioned the ability of city residents to handle significant fee increases to cover the project’s cost.

Officials say they expect to get a low-interest loan, to be repaid over 10, 20 or 30 years. Barrington will also pay about 20 percent of the loan because it has its waste purified at the plant.

Mayor Joseph Larisa Jr. agreed, “Our biggest concern is the cost to our ratepayers.”

The mayor said he couldn’t vote for any final agreement to do the work unless the city gets a study showing that even with new fees, they would still be below or at the average for other Rhode Island communities.

Susan Landon of Malcolm Pirnie, the engineering firm hired by the city, said her company will evaluate rates around the state immediately, but approving the request for proposals this month is critical as well.

The Crest Avenue plant in Riverside was built in 1954 and its holding tanks, aerators and other machines purify millions of gallons of sewage that flow into the facility from two-thirds of the city and Barrington each day. (Waste from the rest of the city, primarily Rumford, is handled by Narragansett Bay Commission’s Bucklin Point plant in Pawtucket.) The cleaned wastewater is discharged into the Bay and upper Providence River.

East Providence’s facility received a major upgrade in the 1970s and was considered state-of-the-art then, but as Sean Coffey of Burns & Levison, the legal firm hired to aid the city, said, “This plant was never designed to meet [the DEM’s latest regulation changes].”

In 2006, the DEM called for all plants to have a biological nutrient removal upgrade. The city must reduce by 2012 the amount of nitrate released into Narragansett Bay to 8 parts per million from 12 parts per million. High amounts of nitrate contribute to the death of fish and other marine life. That portion of the project is estimated to cost $33 million.

Other capital improvements include covering the initial sewer treatment process area to control the odor; computerizing the entire treatment process; improving the digestion and sludge storage areas; replacing the Watchemoket Cove pump station to help reduce stormwater overflow. The request for proposals will seek bidders to design, build and operate the new facility. The company that gets the contract would assume construction costs that exceed its original, estimated price and would have to reach a memorandum of understanding with a labor union that represents the city workers at the plant.

The council plans to select a company and execute a contract by the end of December 2009. The city has to submit final design to the DEM by March 1, 2010, and all of the improvements to the plant have to be finished, including showing that the nitrogen levels have dropped, by Sept. 1, 2012. The city hopes to have the Watchemoket Cove pump station and associated pipe improvement constructed by August 2013.

apina@projo.com