PORTLAND — The City Council on Monday unanimously approved a $3.1 million expansion to the sewer system on Peaks Island.

The project will provide sewer services to an extra 60 households and 57 vacant lots on Island Avenue and Seashore Avenue.

The expansion will be paid for with a 1.5 percent increase in the city sewer rate, which will be assessed to homeowners’ water bills.

The average homeowner in Portland pays about $460 per year for sewer services, so their bills will increase by about $7 per year, Councilor John Anton said.

Don Doane, a Peaks Island resident who began campaigning for the expansion in 2005 with signed petitions, said the cost of a new septic system on the island can cost individual homeowners $20,000 to $45,000 depending on the amount of rock on the lot.

“When you’re looking at $28,000 versus a small monthly fee, that’s quite a difference,” he said.

Mike Murray, a member of the Peaks Island Advisory Committee, said he polled residents in the affected island developments and they overwhelmingly approved of the expansion. The ones who didn’t approve, he said, mostly didn’t have the finances to connect to the city’s system.

Once the city extends the system, homeowners must still pay a $2,000 connection fee, plus the cost of running the line from their home to the city line. That can cost between $5,000 and $10,000, Councilor Ed Suslovic said.

Peaks Island residents won’t have to connect to the city’s expanded line as long as they have a working septic system. If they don’t have a working system, or when their working one fails, they will have to connect to the city’s system.

Michael Bobinsky, the city’s director of public services, said expanding the sewer system will help protect Casco Bay by limiting runoff from leaky septic systems.

Staff Writer Jason Singer can be contacted at 791-6437 or at: [email protected]