PORTLAND, Maine — A proposal to charge Portland property owners a monthly fee to pay for future storm- and wastewater infrastructure improvements will get two public hearings in the next month.

The proposed ordinance, now in front of the City Council finance committee, will first be open for comments at 6 p.m. Thursday, Oct. 23, at Deering High School, 370 Stevens Ave.

A second hearing likely will be held in City Council chambers at 6 p.m. Nov. 13. Councilor Nick Mavodones Jr., the finance committee chairman, last week said the committee could then forward the plan for full City Council deliberation.

If the Nov. 13 hearing draws a large crowd, Mavodones said the committee vote to forward the ordinance to the full City Council would come at a second committee meeting next month.

The amendment to the city code would initially assess all public and private property owners a monthly fee of $6 per 1,200 square feet of impervious surface beginning in early 2016. Roofs, driveways and sidewalks are considered impervious surfaces.

The fees are intended to fund a portion of the current $15 million to $20 million annual cost to upgrade and maintain city storm- and wastewater infrastructure. The costs are projected by city officials to reach $60 million by 2030.

The new fee, which exempts roads, railroads and properties smaller than 400 square feet, would be accompanied by a reduction of $1.50 per hundred cubic feet in the city sewer fees to $8.20. However, the stormwater fee is projected to increase to $8.20 per 1,200 square feet by 2019 in the presentation committee members viewed.

All city islands except Peaks Island would be exempt from the fees.

Efforts to bring the city into compliance with federal and state clean-water regulations, which began when city officials signed a consent agreement in 1991, have entered a third phase.

Future projects include replacing 20 miles of sewer pipes carrying storm- and wastewater, expanding storage capacity for waste- and stormwater by 15 million gallons, and improving catch basins that collect runoff. City Public Services Director Mike Bobinsky said stormwater also will be treated at collection sites before it enters waterways.

Plans call for ending overflows of wastewater in Casco Bay by diverting stormwater that flows to the Portland Water District treatment plant at East End Beach.

During severe storms, the flow of waste- and stormwater can inundate treatment systems, though the combined overflow has been reduced by 42 percent since reaching 800 million gallons annually in 1993.

The data was presented on cleangrowthcleanwater.com, where owners can also look up how many “billing units” of 1,200 square feet their properties will be assessed.

Bobinsky said last week the new plan will be more equitable to property owners because sewer fees are charged only to property owners getting water from the Portland Water District.

“This current method of charging is not equitable in terms of the effects these properties have on the system,” he said. The new fee would be assessed by the city, not PWD, and would not appear on PWD sewer bills.

Last week’s finance committee meeting was intended to be the first public hearing on the plan, developed by a task force led by Councilor Ed Suslovic in 2011.

The meeting was attended by four people, leading to the decision by Mavodones, Suslovic and Councilors Jill Duson and David Marshall to hold a hearing next month.

“I’m deeply troubled we have not done public outreach to let people know they could hear this,” Suslovic said.

The committee instructed Bobinsky and Ian Houseal, the assistant to acting City Manager Sheila Hill-Christian, to send information about the plan and hearings to all city property owners “as soon as possible.”

If forwarded to the City Council, the new fees would be subject to another public hearing. Should the plan be enacted by councilors, property owners would receive a sample bill next summer and would be able to meet with city staff in September 2015.

Square footage of impervious surface will be measured using aerial photography. Business and residential property owners could obtain fee credits by installing control devices such as cisterns, rain gardens or detention ponds.