SOUTH PORTLAND — The City Council informally adopted an update to its Combined Sewer Overflow Facilities Plan, advancing the 12-year, $15.63 million proposal for public comment.
Combined sewer overflow, or CSO, occurs when wet weather overtakes the city’s sewer system, triggering a release of waste water and storm water into the Casco Bay or Fore River.
The Maine Department of Environmental Protection has a policy of reducing CSO, which can lead to water pollution. The problem is often solved through sewer separation, the division of sewage and storm-water runoff systems that prevents CSO.
Before undertaking sewer separation projects, South Portland had 28 CSO points. That number has since dropped to six. The proposal advanced Monday night would eliminate five more.
“In the early ’90s, we were discharging as much as 500 million gallons a year,” said Patrick Cloutier, director of South Portland Water Resource Protection. “Now it’s down to 16 million gallons per year. That’s less than 1 percent of total state discharge.”
The city spent $9 million between 1994 and 2008, when the first draft of the plan revision was written. That money eliminated 18 CSOs. Chris Dwinal, an outside engineer hired by the city, said the revised plan costs more for good reason.
“The ones you got rid of earlier were the easy ones,” he said. “These are harder, that’s why this costs more.”
Dwinal said upgrades to the system would prevent CSOs from up to two-year storm events. Those storms drop 3 inches of rain within 24 hours, and have about a 50 percent chance of occurring any year.
He said he and Water Resource Protection staff chose two-year storms as a cap because preventing CSOs at even bigger storms would have been cost-prohibitive. Mitigating CSOs from 10-year storms could have cost as much as $36 million, he said.
City councilors on Monday praised the plan and the city’s stance toward mitigating CSOs.
“The city is, in my opinion, way far out ahead of most others,” said Councilor Maxine Beecher. “We’ve made a commitment to the environment, and now we’re close to the end.”
City Manager Jim Gailey said most of the funding for CSO mitigation had so far come from the tax increment financing district, or TIF, associated with National Semiconductor. When Texas Instruments bought the company this year, they also signed on to the TIF, which would continue to fund sewer separation.
Now that the plan has been given a preliminary nod by the council, the public has 30 days to comment. After the city addresses public concerns, it can adopt the plan and send it to the Maine Department of Environmental Protection for final approval.