$15.6M sewer proposal eyed

SOUTH PORTLAND — The South Portland City Council gave its provisional nod Monday to a $15.6 million plan to limit the flow of sewage into Casco Bay using a 12-step process of annual projects though 2021.

The next step is for the council to call a public hearing on the plan, which will trigger a 30-day comment period, after which the state Department of Environmental Protection will review the plan for state approval.

The plan, developed by Wight-Pierce Engineering, of Portland, aims to further cut the number of Combined Sewer Overflow (CSO) discharge pipes in the city. This pipes collect sewage and stormwater runoff, dumping the combined effluent out to sea whenever sudden volume from storms threatens to overflow the system, which includes 172 miles of pipe feeding 6,400 manholes and catch basins via 30 pump stations.

In 1987, there were 28 CSOs in South Portland, discharging 500 million gallons of combined overflow into Casco Bay each year.  Today, thanks construction of the treatment plant on Waterman Drive and efforts to remove stormwater runoff from the sewers, there are only six CSOs, discharging about 16 million gallons of overflow, about 1 percent of all such discharge in the state.

The first CSO master plan was approved in 1994 and the city spend $9 million between then and 2008 to limit overflow.

The new plan envisions a system designed to handle a so-called two-year storm (the 50 percent chance of a storm with three inches of rainfall in any given year) without overflowing the system at all in five of the six remaining CSO. The Elm Street CSO doesn’t count at this point, according to engineer, Chris Dwinal, because of its place at the end of the pipeline, at the lowest elevation.

Three phases in the 12-step plan are already completed, or underway, including the $5.3 million upgrade to the Long Creek pump station, and the $256,0000 first phase of project to remove stormwater from sewer pipes in Knightville.

That project will wrap next year at an estimated cost of $837,000. Then comes a similar $1.25 million project in Cash Corner for 2014, completing of that project at a cost of $1 million in 2015, a $1.5 million capacity increase pipes in the Evans Street and Broadway area in 2016, another $1 million separation project for Cash Corner in 2017, a $500,000 capacity hike to the Front Street region in 2018, construction of a $1.5 million pump station and screening system at Front Street in 2020.

Dwinal said that if all the work were to be done in a single year, it would force an 18 percent rate increase. However, by phasing in the projects, city officials hope to mitigate price hikes.