PROJECT GOALS

• To increase stormwater capacity in Commercial Street (Center St to Maple St) to help mitigate frequent flooding issues being experienced as a result of excessive stormwater runoff and tidal impacts in this area.
• To provide a new storm drain system with 25-year storm capacity that allows for the future combined sewer separation of a 30-acre watershed located in Center Street, Free Street, Spring Street and Pleasant Street in an effort to reduce Combined Sewer Overflows (CSO) into Portland Harbor.
• To provide new tidal backflow prevention valves on the new storm drain system and the adjacent Maple Street CSO line to increase the system’s resilience against tidal impacts

PROJECT OVERVIEW

This project will construct a new 42-inch separated storm drain outfall at the southwestern corner of the City’s Portland Fish Pier property and install approximately 1,000 linear feet of new 42-inch storm drain piping along Commercial Street from Maple Street to Center Street, replacing an undersized 18-inch pipe.

Stormwater in this area currently drains into a limited-capacity combined sewer at Maple Street and Commercial Street, contributing to combined sewer overflows (CSOs) at Long Wharf (CSO #25). The new system, along with the adjacent Maple Street CSO line, will include tidal backwater valves to reduce tidal backflow and improve performance during high tides.

The upgraded storm drain is designed to convey a 25-year storm event from the combined Commercial Street and Center Street watershed. This improvement will allow approximately 30 acres of drainage area to be removed from the combined sewer system, reducing CSO discharges to Casco Bay and relieving stress on the existing combined sewer outfall.

In 2024 the project received received a 3.6 million dollar grant as part of the Maine DOT's Maine Infrastructure adaptation fund. For further information on this grant please visit the following link: https://www.maine.gov/dot/programs-services/environmental-efforts/climate-initiative/adaptation