Portland, Maine, CSO Storage Facilities Designed Around Rising Sea Level and Extreme Storm Events

The City of Portland, Maine, has been working under a Consent Decree to control the discharge from combined sewer overflows (CSOs) into its receiving waters for over twenty years. It is currently completing implementation of projects under Teir II of its long-term control plan (LTCP), the last of which is the Baxter Boulevard North Storage Conduit (BBNSC). The BBNSC was recommended as part of a recent update of the City's LTCP and is intended to reduce the frequency and volume of discharges from CSOs 005, 006, and 007, all tributary to Back Cove, a shallow, enclosed embayment. As defined in the LTCP update, the BBNSC is required to provide approximately 7,571 m3 (2.0 million gallons [MG]) of storage to control overflows from approximately the first inch of rainfall. A 1,006 meter (3,300 foot) long rectangular box conduit was envisioned in the LTCP update to extend from CSO 007 at its upstream end to CSO 005 at its downstream end. Construction completion has been set for August 2013 ahead of the required date of December 2013.