Combined Sewer Overflow (CSO) Control Program

Before the widespread construction of water pollution control facilities which began in the 1960s, the Kenduskeag Stream and the Penobscot River were heavily polluted by their continued use from municipalities and local industry along their waterfronts.  Within the Bangor region, residents who had access to these water bodies were no longer able to use them for recreational purposes.   Because of their deteriorating water quality, there was a call for action to address the poor condition of the streams and rivers within the Bangor region. 

By the 1980s, several municipalities within the region, including Bangor, had constructed waste water treatment plants and expanded their sewer collection systems in order to better protect the rivers and streams within their borders.  As a result of these efforts, the water quality within the streams and rivers began to improve. 

Bangor is currently developing its Phase II Long Term Control Plan (LTCP) for combined sewer overflow (CSO) reduction.  A CSO occurs when wet weather (storm water) flows overwhelm the capacity of the sewer collection system and exit the sewer system through licensed relief points before receiving treatment at the City’s wastewater treatment plant.  Under the first LTCP, which began in the early 1990s, Bangor began constructing improvement projects to reduce CSOs that continued to benefit the regional environment.  Each year, engineers compared the annual discharge volumes with the original sewer system computer model predictions to evaluate progress.  The following table is a summary of the combined sewer overflow reductions that were achieved during the first LTCP:

Click here to view a table of CSO level of control by year

Prior to completing any work under the first LTCP in the early 1990s, the city’s sewer system computer model predicted that Bangor would discharge 635 million gallons of untreated CSOs into waterways annually during wet weather events.  In 2015, Bangor’s discharge of CSOs to the Kenduskeag Stream and the Penobscot River was 40 million gallons.  Reducing CSOs helps to improve water quality and encourages recreational activities such as; eating lunch or walking in the waterfront park, boating, fishing, or participating in the Kenduskeag Stream Canoe Race, which held its 50^th race in April 2016.  These are some of the visible benefits resulting from the sewer improvement projects completed by the City of Bangor and other municipalities within the region.