April showers bring… May CSOs? Preventing CSOs (combined sewer overflows) is a top priority for municipalities with combined systems, and looming capacity issues and deteriorating sewer infrastructure only exacerbate the problem. To raise awareness of the issue, we’ve summarized a few valuable online resources below:
The earliest combined sewer systems were introduced in 1855. These networks of underground pipes replaced open ditches, collecting rainwater runoff, domestic sewage, and industrial wastewater, all in the same line. Initially these systems discharged directly into waterways, but in the early twentieth century sewage plants were introduced to treat the wastewater beforehand. Even so, when water from rain and snowmelt overwhelms sewer capacity, excess sewage is still discharged directly to waterways—an event commonly known as a combined sewer overflow. While these overflows prevent wastewater from backing up into homes and businesses, they contaminate lakes, rivers, and coastal waters—potentially harming public health and the environment.
Sewer overflows can violate the Clean Water Act and result in enforcement actions by the Environmental Protection Agency (EPA). To resolve the violations, the EPA typically requires rehabilitation of the sewer collection and treatment system, and imposes penalties for past leaks and overflows. To encourage settlement, the EPA offers to compromise on penalties if the municipality agrees to undertake the necessary rehabilitation work. This agreement is typically recorded in a judicially monitored “consent decree.”
The EPA has made much progress in keeping raw sewage and contaminated stormwater out of public waterways. By the end of the 2015 fiscal year, 201 municipal combined sewer systems serving populations over 50,000 were addressed. By the end of this fiscal year (2016), the EPA will have addressed all 213 such systems with untreated sewer overflows. The above map shows the locations of these systems.
A part of complying with a consent decree is doing a full analysis of you sewer infrastructure. One such analysis workflow is the Phased Assessment Strategy for Sewers (PASS). With PASS you can prioritize which lines need the most attention, and also keep your system-wide assessment more current.