Updated CSO Rule -- A Step Towards Cleaner Water

A CSO example. Photo from USEPA.

A new rule to address combined sewer overflows (CSOs) was recently approved in Vermont. Combined sewer systems collect both sewage and stormwater in the same pipe. These systems were designed to have overflow points to direct excess flow out of the system during intense precipitation events. Doing so avoids overwhelming treatment plants, backups into basements, and street flooding from surcharging manholes. The discharge of untreated wastewater under wet weather conditions can adversely affect water quality and create short-term public health concerns.

The recently approved Rule clarifies the requirements applicable to the remaining CSOs within the State, consistent with existing federal law and the Vermont Water Quality Standards. Further, the Rule lays out the existing permits, tools, and processes the Vermont Agency of Natural Resources (VT ANR) will use to bring CSOs into compliance with federal and state law.

The recently approved rule revises policy that had been in place since 1990. VT ANR estimates there are over 60 combined sewers outfalls still remaining in 16 communities around the state, down from the 171 outfalls in 27 municipalities that existed when the 1990 rule was adopted.