Public Comment Period Open for CSO Outfall Notification Plan

The city has prepared and submitted a final combined sewer overflow (CSO) plan to the Massachusetts Department of Environmental Protection (MassDEP).

The plan details the process for notifying the public when there is an event that necessitates a combined sewer overflow activation. Chelsea is allowed, under a state environmental permit, to discharge sewage to the Chelsea Creek during heavy rain events through three CSO outfalls, according to the city’s plan.

The complete plan can be viewed at and written comments can be submitted to the MassDEP until Feb. 22 by email at [email protected] or by mail to 100 Cambridge St., Suite 900, Boston, MA 02214. Written comments can be submitted to the City of Chelsea by email to [email protected] or by mail to Chelsea Public Works, 500 Broadway, Suite 310, Chelsea, MA 02150.

According to the plan, approximately 70 percent of Chelsea is serviced by combined sewers, and the remaining 30 percent is serviced by separate sanitary sewers and storm drains. Chelsea’s system consists of one collection system and one stormwater pump station. There are no sewage treatment plants in Chelsea.

During normal conditions, sewage and combined sewage is discharged to MWRA interceptors that transport flows to the Deer Island Treatment Plant.

Chelsea is currently working towards separating its combined storm drains and sewers to reduce the amount of untreated sewage that is discharged from the CSOs during high volume precipitation events. According to the plan, this reduction in volume and activation frequency will help improve water quality in the Mystic-Chelsea Confluence.

The CSO public notification plan outlines steps for when there will be a CSO outfall activation and how the public will be notified.

Water and sewer department staff will monitor the weather for possible rain events, and alarms that indicate a possible CSO activation are sent by text message to water and sewer department employees. After receiving a text alert, staff will review the Flow Assessment Services (FAS) web page to determine if an activation has occurred, a process that can take up to four hours.

After an activation has been confirmed, staff will take up to two hours to send out notifications via Constant Contact that will include information for all CSO outfalls in the city. The email will note the start and stop time, along with the volume for any outfalls activated. If an outfall was not activated, the line associated with that outfall will read “no discharge.”

Notifications will be sent out to the Boston Public Health Commission, all community members who signed up on Chelsea’s web page, and a list of community stakeholders that currently receive notifications. That list consists of members of the EPA, MassDEP, MWRA, Mystic River Watershed Alliance, GreenRoots, local newspapers, the city’s public health director, city employees, and other interested parties.

All activations will be posted on the city web page as soon as practicable, but no later than the next business day. All volumes of the outfalls will be calculated by FAS and entered into the system monthly as required.

Leave a Reply

Your email address will not be published. Required fields are marked *