CSO Regulatory Timeline

with links to source documents


DECEMBER 31, 2021
Metropolitan Water Resource Authority (MWRA) Combined Sewer Outfall (CSO) “Final Performance Assessment and Water Quality Assessment” Report is out.


Public comment meeting date will be announced for MWRA’s CSO Report, thirty days in advance of a February meeting. Source: DEP 2019 Alewife Variance Permit, Section C(1)(b)(iii)

FEBRUARY 2022 (date TBD)
Public comment meeting on the MWRA’s CSO Report.
Source: MADEP 2019 Alewife Variance Permit, Section C(1)(b)(ii)

We need everyone to show up to this online meeting in order to make our voice heard! We need to flood the meeting with public comment and demand that the area municipalities and the MWRA develop a second long term CSO control plan to modernize the 19th Century combined sewer systems and close the remaining Alewife CSOs. More needs to be done in the face of Climate Change!

APRIL 1, 2022
Cambridge, Somerville, and MWRA submit to federal EPA and state Department of Environmental Protection (DEP) a scope and schedule for an updated CSO control plan.
Source: MWRA CSO Assessment Public Briefing, May 2020 p. 21

We must work now to educate the municipalities about the realities of pollution and flooding in the Alewife Brook, so that the scope of the new plan includes full sewer separation and an end to sewage pollution in the Alewife Brook including that from other contaminated storm water sources.

APRIL 30, 2022
Deadline for the cities’ annual CSO reporting. The cities will provide a comparison between the precipitation for the year 2021 and the precipitation of the typical year. The annual report will also provide a comparison between the activation volume and frequency for each CSO in 2021 compared to the typical year and the MWRA Long Term Control Plan requirements.


JUNE 30, 2023
Cambridge, Somerville and MWRA must submit a Draft Recommended CSO Control Plan to EPA and DEP for review.
Source: DEP Variance Permit, p.8, section F(5)

We need to demand that green and gray infrastructure technologies are employed to fully separate the combined sewers, close the CSOs, clean the stormwater for contaminants, and provide the public with a safe Alewife Brook that is boatable and fishable.

DECEMBER 31, 2023
Cambridge, Somerville and MWRA submit a Final Recommended CSO control plan to EPA and DEP for review and approval.
Source: MWRA 2019 Compliance Report, see page 9 / DEP Variance Permit, p.8, section F(5)


AUGUST 31, 2024
Massachusetts DEP Temporary 5 Year Variance Permit Expires. This permit is issued by the state and allows the municipalities’ combined sewer systems to pollute the Alewife Brook during wet weather.
Source: MADEP Variance Permit