Alewife CSO Plan does not keep up with Climate Change.

The Draft CSO Plan is designed so that a single, common 2050 5-year storm will still discharge
15.6 million gallons of untreated sewage and stormwater into Alewife Brook. That is the result
after $340 million is spent constructing projects in the Draft Plan at Alewife Brook.

According to MWRA’s Unified Typical Year Model, a 5-year storm under baseline conditions today
discharges 10.53 million gallons into the Brook. The Draft Plan therefore results in Alewife Brook
receiving nearly 50% more CSO volume in a common future 5-year storm than it receives today. The
Draft Plan does not keep up with climate change.

MWRA’s own baseline for a 2050 5-year storm at Alewife Brook is 20.9 million gallons. The Plan
proposes 5.3 million gallons of new storage against it, capturing roughly one quarter of the volume
and leaving 15.6 million gallons of CSO in the Brook during 5-year storm events.

A 5-year storm event has a 20% chance of occurring in any given year.