Combined Sewer Overflows in the Mystic River and Alewife Brook in 2024
Andy Hrycyna
01-07-2025
CSO activations and volumes, Alewife Brook and Mystic River 2024
The following data is downloaded from the MA EEA Data Portal for CSOs. Precipitation data is acquired from USGS gage at Fresh Pond, near Alewife Brook.
The CSO discharges on Alewife Brook are untreated: raw sewage makes its way directly to the stream. The CSO discharges on the Mystic River, while larger, are treated or partially treated CSOs.
Nearly 19 million gallons of CSO discharge in Alewife Brook 2024
Alewife Brook is the scene of the largest untreated CSO discharges in the Mystic Watershed. 2024 was a year in which many high-intensity storm events, expected to increase with climate change, drove high frequency and volumes of Alewife CSOs, especially. in the first half of the year. The area experienced drought conditions in the second half of the year, which limited the number of storms that led to CSOs. CSO discharges to Alewife Brook in 2024 totaled 18,919,000 gallons in 24 events.
| Month | Releases | Gallons | EventType |
|---|---|---|---|
| Jan | 6 | 13,734,000 | Untreated |
| Feb | 0 | 0 | Untreated |
| Mar | 2 | 60,000 | Untreated |
| Apr | 0 | 0 | Untreated |
| May | 6 | 2,545,000 | Untreated |
| June | 5 | 1,466,000 | Untreated |
| July | 2 | 934,000 | Untreated |
| Aug | 3 | 180,000 | Untreated |
| Sept | 0 | 0 | Untreated |
| Oct | 0 | 0 | Untreated |
| Nov | 0 | 0 | Untreated |
| Dec | 0 | 0 | Untreated |
Total CSOs in Mystic River Watershed 2024
These graphs show the total number of activations and volumes for Alewife Brook and Mystic River together in 2024. CSO discharges in the Mystic watershed as a whole in 2024 totaled 100,246,759 gallons in 58 separate events.
| Month | Releases | Gallons | EventType |
|---|---|---|---|
| Jan | 4 | 33,950,000 | Treated |
| Jan | 8 | 13,843,955 | Untreated |
| Feb | 0 | 0 | Untreated |
| Mar | 7 | 24,110,000 | Treated |
| Mar | 2 | 60,000 | Untreated |
| Apr | 3 | 6,780,000 | Treated |
| May | 4 | 9,494,000 | Treated |
| May | 6 | 2,545,000 | Untreated |
| June | 3 | 2,780,000 | Treated |
| June | 6 | 1,478,873 | Untreated |
| July | 2 | 1,410,000 | Treated |
| July | 3 | 936,776 | Untreated |
| Aug | 2 | 1,930,000 | Treated |
| Aug | 5 | 186,303 | Untreated |
| Sept | 0 | 0 | Untreated |
| Oct | 0 | 0 | Untreated |
| Nov | 2 | 730,000 | Treated |
| Dec | 1 | 11,852 | Untreated |
2024 Total Volumes by Outfall
CAM401 is responsible for the majority of releases in Alewife Brook.
| OutfallId | WaterBody | 2024 |
|---|---|---|
| CAM001 | ALEWIFE BROOK | 0 |
| CAM401A | ALEWIFE BROOK | 12,158,000 |
| CAM401B | ALEWIFE BROOK | 915,000 |
| MWR003 | ALEWIFE BROOK | 2,020,000 |
| SOM001A | ALEWIFE BROOK | 3,826,000 |
| BOS019 | LITTLE MYSTIC CHANNEL | 423,000 |
| BOS017 | MYSTIC RIVER | 99,000 |
| CHE004 | MYSTIC RIVER | 44,759 |
| MWR205 | MYSTIC RIVER | 73,234,000 |
| SOM007A/MWR205A | MYSTIC RIVER | 7,950,000 |
Greater Boston CSOs: Mystic, Charles, Boston Harbor in 2024 to date
