Stormwater Management: Cambridge vs Somerville
How do stormwater management rules compare between Cambridge, MA and Somerville, MA?
Cambridge and Somerville have similar restriction levels.
Cambridge, MA
Middlesex County
Cambridge requires stormwater management plans for construction disturbing one acre or more and implements strict post-construction standards to reduce flooding and protect the Charles River and Alewife watershed.
View full Cambridge rules →Somerville, MA
Middlesex County
Somerville is an EPA MS4 community. Projects disturbing 1 acre need NPDES permits; local review kicks in at 500 sq ft of new impervious surface.
View full Somerville rules →Key Facts Comparison
| Fact | Cambridge | Somerville |
|---|---|---|
| Trigger | 1 acre disturbance | - |
| Standard | First inch treatment | - |
| Program | EPA MS4 Phase II | - |
| LID | Encouraged or required | - |
| Illicit discharge | Prohibited | - |
| Federal permit | - | NPDES at 1 acre disturbance |
| Local trigger | - | 500 sq ft impervious |
| Design standard | - | No net peak runoff increase |
| Illicit discharge fine | - | Up to $5,000 per day |
| Watershed | - | Mystic River basin |
Highlighted rows indicate differences between cities.
Cambridge FAQ
When do I need a stormwater plan?
Projects disturbing one acre or more trigger the full stormwater plan; smaller projects in sensitive areas may also need review.
Can I discharge anything to the storm drain?
No, only clean stormwater; wash water, chemicals, and pool water are illicit discharges subject to fines.
Somerville FAQ
I am replacing my driveway with the same area. Do I need stormwater review?
Replacement in kind with no expansion generally does not trigger full review, but switching to a less-pervious surface or expanding the area over 500 square feet does.
Where does Somerville's stormwater go?
Most of the City drains to the Mystic River via MWRA and DCR systems, and some combined sewer areas flow to the Deer Island treatment plant during dry weather.
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