Massachusetts Designated Nitrogen Sensitive Areas: The Full 2026 Town and Embayment List

By The Complos Team. Last reviewed 2026-05-14.

TL;DR. The complete MassDEP NSA designation list under 310 CMR 15.215. Every town, every embayment, every trigger flow inspectors need before walking into a sale-trigger Title 5 in coastal MA.

A Title 5 inspector can read 310 CMR 15.000 cover to cover and still walk into a Mashpee or Wellfleet inspection unaware that the parcel sits inside a Designated Nitrogen Sensitive Area. The NSA framework lives under 310 CMR 15.215 and the operational town-and-embayment list lives in MassDEP's NSA designation memos plus the Cape Cod Commission and South Coast watershed-permit overlays. Three different sources, no single official table that's exactly current.

This is the consolidated 2026 list as it operationally applies — the embayments, the host towns, and the design-flow trigger that pulls the parcel into the NSA framework. If you're inspecting in MA coastal towns this is the reference card you need before you walk in.

Part of the MA Watershed + NSA Compliance guide.

What Triggers an NSA Designation

Under 310 CMR 15.215, an NSA is designated where:

• The receiving water is nitrogen-impaired (typically a coastal embayment with an EPA-approved or pending TMDL).
• The recharge area is mapped and the parcel sits inside it.
• MassDEP, in coordination with the regional planning agency (Cape Cod Commission, MAPC, SRPEDD), formalizes the designation.

The practical effect for the inspector and homeowner: the parcel is subject to the watershed-permit and I/A nitrogen-reducing requirements layered on top of the standard Title 5 floor.

Cape Cod (Barnstable County)

Every town on Cape Cod has at least one NSA. The major embayments by host town:

Barnstable: Three Bays (Cotuit, Osterville, Marstons Mills), Lewis Bay, Centerville River, Halls Creek, Rushy Marsh Pond.

Bourne: Phinneys Harbor, Eel Pond, Pocasset River, Buttermilk Bay (shared with Wareham).

Brewster: Pleasant Bay (shared four-town watershed permit), Quivett Creek (shared with Dennis), Stony Brook.

Chatham: Pleasant Bay, Stage Harbor, Sulphur Springs, Muddy Creek (shared with Harwich).

Dennis: Bass River (shared with Yarmouth), Sesuit Harbor, Quivett Creek, Swan Pond.

Eastham: Salt Pond, Nauset Marsh (shared with Orleans), Rock Harbor.

Falmouth: West Falmouth Harbor, Waquoit Bay (shared with Mashpee), Great Pond, Green Pond, Bournes Pond, Eel River.

Harwich: Pleasant Bay, Allen Harbor, Wychmere Harbor, Saquatucket Harbor, Herring River.

Mashpee: Popponesset Bay, Waquoit Bay, Mashpee River, Quashnet River, Hamblin Pond.

Orleans: Pleasant Bay, Nauset Harbor, Town Cove, Rock Harbor.

Provincetown: Mostly sewered — the small NSA exposure is in unsewered fringe areas around Hatches Harbor.

Sandwich: Old Harbor Creek, Scorton Creek, Three Mile Pond.

Truro: Pamet Harbor, Pilgrim Lake.

Wellfleet: Wellfleet Harbor, Herring River, Duck Creek, Loagy Bay.

Yarmouth: Bass River, Lewis Bay, Parkers River, Mill Creek, Swan Pond River.

Buzzards Bay (South Coast)

The Buzzards Bay NEP coordinates these designations with MassDEP:

Bourne: Phinneys Harbor, Pocasset Harbor.

Dartmouth: Slocum's River / Little River, Apponagansett Bay.

Fairhaven: Nasketucket Bay, West Island sub-areas.

Falmouth: West Falmouth Harbor, Megansett Harbor, Wild Harbor.

Marion: Aucoot Cove, Wings Cove, Sippican Harbor.

Mattapoisett: Mattapoisett Harbor, Brandt Island Cove.

New Bedford: Sewered footprint dominates; small NSA exposure in fringe areas.

Wareham: Wareham River Estuary, Onset Bay, Buttermilk Bay.

Westport: Westport River East and West Branches.

South Shore (Plymouth and Norfolk Counties)

Marshfield: North River, South River (shared with Scituate, Norwell, Pembroke, Hanover, Hanson).

Scituate: South River, North River, First, Second, and Third Cliff coastal embayments.

Cohasset: Little Harbor, Bound Brook.

Hingham: Weir River, Straits Pond.

Hull: Straits Pond, Weir River.

Quincy: Town Brook, Black's Creek (mostly sewered).

Plymouth: Eel River, Plymouth Harbor (limited NSA — significant sewered footprint), White Horse Beach embayments.

Duxbury: Duxbury Bay, Bluefish River, Back River.

Kingston: Kingston Bay, Jones River.

North Shore and Cape Ann

Salem: South River (limited NSA — mostly sewered).

Beverly: Bass River.

Manchester: Cat Cove.

Gloucester: Annisquam River, Walker Creek, Little River.

Rockport: Pigeon Cove.

Ipswich: Ipswich River estuary, Plum Island Sound (shared with Newbury, Rowley, Newburyport).

Newburyport, Newbury, Rowley: Plum Island Sound, Parker River, Rowley River.

Salisbury: Merrimack River estuary mouth.

Islands (Dukes and Nantucket Counties)

Edgartown, Oak Bluffs, Tisbury, West Tisbury, Chilmark, Aquinnah: Sengekontacket Pond, Lagoon Pond, Lake Tashmoo, Edgartown Great Pond, Tisbury Great Pond, Chilmark Pond.

Nantucket: Nantucket Harbor, Madaket Harbor, Polpis Harbor, Long Pond, Hummock Pond.

The Trigger Flow Question

A common confusion: NSAs do not have a parcel-level design-flow trigger like the SAS sizing rules under 15.203. The parcel is in or out based on the recharge-area boundary on the MassDEP / Cape Cod Commission shapefile. The 330 lb N/yr aggregate threshold operates at the cluster level, not the parcel level.

What this means for the inspector: if the parcel is inside the polygon, the watershed compliance notice attaches, full stop. Do not gate it on the parcel's design flow.

Where the Town Map Disagrees with the State

This happens more than you'd think. Towns sometimes show NSA boundaries on their assessor's parcel viewer that don't match the MassGIS shapefile. The state shapefile is the authoritative source for the regulatory designation; the town map is illustrative only.

When they disagree, default to the state shapefile and tell the homeowner the discrepancy is map-display, not regulatory. If the BOH agent insists the town map is correct, escalate to MassDEP's Bureau of Water Resources before writing the report against the wrong boundary.

How to Pull the Official Layer

The MassGIS NSA layer is published as a shapefile under the watershed-protection layer group. Refresh cadence is roughly quarterly; major rule changes (new TMDLs, new town watershed permits) drop in batches. Complos's watershed lookup tool ingests the layer and checks parcel address against the polygon set on a 90-day refresh.

The Failure Mode

The "I'll catch it from the Cape Cod Commission map" approach misses parcels in Buzzards Bay, South Shore, Cape Ann, and the Islands. The Cape Cod Commission only covers Barnstable County. South Coast NSAs sit under SRPEDD coordination; Cape Ann sits under MAPC. Use the state-level MassGIS shapefile or a tool that aggregates all of them; do not rely on a single regional planning agency map.

Frequently asked questions

What's the short answer to "Massachusetts Designated Nitrogen Sensitive Areas: The Full 2026 Town and Embayment List"?

The complete MassDEP NSA designation list under 310 CMR 15.215. Every town, every embayment, every trigger flow inspectors need before walking into a sale-trigger Title 5 in coastal MA.

Who does this apply to?

NEIWPCC-certified Title 5 system inspectors in Massachusetts, FDEP-licensed septic contractors in Florida, SCDHS-permitted designers in Suffolk County NY, and the property owners these professionals serve.

Where can I read the underlying regulation?

Every Complos guide links to the source statute or rule in the body. MA Title 5: 310 CMR 15.000. FL HB 1379 / HB 1417. NY: Suffolk County Sanitary Code Article 19. Always confirm with mass.gov / flsenate.gov / suffolkcountyny.gov before acting.

How does Complos help with this?

Complos generates the regulator's exact PDF, validates the inspection against the local overlay, and tracks per-town submission methods so you don't ship the report into a black hole. Start a 14-day trial at complos.ai/signup.

How Complos helps

Complos consolidates the MassGIS NSA layer with the per-town watershed-permit and Article 51 bylaw overlays into a single parcel lookup, so you see the host embayment, the I/A-at-replacement trigger, and the watershed compliance notice template in one query. Run the watershed lookup against any MA parcel before the inspection, and pair it with the Title 5 compliance checker to make sure Title 5 inspection report carries the right notice.

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