Marshfield-02A
Marshfield, Green Harbor
42.089292, -70.644468
Technical Specifications
Basic Properties
- Type
- Self Regulating Tide Gate
- Material
- Metal
- Control
- Counterweights
- Condition
- Good
- Geometry
- Rectangular
- Status
- Active
- Number of Gates
- 4
Operator & Management
- Operator Type
- PUBLIC
- Operator
- Town of Marshfield
- Permits
- ACOE
- Purpose
- Flood Protection and Restoration
Dimensions & Elevations
- Dimensions
- 4ft diameter, 3ft height
- Invert Elevation
- —
- Installation Date
- —
- Tidal Influence
- —
Culvert Details
- Restriction Type
- Roadway
- Geometry
- Rectangular
- Material
- Concrete
- Bottom Material
- —
- Number of Pipes
- 2
- Dimensions
- 4ft diameter, 3ft height
- Condition
- Good
- Comments
- Both culverts appeared to be in good condition. The upstream wingwall was in good condition, but appeared to be starting to slightly separate from the headwall.
Salt Marsh Field Assessment Results
Comprehensive field assessment dataPhysical Conditions Assessment
Channel Conditions
- Channel Alteration and Ditching
- Limited (<133 ft/acre)
- Channel Constriction
- Narrower than channel
- Channel Erosion
- Little (<10% of bank)
- Sediment Deposits
- None
Blockages
- Debris Blockages
- Limited (<10% of opening)
- Evidence of Overtopping
- No
Ecological Assessment
Habitat Observations
- Ecological Impairment due to Tide Gate
- Severe
- Crab Burrow Intensity
- None
- Ponding and Die-off Depressions
- Severe (>60% of marsh platform
- Phragmites Present
- Severe (>60%)
Invasive Species
- Upstream Invasive Species
- Yes
- Downstream Invasive Species
- Yes
- Invasive Species Notes
- Phragmites along fringe, becomes dense and surrounding channel approximate 570 feet upstream of tide gate.
General Comments
Tide gate submerged due to incoming tide, not all factors could be assessed, however severe die off, lack of low marsh community, constriction of sediment exchange and encroaching phragmites indicate tidal restriction.Habitat Transects
First Transect (50 yards upstream of tide gate)
Second Transect (150 yards upstream of tide gate)
Third Transect (300 yards upstream of tide gate)
Restoration Potential
Assessment
- Salt Marsh Impairment due to Tidal Restriction
- Moderate
- Potential Extent of Marsh Restoration
- Moderate
- Implementation Feasibility
- High
- Restoration Priority
- High
- Recommended Improvement Type
- O&M and Infrastructure
Notes
Site shows moderate salt marsh impairment due to restricted tidal flow. Replacement with self-regulating tide gate could restore approximately 5-8 acres of degraded marsh habitat. Good access for construction equipment. Regional coordination completed with town DPW and conservation commission.Historical Records
Environmental Data
- Invasive Species
- Yes
- Restoration Status
- In-Progress
- Invasive Comments
- Upstream impoundment was mostly comprised of high marsh with some low marsh and fringing phragmites.
- Restoration Comments
- —
- Upstream Area
- Salt Marsh: 10-15 acres
Notes & Comments
- General Comments
- Site is located directly off of Town pier Road and easily accessible. Note that Jason Burtner can provide permitting drawings and other relevant files and site information to further flesh out attributes. Permitted together with Marshfield 01.
- Operation Plan
- No
- Operation Comments
- Self-regulating tide gate installed to enable expanded upstream tidal exchange will still providing flood protection.
- Gate Comments
- There were two tide gates installed at this location. A metal self-regulating tide (SRT) gate was installed to the west (Marshfield-02A) and a metal flap gate was installed to the east (Marshfield-02B). The self-regulating tide gate was in good condition and was operable (all of its floats were intact). The SRT was installed at a 45 degree angle to enable it to directly face the channel. A hand operated winch and strap had been installed to operate the SRT and the strap was weathered. The metal flap gate appeared to be in good condition and operable.
- Elevation Comments
- See "General Comments". Invert elevation and extent of downstream tidal influence can be located on permitted plans to be uploaded. Staining was not apparent on the upstream headwall (i.e., it was higher), so extent of upstream tidal influence could not be assessed.
- Visit Comments
- —
- Other Comments
- Many killifish were observed on the downstream side of the tide gate.
- External Data Comments
- US ACOE NAE-2004-3126 Green Harbor Tide Gates Permit Application 10.2.2002 US ACOE NAE-2004-3126 Green Harbor Tide Gates Permit 12.3.2004 US ACOE NAE-2004-3126 Green Harbor Tide Gates Operation and Maintenance Plan 12.3.2004 Nekton, Inc. Green Harbor Tide Gate Report 8.10.2003 (Other)
Part of the Massachusetts Bays Program© 2026 Massachusetts Bays Program. Monitoring tidegates across Massachusetts.