Sandwich-01
Sandwich, Dock Creek
41.757900, -70.490455
Technical Specifications
Basic Properties
- Type
- Flap Gate
- Material
- Metal
- Control
- —
- Condition
- Fair
- Geometry
- Rectangular
- Status
- Active
- Number of Gates
- 1
Operator & Management
- Operator Type
- PRIVATE
- Operator
- Comm. of MA Department of Transportation (Rail Road)
- Permits
- —
- Purpose
- Flood Protection
Dimensions & Elevations
- Dimensions
- 3ft diameter, 3ft height
- Invert Elevation
- —
- Installation Date
- —
- Tidal Influence
- —
Culvert Details
- Restriction Type
- Railroad
- Geometry
- Circular
- Material
- Ductile Iron Pipe
- Bottom Material
- —
- Number of Pipes
- 1
- Dimensions
- 3ft diameter
- Condition
- Poor
- Comments
- The circular ductile iron culvert appeared to be in good condition; minimal to no corrosion was observed. The downstream end of the culvert was located at the bottom of an embankment comprised of well graded and recently installed gravel. The upstream end of the culvert was located at the bottom of a wooden retaining wall in poor condition. The retaining wall was beginning to collapse at multiple locations, excessive wood rot was observed, and upland vegetation was observed growing through the retaining wall – further compromising its structural integrity.
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
- Severe (>60% of bank)
- Sediment Deposits
- Limited (<10% of channel width)
Blockages
- Debris Blockages
- None
- Evidence of Overtopping
- No
Ecological Assessment
Habitat Observations
- Ecological Impairment due to Tide Gate
- Severe
- Crab Burrow Intensity
- Limited (<10% banks are densely
- Ponding and Die-off Depressions
- None
- Phragmites Present
- Severe (>60%)
Invasive Species
- Upstream Invasive Species
- Yes
- Downstream Invasive Species
- Yes
- Invasive Species Notes
- Phragmites is dominant species, Japanese knotweed along upland boundary as well.
General Comments
Flapper appears to be severely limiting upstream flow as no salt marsh species are present. Phragmites mono culture and peat collapse are only habitat types on the upstream side. Upstream head wall is leaning into channel and may eventually collapse.Habitat Transects
First Transect (50 yards upstream of tide gate)
No data
Second Transect (150 yards upstream of tide gate)
No data
Third Transect (300 yards upstream of tide gate)
No data
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
- Unknown
- Invasive Comments
- The downstream portion of the marsh was comprised of a mixture of high marsh and phragmites while the upstream portion of the marsh was predominately phragmites. Upland vegetation was also observed along the railway embankment including wild cherry and sumac.
- Restoration Comments
- The site appeared to have good restoration potential; however, upgradient infrastructure (i.e. houses) were observed.
- Upstream Area
- Total: 2.07, Salt Marsh: 0
Notes & Comments
- General Comments
- The site is located at the Cape Cod Central Railroad crossing to the southwest of Dewey Avenue (appx. 226 feet) and to the southeast of Liberty Street (appx. 400 feet). The easiest access to the site is along the side of the railroad berm from Liberty Street. Caution should be exercised when accessing the site as this rail line is active.
- Operation Plan
- No
- Operation Comments
- It appeared that the primary purpose of the flap gate was for upstream flood protection.
- Gate Comments
- The square metal flap gate was located on the seaward opening of the culvert and was in fair condition. It appeared that the tide gate had recently been bolted back onto the culvert as evidenced by new “shiny” mounting hardware; however, the metal comprising the flap gate was deformed and did not appear to form a tight seal against the culvert opening. A 3-5” gap was observed from which tidal exchange could occur. In addition, the bottom half of the tide gate was corroded and its operation was impeded by heavy algae growth. It was unclear if the tide gate would be able to fully open in the event of a storm event to pass heavy upstream flows.
- Elevation Comments
- The extent of upstream (U/S) and downstream (D/S) tidal influence as well as the invert of the tide gate was not measured at this site as there was no headwall or other prominent point of reference from which to take a measuredown from for later referencing via LiDAR.
- Visit Comments
- —
- Other Comments
- —
- External Data Comments
- —
Part of the Massachusetts Bays Program© 2026 Massachusetts Bays Program. Monitoring tidegates across Massachusetts.