Manchester-01
Manchester, Sawmill Brook
42.575154, -70.772898
Technical Specifications
Basic Properties
- Type
- Sluice Gate
- Material
- Metal
- Control
- Electric Actuator
- Condition
- Good
- Geometry
- Rectangular
- Status
- Active
- Number of Gates
- 1
Operator & Management
- Operator Type
- PUBLIC
- Operator
- Town of Manchester
- Purpose
- Other
Dimensions & Elevations
- Dimensions
- 5ft diameter, 5ft height
- Invert Elevation
- -4.9 NAVD88
- Tidal Influence
- Upstream: 5.87 NAVD88, Downstream: 3.6 NAVD88
Culvert Details
- Restriction Type
- Roadway
- Geometry
- Other
- Material
- Granite Block
- Bottom Material
- Riprap
- Number of Pipes
- 0
- Dimensions
- 12ft diameter, 7ft height
- Condition
- Poor
- Comments
- The culvert underneath the roadway was semi-circular granite block. It appeared to be in good condition on the downstream end; however, the upstream headwall was in poor condition – A chunk of the headwall had fallen into the channel, exposed rebar was observed, and a vertical crack was forming in the top middle of the headwall that extended almost down to the top of the culvert opening.
Historical Records
Environmental Data
- Invasive Species
- No
- Restoration Status
- Not Applicable
- Invasive Comments
- The upstream area was urbanized and was comprised of a granite block lined open channel which led to a small pond.
Notes & Comments
- General Comments
- The site was easily accessible and is located directly off of Bridge Street (Rt. 127). Parking was available in a parking lot off of Church Street behind the Town Hall.
- Operation Plan
- No
- Operation Comments
- At the time of the site visit, the sluice gate was open approximately 20 inches. The tide gate periodically fully closed in the winter to enable ice skating and is held open in the months of March through May for the annual smelt run. The tide gate and associated spillway control structure are Manchester’s highest hazard priority and extensive studies were being performed at the time of the site visit by others to determine how to operate, retrofit, or remove it. Apparently, the control structure causes upstream flooding during storm events by impeding outflows and creating a backwater effect. There is no mechanism to operate the tide gate for flood protection as storm surges or abnormally high tides can spill over the concrete weir.
- Gate Comments
- There was a metal sluice gate with an electric actuator at this location. The tide gate was installed at the downstream end of a culvert in the face of a two sided 90 degree concrete overflow structure approximately 7 feet tall. The spillway was configured to enable free tidal exchange once overtopped, while the tide gate could be partially opened to enable tidal exchange at lower water levels. The tide gate was rusty but appeared to be in good condition with no evidence of corrosion. The actuator also appeared to be in good condition and appeared to be approximately 15 to 25 years old. A direct measurement of the tide gate could not be obtained, so dimensions were approximated. The actuator and tide gate were located behind a chain link fence with a padlock; however, it was not locked at the time of the site visit. It appeared that power to the actuator was not locked out and could potentially be operated by anyone from the general public.
- Elevation Comments
- Staining was apparent on the upstream (U/S) and downstream (D/S) ends of the headwall (HW) so approximate extent of U/S and D/S tidal influence was able to be assessed in addition to tide gate (TG) invert elevations. The below lists measuredowns taken with a surveyors rod and corresponding top of headwall LiDAR elevations (NAVD88 datum). 1) TG Inv (D/S tide gate): Top of HW El (D/S) = 10.00’; Inv Measuredown = 14.90’; TG Inv = 10.00’ – 14.90 = -4.90’ 2) Upstream Tidal Influence: Top of headwall LiDAR Elevation = 9.97’; Staining Measuredown = 4.10’; U/S Tidal influence = 9.97 – 4.10 = 5.87’. 3) Downstream Tidal Influence: Top of headwall LiDAR elevation = 10.00’; Staining Measuredown = 6.4’; D/S Tidal Influence = 10.00’ – 6.40’ = 3.6’ Note: U/S Influence is greater than D/S influence – this could be a result of potentially erroneous LiDAR data or could be indicative of backwater flooding effects described in the tide gate operational comments field.
- Other Comments
- 2016 Sawmill Brook Culvert and Green Infrastructure Assessment - CZM grant; Tighe&Bond.
Part of the Massachusetts Bays ProgramNavigation
Learn More
© 2025 Massachusetts Bays Program. Monitoring tidegates across Massachusetts.