Gloucester-01A

Gloucester, Mill Pond

42.632916, -70.677217

Technical Specifications

Basic Properties

Type: Sluice Gate
Material: Metal
Control: Manual Gear
Condition: Good
Geometry: Rectangular
Status: Active
Number of Gates: 2

Operator & Management

Operator Type: PUBLIC
Purpose: Flood Protection and Restoration

Dimensions & Elevations

Dimensions: 6ft diameter, 3ft height
Invert Elevation: -4.46 NAVD88
Installation Date: 1970
Tidal Influence: Upstream: 3.54 NAVD88, Downstream: 3.84 NAVD88

Culvert Details

Restriction Type: Roadway
Geometry: Other
Material: Corrugated Metal
Bottom Material: Riprap
Number of Pipes: 0

Dimensions: 13ft diameter, 12ft height
Condition: Fair
Comments: The culvert material was corrugated metal piping and was a semi-circle with an approximate width of 13’ and an approximate height of 12’. The upstream portion of the culvert appeared to be in good condition with no apparent deterioration; however, the downstream portion was slightly separating from the headwall in places. Additionally, portions of the downstream culvert were jagged and appeared to pose a potential safety hazard.

2024 Field Survey Results

Comprehensive field assessment conducted in 2024

Physical Conditions Assessment

Channel Conditions

Channel Alteration: Limited (<133 ft/acre)
Channel Constriction: Narrower than channel
Channel Erosion: Little (<10% of bank)
Sediment Deposits: None

Blockages & Issues

Debris Blockages: None
Evidence of Overtopping: No

Transect Measurements

50 Yards

Open Water: 62
Salt Marsh: 0
Brackish: 0
Freshwater: 0
Ditch: 0
Unvegetated: 60

150 Yards

Open Water: 43
Salt Marsh: 0
Brackish: 0
Freshwater: 0
Ditch: 0
Unvegetated: 42

300 Yards

Open Water: 19
Salt Marsh: 0
Brackish: 0
Freshwater: 0
Ditch: 0
Unvegetated: 114

Ecological Assessment

Habitat Observations

Crab Burrow Intensity: None
Phragmites Present: Moderate (10-60%)
Ecological Impairment: Limited

Invasive Species

Upstream Invasive Species: Yes
Downstream Invasive Species: No
Invasive Species Notes: Limited to upland fringe
Additional Comments (2024): Appears to have sufficient tidal exchange as indicated by lack of phragmites and abundant saltwater invertebrate populations. Town noted tide gate is sometimes closed for extended periods of time. Result of which may have I ncreased ponding and creation of mud flats adjacent to marshy areas. Tide gate was draining well during visit but long term management or o and m plan may help restore more salt marsh.

Historical Records

Legacy data from previous surveys and documentation

Environmental Data

Invasive Species: Yes
Restoration Status: In-Progress
Invasive Comments: Abundant phragmites was observed upstream. It appeared that the phragmites extended to the upstream dam in Mill Pond.
Restoration Comments: New tide gates installed in 2011, 1 gate is being opened an additional 6 inches each year over 6 years. 2016 opening will occur in May.

Notes & Comments

General Comments: Site was easily accessible and located directly off of Washington Street (Route 127). Parking was available at a convenience store to the northeast of the site.
Operation Plan: Yes
Operation Comments: It appears that the operational purpose of Gloucester-01A was for incremental restoration and flood protection purposes. It can be incrementally opened to enable increased tidal flushing with the ability to be completely closed before a storm. It appears that the operational purpose of Gloucester-01B was two-fold: 1) It could be installed towards the invert of the headwall and be incrementally opened to enable restoration while enable outward passage of stormwater flows and mitigating flood potential from the tides. 2) It could be installed at the high position to act as a high level barrier to storm surge while allowing stormwater out the bottom. It appeared that Gloucester-01C was installed for the sole purpose of flood protection and stormwater conveyance. It appears that this trio of tide gates was recently installed and configured in 2011 and are being actively managed to enable upstream restoration.
Gate Comments: There were three tide gates at the site. Gloucester-01A was an old sluice gate with a manual jack screw located at the bottom of the eastern portion of the headwall. It was open approximately 2’ at the time of the site visit. Gloucester-01B was a newer combination metal sluice / flap gate. The sluice gate was able to operated via jack screw to be installed either at the invert of the headwall or towards the top. It was located towards the top of the headwall during the site visit, enabling low level tidal flushing through the bottom opening. Gloucester-01C was a metal flap gate installed in the middle portion of the headwall (i.e., Gloucster-01B could be located either above or below Gloucester-01C) (see field notes for diagram). All three of the tide gates appeared to be in good condition at the time of the site visit. Gloucester-01A was rusty, but corrosion was not evident and it appeared that the manual gear had recently been maintained and greased.

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). 1a) TG Inv (Gloucester-01A = Gloucester-01B): Top of HW El (D/S) = 7.74’; Inv Measuredown = 12.2’; TG Inv = 7.74’ – 12.2 = -4.46’ 1b) TG Inv (Gloucester-01C): Top of HW El (D/S) = 7.74’; Inv Measuredown = 5.00’; TG Inv = 7.74’ – 5.00 = 2.74’ 2) Upstream Tidal Influence: Top of headwall LiDAR Elevation = 7.74’; Staining Measuredown = 4.20’; U/S Tidal influence = 7.74 – 4.20 = 3.54’. 3) Downstream Tidal Influence: Top of headwall LiDAR elevation = 7.74’; Staining Measuredown = 3.90’; D/S Tidal Influence = 7.74’ – 3.90’ = 3.84’

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