Duxbury-01

Duxbury, Duxbury Harbor

42.041284, -70.669757

Dimensions: 1.5ft diameter
Condition: Fair
Comments: The culvert ran through a rip rap seawall. The culvert was cast iron, covered in barnacles, and appeared to be in fair condition. The upstream end of the culvert was unable to be assessed as it was obstructed by collapsing riprap. A vertical crack was forming on the face of the downstream concrete headwall which extended appx. 3 foot down to the tide gate. In addition, the concrete wing walls were beginning to crack.

Legacy data from previous surveys and documentation

Invasive Species: Yes
Restoration Status: Unknown
Invasive Comments: Bordering phragmites were observed in upstream impoundment
Restoration Comments: Aea has a Conservation Restriction possible restoration site

General Comments: Tide gate is accessible via a path from long point marina located off of Washington Street. Note that it is recommended that the marina be consulted prior to visiting site to confirm that accessing the site is ok. A "no trespassing" sign was observed to the south of the tide gate.
Gate Comments: The metal circular flap gate was operational; however, the bottom 10% of the flapper was beginning to corrode away.

Elevation Comments: Staining was apparent on the downstream (D/S) end of the headwall (HW) so approximate extent of D/S tidal influence was able to be assessed in addition to tide gate (TG) invert elevations. Staining was not apparent on the upstream (U/S) end of the HW, so extent of upstream tidal influence was not assessed. 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) = 4.73’; Inv Measuredown = 6.00’; TG Inv = 4.73 – 6.00 = -1.27’ 2) Upstream Tidal Influence: N/A 3) Downstream Tidal Influence: Top of headwall LiDAR elevation = 4.73’; Staining Measuredown = 1.5’; D/S Tidal Influence = 4.73’ – 1.5’ = 3.23’ Note: Downstream headwall elevation was challenging to obtain via LiDAR as it was enfolded into the rock seawall. As a result, two frequent points were used (1.59’ and 7.87’) to arrive at an average of 4.73’.