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Freeport Low Sill Bulkhead and Marsh

Created by Jay Tanski on Jan 08, 2015  
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General
Construction Dates: 
Estimated
2005
Miller Avenue
Freeport , NY
United States
40° 37' 37.722" N, 73° 34' 56.532" W
New York US
Pre-Project Conditions
Submerged Aquatic Vegetation (SAVs) present?: 
No
Bank elevation above MHW: 
2.0 feet
Pre-Construction Erosion Present?: 
Yes
Pre-Construction Erosion at Adjacent Parcels?: 
Yes
Average Nearshore Slope: 
1:1,000.0
Existing Structures or Debris?: 
Yes
Describe Existing Structures or Debris at the Site: 
Deteriorated bulkhead, concrete rubble
Environmental Considerations
Name of Waterbody: 
Little Swift Creek, Hempstead Bay
Site Classification: 
Cove
Shoreline orientation relative to max. fetch distance: 
0 Degrees
Tidal Range: 
4.0 feet
Adjacent to Navigation Channel?: 
Yes
Boat wake exposure: 
Low
Project Site Within a Designated No-Wake Zone?: 
Yes
Salinity: 
Brackish: 0.5 – 30 ppt
Description of Nearby Structures: 
Marina with bulkhead, floating docks, pilings
100-year Flood Elevation Seaward of the Shoreline: 
7.9 feet
100-Year Flood Elevation Vertical Datum: 
NAVD88
Design Considerations
Was fill brought in?: 
Yes
Type of Fill: 
Sand
Amount of Fill: 
679 cubic yards
Source of Fill: 
Dredging of adjacent marina basin (679 cubic yards).
Proposed nearshore slope: 
1:60.0
Area of shallow bottom conversion to marsh: 
10,500 sq ft
Area of upland conversion to marsh: 
0 square feet
Length of Project: 
152 feet
Average Project Width: 
60 feet
Width of Wetlands Above MHW: 
30 feet
Width of Wetlands Below MHW: 
30 feet
Structural Elements
Did the project involve a structure?: 
Yes
Describe construction materials: 
Project involves 2 structures, a low sill bulkhead constructed of wood piling and whales and fiberglass sheet piling and a landward bulkhead/retaining wall constructed of vinyl sheet piling and wood piles and whales
Average distance of structure offshore (from existing MHW/NHW): 
45 feet
Average distance of structure offshore (from existing MLW/NLW): 
0 feet
Structure Base Width: 
1.0 foot
Length of Structure: 
250 feet
Structure Crest Width: 
1.0 foot
Area of shallow bottom conversion to structure: 
250 square feet
Width of Open Water Between Structure and Wetlands: 
0 feet
Height of Structure Above MHW: 
-1.2 feet
Maximum depth at seaward edge of structure: 
8.6 feet
Maximum depth at landward edge of structure (including fill): 
1.4 feet
Drop downs, or openings or overlaps?: 
No
Was geotextile used in foundation?: 
Yes
Porosity of structure: 
Low
Porosity of structure (for vertical structures only): 
0%
Non-Structural Elements
Percentage of vegetative cover between structure and MHW line: 
100%
Primary Wetland species below MHW: 
Spartina alterniflora (smooth cordgrass)
Primary wetland species above MHW: 
Spartina patens (saltmeadow cordgrass)
Root mat developed by vegetation?: 
Yes
Cross-section width of planted area: 
60 feet
Project Performance
Overall performance of Living Shoreline for erosion protection?: 
Medium
Describe overall structure and vegetation performance: 
Marsh appears very healthy and the landward bulkhead has arrested the erosion.
Overall performance of the structure and vegetation?: 
High
Describe overall erosion protection performance: 
The landward bulkhead provides a high degree of protection for the upland area. However the marsh maintained by the low sill bulkhead does seem to help attenuate wave energy as observed during a site visit on a day with strong winds out of the south and extreme high tides. See photos.
Storm Exposure: 
Yes
Storm Date: 
Monday, August 29, 2011
Storm Intensity: 
High
Describe Project Storm Performance: 
Hurricane Irene was a tropical storm by the time it made landfall on Long Island. The structure and marsh performed well.
Other Comments: 
This project actually involves two structures: a low sill bulkhead built in a triangular shape that holds a marsh in front of a higher bulkhead retaining wall landward.

Images

 

Documents

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PDF icon Low Sill Bulkhead_freeport.pdf671.66 KB