Crescent Beach Seawall and Revetment Repair: Hull, Massachusetts

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The existing shore protection system at Crescent Beach consists of a 1,600-foot seawall and revetment structure along Atlantic Avenue in Hull, MA.  Atlantic Avenue is one of three evacuation routes for the Town of Hull, however the road often becomes overwashed with sediment and debris during storms as a result of overtopping water over the seawall.  Due to the downward land slope from the seawall and across the barrier beach, overtopped water and debris flows into Straits Pond, an Area of Critical Environment Concern (ACEC).  In recent years, some progress has been made to increase the resiliency of the homes via elevating properties on pilings, relocating buildings from the seawall, and flow-through decking installed to reduce storm damage.  However, the existing concrete seawall and smooth-grouted rubble revetment has been damaged and although a series of repairs have been made to stabilize the structure, the efforts were not effective in the long term.  The smooth surface and loss of voids associated with grouting accentuates wave runup and overtopping, causing further damage to the homes and infrastructure that the revetment and seawall were designed to protect.

Repair of the existing seawall and revetment was chosen as the most appropriate solution after an evaluation of potential alternatives, including the “do nothing” approach, beach nourishment, and a nearshore wave break structure.  Wave modeling of the 100-year storm was completed in order to develop the design conditions for the repaired structure.  Seven combinations of seawall heights, revetment sizes, and revetment slopes were considered and evaluated based on the effectiveness of reducing wave overtopping and potential environmental consequences.  The final structure design consists capping and raising the height of the seawall by 2 feet and reconstructing the revetment with larger, angular armor stones.  The western section of the revetment was designed to be larger than the eastern section based on the vulnerability of the section to larger waves.  This design provided sufficient wave overtopping reduction while minimizing the structure footprint and associated environmental impacts. Applied Coastal also filed and completed the federal, state, and local permitting and prepared the construction bid package for the project.

Hull, Massachusetts, seawall structure, seawall design