A series of four segmented breakwaters, each approximately 100 feet long, were used to control erosion along an eroding cliff face on the Potomac River facing to the North West. This 30 foot high cliff face is exposed to strong winds blowing over 12 miles of the Potomac River, thereby allowing large waves to build up and pound into the base of the cliff face.
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The open topped concrete boxes, made by Rotondo Precast of Fredericksburg, were delivered on flatbed trucks, offloaded and moved into position with a large tracked excavator. |
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Some boxes were floated from the launching ramp and pushed into position using a workboat. The boxes were lined up end to end and sunk using removable plugs in the walls of the boxes. |
Pilings were then driven in alongside the breakwaters to mark them and provide an ice and storm resistant foundation for piers.
Sand can be seen accumulating behind the breakwaters in a “tombolo” shape, or series of small bays with sand, eventually reaching out to the landward side of the breakwaters as they fill in over the next several years. The boxes, each weighing six or more tons empty, can resist the great force of winter storm driven waves and absorb their energy, allowing the sand that the waves are carrying to settle out behind the breakwaters.
The open boxes also act as aquariums allowing sub aquatic vegetation a calm bed to attach and grow, creating a nursery for fish and crabs to flourish in this high energy area of the river.
The two series of pictures below show a time lapse from two angles showing the sand accretion of the “Tombolos” behind the breakwaters since their completion in April 2005.
| River View | High View |
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