News Stories

High river flows on Cape Fear River stalling work on scour hole at Lock and Dam 2

Published Dec. 21, 2018

While the Wilmington District is deciding whether to transfer or keep the Cape Fear River Locks and Dams during the Cape Fear River Disposition Study, maintenance repairs to all three are still required to ensure public safety and keep them in good operating condition. But flood waters from Hurricanes Florence and Michael, as well as high-precipitation weather patterns have inundated the Cape Fear River basin over the past several months, hampering efforts to repair damage to at least one of the facilities. 

   At Lock and Dam 2, turbulence from water flowing over the dam created a scour hole downstream of the dam.  Without repairs, the scour hole could continue to encroach on the toe of the dam and could ultimately threaten its structural integrity.  However, repairs have been indefinitely delayed because of inconsistent river flows. The contractor was at least 75 percent completed with the scour hole repair before Hurricane Florence.    

   "The scour hole is a dam safety-related repair that must be completed to ensure the integrity of the dam," explained Wilmington District Shallow Draft Navigation Program Project Manager Jim Medlock. "The repairs involve using heavy equipment plus on-site storage and placement of quarry rock into the scour hole."

   Before the flooding, the contractor designed and built a temporary ramp that he used to drive large off-road dump trucks, loaded with rock, onto a series of barges which were then pushed by a tug to the scour hole location.  Once the barge reached the scour hole, the truck deposited the rock in the scour hole and returned to get loaded again. 

   “While the truck mounted barge travels to and from the shore rock stockpile, a long-reach excavator, mounted on another barge, repositions the rock in the scour hole to the final design grade,” said Project Engineer Rolando Serrano.  “The long reach excavator is equipped with GPS that assists the operator in placing the rock at the correct location and proper depth.  Hydrographic surveys are used to confirm the rock is correctly placed.”

   To date, the work site is still experiencing flood conditions resulting from other multiple upstream rainfall events which continue to hamper the contractor from effectively restarting and completing the project.  Once flooding subsides, the Corps will work with the contractor to establish a new completion schedule and completion date.