SEATURTLE.ORGVisiting a Hopper Dredge
Last week, I had the opportunity to visit the Eagle 1, a hopper dredge that was collecting sand from the Morehead City port channel here in North Carolina. Doug Piatkowski, a biologist at the Army Corps of Engineers, invited me to tag along while he conducted a regular site-visit. The photo above is of one of the dragheads. The pointed far end of the draghead allows it to plow below the surface of the ocean floor, making it less likely that it will accidentally suck up a sea turtle. The material (largely sand and water) that is sucked up is dumped into the hopper in the middle of the boat (hence the name "hopper dredge"). The following photo shows the sand/water mixture coming out of the pipes into the hopper (holding container):
The sand/water mixture is dark because there are pockets of mud and other organic debris in the channel that is being dredged. All the material passes through screens that traps solid objects; these screens are regularly checked many times a day for anything out of the ordinary, including any sea turtles. You can see here that some trash and large shells have been trapped by one of the screens:
There are trained observers aboard the dredger so that 24 hours a day, there is someone keeping watch for any signs of incidental take of protected species (turtles, marine mammals, birds, etc.). So far, there have been no signs of any incidental takes (the cool water temperatures in the area right now mean that there are relatively few sea turtles around). If any takes are observed, there is a protocol in place to alert various people and shut down dredging activities until the situation can be properly assessed. The strategy of constraining the window of dredging to months with cool water temperatures combined with protected species observers has helped minimize sea turtle takes in North Carolina. Unfortunately, it is not always 100% effective, particularly in places where water temperatures remain warm year round and turtle are present (for example, in Florida).
The most amazing thing I saw on this trip was what the hopper dredge did when its hopper was full of sand. It stopped dredging, retracted its dragheads, and moved to a designated disposal area off of Bogue Banks. Then, it split open and allowed the sand to pour out of the bottom of the hull (note the crack at the far bottom of the hopper):
