Dredging the deep seabed for danger

Engineer/hydrographic surveyor Emeline Veit spends half the year living and working on a 100 m offshore vessel.
Engineer/hydrographic surveyor Emeline Veit spends half the year living and working on a 100 m offshore vessel.

Controlling dredge pumps to uncover unexploded ordinance on a seabed or to collect enough sand to build an island requires experience and high quality performance. Here we look at the role of one engineer in dredging projects around the world. 

The engineer/hydrographic surveyor Emeline Veit spends half the year living and working on a 100 m offshore vessel tracking underwater bombs, creating nautical charts, and building islands. Veit’s office is a 35-crew off-shore vessel. Her role is significant. While in the North Sea, it is her job to find unexploded ordinance (UXOs), which are explosive weapons like bombs, shells, grenades, land mines, naval mines, cluster munition, etc., that did not explode when they were employed and still pose a risk of detonation, sometimes many decades after they were used or discarded. “My job depends on the project,” she said. “What I did in the North Sea is really special. I looked for UXOs, which are bombs leftover from the second World War. In the North Sea they are building many wind farms. On the cable routes and wind farm locations we must be sure we don’t have potential UXOs if they are piling for a wind turbine or dredging for the export cables. If they encounter a bomb it can destroy everything. The offshore wind power companies require that we look for them and remove them.” In the North Sea, there are still many of them, she said. Experts report that there are approximately 1.6 million tons of these explosive remnants of war still buried below. A global scan is performed with a magnetometer, which provides a list of targets. Then remotely operated vehicles (ROVs) are deployed. ROVs are underwater robots that are operated by two pilots onboard the main vessel. Veit is the navigator. “It’s kind of like an underwater drone, but it’s huge, about 3 m x 2 m,” Veit explained. “I’m in charge of all the equipment on the ROV. I sit on the vessel bridge so I can see everything. The pilots are sitting in a room with screens that looks like an aircraft control room. We communicate through an intercom. I’m in charge of the positioning of the ROV and all the equipment on them. We first locate the precise target based on the readings. I give them the coordinates. It’s my job to create the charts.” Dredge pumps Onboard the offshore vessel all the subsea positioning is her responsibility. “GPS doesn’t work underwater,” she said. “It’s my job to locate what is underwater.” When a potential UXO is located, most of the time it is covered by sand. A dredge pump is used to begin the cleaning process. Sometimes a wheel is uncovered and sometimes a huge sea mine is discovered. High resolution photos are taken, and reports are written.  “Depending on the countries where we work there is different legislation required,” she explained. Each country’s UXO Navy Services are often in charge of demolitions. “We are in no danger at all,” she said. “Once it is clear, then we go and find another one. We are kind of like fishermen hunting for fish. We are fishing for bombs.” When preparing to build a wind farm, there are cables between each wind turbine. A trench must be built in the sea bed for the cables, which are then covered with sand and rocks. With various tools, a 3D map can be made of the sea bed. Veit creates the charts and drawings.  “When I began working I was working on dredging projects onshore,” she explained. “We would use dredges to deepen channels and build land reclamations, like the islands in Dubai and huge construction projects like airports. I did this for two years, mapping, drawing, and making calculations for these types of projects.” Building islands When building an island, for example, first there must be a drawing, Veit explained. “Then, you have to get the sand from somewhere, so we use big dredges with large powerful pumps and engines able to suck sand, clay, silt, and gravel. On the side of the dredger one or two suction pipes descend to the bottom of the sea bed. It is comparable to a large hoover. It is trailed along the sea bed. In the head of these suction pipes, a system connected to a high-pressure water installation is capable of loosening the material on the sea bed. 

The material will be then sucked in the pipe and discharged in the hopper. When they are full, there are different ways of discharging the hopper. One of them is to go back to the shore and connect to a pipe, and then pump out a mixture of the material and water which goes all the way through the pipe to the land reclamation center. Then they bring in bulldozers and cranes and all kind of equipment and make an island.”

Veit calculated how much sand was dredged at sea in volume and how much was put on land in volume. The levels must meet the specifications of the design of the island or the channel. “I would go to sea in a little boat and do a 3D mapping of the sea floor,” she explained. “I then made a drawing and computed all the volumes and then we could show the clients all the calculations. Projects like this can take one to six years or more to complete.”

“I always I wanted to do something with the ocean,” said Veit. “I chose an engineering school in Brest because all the engineering specialties they were offering were linked to the ocean.”

The first assignments for Veit were in Korea and Africa and this created challenges for the recently-graduated engineer. “I was sent to the site in Gabon, Africa (on the western Atlantic coast) because they speak French there,” Veit said. “Being a young engineer in Africa was difficult. I felt like I was always having to prove myself twice. I was on these construction sites with these big tough guys. I was out there taking measurements and having to collaborate with the men every day. It was a tough environment. I was only 22 years old.”

Now, Veit fits right in with the others onboard the offshore vessel. With experience and high-quality performance, she has earned their respect.  “When I’m living on the huge 100 m offshore vessel, it feels huge,” she said; when the work finishes Veit moves to her floating home a 12.5 m sailboat on which she and her husband sail the world. Last year, Emeline Veit spent only 10 days on dry land. She wouldn’t have it any other way.