Marine Construction Technologies: Creating an acoustic barrier to save marine wildlife
Story by Clare LaFond
Photos & video by Conrado Tapado (except where noted)
As the second largest estuary in the U.S., the Puget Sound is home to a variety of marine wildlife, including orcas, sea lions and harbor seals. Its glacier-carved channels fed by rivers and streams flow into the bays of the Sound, where more than 200 species of fish flourish.
The region is also home to millions of people who actively enjoy its tremendous natural beauty – and who count on the construction of bridges, docks and ferry terminals to take them where they need to go. But the harm this loud underwater construction can cause to marine wildlife and their habitats is the reason current federal laws allow for only six months of aquatic construction in the Puget Sound annually. It’s a tight timeframe that can translate into higher construction costs as longer term projects are drawn out and delayed.
That’s where new UW start-up Marine Construction Technologies comes in – with a plan that could soon prove to be a viable solution to turning down the volume on loud aquatic construction activity, instead creating harmony between nature and necessary progress.
Led by UW Mechanical Engineering Chair, Per Reinhall, the new start-up was born out of a competition put forth in 2008 by the Washington State Department of Transportation (WSDOT), titled “Experimental Design for Noise Attenuation for Pile Driving.”
Piles are long, slender steel tubes that are driven into the seabed to support structures that become bridges, piers, docks and other types of marine construction. As a pile is hammered into the seabed floor, it expands, sending out sound waves through the surrounding water and down into the seabed. The resulting sound, both above ground and underwater, can harm sensitive aquatic birds and kill fish and marine mammals.
“When the pile is struck, the sound propagates out as a shockwave in the water and sediment,” Reinhall explained. These manmade sound waves can drown out the noises that fish and marine mammals depend on to survive, causing serious injury and even death. It’s a problem that extends well beyond the Pacific Northwest, to fragile marine ecosystems across the country and around the globe – anywhere aquatic wildlife and marine construction intersect.
WSDOT, which has long studied the ill, often fatal, effects of pile driving on marine wildlife, decided to create a competition to encourage engineers from both industry and academia to come up with a solution.
Together with Peter Dahl, UW professor of mechanical engineering and principal engineer at UW’s Applied Physics Lab, Reinhall wrote a proposal introducing new pile design technology — and the two won the competition. This, in turn, led to the establishment of a long-term, WSDOT-funded research program focusing on the attenuation, or reduction, of sound from pile driving.
“Thanks to the generous support of WSDOT, we were able to develop an understanding of the exact mechanisms of why pile driving is so loud,” Reinhall said, “and how the sound is transmitted in the water.”
In 2011, C4C awarded the researchers $50,000 in Commercialization Gap Funding to help move the technology forward and ensure the design modeling was correct. In partnership with the Washington Research Foundation, C4C provides up to $1 million per year of gap funding to help new technologies get across the “valley of death” between the conclusion of academic research grants and the level of development at which they can attract seed stage investment.
Dave Marver, a local entrepreneur who currently serves as CEO of two other UW start-ups, Spark Medical and JointMetrix Medical, said there were a couple of UW professors he’d always wanted to work with, based on the research they were doing and the high probability that the technology could be commercialized.
“And Per was one of them,” he said. In 2012, Marver approached C4C about licensing the new pile design technology for commercialization. And, soon thereafter, UW start-up Marine Construction Technologies was born.
Marver, who is the Chair and Chief Marketing Officer of Marine Construction Technologies, brought in engineering and construction expert Alex Staley to serve as its CEO.
“This is about looking at a new way to advance an old industry,” Reinhall said.
The UW team started out with a steel pipe that fully enclosed the pile in the water. As the pile was driven into the seabed, the steel pipe enclosing it blocked all sound that spread out through the water, but the overall noise reduction was lower than expected. Studying the results, Reinhall and Dahl made a landmark discovery: the sound was also spreading up through the seabed floor.
“It turned out it was not enough to surround the pile with the steel pipe in the water as a sound shield, since the sound waves were still able to travel up through the seabed,” he said.
To reduce this noise, Reinhall and his team next came up with a double-wall pile concept, in which one pile is placed inside another with an air gap in between the two. The two piles are connected at the bottom with flexible coupling. During construction, only the inside pile is struck and no noise is produced by the outside pile – a result that significantly decreases the overall pile driving noise.
It’s a novel design that can reduce noise from impact pile driving by more than 20 decibels (dB). As a reference point, existing noise reduction techniques for marine pile driving — such as bubble curtains placed in the water to help absorb underwater sound waves — tend to produce only a 3 dB reduction.
Tim Dardis, a UW Mechanical Engineering graduate student and part of Reinhall’s research team, has worked on computer modeling of the new prototype, as well as the actual construction of the piles in the department’s Machine Shop. The new design, he explained, is all about effectively reducing the sound at its source.
“One way to think of it is you’re at a rock ‘n roll concert that’s too loud so you put on ear muffs,” Dardis said. “But another way to lower the sound is to turn down the band’s amplifier. And that’s essentially what we’re doing with our double pile – we’re just turning down the amplifier of the rock ‘n roll band.”
The UW team will conduct the first full-scale field tests of the new pile design this summer in Tacoma’s Commencement Bay with generous support from the Port of Tacoma. The study will be funded by WSDOT and the National Oceanic and Atmospheric Administration (NOAA), with monitoring assistance from the National Marine Fisheries Service.
“This innovation promises significant environmental and economic benefits for marine construction projects,” Reinhall said, “and we have several future concepts in mind that have the potential to improve performance even further.”