Impact pile driving in marine environments poses a real risk to fish and marine mammals. Managing that risk in real time across active construction is the work of hydroacoustic monitors and marine mammal observers.
Impact pile driving for marine jetty construction generates underwater sound pressure that can injure or kill fish and disturb marine mammals at significant distances from the source. Managing this requires continuous monitoring and a clear stop-work framework.
Most people watching a construction barge from shore have no idea what is happening beneath the waterline. The hammering they might faintly hear carries far louder through water than through air. Unlike on land, the animals in the path of that sound have nowhere obvious to go.
Impact pile driving is the process of hammering steel piles into the seabed to anchor marine structures. It generates pressure waves powerful enough to kill fish outright, rupture internal organs, or permanently damage hearing at distances that would surprise most people. The work happens out of sight, which is exactly why someone needs to be listening.
On BC’s north coast, that responsibility falls to hydroacoustic monitors and marine mammal observers — and Wai Wah Environmental (WWE) has built the capacity to field both.
WWE provides hydroacoustic monitoring and marine mammal observer services on major in-water construction projects on BC’s north coast. The scale of this work is not small. At one recent port terminal project, up to two piling barges operated simultaneously, each requiring its own dedicated crew of hydrophone monitors and marine mammal observers working 12-hour shifts across a continuous construction window.
Calibrated hydrophone arrays were deployed at two depths within 10 metres of each active pile, with a third hydrophone monitoring the outer marine mammal exclusion zone. Sound pressure levels were recorded continuously against DFO-recommended thresholds.
The hydroacoustic work is precise and important. WWE deployed calibrated vertical hydrophone arrays at two positions relative to each active pile — one at mid-water column and one two metres off the seabed, both within 10 metres of the pile — with a third hydrophone at the outer exclusion zone boundary.
Sound levels were tracked in real time and compared to Fisheries and Oceans Canada guidelines for fish safety. A yellow alert gave the crew an early warning to reduce noise by adjusting bubble curtains or reducing hammer force, before a red alert required stopping work right away. The cetacean behavioural disturbance threshold was monitored simultaneously at the outer exclusion zone boundary.
The cetacean exclusion zone started at 1,000 metres from the pile. That is a circle two kilometres across, continuously monitored every shift for the duration of active piling.
The marine mammal monitoring layer ran in parallel. In the waters around the project site, the species of concern included northern resident and Bigg’s killer whales , both listed as threatened under the Species at Risk Act; humpback whales and Steller sea lions , listed as special concern; and harbour porpoises, Dall’s porpoises, Pacific white-sided dolphins, and harbour seals.
Before any piling could start, WWE’s marine mammal observers watched the full exclusion zone for 30 minutes, as long as visibility was clear. Work began only after they confirmed there were no marine mammals in the area.
A 30-minute clear pre-scan of the full exclusion zone was required before each impact piling event. If a marine mammal was sighted within the zone at any point during active piling, work stopped immediately and could not resume until the animal was observed to exit or 30 minutes had elapsed since the last confirmed sighting.
WWE’s marine monitors work as an integrated part of the construction team. When sound levels approach a threshold, the response is collaborative — adjusting hammer force, assessing attenuation devices, or modifying the approach before a shutdown becomes necessary
Marine environmental monitoring at this scale is not performed by a single technician with a notepad. It requires coordinated teams of hydrophone monitors, lead MMOs, boat-based observers, and environmental monitors with stop-work authority, working in real time, in all weather, and communicating with each other and the construction management team.
WWE has built that capability and built it locally. When the coast you are monitoring is the coast you are from, the work means something different.
WWE Environmental supports in-water construction projects through hydroacoustic monitoring, marine mammal observation, and environmental compliance services across BC’s north coast. To learn more, visit our services page.
