Section 1 Introduction - National Marine Fisheries Service - NOAA

NBK at Bangor EHW-1 Pile Replacement Project Final Marine Mammal Monitoring Report
addition, a number of California sea lions hauled out on the floating security fence before, during
and after pile driving. In summary, MMOs had the general impression that neither harbor seals
nor California sea lions were adversely affected by the pile driving activities at the EHW-1 PRP.
Some animals were observed diving at the initiation of soft start, reemerging further away and
continuing their movements. Multiple-week observations of two individual harbor seals
suggested that these animals were drawn to the area by curiosity and did not appear to be
repelled by marine noise or construction-related activities.
Section 4 Recommendations
1. Observational data collected during the EHW-1 PRP did not indicate any adverse
reaction of marine mammals to pile driving activities. The harbor seal, which is the
species that most heavily utilizes the WRA (in particular, the EHW-1 structure), did not
appear to be affected by construction as it often came in the closest to investigate
construction activities. Based on the observational data collected during the EHW-1
PRP, the standoff distances currently used for marine mammals may be overly
conservative (i.e., overestimated), especially given that vibratory pile driving does not
produce SPLs that would exceed the injury criteria within more than a few meters of the
pile. A smaller shutdown zone (e.g., 10 m [33 ft] rather than the 50 m [164 ft] used
during this project) should be utilized for future construction projects in this area. A
shutdown zone of 10 m (33 ft) would prevent direct interactions with marine mammals
and would be sufficient to avoid adverse behavioral reactions to pile driving activities. If
feasible, differentiate the shutdown zone for pinnipeds versus cetaceans, because the
acoustic criteria levels are different for these species, as is their use of the nearshore areas
(i.e., inside the WRA) at NBK at Bangor.
2. The 1-minute pauses in between soft start sounds employed during this project may have
been too long to send an effective warning to animals in the area. Longer breaks between
the sounds may be interpreted by the animals as transient noise and may not serve the
intended purpose of providing an indication that louder sounds from pile driving are
about to begin. It is recommended that noise bursts during soft start events occur at
30-second intervals and with increasing intensity, as done for seismic surveys Soft start
pauses should at least be shortened to 30 seconds, even if SPLs remain the same
throughout soft start.
3. Due to the substantial effort and cost of monitoring the entire Hood Canal area, future
monitoring efforts might effectively be confined to the shutdown zone and adjacent areas
(i.e., inside the WRA fence) to document behavioral impacts to marine mammals.
4. Steller sea lion takes should be included in take permits for future construction projects in
Hood Canal.
5. Further detailed analysis of harbor porpoise density, abundance and habitat use should be
completed to provide updates to current available data.
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