Section 1 Introduction - National Marine Fisheries Service - NOAA

NBK at Bangor EHW-1 Pile Replacement Project Final Marine Mammal Monitoring Report
Section 3 Results
Acoustic Results
In general, underwater and airborne sound measurements collected at the WRA vessel, provided
the best acoustic data for construction. However, sound measurements were taken in multiple
locations inside and outside the WRA, and the distances to various sound thresholds for marine
mammals were calculated using data from all available sources. Only sound levels recorded at
the mid-distance (WRA vessel) and distant (raft and mid-channel vessel) locations are presented
in this report. For more detailed sound pressure level results please see NAVFAC 2012. In
some cases data was not available from the vessel-based sound sensors because of equipment
failures/damage, transportation issues, timing limitations, environmental conditions, or
communication system failures; in these cases, sound thresholds were calculated based on other
sensors located inside and outside the WRA.
Vibratory Pile Driving: Acoustic Results
Typical vibratory pile driving during the EHW-1 resulted in sound levels that varied
considerably through the driving periods. Vibratory sounds underwater were characterized by
the measurement of RMS sound pressure levels. During the EHW-1 PRP there were 28
permanent steel pipe piles (12 at the walkway and 16 at Bents of the EHW-1 structure) and 8
temporary steel falsework piles which were installed using a vibratory hammer. In addition, two
24-inch steel fender piles and eight 12-inch steel fender piles were removed using a vibratory
hammer and/or dead pull. Vibratory pile installation/removal occurred on 14 days between
Oct 5 – 27 th . Vibratory installation occurred during parts of all of the 14 days, whereas vibratory
extraction only occurred on portions of two of the days. During the installation/removal of an
individual pile there were occasionally multiple vibratory recording events as a result of the pile
driver being temporarily shutdown or the pile requiring additional driving at a later time. In total,
65 vibratory driving events (i.e., installation or removal of piles) were measured. Actual
vibratory pile driving events during the EHW-1 lasted from less than 0.5 minutes to almost 41
minutes, and the duration of vibratory extraction events ranged from 3 minutes to 32 minutes per
pile. The total duration of all vibratory driving and extraction events over the course of EHW-1
PRP was 13:52:23 (vib in 12:11:36, vib out 1:40:47) (see Table 3). Table 4 presents a summary
of the average RMS sound pressure levels measured at the WRA boat and the estimated distance
to the 120 dB behavioral harassment threshold for cetaceans and pinnipeds. On average, the
WRA-boat sound level was 158 dB RMS (re: 1µPa) for piles less than 30-inches in diameter and
154 dB RMS (re: 1µPa) for 30-inch diameter piles. The maximum event level recorded at this
location from all driving was 168 dB RMS (re: 1µPa). The maximum sound pressure level
recorded approximately 10 meters from the pile, was 174 dB RMS (re: 1µPa) (NAVFAC 2012).
The average sound pressure level for all 30-inch permanently installed piles, using a 10 second
integration period, was 166 dB RMS (re: 1µPa) at 10 meters. Sound pressure levels were
generally lower during the installation of falsework piles, which were slightly smaller (16–inch
diameter), or the vibratory extraction of piles. For environmental compliance documents for the
EHW-1 PRP, the near-source level used for consultations was 168 dB RMS (re: 1µPa) at 10
meters. Based on the data recorded during the EHW-1 PRP, the near-source levels used in the
consultation process were close or only slightly conservative compared to the recorded levels..
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