Section 1 Introduction - National Marine Fisheries Service - NOAA

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NBK at Bangor EHW-1 Pile Replacement Project Final Marine Mammal Monitoring Report Event Description Pile Coordinates Start Time Stop Time Sensor Measured Sound Pressure Level - RMS (WRA Boat) Ave Max Calculated distance to 120 dB RMS (m) Date: 10/21/2011 (continued) W-3 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 15:37:01 15:39:51 Mid Down 821 W-4 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 16:00:34 16:11:39 Mid Down 143 145 153 154 5,246 W-5 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 16:13:55 16:16:47 Mid Down 150 150 153 155 5,199 W-6 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 16:18:14 16:21:54 Mid Down 151 153 154 155 5,643 Date: 10/27/2011 W7 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 9:55:24 10:03:08 Mid Down 160 161 South ± 7,000 (Land) North ± 13,000 (Land) W9 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 10:05:17 10:08:51 Mid Down 151 154 South ± 7,000 (Land) North 10,400 W12 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 10:12:52 10:18:33 Mid Down 152 156 South ± 7,000 (Land) North 12,000 W11 - REVIB Lat. Long. 47° 45.199' 122° 43.448' 10:21:04 10:26:12 Mid Down 153 157 South ± 7,000 (Land) North ± 13,000 (Land) EX3 Lat. Long. 47° 45.199' 122° 43.448' 11:24:13 11:25:58 Mid Down 145 146 147 147 4,706 EX4 Lat. Long. 47° 45.199' 122° 43.448' 11:28:00 11:28:14 Mid Down 139 140 148 148 4,566 EX3 - Cont. Lat. Long. 47° 45.199' 122° 43.448' 11:31:00 11:31:18 Mid Down 142 143 142 144 2,754 EX5 Lat. Long. 47° 45.199' 122° 43.448' 11:49:48 11:52:38 Mid Down 128 128 152 151 South ± 7,000 (Land) North 8,800 EX6 Lat. Long. 47° 45.199' 122° 43.448' 11:58:49 12:02:13 Mid Down 128 129 151 150 South ± 7,000 (Land) North 7,700 Notes: 1 Pile was not driven. Hammer was setup on a permanent pile inside EHW-1, however, due to space limitations as a result of the tidal elevation the hammer could not be turned on and no pile driving occurred on October 4th; A RMS Sound levels during vibratory driving analyzed in 10 sec periods "Max" is the maximum level for any 10 second period "Avg" is the average of the 10 second periods over the duration of the pile driving event. B Based on best available data for each pile driving event Prior to the EHW-1, the 120-dB behavioral disturbance zone for vibratory driving sounds was predicted to extend out along the main channel about 13,840 meters north to Squamish Harbor and about 6,760 m south to Toandos Peninsula. During the EHW-1 PRP, levels exceeding the 120 dB RMS isopleth were measured at distances out to 3,995 m, where the level was 125 dB RMS (re: 1µPa). However, there were measurements closer than 3,995 m where sound levels did not exceed 120 dB RMS (re: 1µPa). The data collected during the EHW-1 cannot accurately pinpoint a single distance which would estimate the extent of the 120-dB harassment zone, because of the large variability in measured sounds from drive to drive and the extensive size of the area. The data do, however, indicate that levels were not louder than those predicted for the project. Although most measurements were made within the zone predicted to have levels above 120 dB, the measurements made outside of the zone had levels less than 120 dB. Using the Bangor, Washington 26
NBK at Bangor EHW-1 Pile Replacement Project Final Marine Mammal Monitoring Report average WRA boat measured level and the average propagation rates from measured vibratory sound levels for all piles, the calculated distance to the 120-dB ranged from 821 to 13,000 m (Table 4). Sound levels during soft starts were typically lower than those levels at the initiation and completion of continuous vibratory driving. However, levels during continuous driving varied considerably and were at times lower than those produced during the soft starts. It is difficult to assign a level that describes how much lower the soft start sound levels were than continuous levels. The APE 200-6 vibratory hammer was used to install and remove all piles. Table 5 summarizes the difference between the modeled and actual harassment sound thresholds for vibratory pile driving. As stated previously, the maximum underwater sound levels recorded at 10 meters from the pile was 174 dB RMS (re: 1µPa) and the average was 166 dB RMS (re: 1µPa). Using the average SPL and assuming practical spreading loss (15LogR), the source levels produced from vibratory driving were below the injury threshold for both cetaceans (180 dB) and pinnipeds (190 dB), therefore there was no risk of injury to any marine mammal during pile driving and removal events associated with the EHW-1 PRP. Even using the maximum SPL produced, the source level of pile driving were always less than 190 dB RMS, and the maximum distance to the 180 dB RMS isopleth would have been less than 4 meters from the pile. Since no cetaceans ever approached or entered within the WRA (over 500 meters from the pile) there was still no risk of injury to cetaceans even if the sound pressure levels exceeded the 180 dB RMS isopleth on occasion. Table 5. Modeled and Measured Marine Mammal Behavioral Harassment RMS Sound Level Thresholds for Vibratory (120 dB) Pile Driving Threshold Airborne Sound Modeled Distance (Average, m) Measured Distance (Average, m) 120 dB 10,300 † 4,396 † Average of predicted thresholds to the North (13,840 m) and South (6,760 m) in Hood Canal Airborne measurements were taken using two microphone systems placed along the shoreline on the north and south (removed 7 October 2011) of the project site; also, one microphone was placed on a vessel within the WRA. No injury thresholds exist for marine mammals exposed to airborne sound, and no behavioral harassment threshold exists for cetaceans exposed to airborne sound. The behavioral harassment thresholds for pinnipeds are 90 dB RMS re: 20 µPa (harbor seals only) and 100 dB RMS re: 20µPa (all other pinnipeds). Summaries of RMS sound levels at these locations, and associated threshold distances, are shown in Table 6. Prior to the initiation of the EHW-1 PRP, the distance to the 100 dB (unweighted) airborne harassment zone for vibratory pile driving was predicted to extend 9 m from the pile. Based on the measurement of average RMS Leq levels and applying a 20 Log10 propagation rate, the harassment zone was 10 m from the pile for all pile sizes. Likewise, the distance to the 90 dB (unweighted) harassment zone for harbor seals was predicted to extend 28 m from the pile. Based on the measurement of average levels and applying a 20Log10 propagation rate, the actual harassment zone was 33 m for all pile sizes (Table 7). Bangor, Washington 27
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Section 1 Introduction - National Marine Fisheries Service - NOAA

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