IISG comment to SEIC 24 June 06

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Comment by Independent Scientists concerning SEIC’s Detailed Response to the IISG Report From: Alexander Vedenev, Doug Nowacek, Tim Ragen and Randall Reeves 24 June 2006 Item No. 40: (A) Mother/calf pairs are known to feed in water shallower than 10 m; (B) Using 10 m as a standard is not “conservative” because sound levels at 10 m depth are not generally higher than they are at the bottom. Although this can vary, it is usually vice versa; (C) Acoustic measurements are always taken near the sea bottom (as indicated in Fig. 3.1 of SEIC Document 13F_MNR_Report_Acoustic_Volume_2_2005.pdf) but JASCO’s modeled sound levels relate only to 10 m depth. The modeled data therefore need to be recalculated for comparison to received (empirical) values obtained at positions where the water depth is other than 10 m. Such comparisons would be informative and should be done. Item No. 41: To clarify, the IISG suggested a single, simple criterion based on a noise “dose” approach, which attempts to account for duration of exposure and not just level. We proposed a procedure that would use PEL dB as the control unit (PEL = Permitted Exposure Level), derived from RMS of sound pressure (dB) averaged over time (T). This supposes an equal acoustic impact using a 5 dB exchange rate, Q (from the U.S. Occupational Safety and Health Administration or OSHA). In the common case: PEL (T) dB = PEL (T ) dB - Q/3 T dB, ref * Where Q= 5, T dB = 10 log (T / T ), ...

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• Publié par: Seah
• Nombre de lectures: 167
• Langue: English

Extrait

Comment by Independent Scientists concerning SEIC’s Detailed Response to the IISG

Report

From: Alexander Vedenev, Doug Nowacek, Tim Ragen and Randall Reeves

24 June 2006

Item No. 40:

(A) Mother/calf pairs are known to feed in water shallower than 10 m; (B) Using 10 m as

a standard is not “conservative” because sound levels at 10 m depth are not generally

higher than they are at the bottom. Although this can vary, it is usually vice versa; (C)

Acoustic measurements are always taken near the sea bottom (as indicated in Fig. 3.1 of

SEIC Document 13F_MNR_Report_Acoustic_Volume_2_2005.pdf) but JASCO’s

modeled sound levels relate only to 10 m depth. The modeled data therefore need to be

recalculated for comparison to received (empirical) values obtained at positions where

the water depth is other than 10 m. Such comparisons would be informative and should

be done.

Item No. 41:

To clarify, the IISG suggested a single, simple criterion based on a noise “dose”

approach, which attempts to account for

duration

of exposure and not just level. We

proposed a procedure that would use PEL dB as the control unit (PEL = Permitted

Exposure Level), derived from RMS of sound pressure (dB) averaged over time (T). This

supposes an equal acoustic impact using a 5 dB exchange rate, Q (from the U.S.

Occupational Safety and Health Administration or OSHA).

In the common case:

PEL (T) dB = PEL (T

ref

) dB - Q/3

*

T dB,

Where Q= 5, T dB = 10 log

10

(T / T

ref

),

T

ref

= 60 min, PEL (T

ref

) =

130 dB, T

trans

= 15

min (5 and 3 min during 1 hour, to take into account transient noise), T

max

= 240 min (T

has limit because PEL(T

max

) =120 dB lowest level for negative effect on whales).

In the IISG Report, Table 1 (page 20) corresponds to the expression: PEL(dB) = 130 - 5/3

*10 log10 (T / 60), where time of exposure T is given in minutes.

The OSHA uses a 5 dB exchange rate. The U.S. Navy uses a 4 dB exchange rate. The

U.S. Army and Air Force use a 3 dB exchange rate. The National Institute for

Occupational Safety and Health

(

NIOSH) recommends a 3 dB exchange rate.

Note that the equal-energy rule is based on a 3 dB exchange rate. However, the most

recent scientific data (2005) indicate that the equal-energy rule

is incorrect for animals.

For example:

•

For cats it has been shown that the EEH (equal-energy hypothesis) is not

confirmed in case of an equivalence index of 3 (exchange rate)

(

http://elib.sci.am/2005_4/14/14.htm

).

•

For pinnipeds (California sea lion, harbor seal, northern elephant seal), in some

cases doubling the exposure duration for a 3 dB increase in sound exposure level

had a greater effect on threshold shift than an transient increase of 15 dB in

exposure level (D. Kastak et al, “Underwater temporary threshold shift in

pinnipeds: Effects of noise level and duration”, JASA, 18, 5, 2005

<http://www.nmfs.noaa.gov/pr/pdfs/acoustics/noise_pinnipeds.pdf

SEIC agreed to this 5 dB exchange when they adopted the time-level-exposure criteria

for levels of 130 and 140 dB, so we are not arguing for a different standard than was

agreed upon in Vancouver in April 2006, simply that the criteria be applied equally at all

levels.

We reiterate that noise exposure can elicit negative reactions other than, or in addition to,

avoidance alone. The principle stands that corrective action should be taken when gray

whales have been exposed for 4 continuous hours to received levels of 120 dB re 1uPa.

As read (SEIC response to Item 41), it appears that SEIC does not intend to implement

measures according to this principle because: (a) it would make completion of the

pipeline construction activities in one season impossible, (b) any individual whale can be

assumed to be moving and therefore would be unlikely to remain in an area with that

level of sound for that length of time, and (c) “avoidance” is the only response of concern

(recognizing that this may be related causally to reason b, above).

Item 50:

We remain dubious about the radio link to the buoys, i.e., this system’s ability to convey

necessary information about noise levels. Assuming the ARBs still have only a 35 dB

dynamic range and that the bottom of this range is set to 110 dB, then any noise >145 dB

cannot be measured accurately, and considering the exposure dosage approach (see

above), even very short bursts of noise at these levels are likely to cause disturbance to

the whales.

Item 52:

We do not recall being informed that buoys would be placed at the 10 m contour. This is,

however, welcome news as such placement would be a good addition to the process.

.