NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
would be operated to ensure that the sound field at these sites would not exceed 145 dB, adding an additional level
of protection for marine mammals located in dive sites.
Based on the operations of the HF/M3 sonar during missions the Navy conducted between 2002 and 2006, the HF/M3
sonar appears to effectively detect marine animals within 1 to 2 kilometers of the LFA projectors. Recent testing of
the HF/M3 sonar demonstrated a probability of single-ping detection above 95 percent within the LFA mitigation zone
for most marine mammals (Navy 2005). For example, during seven of the nine SURTASS LFA missions the Navy
conducted in 2004, there were twelve HF/M3 alerts that were identified as possible marine mammal or sea turtle
detections. Between February 2005 and February 2006 LFA transmissions were delayed or suspended on 33
occasions: operations on the USNS IMPECCABLE were delayed or suspended four times because of possible marine
mammal or sea turtle detections and three times due to HF/M3 failures while operations on the R/V Cory Chouest
were delayed or suspended 12 times because of possible marine mammal or sea turtle detections, 13 times because
the HF/M3 system failed, and once because of a visual sighting of dolphins.
Thus far, the combination of geographic constraints, operating protocols, monitoring measures, and shut-down
procedures appear to have prevented most threatened and endangered species of marine mammal and sea turtles
from being exposed to SURTASS LFA sonar at received levels exceeding 180 dB. Further, they have prevented these
species from being exposed in areas that are critical to their ecology, critical to large portions of their populations, or
both. The Navy proposes to continue using these measures and they are likely to perform as well in the future as they
have performed thus far. Therefore, based on the evidence available, most marine animals are likely to be exposed to
received levels of LFA sonar at or below 180 dB.
DURATION OF POTENTIAL EXPOSURE TO SURTASS LFA TRANSMISSIONS. Between the third week of January 2009 and
mid-August 2009, the Navy proposes to conduct 3 missions with the SURTASS LFA sonar system in the Hawai'i
Range Complex, with 7 days active during each mission and 24 hours of operations per day. The duration of a
typical SURTASS LFA ping would range from 6 to 100 seconds, with no more than 10 seconds at a single frequency;
intervals between pings would range from 6 to 15 minutes. Pings would consist of various signal types that vary in
frequency (between 100 and 500 Hz) and duration (including continuous wave and frequency-modulated signals).
When the system is turned off, no additional energy would enter the ocean’s environment.
The duration of an animal’s exposure to SURTASS LFA signals would depend on the animal’s proximity to the
transmitter and the animal’s location in the water column. Nevertheless, because of the length of individual pings,
individual animals are likely to be exposed to SURTASS LFA transmissions for periods ranging from 6 to 100 seconds.
MITIGATION MEASURES TO MINIMIZE THE LIKELIHOOD OF EXPOSING MARINE MAMMALS TO LFA SONAR. The Navy
proposes to use a monitoring program to avoid potentially exposing marine mammals to LFA transmissions at high
decibel levels. As discussed in the Description of the Proposed Action, this monitoring program includes visual,
passive acoustic, and active acoustic monitoring of a 180 dB mitigation zone and an additional 1 km buffer zone.
The effectiveness of visual monitoring is limited to daylight hours, and its effectiveness declines during poor
weather conditions. In line transect surveys, the range of effective visual sighting (the distance from the ship’s track
or the effective strip width) varies with an animal’s size, group size, reliability of conspicuous behaviors (blows),
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