50 CFR 217.204 - Mitigation.
(a) When conducting operations identified in § 217.200(a), the mitigation measures contained in the Letter of Authorization, issued under § 216.106 of this chapter and § 217.207, must be implemented. These mitigation measures are:
(1) Through monitoring described under § 217.205, the Holder of a Letter of Authorization will ensure that no marine mammal is subjected to a sound pressure levels of 190 or 180 dB re: 1 microPa or greater for pinnipeds and cetaceans, respectively. If a marine mammal is detected within or approaching a distance 200 m from in-water pile driving or in-water chipping, operations shall be immediately delayed or suspended until the marine mammal moves outside these designated zones or the animal is not detected within 15 minutes of the last sighting.
(2) If a marine mammal is detected within or approaching the Level B harassment zone designated for impact pile driving (350 m) prior to in-water impact pile driving, operations shall not commence until the animal moves outside this zone or it is not detected within 15 minutes of the last sighting.
(3) If a marine mammal is detected within or approaching the Level B harassment zone designated for vibratory pile driving (1,300 m) prior to in-water vibratory pile driving, operations shall not commence until the marine mammal moves outside this zone or it is not detected within 15 minutes of the last sighting.
(4) A start” technique shall be used at the beginning of each day's in-water pile driving activities or if pile driving has ceased for more than one hour to allow any marine mammal that may be in the immediate area to leave before piling driving reaches full energy. For vibratory hammers, the soft start requires the holder of the Letter of Authorization to initiate noise from the hammers for 15 seconds at reduced energy followed by 1-minute waiting period and repeat the procedure two additional times. If an impact hammer is used, the soft start requires an initial set of three strikes from the impact hammer at 40 percent energy, followed by a one minute waiting period, then two subsequent 3 strike sets.
(5) In-water pile driving or chipping shall not occur when conditions restrict clear, visible detection of all waters within the appropriate harassment zones or the 200 m safety zone. Such conditions that can impair sightibility include, but are not limited to, fog and rough sea state.
(6) In-water piles will be driven with a vibratory hammer to the maximum extent possible (i.e., until a desired depth is achieved or to refusal) prior to using an impact hammer.
(7) In-water impact pile driving shall not occur during the period from two hours before low tide until two hours after low tide.
(8) The following measures apply to all in-water pile driving, except during the “stabbing” phase, and all in-water chipping associated with demolition of the existing dock:
(i) No in-water pile driving (impact or vibratory) or chipping shall occur if any marine mammal is located within 200m of the hammer in any direction. If any marine mammal is sighted within or approaching this 200m safety zone, pile-driving or chipping must be suspended until the animal has moved outside the 200m safety zone or the animal is not resighted within 15 minutes.
(ii) If a group of more than 5 beluga whales is sighted within the Level B harassment isopleths, in-water pile driving shall be suspended. If the group is not re-sighted within 15 minutes, pile driving may resume.
(iii) If a beluga whale calf or group with a calf is sighted within or approaching a harassment zone, in-water pile driving shall cease and shall not be resumed until the calf or group is confirmed to be outside of the harassment zone and moving along a trajectory away from such zone. If the calf or group with a calf is not re-sighted within 15 minutes, pile driving may resume.
(9) If maximum authorized take is reached or exceeded for a particular species, any marine mammal of that species entering into the harassment or safety isopleths will trigger mandatory in-water pile driving shut down.
(10) For Port of Anchorage operated in-water heavy machinery work other than pile driving or chipping (i.e., dredging, dump scowles, tug boats used to move barges, barge mounted hydraulic excavators, or clamshell equipment used to place or remove material), if a marine mammal comes within 50 m, those operations will cease and vessels will reduce to the slowest speed practicable while still maintaining control of the vessel and safe working conditions.
(11) In the event the Port of Anchorage conducts out-of-water blasting, detonation of charges will be delayed if a marine mammal is detected anywhere within a visible distance from the detonation site.
(12) Additional mitigation measures as contained in a Letter of Authorization.