(a) When conducting the activities identified in Sec. 217.140(a), the mitigation measures contained in the Letter of Authorization issued under Sec. Sec. 216.106 and 217.148 of this chapter must be implemented. These mitigation measures include but are not limited to:
(1) Ice-covered Season:
(i) In order to reduce the taking of ringed seals to the lowest level practicable, BP must begin winter construction activities, principally ice roads, as soon as possible once weather and ice conditions permit such activity.
(ii) Any ice roads or other construction activities that are initiated after March 1, in previously undisturbed areas in waters deeper than 10 ft (3 m), must be surveyed, using trained dogs in order to identify and avoid ringed seal structures by a minimum of 492 ft (150 m).
(iii) After March 1 of each year, activities should avoid, to the greatest extent practicable, disturbance of any located seal structure.
(2) Open-water Season:
(i) BP will establish and monitor, during all daylight hours, a 190 dB re 1 [micro]Pa (rms) exclusion zone for seals around the island for all activities with sound pressure levels (SPLs) that are expected to exceed that level in waters beyond the Northstar facility on Seal Island.
(ii) BP will establish and monitor, during all daylight hours, a 180 dB re 1 [micro]Pa (rms) exclusion zone for cetaceans around the island for all activities with SPLs that are expected to exceed that level in waters beyond the Northstar facility at Seal Island.
(iii) If any marine mammals are observed within the relevant exclusion zone, described in Sec. 217.144(a)(2)(i) or (a)(2)(ii), the activity creating the noise will shutdown or reduce its SPL sufficiently (i.e., power down) to ensure that received SPLs do not exceed those prescribed SPL intensities at the affected marine mammal. The shutdown or reduced SPL shall be maintained until such time as the observed marine mammal(s) has been seen to have left the applicable exclusion zone or until 15 minutes have elapsed in the case of a pinniped or odontocete or 30 minutes in the case of a mysticete without resighting, whichever occurs sooner.
(iv) The entire exclusion zones prescribed in Sec. 217.144(a)(2)(i) or (a)(2)(ii) must be visible during the entire 30-minute pre-activity monitoring time period in order for the activity to begin.
(v) BP shall employ a ramp-up technique at the beginning of each day's in-water pile driving activities and if pile driving resumes after it has ceased for more than 1 hour.
(A) If a vibratory driver is used, BP is required to initiate sound from vibratory hammers for 15 seconds at reduced energy followed by a 1-minute waiting period. The procedure shall be repeated two additional times before full energy may be achieved.
(B) If a non-diesel impact hammer is used, BP is required to provide an initial set of strikes from the impact hammer at reduced energy, followed by a 1-minute waiting period, then two subsequent sets.
(C) If a diesel impact hammer is used, BP is required to turn on the sound attenuation device for 15 seconds prior to initiating pile driving.
(vi) New drilling into oil-bearing strata shall not take place during either open-water or spring-time broken ice conditions.
(vii) All non-essential boats, barge, and air traffic will be scheduled to avoid periods when bowhead whales are migrating through the area where they may be affected by noise from these activities.
(3) Helicopter flights to support Northstar activities must be limited to a corridor from Seal Island to the mainland, and, except when limited by weather or personnel safety, must maintain a minimum altitude of 1,000 ft (305 m), except during takeoff and landing.
(4) Additional mitigation measures as contained in a Letter of Authorization issued under Sec. Sec. 216.106 and 217.148 of this chapter.
(b) [Reserved]