When conducting the specified activities identified in § 217.160(c), Hilcorp must implement the mitigation measures contained in this section and any LOA issued under §§ 216.106 of this chapter and 217.166 unless implementing the mitigation measure would create a risk to human safety or cause pile instability or refusal. These mitigation measures include, but are not limited to:

(a) A copy of any issued LOA should be in the possession of Hilcorp, its designees, and work crew personnel operating under the authority of the issued LOA.

(b) Hilcorp must coordinate with local Tribes as described in its Stakeholder Engagement Plan, notify the communities of any changes in the operation, and take action to avoid or mitigate impacts to subsistence harvests.

(c) Tug boat and pile driving supervisors and crews, the monitoring team, and relevant Hilcorp staff must be trained prior to the start of all activities so that responsibilities, communication procedures, mitigation measures, monitoring protocols, and operational procedures are clearly understood. New personnel joining during the project must be trained prior to commencing work.

(d) Hilcorp must implement clearance and shutdown zones with radial distances as identified in any LOA issued under §§ 216.106 of this chapter and 217.166.

(e) Pre-start clearance monitoring.

(1) Prior to initiating any activity or resuming those activities after a 30-minute lapse (e.g., pauses between intermittent pile driving), Hilcorp must conduct monitoring of the clearance zones 30 minutes prior to commencing activities identified in § 217.160(c) (i.e., pre-start clearance monitoring).

(2) Except for tugs towing a jack-up rig, activities may commence or resume if, following 30 minutes of observation of the clearance zone, it is determined by a protected species observer (PSO) that the clearance zones are clear of marine mammals.

(3) Should a marine mammal be within the clearance zone during the clearance monitoring period, the activity (except for tugs under tow if tidal restrictions necessitate) must not commence or resume until any animal has left the clearance zone and is on a path away from the clearance zone or at least 30 minutes has elapsed for all baleen whale species and Cook Inlet Beluga Whales (CIBWs) without subsequent detection, or 15 minutes has elapsed without subsequent detection for all other species.

(f) Pile driving at the Tyonek Platform may only occur from November 15 through April 15.

(g) Hilcorp must cease all pile driving activities, including soft starts, if a marine mammal is observed entering or within the shutdown zone. Should safety or pile instability or refusal concerns prevent a shutdown, pile driving may continue only until the current segment of the pile is driven; no additional sections of pile or additional piles may be driven until a PSO has determined that the clearance zones are clear of marine mammals.

(1) If pile driving is halted or delayed due to the presence of a marine mammal, the activity may not commence or resume until either the animal has voluntarily left and is visually confirmed to be beyond the shutdown zone or at least 30 minutes has elapsed for all baleen whale species and CIBWs without subsequent detection or 15 minutes has elapsed without subsequent detection for all other species.

(2) If during pile driving, a PSO can no longer effectively monitor the entirety of the corresponding shutdown zone due to environmental conditions (e.g., fog, rain, wind), pile driving may continue only until the current segment of the pile is driven. No additional sections of pile or additional piles may be driven until conditions improve such that the shutdown zone can be effectively monitored. If the shutdown zone cannot be monitored for more than 15 minutes, the entire zone must be cleared again for 30 minutes prior to reinitiating pile driving.

(h) Hilcorp must use soft-start techniques when impact pile driving. Should safety or pile instability/refusal concerns arise during a soft start wherein this process cannot be met, Hilcorp must use the minimum amount of energy practicable. Prior to soft-start beginning, the operator must receive confirmation from the PSO that the clearance zone is clear of any marine mammals.

(i) For transportation of a jack-up rig to or from the Tyonek platform, in addition to PSOs stationed on the rig during towing, an additional PSO must be stationed on the Tyonek Platform to monitor for marine mammals. The PSO should be on watch for at least 1 hour before tugs are expected to arrive (scheduled to approach the estimated 120-dB isopleth).

(j) Unless deviation is necessary to maintain safe maneuvering speed and justified because the vessel is in an area where oceanographic, hydrographic, and/or meteorological conditions severely restrict the maneuverability of the vessel; an emergency situation presents a threat to the health, safety, life of a person; or a vessel is actively engaged in emergency rescue or response duties, including vessel-in-distress or environmental crisis response, Hilcorp must:

(1) Maneuver tugs engaged in towing, holding, or positioning a jack-up rig, and anchor handling and pipe pulling activities such that they maintain a consistent speed (approximately 4 knots [kt; 7 kilometers (km)/hr]) and avoid multiple changes of speed and direction to make the course of the vessels as predictable as possible to marine mammals in the surrounding environment, characteristics that are expected to be associated with a lower likelihood of disturbance;

(2) Not actively approach a marine mammal purposefully and must adhere to NOAA Alaska Region Marine Mammal Viewing Guidelines;

(3) Reduce vessel speed to < 9 km/hr (5 kt) when within 274 meters (m; 300 yards) of any whale, reduce speed to 18.5 km/hr (10 kt) or less when weather conditions reduce visibility to 1.6 km (1 mile [mi]) or less, avoid multiple changes in direction and speed when within 274 m (300 yards) of any whale, and place the engine in neutral if a whale is approaching within 91 m (100 yards) of a vessel;

(4) Maintain a distance of at least 2.4 km from the Mean Lower Low Water line of the Susitna River Delta (Beluga River to the Little Susitna River) between April 15 and November 15; and

(5) Maintain a watch for marine mammals while underway and check water immediately adjacent to the vessel prior to engaging propellers; should a marine mammal be observed near propellers and it is determined that interaction is possible, delay engaging propellers.

(k) Hilcorp must maintain clean, taught lines in the water such that no lines are in the water unless both ends are under tension and affixed to vessels or gear.