Section 217.134 - Mitigation requirements(a) When conducting the activities identified in § 217.130(a) , the mitigation measures contained in this subpart and any LOA issued under § 216.106 of this chapter and § 217.136 must be implemented. These mitigation measures include:(1) A copy of any issued LOA must be in the possession of the Navy, its designees, and work crew personnel operating under the authority of the issued LOA at all times that activities subject to this LOA are being conducted.(2) Should environmental conditions deteriorate such that marine mammals within the entire shutdown zone would not be visible (e.g., fog, heavy rain, night), the Navy shall delay pile driving and drilling until observers are confident marine mammals within the shutdown zone could be detected.(3) The Navy must ensure that construction supervisors and crews, the monitoring team, and relevant Navy staff are trained prior to the start of construction activity subject to this rule, so that responsibilities, communication procedures, monitoring protocols, and operational procedures are clearly understood. New personnel joining during the project will be trained prior to commencing work.(4) The Navy, construction supervisors and crews, protected species observers (PSOs), and relevant Navy staff must avoid direct physical interaction with marine mammals during construction activity. If a marine mammal comes within 10 m of such activity, operations will cease and vessels will reduce speed to the minimum level required to maintain steerage and safe working conditions, as necessary, to avoid direct physical interaction.(5) The Navy must monitor the project area to the maximum extent possible based on the required number of PSOs, required monitoring locations, and environmental conditions as described in this rule and the NMFS-approved Marine Mammal Monitoring Plan.(6) Monitoring must take place from 30 minutes prior to initiation of pile driving or drilling activity (i.e., pre-start clearance monitoring) through 30 minutes post-completion of pile driving or drilling activity.(7) For all pile driving and drilling activities, the Navy must implement shutdown zones with radial distances as identified in a LOA issued under § 216.106 of this chapter and § 217.136 . If a marine mammal comes within or approaches the shutdown zone, such operations must cease.(8) In the event of a delay or shutdown of activity resulting from marine mammals in the shutdown zone, animals must be allowed to remain in the shutdown zone (i.e., must leave of their own volition) and their behavior must be monitored and documented. If a marine mammal is observed within the shutdown zone, pile driving or drilling activities may not commence or resume until at least one of the following conditions has been met: (i) The animal has been observed exiting the shutdown zone;(ii) The animal is thought to have exited the shutdown zone based on a determination of its course, speed, and movement relative to the pile driving location; or(iii) The shutdown zone has been clear from any additional sightings for fifteen minutes.(9) If pile driving or drilling construction activities cease for more than 30 minutes, the pre-activity monitoring of the shutdown zone must commence.(10) The Navy must conduct monitoring to include the entire region of influence, which includes the area within the Level A and Level B harassment zones with radial distances as identified in a LOA issued under § 216.106 of this chapter and § 217.136 .(11) The Navy must use soft start techniques when impact pile driving. Soft start requires contractors to provide an initial set of strikes from the hammer at reduced energy, followed by a 30-second waiting period, then two subsequent reduced-energy strike sets. A soft start will be implemented at the start of each day's impact pile driving and at any time following cessation of impact pile driving for a period of 30 minutes or longer.(12) The Navy must install a bubble curtain across the entrance openings during DTH cluster drill and hydraulic rock hammering activities. The bubble curtain must adhere to the following restrictions:(i) The bubble curtain must distribute air bubbles across 100 percent of the entrance openings for the full depth of the water column;(ii) The lowest bubble ring must be in contact with the substrate for the full extent of the curtain, and the weights attached to the bottom of the curtain must ensure 100 percent substrate contact. No parts of the curtain or other objects shall prevent full substrate contact; and(iii) Air flow to the bubblers must be balanced across the entrance openings to the super flood basin.(iv) The Navy shall require that construction contractors train personnel in the proper balancing of air flow to the bubblers and corrections to the attenuation device to meet the performance standards. This shall occur prior to the initiation of in-water construction activities.(13) The bubble curtain may be discontinued for certain activities should the results of hydroacoustic recordings inside the bubble curtain show that the source levels from those activities do not result in the Level A harassment thresholds being achieved across the entire region of influence, upon review of the data by NMFS.(14) Pile driving and drilling activity must be halted upon observation of either a species entering or within the harassment zone for which incidental take is not authorized, or a species for which incidental take has been authorized but the authorized number of takes has been met. 88 FR 19539 , 4/1/2023through 3/31/2028