# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Oil and Gas Activities in Cook Inlet, Alaska > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2019-15867 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** July 31, 2019 - **Citation:** 84 FR 37442 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 217 [Docket No. 190214112-9535-02] RIN 0648-BI62 Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Oil and Gas Activities in Cook Inlet, Alaska AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Final rule; issuance of Letters of Authorization (LOA). SUMMARY: NMFS, upon request from Hilcorp Alaska LLC (Hilcorp), hereby issues regulations to govern the unintentional taking of marine mammals incidental to oil and gas activities in Cook Inlet, Alaska, over the course of five years (2019-2024). These regulations, which allow for the issuance of Letters of Authorization (LOA) for the incidental take of marine mammals during the described activities and specified timeframes, prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat, as well as requirements pertaining to the monitoring and reporting of such taking. In accordance with the Marine Mammal Protection Act (MMPA), as amended, and implementing regulations, notification is hereby additionally given that a LOA has been issued to Hilcorp to take marine mammals incidental to oil and gas activities. DATES: Effective from July 30, 2019, to July 30, 2024. FOR FURTHER INFORMATION CONTACT: Sara Young, Office of Protected Resources, NMFS, (301) 427-8401. SUPPLEMENTARY INFORMATION: Availability A copy of Hilcorp's application and any supporting documents, as well as a list of the references cited in this document, may be obtained online at: www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these documents, please call the contact listed above (see FOR FURTHER INFORMATION CONTACT ). Purpose and Need for Regulatory Action These regulations establish a framework under the authority of the MMPA (16 U.S.C. 1361 et seq. ) to allow for the authorization of take of marine mammals incidental to Hilcorp's oil and gas activities in Cook Inlet, Alaska. We received an application from Hilcorp requesting five-year regulations and authorization to take multiple species of marine mammals. Take will occur by Level A and Level B harassment incidental to a variety of sources including: Two-dimensional (2D) and three-dimensional (3D) seismic surveys, geohazard surveys, vibratory sheet pile driving, and drilling of exploratory wells. Please see “Background” below for definitions of harassment. Legal Authority for the Action Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs the Secretary of Commerce to allow, upon request, the incidental, but not intentional taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region for up to five years if, after notice and public comment, the agency makes certain findings and issues regulations that set forth permissible methods of taking pursuant to that activity and other means of effecting the least practicable adverse impact on the affected species or stocks and their habitat (see the discussion below in the “Mitigation” section), as well as monitoring and reporting requirements. Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for issuing this rule containing five-year regulations, and for any subsequent LOAs. As directed by this legal authority, this rule contains mitigation, monitoring, and reporting requirements. Summary of Major Provisions Within the Rule Following is a summary of the major provisions of this rule regarding Hilcorp's activities. These measures include: • Required monitoring of the ensonified areas to detect the presence of marine mammals before beginning activities; • Required aerial surveys to search for Cook Inlet beluga whales before beginning seismic surveys; • Shutdown of activities under certain circumstances to minimize injury of marine mammals; • Ramp up at the beginning of seismic surveying to allow marine mammals the opportunity to leave the area prior to beginning the survey at full power, and vessel strike avoidance; • Ramp up of impact hammering of the drive pipe for the conductor pipe driven from the drill rig; and • Ceasing noise producing activities within 10 miles (16 km) of the mean higher high water (MHHW) line of the Susitna Delta (Beluga River to the Little Susitna River) between April 15 and October 15, as well as ceasing seismic activity within the Level B harassment isopleth distance of the mouth of the Kasilof River between January 1 and May 31. Background The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq. ) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed incidental take authorization may be provided to the public for review. Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of such takings must be set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival. The MMPA states that the term “take” means to harass, hunt, capture, kill or attempt to harass, hunt, capture, or kill any marine mammal. Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment). National Environmental Policy Act To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq. ) and NOAA Administrative Order (NAO) 216-6A, NMFS reviewed our proposed action ( i.e., the issuance of an incidental harassment authorization) with respect to potential impacts on the human environment. NMFS prepared an Environmental Assessment (EA) and analyzed the potential impacts to marine mammals that will result from Hilcorp's activities. A Finding of No Significant Impact (FONSI) was signed on July 17, 2019. A copy of the EA and FONSI is available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-oil-and-gas. Summary of Request On April 17, 2018, NMFS received an application from Hilcorp (or “the applicant”) requesting authorization to incidentally take marine mammals, by Level A and Level B harassment, incidental to noise exposure resulting from oil and gas activities in Cook Inlet, Alaska, from May 2019 to April 2024. These regulations will be valid for a period of five years. On October 8, 2018, NMFS deemed the application adequate and complete. The use of sound sources such as those described in the application ( e.g., seismic airguns) may result in the take of marine mammals through disruption of behavioral patterns or may cause auditory injury of marine mammals. Therefore, incidental take authorization under the MMPA is warranted. Description of Activity Overview The scope of Hilcorp's Incidental Take Regulations (ITR) Petition includes four stages of activity, including exploration, development, production, and decommissioning activities within the applicant's area of operations in and adjacent to Cook Inlet within the Petition's geographic area (Figures 3 and 8 in the application). Table 1 summarizes the planned activities within the geographic scope of this Petition, and the following text describes these activities in more detail. This section is organized into two primary areas within Cook Inlet: Lower Cook Inlet (south of the Forelands to Homer) and middle Cook Inlet (north of the Forelands to Susitna/Point Possession). Table 1—Summary of Planned Activities Included in Incidental Take Regulations (ITR) Petition [Updates from Table 1 in the proposed rule are reflected in bold] Project name Cook Inlet region Year(s) planned Seasonal timing Anticipated duration Antiicpated noise sources Anchor Point 2D seismic survey Lower Cook Inlet, Anchor Point to Kasilof 2021 or 2022 April-October 30 days ( 10 days seismic ) Marine: 1 source vessel with airgun array , 1 node vessel. Onshore/Intertidal: Shot holes, tracked vehicles, helicopters. OCS 3D seismic survey Lower Cook Inlet OCS 2019 or 2020 April-October 45-60 days 1 source vessel with airgun array , 2 support vessels, 1 mitigation vessel. OCS geohazard survey Lower Cook Inlet OCS 2020-2021 April-October 30 days 1 vessel with echosounders and/or sub-bottom profilers. OCS exploratory wells Lower Cook Inlet OCS 2020-2022 February-November 40-60 days per well, 2-4 wells per year 1 jack-up rig, drive pipe installation, vertical seismic profiling, 2-3 tugs for towing rig, support vessels, helicopters. Iniskin Peninsula exploration and development (causeway construction) Lower Cook Inlet, west side 2020 -2022 April-October 180 days each year Construction of causeway, vibratory sheet pile driving, dredging, vessels. Platform & pipeline maintenance Middle Cook Inlet 2019-2024 April-October 180 days ( each year ) Vessels, water jets, hydraulic grinders, pingers, helicopters, and/or sub-bottom profilers No change. North Cook Inlet Unit subsea well geohazard survey Middle Cook Inlet 2020 April-October 14 days 1 vessel with echosounders and/or sub-bottom profilers No change. North Cook Inlet Unit well abandonment activity Middle Cook Inlet 2020 April-October 90 days 1 jack-up rig, tugs towing rig, support vessel, helicopters. Trading Bay area geohazard survey Middle Cook Inlet 2020 April-October 30 days 1 vessel with echosounders and/or sub-bottom profilers. Trading Bay area exploratory wells Middle Cook Inlet 2020 April-October 120-150 days 1 jack-up rig, drive pipe installation, vertical seismic profiling, tugs towing rig, support vessel, helicopters. Granite Point production drilling and geohazard survey * Middle Cook Inlet 2019 June-October 120-150 days 1 jack-up rig, tugs towing rig, support vessel, helicopters, 1 vessel with echosounders. Drift River terminal decommissioning Lower Cook Inlet, west side 2020 -2023 April-October 120 days Vessels. * While these activities were added after the proposed rule, they do not involve technologies that NMFS believes are likely to result in take and therefore do not change the number of takes authorized. Bold text indicates changes from Table 1 in the Proposed Rule. Dates and Duration The scope of the Petition includes exploration, development, production, and decommissioning activities within the applicant's area of operations in and adjacent to Cook Inlet within the Petition's geographic area (Figures 3 and 8 in the application) for the period of five years beginning May 1, 2019, extending through April 30, 2024. Specific Geographic Region The geographic area of activity covers a total of approximately 2.7 million acres (10,926 km 2 ) in Cook Inlet. It includes land and adjacent waters in Cook Inlet including both State of Alaska and Federal OCS waters (Figure 3 and 8 in the application). The area extends from the north at the Susitna Delta on the west side (61°10′48 N, 151°0′55 W) and Point Possession on the east side (61°2′11 N, 150°23′30 W) to the south at Ursus Cove on the west side (59°26′20 N, 153°45′5 W) and Nanwalek on the east side (59°24′5 N, 151°56′30 W). The area is depicted in Figures 3 and 8 of the application. Detailed Description of Specific Activity It is difficult to characterize each year accurately because many of the activities are progressive ( i.e., they depend on results and/or completion of the previous activity). This results in some uncertainty in the timing, duration, and complete scope of work for each year. The applicant will submit an application for a LOA with the specific details of the planned work for that year and with estimated take numbers using the same assumptions as in the ITR Petition. Activities in Lower Cook Inlet Based on potential future lease sales in both State and Federal waters, operators collect two-dimensional (2D) seismic data to determine the location of possible oil and gas prospects. Generally, 2D survey lines are spaced farther apart than three-dimensional (3D) survey lines, and 2D surveys are conducted in a regional pattern that provides less detailed geological information. 2D surveys are used to cover wider areas to map geologic structures on a regional scale. Airgun array sizes used during 2D surveys are similar to those used during 3D surveys. Activities in Middle Cook Inlet 2D Seismic Survey During the timeframe of this Petition, the region of interest for the 2D survey is the marine, intertidal, and onshore area on the eastern side of Cook Inlet from Anchor Point to the mouth of the Kasilof River. The area of interest is approximately 8 km (5 miles) offshore of the coastline. The anticipated timing of the planned 2D survey is in the open water season (April through October) in either 2020 or 2021. The actual survey duration is approximately 30 days in either year, but only 10 of the 30 days would be in-water seismic work. The 2D seismic data are acquired using airguns in the marine zone, airguns in the intertidal zone when the tide is high, drilled shot holes in the intertidal zone when the tide is low, and drilled shot holes in the land zone. The data are recorded using an autonomous nodal system ( i.e., no cables) that are deployed in the marine, intertidal, and land zones. The planned source lines (airgun and shot holes) are approximately 16 km (10 mi) in length running perpendicular to the coastline (see Figure 1 in the application). The source lines are spaced every 8 km (5 mi) in between Anchor Point and Kasilof, with approximately 9-10 lines over the area of interest. In the marine and high tide intertidal zones, data will be acquired using a shallow water airgun towed behind one source vessel. Although the precise volume of the airgun array is unknown at this time, Hilcorp will use an airgun array similar to what has been used for surveys in Cook Inlet by Apache (2011-2013) and SAExploration (2015): Either a 2,400 cubic inch (in 3 ) or 1,760 in 3 array. A 2,400 in 3 airgun was assumed for analysis in this rule to be conservative in take estimation. In addition, the source vessel will be equipped with a 440 in 3 shallow water source which it can deploy at high tide in the intertidal area in less than 1.8 meters (m) (6 feet (ft)) of water. Source lines are oriented along the node line. A single vessel is capable of acquiring a source line in approximately 1-2 hours (hrs). In general, only one source line will be collected in one day to allow for all the node deployments and retrievals, and intertidal and land zone shot holes drilling. There are up to 10 source lines, so if all operations run smoothly, there will only be 2 hrs per day over 10 days of airgun activity. Hilcorp anticipates the entire operation to take approximately 30 days to complete to account for weather and equipment contingencies. The recording system that will be employed is an autonomous system “nodal” ( i.e., no cables), which is expected to be made up of at least two types of nodes; one for the land and one for the intertidal and marine environment. For the intertidal and marine zone, this will be a submersible multi-component system made up of three velocity sensors and a hydrophone. These systems have the ability to record continuous data. Inline receiver intervals for the node systems are approximately 50 m (165 ft). For 2D seismic surveys, the nodes are deployed along the same line as the seismic source. The deployment length is restricted by battery duration and data storage capacity. The marine nodes will be placed using one node vessel. The vessels required for the 2D seismic survey include just a source vessel and a node vessel that is conducting only passive recording. In the marine environment, once the nodes are placed on the seafloor, the exact position of each node is required. In very shallow water, the node positions are either surveyed by a land surveyor when the tide is low, or the position is accepted based on the position at which the navigator has laid the unit. In deeper water, a hull or pole mounted pinger to send a signal to the transponder attached to each node will be used. The transponders are coded and the crew knows which transponder goes with which node prior to the layout. The transponders response (once pinged) is added together with several other responses to create a suite of range and bearing between the pinger boat and the node. Those data are then calculated to precisely position the node. In good conditions, the nodes can be interrogated as they are laid out. It is also common for the nodes to be pinged after they have been laid out. Onshore and intertidal locating of source and receivers will be accomplished with Differential Global Positioning System/roving units (DGPS/RTK) equipped with telemetry radios which will be linked to a base station established on the source vessel. Survey crews will have both helicopter and light tracked vehicle support. Offshore source and receivers will be positioned with an integrated navigation system (INS) utilizing DGPS/RTK links to the land base stations. The integrated navigation system will be capable of many features that are critical to efficient safe operations. The system will include a hazard display system that can be loaded with known obstructions, or exclusion zones. Apache conducted a sound source verification (SSV) for the 440 in 3 and 2,400 in 3 arrays in 2012 (Austin and Warner 2012; 81 FR 47239). The location of the SSV was in Beshta Bay on the western side of Cook Inlet (between Granite Point and North Forelands). Water depths ranged from 30-70 m (98-229 ft). For the 440 in 3 array, the measured levels for the broadside direction were 217 decibel (dB) re: 1microPa (μPa) peak, 190 dB sound exposure level (SEL), and 201 dB root mean square (rms) at a distance of 50 m. The estimated distance to the 160 dB rms (90th percentile) threshold, assuming the empirically measured transmission loss of 20.4 log R (Austin and Warner, 2012), was 2,500 m. Sound levels near the source were highest between 30 and 300 hertz (Hz) in the endfire direction and between 20 Hz and 300 Hz in the broadside direction. For the 2,400 in 3 array, the measured levels for the endfire direction were 217 dB peak, 185 dB SEL, and 197 dB rms at a distance of 100 m. The estimated distance to the 160 dB rms (90th percentile) thresholds, assuming the empirically measured transmission loss of 16.9 log R, was 7,770 m. Sound levels near the source were highest between 30 and 150 Hz in the endfire direction and between 50 and 200 Hz in the broadside direction. During the process of issuing regulations for Apache Alaska, JASCO provided an updated distance of 7,330 m for a 24-hour survey (81 FR 47239). This updated estimate is considered the best available science for seismic activity of similar array size in Cook Inlet and was used to estimate take in this rulemaking. It is important to note that neither survey by Hilcorp is expected to use an airgun array of 2,400 in 3 ; both surveys will use an airgun array with a lower in 3 than this. However, 7,330 m is used in calculations as it is the closest known and measured value for seismic airgun isopleths for arrays of a similar size in middle and lower Cook Inlet. Further, a sound source verification (SSV) will be performed to characterize the actual array and environmental parameters for the area to be surveyed. These measured levels were used to evaluate potential Level A harassment (217 dB peak and 185 dB SEL at 100 m assuming 15 log transmission loss) and Level B harassment (7,330 m distance to 160 dB threshold) isopleths from these sound sources (see Estimated Take section). 3D Seismic Survey During the timeframe of this Petition, Hilcorp plans to collect 3D seismic data for approximately 45-60 days starting May 1, 2019 over 8 of the 14 OCS lease blocks in lower Cook Inlet. The 3D seismic survey is comprised of an area of approximately 790 km 2 (305 mi 2 ) through 8 lease blocks (6357, 6405, 6406, 6407, 6455, 6456, 6457, 6458). Hilcorp submitted an application for an Incidental Harassment Authorization (IHA) in late 2017 for a planned survey in 2018 but withdrew the application, and now plans for the survey to take place in 2019 and cover several years of surveying and development. Hilcorp plans to collect 3D seismic data for approximately 45-60 days in either the fall of 2019 (September-October) or spring of 2020 (April-May). Hilcorp plans to collect the seismic survey data in one season (either fall 2019 or spring 2020). If the seismic vessel is not able to start in September and end by October 31 to comply with BOEM lease stipulations, the survey will be postponed until spring 2020. The length of the survey will depend on weather, equipment, and marine mammal delays (contingencies of 20 percent weather, 10 percent equipment, 10 percent marine mammal were assumed in this analysis, or a 40 percent increase in expected duration to account for the aforementioned delays). Polarcus is the intended seismic contractor, and the general seismic survey design is provided below. The 3D seismic data will be acquired using a specially designed marine seismic vessel towing between 8 and 12 ~2,400-m (1.5 mi) recording cables with a dual air gun array. The survey will involve one source vessel, one support vessel, one chase vessel, and one mitigation vessel. The anticipated seismic source to be deployed from the source vessel is a 14-airgun array with a total volume of 1,945 in 3 . Crew changes are expected to occur every four to six weeks using a helicopter or support vessel from shore bases in lower Cook Inlet. The seismic survey will be active 24 hrs per day. The array will be towed at a speed of approximately 7.41 km/hr (4 knots), with seismic data collected continuously. Data acquisition will occur for approximately 5 hrs, followed by a 1.5-hr period to turn and reposition the vessel for another pass. The turn radius on the seismic vessel is approximately 3,200 m (2 mi). The data acquisition will be shot parallel to the Cook Inlet shorelines in a north/south direction. This operational direction will keep recording equipment/streamers in line with Cook Inlet currents and tides and keep the equipment away from shallow waters on the east and west sides. The program may be modified if the survey cannot be conducted as a result of noise conditions onsite ( i.e., ambient noise). The airguns will typically be turned off during the turns. The vessel will turn into the tides to ensure the recording cables/streamers remain in line behind the vessel. Hilcorp plans to use an array that provides for the lowest possible sound source to collect the target data. The array is a Bolt 1900 LLXT dual gun array. The airguns will be configured as two linear arrays or “strings;” each string will have 7 airguns shooting in a “flip-flop” configuration for a total of 14 airguns. The airguns will range in volume from 45 to 290 in 3 for a total of 1,945 in 3 . The first and last are spaced approximately 14 m (45.9 ft) apart and the strings are separated by approximately 10 m (32.8 ft). The two airgun strings will be distributed across an approximate area of 30 x 14 m (98.4 x 45.9 ft) behind the source vessel and will be towed 300-400 m (984-1,312 ft) behind the vessel at a depth of 5 m (16.4 ft). The firing pressure of the array is 2,000 pounds per square inch (psi). The airgun will fire every 4.5 to 6 seconds, depending on the exact speed of the vessel. When fired, a brief (25 milliseconds [ms] to 140 ms) pulse of sound is emitted by all airguns nearly simultaneously. Hilcorp intends to use 8 Sercel-type solid streamers or functionally similar for recording the seismic data (Figure 5 in the application). Each streamer will be approximately 2,400 m (150 mi) in length and will be towed approximately 8-15 m (26.2-49.2 ft) or deeper below the surface of the water. The streamers will be placed approximately 50 m (165 ft) apart to provide a total streamer spread of 400 m (1,148 ft). Hilcorp recognizes solid streamers as best in class for marine data acquisition because of unmatched reliability, signal to noise ratio, low frequency content, and noise immunity. The survey will involve one source vessel, one support vessel, one or two chase vessels, and one mitigation vessel. The source vessel tows the airgun array and the streamers. The support vessel provides general support for the source vessel, including supplies, crew changes, etc. The chase vessel monitors the in-water equipment and maintains a security perimeter around the streamers. The mitigation vessel provides a viewing platform to augment the marine mammal monitoring program. The planned volume of the airgun array is 1,945 in 3 . Hilcorp and their partners will be conducting detailed modeling of the array output, but a detailed SSV has not been conducted for this array in Cook Inlet. Therefore, for the purposes of estimating acoustic harassment, results from previous seismic surveys in Cook Inlet by Apache and SAExploration, particularly the 2,400 in 3 array, were used. Apache conducted an SSV for the 440 in 3 and 2,400 in 3 arrays in 2012 (Austin and Warner 2012; 81 FR 47239). The location of the SSV was in Beshta Bay on the western side of Cook Inlet (between Granite Point and North Forelands). Water depths ranged from 30-70 m (98-229 ft). For the 2,400 in 3 array, the measured levels for the endfire direction were 217 dB peak, 185 dB SEL, and 197 dB rms at a distance of 100 m. The estimated distance to the 160 dB rms (90th percentile) thresholds, assuming the empirically measured transmission loss of 16.9 log R, was 7,770 m. Sound levels near the source were highest between 30 and 150 Hz in the endfire direction and between 50 and 200 Hz in the broadside direction. These measured levels were used to evaluate potential Level A (217 dB peak and 185 dB SEL at 100 m assuming 15 log transmission loss) and Level B (7,330 m distance to 160 dB threshold) acoustic harassment of marine mammals in this Petition. Geohazard and Geotechnical Surveys Upon completion of the 3D seismic survey over the lower Cook Inlet OCS leases, Hilcorp plans to conduct a geohazard survey on site-specific regions within the area of interest prior to conducting exploratory drilling. The precise location is not known, as it depends on the results of the 3D seismic survey, but the location will be within the lease blocks. The anticipated timing of the activity is in either the fall of 2019 or the spring of 2020. The actual survey duration will take approximately 30 days. The suite of equipment used during a typical geohazards survey consists of single beam and multi-beam echosounders, which provide water depths and seafloor morphology; a side scan sonar that provides acoustic images of the seafloor; a sub-bottom profiler which provides 20 to 200 m (66 to 656 ft) sub-seafloor penetration with a 6- to 20-centimeter (cm, 2.4-7.9-inch (in)) resolution. Magnetometers, to detect ferrous items, may also be used. Geotechnical surveys are conducted to collect bottom samples to obtain physical and chemical data on surface and near sub-surface sediments. Sediment samples typically are collected using a gravity/piston corer or grab sampler. The surveys are conducted from a single support vessel. The echosounders and sub-bottom profilers are generally hull-mounted or towed behind a single vessel. The ship travels at 3-4.5 knots (5.6-8.3 km/hr). Surveys are site specific and can cover less than one lease block in a day, but the survey extent is determined by the number of potential drill sites in an area. BOEM guidelines at NTL-A01 require data to be gathered on a 150 by 300 m (492 by 984 ft) grid within 600 m (1,969 ft) of the surface location of the drill site, a 300 by 600 m (984 by 1,969 ft) grid along the wellbore path out to 1,200 m (3,937 ft) beyond the surface projection of the conductor casing, and extending an additional 1,200 m beyond that limit with a 1,200 by 1,200 m grid out to 2,400 m (7,874 ft) from the well site. The multibeam echosounder, single beam echosounder, and side scan sonar operate at frequencies of greater than 200 kHz. Based on the frequency ranges of these pieces of equipment and the hearing ranges of the marine mammals that have the potential to occur in the action area, the noise produced by the echosounders and side scan sonar are not likely to result in take of marine mammals and are not considered further in this document. The geophysical surveys include use of a low resolution and high resolution sub-bottom profiler. The high-resolution sub-bottom profiler operates at source level of 210 dB re 1 μPa RMS at 1 m. The system emits energy in the frequency bands of 2 to 24 kHz. The beam width is 15 to 24 degrees. Typical pulse rate is between 3 and 10 Hz. The secondary low-resolution sub-bottom profiler will be utilized as necessary to increase sub-bottom profile penetration. The system emits energy in the frequency bands of 1 to 4 kHz. Exploratory Drilling Operators will drill exploratory wells based on mapping of subsurface structures using 2D and 3D seismic data and historical well information. Hilcorp plans to conduct the exploratory drilling program April to October between 2020 and 2022. The exact start date is currently unknown and is dependent on the results of the seismic survey, geohazard survey, and scheduling availability of the drill rig. It is expected that each well will take approximately 40-60 days to drill and test. Beginning in spring 2020, Hilcorp Alaska plans to possibly drill two and as many as four exploratory wells, pending results of the 3D seismic survey in the lower Cook Inlet OCS leases. After testing, the wells may be plugged and abandoned. Hilcorp Alaska plans to conduct its exploratory drilling using a rig similar to the Spartan 151 drill rig. The Spartan 151 is a 150 H class independent leg, cantilevered jack-up drill rig with a drilling depth capability of 7,620 m (25,000 ft) that can operate in maximum water depths up to 46 m (150 ft). Depending on the rig selection and location, the drilling rig will be towed on site using up to three ocean-going tugs licensed to operate in Cook Inlet. Rig moves will be conducted in a manner to minimize any potential risk regarding safety as well as cultural or environmental impact. While under tow to the well sites, rig operations will be monitored by Hilcorp and the drilling contractor management. Very High Frequency (VHF) radio, satellite, and cellular phone communication systems will be used while the rig is under tow. Helicopter transport will also be available. Similarly to transiting vessels, although some marine mammals could receive sound levels in exceedance of the general acoustic threshold of 120 dB from the tugs towing the drill rig during this project, take is unlikely to occur, primarily because of the predictable movement of vessels and tugs. Additionally, marine mammal population density in the project area is low (see Estimated Take section below), and those that are present are likely habituated to the existing baseline of commercial ship traffic. Further, there are no activity-, location-, or species-specific circumstances or other contextual factors that increase concern and the likelihood of take from towing of the drill rig. The drilling program for the well will be described in detail in an Exploration Plan to BOEM. The Exploration Plan will present information on the drilling mud program; casing design, formation evaluation program; cementing programs; and other engineering information. After rig up/rig acceptance by Hilcorp Alaska, the wells will be spudded and drilled to bottom-hole depths of approximately 2,100 to 4,900 m (7,000 to 16,000 ft) depending on the well. It is expected that each well will take about 40-60 days to drill and up to 10-21 days of well testing. If two wells are drilled, it will take approximately 80-120 days to complete the full program; if four wells are drilled, it will take approximately 160-240 days to complete the full program. Primary sources of rig-based acoustic energy were identified as coming from the D399/D398 diesel engines, the PZ-10 mud pump, ventilation fans (and associated exhaust), and electrical generators. The source level of one of the strongest acoustic sources, the diesel engines, was estimated to be 137 dB re 1 μPa rms at 1 m in the 141-178 Hz bandwidth. Based on this measured level, the 120 dB rms acoustic received level isopleth is 50 m (154 ft) away from where the energy enters the water (jack-up leg or drill riser). Drilling and well construction sounds are similar to vessel sounds in that they are relatively low-level and low-frequency. Since the rig is stationary in a location with low marine mammal density, the impact of drilling and well construction sounds produced from the jack up rig is expected to be lower than a typical large vessel. There is open water in all directions from the drilling location. Any marine mammal approaching the rig would be fully aware of its presence long before approaching or entering the zone of influence for behavioral harassment, and we are unaware of any specifically important habitat features ( e.g., concentrations of prey or refuge from predators) within the rig's zone of influence that encourages marine mammal use and exposure to higher levels of noise closer to the source. Given the absence of any activity-, location-, or species-specific circumstances or other contextual factors that increase concern, we do not expect routine drilling noise to result in the take of marine mammals. When planned and permitted operations are completed, the well will be suspended according to Bureau of Safety and Environmental Enforcement (BSEE) regulations. The well casings will be landed in a mudline hanger after each hole section is drilled. When the well is abandoned, the production casing is sealed with mechanical plugging devices and cement to prevent the movement of any reservoir fluids between various strata. Each casing string will be cutoff below the surface and sealed with a cement plug. A final shallow cement plug will be set to approximately 3.05 m (10 ft) below the mudline. At this point, the surface casing, conductor, and drive pipe will be cutoff and the three cutoff casings and the mudline hanger are pulled to the deck of the jack-up rig for final disposal. The plugging and abandonment procedures are part of the Well Plan which is reviewed by BSEE prior to being issued an approved Permit to Drill. A drive pipe is a relatively short, large-diameter pipe driven into the sediment prior to the drilling of oil wells. The drive pipe serves to support the initial sedimentary part of the well, preventing the looser surface layer from collapsing and obstructing the wellbore. Drive pipes are installed using pile driving techniques. Hilcorp plans to drive approximately 60 m of 76.2-cm pipe at each well site prior to drilling using a Delmar D62-22 impact hammer (or similar). This hammer has an impact weight of 6,200 kg (13,640 lbs). The drive pipe driving event is expected to last one to three days at each well site, although actual pounding of the pipe will only occur intermittently during this period. Illingworth & Rodkin (2014) measured the hammer noise for hammering the drive pipe operating from the rig Endeavour for Buccaneer in 2013 and reported the source level at 190 dB at 55 m, with underwater levels exceeding 160 dB rms threshold at 1.63 km (1 mi). The measured sound levels for the pipe driving were used to evaluate potential Level A (source level of 221dB @ 1m and assuming 15 logR transmission loss) and Level B (1,630 m distance to the 160 dB threshold) acoustic harassment of marine mammals. Conductors are slightly smaller diameter pipes than the drive pipes used to transport or “conduct” drill cuttings to the surface. For these wells, a 50.8-cm (20-in) conductor pipe may be drilled, not hammered, inside the drive pipe, dependent on the integrity of surface formations. There are no noise concerns associated with the conductor pipe drilling. Once the well is drilled, accurate follow-up seismic data may be collected by placing a receiver at known depths in the borehole and shooting a seismic airgun at the surface near the borehole, called vertical seismic profiling (VSP). These data provide high-resolution images of the geological layers penetrated by the borehole and can be used to accurately correlate original surface seismic data. The actual size of the airgun array is not determined until the final well depth is known, but typical airgun array volumes are between 600 and 880 in 3 . VSP typically takes less than two full days at each well site. Illingworth & Rodkin (2014) measured a 720 in 3 array for Buccaneer in 2013 and report the source level at 227 dB at 1 m, with underwater levels exceeding 160 dB rms threshold at 2.47 km (1.54 mi). The measured sound levels for the VSP were used to evaluate potential Level A harassment (227 dB rms at 1 m assuming 15 logR transmission loss) and Level B harassment (2,470 m distance to the 160 dB threshold) isopleths. Iniskin Peninsula Exploration Hilcorp Alaska initiated baseline exploratory data collection in 2013 for a proposed land-based oil and gas exploration and development project on the Iniskin Peninsula of Alaska, near Chinitna Bay. The project is approximately 97 km (60 mi) west of Homer on the west side of Cook Inlet in the Fitz Creek drainage. New project infrastructure includes material sites, a 6.9 km (4.3 mi) long access road, prefabricated bridges to cross four streams, an air strip, barge landing/staging areas, fuel storage facilities, water wells and extraction sites, an intertidal causeway, a camp/staging area, and a drill pad. Construction is anticipated to start in 2020. An intertidal rock causeway will be constructed adjacent to the Fitz Creek staging area to improve the accessibility of the barge landing during construction and drilling operations. The causeway will extend seaward from the high tide line approximately 366 m (1,200 ft) to a landing area 46 m (150 ft) wide. A dock face will be constructed around the rock causeway so that barges will be able to dock along the causeway. Rock placement for the causeway is not known to generate sound at levels expected to disturb marine mammals. The causeway is also not planned at a known pinniped haulout or other biologically significant location for local marine mammals. Therefore, rock laying for the causeway is not considered further in this document. The causeway will need to be 75 percent built before the construction of the dock face will start. The dock face will be constructed with 18-m (60-ft) tall Z-sheet piles, all installed using a vibratory hammer. It will take approximately 14-25 days, depending on the length of the work shift, assuming approximately 25 percent of the day actual pile driving. The timing of pile driving will be in late summer or early winter, after the causeway has been partially constructed. Illingworth & Rodkin (2007) compiled measured near-source (10 m [32.8 ft]) SPL data from vibratory pile driving for different pile sizes ranging in diameter from 30.5 to 243.8 cm (12 to 96 in). For this Petition, the source level of the 61.0-cm (24-in) AZ steel sheet pile from Illingworth & Rodkin (2007) was used for the sheet pile. The measured sound levels of 160 dB rms at 10 m, assuming 15 logR transmission loss for the vibratory sheet pile driving, was used to evaluate potential Level A and B harassment isopleths. Airborne sound from this construction is only expected to impact pinnipeds that are hauled out in the area where sound levels exceed in-air harassment thresholds. While harbor seals are known to use nearby bays, no major land haulouts exist in the project area and no harassment from airborne sound is expected to result from project activities. Therefore, above-water construction will not be discussed further in this document. Activities in Middle Cook Inlet Offshore Production Platforms Of the 17 production platforms in central Cook Inlet, 15 are owned by Hilcorp. Hilcorp performs routine construction on their platforms, depending on needs of the operations. Construction activities may take place up to 24 hrs a day. In-water activities include support vessels bringing supplies five days a week up to two trips per day between offshore systems at Kenai (OSK) and the platform. Depending on the needs, there may also be barges towed by tugs with equipment and helicopters for crew and supply changes. Routine supply-related transits from vessels and helicopters are not substantially different from routine vessel and air traffic already occurring in Cook Inlet, and take is not expected to occur from these activities. Offshore Production Drilling Hilcorp routinely conducts development drilling activities at offshore platforms on a regular basis to meet the asset's production needs. Development drilling activities occurs from existing platforms within the Cook Inlet through either open well slots or existing wellbores in existing platform legs. Drilling activities from platforms within Cook Inlet are accomplished by using conventional drilling equipment from a variety of rig configurations. Some other platforms in Cook inlet have permanent drilling rigs installed that operate under power provided by the platform power generation systems, while others do not have drill rigs, and the use of a mobile drill rig is required. Mobile offshore drill rigs may be powered by the platform power generation (if compatible with the platform power system) or self-generate power with the use of diesel fired generators. For the reasons outlined above for the Lower Inlet, noise from routine drilling is not considered further in this document. Helicopter logistics for development drilling programs operations will include transportation for personnel and supplies. The helicopter support will be managed through existing offshore services based at the OSK Heliport to support rig crew changes and cargo handling. Helicopter flights to and from the platform while drilling is occurring is anticipated to increase (on average) by two flights per day from normal platform operations. Major supplies will be staged on-shore at the OSK Dock in Nikiski. Required supplies and equipment will be moved from the staging area to the platform in which drilling occurring by existing supply vessels that are currently in use supporting offshore operations within Cook Inlet. Vessel trips to and from the platform while drilling is occurring is anticipated to increase (on average) by two trips per day from normal platform operations. During mobile drill rig mobilization and demobilization, one support vessel is used continuously for approximately 30 days to facilitate moving rig equipment and materials. Oil and Gas Pipeline Maintenance Each year, Hilcorp Alaska must verify the structural integrity of their platforms and pipelines located within Cook Inlet. Routine maintenance activities include: Subsea pipeline inspections, stabilizations, and repairs; platform leg inspections and repairs; and anode sled installations and/or replacement. In general, pipeline stabilization and pipeline repair are anticipated to occur in succession for a total of 6-10 weeks. However, if a pipeline stabilization location also requires repair, the divers will repair the pipeline at the same time they are stabilizing it. Pipeline repair activities are only to be conducted on an as-needed basis whereas pipeline stabilization activities will occur annually. During underwater inspections, if the divers identify an area of the pipeline that requires stabilization, they will place Sea-Crete bags at that time rather than waiting until the major pipeline stabilization effort that occurs later in the season. Natural gas and oil pipelines located on the seafloor of the Cook Inlet are inspected on an annual basis using ultrasonic testing (UT), cathodic protection surveys, multi-beam sonar surveys, and sub-bottom profilers. Deficiencies identified are corrected using pipeline stabilization methods or USDOT-approved pipeline repair techniques. The applicant employs dive teams to conduct physical inspections and evaluate cathodic protection status and thickness of subsea pipelines on an annual basis. If required for accurate measurements, divers may use a water jet to provide visual access to the pipeline. For stabilization, inspection dive teams may place Sea-Crete bags beneath the pipeline to replace any materials removed by the water jet. Results of the inspections are recorded and significant deficiencies are noted for repair. Multi-beam sonar and sub-bottom profilers may also be used to obtain images of the seabed along and immediately adjacent to all subsea pipelines. Elements of pipeline inspections that could produce underwater noise include: The dive support vessel, water jet, multi-beam sonar/sub-bottom profiler and accompanying vessel. A water jet is a zero-thrust water compressor that is used for underwater removal of marine growth or rock debris underneath the pipeline. The system operates through a mobile pump which draws water from the location of the work. Water jets likely to be used in Cook Inlet include, but are not limited to, the CaviDyne CaviBlaster® and the Gardner Denver Liqua-Blaster. Noise generated during the use of the water jets is very short in duration (30 minutes or less at any given time) and intermittent. Hilcorp Alaska conducted underwater measurements during 13 minutes of CaviBlaster® use in Cook Inlet in April 2017 (Austin 2017). Received sound levels were measured up to 143 dB re 1 μPa rms at 170 m and up to 127 dB re 1 μPa rms at 1,100 m. Sounds from the Caviblaster® were clearly detectable out to the maximum measurement range of 1.1 km. Using the measured transmission loss of 19.5 log R (Austin 2017), the source level for the Caviblaster® was estimated as 176 dB re 1 μPa at 1 m. The sounds were broadband in nature, concentrated above 500 Hz with a dominant tone near 2 kHz. Specifications for the GR 29 Underwater Hydraulic Grinder state that the SPL at the operator's position is 97 dB in air (Stanley 2014). There are no underwater measurements available for the grinder, so using a rough estimate of converting sound level in dB in air to water by adding 61.5 dB results in an underwater level of approximately 159 dB at 1 meter. The measured sound levels for the water jet were used to evaluate potential Level A and B acoustic harassment isopleths, but the grinder was not included. If necessary, Hilcorp may use an underwater pipe cutter to replace existing pipeline segments in Cook Inlet. The following tools are likely to be used for pipeline cutting activities: • A diamond wire saw used for remote cutting underwater structures such as pipes and I-Beams. These saws use hydraulic power delivered by a dedicated power source. The saw usually uses a method that pushes the spinning wire through the pipe. • A hydraulically-powered Guillotine saw which uses an orbital cutting movement similar to traditional power saws. Generally, sound radiated from the diamond wire cutter is not easily discernible from the background noise during the cutting operation. The Navy measured underwater sound levels when the diamond saw was cutting caissons for replacing piles at an old fuel pier at Naval Base Point Loma (Naval Base Point Loma Naval Facilities Engineering Command Southwest 2017). They reported an average SPL for a single cutter at 136.1-141.4 dB rms at 10 m. Specifications for the Guillotine saw state that the SPL at the operator's position is 86 dB in air (Wachs 2014). There are no underwater measurements available for the grinder, so using a rough estimate of converting sound level in dB in air to water by adding 61.5 dB results in an underwater level of approximately 148 dB at 1 meter. Because the measured levels for use of underwater saws do not exceed the NMFS criteria, the noise from underwater saws was not considered further in this document. Scour spans beneath pipelines greater than 23 m (75 ft) have the potential to cause pipeline failures. To be conservative, scour spans of 15 m (50 ft) or greater identified using multi-beam sonar surveys are investigated using dive teams. Divers perform tactile inspections to confirm spans greater than 15 m (50 ft). The pipeline is stabilized along these spans with Sea-Crete concrete bags. While in the area, the divers will also inspect the external coating of the pipeline and take cathodic protection readings if corrosion wrap is found to be absent. Significant pipeline deficiencies identified during pipeline inspections are repaired as soon as practicable using methods including, but not limited to, USDOT-approved clamps and/or fiber glass wraps, bolt/flange replacements, and manifold replacements. In some cases, a water jet may be required to remove sand and gravel from under or around the pipeline to allow access for assessment and repair. The pipeline surface may also require cleaning using a hydraulic grinder to ensure adequate repair. If pipeline replacement is required, an underwater pipe cutter such as a diamond wire saw or hydraulically-powered Guillotine saw may be used. Water jets are the only equipment in pipeline stabilization activities that could produce underwater noise that have the potential to result in take of marine mammals. Platform Leg Inspection and Repair Hilcorp's platforms in Cook Inlet are inspected on a routine basis. Divers and certified rope access technicians visually inspect subsea platform legs. These teams also identify and correct significant structural deficiencies. Platform leg integrity and pipeline-to-platform connections beneath the water surface are evaluated by divers on a routine basis. Platform legs, braces, and pipeline-to-platform connections are evaluated for cathodic protection status, structure thickness, excessive marine growth, damage, and scour. If required, divers may use a water jet to clean or provide access to the structure. If necessary, remedial grinding using a hydraulic underwater grinder may be required to determine the extent of damage and/or to prevent further crack propagation. All inspection results are recorded and significant deficiencies are noted for repair. Elements of subsea platform leg inspection and repair that could produce underwater noise include: Dive support vessel, hydraulic grinder, water jet. Platform leg integrity along the tidal zone is inspected on a routine basis. Difficult-to-reach areas may be accessed using either commercially-piloted unmanned aerial systems (UAS). Commercially-piloted UASs may be deployed from the top-side of the platform to obtain images of the legs. Generally, the UAS is in the air for 15-20 minutes at a time due to battery capacity, which allows for two legs and part of the underside of the platform to be inspected. The total time to inspect a platform is approximately 1.5 hrs of flight time. The UAS is operated at a distance of up to 30.5 m (100 ft) from the platform at an altitude of 9-15 m (30-50 ft) above sea level. To reduce potential harassment of marine mammals, the area around the platform will be inspected prior to launch of the UAS to ensure there are no flights directly above marine mammals. As no flights will be conducted directly over marine mammals, the effects of drone use for routine maintenance are not considered further in this application. Anode Sled Installation and Replacement Galvanic and impressed current anode sleds are used to provide cathodic protection for the pipelines and platforms in Cook Inlet. Galvanic anode sleds do not require a power source and may be installed along the length of the pipelines on the seafloor. Impressed current anode sleds are located on the seafloor at each of the corners of each platform and are powered by rectifiers located on the platform. Anodes are placed at the seafloor using dive vessels and hand tools. If necessary, a water jet may be used to provide access for proper installation. Anodes and/or cables may be stabilized using Sea-Crete bags. Pingers Several types of moorings are deployed in support of Hilcorp operations; all require an acoustic pinger for location or release. The pinger is deployed over the side of a vessel, and a short signal is emitted to the mooring device. The mooring device responds with a short signal to indicate that the device is working, to indicate range and bearing data, or to illicit a release of the unit from the anchor. These are used for very short periods of time when needed. The types of moorings requiring the use of pingers anticipated to be used in the Petition period include acoustic moorings during the 3D seismic survey (assumed 2-4 moorings), node placement for the 2D survey (used with each node deployment), and potential current profilers deployed each season (assumed 2-4 moorings). The total amount of time per mooring device is less than 10 minutes during deployment and retrieval. To avoid disturbance, the pinger will not be deployed if marine mammals have been observed within 135 m (443 ft) of the vessel. The short duration of the pinger deployment as well as Hilcorp's mitigation suggests take of marine mammals from pinger use is unlikely to occur, and pingers are not considered further in this analysis. North Cook Inlet Unit Subsea Well Plugging and Abandonment The discovery well in the North Cook Inlet Unit was drilled over 50 years ago and is planned to be abandoned, so in 2020 Hilcorp Alaska plans to conduct a geohazard survey to locate the well and conduct plugging and abandonment (P&A) activities for a previously drilled subsea exploration well. The geohazard survey location is approximately 402-804 m ( 1/4 - 1/2 mi) south of the Tyonek platform and will take place over approximately seven days with a grid spacing of approximately 250 m (820 ft). The suite of equipment used during a typical geohazards survey consists of single beam and multi-beam echosounders, which provide water depths and seafloor morphology; a side scan sonar that provides acoustic images of the seafloor; a sub-bottom profiler which provides 20 to 200 m (66 to 656 ft) sub-seafloor penetration with a 6- to 20-cm (2.4-7.9-in) resolution. The echosounders and sub-bottom profilers are generally hull-mounted or towed behind a single vessel. The vessel travels at 3-4.5 knots (5.6-8.3 km/hr). After the well has been located, Hilcorp plans to conduct plugging and abandonment activities over a 60-90 day time period from May through July in 2020. The jack-up rig will be similar to what is described above (the Spartan 151 drill rig, or similar). The rig will be towed onsite using up to three ocean-going tugs. Once the jack-up rig is on location, divers working off a boat will assist in preparing the subsea wellhead and mudline hanger for the riser to tie the well to the jack-up. At this point, the well will be entered and well casings will be plugged with mechanical devices and cement and then cutoff and pulled. A shallow cement plug will be set in the surface casing to 3.05 m (10 ft) below the mudline hanger. The remaining well casings will be cutoff and the mudline hanger will be recovered to the deck of the jack-up rig for disposal. The well abandonment will be performed in accordance to Alaska Oil and Gas Conservation Commission (AOGCC) regulations. Trading Bay Exploratory Drilling Hilcorp plans to conduct exploratory drilling activities in the Trading Bay area. The specific sites of interest have not yet been identified, but the general area is shown in Figure 3 in the application. Hilcorp will conduct geohazard surveys over the areas of interest to locate potential hazards prior to drilling with the same suite of equipment as described above for exploratory drilling in the lower Inlet. The survey is expected to take place over 30-60 days in 2019 from a single vessel. The exploratory drilling and well completion activities will take place in site-specific areas based on the geohazard survey. Hilcorp plans to drill 1-2 exploratory wells in this area in the open water season of 2020 with the same equipment and methods as described above for lower Inlet exploratory drilling. The noise of routine drilling is not considered further as explained in the description of activities in the Lower Inlet. However, drive pipe installation and vertical seismic profiling will be considered further in the Estimated Take section. Required mitigation, monitoring, and reporting measures are described in detail later in this document (please see Mitigation and Monitoring and Reporting ). Public Comments and Responses A notice of NMFS's proposal to issue regulations to Hilcorp was published in the Federal Register on April 1, 2019 (84 FR 12330). That notice described, in detail, Hilcorp's activity, the marine mammal species that may be affected by the activity, and the anticipated effects on marine mammals. During the 30-day public comment period, NMFS received comments from the Marine Mammal Commission (the Commission), several NGOs, the Cook Inlet Regional Citizens Advisory Council, and private citizens. These comments and our responses are described below. Comment 1: The Commission recommended that NMFS ensure all applicants include a site-specific stakeholder engagement plan or plan of cooperation that includes the required information on the species or stocks potentially affected by the proposed activities, a list of communities contacted, a summary of input received, a schedule for ongoing community engagement, and measures that would be implemented to mitigate any potential conflicts with subsistence hunting, as part of their LOA requests. Response: Hilcorp has shared the stakeholder meeting tracking tool with NMFS listing dates, attendees, and discussions specifically on marine mammal subsistence hunting. Hilcorp will continue to update NMFS and USFWS with this tracking tool. Each annual LOA will include a detailed Marine Mammal Mitigation and Monitoring Plan (4MP) for the activities to be conducted in that year. The list of communities and individuals contacted, date and form of contact, and any issues raised, will be posted on the NMFS Incidental Take Program website. Comment 2: Several commenters recommended that NMFS defer issuance of a final rule to Hilcorpor any other applicant proposing to conduct sound-producing activities in Cook Inlet until NMFS has a reasonable basis for determining that authorizing any incidental harassment takes would not contribute to or exacerbate the decline of Cook Inlet beluga whales. Response: In accordance with our implementing regulations at 50 CFR 216.104(c), we use the best available scientific evidence to determine whether the taking by the specified activity within the specified geographic region will have a negligible impact on the species or stock and will not have an unmitigable adverse impact on the availability of such species or stock for subsistence uses. Based on the scientific evidence available, NMFS determined that the impacts of the oil and gas program, which are primarily acoustic in nature, would meet the standard of no more than a negligible impact and no unmitigable adverse impact on availability of marine mammals for subsistence uses. Moreover, Hilcorp proposed and NMFS has required in the rule a rigorous mitigation plan to reduce impacts to Cook Inlet beluga whales and other marine mammals to the lowest level practicable. Hilcorp is required to shutdown airguns if any beluga whale is observed within the Level B isopleth (described further in our Ensonified Area section), and activities are further restricted by imposing a shutdown of activities within a 10 mi (16 km) radius of the Susitna Delta from April 15 through October 15, which is an important area for beluga feeding and calving in the spring and summer months. These shutdown measures are more restrictive than the standard shutdown measures typically applied and combined with the Susitna Delta exclusion (minimizing adverse effects to foraging), they are expected to reduce both the scope and severity of potential harassment takes, ensuring that there are no energetic impacts from the harassment that would adversely affect reproductive rates or survivorship. Additionally, since the proposed rule was published, another mitigation area has been added in an area and time where belugas have been observed congregating, to further minimize impacts. Specifically, no 2D seismic airgun activity will be allowed between January 1 and May 31 within the level B harassment radius (which may be updated based on the SSV results) of the Kasilof River. We are assuming that timing of belugas in the Kasilof is likely similar to the timing of belugas in the nearby Kenai River (sighings peak in spring and fall, with little to no presence in the summer). Belugas may also be present in the Kenai River throughout the year; however, there are peaks of beluga presence in spring (Castellote et al. 2016; NMFS unpublished data) and sightings also in the fall (August through October; NMFS unpublished data). There appears to be a steep decline in beluga presence in the Kenai River area during the summer (June through August); however, historically belugas were seen throughout the summer in the area. Cook Inlet belugas were also historically observed in the nearby Kasilof River during aerial surveys conducted by ADFG in the late 1970s and early 1980s and NMFS starting in 1993 (Shelden et al. 2015b). NMFS' records of opportunistic sightings contain thirteen records of beluga sightings in the Kasilof River between 1978 and 2015, with half of those sightings occurring since 2008 (Shelden et al. 2015b; NMFS unpublished data). In 2018, surveys of local residents in the Kenai/Kasilof area were conducted by NMFS. There were two reports of sightings of belugas in the Kasilof River in April; one of these reports was of a group of around 30 belugas (NMFS unpublished data). Our analysis indicates that issuance of these regulations will not contribute to or worsen the observed decline of the Cook Inlet beluga whale population. Additionally, the ESA Biological Opinion determined that the issuance of this rule is not likely to jeopardize the continued existence of the Cook Inlet beluga whales or the western distinct population segment of Steller sea lions or to destroy or adversely modify Cook Inlet beluga whale critical habitat. The Biological Opinion also outlined Terms and Conditions and Reasonable and Prudent Measures to reduce impacts, which have been incorporated into the rule, including an additional area closure of the Kasilof River mouth discussed in the Mitigation section below. Therefore, based on the analysis of potential effects, the parameters of the activity, and the rigorous mitigation and monitoring program, NMFS determined that the activity would have a negligible impact on the Cook Inlet beluga whale stock. Moreover, the oil and gas activity would take only small numbers of marine mammals relative to their population sizes. Further, either these takes represent one annual disturbance event for each of these individuals, or perhaps a few individuals could be disturbed a few times, in which case the number of impacted individual whales is even lower. As described in the proposed rule Federal Register notice, NMFS used a method that incorporates density of marine mammals overlaid with the anticipated ensonified area to calculate an estimated number of takes for belugas, which was estimated to be less than 10% of the stock abundance, which NMFS considers small. Comment 3: Several commenters recommended that NMFS defer issuance of Hilcorp's final rule until all activities for which incidental take authorizations or regulations have been or are expected to be issued are considered with respect to their anticipated, cumulative take of Cook Inlet beluga whales, as part of a Programmatic Environmental Iimpact Statement under NEPA. Response: NMFS originally declared its intent to prepare an Environmental Impact Statement (EIS) for oil and gas activities in Cook Inlet, Alaska (79 FR 61616; October 14, 2014). However, in a 2017 Federal Register notice (82 FR 41939; September 5, 2017), NMFS indicated that due to a reduced number of Incidental Take Authorization (ITA) requests in the region, combined with funding constraints at that time, we were postponing any potential preparation of an EIS for oil and gas activities in Cook Inlet. As stated in the 2017 Federal Register notice, should the number of ITA requests, or anticipated requests, noticeably increase, NMFS will re-evaluate whether preparation of an EIS is necessary. Currently, the number of ITA requests for activities that may affect marine mammals in Cook Inlet is at such a level that preparation of an EIS is not yet necessary. Nonetheless, under NEPA, NMFS is required to consider cumulative effects of other potential activities in the same geographic area, and these are discussed in greater detail in the Final Environmental Assessment (EA). Comment 4: The Commission also recommended that NMFS establish annual limits on the total number and type of takes that are authorized for all sound-producing activities in Cook Inlet before issuing the final rule. Response: As mentioned above, NMFS is required to make its required determinations at the specified activities level ( i.e., the entire project described in the application) under the MMPA. Setting limits on the number and types of takes across individual activity pieces is not necessary, as there are no takes associated with any specific portion of the project that have differential or more severe impacts such that they require individual management or limits. Further, there are few incidental takes of Cook Inlet beluga whales currently authorized in Cook Inlet, and the projects for which takes are authorized are separated spatially and temporally. NMFS explores the effects of potential overlap in projects and the effects of sound sources other than sound sources resulting in incidental take on Cook Inlet beluga whales in the Cumulative Effects section of the Final EA. Comment 5: The Commission recommended that NMFS address and fix inconsistencies with respect to information provided regarding the referenced sound sources. Response: NMFS clarified which sound sources were referenced to 1 m. NMFS also clarified that it does not expect that the sounds produced by hydraulic grinders or pipe cutters are likely to result in take. Therefore, NMFS did not analyze those source any further. Comment 6: The Commission recommended that NMFS require Hilcorp to ensure that the total number of days for each activity is accurate and consistent, and recommended that NMFS revise the number of days used to estimate the number of marine mammal takes for each of the proposed activities based on the number of days each type of activity is scheduled to occur regardless of the duration of those activities on a given day. Response: The number of days of activity have been updated in the calculations for take estimates, and an updated Table 1 is included in the project description above. Comment 7: The Commission recommended that NMFS require Hilcorp to revise the geohazard survey durations for each of the well sites (the four lower Cook Inlet OCS sites, the North Cook Inlet Unit site, and the two Trading Bay area sites) and re-estimate the number of marine mammal takes. Response: Geohazard duration was calculated based on a worst-case scenario, as the precise scope of work will depend on results of other surveys. Therefore, the original estimate is still appropriate: 2,400 m of monitoring distance in both directions yields 4,800 m total length of transect. This 4,800 m of transect distance, divided by 150 m transect width yields 32 transects. 4,800 m transect length multiplied by 32 transects yields 153.6 km transect length to be surveyed. If the distance is covered at a speed of 7.41 km/hour this results in 0.65 hours (38 minutes) to survey each transect. If surveying can occur for 12 hours per day, this results in 7.77 days to survey one well grid. This duration (7/77 days) multiplied by the number of wells results in durations of: 31 days for OCS wells, eight days for Northern Cook Inlet wells, and 15.5 days for Trading Bay wells. Comment 8: The Commission recommended that NMFS determine which of the proposed activities will actually occur this year and which will be delayed until 2020, and revise the numbers of marine mammal takes accordingly. Response: As noted above, these activities are progressive and dependent on results from the previous year, so predicting activities by year is challenging. Hilcorp has provided a “worst case” 5-year scenario of activities. Based on the predicted schedule, we have used June 1 to May 31 as the annual scenario described in the Estimated Take Section below. Therefore, we attempt to use “Year 1 or Season 1” terminology, as these activities are not confined to single calendar years (January to December). One of the primary challenges with the forecasting annual activities is how to break up and analyze components associated with the OCS exploratory drilling ( i.e., VSP, conductor pipe driving, geohazard). Hilcorp has clarified that the plan is to drill all 4 wells between June 1 2020-2021 (Year 2), as long as everything goes well. So, we have included a shallow hazard survey in April-May 2020 (Year 1) over 2 of the 4 wells, and then a suite of drilling activities (VSP, conductor pipe driving) over all 4 wells in June 2020-2021 (Year 2), with the other 2 wells surveyed for shallow hazards (shallow hazard survey must be conducted within a few months of the planned drilling, so we would do shallow hazard in between the wells). To be conservative, we have included drilling activities (VSP, conductor pipe, and shallow hazard) for 1 of 4 wells in Years 3 and 4, in the event OCS activities take longer than the planned 1 year. Tables 11 through 18 have been updated accordingly. Comment 9: The Commission noted several inconsistencies regarding source levels presented in either the application or the proposed rule which did not result in the correct outputs for Level A harassment isopleths. The Commission did not agree with several pulse durations used in the proposed rule, including the chosen pulse duration for the profiler (boomer), which the Commission suggests is too long at 90 msec for a repetition rate of 30 msec, as well as VSP and impact pile driving, for which the Commission suggests the pulse durations were too short at 20 msec. The Commission recommended that NMFS recalculate all of the Level A harassment zones and revise the numbers of marine mammal takes and mitigation measures accordingly. Response: The exposure estimates have been updated using the NMFS 2018 guidance and updated user spreadsheet inputs. Per the Commission's comments, the boomer pulse duration was adjusted to 0.1 sec (100 ms). The VSP pulse duration was kept at 0.02 sec (20 ms). When speaking to the Hilcorp engineers, they indicated that the seismic pulse for VSP is generally the same as for 3D seismic survey, or generally 20 ms . The impact pipe driving was adjusted to 0.1 sec (100 ms) per the Commission's comments. It is important to note that the specific equipment for everything other than the 3D seismic survey is not known at this time because contractors have not been selected; these are estimates only, although the equipment will be required to be within the parameters outlined in the proposed rule. If peak measurements were not available, the RMS was used to calculate peak. Many of the SSV reports prior to 2016 did not include peak or SEL. They only included RMS for the 190/180/160/120 dB thresholds, such as the VSP and water jet. The inputs used are as follows: 3D/2D seismic survey: 217 dB peak/185 dB SEL @100 m; 2.05 m/s vessel speed, pulse duration 0.02 s, repetition rate every 6 s; • Profiler (boomer): 212 dB peak @1 m; 2.05 m/s vessel speed, pulse duration 0.1 s, repetition rate every 6 s; • VSP: 227 dB rms @1 m; 4 hrs per day; pulse duration 0.02 s; repetition rate 6 s; • Water jet: 176 dB rms @1 m; 3 hrs per day; • Pipe driving: 195 dB rms @55 m; 1 pile per day; 0.100 s; 25 strikes per pile • Vib pile driving: 160 dB rms @10 m; 5 piles per day; 90 min per pile Table 4 has been updated accordingly. Comment 10: The Commission recommended that, until the behavior thresholds are updated, NMFS require Hilcorp to use the 120- dB re 1 μPa threshold rather than the 160-dB re 1 μPa threshold for intermittent, non-impulsive sources, such as chirps. Response: Please see our Notice of Proposed Rulemaking (83 FR 37638; August 1, 2018) for the discussion related to acoustic terminology and thresholds. The Commission repeats a recommendation made in prior letters concerning proposed authorization of take incidental to the use of scientific sonars (such as echosounders). As we have described in responses to those prior comments ( e.g., 83 FR 36370), our evaluation of the available information leads us to disagree with this recommendation. After review of the Commission's recommendation in this case, our assessment is unchanged. While the Commission presents certain valid points in attempting to justify their recommendation ( e.g., certain sensitive species are known to respond to sound exposures at lower levels), these points do not ultimately support the recommendation. First, we provide here some necessary background on implementation of acoustic thresholds. NMFS has historically used generalized acoustic thresholds based on received levels to predict the occurrence of behavioral disturbance rising to the level of Level B harassment, given the practical need to use a relatively simple threshold based on information that is available for most activities. Thresholds were selected largely in consideration of measured avoidance responses of mysticete whales to airgun signals and to industrial noise sources, such as drilling. The selected thresholds of 160 dB rms SPL and 120 dB rms SPL, respectively, have been extended for use for estimation of behavioral disturbance rising to the level of Level B harassment associated with noise exposure from sources associated with other common activities. The Commission misinterpreted how NMFS characterizes scientific sonars, so we provide clarification here. Sound sources can be divided into broad categories based on various criteria or for various purposes. As discussed by Richardson et al. (1995), source characteristics include strength of signal amplitude, distribution of sound frequency and, importantly in context of these thresholds, variability over time. With regard to temporal properties, sounds are generally considered to be either continuous or transient ( i.e., intermittent). Continuous sounds, which are produced by the industrial noise sources for which the 120-dB behavioral threshold was selected, are simply those for which sound pressure level remain above ambient sound during the observation period (ANSI, 2005). Intermittent sounds are defined as sounds with interrupted levels of low or no sound (NIOSH, 1998). Simply put, a continuous noise source produces a signal that continues over time, while an intermittent source produces signals of relatively short duration having an obvious start and end with predictable patterns of bursts of sound and silent periods ( i.e., duty cycle) (Richardson and Malme, 1993). It is this fundamental temporal distinction that is most important for categorizing sound types in terms of their potential to cause a behavioral response. For example, Gomez et al. (2016) found a significant relationship between source type and marine mammal behavioral response when sources were split into continuous ( e.g., shipping, icebreaking, drilling) versus intermittent ( e.g., sonar, seismic, explosives) types. In addition, there have been various studies noting differences in responses to intermittent and continuous sound sources for other species ( e.g., Neo et al., 2014; Radford et al., 2016; Nichols et al., 2015). Sound sources may also be categorized based on their potential to cause physical damage to auditory structures and/or result in threshold shifts. In contrast to the temporal distinction discussed above, the most important factor for understanding the differing potential for these outcomes across source types is simply whether the sound is impulsive or not. Impulsive sounds, such as those produced by airguns, are defined as sounds which are typically transient, brief (< 1 sec), broadband, and which consist of a high peak pressure with rapid rise time and rapid decay (ANSI, 1986; NIOSH, 1998). These sounds are generally considered to have greater potential to cause auditory injury and/or result in threshold shifts. Non-impulsive sounds can be broadband or narrowband ( i.e., tonal), brief or prolonged, and continuous or intermittent, and typically do not have the high peak pressure with rapid rise/decay time that impulsive sounds have (ANSI, 1995; NIOSH, 1998). Because the selection of the 160-dB behavioral threshold was focused largely on airgun signals, this threshold has historically been referred to as the “impulse noise” threshold (including by NMFS). However, this longstanding confusion in terminology— i.e., the erroneous impulsive/continuous dichotomy—presents a narrow view of the sound sources to which the thresholds apply and inappropriately implies a limitation in scope of applicability for the 160-dB behavioral threshold in particular. An impulsive sound is by definition intermittent; however, not all intermittent sounds are impulsive. Many sound sources for which it is generally appropriate to consider the authorization of incidental take are in fact either impulsive (and intermittent) ( e.g., impact pile driving) or continuous (and non-impulsive) ( e.g., vibratory pile driving). However, scientific sonars present a less common case where the sound produced is considered intermittent but non-impulsive. Herein lies the crux of the Commission's argument, i.e., that because chirps used by Hilcorp are not impulsive sound sources, they must be assessed using the 120-dB behavioral threshold appropriate for continuous noise sources. However, given the existing paradigm—dichotomous thresholds appropriate for generic use in evaluating the potential for behavioral disturbance rising to the level of Level B harassment resulting from exposure to continuous or intermittent sound sources—the Commission does not adequately explain why potential harassment from an intermittent sound source should be evaluated using a threshold developed for use with continuous sound sources. As we have stated in prior responses to this recommendation, consideration of the preceding factors leads to a conclusion that the 160-dB threshold is more appropriate for use than the 120-dB threshold. As noted above, the Commission first claims generically that we are using an incorrect threshold, because scientific sonars do not produce impulse noise. However, in bridging the gap from this generic assertion to their specific recommendation that the 120-dB continuous noise threshold should be used, the Commission makes several leaps of logic that we address here. The Commission's justification is in large part seemingly based on the Commission's citation to examples in the literature of the most sensitive species responding at lower received levels to sources dissimilar to those considered here. There are three critical errors in this approach. First, the citation of examples of animals “responding to sound” does not equate to Level B harassment, as defined by the MMPA. As noted above under “Background,” the MMPA defines Level B harassment as acts with the potential to disturb a marine mammal by causing disruption of behavioral patterns. While it is possible that some animals do in fact experience Level B harassment upon exposure to intermittent sounds at received levels less than the 160-dB threshold, this is not in and of itself adequate justification for using a lower threshold. Implicit in the use of a step function for quantifying Level B harassment is the realistic assumption, due to behavioral context and other factors, that some animals exposed to received levels below the threshold will in fact experience harassment, while others exposed to levels above the threshold will not. Moreover, a brief, transient behavioral response alone should not necessarily be considered as having the potential to disturb by disrupting behavioral patterns. We note that the Commission cites Lurton and DeRuiter (2011), which suggests 130 dB as a reasonable behavioral response threshold. Given that a “behavioral response threshold” does not equate to a Level B harassment threshold, we are unsure about the potential implications. In addition, Lurton and DeRuiter casually offered this threshold as a result of a “conservative approach” using “response thresholds of the most sensitive species studied to date.” NMFS does not agree with any suggestion that this equates to an appropriate Level B harassment threshold. Watkins and Schevill (1975) noted that when sperm whales were exposed to “temporarily interrupted” sound production in response to sound from pingers, no avoidance behavior was observed, and the authors note that “there appeared to be no startle reactions, no sudden movements, or changes in the activity of the whales.” Kastelein et al. (2006a) described the response of harbor porpoise to an experimental acoustic alarm (discussed below; averaged source level of 145 dB), while also noting that a striped dolphin showed no reaction to the alarm, despite both species being able to clearly detect the signal. Second, unlike the studies discussed above, which relate to echosounders, many of the cited studies do not present a relevant comparison. These studies discuss sources that are not appropriately or easily compared to the sources considered here, and address responses of animals in experimental environments that are not appropriately compared to the likely exposure context here. For example, aside from the well-developed literature concerning “acoustic harassment” or “acoustic deterrent” devices—which are obviously designed for the express purpose of harassing marine mammals (usually specific species or groups)—Kastelein et al. (2006b) describe harbor seal responses to signals used as part of an underwater data communication network. In this case, seals in a pool were exposed to signals of relatively long duration (1-2 seconds) and high duty cycle for 15 minutes, with experimental signals of continuously varying frequency, three different sound blocks, or frequency sweeps. These seals swam away from the sound (though they did not attempt to reduce exposure by putting their heads out of the water), but this result is of questionable relevance to understanding the likely response of seals in the wild that may be exposed to a 1-ms single-frequency signal from an echosounder moving past the seal as a transient stimulus. Some studies do not provide a relevant comparison not only because of differences in the source, but because they address sources (in some cases multiple sources) that are stationary (for extended periods of time in some cases); whereas, Hilcorp's use of sub-bottom profilers will be infrequent and transient in any given location. Morton (2000) presents only brief speculation that an observed decline in abundance of Pacific white-sided dolphin coincided with introduction of 194-dB (source level) acoustic deterrent devices—an observation that is not relevant to consideration of a single mobile source that would be transient in space and time relevant to a receiver. Morton and Symonds (2002) similarly address displacement from a specific area due to a profusion of “high-powered” deterrent devices (the same 194-dB system discussed briefly in Morton (2000)) placed in restricted passages for extended time periods (6 years). Third, the Commission's sources tend to pertain to the most sensitive species, which does not support an argument that the 120-dB threshold should be applied to all species. NMFS has acknowledged that the scientific evidence indicates that certain species are, in general, more acoustically sensitive than others. In particular, harbor porpoise and beaked whales are considered to be behaviorally sensitive, and it may be appropriate to consider use of lower Level B harassment thresholds for these species. NMFS is considering this issue in its current work of developing new guidelines for assessing Level B harassment; however, until this work is completed and new guidelines are identified (if appropriate), the existing generic thresholds are retained. Moreover, as is discussed above for other reasons, the majority of examples cited by the Commission are of limited relevance in terms of comparison of sound sources. In support of their statement that numerous researchers have observed marine mammals responding to sound from sources claimed to be similar to those considered herein, the Commission cites numerous studies; however, the vast majority of these studies address responses of harbor porpoise or beaked whales to various types of acoustic alarms or deterrent devices. We acknowledge that the Commission presents legitimate points in support of defining a threshold specific to non-impulsive, intermittent sources, and that, among the large number of cited studies, there are a few that show relevant results of individual animals responding to exposure at lower received levels in ways that could be considered harassment under the MMPA. As noted in a previous comment response, NMFS is currently engaged in an ongoing effort to develop updated guidance regarding the effects of anthropogenic sound on marine mammal behavior. However, prior to conclusion of this effort, NMFS will continue using the historical Level B harassment thresholds (or derivations thereof) and will appropriately evaluate behavioral disturbance rising to the level of Level B harassment due to intermittent sound sources relative to the 160-dB threshold. Comment 11: The Commission recommended that NMFS clarify what density estimates were used to determine the numbers of takes and ensure the density estimates for marine mammals other than beluga whales are consistent with its stated method for calculating densities based on sightings from aerial surveys from 2000-2016. Response: The densities used are detailed in Table 7 for Cook Inlet beluga whales and Table 8 for all other marine mammal species. Table 8 in the proposed rule included incorrect density estimates from a previous version of exposure calculations that included hours surveyed as part of the calculation, while also correcting for distance. The densities in Table 9 of this final rule are the correct densities based on NMFS aerial survey data, using number of animals sighted divided by distance surveyed. The values in Table 9 are the densities used to calculate exposure estimates for this final rule. Comment 12: The Commission recommended that NMFS specify the relevant densities, ensonified areas associated with both Level A and B harassment for the various proposed activities, the number of days each activity would occur, and finally the numbers of takes prior to issuing the final rule. Response: Based on updated durations of activities, ensonified areas and updated exposure estimates are contained in the relevant tables throughout the final rule. Comment 13: The Commission recommended that NMFS provide the numbers of beluga whales that could be taken during the proposed activities and any assumptions made to reduce those takes. Response: The method for estimating takes of Cook Inlet beluga whale is described in the Take Estimation section below. The number of beluga whales that could be exposed during each year is listed in Tables 12-16. There are no assumptions made to reduce authorized take from estimated exposure. Comment 14: The Commission recommended that NMFS authorize the total estimated number of harbor seal takes in a given year for each year from 2019-2024 rather than presuming only 25 percent of the population would be taken during the course of the five years of activities. Response: NMFS is authorizing the total number of instances of exposure resulting from the take calculation. Note that NMFS is not equating the total number of instances of exposure to the number of individual harbor seals that may be taken, as that would lead to an overestimation of harbor seal occurrence in the survey area. The explanation for why the calculation results in overestimation of individuals is described in the Take Estimation section below. Based on consideration of the factors described further in the Estimated Take section, the number of individual harbor seals that may be taken by Level A or Level B harassment will not exceed 25 percent of the population. However, NMFS agrees with this comment from the Commission, and is authorizing an annual number of harbor seal takes rather than a certain number over the five years of activities authorized by this rule. Comment 15: The Commission recommended that, in the final rule, NMFS explicitly require Hilcorp to conduct SSVs at the beginning of the proposed activities for 3D seismic and sub-bottom profiler surveys and use those measurements to verify and adjust, if necessary, the extents of the Level A and B harassment zones. Response: SSVs for 3D seismic and sub-bottom profiler use are required in the final rule. Comment 16: The Commission recommended that NMFS (1) specify how Hilcorp should enumerate the numbers of animals taken when observers are only monitoring a portion of the Level B harassment zones, and (2) require Hilcorp to keep a tally of the numbers of marine mammals taken, alert NMFS when the number of authorized beluga whale takes has been reached, and follow any guidance provided. Response: A description of how Hilcorp should record and report takes has been added to the Monitoring section below. The specific extrapolation method to be used by Hilcorp will be submitted to NMFS Alaska Regional Office (AKR) and the Office of Protected Resources (OPR) for approval before seismic activity may begin. Hilcorp will contact NMFS AKR and OPR when the number of takes authorized for that year has been reached. Comment 17: The Commission recommends that NMFS prohibit Hilcorp from using power-down procedures as a mitigation measure for seismic surveys in Cook Inlet. The Center for Biological Diversity (CBD) commented that power-downs should be required for all species within the safety zone. Response: As noted by the Commission, a power down requirement would potentially lead to the need for termination of survey lines. The need to revisit missed survey lines to reacquire data is likely to result in an overall increase in the total sound energy input to the marine environment and an increase in the total duration over which the survey is active in a given area. NMFS has removed the use of power downs as a mitigation measure for seismic surveys in this rulemaking. Comment 18: The Commission recommends that NMFS prohibit the use of a mitigation gun to avoid implementing ramp-up procedures. Response: Mitigation guns have been removed as a mitigation measure from the final rule. While it is possible that use of a mitigation gun could provide a “warning” sound to marine mammals in the vicinity of the seismic survey source, it is likely that the use of mitigation guns would emit sound into the water at a time that the environment would otherwise be devoid of any airgun-related sound. Comment 19: The Commission recommends that NMFS specify in the final rule that observers be placed on the source vessel (for seismic and geohazard surveys) or on the drilling rig (for pile/pipe driving and VSP) to monitor the Level A and B harassment zones for the proposed sound-generating activities. Response: NMFS has specified placement of at least two on-duty PSOs on the source vessel (for seismic and geohazard surveys) or one PSO on the drill rig (for pipe driving and VSP). However, for seismic surveying, at least one on-duty PSO will be required to be stationed on a mitigation vessel. Comment 20: The Commission recommended that NMFS (1) consult with Hilcorp regarding the numerous issues raised in this letter and direct the applicant to revise the application accordingly, and (2) publish a revised proposed rule prior to issuance of a final rule. Response: NMFS has consulted with Hilcorp, which has corrected errors contained in their Petition for regulations, and in this final rule NMFS has corrected errors that were in the proposed rule. These corrections are discussed in this final rule in the Estimated Take sections. As these corrections did not substantively change NMFS' findings, a revised proposed rule was not published. Comment 21: The International Association of Geophysical Contractors (IAGC) commented that a 7,300 m shutdown zone for beluga whales was unnecessary and impractical. Response: NMFS has revised the mitigation and monitoring scheme, taking into consideration comments received during the public comment period. A 7,300 m monitoring zone is not required as it is not feasible or practicable to cover that area during seismic surveying. Instead, a 1,500 m safety zone will be implemented. This 1,500 m safety zone requires observers on the source vessel and the mitigation vessel to observe to a distance of 1,500 m during seismic activity. Hilcorp plans to conduct a SSV for 3D seismic surveys during the course of the activities authorized by this rule, and mitigation and monitoring may be adjusted based on the results of the SSV. However, in light of concerns surrounding the status of Cook Inlet beluga whales, NMFS implemented a shutdown measure that requires Hilcorp to shut down active sound sources from which take could occur if a Cook Inlet beluga whale is sighted at any distance within the relevant Level B harassment isopleths. Comment 22: The IAGC commented that the specifications for data collected by protected species observers were impractical, and that collecting data on environmental variables distracted observers from monitoring safety and exclusion zones. Response: NMFS disagrees with the commenter about the burden of collecting the required information. Applicants are required to collect information that improves our understanding of the effects of their activity. While an applicant could propose that a separate team or project could accomplish those objectives, Hilcorp proposed that their own PSOs collect the required monitoring information simultaneously with their observation duties. Information about environmental conditions informs detectability of certain species and provides detail about potential accuracy of the reported information. The IAGC also commented that recording these details could be distracting for a PSO. However, for many activities, more than one PSO is on watch simultaneously to ensure monitoring coverage is not compromised while recording other essential pieces of information. Comment 23: The IAGC commented that sound source verification studies are complicated and burdensome for operators, as the results are highly variable and should be removed from the final rule requirements. Response: NMFS disagrees with the IAGC comments that the requirement for SSVs should be removed. Cook Inlet is a unique environment with characteristics that are difficult to quantify using generic sound source studies. Additionally, very few SSVs of sub-bottom profiler sounds are available to characterize potential disturbance from the use of a sub-bottom profiler, which is an increasingly used technology. While SSVs can be unusable if conducted improperly, Hilcorp has agreed to submit their SSV plans to NMFS' acousticians to ensure that the data will be collected in a format that is useful in the future. Additionally, mitigation and monitoring measures tied to acoustic zones may be adjusted based on the results of the SSV. Comment 24: The Environmental Investigation Agency (EIA) commented that NMFS did not consider all possible sources of take by discounting take of marine mammals from echosounders and side scan sonar operating at frequencies greater than 220 kHz but producing subharmonics within hearing ranges of marine mammals. Response: The intended operating frequencies of this equipment is at 200kHz or greater, which is outside the hearing range of marine mammals in Cook Inlet. Subharmonics produced in the 90-130kHz range are not an intended byproduct of the equipment, and when the equipment is set up correctly, subharmonics should not be produced. As stated in the Deng et al. (2015) study cited by the EIA, the subharmonics produced were at sound levels so low that they were “well below potentially harmful levels”. Comment 25: The EIA commented that NMFS failed to reflect the full potential impact of noise sources, specifically the sensitivity of Cook Inlet beluga whales to anthropogenic noise. Response: NMFS has considered the sensitivity of all marine mammal species in Cook Inlet to anthropogenic activity, including the sensitivity of Cook Inlet beluga whales. Literature indicating the responses of beluga whales to anthropogenic activity, particularly seismic activity in the Beaufort Sea, is considered in this final rule. Behavioral responses to pile driving have also been considered in the rule, as NMFS discussed avoidance behavior as a possible effect of Hilcorp's activity. The short term nature of the activity in any one location, either through the use of mobile sources or localized drill activity that continues for a short amount of time before moving to a different drill rig, allows beluga whales to return to favored areas while activity continues in other locations. Additionally, the area identified as most sensitive for Cook Inlet beluga whales, the area of the Susitna Delta between the Susitna and Beluga Rivers, has been excluded from activity during periods when beluga whales are known to occur frequently. While literature suggests that beluga whales may react to anthropogenic sounds, by requesting take Hilcorp is requesting permission to incidentally harass marine mammals by emitting anthropogenic noise. Migitation and monitoring measures required by NMFS are directed at reducing potential impact of the sound, not to completely avoid behavioral harassment. Comment 26: The EIA commented that NMFS did not conduct an adequate assessment of cumulative effects in the draft Environmental Assessment (EA). Response: NMFS fulfilled its requirement under NEPA to analyze potential effects of Hilcorp's activities in conjunction with other activities that may overlap spatially or temporally in the past, present, or reasonably foreseeable future, with Hilcorp's activities or the marine mammals that may be impacted by these activities. During public comment, additional activities that should be included in the cumulative impacts assessment were raised, and these activities have been included in the final Environmental Assessment. Comment 27: The EIA expressed concern about potential renewal of the proposed incidental take authorization. Response: NMFS does not propose to renew the incidental take regulations in this final rule. The regulations would be valid for five years from the date of issuance with a maximum of five annual Letters of Authorization requested under these regulations. Comment 28: The Cook Inlet Regional Citizens Advisory Council (CIRCAC) commented that the dates proposed for 3D seismic activity in the proposed rule differ from the dates set forth in Hilcorp's Marine Mammal Mitigation and Monitoring Plan. Response: During the time period encompassing the process of requesting incidental take regulations, drafting the proposed rule, and preparing this final rule, Hilcorp's proposed timelines have been delayed slightly from what was intended in their original application. To account for these delays, tables in this final rule referring to amounts of take authorized by year have been labeled using Year 1, Year 2, etc., instead of using specific calendar dates. Comment 29: The CIRCAC expressed concern regarding the scope of the activities covered under the rulemaking and the ambiguity in dates and locations of certain components of the activities. Response: While there is potential uncertainty associated with these activities, NFMS required and Hilcorp provided information on specified activities, as well as a specified geographic area. Hilcorp provided details about all potential activities as well as where and when they could occur. Hilcorp's application included information on the maximum possible level of activity; therefore, any changes to these planned activities in the future would result in fewer activities being carried out than initially proposed. If for example, geohazard surveys do not indicate that it is feasible to conduct exploratory drilling activities at a particular site, Hilcorp would be conducting less activity than considered in this rule, and the effects would be less, not more, impactful to marine mammals than those effects analyzed in this rule. Additionally, to ensure the activities are within the scope of this rule, NMFS is requiring Hilcorp to obtain annual Letters of Authorization, thereby requiring Hilcorp to provide specific detail about each year's activities so that NMFS can determine whether these activities comport with the regulations. Comment 30: The CIRCAC commented on a lack of description of effects from developing the causeway inside Chinitna Bay on Cook Inlet beluga whales and their prey species. They also commented that proposed pile driving activities in Chinitna Bay overlap with time periods when beluga whales have been documented in the Chinitna Bay. Response: NMFS analyzed the effects of potential pile driving on marine mammal species for the building of the causeway at Chinitna Bay. Potential erosion of the area due to the creation of the causeway is not likely to result in take of marine mammals, and therefore is not part of this incidental take authorization. As referenced in the comment letter, erosion of habitat for prey species, such as crangonid shrimp and polychaetes, could certainly be a possible impact resulting from the causeway construction. However, the size of the causeway and its construction area, relative to the total available habitat for crangonid shrimp or polychaetes in middle and lower Cook Inlet, is likely very small. The construction in this area will include pile driving and rock laying for construction of a causeway extending 1,200 ft into the bay. The Iniskin causeway will result in 2.65 acres of seafloor disturbance and temporary loss of habitat. The causeway itself is likely to impact local streams and the anadromous fish (including smolt) by altering the flow of water within Chinitna Bay. The turbidity resulting from pile driving and rock laying is expected to be localized and largely indistinguishable from ambient turbidity. After the causeway is no longer needed for the project, it is proposed that rock fill be removed and relocated to a landowner- approved upland fill area, exposing the natural mud flat surface. Tidal action, wave action, and currents will naturally restore the area disturbed by the causeway. Overall, seafloor disturbance and habitat alteration could have highly localized, short-term effects on marine mammals and their prey species. Potential effects from seafloor disturbance are likely to limit the foraging quality of the disturbed area temporarily, but prey species would likely navigate to suitable nearby habitat until the habitat was returned to acceptable conditions for these species. Accordingly, marine mammals would likely forage elsewhere, and any effects on their foraging would be immeasurably small, and thus insignificant. Comment 31: Several commenters suggested that passive acoustic monitoring (PAM) should be used in addition to the proposed mitigation and monitoring. They highlight environmental differences between upper and lower Cook Inlet and suggest PAM would be successful in the lower Inlet. Response: NMFS has required PAM in several previous incidental take authorizations in Cook Inlet, including activity in mid and lower Cook Inlet. These efforts have not resulted in successful deployment of PAM or useful detections of marine mammals to inform mitigation and monitoring during the activities. NMFS looks forward to advances in technology that could make PAM a practicable mitigation measure in these areas in the future. However, at the time of this rulemaking, NMFS has elected to require additional mitigation measures outside of PAM to mediate impacts of Hilcorp's activities on marine mammals, including the use of aerial surveys for spotting beluga whales in the area and the use of additional mitigation vessels to expand visual PSO coverage. Comment 32: The CIRCAC commented that there are no monitoring requirements related to marine mammal prey species. Response: The monitoring requirement under MMPA Section 101(a)(5)(A) is intended to provide information that helps us understand the impacts of the specified activity on the affected species and stocks. While monitoring of prey species could be included as part of a monitoring plan, if the applicant submitted it, it is not required, and Hilcorp did not propose it. Hilcorp will conduct visual observations of marine mammals before, during and after sound-producing activities that have the potential to result in take. These visual observations will help us better understand the impacts of activities on behavioral responses of marine mammals to particular types of sound. These monitoring efforts can provide valuable information on species occurrence and seasonality of occurance, more detail regarding habitat use, and information about temporary habitat abandonment and timing of animal return to the affected area. Comment 33: The Center for Biological Diversity (CBD) commented that NMFS did not consider population-level effects of noise from the proposed activities. Response: NMFS has carefully reviewed the best available scientific information in assessing impacts to marine mammals and recognizes that these activities have the potential to impact marine mammals through threshold shifts, behavioral effects, stress responses, and auditory masking. However, NMFS has determined that the nature of such potentially transitory exposure—any given location will be exposed to noise from these activities only relatively briefly and infrequently—means that the likelihood of any impacts to fitness from the authorized take, including from detrimental energetic effects or reproductive impacts, is low. NMFS has also prescribed a robust suite of mitigation measures, such as a beluga-specific exclusion zone and extended distance shutdown zone, that are expected to further reduce the duration and intensity of acoustic exposure, while limiting the potential severity of any possible behavioral disruption. Further characterization of these short-term, recoverable effects with respect to long-term population success are unknown. However, disruption to behaviors such as feeding, breeding, and vocalizing, which are essential functions, are analyzed within this rule. Comment 34: The CBD commented that NMFS underestimated take of Cook Inlet beluga whales by not accounting for beluga hearing sensitivities and using densities based on seasonal aerial surveys. Response: NMFS' take estimate for Cook Inlet belugas uses the best available science concerning hearing sensitivities, occurrence, and seasonality of the species. Regarding hearing sensitivity, the NMFS Acoustic Guidance uses the best available science, vetted through peer review, to characterize the thresholds for onset of TTS and PTS in marine mammal hearing for all underwater sounds. To best assess these onset thresholds for all marine mammals, the species were divided into functional hearing groups. The mid-frequency cetacean group includes beluga whales and was derived based on beluga whale data, as data from nine beluga whales was used in creating the composite audiogram in the NMFS Acoustic Guidance. The paper cited by CBD (Mooney et al, 2018) does not illustrate a particular portion of beluga whale hearing range that has been mischaracterized; rather, that paper highlights the amount of variation in hearing sensitivity across individuals within a population. The paper concludes that testing auditory evoked potentials of several individuals in a population is necessary to accurately describe sensitivity and variance in hearing. NMFS agrees that these pieces of information would be crucial in quantifying the sensitivity of Cook Inlet beluga whales, but currently this data does not exist. NMFS uses the best available science in the form of the Acoustic Guidance to determine potential onset of PTS and TTS. Aside from our acoustic thresholds, NMFS can only qualitatively consider the sensitivity of beluga whales to anthropogenic sounds, particularly in light of the potentially high variance in sensitivity across individuals. Because of this uncertainty and lack of data on the sensitivity for the Cook Inlet stock of beluga whales, NMFS is requiring Hilcorp to shut down activities when any beluga is sighted within the relevant Level B harassment isopleth. Regarding density, NMFS carried two potential densities all the way through the analysis—the first based purely on the NMFS summer aerial surveys mentioned in CBD's comment letter, and the second using the aerial surveys as the basis for a model that accounts for beluga whale presence as well as beluga whale count data. While the data is collected in the summer, this is the best scientific information available. Rigorous surveys for Cook Inlet beluga whales outside of summer months are not considered feasible, largely due to safety concerns because of weather conditions. Monitoring reports of previous incidental take authorizations issued in Cook Inlet with take of Cook Inlet beluga whales reveal that sightings of Cook Inlet beluga whales are often substantially lower than the calculated exposure estimate or take authorized. This data, couple with the beluga-specific mitigation measures included in this rule, suggest that take of Cook Inlet belugas is not underestimated. Comment 35: The CBD commented that NMFS relies on avoidance to make its negligible impact determination, while ignoring that avoidance can be a detrimental behavior. Response: NMFS does not rely on avoidance behaviors to make its negligible impact determination. NMFS agrees that avoidance of preferred habitat may temporarily limit optimal feeding or other biologically important behaviors. However, the majority of the proposed activities will occur in habitat that is not known to be of particular significance to Cook Inlet beluga whales. For those activities that are conducted near habitat thought to be important to beluga whale behavior such as mud flats in the Susitna River Delta, a time-area closure will be implemented so beluga whales will be able to access this habitat during the summer, which is when they frequent upper Cook Inlet. In combination, the density of Cook Inlet beluga whales in the area of the activity, which inform the take estimation, coupled with mitigation and monitoring measures and knowledge of the range of Cook Inlet beluga whales during the months of operation proposed by Hilcorp, suggest a finding of negligible impact of these effects on Cook Inlet beluga whales. Comment 36: The CBD commented that NMFS should count all exposures as separate takes, and that counting all exposures of an animal that occur within one day as one take is an underestimate. Response: For the purposes of consistency in estimating the numbers of takes, we do not consider one individual as taken more than one time in a day, even if modeling or direct knowledge might show that an individual would likely be exposed to sound or other stressors in a manner that we would consider a take multiple separate times in one day. For the purposes of analyzing the impacts of these takes to the stock, it is important to understand the likely nature of these instances of take within a day ( e.g., momentary exposure versus multiple hours, high level versus low level of intensity of acoustic exposure). We acknowledge that certain harbor seals are likely to swim in and out of a potentially ensonified area without remaining in the ensonified zone for the entire daily duration of an activity. Also, of note, just because activities continue for hours at a time, that does not mean that mobile marine mammals are exposed (to sometimes mobile sources) for all of those hours, as in many cases they would be expected to move away. While certain species, such as Cook Inlet beluga whales, Steller sea lions, and harbor seals, are known to exhibit site fidelity, Hilcorp's activities are not planned to occur directly in biologically important habitat for any of these marine mammal species in Cook Inlet. Therefore, site fidelity may not automatically equate to increased duration of exposure, especially given the use of mobile sources, as the habitat that animals are likely to frequent, such as important haulouts or river mouths, are near the activity, but primarily are outside of the calculated acoustic isopleths. NMFS requires that data be collected on the number of animals that are taken and the frequency of takes. While NMFS does not anticipate that multiple Level B harassments of the same animal within 2 hours would substantively alter the fitness of that animal, NMFS would request that the frequency of those takes is reported. However, in certain environments or circumstances, such as the use of a mobile source where an individual of a certain species is sighted, not sighted for a number of hours, and sighted again, it is unlikely that, without substantial uniquely identifiable markings, a PSO would know they are sighting a repeat individual. Therefore, in most instances, these sightings would be reported as separate takes during the activity. Comment 37: The CBD commented that NMFS must consider the best available scientific information regarding noise and marine mammals, noting some sources in the proposed rule are decades old. The CBD also commented that NMFS overlooked particularly important references regarding sensitivity of marine mammals to airgun sounds, citing Miller at al. (2005) and Gomez et al. (2016). Response: NMFS has considered the best available science in this rulemaking. Certain papers, particularly papers pertaining to basic physiolology, biology, and acoustics, formed a baseline knowledge that is expanded upon in recent publications. However, the age of certain papers does not negate their validity or quality of science. As appropriate, NMFS considers the best available science and consistently reviews recent literature to inform our analyses. While the papers cited by CBD are part of the general body of literature regarding marine mammals and anthropogenic noise, they each present shortcomings. The Miller et al (2005) paper is a case study of a marine seismic survey in Canadian waters of the Beaufort Sea. Beluga whales were recorded during this study with potential avoidance behaviors recorded at various distances. NMFS does not dispute that avoidance is a potential outcome of seismic activity, as discussed in our Effects on Marine Mammals section below. However, the conclusion of the Miller et al (2005) paper states that the mitigation measures undertaken during the survey, many of which are similar to measures required in this rulemaking, were found to be effective. Additionally, the results of the Gomez et al (2016) paper, suggest that, for the studies reviewed in this paper, received level did not explain the severity of the behavioral response to anthropogenic sound sources. For some sources, including seismic sources, it is possible that distance to the source may have a more direct relationship to a behavioral response than the received level. Gomez et al (2016) ultimately concluded there were insufficient data to identify a dose-response relationship between received level and severity of behavioral response. This supports NMFS' analysis that there is uncertainty in the severity and type of response that animals may exhibit in response to Hilcorp's activities. However, to minimize impacts to the best of our ability, NMFS is implementing mitigation measures in line with those found to be effective in Miller et al (2005). Time-area closures at areas and times of biological importance, airgun shutdowns, and ramp-up of airguns are all measures that are discussed in the paper and that are required in this rule. Comment 38: The CBD commented that the negligible impact statement does not consider: Above-water impacts to seals and sea lions that are hauled out, risk of ship strike from non-source project vessels, entanglement from seismic survey cables, and increased risk of oil spills from the activities. Response: NMFS does not consider above-water acoustic impacts to seals and sea lions in this rulemaking because none are expected, as described in the description of Iniskin Peninsula activities above. None of the proposed activities are likely to result in take from above-water acoustic disturbance in the vicinity of hauled out seals and sea lions, as any animals potentially exposed to those sounds above water would also be exposed to underwater sound that rises to the level of take. Additionally, [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2019-15867. Public record. Not legal advice.