# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Eareckson Air Station Fuel Pier Repair in Alcan Harbor on Shemya Island, Alaska > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2023-23970 ## Record - **Collection:** Federal Register - **Document type:** Notice - **Published:** October 31, 2023 - **Citation:** 88 FR 74451 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration [RTID 0648-XD325] Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Eareckson Air Station Fuel Pier Repair in Alcan Harbor on Shemya Island, Alaska AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Notice; proposed incidental harassment authorization; request for comments on proposed authorization and possible renewal. SUMMARY: NMFS has received a request from the U.S Army Corps of Engineers (USACE) on behalf of the Pacific Air Forces Regional Support Center (USAF) for authorization to take marine mammals incidental to the Eareckson Air Station (EAS) Fuel Pier Repair in Alcan Harbor, Shemya Island, Alaska. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an incidental harassment authorization (IHA) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, 1-year renewal that could be issued under certain circumstances and if all requirements are met, as described in the Request for Public Comments section at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision. DATES: Comments and information must be received no later than November 30, 2023. ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service and should be submitted via email to ITP.Fleming@noaa.gov. Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In case of problems accessing these documents, please call the contact listed below. Instructions: NMFS is not responsible for comments sent by any other method, to any other address or individual, or received after the end of the comment period. Comments, including all attachments, must not exceed a 25-megabyte file size. All comments received are a part of the public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying information ( e.g., name, address) voluntarily submitted by the commenter may be publicly accessible. Do not submit confidential business information or otherwise sensitive or protected information. FOR FURTHER INFORMATION CONTACT: Kate Fleming, Office of Protected Resources, NMFS, (301) 427-8401. SUPPLEMENTARY INFORMATION: 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 proposed or, if the taking is limited to harassment, a notice of a proposed IHA is 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 the 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 the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below. 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 must review our proposed action ( i.e., the issuance of an IHA) with respect to potential impacts on the human environment. This action is consistent with categories of activities identified in Categorical Exclusion B4 (IHAs with no anticipated serious injury or mortality) of the Companion Manual for NAO 216-6A, which do not individually or cumulatively have the potential for significant impacts on the quality of the human environment and for which we have not identified any extraordinary circumstances that would preclude this categorical exclusion. Accordingly, NMFS has preliminarily determined that the issuance of the proposed IHA qualifies to be categorically excluded from further NEPA review. We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on the IHA request. Summary of Request On May 15, 2023, NMFS received a request from the USACE on behalf of USAF for an IHA to take marine mammals incidental to construction associated with the EAS Fuel Pier Repair in Alcan Harbor on Shemya Island, Alaska. Following NMFS' review of the application, and discussions between NMFS and USAF, the application was deemed adequate and complete on September 19, 2023. The USAF's request is for take of 12 species of marine mammals, by Level B harassment and, for a subset of these species, Level A harassment. Neither USAF nor NMFS expect serious injury or mortality to result from this activity and, therefore, an IHA is appropriate. This proposed IHA would cover 1 year of a larger 3-year project that involves construction activities that will not result in the take of marine mammals ( i.e., movement, mobilization, and staging of equipment; replacing the pier deck; and installing an engineered revetment along the western shoreline). Description of Proposed Activity Overview The USAF is proposing to conduct long-term repairs on the only existing fuel pier at EAS on Shemya Island, Alaska. The fuel delivered to the pier is used by the island generator systems to aid in the operation of homeland defense early warning radar surveillance and communication systems. EAS also functions as an emergency divert airfield supporting commercial and air traffic destined for Japan, China, and other destinations in Asia and the Pacific. In February 2020, a destructive storm left the fuel pier in critical condition. In 2021, emergency repairs were completed to restore minimal function to the fuel pier. Long-term repairs are planned in order to prevent future degradation and catastrophic loss to the fuel pier, to maintain access to the pier, and to protect the shoreline facilities from further erosion. The activities that have the potential to take marine mammals, by Level A harassment and Level B harassment, include down-the-hole (DTH) drilling, vibratory and impact installation of temporary and permanent steel pipe piles, and vibratory removal of temporary steel pipe piles, and would introduce underwater sounds that may result in take, by Level A harassment and Level B harassment, of marine mammals. The marine construction associated with the proposed activities is planned to occur over 160 days over 1 year, accounting for weather delays and mechanical issues. Dates and Duration The proposed IHA would be effective from April 1, 2024 to March 31, 2025. The project would occur between April and October 2024 and would require approximately 160 days of pile driving. In-water construction activities would only occur during daylight hours, and typically over a 12-hour work day, up to 7 days per week. Specific Geographic Region The proposed activities would occur on the EAS Fuel Pier on Shemya Island, located in Section 16, Township 86 South, Range 257 West, of the Seward Meridian, Alaska. Shemya Island is a remote island in the western Aleutians. The fuel pier is located in Alcan Harbor, which opens to Shemya Pass to the west and the Bering Sea to its north and east. Alcan harbor is exposed to strong north winds. The dimensions of the new Pier footprint would be approximately 30 by 104 meters (m), or 100 by 340 feet (ft). Depths at the project site range from 5 to 10 m (16 to 33 ft). However, the area of impact would extend 40 kilometers (km), or 25 miles (mi), into the southwest portion of the Bering Sea, reaching depths of approximately 3,900 m (2.4 mi). Shemya Island and its waters are within the Alaska Maritime National Wildlife Refuge, which if not for it being a military base, would typically be under the jurisdiction of U.S. Fish and Wildlife Service (USFWS, 2021). The fuel pier is the only pier on Shemya Island; there are no neighboring piers or docks. The next nearest developed location that is inhabited is Nikol'skoe, which is approximately 370 mi (595 km) west on Bering Island, Russia. Adak, Alaska, is approximately 400 mi (644 km) to the east in the Central Aleutians. The United States Coast Guard previously maintained a long-range navigation station on Attu Island, Alaska, 28 mi (45 km) to the west, but that site has been abandoned for several years. All former Alaska Native village sites in the region have been abandoned since World War II. BILLING CODE 3510-22-P EN31OC23.000 EN31OC23.001 BILLING CODE 3510-22-C Detailed Description of the Specified Activity The USAF is proposing to repair the fuel pier at EAS on Shemya Island, Alaska. As noted above, this proposed IHA would authorize take associated with Year 1 of a larger 3-year project. Please refer to USAF's application for additional information about project components planned for the period beyond Year 1. The USAF estimates that Year 1 activities would include vessel movement and mobilization; pile installation for the fuel pier, screening and clearance for Munitions and Explosives of Concern (MEC) (see explanation below), remote equipment operations, removal of existing precast dolosse from the western shoreline, and crushing/recycling concrete. The replacement fuel pier is within a Military Munitions Response Program (MMRP) site and although prior surveys and clearance of the Alcan Harbor Ordnance MMRP site have been completed, there is potential for munitions and explosives of concern to migrate within the site. As such, magnetometer-based surveys for MEC will be conducted prior to ground disturbing activities within the boundaries of the MMRP site to detect anomalies and inform follow-on actions to the extent practicable. Excavated material from in-water work will be further screened and cleared to remove any potential MEC. The material would be excavated with a clamshell bucket and placed in a hopper that deposits the material onto a conveyor leading to a 6-inch remote controlled grizzly rock screener. Subsequently, material six inches or larger would be inspected by UXO technicians for MEC prior to transfer by armored equipment to a screening plant with a specialized magnet belt to remove all potential metals and munitions. Cleared material would be transferred to an upland, low-grade staging area while MEC would be transferred from the construction site to the MEC storage and disposal site. Additionally, USAF anticipates approximately five vessels ( i.e., tugboats towing barges) per season would be used for project activities, transiting between Seattle, WA and Shemya Island, AK, with some trips making a stop in Seward, Kodiak, or Anchorage, AK. With the exception of pile driving, these activities are not anticipated to result in take. The proposed fuel pier replacement project would include the installation of an interlocking steel pipe combi-wall system, which will require the installation and removal of 60 30-inch (in) temporary steel pipe piles and the installation of 208 42-inch round steel interlocking pipe piles using vibratory, impact, and/or DTH methods (table 1). USAF does not plan to operate multiple hammers concurrently. The interlocking steel pipe combi-wall system would be installed 15 ft (4.6 m) off the existing fuel pier to encapsulate most of the existing structure. The steel combi-wall system would extend approximately 560 ft (171 m) from the northern bulkhead corner, along the entire Pier berthing face, and around the northern perimeter. Template frames for the pile wall would be installed to construct the new pier exterior structure and subsequently removed; template frames would be constructed to cantilever off the existing fuel pier structure ( i.e., not be placed in the water). However, up to 60 30-inch (76-cm) template piles may be installed in the water to provide additional support. A remotely operated vibratory pile driving hammer would be used to drive the piles through the bottom sediment to specified depths. It is anticipated that a diesel or hydraulic impact hammer would be utilized to achieve the specified embedment depth of 44 temporary piles. Up to six temporary piles in the southeast corner, where there is very little overburden, would likely need to be rock socketed into bedrock via a DTH. The main component of the combi-wall system would require the installation of 208 42-inch (107-cm) interlocking permanent steel pipe piles that would be installed using vibratory and impact pile driving to specified embedment depths. The pile interlocks would be designed to transfer soil and water pressure to the interlocking steel pipe piles, which would carry most of the load. In addition to vibratory and impact pile driving, it is expected that most, if not all permanent piling will require a rock socket into the bedrock, at a minimum of 30 ft (9 m) below the mudline, using a DTH hammer and bit. The bit will be slightly larger than the outside diameter of the permanent pipe pile. Construction of the proposed dock would follow this sequence: 1. Set one or two cantilevered templates utilizing existing fuel pier as support. These cantilevered templates would not be installed in the water. However, template piles may be installed in some areas to offer additional support (table 1). 2. Within the frame, loft and stab 6-12 each 42-inch permanent pile. 3. Within the frame, vibrate, impact, and DTH drill 42-inch diameter pipe pile. Only one pile would be driven at a time, even if two pile templates are used. 4. Remove the frame and any temporary piles and move to the next permanent pile location. 5. Repeat this process for placement of all the permanent piles. Table 1—Summary of Piles To Be Installed and Removed Installation or removal Number of piles Impact strikers per pile Vibratory duration per pile, minutes DTH pile installation, duration per pile, minutes Maximum piles per day— impact pile driving Maximum piles per day— vibratory pile driving Maximum piles per day—DTH pile installation Days of installation and/or removal a 42-inch Interlocking Steel Pipe Piles—Permanent Installation 208 1,800 30 180 4 4 3 122 30-inch Steel Pipe Piles—Template Installation 60 900 15 150 4 4 3 17 Removal 4 a USAF estimates a total of 160 construction days to account for weather delays and mechanical issues. Proposed mitigation, monitoring, and reporting measures are described in detail later in this document (please see Proposed Mitigation and Proposed Monitoring and Reporting sections). Description of Marine Mammals in the Area of Specified Activities Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments ) and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/find-species ). Table 2 lists all species or stocks for which take is expected and proposed to be authorized for this activity, and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or proposed to be authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats. Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Alaska 2022 SARs (Young et al., 2023). All values presented in table 2 are the most recent available at the time of publication and are available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments. Table 2—Species Likely Impacted by the Specified Activities Common name Scientific name Stock ESA/MMPA status; strategic (Y/N) 1 Stock abundance (CV, N min , most recent abundance survey) 2 PBR Annual M/SI 3 Order Artiodactyla—Infraorder Cetacea—Mysticeti (baleen whales) Family Balaenopteridae Fin Whale Balaenoptera physalus Northeast Pacific E, D, Y UND (UND, UND, 2013) 4 UND 0.6 Humpback Whale Megaptera novaeangliae Western North Pacific E, D, Y 1,084, (0.088, 1,007, 2006) 3 2.8 Mexico—North Pacific T, D, Y N/A (N/A, N/A, 2006) 5 UND 0.56 Hawai'i -, -, N 11,278 (0.56, 7,265, 2020) 127 19.6 Minke Whale Balaenoptera acutorostrata Alaska -, -, - N/A (N/A, N/A, N/A) 6 UND 0 Odontoceti (toothed whales, dolphins, and porpoises) Family Physeteridae Sperm whale Physeter macrocephalus North Pacific E, D, Y UND (UND, UND, 2015) 7 UND 3.5 Family Ziphiidae (beaked whales) Baird's beaked whale Berardius bairdii Alaska -, -, N N/A (N/A, N/A, N/A) 8 N/A 0 Stejneger's Beaked Whale Mesoplodon stejnegeri Alaska -, -, N N/A (N/A, N/A, N/A) 8 N/A 0 Family Delphinidae Killer Whale Orcinus orca ENP Alaska Resident Stock -, -, N 1,920 (N/A, 1,920, 2019) 19 1.3 ENP Gulf of Alaska, Aleutian Islands, and Bering Sea -, -, N 587 (N/A, 587, 2012) 5.9 0.8 Family Phocoenidae (porpoises) Dall's Porpoise Phocoenoides dalli Alaska -, -, N UND (UND, UND, 2015) 9 UND 37 Harbor Porpoise Phocoena phocoena Bering Sea -, -, Y UNK (UNK, N/A, 2008) 10 UND 0.4 Order Carnivora—Pinnipedia Family Otariidae (eared seals and sea lions) Northern Fur Seal Callorhinus ursinus Eastern Pacific -, D, Y 626,618 (0.2, 530,376, 2019) 11,403 373 Steller Sea Lion Eumetopias jubatus Western, U.S E, D, Y 52,932 (N/A, 52,932, 2019) 318 254 Family Phocidae (earless seals) Harbor Seal Phoca vitulina Aleutian Islands -, -, N 5,588 (N/A, 5,366, 2018) 97 90 1 Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. 2 NMFS marine mammal stock assessment reports online at: https://www.nmfs.noaa.gov/pr/sars/. CV is coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, CV is not applicable (explain if this is the case). 3 These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined ( e.g., commercial fisheries, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases. 4 The best available abundance estimate for this stock is not considered representative of the entire stock as surveys were limited to a small portion of the stock's range. Based upon this estimate and the Nmin, the PBR value is likely negatively biased for the entire stock. 5 Abundance estimates are based upon data collected more than 8 years ago and therefore current estimates are considered unknown. 6 Reliable population estimates are not available for this stock. Please see Friday et al. (2013) and Zerbini et al. (2006) for additional information on numbers of minke whales in Alaska. 7 The most recent abundance estimate is likely unreliable as it covered a small area that may not have included females and juveniles, and did not account for animals missed on the trackline. The calculated PBR is not a reliable index for the stock as it is based upon negatively biased minimum abundance estimate. 8 Reliable abundance estimates for this stock are currently unavailable. 9 The best available abundance estimate is likely an underestimate for the entire stock because it is based upon a survey that covered only a small portion of the stock's range. 10 The best available abundance estimate and Nmin are likely an underestimate for the entire stock because it is based upon a survey that covered only a small portion of the stock's range. PBR for this stock is undetermined due to this estimate being older than 8 years. As indicated above, all 12 species (with 15 managed stocks) in table 2 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. All species that could potentially occur in the proposed project area are included in table 3-1 of the IHA application. While blue whale, gray whale, North Pacific right whale, Pacific white-sided dolphin, and ribbon seal could occur in the area, the temporal and/or spatial occurrence of these species is such that take is not expected to occur, and they are not discussed further beyond the explanation provided here. These species all have extremely low abundance and most are observed in areas outside of the project area. In addition, northern sea otter may be found the western Aleutians. However, this species is managed by the U.S. Fish and Wildlife Service and is not considered further in this document. Fin Whale Fin whales are found in polar, temperate, and subtropical waters worldwide, where they inhabit deep, offshore waters and often travel in open seas away from coasts. Fin whales in the northeast Pacific are typically distributed off the coast of the Gulf of Alaska and the Bering and Chukchi Seas. In general, the spring and early summer are spent in cold, high latitude feeding waters as far north as Chukchi Sea, the Gulf of Alaska, Prince William Sound, along the Aleutian Islands, and west of Kodiak Island. In the fall, fin whales return to low latitudes for the winter breeding season, though they may remain in residence in their high latitude ranges if food resources remain plentiful. Although typically observed in groups of 6 to 10 individuals, fin whales are also sighted in pairs, alone, or in feeding aggregations up to 100 individuals. In the central eastern Bering Sea, most sightings have occurred along the continental shelf break in a zone of high prey abundance (Clark, 2008a). Across 119 days of three distinct marine mammal surveys completed from Shemya Island between 2016 and 2021, no fin whales were observed in the project area (see application). Note that Alcan harbor was included in island-wide monitoring of two of these surveys, and the third survey effort was conducted exclusively at the project site during an emergency repair of the fuel pier. Humpback Whale On September 8, 2016, NMFS divided the once single population into 14 distinct population segments (DPS) under the ESA, removed the species-level listing as endangered, and, in its place, listed four DPSs as endangered and one DPS as threatened (81 FR 62259, September 8, 2016). The remaining nine DPSs were not listed. There are four DPSs in the North Pacific, including the Western North Pacific and Central America, which are listed as endangered, Mexico, which is listed as threatened, and Hawai'i, which is not listed. The 2022 Alaska and Pacific SARs described a revised stock structure for humpback whales which modifies the previous stocks designated under the MMPA to align more closely with the ESA-designated DPSs (Caretta et al., 2023; Young et al., 2023). Specifically, the three previous North Pacific humpback whale stocks (Central and Western North Pacific stocks and a CA/OR/WA stock) were replaced by five stocks, largely corresponding with the ESA-designated DPSs. These include the Western North Pacific and Hawai'i stocks and a Central America/Southern Mexico—CA/OR/WA stock (which corresponds with the Central America DPS). The remaining two stocks, corresponding with the Mexico DPS, are the Mainland Mexico—CA/OR/WA and Mexico—North Pacific stocks (Caretta et al., 2023; Young et al., 2023). The former stock is expected to occur along the west coast from California to southern British Columbia, while the latter stock may occur across the Pacific, from northern British Columbia through the Gulf of Alaska and Aleutian Islands/Bering Sea region to Russia. The Hawai'i stock consists of one demographically independent population (DIP)—Hawai'i—Southeast Alaska/Northern British Columbia DIP and one unit—Hawai'i—North Pacific unit, which may or may not be composed of multiple DIPs (Wade et al., 2021). The DIP and unit are managed as a single stock at this time, due to the lack of data available to separately assess them and lack of compelling conservation benefit to managing them separately (NMFS, 2023; NMFS, 2019; NMFS, 2022b). The DIP is delineated based on two strong lines of evidence: genetics and movement data (Wade et al., 2021). Whales in the Hawai'i—Southeast Alaska/Northern British Columbia DIP winter off Hawai'i and largely summer in Southeast Alaska and Northern British Columbia (Wade et al., 2021). The group of whales that migrate from Russia, western Alaska (Bering Sea and Aleutian Islands), and central Alaska (Gulf of Alaska excluding Southeast Alaska) to Hawai'i have been delineated as the Hawai'i—North Pacific unit (Wade et al., 2021). There are a small number of whales that migrate between Hawai'i and southern British Columbia/Washington, but current data and analyses do not provide a clear understanding of which unit these whales belong to (Wade et al., 2021; Caretta et al., 2023; Young et al., 2023). The Mexico—North Pacific unit is likely composed of multiple DIPs, based on movement data (Martien et al., 2021; Wade, 2021; Wade et al., 2021). However, because currently available data and analyses are not sufficient to delineate or assess DIPs within the unit, it was designated as a single stock (NMFS, 2023a; NMFS, 2019; NMFS, 2022c). Whales in this stock winter off Mexico and the Revillagigedo Archipelago and summer primarily in Alaska waters (Martien et al., 2021; Carretta et al., 2023; Young et al., 2023). The Western North Pacific stock consists of two units—the Philippines/Okinawa—North Pacific unit and the Marianas/Ogasawara—North Pacific unit. The units are managed as a single stock at this time, due to a lack of data. Recognition of these units is based on movements and genetic data (Oleson et al., 2022). Whales in the Philippines/Okinawa—North Pacific unit winter near the Philippines and in the Ryukyu Archipelago and migrate to summer feeding areas primarily off the Russian mainland (Oleson et al., 2022). Whales that winter off the Mariana Archipelago, Ogasawara, and other areas not yet identified and then migrate to summer feeding areas off the Commander Islands, and to the Bering Sea and Aleutian Islands comprise the Marianas/Ogasawara—North Pacific unit. Humpback whales that occur in the project area are predominantly members of the Hawai'i stock, which corresponds to the Hawai'i DPS (91 percent probability in the Aleutian Islands), and is not listed under the ESA. However, members of the Mexico North Pacific stock, which include the Mexico DPS and is listed as threatened, have a small potential to occur in the project location (7 percent probability in the Aleutians), and the Western North Pacific Stock, which corresponds to the Western North Pacific DPS and is listed as endangered, have an even smaller potential to occur in the project location (2 percent, Wade, 2021). Humpback whales migrate to the North Pacific, including the Aleutian Islands, to feed after months of fasting in equatorial breeding grounds. Humpback whales generally travel alone or in small groups that persist only a few hours. Groups may stay together for longer in the summer in order to feed cooperatively. During the 2016 and 2021 Shemya Island marine mammal surveys, seven humpback whales were observed in the project area (see application). Minke Whale Minke whales occur in polar, temperate, and tropical waters worldwide in a range extending from the ice edge in the Arctic during the summer to near the equator during winter. However, they are known to prefer temperate to boreal waters due to the abundance of prey (Guerrero, 2008b). When comparing distribution and abundance in the years 2002, 2008, and 2010, it was found that that minke whales were scattered throughout all oceanographic domains: coastal, middle shelf, and outer shelf/slope (Muto et al., 2021). The minke whale mostly migrates seasonally and can travel long distances; although, some minke whale individuals and stocks have resident home ranges and are not highly migratory (Guerrero, 2008b). The Alaska Stock of minke whales are migratory and are common in the waters of the Bering Sea, Gulf of Alaska, and Southeast Alaska in the spring and summer (NMFS, 2023c). The distribution of minke whales vary according to age, sex, and reproductive status. Older mature males are commonly found in small social groups around the ice edge of polar regions during the summer feeding season. Comparatively, adult females will migrate farther into the higher latitudes but generally remain in coastal waters. Immature minke whales tend to be solitary and stay in lower latitudes during the summer (Guerrero, 2008b). Although the minke whale tends to be solitary or in groups of two to three individuals, they can congregate in larger groups containing up to 400 individuals at the higher latitude foraging areas (NOAA, 2021). During surveys in Alaska, minke whales are predominately observed alone (Wade et al., 2003; Waite, 2003). Breeding season typically occurs from December to March, but in some regions minke whales breed year-round. When migrating north in spring and summer, they will travel along in coastal waters, whereas in fall and winter, they move farther offshore (NMFS, 2023c). In 2003, a minke whale was observed in July when a sea otter survey was being conducted at Attu Island (Doroff et al., 2004), 28 mi to the west of Shemya Island. During the 2016 and 2021 Shemya Island marine mammal surveys, no minke whales were observed in the project area (see application). Sperm Whale Sperm whales are the most sighted and recorded cetacean in marine mammal surveys in high latitude regions of the North Pacific, including the Bering Sea and the Aleutian Islands (Young et al., 2023). However, sperm whales exhibit sex-specific latitudinal segregation, where females and their young form social groups and are usually found in temperate and tropical latitudes, while males forage at higher latitudes and tends to only return to tropical and subtropical regions to breed (Whitehead, 2009). As such, males are more frequently encountered in the Aleutians than females; social groups typically occur in this area only during the winter when males are less likely to be present (Posdalijian, 2023). Sperm whales tend to occur offshore in submarine canyons at the edge of the continental shelf in water 1,000 m (3,300 ft) deep (Jaquet and Whitehead, 1996). They hunt for food during deep dives that routinely reach depths of 2,000 feet and can last for 45 minutes. Because sperm whales spend most of their time in deep waters, their diet consists of species such as squid, sharks, skates, and fish that also occupy deep ocean waters. The Aleutian Islands are considered a biologically important area (BIA) for feeding for sperm whale (Brower, 2022). This BIA overlaps with the project area and is active April through September. The BIA scored a three for importance and intensity, and a two for data support and boundary certainty, indicating that it is of high importance, has moderately certain boundaries, and moderate data to support the identification of the BIA (see Harrison et al. (2023) for additional information about the scoring process used to identify BIAs). The BIA was identified as having dynamic spatiotemporal variability. During the 2016 and 2021 marine mammal surveys completed on Shemya Island, four sperm whales were observed on a single day (see application). Baird's Beaked Whale Baird's beaked whale occurs in the North Pacific and Bering Sea along the Aleutian Islands as well as the adjacent waters of the Gulf of Alaska, Sea of Okhotsk, and the Sea of Japan (Guerrero, 2008a). Within the North Pacific Ocean, Baird's beaked whales have been sighted north of 30° N in deep, cold waters over the continental shelf (Muto et al., 2021), particularly in regions with 1,000 m (3,300 ft) or deeper contours, submarine canyons, and seamounts. However, they can be occasionally found in nearshore environments along narrow continental shelves. Baird's beaked whales migrate seasonally based on the temperature of surface water (NMFS, 2023a). They occur in waters of the continental slope during summer and fall months when surface water temperatures are the highest (Muto et al., 2021). They have also been observed in the nearshore waters of the Bering Sea and Okhotsk Sea in May to October (NMFS, 2023a). Baird's beaked whales are usually found in tight social groups (schools or pods) averaging between five and 20 individuals, but they have occasionally been observed in larger groups of up to 50 animals. During the 2016 and 2021 Shemya Island marine mammal surveys, no Baird's beaked whales were observed in the project area (see application). Stejneger's Beaked Whale Stejneger's beaked whale prefer cold, temperate, and subarctic waters of the North Pacific Ocean and are generally found in deep, offshore waters on or beyond the continental slope between 2,500 and 5,000 ft. Most records are from Alaskan waters, and the Aleutian Islands appear to be its center of distribution (Mead, 1989; Wade et al., 2003).They are usually found in small, tight social groups averaging between 5 and 15 individuals. This whale is rarely sighted at sea, but they have been detected acoustically in the Aleutian waters in summer, fall, and spring (Baumann-Pickering et al., 2014; Muto, 2021). Most data on Stejneger's beaked whale have been collected and inferred from stranded individuals. Though most strandings in the Aleutians occur in the central portion of the island chain, there was a stranding of an adult male Stejneger's beaked whale on the southeast coast of Shemya Island on September 1, 2005 (Savage et al., 2021). During the 2016 and 2021 marine mammal surveys completed on Shemya Island, no Stejneger's beaked whale were observed. Killer Whale Killer whales occur in every ocean in the world and are the most widely distributed of all cetaceans. Along the west coast of North America, killer whales occur along the entire Alaska coast (Braham and Dahlheim, 1982). This proposed IHA considers only the Eastern North Pacific Alaska Resident stock (Alaska Resident stock), and the Eastern North Pacific Gulf of Alaska, Aleutian Islands and Bering Sea Transient stocks because all other killer whale stocks occur outside the geographic area under consideration (Muto et al., 2021). There are three distinct ecotypes, or forms, of killer whales recognized: Resident, Transient, and Offshore. The three ecotypes differ morphologically, ecologically, behaviorally, and genetically. Spatial distribution has been shown to vary among the different ecotypes, with resident and, to a lesser extent, transient killer whales more commonly observed along the continental shelf, and offshore killer whales more commonly observed in pelagic waters (Rice et al., 2021). When comparing movement, residents tend to have more predictable movements and the smallest home ranges and they return annually, whereas transients are less predictable due to their larger home ranges and quick transits through local areas. Offshore ecotypes have the largest home ranges that are generally farther offshore compared to the other two ecotypes. (Zimmerman and Small, 2008). Resident killer whales live in large, stable groups ranging normally from 5 to 50 individuals and up to 100 or more. They feed only on fish, especially Pacific salmon. Transient killer whales, on the other hand, hunt marine mammals, like pinnipeds and porpoises, in smaller groups of 10 individuals or less (Forney and Wade, 2006). During the 2016 and 2021 marine mammal surveys at Shemya Island, Killer whales were frequently documented within the project area and around the island during these surveys. Within the project area alone, the average daily observation rate was 0.6 killer whales (see application). Dall's Porpoise Dall's porpoises are widely distributed across the North Pacific Ocean, ranging from Japan to southern California and up to Alaska and the Bering Sea in coastal and pelagic waters between 28° N and 65° N (Wells, 2008; Muto et al., 2021). They inhabit all strata on the continental shelf, slope, and pelagic waters with the greatest densities occurring in deeper inshore and slope habitats (Rone et al., 2017). Throughout most of the eastern North Pacific they are present during all months of the year, although there may winter movements out of areas of ice like Prince William Sound and the Bering Sea or onshore-offshore movements along the west coast of the continental U.S. (Muto et al., 2021). Depending on morphology/type, geography, and seasonality, they have inshore-offshore and north-south migration patterns (NMFS, 2023b). They generally travel in groups of 10 to 20 individuals but can occur in groups with over hundreds of individuals (Wells, 2008). These groups appear to be fluid as they form and break-up during play and feeding. During the 2016 and 2021 Shemya Island marine mammal surveys, no Dall's porpoise were observed in the project area (see application) Harbor Porpoise The Bering Sea stock of harbor porpoise occurs within the project area, ranging from throughout the Aleutian Islands and into all waters north of Unimak Pass. The harbor porpoise frequents nearshore waters and coastal embayments throughout their range, including bays, harbors, estuaries, and fjords less than 650 ft (198 m) deep (NMFS, 2023d). They are most often observed in groups of two or three. During the 2016 and 2021 marine mammal surveys completed on Shemya Island, one group of two to three harbor porpoise were observed (see application). Northern Fur Seal Northern fur seals occur from southern California north to the Bering Sea and west to the Sea of Okhotsk and Honshu Island, Japan. They are highly pelagic, spending most of their time each year alone at sea. During the summer breeding season, most of the worldwide population is found on the Pribilof Islands in the southern Bering Sea, with the remaining animals on rookeries in Russia, on Bogoslof Island in the southern Bering Sea, on San Miguel Island off southern California (Lander and Kajimura, 1982; NMFS, 1993), and on the Farallon Islands off central California. Non-breeding northern fur seals may occasionally haul out on land at other sites in Alaska, British Columbia, and on islets along the west coast of the United States (Fiscus, 1983). During the reproductive season, adult males usually are on shore during the 4-month period from May to August, although some may be present until November. Adult females are ashore during a 6-month period (June-November). Following their respective times ashore, Alaska northern fur seals of both genders the move south and remain at sea until the next breeding season (Roppel, 1984). Adult females and pups from the Pribilof Islands move through the Aleutian Islands into the North Pacific Ocean, often to the waters offshore of Oregon and California (Ream et al., 2005). Adult males generally move only as far south as the Gulf of Alaska in the eastern North Pacific (Kajimura, 1984) and the Kuril Islands in the western North Pacific (Loughlin et al., 1999). In Alaska, pups are born during the summer months and leave the rookeries in the fall, on average around mid-November. They generally remain at sea for 22 months before returning to land (Kenyon and Wilke, 1953). During the 2016 and 2021 marine mammal surveys completed on Shemya Island, no northern fur seals were observed (see application). Steller Sea Lion Steller sea lions in the project area are anticipated to be from the Western stock, which includes all Steller sea lions originating from rookeries west of Cape Suckling (144° W longitude). The centers of abundance and distribution for western DPS Steller sea lions are located in the Gulf of Alaska and Aleutian Islands. At sea, Steller sea lions commonly occur near the 656-ft (200-m) depth contour but have been found from nearshore to well beyond the continental shelf (Kajimura and Loughlin, 1988). Sea lions move offshore to pelagic waters for feeding excursions. Steller sea lions are frequently observed around Shemya Island outside of the ensonified area, though only occasionally observed in low numbers in Alcan Harbor and Shemya Pass (see application). The ensonified area would intersect with the aquatic zone of Steller sea lion haulouts designated as critical habitat. The Shemya Island Major Haulout is 2.75 nmi to the east of the project site, Alaid Island Major Haulout is 5 nmi northwest of the project site, and Attu/Chirikof Point Major Haulout is 24 nmi to the northwest of the project site. However, no Steller sea lions have been observed on the Shemya Island Major Haulout during surveys completed between 2015 and 2017, and only one Steller sea lion was observed at Attu/Chirkock Point during surveys conducted during the same time frame. An average of 68 non-pups and 7 pups were observed annually during this time at Alaid Island Major Haulout (see application). Harbor Seal Harbor seals inhabit coastal and estuarine waters off Alaska. They haul out on rocks, reefs, beaches, and drifting glacial ice. They are generally non-migratory, with local movements associated with such factors as tides, weather, season, food availability, and reproduction (Muto et al., 2021). They are opportunistic feeders and often adjust their distribution to take advantage of locally and seasonally abundant prey (Womble et al., 2010; Allen and Angliss, 2015). Although they tend to be solitary when in the water, they can form groups of about 30 or less individuals of both sexes and all ages when hauling out. Harbor seals haul out to rest periodically, give birth or nurse. Harbor seals in the project area are recognized as part of the Aleutian Island stock, occurring along the entire Aleutian island chain from Attu Island to Ugamak Island. Pupping season in the Aleutian Islands is occurs between mid-June to mid-July. (Sease, 1992). Harbor seals haul out on beaches all around Shemya Island, with largest numbers observed on the east side of the island, away from the ensonified area. However, harbor seals are occasionally observed occurring inside the ensonified area. During the 2016 and 2021 marine mammal surveys completed on Shemya Island, an average of 0.45 harbor seals were observed each day. Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities ( e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling, etc. ). Note that no direct measurements of hearing ability have been successfully completed for mysticetes ( i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65-decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall et al. (2007) retained. Marine mammal hearing groups and their associated hearing ranges are provided in table 3. Table 3—Marine Mammal Hearing Groups [NMFS, 2018] Hearing Group Generalized Hearing Range * Low-frequency (LF) cetaceans (baleen whales) 7 Hz to 35 kHz Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) 150 Hz to 160 kHz High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis ) 275 Hz to 160 kHz Phocid pinnipeds (PW) (underwater) (true seals) 50 Hz to 86 kHz Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) 60 Hz to 39 kHz * Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65-dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall et al., 2007) and PW pinniped (approximation). The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 2013). For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information. Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section provides a discussion of the ways in which components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival. Acoustic effects on marine mammals during the specified activity can occur from impact and vibratory pile driving and removal and DTH. The effects of underwater noise from USAF's proposed activities have the potential to result in Level A harassment and Level B harassment of marine mammals. Description of Sound Sources The marine soundscape is comprised of both ambient and anthropogenic sounds. Ambient sound is defined as the all-encompassing sound in a given place and is usually a composite of sound from many sources both near and far (American National Standards Institute 1995). The sound level of an area is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical ( e.g., waves, wind, precipitation, earthquakes, ice, atmospheric sound), biological ( e.g., sounds produced by marine mammals, fish, and invertebrates), and anthropogenic sound ( e.g., vessels, dredging, aircraft, construction). The sum of the various natural and anthropogenic sound sources at any given location and time—which comprise “ambient” or “background” sound—depends not only on the source levels (as determined by current weather conditions and levels of biological and shipping activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor, and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10 to 20 dB from day to day (Richardson et al., 1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. In-water construction activities associated with the project would include impact pile driving, vibratory pile driving and removal, and use of DTH equipment. The sounds produced by these activities fall into one of two general sound types: Impulsive and non-impulsive. Impulsive sounds ( e.g., explosions, gunshots, sonic booms, impact pile driving) are typically transient, brief (less than 1 second), broadband, and consist of high peak sound pressure with rapid rise time and rapid decay (American National Standards Institute (ANSI), 1986; National Institute of Occupational Safety and Health (NIOSH), 1998; NMFS, 2018). Non-impulsive sounds ( e.g., aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems) can be broadband, narrowband or tonal, brief or prolonged (continuous or intermittent), and typically do not have the high peak sound pressure with rapid rise/decay time that impulsive sounds do (ANSI, 1995; NIOSH, 1998; NMFS, 2018). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing ( e.g., Ward 1997 in Southall et al., 2007). Three types of hammers would be used on this project: impact, vibratory, and DTH. Impact hammers operate by repeatedly dropping and/or pushing a heavy piston onto a pile to drive the pile into the substrate. Sound generated by impact hammers is characterized by rapid rise times and high peak levels, a potentially injurious combination (Hastings and Popper, 2005). Vibratory hammers install piles by vibrating them and allowing the weight of the hammer to push them into the sediment. Vibratory hammers produce significantly less sound than impact hammers. Peak Sound Pressure Levels (SPLs) may be 180 dB or greater, but are generally 10 to 20 dB lower than SPLs generated during impact pile driving of the same-sized pile (Oestman et al., 2009). Rise time is slower, reducing the probability and severity of injury, and sound energy is distributed over a greater amount of time (Nedwell and Edwards, 2002; Carlson et al., 2005). A DTH hammer is essentially a drill bit that drills through the bedrock using a rotating function like a normal drill, in concert with a hammering mechanism operated by a pneumatic (or sometimes hydraulic) component integrated into to the DTH hammer to increase speed of progress through the substrate ( i.e., it is similar to a “hammer drill” hand tool). The sounds produced by the DTH method contain both a continuous, non-impulsive component from the drilling action and an impulsive component from the hammering effect. Therefore, we treat DTH systems as both impulsive and continuous, non-impulsive sound source types simultaneously. The likely or possible impacts of USAF's proposed activities on marine mammals could be generated from both non-acoustic and acoustic stressors. Potential non-acoustic stressors include the physical presence of the equipment, vessels, and personnel; however, any impacts to marine mammals are expected to primarily be acoustic in nature. Acoustic stressors include effects of heavy equipment operation during pile installation and removal and DTH. Acoustic Impacts The introduction of anthropogenic noise into the aquatic environment from pile driving and removal and DTH equipment is the primary means by which marine mammals may be harassed from USAF's specified activities. In general, animals exposed to natural or anthropogenic sound may experience behavioral, physiological, and/or physical effects, ranging in magnitude from none to severe (Southall et al., 2007). Generally, exposure to pile driving and removal and DTH noise has the potential to result in behavioral reactions ( e.g., avoidance, temporary cessation of foraging and vocalizing, changes in dive behavior) and, in limited cases, auditory threshold shifts. Exposure to anthropogenic noise can also lead to non-observable physiological responses such as an increase in stress hormones. Additional noise in a marine mammal's habitat can mask acoustic cues used by marine mammals to carry out daily functions such as communication and predator and prey detection. The effects of pile driving and removal and DTH noise on marine mammals are dependent on several factors, including, but not limited to, sound type ( e.g., impulsive vs. non-impulsive), the species, age and sex class ( e.g., adult male vs. mother with calf), duration of exposure, the distance between the pile and the animal, received levels, behavior at time of exposure, and previous history with exposure (Wartzok et al., 2003; Southall et al., 2007). Here we discuss physical auditory effects (threshold shifts) followed by behavioral effects and potential impacts on habitat. NMFS defines a noise-induced threshold shift (TS) as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018). The amount of threshold shift is customarily expressed in dB. A TS can be permanent or temporary. As described in NMFS (2018), there are numerous factors to consider when examining the consequence of TS, including, but not limited to, the signal temporal pattern ( e.g., impulsive or non-impulsive), likelihood an individual would be exposed for a long enough duration or to a high enough level to induce a TS, the magnitude of the TS, time to recovery (seconds to minutes or hours to days), the frequency range of the exposure ( i.e., spectral content), the hearing and vocalization frequency range of the exposed species relative to the signal's frequency spectrum ( i.e., how animal uses sound within the frequency band of the signal; e.g., Kastelein et al., 2014), and the overlap between the animal and the source ( e.g., spatial, temporal, and spectral). Permanent Threshold Shift (PTS) —NMFS defines PTS as a permanent, irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018). Available data from humans and other terrestrial mammals indicate that a 40-dB threshold shift approximates PTS onset (Ward et al., 1958; Ward et al., 1959; Ward, 1960; Kryter et al., 1966; Miller, 1974; Henderson et al., 2008). PTS levels for marine mammals are estimates, because there are limited empirical data measuring PTS in marine mammals ( e.g., Kastak et al., 2008), largely due to the fact that, for various ethical reasons, experiments involving anthropogenic noise exposure at levels inducing PTS are not typically pursued or authorized (NMFS, 2018). Temporary Threshold Shift (TTS) —A temporary, reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018). Based on data from cetacean TTS measurements (Southall et al., 2007), a TTS of 6 dB is considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Schlundt et al., 2000; Finneran et al., 2000; Finneran et al., 2002). As described in Finneran (2016), marine mammal studies have shown the amount of TTS increases with cumulative sound exposure level (SEL cum ) in an accelerating fashion: At low exposures with lower SEL cum, the amount of TTS is typically small and the growth curves have shallow slopes. At exposures with higher SEL cum, the growth curves become steeper and approach linear relationships with the noise SEL. Depending on the degree (elevation of threshold in dB), duration ( i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in Masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. We note that reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall et al., 2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost. Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin ( Tursiops truncatus ), beluga whale ( Delphinapterus leucas ), harbor porpoise, and Yangtze finless porpoise ( Neophocoena asiaeorientalis ) and five species of pinnipeds exposed to a limited number of sound sources ( i.e., mostly tones and octave-band noise) in laboratory settings (Finneran, 2015). TTS was not observed in trained spotted ( Phoca largha ) and ringed ( Pusa hispida ) seals exposed to impulsive noise at levels matching previous predictions of TTS onset (Reichmuth et al., 2016). In general, harbor seals and harbor porpoises have a lower TTS onset than other measured pinniped or cetacean species (Finneran, 2015). Additionally, the existing marine mammal TTS data come from a limited number of individuals within these species. No data are available on noise-induced hearing loss for mysticetes. For summaries of data on TTS in marine mammals or for further discussion of TTS onset thresholds, please see Southall et al. (2007), Finneran and Jenkins (2012), Finneran (2015), and table 5 in NMFS (2018). Activities for this project include impact and vibratory pile driving, vibratory pile removal, and DTH activities. There would likely be pauses in activities producing the sound during each day. Given these pauses and the fact that many marine mammals are likely moving through the project areas and not remaining for extended periods of time, the potential for threshold shift declines. Behavioral harassment —Exposure to noise from pile driving and removal and DTH also has the potential to behaviorally disturb marine mammals. Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal. If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant [ e.g., Lusseau and Bejder, 2007; Weilgart, 2007; National Research Council (NRC), 2005]. The following subsections provide examples of behavioral responses that provide an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species, or extrapolated from closely related species when no information exists, along with contextual factors. Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal. There are broad categories of potential response, which we describe in greater detail here, that include alteration of dive behavior, alteration of foraging behavior, effects to respiration, interference with or alteration of vocalization, avoidance, and flight. Pinnipeds may increase their haul out time, possibly to avoid in-water disturbance (Thorson and Reyff, 2006). Behavioral reactions can vary not only among individuals but also within an individual, depending on previous experience with a sound source, context, and numerous other factors (Ellison et al., 2012), and can vary depending on characteristics associated with the sound source ( e.g., whether it is moving or stationary, number of sources, distance from the source). In general, pinnipeds seem more tolerant of, or at least habituate more quickly to, potentially disturbing underwater sound than do cetaceans, and generally seem to be less responsive to exposure to industrial sound than most cetaceans. Alteration of Dive Behavior —Changes in dive behavior can vary widely, and may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive ( e.g., Frankel and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et al., 2013). Seals exposed to non-impulsive sources with a received sound pressure level within the range of calculated exposures (142-193 dB re 1 μPa), have been shown to change their behavior by modifying diving activity and avoidance of the sound source (Götz and Janik, 2010; Kvadsheim et al., 2010). Variations in dive behavior may reflect interruptions in biologically significant activities ( e.g., foraging) or they may be of little biological significance. The impact of an alteration to dive behavior resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response. Alteration of Feeding Behavior —Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators ( e.g., bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance ( e.g., Croll et al., 2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al., 2007; Melcón et al., 2012). In addition, behavioral state of the animal plays a role in the type and severity of a behavioral response, such as disruption to foraging ( e.g., Silve et al., 2016; Wensveen et al., 2017). An evaluation of whether foraging disruptions would be likely to incur fitness consequences considers temporal and spatial scale of the activity in the context of the available foraging habitat and, in more severe cases may necessitate consideration of information on or estimates of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal. Goldbogen et al. (2013) indicate that disruption of feeding and displacement could impact individual fitness and health. However, for this to be true, we would have to assume that an individual could not compensate for this lost feeding opportunity by either immediately feeding at another location, by feeding shortly after cessation of acoustic exposure, or by feeding at a later time. There is no indication this is the case here, particularly since prey would likely still be available in the environment in most cases following the cessation of acoustic exposure. Respiration —Respiration naturally varies with different behaviors, and variations in respiration rate as a function of acoustic exposure can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Studies with captive harbor porpoises showed increased respiration rates upon introduction of acoustic alarms (Kastelein et al., 2001; Kastelein et al., 2006a) and emissions for underwater data transmission (Kastelein et al., 2005). Various studies also have shown that species and signal characteristics are important factors in whether respiration rates are unaffected or change, again highlighting the importance in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure ( e.g., Kastelein et al., 2005; Kastelein et al., 2006; Kastelein et al., 2018; Gailey et al., 2007; Isojunno et al., 2018). Vocalization —Marine mammals vocalize for different purposes and across multiple modes, such as whistling, echolocation click production, calling, and singing. Changes in vocalization behavior in response to anthropogenic noise can occur for any of these modes and may result from a need to compete with an increase in background noise or may reflect increased vigilance or a startle response. For example, in the presence of potentially masking signals, humpback whales and killer whales ( Orcinus orca ) have been observed to increase the length of their songs (Miller et al., 2000; Fristrup et al., 2003; Foote et al., 2004), while right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks et al., 2007; Rolland et al., 2012). Killer whales off the northwestern coast of the United States have been observed to increase the duration of primary calls once a threshold in observing vessel density ( e.g., whale watching) was reached, which has been suggested as a response to increased masking noise produced by the vessels (Foote et al., 2004; NOAA, 2014). In some cases, however, animals may cease or alter sound production in response to underwater sound ( e.g., Bowles et al., 1994; Castellote et al., 2012; Cerchio et al., 2014). Studies also demonstrate that even low levels of noise received far from the noise source can induce changes in vocalization and/or behavioral responses (Blackwell et al., 2013; Blackwell et al., 2015). Avoidance —Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors, and is one of the most obvious manifestations of disturbance in marine mammals (Richardson et al., 1995). Avoidance is qualitatively different from the flight response, but also differs in the magnitude of the response ( i.e., directed movement, rate of travel, etc. ). Often avoidance is temporary, and animals return to the area once the noise has ceased. Acute avoidance responses have been observed in captive porpoises and pinnipeds exposed to a number of different sound sources (Kastelein et al., 2001; Finneran et al., 2003; Kastelein et al., 2006a; Kastelein et al., 2006b; Kastelein et al., 2015b; Kastelein et al., 2015c; Kastelein et al., 2018). Short-term avoidance of seismic surveys, low frequency emissions, and acoustic deterrents have also been noted in wild populations of odontocetes (Bowles et al., 1994; Goold, 1996; Goold and Fish, 1998; Morton and Symonds, 2002; Hiley et al., 2021) and to some extent in mysticetes (Malme et al., 1984; McCauley et al., 2000; Gailey et al., 2007). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur ( e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann et al., 2006). Forney et al. (2017) described the potential effects of noise on marine mammal populations with high site fidelity, including displacement and auditory masking. In cases of western gray whales ( Eschrichtius robustus ) and beaked whales ( Ziphius cavirostris ), anthropogenic effects in areas where they are resident or exhibit site fidelity could cause severe biological consequences, in part because displacement may adversely affect foraging rates, reproduction, or health, while an overriding instinct to remain in the area could lead to more severe acute effects. Avoidance of overlap between disturbing noise and areas and/or times of particular importance for sensitive species may be critical to avoiding population-level impacts because (particularly for animals with high site fidelity) there may be a strong motivation to remain in the area despite negative impacts. Flight Response —A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response ( e.g., directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, marine mammal strandings (Evans and England, 2001). There are limited data on flight response for marine mammals in water; however, there are examples of this response in species on land. For instance, the probability of flight responses in Dall's sheep Ovis dalli dalli (Frid, 2003), hauled out ringed seals ( Phoca hispida ) (Born et al., 1999), Pacific brant ( Branta bernicla nigricans ), and Canada geese ( B. canadensis ) increased as a helicopter or fixed-wing aircraft more directly approached groups of these animals (Ward et al., 1999). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response. Behavioral disturbance can also impact marine mammals in more subtle ways. Increased vigilance may result in costs related to diversion of focus and attention ( i.e., when a response consists of increased vigilance, it may come at the cost of decreased attention to other critical behaviors such as foraging or resting). These effects have generally not been observed in marine mammals, but studies involving fish and terrestrial animals have shown that increased vigilance may substantially reduce feeding rates and efficiency ( e.g., Beauchamp and Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In addition, chronic disturbance can cause population declines through reduction of fitness ( e.g., decline in body condition) and subsequent reduction in reproductive success, survival, or both ( e.g., Harrington and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). Many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hour cycle). Disruption of such functions resulting from reactions to stressors such as sound exposure are more likely to be significant if they last more than one diel cycle or recur on subsequent days (Southall et al., 2007). Consequently, a behavioral response lasting less than 1 day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall et al., 2007). Note that there is a difference between multi-day substantive behavioral reactions and multi-day anthropogenic activities. For example, just because an activity lasts for multiple days does not necessarily mean that individual animals are either exposed to activity-related stressors for multiple days or, further, exposed in a manner resulting in sustained multi-day substantive behavioral responses. To assess the strength of behavioral changes and responses to external sounds and SPLs associated with changes in behavior, Southall et al. (2007) developed and utilized a severity scale, which is a 10-point scale ranging from no effect (labeled 0), effects not likely to influence vital rates (low; labeled from one to three), effects that could affect vital rates (moderate; labeled from four to six), to effects that were thought likely to influence vital rates (high; labeled from seven to nine). Southall et al. (2021) updated the severity scale by integrating behavioral context ( i.e., survival, reproduction, and foraging) into severity assessment. For non-impulsive sounds ( i.e., similar to the sources used during the proposed action), data suggest that exposures of pinnipeds to sources between 90 and 140 dB re 1 μPa do not elicit strong behavioral responses; no data were available for exposures at higher received levels for Southall et al. (2007) to include in the severity scale analysis. Reactions of harbor seals were the only available data for which the responses could be ranked on the severity scale. For reactions that were recorded, the majority (17 of 18 individuals/groups) were ranked on the severity scale as a 4 (defined as moderate change in movement, brief shift in group distribution, or moderate change in vocal behavior) or lower. The remaining response was ranked as a 6 (defined as minor or moderate avoidance of the sound source). Habituation —Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok et al., 2003). Animals are most likely to habituate to sounds that are predictable and unvarying. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance (Bejder et al., 2009). The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure. As noted, behavioral state may affect the type of response. For example, animals that are resting may show greater behavioral change in response to disturbing sound levels than animals that are highly motivated to remain in an area for feeding (Richardson et al., 1995; NRC, 2003; Wartzok et al., 2003). Controlled experiments with captive marine mammals have showed pronounced behavioral reactions, including avoidance of loud sound sources (Ridgway et al., 1997; Finneran et al., 2003). Observed responses of wild marine mammals to loud impulsive sound sources (typically seismic airguns or acoustic harassment devices) have been varied but often consist of avoidance behavior or other behavioral changes suggesting discomfort (Morton and Symonds, 2002; Richardson et al., 1995; Nowacek et al., 2007). Stress responses —An animal's perception of a threat may be sufficient to trigger stress responses consisting of some combination of behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses ( e.g., Seyle, 1950; Moberg, 2000). In many cases, an animal's first and sometimes most economical (in terms of energetic costs) response is behavioral avoidance of the potential stressor. Autonomic nervous system responses to stress typically involve changes in heart rate, blood pressure, and gastrointestinal activity. These responses have a relatively short duration and may or may not have a significant long-term effect on an animal's fitness. Neuroendocrine stress responses often involve the hypothalamus-pituitary-adrenal system. Virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction, altered metabolism, reduced immune competence, and behavioral disturbance ( e.g., Moberg, 1987; Blecha, 2000). Increases in the circulation of glucocorticoids are also equated with stress (Romano et al., 2004). The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and “distress” is the cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energetic reserves sufficient to restore normal function. Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments and for both laboratory and free-ranging animals ( e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005). Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more rarely, studied in wild populations ( e.g., Romano et al., 2002a). For example, Rolland et al. (2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. These and other studies lead to a reasonable expectation that some marine mammals will experience physiological stress responses upon exposure to acoustic stressors and that it is possible that some of these would be classified as “distress.” In addition, any animal experiencing TTS would likely also experience stress responses (NRC, 2003), however distress is an unlikely result of these projects based on observations of marine mammals during previous, similar projects. Auditory Masking —Sound can disrupt behavior through masking, or interfering with, an animal's ability to detect, recognize, or discriminate between acoustic signals of interest ( e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, navigation) (Richardson et al., 1995). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural ( e.g., snapping shrimp, wind, waves, precipitation) or anthropogenic ( e.g., pile driving, shipping, sonar, seismic exploration) in origin. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest ( e.g., signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities ( e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age or TTS hearing loss), and existing ambient noise and propagation conditions. Masking of natural sounds can result when human activities produce high levels of background sound at frequencies important to marine mammals. Conversely, if the background level of underwater sound is high ( e.g., on a day with strong wind and high waves), an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked. Airborne Acoustic Effects —Pinnipeds that occur near the project site could be exposed to airborne sounds associated with pile driving and removal that have the potential to cause behavioral harassment, depending on their distance from pile driving activities. Cetaceans are not expected to be exposed to airborne sounds that would result in harassment as defined under the MMPA. Airborne noise would primarily be an issue for pinnipeds that are swimming or hauled out near the project site within the range of noise levels elevated above the acoustic criteria. We recognize that pinnipeds in the water could be exposed to airborne sound that may result in behavioral harassment when looking with their heads above water. Most likely, airborne sound would cause behavioral responses similar to those discussed above in relation to underwater sound. For instance, anthropogenic sound could cause hauled out pinnipeds to exhibit changes in their normal behavior, such as reduction in vocalizations, or cause them to temporarily abandon the area and move further from the source. However, these animals would likely previously have been `taken' because of exposure to underwater sound above the behavioral harassment thresholds, which are generally larger than those associated with airborne sound. Thus, the behavioral harassment of these animals is already accounted for in these estimates of potential take. Therefore, we do not believe that authorization of additional incidental take resulting from airborne sound for pinnipeds is warranted, and airborne sound is not discussed further. Marine Mammal Habitat Effects USAF's proposed construction activities could have localized, temporary impacts on marine mammal habitat, including prey, by increasing in-water sound pressure levels and slightly decreasing water quality. Increased noise levels may affect acoustic habitat (see Masking discussion above) and adversely affect marine mammal prey in the vicinity of the project areas (see discussion below). Elevated levels of underwater noise would ensonify the project areas where both fishes and mammals occur and could affect foraging success. Additionally, marine mammals may avoid the area during construction; however, displacement due to noise is expected to be temporary and is not expected to result in long-term effects to the individuals or populations. In-water Construction Effects on Potential Prey —Construction activities would produce continuous ( i.e., vibratory pile driving and DTH) and intermittent ( i.e., impact driving and DTH) sounds. Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species ( e.g., crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies by species, season, and location. Here, we describe studies regarding the effects of noise on known marine mammal prey. Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning ( e.g., Zelick and Mann, 1999; Fay, 2009). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay et al., 2008). The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality. Fish react to sounds that are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on the physiological state of the fish, past exposures, motivation ( e.g., feeding, spawning, migration), and other environmental factors. Hastings and Popper (2005) identified several studies that suggest fish may relocate to avoid certain areas of sound energy. Additional studies have documented effects of pile driving on fish; several are based on studies in support of large, multiyear bridge construction projects ( e.g., Scholik and Yan, 2001; Scholik and Yan, 2002; Popper and Hastings, 2009). Several studies have demonstrated that impulse sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs ( e.g., Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; Paxton et al., 2017). However, some studies have shown no or slight reaction to impulse sounds ( e.g., Pena et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman, 2009). SPLs of sufficient strength have been known to cause injury to fish and fish mortality. However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen et al. (2012a) showed that a TTS of 4 to 6 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long. Injury caused by barotrauma can range from slight to severe and can cause death, and is most likely for fish with swim bladders. Barotrauma injuries have been documented during controlled exposure to impact pile driving (Halvorsen et al., 2012b; Casper et al., 2013). The most likely impact to fishes from pile driving activities at the project area would be temporary behavioral avoidance of the area. The duration of fish avoidance of this area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. Construction activities have the potential to have adverse impacts on forage fish in the project area in the form of increased turbidity. Forage fish form a significant prey base for many marine mammal species that occur in the project area. Turbidity within the water column has the potential to reduce the level of oxygen in the water and irritate the gills of prey fish in the proposed project area. However, fish in the proposed project area would be able to move away from and avoid the areas where increase turbidity may occur. Given the limited area affected and ability of fish to move to other areas, any effects on forage fish are expected to be minor or negligible. In summary, given the short daily duration of sound associated with individual pile driving and removal events and the relatively small areas being affected, pile driving and removal activities associated with the proposed actions are not likely to have a permanent, adverse effect on any fish habitat, or populations of fish species. Any behavioral avoidance by fish of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. Thus, we conclude that impacts of the specified activities are not likely to have more than short-term adverse effects on any prey habitat or populations of prey species. Further, any impacts to marine mammal habitat are not expected to result in significant or long-term consequences for individual marine mammals, or to contribute to adverse impacts on their populations. Estimated Take of Marine Mammals This section provides an estimate of the number of incidental takes proposed for authorization through this IHA, which will inform both NMFS' consideration of “small numbers,” and the negligible impact determinations. Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of 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). Authorized takes would primarily be by Level B harassment, as use of the acoustic sources ( i.e., impact and vibratory pile driving and removal and DTH) has the potential to result in disruption of behavioral patterns for individual marine mammals. There is also some potential for auditory injury (Level A harassment) to result, primarily for mysticetes and/or high frequency species and/or phocids because predicted auditory injury zones are larger than for mid-frequency species and/or otariids. Auditory injury is unlikely to occur for other groups. The proposed mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable. As described previously, no serious injury or mortality is anticipated or proposed to be authorized for this activity. Below we describe how the proposed take numbers are estimated. For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the proposed take estimates. Acoustic Thresholds NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment). Level B Harassment —Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al., 2007; Southall et al., 2021; Ellison et al., 2012). Based on what the available science indicates and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared pressure received levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous ( e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive ( e.g., seismic airguns) or intermittent ( e.g., scientific sonar) sources. Generally speaking, Level B harassment take estimates based on these behavioral harassment thresholds are expected to include any likely takes by TTS as, in most cases, the likelihood of TTS occurs at distances from the source less than those at which behavioral harassment is likely. TTS of a sufficient degree can manifest as behavioral harassment, as reduced hearing sensitivity and the potential reduced opportunities to detect important signals (conspecific communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur. USAF's proposed activity includes the use of continuous (vibratory pile driving and removal and DTH) and impulsive (impact pile driving and DTH) sources, and therefore the RMS SPL thresholds of 120 and 160 dB re 1 μPa is/are applicable. Level A harassment —NMFS' “Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing” (Version 2.0, Technical Guidance, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). USAF's proposed activity includes the use of impulsive (impact pile driving and DTH) and non-impulsive (vibratory pile driving and removal and DTH) sources. These thresholds are provided in the table below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/ marine-mammal-acoustic-technical-guidance. Table 4—Thresholds Identifying the Onset of Permanent Threshold Shift Hearing group PTS onset acoustic thresholds * (received level) Impulsive Non-impulsive Low-Frequency (LF) Cetaceans Cell 1: L pk,flat : 219 dB; L E,LF,24h : 183 dB Cell 2: L E,LF,24h : 199 dB. Mid-Frequency (MF) Cetaceans Cell 3: L pk,flat : 230 dB; L E,MF,24h : 185 dB Cell 4: L E,MF,24h : 198 dB. High-Frequency (HF) Cetaceans Cell 5: L pk,flat : 202 dB; L E,HF,24h : 155 dB Cell 6: L E,HF,24h : 173 dB. Phocid Pinnipeds (PW) (Underwater) Cell 7: L pk,flat : 218 dB; L E,PW,24h : 185 dB Cell 8: L E,PW,24h : 201 dB. Otariid Pinnipeds (OW) (Underwater) Cell 9: L pk,flat : 232 dB; L E,OW,24h : 203 dB Cell 10: L E,OW,24h : 219 dB. * Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered. Note: Peak sound pressure ( L pk ) has a reference value of 1 μPa, and cumulative sound exposure level ( L E ) has a reference value of 1μPa 2 s. In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript “flat” is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. Ensonified Area Here, we describe operational and environmental parameters of the activity that are used in estimating the area ensonified above the acoustic thresholds, including source levels and transmission loss coefficient. The sound field in the project area is the existing background noise plus additional construction noise from the proposed project. Marine mammals are expected to be affected via sound generated by the primary components of the project ( i.e., pile driving and removal and DTH). The maximum (underwater) area ensonified above the thresholds for behavioral harassment referenced above is 1286 km 2 (496 mi 2 ), and the calculated distance to the farthest behavioral harassment isopleth is approximately 39,811 m (24,737.4 mi). The project includes vibratory pile installation and removal, impact pile driving, and DTH. Source levels for these activities are based on reviews of measurements of the same or similar types and dimensions of piles available in the literature. Source levels for each pile size and activity are presented in table 5. Source levels for vibratory installation and removal of piles of the same diameter are assumed to be the same. NMFS recommends treating DTH systems as both impulsive and continuous, non-impulsive sound source types simultaneously. Thus, impulsive thresholds are used to evaluate Level A harassment, and continuous thresholds are used to evaluate Level B harassment. With regards to DTH mono-hammers, NMFS recommends proxy levels for Level A harassment based on available data regarding DTH systems of similar sized piles and holes (Denes et al., 2019; Reyff and Heyvaert, 2019; Reyff, 2020; Heyvaert and Reyff, 2021) (table 1 includes number of piles and duration; table 5 includes sound pressure and sound exposure levels for each pile type). Table 5—Estimates of Mean Underwater Sound Levels Generated During Vibratory and Impact Pile Installation, DTH, and Vibratory Pile Removal Continuous sound sources SSL at 10 m dB rms Literature source Vibratory Hammer 42-inch steel piles 168.2 Port of Anchorage Test Pile Program (Table 16 in Austin et al., 2016). 30-inch steel piles 166 * NMFS Analysis (C. Hotchkin, April 24, 2023). DTH 42-inch steel piles 174 Reyff & Heyvaert, 2019; Reyff, 2020. 30-inch steel piles 174 Reyff & Heyvaert, 2019; Reyff, 2020. Impulsive sound sources dB rms dB SEL dB peak Literature source Impact Hammer 42-inch steel piles 192 179 213 Caltrans, 2020. 30-inch steel piles 191 177 212 Caltrans, 2020. DTH 42-inch steel piles N/A 164 194 Reyff & Heyvaert, 2019; Reyff, 2020; Denes et al., 2019. 30-inch steel piles N/A 164 194 Reyff & Heyvaert, 2019; Reyff, 2020; Denes et al., 2019. Note: dB peak = peak sound level; DTH = down-the-hole drilling; rms = root mean square; SEL = sound exposure level. * NMFS generated this source level by completing a completed a comprehensive review of source levels relevant to Southeast Alaska; NMFS compiled all available data from Puget Sound and Southeast Alaska and adjusted the data to standardize distance from the measured pile to 10 m. NMFS then calculated average source levels for each project and for each pile type. NMFS weighted impact pile driving project averages by the number of strikes per pile following the methodology in Navy (2015). Transmission loss ( TL ) is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, and bottom composition and topography. The general formula for underwater TL is: TL = B * Log10 ( R 1/ R 2), where TL = transmission loss in dB B = transmission loss coefficient R 1 = the distance of the modeled SPL from the driven pile, and R 2 = the distance from the driven pile of the initial measurement Absent site-specific acoustical monitoring with differing measured transmission loss, a practical spreading value of 15 is used as the transmission loss coefficient in the above formula. Site-specific transmission loss data for the Shemya Island are not available; therefore, the default coefficient of 15 is used to determine the distances to the Level A harassment and Level B harassment thresholds. The ensonified area associated with Level A harassment is more technically challenging to predict due to the need to account for a duration component. Therefore, NMFS developed an optional User Spreadsheet tool to accompany the Technical Guidance that can be used to relatively simply predict an isopleth distance for use in conjunction with marine mammal density or occurrence to help predict potential takes. We note that because of some of the assumptions included in the methods underlying this optional tool, we anticipate that the resulting isopleth estimates are typically going to be overestimates of some degree, which may result in an overestimate of potential take by Level A harassment. However, this optional tool offers the best way to estimate isopleth distances when more sophisticated modeling methods are not available or practical. For stationary sources such as pile driving, the optional User Spreadsheet tool predicts the distance at which, if a marine mammal remained at that distance for the duration of the activity, it would be expected to incur PTS. Inputs used in the optional User Spreadsheet tool, and the resulting estimated isopleths, are reported below. Table 6—User Spreadsheet Inputs Vibratory 30-inch steel piles Installation or removal 42-inch steel piles Installation Impact 30-inch steel piles Installation 42-inch steel piles Installation DTH 30-inch steel piles Installation 42-inch steel piles Installation Spreadsheet Tab Used A.1) Vibratory Pile Driving A.1) Vibratory Pile Driving E.1) Impact Pile Driving E.1) Impact Pile Driving E.2) DTH Pile Driving E.2) DTH Pile Driving Source Level (SPL) 166 RMS 168.2 RMS 177 SEL 179 SEL 174 RMS, 164 SEL 174 RMS, 164 SEL Transmission Loss Coefficient 15 15 15 15 15 15 Weighting Factor Adjustment (kHz) 2.5 2.5 2 2 2 2 Activity Duration per day (minutes) 60 120 120 180 150 180 Strike Rate per second 10 10 Number of strikes per pile 900 1,800 Number of piles per day 4 4 4 4 3 3 Distance of sound pressure level measurement 10 10 10 10 10 10 Table 7—Level A Harassment and Level B Harassment Isopleths From Vibratory and Impact Pile Driving and DTH Pile type Level A harassment isopleths (m) LF MF HF PW OW Level B harassment isopleth (m) Vibratory 42-inch steel pipe piles 32.7 2.9 48.4 19.9 1.4 16,343 30-inch Steel pipe piles 14.7 1.3 21.8 8.9 0.6 11,659 DTH 42-inch Steel pipe piles 2,549.4 90.7 3,036.7 1,364.3 99.3 39,811 30-inch Steel pipe piles 2,257.6 80.3 2,689.2 1,208.2 88.0 39,811 Impact 42-inch steel pipe piles 2,015.1 71.7 2,400.3 1,078.4 78.5 1,359 30-inch Steel pipe piles 933.8 33.2 1,112.3 499.7 36.4 1,166 Marine Mammal Occurrence and Take Estimation In this section we provide information about the occurrence of marine mammals, including density or other relevant information which will inform the take calculations. We describe how the information provided is synthesized to produce a quantitative estimate of the take that is reasonably likely to occur and proposed for authorization. As described above, for some species (humpback whale, killer whale, Steller sea lion and harbor seal) observations within the project area from the prior monitoring were available to directly inform the take estimates, while for other species (fin whale, minke whale, sperm whale, Baird's beaked whale, Stejneger's beaked whale, Dall's porpoise, harbor porpoise and northern fur seal) they were not. Prior surveys include Protected Species Observer (PSO) monitoring completed at the project site on 60 days between June and August 2021 during the emergency fuel pier repair, island-wide faunal surveys completed by the USACE Engineer Research Development Center (ERDC) across 33 days between 2016 and 2019 (primarily in the spring and fall), and island-wide marine mammal surveys completed by the USACE Civil Works Environmental Resource Section on 26 days between May and October 2021. From all three surveys, data that were collected within the project area are primarily the basis for the take estimates because those data best represents what might be encountered there. Average group sizes used to inform Level B take estimates (which also underlie the estimates for Level A harassment) for all species with prior observations in the project area are primarily based on those data. Alternate methods utilizing average group sizes informed primarily by Alaska's Wildlife Notebook Series are used for species without prior observations. Also of note, while the results are not significantly different, in some cases we recommended modified methods for estimating take from those presented by the applicant and have described them below. A summary of proposed take, including as a percentage of population for each of the species, is shown in table 8. Fin Whale No fin whale were reported during monitoring conducted for the EAS fuel pier emergency repair completed in 2021, nor during other surveys completed from Shemya Island (see application). Accordingly, average group size, estimated group size based on information shared in the Alaska Wildlife Notebook Series (Clark 2008a), is used as the basis for the take estimates. USAF requested 17 takes of fin whales by Level B harassment, using a calculation based on of 0.002 groups of eight fin whales per hour of construction activity. NMFS concurs with USAF's predicted group size of fin whale (8 individuals), but since there are no observations of this species from Shemya Island, NMFS finds it more appropriate to estimate take by Level B harassment using a less granular occurrence estimate (monthly) rather than USAF's hourly occurrence estimate. Specifically, 1 group of 8 fin whales is predicted every 2 construction months, based on the applicant's prediction that this species would be rare in the project area. The duration of the construction is 160 days (2.65 × the basic 60 day period) and 8 * 2.65 = 21 takes by Level B harassment). Although the shutdown zone is larger than the Level A harassment zone for low frequency cetaceans, USAF indicates that at ≥2,000 m, it becomes more challenging to reliably detect low frequency cetaceans in some environmental conditions, and therefore it is possible that a fin whale could enter the Level A harassment zone during DTH activities and stay long enough to incur PTS before USAF detects the animal and shuts down. As such, USAF requested and NMFS proposed to authorize a small amount of take by Level A harassment of fin whales. NMFS calculated takes by Level A harassment by first determining the proportion of the area of largest Level A harassment zone (42-inch DTH, 2,549 m) that occurs beyond the readily observable 2,000 m from the pile driving location ( i.e., 7.5 km 2 −5 km 2 /7.5 km 2 = 0.33). This ratio was multiplied by the estimated fin whale exposures, which is generally one group of eight fin whale that would occur every 2 construction months (or 60 days, adjusted by 1.2 to account for the 70 days that DTH activities are planned). Multiplying these factors (8 * 1.2 * 0.33) results in = 3 takes by Level A harassment). Any individuals exposed to the higher levels associated with the potential for PTS closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as both a Level A harassment take and a Level B harassment take, and therefore takes by Level B harassment calculated as described above are further modified to deduct the proposed amount of take by Level A harassment ( i.e., 21−3 = 18). Therefore, NMFS proposes to authorize 3 takes by Level A harassment and 18 takes by Level B harassment for fin whales, for a total of 21 takes. Humpback Whale Across 119 days of marine mammal surveys completed from Shemya Island between 2016 and 2021, seven humpback whales were observed in the project area. The average group size for humpback whales detected in the project area was 2 humpback whales per group detected. For estimating take by Level B harassment where monitoring data confirmed the presence of the marine mammal species, NMFS concurred with USAF's proposed approach. USAF requested take by Level B harassment by predicting that 0.07 groups of humpback whales would be sighted every hour, which was based on the applicant predicting this species would commonly occur within the project area. This was then multiplied by the average group size for humpback whales (2 individuals), to achieve an hourly humpback rate. Finally, these numbers are multiplied by the hours of construction activity. (0.07 * 2 * 1,101 = 154 takes by Level B harassment). Although the shutdown zone is larger than the Level A harassment zone for low frequency cetaceans, USAF indicates that at ≥2,000 m, it becomes more challenging to reliably detect low frequency cetaceans in some environmental conditions, and therefore it is possible that humpback whales could enter the Level A harassment zone during DTH activities and stay long enough to incur PTS before USAF detects the animal and shuts down. As such, USAF requested and NMFS proposed to authorize a small amount of take by Level A harassment of humpback whales. NMFS calculated takes by Level A harassment by determining the proportion of the area of largest Level A harassment zone (42-inch DTH, 2,549 m) that occurs beyond 2,000 m from the pile driving location ( i.e., 7.5 km 2 −5 km 2 /7.5 km 2 = 0.33) and multiplying this ratio by the estimated humpback whale exposures (0.07 groups of 2 humpback whale) that would occur every construction hour that DTH activities are planned (624 hours) (0.07 * 2 * 624 * 0.33 = 29 takes by Level A harassment). For the reasons described above, takes by Level B harassment were modified to deduct the proposed amount of take by Level A harassment ( i.e., 154−29 = 125). Therefore, NMFS proposes to authorize 29 takes by Level A harassment and 125 takes by Level B harassment for humpback whales, for a total of 154 takes. Minke Whale No minke whales were reported during monitoring conducted for the EAS fuel pier emergency repair completed in 2021, nor during other surveys completed from Shemya Island ( e.g., see application). Accordingly, average group size, estimated based on group size information shared in the Alaska Wildlife Notebook Series (Clark 2008a), is used as the basis for the take estimates (Guerrero 2008b). USAF requested 7 takes of minke whales by Level B harassment, using a calculation of of 0.002 groups of three minke whales per hour of construction activity. NMFS concurs with USAF's predicted group size of minke whale (three individuals), but since there are no observations of this species from Shemya Island, NMFS finds it more appropriate to estimate take by Level B harassment using a less granular occurrence estimate (monthly) rather than USAF's hourly occurrence estimate. Specifically, one group of three minke whales is predicted every 2 construction months, based on the applicant's prediction that this species would be rare in the project area. The duration of construction is 160 days (2.65 * the basic 60 day period, which corresponds to two months) and 3 * 2.65 = 8 takes by Level B harassment. Although the shutdown zone is larger than the Level A harassment zone for low frequency cetaceans, USAF indicates that at ≥2,000 m, it becomes more challenging to reliably detect low frequency cetaceans in some environmental conditions, and therefore it is possible that a minke whale could enter the Level A harassment zone during DTH activities and stay long enough to incur PTS before USAF detects the animal and shuts down. As such, USAF requested and NMFS proposed to authorize a small amount of take by Level A harassment of minke whales. NMFS calculated takes by Level A harassment by determining the proportion of the area of largest Level A harassment zone (42-inch DTH, 2,549 m) that occurs beyond the readily observable 2,000 m from the pile driving location ( i.e., 7.5 km 2 −5 km 2 /7.5 km 2 = 0.33). This ratio was multiplied by the estimated minke whale exposures, which is generally one group of three minke whales every 2 construction months (or 60 days), adjusted by 1.2 to account for the 70 days that DTH activities are planned. Multiplying these factors 1.2 * 0.33 results in 1 take by Level A harassment. Since the predicted average group size of minke whale is three, NMFS proposes to authorize three takes by Level A harassment of minke whale. For reasons described above, takes by Level B harassment were modified to deduct the proposed amount of take by Level A harassment ( i.e., 8−3 = 5). Therefore, NMFS proposes to authorize three takes by Level A harassment and five takes by Level B harassment for minke whales, for a total of eight takes. Sperm Whale Across 119 monitoring days between 2016 and 2021, four sperm whales were observed on a single day from Shemya Island, though outside of the project area (see application). USAF requested 27 takes of sperm whale by Level B harassment, using a calculation based on of 0.006 groups of four sperm whales per hour of construction activity. NMFS concurs with USAF's predicted group size of sperm whale (4 individuals, which corresponds to the number of sperm whales detected on a single day during Shemya Island marine mammal surveys), but since there are few observations of this species from Shemya Island, NMFS finds it more appropriate to estimate take by Level B harassment using a less granular occurrence estimate (monthly) rather than USAF's hourly occurrence estimate. Specifically, two groups of four sperm whales is predicted every 1 construction month based on sperm whales being one of the most frequently sighted marine mammals in the high latitude regions of the North Pacific, including the Bering Sea and the Aleutian Islands. The duration of the construction is 5 months and 2 * 4 * 5 = 40 takes by Level B harassment. Due to the small Level A harassment zones (table 9), which do not reach deep water where sperm whales are expected to be encountered, coupled with the implementation of shutdown zones, which will be larger than Level A harassment zones for mid-frequency cetaceans (described in the Proposed Mitigation section), NMFS concurs with USAF's assessment that take by Level A harassment is not anticipated for sperm whale. Therefore, NMFS proposed to authorize all 40 estimated exposures as takes by Level B harassment. Takes by Level A harassment for sperm whales are not requested nor are they proposed for authorization. Baird's Beaked Whale Baird's beaked whales are usually found in tight social groups (schools or pods) averaging between 5 and 20 individuals, but they have occasionally been observed in larger groups of up to 50 animals. Across 119 days of marine mammal surveys completed from Shemya Island between 2016 and 2021, no observations of Baird's beaked whale were recorded (see application). Accordingly, average group size, estimated based on group size information shared in the Alaska Wildlife Notebook Series (Guerrero 2008a), is used as the basis for take estimates. USAF requested 11 takes by Level B harassment, using a calculation based on 0.001 groups of ten Baird's beaked whales per hour of construction activity. NMFS concurs with USAF's predicted group size of Baird's beaked whale (10 individuals), but since there are no observations of this species from Shemya Island, NMFS finds it more appropriate to estimate take by Level B harassment using a less granular occurrence estimate (monthly) rather than USAF's hourly occurrence estimate. Specifically, 1 group of 10 Baird's beaked whales is predicted across the project, which is based on this species being shy and preferring deep waters and as such the applicant predicted they would be very rare in the project area. Therefore, NMFS proposes to authorize 10 takes of Baird's beaked whale by Level B harassment. Due to the small Level A harassment zones (table 9), which do not reach deep water where Baird's beaked whales are expected to be encountered, coupled with the implementation of shutdown zones, which will be larger than Level A harassment zones for mid-frequency cetaceans (described in the Proposed Mitigation section), NMFS concurs with USAF's assessment that take by Level A harassment is not anticipated for Baird's beaked whale. Therefore, NMFS proposed to authorize all 10 estimated exposures as takes by Level B harassment. Takes by Level A harassment for Baird's beaked whales are not requested nor are they proposed for authorization. Stejneger's Beaked Whale Across 119 days of marine mammal surveys completed from Shemya Island between 2016 and 2021, no observations of Stejneger's beaked whale were recorded (see application). Accordingly, average group size, estimated based on group size information shared in the Alaska Wildlife Notebook Series (Guerrero 2008a), is used as the basis for take estimates. USAF requested 9 takes of Stejneger's beaked whale by Level B harassment, using a calculation based on of 0.001 groups of eight Stejneger's beaked whales per hour of construction activity. NMFS concurs with USAF's predicted group size of Stejneger's beaked whale (eight individuals), but since there are no observations of this species from Shemya Island, NMFS finds it more appropriate to estimate take by Level B harassment using a less granular occurrence estimate (monthly) rather than USAF's hourly [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%3A2023-23970. Public record. Not legal advice.