EIBN Systems and Technologies Corporation A Subsidiary of Bolt Beranek and Newman Inc. Report No. 6945 (3CS Study MMS 89-0006 Analysis and Ranking of the Acoustic Disturbance Potential of Petroleum Industry Activities and Other Sources of Noise in the Environment of Marine Mammals in Alaska FINAL REPORT Contract No. 14-12-0001-30365 Prepared for: U.S. Department of the Interior Minerals Management Service Alaska OCS Office 'flTE2 i.j:iI 2EAIC IEEVh'J. E IWEEBTO cn .1 Report No. 6945 OCS Study MMS 89-0006 . ANALYSIS AND RANKING OF THE ACOUSTIC DISTURBANCE POTENTIAL OF PETROLEUM INDUSTRY ACTIVITIES AND OTHER SOURCES OF NOISE IN THE ENVIRONMENT OF MARINE MAMMALS IN ALASKA C.I. Malme, P.R. Miles - BBN G.W. Miller, W.J. Richardson, D.G. Roseneau, D.H. Thomson - LGL C.I?. Greene, Jr. - Greeneridge Sciences August 1989 Contract No. 14-12-0001-30365 Prepared by: BBN Systems and Technologies Corporation 10 Moulton Street Cambridge, MA 02238 Prepared for: Minerals Management Service U.S. Department of the Interior 949 East 36th Avenue, Room 603 Anchorage, Alaska 99508 Report No. 6945 BBN Systems and Technologies Corporation This report has been reviewed by the Minerals Management Service (MMS) and approved for publication. Approval does not signi~ that the contents necessarily reflect the views and policies of the MMS~ nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Report No. 6945 BBN Systems and Technologies Corporation ACKNOWLEDGEMENTS We thank Daniel Basta. Chief of NOAA’s Strategic Assessment Branch, for making material from the pre-publication edition OF the Bering, Chukchi”and Beauf~rt Seas Strategic Assessment: Data Atlas available to us. Stephen AmstruD.. Alaska Fish and Wildlife Research Center, kindly provided information about maternity denning of polar bears on ice in Alaska waters. David Friis and Laurie Jarvela, NOAA National Ocean Service, Anchorage were very helpful in providing OCSEAP reference documents. The MMS environmental impact and socioeconomic study documents provided by Stephen Treaty and Kevin Banks, MMS OCS Office, Anchorage , were very useful in our analysis. The information on fishing vessel activities in Alaskan waters provided by Bill Wilson, North Pacific Fishery Management Council, Anchorage; and Joe Terry, NOAA Northwest and Alaska Fisheries Center, Seattle, was greatly appreciated. The double duty of co-authors, W. John Richardson and Paul Miles in editing the lengthy draft of this report is very much appreciated. We thank Judy Derle for her expeditious and accurate processing of the text presented in the following pages. i Report No. 6945 BBN Systems and Technologies Corporation ABSTRACT A better understanding of the numbers, locations, and acoustic intensi- ties of the wide variety of man-made and natural noise sources in the Alaskan marine environment is needed in order to determine the normal levels of natural ambient noise and the “normal” levels of human noise to which marine mammals are exposed in their usual habitats. The purpose of this study is to provide an up-to-date comprehensive synthesis of available information that compares the relative magnitudes and effects on marine mammals of noise from oil and gas industry activities with noise from other sources in Alaska OCS and coastal waters. The study procedure incorporates the receiver, source and path concepts generally used in acoustic analysis. The receiver characteriza- tion includes a review of marine mammal distribution in Alaska and a map of the distribution of each major species. (Scientific names of marine mammal species discussed in this report are presented in Appendix F.) Information on sound production, hearing sensitivity (when known) , and observed responses to noise sources is also included. The analysis of noise sources found in the Alaskan marine environment considers natural, industrial, transportation, and cultural sources. Acoustic transmission loss characteristics obtained from measurements and model predictions are used to estimate the effective ranges of the noise sources using available source level information. Information on species distribution was combined with information on source distribution, source level, and transmission loss to determine the most significant sources in terms of their acoustic range and the numbers of mammals potentially affected. This was done by developing a Standardized Noise Contribution Model combined with a Standardized Exposure Rating Model for various specific species. This procedure provides an indication of which source - species com- binations may have the highest potential for acoustic interaction in a given area. In terms of their potential effects on marine mammals, the loudest sound sources in the Alaskan marine environment are seismic arrays (both air gun and vibroseis), icebreakers large ships, and dredges. Sound levels produced by smaller vessels and boats become significant when several of these sources are operating concurrently in a small area. Earthquake events produce high underwater sound levels sporadically in active seismic areas such as the Aleutian arc. Baleen whales are considered to have hearing sensitivity char- acteristics which include the frequency range of most of the man-made sources described above. As a result the exposure model showed that the gray, bow- head, fin, and humpback whales which frequent Alaskan waters are the species with the highest probability of acoustic interaction with most of the sound sources studied. The model predicted that killer whales, harbor porpoise, DaH’s porpoise, harbor seals, and fur seals would be influenced primarily by the loudest sources since their hearing sensitivity does not extend to the low frequency range estimated for baleen whales. The other species studied, including walrus, white whale, and Steller sea lion, were all predicted to have medium to low probability of acoustic influence from the sources con- sidered. This is primarily a result of the fact that their optimal hearing sensitivity is at frequencies above the dominant output frequencies of most man-made sources. ii Report No. 6945 BBN Systems and Technologies Corporation EXECUTIVE SUMMARY Background A number of studies have been made of the responses of marine mammals to various types of noise produced by the oil and gas industry. In these studies the existing ambient noise levels in the study areas have necessarily been used as a control stimulus. The noise exposure history of the subject mammals has not been known. The Alaskan marine environment contains a diverse variety of noise sources including marine biota, natural seismicity, vessel noise, and sources associated with the oil and gas industry. A better understanding of the numbers, locations, and intensities of these noise sources is needed in order to determine the normal levels of natural ambient noise and the “normal” levels of background noise, including extraneous human noise, to which marine mammals are exposed in their usual habitats. To that end, the purpose of this study is to provide an up-to-date comprehensive synthesis of available informa- tion about the relative magnitudes and anticipated effects on marine mammals of noise from oil and gas industry activities in relation to magnitudes and effects of noise from other sources in Alaska OCS and coastal waters. Objectives 1. Identify the major sound sources in the Alaskan OCS and coastal marine environment and quantify their numbers, distributions (temporal and spatial), and acoustic characteristics. 2. Summarize the geographic zones of the potential acoustic influence on important marine mammal habitats and, for each noise source, postulate the magnitude of overall interactions with Alaskan marine mammals. 3. Quantify and rank the relative seasonal magnitude of sound “loading” of the Alaskan marine environment produced by each major sound source. 4. Depict the major sound sources and their geographic zone of influence as graphic overlays on displays of regional and temporal marine mammal distribution. Study Description The procedure followed to meet these requirements incorporates the source, path, and receiver concepts generally used in acoustic analysis. The receiver characterization includes a review of marine mammal distributions in Alaska and a map of the distribution of each major species. A total of 30 species known to occur in Alaska were considered in the study. Alaska is a significant part of the range of 18 of these species. Alaska is a relatively unimportant part of the range of eight of the species, and four of the species are rare or accidental in Alaskan waters. The report also reviews information on sound production by each species, hearing sensitivity (when known), and observed responses to noise sources. iii Report No. 6945 BBN Systems and Technologies Corporation The analysis of noise sources found in the Alaskan marine environment includes natural, industrial, transportation, and cultural sources. Information on their output spectra is presented in graphs and tables of 1/3 octave source level (dB re 1 pPa at 1 m). When available, information on the temporal characteristics of the sources is also included. Acoustic transmission loss characteristics are obtained from measurements and model predictions. These characteristics, along with the above source level data, are used to estimate the effective acoustic ranges of sound sources. Both airborne and underwater transmission loss characteristics are required. However, empirical information on underwater