Loading...
HomeMy WebLinkAboutUnimak Pass Vessel Analysis Tech Rep No108 1984 Technical Report Number 108 Social and Economic Studies Program Sponsor: Minerals Management Service Alaska Outer Continental Shelf Region Unimak Pass Vessel Analysis TECHNICAL REPORT NO. 108 CONTRACT NO. AA851-CT2-34 UNIMAK PASS VESSEL ANALYSIS Prepared for: MINERALS MANAGEMENT SERVICE ALASKA OUTER CONTINENTAL SHELF REGION LEASING AND ENVIRONMENT OFFICE SOCIAL AND ECONOMIC STUDIES UNIT September 1984 NOTICE This document is disseminated under the sponsorship of the Minerals Management Service, U.S. Department of the Interior, Alaska Outer Continental Shelf Region, in the interest of information exchange. The U.S. Government assumes no liability for its contents or use thereof. UNIMAK PASS VESSEL ANALYSIS Prepared by: Louis Berger and Associates, Inc. This report was prepared under the guidance of Karen Gibson, Minerals Mangement Service. Principal contributors to this re- port include Peter Cook and Jim Pederson, Louis Berger and Asso- ciates and Gary Hennigh, Gary Hennigh Associates. ABSTRACT This report identifies present and future marine traffic and related characteristics of vessels using Unimak Pass. This pass is the main portal in the Aleutian Islands between the Bering Sea and the Pacific Ocean. A description of the location and weather features of Unimak Pass is provided. Also, a discussion of historical collisions, navigational issues, anda recent U.S. Coast Guard study in regards to the pass are presented. Present and future vessel traffic estimates through the year 2000 are developed for four categories: OCS activities, fishing, natural resources, and commercial shipping. Increases in OCS traffic are expected between 1985 and 2000. Between 1995 and 2000 major traffic increases in natural resource shipping activi- ties are expected. Fishing vessels are expected to remain rela- tively stable throughout the period. Total annual vessel traffic for the year 2000 is estimated to increase approximately 100 percent over the base year from approximately 2290 trips to 4600 trips in 2000. The primary focus of the report is to assess the impact, i.e. increase in collisions, of additional vessel traffic using Unimak Pass as a result of future OCS activities in northern and western Alaska. A probability model for estimating future colli- sions is developed. The probability of collision incidents in the year 2000 without OCS traffic is one collision every fifty- seven years and with OCS traffic is one collision every thirty- three years. The OCS traffic almost doubles the likelihood of a collision in the pass by the year 2000. However, relative to the possibility of a collision without OCS traffic, this increase is insignificant. TABLE OF CONTENTS 1.0 INTRODUCTION 1.1 Purpose 1.2 Study Scope and Organization 2.0 UNIMAK PASS 2.1 Location and Weather Characteristics 2.2 Issues 2.2.1 Collisions in Unimak Pass 2.2.2 Coast Guard Activities 3.0 UNIMAK PASS VESSEL TRAFFIC 3.1 Current Traffic Estimates 3.1.1 OCS Traffic 3.1.2 Fishing Vessels 3.1.3 Natural Resource Shipping 3.1.4 Commercial Shipping 3.2 Future Traffic Projections 3.2.1 OCS Traffic 3.2.2 Fishing Vessels 35233 Natural Resource Shipping 3.2.3.1 Coal 3.2.3.2 Other Minerals 3.2.3.3 Timber 3.2.4 Commercial Shipping 4.0 PROBABILITY OF FUTURE COLLISIONS 4.1 Factors Affecting Collisions 4.2 Collisions Models 4.3 Collisions in Unimak Pass 4.4 Relation of Model Results to Recent Experience 4.5 Conclusion Appendix A Collision Probability Calculations BIBLIOGRAPHY Page 12 12 14 14 16 20 20 22 24 25 27 27 28 31 35 36 37 38 LIST OF TABLES Unimak Pass Vessel Traffic Base Year Domestic Fleet Movements Through Unimak Pass International Fishing Fleet Movements Through Unimak Pass 1982 Domestic Waterborne Commerce Total Unimak Pass Vessel Traffic Projections Western Alaska OCS Traffic Projections Using Unimak Pass Sealift Traffic Projection for 1985-2000 Using Unimak Pass Total OCS Traffic Projections Using Unimak Pass Natural Resource Shipping Movements Through Unimak Pass Future Domestic Commercial Shipping Movements Through Unimak Pass Summary of Vessel Traffic Forecasts for Unimak Pass Forecast of Collisions in Unimak Pass ii 11 13 15 17 18 19 23 26 32 34 — mm ex Figures 2.1 2.2 LIST OF FIGURES Regional Location Map of Unimak Pass Sub-regional Location Map of Unimak Pass iii _ 1.0 INTRODUCTION 1.1 Purpose The purpose of this report is to identify and evaluate the levels of present and future vessel traffic using Unimak Pass. The pass is the principal portal through the Aleutian Islands that provides a major travel way for vessels moving between the Bering Sea and Pacific Ocean. The pass forms part of the great circle route that links the orient with the west coast of North America and is subject to passage by numerous cargo and fishing vessels. Anticipated economic growth throughout Alaska and in international trade with Asia is expected to increase traffic through the pass. A significant portion of this traffic increase may result from OCS oil and gas exploration and development activities in western and northern Alaska. There has been some recent speculation that increases in vessel traffic using Unimak Pass may cause an increase in colli- sions and other related safety issues in this area. Therefore, a primary objective of this study is to determine if an increase in Unimak Pass traffic will result in a higher level of collision incidents in the pass, particularly in consideration of future OCS activities in western and northern Alaska. This study is one of several transportation-related studies sponsored by the Minerals Management Service, Alaska OCS Region, Social and Economic Studies Unit. The overall objective of this program is to evaluate the broad range of possible socioeconomic effects of OCS activities throughout Alaska. This information can be used in the preparation of various decision making docu- ments required by the Minerals Management Service Office for determining the effects of Federal OCS activities on Alaska's transportation systems. 1.2 Study Scope and Organization This report contains three major chapters. Chapter 2 des- cribes the location and weather characteristics, recent colli- sions and issues regarding Unimak Pass. It also discusses recent Coast Guard activities in relation to Unimak Pass. Chapter 3 provides estimates of current and future Unimak Pass’ vessel traffic through the year 2000. The vessel traffic data are presented in four major components: fishing vessels, natural resources vessels, OCS vessels, and commercial shipping vessels. Chapter 4 focuses on the probability of future vessel collisions in Unimak Pass. It discusses the factors affecting collisions, collision models, and evaluates the statistical probability of future collisions in the pass with and without OCS activity. 2.0 UNIMAK PASS 2.1 Location and Weather Characteristics Unimak Pass is the first major ship passage in the Aleutian Islands southwest of the Alaska Peninsula that connects’ the Bering Sea with the Pacific Ocean (see Figure 2.1). The pass is part of the Fox Islands (subgroup of the Aleutian Islands) and at its narrowest distance is approximately twelve miles wide between the southwest end of Unimak Island and Ugamak Island (see Fig- ure 2.2). Unimak Pass is the widest of the three Fox Islands passes and the one most generally used. The only navigational aids are channel marker lights located at various intervals throughout the pass (U.S. Department of Commerce, 1983). In addition to being the major gateway into the Bering Sea, Unimak Pass is also used by many vessels on the great circle route to effect a shorter and better weather route across_ the North Pacific Ocean. This route connects the United States west coast ports with Asian ports, primarily in Japan, Korea, and Taiwan. The route generally follows the outer edge of the Pacific Ocean in linking the continents of North America and Asia together. The route west via the Bering Sea avoids the prevail- ing head winds and heavy seas that are frequently encountered south of the Aleutian Islands. The Aleutian Islands are known for their notoriously bad weather, particularly rain, fog, and strong winds. Poor visibil- ity is often a problem that marine and aviation operators in this area must contend with. Visibility around Unimak Pass is gener- ally best in the winter. ° In summer when warm air from the Pacif- ic Ocean moves over relatively cooler waters near the Aleutians, extensive fog formation takes place. Often the sun's heat’ has little effect in dissipating this fog, and it takes a change in air flow to clear the region. This advection or sea fog forms most often from June through September. At its peak in July and August, it can reduce visibilities to below two miles on ten to twenty days per month throughout the chain. It is most likely to affect the southern side of the Aleutian Islands, although quite often it blankets the entire region. In winter, land fog is more local and can be expected along with snow and rain, to drop visibilities to less than two miles on one to four days per month. 2.2 Issues As part of this study, we were required to identify existing and future navigational issues and problems relating to Unimak Pass. A literature search was initiated which proved to be of FIGURE 2.1 REGIONAL LOCATION MAP OF UNIMAK PASS SOURCE: Bugosiul Island * 4 The Aleutians, Volume 7, Number 3, 1980, Alaska Geogra- phic. Aleutian Islands 2 LP D izembek National /"s. fs Wildlite Range, 2s. Nai See Amak Island & 7), Aleutian Islands National Wiidhte Retuge S King Covds= “Pavloft Shumagin Islands 7 S&S BERING SEA Wee als 3&3, Islands ‘Cherni Is. Loman Sos Sanak Oni, Islands ‘s ‘ak Pass pd PACIFIC OCEAN “el Ft d Islan FIGURE 2.2 SUB-REGIONAL LOCATION MAP OF UNIMAK PASS Wzemoet Hatonal °° Wildnte Range 2° ( * Alaska Peninsula Unimak Island we Aleutian Islands National Wildiite Refuge Roundtop F si Moulin?) Unimak Island ‘3? [ ai Peaks V CX Volcano , isanotski “a ie si eme | S)) i yx A. Fox Islands 562081 BGs worse: SL Unimak Bight I ois KU 4 6.568°/7 a Yesidan! Peak TTS : oth Ugamas Is Aaslak Is ere Tangunak Is * Abutun fay Island go" Thyalda Adukt is | pean “aiutan wit a ae “Island Excetune ts] 4275's {fo hank een Kose nent Is Akutan i YP Besos Ao ch Wo Nursery Is Romansenaur's| %, island Unwiga is Nee Pass Krenitzin *tuslands Aleuban Islands 7 7 7 Raby ¢Uialna is. Nanonal Yuidute Retuge We ly Buy edanka ¢ on sce wh Unalaska Vad SOURCE: The Aleutians, Volume 7, Number 3, 1980, Alaska Geogra- { phic. limited value since virtually nothing has been written about traffic levels or navigation issues in Unimak Pass. Discussions were held with various shipping and fishing vessel operators who frequently use the pass. Also, phone interviews were conducted with the U.S. Coast Guard and the Southwest Alaska Pilots Asso- ciation regarding the pass. Only one major problem was consistently perceived by the marine operators and that was a problem of weather. However, for the collisions recently reported, inclement weather does not appear to be a factor. Furthermore, weather is a typical consid- eration which all marine navigation activities must monitor. One major shipping firm (name withheld by request) stated that it had a couple minor incidents with non-English speaking fishing vessels in the pass. None of the interviewed shippers said that the current traffic levels were a problem, and many stated that there could be a major increase in traffic and they would not even be aware of it. Many of the vessel operators did not appear to be aware or concerned that significant increases in Unimak Pass vessel traffic may result from future OCS activities in western and northern Alaska. None of the shippers saw a need for a traffic separation scheme. However, at the same time no one stated any opposition to such a scheme if it was deemed necessary. 2.2.1 Collisions in Unimak Pass Limited information on collisions in Unimak Pass is avail- able. Based on the existing literature, a review of major Alas- kan newspaper files from the mid-1970s to’the present time, and personal interviews, it appears that no collisions have occurred in which human lives were lost. The Coast Guard has also stated that Unimak Pass has "no strong history of collisions" (Anchorage Times, March 13, 1984). However, it is not known how well historical accidents in the pass have been reported to the Coast Guard. At least two reported collisions occurred in 1983. These two collisions appear to be a result of pilot error and/or care- lessness. In June 1983, the 300 foot Gale Wind was towing the 520 foot Resoff when a 300 foot stern trawler, Sunflower, ran through the tow line and struck the Resoff (Fairbanks Daily News Miner, June 14, 1983). The specific location of the collision was not reported. There were no reported injuries and neither vessel was damaged enough to cause a concern for’ sinking. The weather was reported as good. In September 1983, two South Korean freighters collided "near" Unimak Pass (Anchorage Times, September 1l, 1983). The 551 foot Pan Nova, which was carrying wheat and headed for Korea, collided with the Swibon just after midnight. There were no personal injuries, but the Pan Nova was damaged enough so that a U.S. Coast Guard cutter had to rescue its twenty-six member crew. Again, the weather was listed as good with only ten-knot winds, two-foot seas, and twelve miles visibility. According to one interviewed source (name withheld by request), this collision was a complete act of carelessness. The vessels were reported to have been on automatic pilot, and consequently, were unaware of each others' presence. 2.2.2 Coast Guard Activities The U.S. Coast Guard (USCG) recently conducted a study in Unimak Pass to determine if a vessel separation scheme is re- quired. The 1972 Port and Waterway Safety Act and subsequent admendments require the USCG to study navigable waterways, at least once every eight years, to determine if marine traffic levels and related navigational concerns necessitate a need for a vessel separation scheme. Their study estimated that approximately 3400 annual trips are currently made through Unimak Pass. This estimate was developed by applying a factor to 59 days of field data collected by a combination of Coast Guard cutters and buoy tenders making trips through the pass and an air reconnaissance (one trip in a C 130 Hercules) over the pass. The Coast Guard study concluded that a range of 3,000 to 4,000 annual transits of the pass are likely (Lt. Commander J.D. Asbury, Personal Communication). Their study suggests that the level of marine traffic using Unimak Pass does not warrant a vessel separation scheme. However, the final determination will be made in January 1985 (Lt. Commander J.D. Asbury, Personal Communication). Even if such a scheme is recommended by USCG, it will need to be ratified by the International Maritime Organization which is part of the United Nations. This course of action is necessary since maritime regulations specify that sea lanes beyond three miles of any country's land mass are available for international navigation purposes. 3.0 UNIMAK PASS VESSEL TRAFFIC Limited vessel traffic data are available for Unimak Pass. This section provides an estimate of base year traffic data and forecasts for 1985, 1990, 1995, and 2000. The traffic estimates are divided into four categories: OCS activities, fishing, natu- ral resources, and commercial shipping (both domestic traffic serving western and northern Alaska and international traffic via the great circle route). United States military operations (Navy and Coast Guard) using the pass for search and rescue missions, buoy tenders and international fisheries law enforcement are estimated to be less than 200 trips per year. They are not included in these traffic estimates. General assumptions asso- ciated with the estimates are based upon the review of available information and discussions with knowledgeable private industry and governmental agency representatives. 3.1 Current Traffic Estimates Table 3.1 presents an estimate of base year vessel trips through Unimak Pass. The base year is 1982. Approximately 2300 annual trips have been estimated. Of these trips, fishing ves- sels account for approximately 60 percent of the total trips. The remaining trips are comprised of commercial vessels, which are primarily linehaul cargo ships, and account for approximately 25 percent of the total; natural resource vessels account for about 10 percent and OCS vessels for the remaining 5 percent of the traffic. A recent Coast Guard study estimated the annual traffic to be approximately 30 percent more than this estimate (see Section 2.2.2). However, given the lack of a historical data base and the difference between the two methodologies in estimating the traffic levels, this was assumed to not represent a significant difference and/or concern. The timing and distribution of vessels in the pass are not known. However, an estimate of seventy percent of the traffic occurs between April and September was assumed. This time frame generally corresponds with the seasonal periods of "better" weather (except for visibility and fog) and the major fishing seasons in the Bering Sea area (U.S. Department of Commerce, 1983). TABLE 3.1 UNIMAK PASS VESSEL. TRAFFIC BASE YEAR* TRAFFIC CATEGORY NO. TRIPS OCS Vessels Support Traffic 120 Resource Tankers 0 Subtotal 120 Fishing Vessels Domestic 651 International 719 Subtotal 1370 Natural Resource Vessels Timber 220 Subtotal 220 Commercial Vessels Domestic 270 Foreign 310 Subtotal 580 TOTAL 2290 *This table was developed from the text in Section 3.1 and Tables 3.2 through 3.4. Source: Louis Berger and Associates, Inc., Anchorage, AK. 3.1.1 OCS Traffic At present, two types of OCS activities in northern and western Alaska result in traffic moving through Unimak Pass. The annual sealift to northern Alaska, serving Prudhoe Bay, Kuparuk River, and Beaufort Sea operations, constitutes the majority of this traffic. In 1983, 13 tugs and 26 barges made the trip (Louis Berger and Associates, 1984). In western Alaska, exploration activities are presently occurring as a result of the Norton Sound and St. George Basin lease sales. The Norton Sound Sale No. 57 was held March 15, 1983. The St. George Basin Sale No. 70 was held April 12, 1983. Using previous OCS traffic data developed for exploration activi- ties in these two areas, 42 annual trips through Unimak Pass have been estimated (Peat, Marwick, Mitchell & Company, 1981 and Peat, Marwick, Mitchell & Company and James Lindsay & Associates, 1980). These trips, combined with the sealift traffic of 78 roundtrips (13 tugs plus 26 barges times two), represent the total of the 120 trips shown in Table 3.1. 3.1.2 Fishing Vessels Domestic and international fishing activities account for the majority of vessel traffic currently using Unimak Pass. Domestic vessels principally originate from Seattle and the Puget Sound area. International traffic originates primarily from Japan, Korea, the Soviet Union, and Poland. Based on discussions with a number of industry and government sources, it is estimated that approximately 1,370 fishing-related movements were made through Unimak Pass during the 1982-1983 fishing season (Tables 3.2 and 3.3). Approximately fifty-three percent of these trips are believed to have been made by the international fleet. (See Table 3.3; 719 international fleet trips out of a total of 1370 trips.) Domestic fleet traffic through Unimak Pass is characterized primarily by crab vessels traveling to fishing grounds in the Bering Sea, joint venture and other trawlers working the rich fisheries located just north of Unimak Pass, and smaller commer- cial purseiners and craft pursuing the herring and salmon fisher- ies of Bristol Bay. It is estimated that these domestic fleet vessels currently make about 650 trips through Unimak Pass each year (Table 3.2). The international fleet which travels through Unimak Pass is comprised of trawlers, seiners, long-liners, factory ships, cargo transport vessels, snail pot vessels, and support tankers. Based on information provided by the National Marine Fisheries Service (NMFS), it is estimated that 512 international vessels operated in Alaskan waters during the 1982-1983 fishing season. Of these vessels, 176 operated exclusively in the central Bering Sea and the western Aleutian areas. The remaining 336 vessels fished and OT TABLE 3.2 DOMESTIC FLEET MOVEMENTS THROUGH UNIMAK PASS 1982-1983 FISHING SEASON AVERAGE VESSEL VESSEL TYPE/CLASS FLEET SIZE TRIPS/YEAR Crab Vessels (85'-130') 130 1 Joint Venture Trawlers (85'-130') 40 2 Other Bottomfish Trawlers (85'-130') 25 2 Red Herring Purseiners (32'-48') 150 1 Salmon Boats (18'-32') 241 1 TOTAL 566 ESTIMATED ANNUAL VESSEL MOVEMENTS THROUGH UNIMAK PASS 130 80 50 150 651 Sources: Alaska Department of Fish and Game, Commercial Fisheries Division, Kodiak, AK (Personal Communication with Marty Eaton) TAMS Engineers, Anchorage, AK (Personal Communication with Gary Schneider) Natural Resources Consultants, Seattle, WA, April 1984 Louis Berger and Associates, Inc., Anchorage, AK, April 1984 II TABLE 3.3 INTERNATIONAL FISHING FLEET MOVEMENTS THROUGH UNIMAK PASS 1982-1983 FISHING SEASON ESTIMATED ANNUAL AVERAGE ESTIMATED VESSEL VESSEL TRIPS FLEET SIZE* VESSEL TRIPS TO & FROM THROUGH VESSEL TYPE/CLASS (NO. OF VESSELS) TRIPS/YEAR ALASKAN WATERS UNIMAK PASS Trawlers Less than 290 metric tons GWT a 3 15 11 290-1399 metric tons GWT 121 3 363 272 Over 1400 metric tons GWT 55 3 165 124 Seiners 14 1 14 ll Long-liners 23 3 69 52 Factory Ships (processors) 9 1 9 7 Cargo Transport 102 3 306 230 Support Tankers 5 3 15 11 Snail Pot _ 2 1 _ 2 i TOTAL 336 2.85 958 719 * International Fleet estimates do not include approximately 176 other international vessels which operated exclusively in the central Bering Sea and the western Aleutian Chain. Source: National Marine Fisheries Service, Juneau, AK (Personal Communication with Vicki Vaughn) Louis Berger and Associates, Inc., Anchorage, AK traveled throughout Alaskan waters from the central Bering Sea to Yakutat. Using average vessel trip estimates by NMFS and confidential Japanese industry sources, a total estimate of sea- sonal trips (958) to and from Alaskan waters was developed. Assuming that seventy-five percent of these trips were made through Unimak Pass, it is estimated that the 336 vessels made approximately 720 trips through Unimak Pass for movements to and from the Gulf of Alaska, Bristol Bay, and the Bering Sea (Table 3.3). 3.1.3 Natural Resource Shipping The shipment of natural resources through Unimak Pass is characterized almost entirely by freighters transporting logs, cants, manufactured logs, and wood chips to Far East markets. These freighters typically transport approximately 1.5 to 4.0 million board feet of timber product per shipment. Since 1975, approximately 500,000 to 600,000 thousand board feet of timber are harvested annually in the State of Alaska (Alaska Department of Natural Resources, 1984). Approximately eighty percent of this product is shipped to Japan (Morehouse, 1984). Most of the exported timber originates from the southeast, e.g. Ketchikan. The current level of natural resource shipping movements through Unimak Pass is approximately 225 vessel trips associated with the export of timber products to the Near East. Potential shipping movements through the Pass from other natural resource development activities in Alaska have not materialized in recent years due to changing conditions in world coal and other mineral markets. 3.1.4 Commercial Shipping Unimak Pass is used by a number of domestic and foreign container vessels, freighters, tankers, and barges. The domestic ships predominately transport various types of freight and mate- rials to numerous Bering Sea, Bristol Bay, and Aleutian Islands communities. In 1982, some 680,000 short tons of waterborne freight were transported to various communities in the Bering Sea, Bristol Bay, the Aleutian Islands, and the northerly side of the Alaskan Peninsula (Table 3.4). Based on a review of past schedules, Phone conversations with selected shippers, and previous’ trans- portation reports, it is estimated that approximately 80 percent of all incoming freight to the area is transported via Unimak Pass. Therefore, assuming that 544,000 short tons of freight (80 percent of 680,000 short tons) were transported on vessels carrying an average annual vessel carrying capcity of 8,000 DWT, it is estimated that 136 one-way commercial vessel trips were 12 eT PORTS OF CALL Nome Yukon River Bering Sea Ports Pribilof/ St. Matthew Islands Bethel Dillingham Alaskan Peninsula (northerly side) Dutch Harbor TOTAL TABLE 3.4 1982 DOMESTIC WATERBORNE COMMERCE BERING SEA, BRISTOL BAY, ALEUTIAN ISLANDS, AND NORTHERLY SIDE OF ALASKAN PENINSULA FREIGHT VOLUMES (SHORT TONS) DOMESTIC INTERNATIONAL LOCAL INCOMING OUTBOUND IMPORT EXPORT INCOMING OUTBOUND TOTAL 42,398 2,496 a -4- --- --- 44,894 3,111 21 __ = __ 3 3,135 148, 708 8,788 32,097 _L _ 48,127 237,720 8,956 866 _ _L _ = 9,822 52,930 34,384 __ iL 38 8,753 96,105 38,294 4,540 __ i __ a 42,834 44,978 3,015 _ = 8,753 733 57,479 340,634 224,375 1,819 6,658 «172,313 745,799 680,009 278,485 33,916 6,658 8,791 229,929 1,237,788 Source: U.S. Army Corps of Engineers, 1984, made through Unimak Pass in 1982, This was converted to round- trips through the pass for a total of 272 vessel movements. Foreign vessels moving through Unimak Pass are generally providing service between United States west coast ports and Asian ports following the great circle route. These foreign sailings originate in Seattle, San Francisco, Portland, or Los Angeles and in Japan, Korea, and sometimes Taiwan. A previous estimate of 310 annual foreign vessel movements through Unimak Pass was used (Peat, Marwick, Mitchell & Company, 1981). 3.2 Future Traffic Projections Table 3.5 presents Unimak Pass vessel traffic projections for 1985, 1990, 1995, and 2000. Total traffic is projected to double between the base year and the year 2000 (2290 to 4600 trips). Significant increases in OCS vessels and other natural resource vessels using Unimak pass are expected to occur. In the peak traffic year (2000), OCS vessels are projected to account for approximately 24 percent of the total trips compared to 5 percent in the base year. Natural resource vessels are expected to account for approximately 28 percent of the _ total traffic compared to 10 percent in the base year. The number of fishing vessels using Unimak Pass are expected to remain generally constant throughout the forecast period. However, given the expected increases in other traffic compo- nents, the number of fishing vessels will represent only about 30 percent of the traffic in 2000 as compared to 60 percent esti- mated for the base year. For the number of commercial cargo vessels, a modest linear growth pattern is projected. This segment of the traffic is projected to account for about 18 percent of the traffic in 2000 as compared to 10 percent in the base year. 3.2.1 OCS Traffic Vessel traffic using Unimak Pass as a result of future OCS exploration and development in western and northern Alaska is very speculative. The major factors which will affect this traffic component are the specific locations of these activities and associated support facilities, timing, and where and how the developed resources will be transported to market. The current Federal Five-Year OCS Oil and Gas Leasing Sched- ule (July 1982) has thirteen lease offerings scheduled between 1982 and 1987 that could potentially result in increases in OCS traffic moving through Unimak Pass into western and northern Alaska. In order to develop an estimate of potential traffic, a 14 ST TABLE 3.5 TOTAL UNIMAK PASS VESSEL TRAFFIC PROJECTIONS* CATEGORY 1985 1990 1995 2000 OCS Vessels Support Traffic 170 410 290 280 Resource Tankers 0 140 410 840 Subtotal 170 55 700 1120 Fishing Vessels Domestic 651 651 651 651 International 719 719 719 719 Subtotal 1370 1370 1370 1370 Natural Resource Vessels Coal 16 16 216 216 Timber 224 224 224 224 Other 34 34 834 Subtotal 240 27 70 1270 Commercial Vessels Domestic 300 340 390 460 Foreign 320 340 360 380 Subtotal 620 680 750 840 TOTAL 2400 2870 3290 4600 * This table was developed from Tables 3.6 through 3.10 and the corresponding text in Section 3.2. Subtotals were rounded to the nearest ten, Source: Louis Berger and Associates, Inc., Anchorage, AK "most likely" scenario of cumulative exploration and development assumptions for the six OCS planning areas from which the’ thir- teen lease offerings originate in northern and western Alaska was developed. This included exploration only activities for the Norton Basin, Barrow Arch, and North Aleutian Basin, and a mean find scenario for the Diapir Field Basin, Navarin Basin and St. George Basin. Tables 3.6 and 3.7 are estimates of future OCS traffic required to support the "most likely" exploration and development scenario. These estimates have been developed from previous transportation impact studies and assumptions sponsored by the Social and Economic Studies Program. Starting in the 1990s, resource tankers serving the St. George and Navarin Basins are projected to be the major component of the OCS traffic in western Alaska (see Table 3.6). Supply vessels, barges and tugs serving these areas are projected to remain constant after commercial production begins. It is as- sumed that major linehaul vessels will supply the individual support bases which are assumed to be on the northern side of Unimak Pass. Smaller vessels and barges will then transship supplies to the individual sites as required. Consequently, given these assumptions, it is not likely that a _ significant amount of the support traffic will move through Unimak Pass on a regular basis. The sealift traffic forecasts (Table 3.7) assume a relatively high level of demand through early 1990. This is primarily a result of the continuing demands from current production at Prudhoe Bay and Kuparuk River and the exploration activities expected for the Diapir Field and the Barrow Arch lease areas. All resource production is assumed to be transport-— ed via the Trans-Alaska Pipeline System (TAPS). Table 3.8 presents the combined traffic projections of OCS activities in western and northern Alaska that are likely to use Unimak Pass. Between 1985 and 2000 total annual OCS traffic is expected to increase over 500 percent (170 to 1124 trips). 3.2.2 Fishing Vessels Future fishing-related traffic using Unimak Pass through the year 2000 is expected to continue at about the same levels as occurred in 1982-1983. This trend will continue because of the continued availability of an abundant groundfish resource in Alaskan waters, and competitive economic interests desiring to harvest these resources and provide fishery products to the 16 LT TABLE 3.6 WESTERN ALASKA OCS TRAFFIC PROJECTIONS USING UNIMAK PASS NORTON ST. GEORGE NAVARIN NORTH ALEUTIAN*** BASIN BASIN BASIN BASIN TOTAL TRIPS**** YEAR sve -RT#*® SV RT. sv RT sv RT sv RT 1985 5 27 64 1986 2 37 41 9 178 1987 25 56 13 188 1988 45 38 14 194 1989 59 68 13 280 1990 73 71 89 7 338 142 1991 58 239 110 336 478 1992 . 52 332 87 278 664 1993 49 285 78 254 570 1994 49 218 74 8 246 452 1995 49 177 74 28 246 410 1996 49 148 74 51 246 398 1997 49 128 74 87 246 430 1998 49 116 74 120 246 472 1999 49 107 74 225 246 664 2000 49 101 74 320 246 842 *SV = Supply vessels, barges, and tugs. **RT = Resource tankers, ***Exploration scenario for the North Aleutian Basin was assumed to be similar to the St. George Basin, since a previous analysis has not been developed. ****Converts individual trips into roundtrips by multiplying by two. Source: Peat, Marwick, Mitchell and Company and James Lindsay and Associates, 1980; and Louis Berger and Associates, 1984, 8T TABLE 3.7 SEALIFT TRAFFIC PROJECTIONS FOR 1985-2000 USING UNIMAK PASS PRUDHOE BAY & KUPARUK RIVER DIAPER FIELDS BARROW ARCH TOTAL ROUND TRIPS* YEAR TUGS BARGES TUGS BARGES TUGS BARGES TUGS BARGES 1985 6 12 12 23 36 70 1986 6 12 ‘12 23 2 3 40 76 1987 6 12 11 22 2 4 38 76 1988 6 12 10 20 2 4 36 72 1989 6 12 13 25 2 4 42 82 1990 6 12 4 7 3 5 26 48 1991 5 10 5 9 20 38 1992 5 10 8 16 26 52 1993 5 10 7 13 24 46 1994 5 10 3 5 16 30 1995 5 10 2 4 14 28 1996 4 8 2 4 12 24 1997 4 8 2 4 12 24 1998 4 8 2 4 12 24 1999 4 8 2 4 12 24 2000 4 8 2 4 12 24 *Converts individual trips into roundtrips by multiplying by two. Source: Louis Berger and Associates, 1984 and ERE Systems, Ltd., 1984, 61 TABLE 3.8 TOTAL OCS TRAFFIC PROJECTIONS USING UNIMAK PASS* WESTERN ALASKA NORTHERN ALASKA OCS TRAFFIC OCS TRAFFIC TOTAL OCS TRAFFIC SUPPORT RESOURCE SUPPORT SUPPORT RESOURCE YEAR TRAFFIC TANKERS TRAFFIC TRAFFIC TANKERS 1985 64 106 170 1986 178 116 294 1987 188 114 302 1988 194 108 302 1989 280 124 404 1990 338 142 74 412 142 1991 336 478 59 394 478 1992 278 664 78 356 664 1993 254 570 70 324 570 1994 246 452 46 292 452 1995 246 410 42 288 410 1996 246 398 36 282 398 1997 246 430 36 282 430 1998 246 472 36 282 472. 1999 246 664 36 282 664 2000 246 842 36 282 842 *Combines the traffic data from Tables 3.6 and 3.7. Source: Louis Berger and Associates, Inc., Anchorage, AK. international marketplace. Future changes in groundfish harvest-— ing technology are expected to influence the quality of the product transported to the marketplace rather than the amount of trips to and from Alaskan waters. No meaningful statistical estimates of the split between future domestic and international fleet movements through Unimak Pass can be made at this time. Decreasing harvest allocations to other nations, e.g. Japan, and the related emergence of consider- able American industry interest in harvesting Alaska's groundfish resources suggest significant changes in the composition of the future fleets which will pursue fisheries resources in Alaska. American and Japanese industry sources suggest that most, if not all, of the trawler vessels operating in Alaskan waters may be American vessels by the early 1990s. In response, much of the international fleet will likely be converted to factory (process- ing) ships until such time that American industry develops more factory trawlers (combined catching and processing ships). Con- sequently, the interim period between 1984 and the early 1990s will likely continue to be characterized by a growing number of joint ventures of American trawlers and international factory ships. Anticipated changes in the composition of the domestic and international fleet are expected to reduce the size of the inter- national fleet and increase the size of the American fleet. However, the amount of vessel trips through Unimak Pass is not expected to change more than plus or minus ten percent from current traffic levels. 3.2.3 Natural Resource Shipping The future composition and volume of natural resource ship- ments are expected to change considerably as exports of coal and other selected mineral ores begin to emerge in the late 1980s and early 1990s. The significance of these new exports upon trans- portation movements through Unimak Pass will depend upon final logistical decisions which will be made for each of three antici- pated resource development projects. Timber exports are general- ly expected to maintain present levels of both production and related vesel transport to Far East markets. More’ specific assumptions made in conjunction with each general type of re- source are described in the following paragraphs. 3.2.3.1 Coal Plans for four coal export projects have been identified in recent years which, if carried out, will generate coal-related shipping movements to the Near East. The four proposed projects 20 include (1) Sun-Eel's export of coal from the Usibelli Coal Mine in Healy to the Korea Electric Company, (2) Placer Amex export of coal from the Beluga Coal Fields to a yet undetermined market source in the Near East, (3) the export of coal in adjacent Beluga Coal Field lands by Dimond-Alaska Coal Company to a_ yet undefined market source in the Near East, and (4) the export of bituminous coal from the Bering coal fields near Cordova by KADCO and Chugach Alaska Corporation. After several months of uncertainty, Sun-Eel has’ finally arranged additional financial backing for its coal export pro- ject. Additional financing was obtained through its recent sale of half of its stock to Hyundai Merchant Marine. Sun-Eel's business move was apparently made in response to Korean’ govern- ment efforts to consolidate Korea's shipping industry. However, the stock sale also generated needed additional financing and/or financial leverage to Sun-Eel. Both firms finalized their agree- ment on March 25, 1984. Given the recent positive actions by Sun-Eel, the State of Alaska has resumed its efforts for the construction of dock improvements at the site of the proposed coal terminal facility in Seward. The latest project schedule indicates that approxi- mately 0.8 million tons of steam coal will be exported annually to Korea Electric Company. When in operation, three-weekly rail- car loads of coal will be transported from Healy to Seward where the coal will be onloaded to transport vessels having a carrying capacity of approximately 100,000 DWT. Plans by both Placer Amex and Dimond-Alaska Coal Company for the export of coal from adjacent fields in the Beluga area remain conceptual in nature at this time. Both investment groups have made estimates of potential quantities and quality of developable coal deposits, and have identified conceptual support require- ments for the extraction and transportation of the resource. No potential customers for the potential resource have been identi- fied for either project. However, the proximity of Alaska to the Near East, in comparison to the U.S. west coast, is one of vari- ous factors which suggest that any potential market for the resource will most likely be in the Near East. Given this cir- cumstance and numerous other undefined considerations, both of the projects remain, at best, uncertain (Morehouse, 1984). Preliminary estimates of the developable resource suggest that approximately 10 million short tons of coal will be recov- ered annually by Placer Amex while some 7.7 million short tons of coal will be extracted by Dimond-Alaska Coal Company. Respective project schedules suggest that potential export of the resource could begin sometime in the late 1980s or early 1990s. 21 Chugach Alaska Corporation and KADCO (a consortium of three Korean companies) are in the midst of completing their third and final year of preliminary exploration work which will indicate the size, volume and quantity of coal reserves in the Bering coal field near Cordova. Preparation of conceptual plans for required infrastructure support are expected to begin within the next two years. Agreements between Chugach Alaska Corporation and KADCO stipulate that KADCO has the first option to buy on _ reserves eventually developed. Consequently, the eventual market for these resources is expected to be in Korea. The timing of the Proposed project is difficult to assess at this early stage of the project. It is reasonable to assume, however, that this Project will generate future shipments of coal through Unimak Pass in light of current agreements between KADCO and Chugach Alaska Corporation. For the purposes of this forecast, it was assumed that only the Sun-Eel and Placer Amex project will begin operations before the year 2000 (Table 3.9). It was assumed that both of these Projects will export quantities currently estimated beginning in 1986 (Sun-Eel) and 1995 (Placer Amex). The potential vessel traffic which will be generated through the export of coal from the Sun-Eel and Placer Amex projects over the next fifteen years is presented in Table 3.9. The Sun-Eel project is expected to generate approximately sixteen annual vessel trips during the next ten years while the Placer Amex will require some 200 annual vessel trips beginning in 1995. 3.2.3.2 Other Minerals Although various known mineral deposits are located through- out the state, e.g. Ambler district, Admiralty Island, and the Delong Mountains, available data suggests that only three mineral development projects show promise during the forecast period. Similar to coal, numerous market and production cost considera- tions will continue to affect the viability of these two pro- jects. The export of minerals from each of these projects will likely generate vessel transport movements through Unimak Pass enroute to markets in British Columbia and the Near East. Cominco Alaska and NANA, Inc. are in the process of develop- ing a new lead/zinc/silver mine approximately 90 miles north of Kotzebue. Red Dog deposit, the source of minerals for this project, is estimated to contain 85 million tons of ore which contains 5 percent lead, 17 percent zinc, and 2.4 ounces of silver per ton of ore (Morehouse, 1984). As proposed, this project will begin operations in early 1988. Extracted ore will be exported at a rate of approximately 500,000 short tons of ore per year (Personal Communication, Noah, 1984). 22 €7 TABLE 3.9 NATURAL RESOURCE SHIPPING MOVEMENTS THROUGH UNIMAK PASS ESTIMATED ANNUAL VESSEL TRIPS YEARS 1985, 1990, ESTIMATED EXPORT VOLUME (MILLION SHORT TONS) 1995, AND 2000 UNIT TRANSPORT TYPE OF RESOURCE 1985 1990 1995 2000 SIZE (DWT) Minerals Coal 0.8 0.8 10.8 10.8 100,000 DWT Other Minerals - 0.5 0.5 40.5 30,000 DWT and 100,000 DWT* Timber 0.002 0.002 0.002 0.002 : 20 DWT TOTAL * Should the U.S. Borax Mine in Ketchikan go into production, 100,000 DWT vessel will be used. Source: Louis Berger and Associates, Inc., Anchorage, AK POTENTIAL VESSEL TRIPS VIA UNIMAK 1985 1990 1995 16 16 216 34 34 224 224 " 224 240 274 474 PASS 2000 216 834 224 1274 it is assumed that a larger Cominco officials estimate that approximately sixty percent of the ore will be shipped to Cominco's smelter in Trail, British Columbia. The remaining forty percent will be transported to yet undefined markets in Japan. Approximately eighteen miles southwest of Juneau is a miner- al deposit known as Greens Creek. This deposit, estimated to have some three million tons of reserves, contains ores with nine to ten percent zinc, three percent lead, and nine to ten ounces of silver per ton (Morehouse, 1984). Proposed plans call for mine production to begin in late 1986. Export quantities are estimated to be approximately 0.2 million ton per year over a fifteen-year period. The ultimate market for these resources has not been determined. For the purposes of this report, it is assumed that a future market will be found in the Near East. The U.S. Borax "Quartz Hill" molybdenum mine near Ketchikan is tentatively scheduled for production sometime in 1988. Pro- posed plans indicate that the mine will produce approximately 40,000 million tons of ore per year (Alaska Information Service, 1984). Even though the eventual market for the ore has not been identified, it is expected that the future market will be in the Near East as U.S. Borax will continue to have serious competition from a crowded American market (Alaska Information Service, 1984). Assuming that each of the three mineral projects come into production and are marketed as suggested, future vessel traffic in Unimak Pass would increase only slightly during the next ten years (Table 3.9). In the event that the U.S. Borax projects come on line by the year 2000, a significant additional traffic flow will be generated independently by this project (Table 3.9). 3.2.3.3 Timber State forestry officials expect that future timber exports to the Near East will occur at the present rate of approximately 440,000 million board feet per year to the year 2000 (Alaska Department of Natural Resources, Division of Forestry, 1984). Assuming an average freighter capacity of 3.75 million board feet (20 DWT) per load (based on discussions with the forestry offi- cials), the continued annual export volume of 440 million board feet of timber will generate approximately 225 vessel trips through Unimak Pass each year. 24 3.2.4 Commercial Shipping Future domestic commercial shipping can be estimated by assuming that such shipments will increase at the average annual rate of population growth. From 1970 to 1980, the average annual growth rate of population in the Aleutian Islands was approxi- mately 2.9 percent. Using this growth factor in conjunction with other assumptions made concerning current shipping activity, future shipping movements through Unimak Pass were calculated (Table 3.10). Application of the 2.9 percent annual growth rate to the 1982 year estimate of 544,000 short tons of freight via Unimak Pass formed the basis for the 1985 estimate. Table 3.10 suggests that future domestic commercial shipping movements through Unimak Pass will not increase significantly during the next fifteen years. By the year 2000, it is estimated that 460 annual domestic commercial shipping trips will be made through the pass. For foreign commercial vessels, previous estimates developed by Peat, Marwick, Mitchell and Company (1981) were assumed to be reasonable. These estimates are as follows: 320 foreign vessels in 1985; 340, in 1990; 360, in 1995; and 380, in 2000. 25 97 TALBE 3.10 FUTURE DOMESTIC COMMERCIAL SHIPPING MOVEMENTS THROUGH UNIMAK PASS 1985, 1990, 1995, AND 2000 ESTIMATED ESTIMATED SHIPPING VOLUMES SHIPPING VOLUMES TO ALEUTIANS, VIA UNIMAK BRISTOL BAY, PASS AT 80% AVERAGE AND WESTERN ALASKA OF TOTAL VOLUME VESSEL CARRYING YEAR (SHORT TONS) (SHORT TONS) CAPACITY (DWT 1985 740,892 592,714 8,000 1990 854,736 683,789 8,000 1995 986,072 788,858 8,000 2000 1,137,589 910,071 8,000 * ESTIMATED* VESSEL ROUNDTRIPS VIA _UNIMAK PASS 300 340 390 460 Eighty percent shipping volumes (short tons) divided by 8,000 DWT (average vessel carrying capacity) multiplied by 4 = estimated roundtrips via Unimak Pass. Rounded off. Source: Louis Berger and Associates, Inc., Anchorage, AK 4.0 PROBABILITY OF FUTURE COLLISIONS 4.1 Factors Affecting Collisions There are a variety of factors which determine whether or not a vessel collision will occur in a given location. These include the physical restrictions on vessels in the location, the number of vessels which come into the area, the speed of the vessels, the weather conditions (particularly visibility), the mechanical condition of the vessels, and the training and alert- ness of the crews. According to Devanney (1979) the single most complete analy- sis of vessel collisions was carried out for the English Channel in the area of the Dover Straits. A study by Wheatley (1972) examined 174 collisions in this area between 1958 and 1971. Another study covered a worldwide sample of data over a seventeen-year period (Cockroft, 1976) for collisions where a large vessel was involved, and the National Transportation Safety Board in 1979 examined all large vessel accidents in U.S. waters over a five-year period. These analyses all point out the importance of local charac- teristics and hazards which contribute to collisions, and the large variability in the physical condition and training of the ships' crews. Most collisions are caused by several contributory factors rather than a single factor. The most common contributo- ry factor was rules violations, followed by judgment errors, environmental conditions (especially fog), and other human er-— rors. However, there were several significant points discovered by these researchers which could be generalized to other locations. These were: 1. Most accidents occur in conditions of poor visibility (eighty percent of the Dover Straits and seventy per- cent of worldwide accidents occurred in poor visibili- ty). 2. The majority of accidents take place when vessels are crossing or overtaking each other. 3. Most of the ships that were involved in collisions were aware of the other ship, usually through radar contact. The visibility issue is even more of a collision factor when the frequency of low visibility conditions is taken into account. 27 In the Dover Straits poor visibility (less than 4000 m.) occur- red only six percent of the time, yet these time periods account- ed for eighty-two percent of the accidents. This relationship is particularly important in the case of Unimak Pass which has frequent fog. Another way to evaluate ship collisions in low visibility conditions has been used in both Japan and England where the accident rate in conditions of either good or poor visibility has been compared to the probability of random collisions with no avoidance maneuvers. In clear weather and good visibility the accident rate is 1/10,000 of the random probability. However, in poor visibility the rate is only 1/10 of the random probability (Devanney, 1979). According to Devanney, the main reason for the high colli- sion rate in poor visibility conditions, even when the vessels are aware of each other, is a basic ambiguity in the "rules of the road.” These rules call for a turn to starboard by both ships when they are approaching on a crossing course in a poten- tially dangerous’ situation. This works well when the_ ships approach each other head on or to port; but when they are ap- proaching slightly to starboard, a starboard turn could make the situation more dangerous. This situation causes the pilots to make an unpredictable choice of port or starboard turns. The situation is made worse in poor visibility when the pilots cannot visually observe the actions of the other vessel. In this circumstance a greater number of avoidance maneuvers are taken by approaching vessels and this tends to increase the probability of collisions rather than decrease it. 4.2 Collision Models As described above, the peculiarity of the data on vessel collisions and the variability of human behavior has made it difficult to model collisions between vessels. There is an attempt to correct this problem by the Coast Guard through simu- lation of specific sites with a Traffic Management Model now under development at the DOT Transportation Systems Center, based on previous port traffic research in the Netherlands. This model will allow the simulation of ship maneuvers with very site- specific data on hazards and other conditions. This reseaarch is being complemented by simulation of ship behavior at the DOT Com- puter Aided Operations Research Facility (CAORF) at Kings Point, New York and by the Marine Institute of Training and Graduate Studies in Baltimore. These research operations examine the crew's behavior under simulated conditions on the ship's’ bridge. 28 The most pertinent research on vessel collisions now avail- able has been carried out on a more general level. This includes research by Draper and Bennett (1972) for the Dover Straits and generalized by Operations Research Inc. (1974) and applied by Earl R. Combs (1981) for Alaskan conditions. The approach of these models is to define the probability of collision as _ the product of the probabilities of two separate events: (1) two vessels encounter each other and (2) the vessels collide in the encounter zone. The probability of encounter is a function of traffic lev- els, size of the passage or channel, speed and length of the vessels. The probability of collision given that two ships have an encounter is a function of visibility, condition of the ships and training of the crew, communications between ships and a set of random events that might cause a ship to deviate from its course. In the case of two ships proceeding in opposite directions through a navigation channel such as Unimak Pass, the number of possible encounters per year is given by Combs as: E = N?2 L/2KV Where N the number of vessel passages per year re i] the length of the waterway in nautical miles K = a constant equal to the number of hours in a year V = the average velocities of vessels in knots This equation gives the number of times per year that two vessels moving in opposite directions will be in the channel at the same time. This is defined as an encounter. From this equation it can be seen that the number of encounters increases with the square of the traffic level and in proportion to the length of the waterway. It decreases as average vessel speed increases (and ships spend less time in the waterway). The probability of a collision was then expressed as: C = P(C/E)Eb/W Where P(C/E) = the probability of a collision given an encounter E = the number of encounters per year b = the average clearance requirements of vessels in miles W = the average width of the waterway navigation channel in miles 29 The probability of a collision given an encounter depends on the alertness, behavior patterns, and avoidance maneuver expectations of ship crews, and must be estimated from appropriate research. This is then multiplied by the number of encounters (as. given from the first equation) and adjusted to take into account vessel clearance requirements and channel width. The larger the chan- nel, the lower the probability of collision. The larger the vessel and its clearance requirements, the greater the probabili- ty of collision. The Combs model described above was modified to take into account the difference in collision rates under poor visibility cited by Devanney, et al. and to take into account traffic varia- tion over the year. The first adjustment was accomplished by using a linear equation related to visibility rather than a constant for the conditional probability of collisions. The con- stant used by Combs assumes that the occurrence of poor visibili- ty in other locations is the same as that where the research was done (Dover Straits). This assumption does not hold for Unimak Pass where more frequent fog conditions are found. Therefore, the Dover data was converted to an equation which increases’ the probability of collisions in relation to the occurrence of poor visibility. The resulting equation, derived from the Dover research* is: P(C/E) = .002F + 2.85 x 1075 where F is the fraction of the year when fog or other poor visibility conditions are present. The second adjustment was accomplished through dividing K by a factor which reflects variation in traffic on a daily and seasonal basis over the year. The Combs model assumes that the traffic through the waterway is distributed evenly over all the hours of the year. In fact, we know that much of this traffic occurs in fishing seasons that are more active in summer months than in winter. Also many ships will time their passage through the pass to occur in daylight conditions when possible. The effect of these factors is significant in that it concentrates traffic into certain hours and increases the chances of a colli- sion as a result. *This was derived by ascribing Dover accidents to either poor visibility or good visibility conditions, then taking the poor visibility accident rate and dividing by the fraction of time when poor visibility occurred (.06). Rounded figures are used to indicate the level of accuracy. 30 While the exact distributions of vessels in the pass is not known, it is estimated that seventy percent of the traffic occurs in six months of the year, and that eighty percent of the traffic during each day occurs in daylight hours. This is the mathematical equivalent of traffic being concentrated in a 12 to 14 hour period per day over the year, and therefore an adjustment factor of K/1.85 was used instead of K in the Combs model. The resulting adjusted model takes the following form: 5 - - 2 C = (.002F + 2.85 x 10 5 yn? Lb = (.002F + 2.85 x 10 )N- Lb 2KVW/1.85 9470VW 4.3 Collisions in Unimak Pass Based on the estimates of marine traffic presented in the previous sections, the present probability of collisions in Uni- mak Pass is approximately one every 132 years. This calculation is based on the following characteristics for the two segments of the Unimak Pass waterway that we identified. Segment 1 begins approximately a mile east of the northeast tip of Ugamak Island at the southern entrance to the pass (see Figure 2.1 and 2.2). * SEGMENT WIDTH (W) LENGTH (L) 1 6-12 mi. 8 mi. 2 20-26 mi. 20 mi. We have calculated the probability of collisions for each segment and added them together to determine the total collision probability for the entire pass. (See Appendix A for details of this calculation.) The total vessel traffic, average length of all vessels, and average vessel speeds that are expected to use the pass are presented in Table 4.1. The average clearance required to avoid Maneuvers was assumed to be 800 feet (b = .13 nautical miles). *Unimak Pass is approximately 28 miles in length and varies in width from approximately 12 miles (between Unimak and Ugamak Islands, see Figure 2.1) to 26 miles. The range of widths depend on whether the entire area of the pass is considered or just the portion of the pass in international waters. In order to’ show the highest collision probabilities the narrowest widths are used. 31 ce TABLE 4.1 SUMMARY OF VESSEL TRAFFIC FORECASTS FOR UNIMAK PASS ANNUAL NUMBER OF PASSAGES * VESSEL TYPE AVERAGE LENGTH 1985 1990 1995 2000 *% 2 OCS Vessels Supply Vessels & Barges 500' 150 370 260 250 Tugs 100' 20 40 30 30 OCS Tankers 800' _ 0 140 410 840 Subtotal 170 550 700 1120 Fishing Vessels Small Boats 35' 391 391 391 391 Large Boats & Trawlers 115° 679 679 679 679 Processors & Long-liners 250! 59 59 59 59 Other 200! 241 241 241 241 Subtotal 1370 1370 137 1370 Natural Resource Vessels Resource Freighters 750' 240 270 470 1270 Subtotal 240 270 70 1270 Commercial Vessels Domestic & Foreign 350' 620 680 750 840 Subtotal 620 680 75 840 TOTAL 2400 2870 3290 4600 ¥ Estimate of the average length for vessel types by category. Average length of all vessels passing through Unimak Pass in the year 2000 is 478 feet. Estimate of average speed for all vessel types through Unimak Pass is 10 knots. He It is assumed that 90 percent of all OCS vessels are either supply vessels or barges. The remaining 10 percent are tugs. Source: Louis Berger and Associates. Ine. Anchorage AK The probability of poor visibility in Unimak Pass was deter- mined from U.S. Department of Commerce, National Oceanic and Atmospheric Administration data which is derived from the reports of private vessels using the pass. These ships reported ten to fourteen percent poor annual visibility (less than two nautical miles). This data is biased toward better weather conditions and was therefore adjusted to reflect actual conditions. In addition the weather in peak traffic months (which is worse than the yearly average ten to twenty days per month poor visibility in the summer) was weighted more heavily to reflect conditions encountered by the average vessel in Unimak Pass. These adjust- ments result in an estimate of twenty-one percent poor visibility conditions for all vessels using the pass. (F = .21) The resulting probability of collisions in Unimak Pass with and without OCS activities is summarized in Table 4.2. This table confirms our initial readings that there is a very low probability of collisions even at the highest traffic levels in 2000. The presence of OCS traffic only raises the probability of a collision from one in fifty-seven years to one in thirty-three years. This model can also be used to calculate a traffic threshold which would show when OCS marine traffic through the pass would create a significant increase in the probability of a collision. It is up to the MMS to determine what probability of collision would constitute a significant impact. However, one possible definition could be an increase in OCS traffic which would lead to the probability of one collision per year (P = 1.0) or one collision every two years (or P = 0.5). The traffic levels that would lead to these levels of prob- ability are as follows: PROBABILITY TOTAL VESSEL EXTRA TRAFFIC OVER PER YEAR TRIPS REQUIRED FORECASTS LEVELS WITHOUT OCS TRAFFIC 1990 2000 0.5 18,630 per year 15,760 13,030 1.0 26,350 per year 23,480 21,750 The extra traffic needed to reach even the 0.5 probability level is more than twelve times the maximum OCS traffic expected through Unimak Pass through the year 2000. 33 TABLE 4.2 FORECAST OF COLLISIONS IN UNIMAK PASS 1983 1990 2000 A. Without OCS Activity Probability of collision in one year - 0068 -0078 -0174 Number of years for one collision to be expected 147 128 57 B. With OCS Activity Probability of collision in one year -0076 -0119 305 Number of years for one collision to be expected 132 84 33 Source: Louis Berger and Associates, Inc., Anchorage, AK (See Appendix A for calculations). 34 4.4 Relation of Model Results to Recent Experience The model used to describe the probabilities of collisions is a model based partly on theory and partly on experimental evi- dence gathered in the Dover Straits and analyzed by Devanney, Cockroft, and others. It has been adjusted to correspond to conditions in Unimak Pass. However it still contains some basic assumptions which affect its usefulness as a predictor of reali- ty. These are: 1. Crew alertness and competence in Unimak Pass is the same as in other places (i.e., Dover Straits). 2. Vessel equipment and detection ability is on average, the same as in other locations (i.e., Dover Straits). 3. Accidents are a result of errors and equipment failures, not intentional. 4. The navigation conditions in Unimak Pass are not unusual. In so far as we can determine, these assumptions are accurate for Unimak Pass in normal circumstances. In certain circumstances, however, it is possible to have a combination of events which gteatly increase the probability of an accident (i.e., several vessels converging on the narrow part of the pass in poor visibility). The model does not take these unlikely events into account, except in so far as they occurred in the Dover Straits. In addition, intentional accidents will not be predicted by this model. It is also clear that cases of extreme fatigue, such as fishing crews experience in the Bering Sea, can affect alertness and competence and could lead to accidents. There are currently about 1500 encounters per year in the Unimak Pass and _ possibly 300 in poor visibility. Despite the low odds, a really fatigued crew could cause an accident if they happened to meet these conditions. The laws of probabilty and the estimates used here do not rule out the additional accidents these unusual circumstances may encourage. If there continues to be more accidents than this model predicts, then specific research will be required to identify the special elements of the Unimak Pass environment or its vessel traffic that make it more dangerous than other locations of a similar type. 35 4.5 Conclusion Based on the traffic forecasts, our stated assumptions and the modified collision model developed as part of this research, we have concluded that the expected levels of future OCS demands on western and northern Alaska will not cause a _ significant increase in the occurrence of vessel collisions in Unimak Pass. 36 Base Year 1985 1990 1995 2000 APPENDIX A COLLISION PROBABILITY CALCULATIONS Constant Parameters 1 -13 nautical miles 8 nautical miles utical miles 6 nautical miles a) Fraction of time poor visibility; F = .2 b) Average vessel clearance; b = c) Average vessel speeds; V = 10 knot d) Channel length segment 1: L = segment 2: L = 20 na e) Minimum channel width segment 1: W = segment 2: W = 20 na Reduced Equations Segment 1: C = [.002(.21) + 2.85 x 10-5 ] N2 x 8x .13 9470 x 10 x 6 Segment 2: C = [.002(.21) + 2.85 x 1075 ] N2 x 20 x .1 9470 x 10 x 20 Probability of a Collision in Either Segment (P = P = P, ) T 1 Probability by Key Year ANNUAL TRAFFIC* wo/ocs w/ocs 2170 2290 2230 2400 2320 2870 2590 3290 3480 4600 *From Table 4.1. **Using traffic as N in equation 3 above. ***1 divided by the probability per year. PROBABILIT PER YEAR** wo/ocs -0068 -0071 -0078 -0097 0174 37 Y w/ocs -0076 -0082 -0119 -0156 0305 utical miles 8.2 x 10719 y2 3 6.2 x 10719 y2 14.4 x 10719 y2 EXPECTED YEARS FOR ONE COLLISION*** wo/ocs w/OCS 147 132 141 122 128 84 103 64 57 33 BIBLIOGRAPHY Alaska Consultants, Inc./PRC Harris, Inc. January 1981. South- central Region of Alaska Deep-Draft Navigation Study. Anchorage. (Prepared for U.S. Army Corps of Engineers, Alaska District). Alaska Department of Natural Resources, Division of Forestry and the U.S. Department of Agriculture, Forest Service. 1984 (unpub- lished preliminary draft). Alaska 1983-1984 Forest Industry Directory. Alaska Department of Natural Resources. Anchorage, Alaska. Alaska Geographic, The Aleutians, Volume 7, Number 3, 1980. Alaska Information Service. 1984. The Alaska Economic Report "Quartz Hill Faces Tough World Markets" (February 16, 1984 edi- tion). Volume No. 3/84. Anchorage, Alaska. Anchorage Times. March 13, 1984, Coast Guard Studies Pass in Aleutians. Anchorage Times. March 20, 1984. Coast Guard Facility Proposed for Unalaska. Anchorage Times. September 11, 1983. South Korean Ships Col- lide. CAORF. 1977. Proceedings of First CAORF Symposium, June 23 and 24, 1977. National Marine Research Council, Kings Point, New York. Cockroft, A. N. 1976. "Statistics of Collisions at Sea." Jour- nal of Institute of Navigation. Volume 29, Number 3. Devanney, J. W., Protopapa, S., and Klock, R. 1979. "Tanker Spills, Collisions, and Groundings." MIT Sea Grant Report 1979- 14, D.M.J.M. October 1980. Draft Aleutian and Southwest Alaska Multi Modal Transportation Study. Anchorage (Prepared for the Alaska Department of Transportation and Public Facilities. D.M.J.M. Forssen. June 1980. Draft Aleutian and Southwest Alaska Coastal Ferry Study. Anchorage. (Prepared for the Alaska Department of Transportation and Public Facilities.) Draper and Bennett. 1972. "Modelling and Counter Rates in Marine Traffic Flows with Particular Application to Dover Straits." Journal of Institute of Navigation. Volume 25, Num- ber 3. 38 Earl R. Combs, Inc. October 1981. St. George Basin and North Aleutian Shelf Commercial Fishing Analysis. Alaska OCS Social and Economic Studies Program Technical Report No. 60 Mercer Island, Washington. (Prepared for Minerals Management Service, Alaska Outer Continental Shelf Office.) Energy Resources Co., Inc. and E.G. Frankel, Inc. 1978. Study to Assess the Impact of Alaska Petroleum Development on the Coast Guard through the Year 2000. Task 2, Marine Vessel Activity. Cambridge, MA (Prepared for U.S. Coast Guard.) ERE Systems, Ltd. May 1984. Barrow Arch Transportation Systems Impact Analysis, Draft Final Report. Arlington, VA. (Prepared for Minerals Management Service, Alaska Outer Continental Shelf Office.) Fairbanks Daily News Miner. June 14, 1983. Vessels Collide in Unimak Pass. Government of Canada. 1980. Arctic Pilot Project (Northern Component.) Report of the Environmental Assessment Panel. Otta- wa, Ontario, Canada. Hargreaves, E. R. 1973. "Safety of Navigation in the Channel." Papers of the International Congress of the European and American Institute of Navigation; Collisions Avoidance and Rendezvous Navigation, October 2-6, 1973. Hanover, Germany. Louis Berger and Associates, Inc. February 1984. Diaper Field (Sale 87) Transportation Systems Impacts Analysis. Alaska OCS Social and Economic Studies. Program Technical Report No. 105. Anchorage. (Prepared for Minerals Management Service, Alaska Outer Continental Shelf Office.) Louis Berger and Associates, Inc. May 1983. Navarin Basin (Sale 83) Transportation Systems Impact Analysis. Alaska OCS Social and Economic Studies Program Technical Report No. 84. Fairbanks. (Prepared for Minerals Management Service, Alaska Outer Continen- tal Shelf Office.) Louis Berger and Associates, Inc. with Philleo Engineering & Architectural Services, Inc. January 1982. Western and Arctic Alaska Transportation Study. Fairbanks. (Prepared for State of Alaska Department of Transportation and Public Facilities.) Morehouse, Thomas, ed. Contributing authors: Berman, Matthew; Codey, Richard; Morehouse, Thomas; Tuck, Bradford; Tussing, Ar- lon; and Weeden, Robert. 1984. Alaskan Resources Development: Issues of the 1980s. Westview Press. Boulder, Colorado. 39 Natural Resources Consultants. 1984, Projections of Domestic Fleet and Effort Required to Harvest the Alaska Groundfish Opti- mum Yield. North Pacific Fishery Management Council. Anchorage, Alaska. Operations Research Incorporated. 1974 Spill Risk Analysis Pro- gram, Phase II; Methodology Development and Demonstration. U.S. Coast Guard Technical Report CG-D-15-75. Pacific Fishing 1984 Yearbook. "A Look Back at '83 and Ahead to '84." Pacific Fishing. Seattle, Washington. Peat, Marwick, Mitchell & Company. September 1981. St. George Basin Petroleum Development Scenarios Transportation Systems Analysis. Alaska OCS Socioeconomic Studies Program Technical Report No. 58. Anchorage. (Prepared for Bureau of Land Manage- ment, Alaska Outer Continental Shelf Office.) Peat, Marwick, Mitchell & Company and James Lindsay & Associates. March 1980. Bering-Norton Petroleum Development Scenarios Trans- portation Systems Analysis. Alaska OCS Socioeconomic Studies Program, Technical Report 65. Anchorage. (Prepared for Bureau of Land Management, Alaska Outer Continental Shelf Office.) U.S. Army Corps of Engineers. 1984. Waterborne Commerce of the United States, CY 1982, Part 4, Waterways and Harbors, Pacific Coast, Alaska and Hawaii. Department of the Army. U.S. Department of Commerce, National Oceanic and Atmospheric Administration. January 1983. U.S. Coast Pilot Number 9 Pacific and Arctic Coasts Alaska: Cape Spencer to Beaufort Sea. Elev- enth Edition. Washington. U.S. Department of Transportation, Coast Guard. 1979. Draft EIS for Puget Sound Vessel Traffic Service Tank Vessel Operations Regulations. Seattle, Washington. Wheatley, J. H. 1972. "Circumstances of Collisions and Strand- ings." Marine Traffic Engineering. Proceedings of the Royal Institute of Navigation and Naval Architect Conference. 40 Personal Communications Personal Communication. 1984. Confidential Japanese fishing industry representative temporarily based in Anchorage, Alaska. Personal Communication. 1984, Mr. Gene Fine, superintendent, Southeast Stevedoring Company. Ketchikan, Alaska. Personal Communication. 1984, Mr. Steve Hughes, Natural Re- sources Consultants. Seattle, Washington. Personal Communication. 1984, Mr. Harry Noah, Cominco Alaska. Anchorage, Alaska. Personal Communication. 1984. Ms. Vicki Vaughn, National Marine Fisheries Service. Juneau, Alaska. Personal Communication. 1984, Lt. Commander J. D. Asbury, Chief, Coast Guard's Marine Port Safety Branch. Juneau, Alaska. Personal Communication. 1984, Captain Thurston, Foss’ Alaska Lines. Anchorage, Alaska. Personal Communication. 1984. Mr. Bob Bradley, President, Southwest Alaska Pilots Association. Homer, Alaska. Personal Communication. 1984. Captain Larkin, American President Line. Oakland, California. 41