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57 One way to improve vessel survivability is to limit the hazards that a vessel is likely to encounter during waterborne operations. Such limitations are already in place to some extent through restrictions that limit WWII DUKWs and Stretch Ducks to protected waters. But these restrictions only work if the definition of âprotected watersâ indeed excludes all bodies of water capable of experiencing conditions that may threaten a DUKW. Recent major casualty events in the United States indicate that the current definition of âprotected watersâ may not adequately protect DUKWs. In addition to reviewing casualty events and regulations, this chapter catalogs the factors an Officer in Charge, Marine Inspection (OCMI) may want to consider in evaluating the risks associated with operating a DUKW on a specific body of water or a specific route on a body of water. The current operating area evaluation method, which depends on the type of body of water, could be improved by considering a consistent set of evalu- ation criteria. Although blanket prohibitions may be necessary, limiting operating areas by time may present another option to reduce the risks associated with an operating area. As for severe weather, this chapter ex- plains how the National Weather Serviceâs (NWSâs) alert system could be leveraged to provide a straightforward and effective way of consistently restricting operating areas and times to reduce the risk that DUKWs are on the water during weather that threatens a vesselâs survivability. Set- ting operating restrictions based on the NWSâs alert system would require operators to adopt operat ing procedures, acquire equipment, and provide training to adequately monitor and respond to severe weather. 4 Operating Areas
58 OPTIONS FOR IMPROVING THE SAFETY OF DUKW TYPE AMPHIBIOUS VESSELS OPERATING AREAS AND CASUALTY EVENTS The operating areas of the Stretch Duck 7 and DUKW 34 created the con- ditions that made the vessels vulnerable to operator errors. Stretch Duck 7 took passengers on Table Rock Lake, created by a dam on the White River in the Ozark Mountains of southern Missouri. On Stretch Duck 7âs route, the bottom of the 43,000-acre lake dropped off quickly from the shore. The boat was eventually recovered from a depth of 85 feet. As a dam-created lake in the mountains, Table Rock Lake has a complex shoreline. Fetchâthe straight distance wind can travel over the waterâranges from 1.55 to 3.7 miles for winds out of the north. Fetch affects wave height.1 Southern Missouri is in a part of the United States prone to severe thunderstorms during the summer. A derecho, the type of thunderstorm that hit Table Rock Lake on July 19, 2018, is a particularly severe type of thunderstorm, characterized by strong, relatively long-lasting straight- line winds. NWS issued a severe thunderstorm watch 7 hours before and a severe thunderstorm warning 23 minutes before Stretch Duck 7 entered the water. Derecho winds hit in advance of the rain line and can appear suddenly. When Stretch Duck 7 entered the water, the surface of the lake was flat and calm. Five minutes later, the squall line hit; within 15 seconds the water surface went from calm to white-capped waves. NWS determined the winds from this squall ranged from 50 to 65 miles per hour (45 to 55 knots) for 30 minutes. Waves were from 2.7 to 3.7 feet, with some estimated as high as 4.2 feet. The wind speeds and wave heights significantly exceeded the maximum operating restrictions in the Stretch Duck 7âs Certificate of Inspection (COI) of wave heights of 2.0 feet and winds of 35 miles per hour. DUKW 34âs operating area, the Delaware River near Philadelphia, put it at risk of collision with commercial vessels. When DUKW 34 experienced mechanical trouble, the crew shut down the engine and anchored the boat almost in the center of the navigation channel used by deep draft vessels and commercial barges. At the time of anchoring, the bargeâs tugboat, the Caribbean Sea, was 0.3 nautical miles (1,823 feet) from DUKW 34. Human error was ultimately responsible for the collision, but the operating area set the stage for human fallibility to produce deadly results.2 1 NTSB, 2020, âSinking of Amphibious Passenger Vessel Stretch Duck 7, Table Rock Lake, near Branson, MO, July 19, 2018,â Marine Accident Report NTSB/MAR/20-01, April 28. https://www.ntsb.gov/investigations/AccidentReports/Reports/MAR2001.pdf. 2 NTSB, 2011, âCollision of Tugboat/Barge Caribbean Sea/The Resource with Amphibious Passenger Vessel DUKW34, Philadelphia, PA, July 7, 2010,â Marine Accident Report NTSB/ MAR-11/02, June 21. https://www.ntsb.gov/investigations/Pages/DCA10MM025.aspx.
OPERATING AREAS 59 REGULATIONS AND NVIC 1-01 Operating areas for DUKWs are currently limited in their stability letters to either âprotected watersâ or âpartially protected watersâ (see Box 4-1). Only Truck Ducks, which have a higher freeboard, are allowed to operate in partially protected waters. A DUKWâs operating area is further restricted in its COI, as determined by the OCMI. The determination of operating areas and operating restrictions is a subjective process highly dependent on BOX 4-1 Subchapter T Regulations Limiting Routes 46 CFR § 176.110 Routes Permitted a. The area of operation for each vessel and any necessary operational limits are determined by the cognizant OCMI and recorded on the vesselâs Certificate of Inspection. Each area of operation, referred to as a route, is described on the Certificate of Inspection under the major headings âOceans,â âCoastwise,â âLimited Coastwise,â âGreat Lakes,â âLakes, Bays, and Sounds,â or âRivers,â as applicable. Further limitations imposed or extensions granted are described by reference to bodies of waters, geographical points, distance from geographical points, dis- tances from land, depths of channel, seasonal limitations, and similar factors. b. Operation of a vessel on a route of lesser severity than those specifically described or designated on the Certificate of Inspection is permitted unless expressly prohibited on the Certificate of Inspection. The general order of severity of routes is: oceans, coastwise, limited coastwise, Great Lakes, lakes, bays, and sounds, and rivers. The cognizant OCMI may prohibit a vessel from operating on a route of lesser severity than the primary route a vessel is authorized to operate on if local conditions necessitate such a restriction. c. Non-self-propelled vessels are prohibited from operating on an oceans, coastwise, limited coastwise, or Great Lakes route unless the Comman- dant approves such a route. d. When designating a permitted route or imposing any operational limits on a vessel, the OCMI may consider: 1. Requirements of this subchapter for which compliance is based on the route of the vessel; 2. The performance capabilities of the vessel based on design, scantlings, stability, subdivision, propulsion, speed, operating modes, maneuverability, and other characteristics; 3. The suitability of the vessel for nighttime operations; and 4. The suitability of the vessel for all environmental conditions. SOURCE: https://www.ecfr.gov/current/title-46/chapter-I/subchapter-T/part-176.
60 OPTIONS FOR IMPROVING THE SAFETY OF DUKW TYPE AMPHIBIOUS VESSELS the expertise of the OCMI. OCMIs base their decisions on current and past waterway use, marine casualty information, legal and regulatory standards, and stakeholder input from sources like local Harbor Safety Committees and regional or trade specific Safety Advisory Committees. Each DUKWâs COI has a âRoute Permitted and Conditions of Opera- tionâ section that details the local restrictions imposed by the OCMI. All COIs include a general route permitted: DUKWs are assigned either âriversâ or âlakes, bays, and sounds.â In addition, the OCMI may place additional operating restrictions, such as time limits on the duration of waterborne trips, descriptions of the defined geographical area (e.g., the Tennessee River between Mile Markers 463 and 465),3 and maximum wind speeds and wave heights. For the classification of the body of water, the local OCMI makes this determination mostly based on local knowledge and the availability of âharbors of safe refuge.â 46 CFR 175.400 defines a âharbor of safe refugeâ as âa port, inlet, or other body of water normally sheltered from heavy seas by land and in which a vessel can navigate and safely moor.â The OCMI determines whether a location can function as a harbor of safe refuge for a specific vessel, based on the vesselâs size, maneuverability, and mooring gear. There are no written guidelines or policies that provide definitive and uniform methods on which OCMIs can base their determination. Further- more, the definitions provided in Subchapter T (46 CFR 175.400) for the various route designations are open to interpretation. For example, âriversâ could mean a route on any of the following waters: 1. A river, 2. A canal, or 3. Such other similar waters as may be designated by a Coast Guard District Commander. âLakes, bays, and soundsâ means a route on any of the following waters: 1. A lake other than the Great Lakes, 2. A bay, 3. A sound, or 4. Such other similar waters as may be designated by a Coast Guard District Commander. 3 A. Moyers, Chattanooga Ducks, presentation to the committee, March 2021. For example, the COI for Chattanooga Ducks limits operations to daylight on the Tennessee River only between Mile Markers 463 and 465.
OPERATING AREAS 61 The designation as a river or a lake, bay, or sound may not capture what makes an operating area higher or lower risk for DUKW operations. Many lakes, bays, and sounds are benign bodies of water that are generally calm and protected from large waves and strong winds. However, some lakes are known for high winds that appear daily, such as Flathead Lake, Montana, and Lake Tahoe in Nevada and California. Table Rock Lake was classified as protected waters, even though portions of the lake have fetches of 1 to 4 miles. Many mid-continent reservoirs and pools created by flood control or navigation dams may have similar fetches. Similarly, a river can be anything from a languid stream meandering through pastures to a swift-flowing torrent between high banks to a broad expanse of pool water, exposed to sudden and unpredictable winds, includ- ing tornadoes and thunderstorms. Rivers can be as innocuous as the upper reaches of the Potomac River and countless other rivers throughout the 50 states. In contrast, the Columbia River Gorge, near Hood River, Oregon, is renowned as the windsurfing capital of the world, and the Salmon River in Idaho is notorious as the âriver of no return.â A river designation includes the Fox River in northern Illinois, which is barely 100 feet across in most places, as well as the Mississippi and Missouri rivers, which in places are a mile wide. Compliance with the operating restrictions in the COI is the responsi- bility of the crew and land-based support personnel. For maximum wind speeds and wave heights operating restrictions, the operator must obtain up-to-date weather information far enough in advance to make the decision to cancel the waterborne portion of a tour or to cut short a tour and safely leave the water. Wave heights in excess of limitations can also be created by the wakes of large high-speed recreational or commercial vessels, a situation where a DUKWâs crew would have little control over once on the water. FACTORS FOR EVALUATING OPERATING AREAS The evaluation of a DUKWâs operating area requires knowledge of the capabilities of the vessel and the range of operating conditions likely to be found on the body of water. The wide variability within types of water bodies and types of DUKWs complicates efforts to create a definitive guide for designating operating areas. Still, developing a consistent set of evalua- tion standards is likely a feasible endeavor. Vessel Weaknesses Relative to other small passenger excursion vessels, DUKWs have several known design weaknesses that compromise their ability to deal with wind, waves, and other boat traffic. Forward speeds are slow, typically six knots
62 OPTIONS FOR IMPROVING THE SAFETY OF DUKW TYPE AMPHIBIOUS VESSELS or less and speeds in reverse are only two knots, according to the U.S. Armyâs DUKW Operations Manual. Steering is also poor, particularly if there are any significant crosswinds or currents. In addition, DUKWs do not have a traditional bow; they have a scow bow and modified truck hood that, when the bow is turned into a wave, acts more as a scoop. The bow design and low freeboard add to flooding risk. DUWKs also have reliability issues, as reviewed previously in Tables 2-2 and 2-3. Stretch Ducks and Truck Ducks are not more reliable than WWII DUKWs. DUKWs are particularly vulnerable to a loss or reduction of vessel propulsion and steering. High-Traffic Areas Because of the DUKWâs inherent maneuverability limitations, the presence of large commercial ships is a major safety concern. These much larger vessels are likely to be moving at higher speeds than a DUKW. These ships may also be operating in a defined channel, limiting their ability to go around a DUKW in distress. The small silhouette of a DUKW may not be easily visible from the pilothouse of a commercial tug and barge combina- tion, particularly when the tug is pushing or working alongside the barge. The presence of large numbers of recreational craft also presents a safety risk to DUKWs. Some recreational craft are capable of higher speeds and may be operated unpredictably by mariners with a range of skill levels. Operating a DUKW in or near a busy marina or waterway will increase the risk of collisions, especially given the difficulty a typical DUKW will have getting out of harmâs way even if the other vessel legally has the right of way. Large wakes, from commercial ships or reckless recreational craft, may be dangerous for DUKWs because of the bow design and limited maneu- verability. Although the presence of other commercial or recreational craft mayâand hasâprovided benefits as âGood Samaritanâ rescue craft, this benefit should be weighed against their potential dangers. Wind and Waves A DUKWâs operational weaknesses limit its ability to survive when caught in a storm. DUKWs have such poor maneuverability that high winds greatly increase the likelihood that a DUKW will lose control and hit things, run aground, or be unable to avoid collisions. Even if just 10 feet from a dock, the wind and waves could prevent a DUKW from landing safely. If docked, large waves pounding the boat may make it unsafe for passengers to dis- embark. Anchoring a DUKW to wait out a storm is also not a safe solution. In addition to the DUKWâs bow being prone to shipping water (or taking
OPERATING AREAS 63 on water), the anchor would restrain the DUKW from rising to the waves, increasing the likelihood of water coming over the bow. Safely beaching a DUKW during an emergency will depend on the water bottomâs type and contour, the wind direction and speed, and the available space ashore to park the DUKW or unload passengers. It may be possible for a DUKW caught in a storm to escape to land via âsafe refuge locationsâ (see Box 4-2). These are places such as docks or boat ramps where a DUKW could safely disembark passengers or escape onto land before a storm struck. These docks or boat ramps would be in addition to ramps or docks normally used to enter and exit during a tour. OPERATING RESTRICTIONS DURING SEVERE WEATHER The committee considered two approaches that the United States Coast Guard (USCG) could use to evaluate weather risks and apply appropri- ate safeguards to enhance weather-related safety. One approach evaluates each proposed route individually and develops a probability assessment BOX 4-2 Safe Refuge Locations for Escape onto Land The committee considers âsafe refuge locationsâ to be places such as docks or boat ramps where a DUKW could safely disembark passengers or escape onto land in an emergency. The close proximity of safe refuge locations may be a factor the Coast Guard considers in evaluating an operating area or operating restrictions. To determine whether safe refuge locations are available, the following factors could be considered: ⢠The distance from the vesselâs normal track line/tour path. ⢠Expected warning time for severe weather. ⢠For docks: o Are mooring lines and cleats available? o Is the DUKW set up for passengers to egress onto a dock? o Is the crew trained in the debarkation procedure? o Are the docks physically suitable for a DUKW to safely moor up to? o Is shelter available on or near the dock? An ideal safe refuge location would allow all passengers to be safely evacu- ated from the DUKW to a secure shelter before a storm hits. Close proximity of a shoreline or beach should not be considered a safe refuge location in a storm event unless the shoreline is such that the DUKW can exit the water and drive to a safe location.
64 OPTIONS FOR IMPROVING THE SAFETY OF DUKW TYPE AMPHIBIOUS VESSELS of weather hazards based on historic weather data, vessel particulars, and waterway characteristics. The second approach leverages NWSâs integrated severe weather alert system. The committee concluded that tying operating restrictions to the severe weather alert system was more feasible than the individual assessments of routes. Although an individual assessment of weather hazards for each pro- posed operating area would provide a tailored picture of risks, the process would be labor intensive, rely heavily on the availability of weather data, and likely involve the extrapolation of weather information from large geographic areas down to a very small DUKW operating area. In addi- tion, because of the extensive effort needed to carry out an individualized weather risk assessment, the committee is concerned that OCMIs would rarely reconsider a completed evaluation unless some type of event, such as a major marine casualty, prompted re-evaluation. Setting operating restrictions according to the severe weather infor- mation produced by NWS would take advantage of NWSâs real-time, mature, dynamic, and continually improving tools. NWS has developed an integrated severe weather alert system with the intent âto minimize injury, death, and property damage due to hazards such as severe weather and flooding. In other words, the goal of a warning is to provide sufficient time for people to get out of harmâs way.â NWS issues watches, warnings, and advisories through evaluating data from remote sensing devices, such as radar and satellites; on-site observing devices, such as river and rain gauges and automated flood warning systems; and eyewitness reports. NWS coor- dinates with all levels of government and the private sector to disseminate alerts of a hazard on multiple platforms. NWS is also committed to leading or coordinating outreach and educational initiatives designed to increase the publicâs awareness of safe responses to weather emergencies.4 With respect to the Stretch Duck 7 sinking, the weather alert system provided the necessary and timely information for operators to have made the decision to cancel the upcoming tour. NWS issued a severe thunder- storm watch for the area 7 hours prior to the accident, followed by a severe thunderstorm warning 1 minute before the vessel departed from the pas- senger boarding facility and 23 minutes before it entered the water. Had the vessel been restricted from conducting waterborne operations during a severe weather warning through either regulation or an operating restric- tion, the casualty could have been prevented. Leveraging NWSâs expertise and the agencyâs alert system will provide a consistent and simpler method for addressing weather-related risks. As 4 National Weather Service (NWS), 2018, âWarning Coordination and Hazard Awareness,â NWS Instruction 10-1801, April 18. https://www.nws.noaa.gov/directives/sym/pd01018001curr. pdf.
OPERATING AREAS 65 compared to relying on the maximum wind and wave criteria listed in the COI, it will also provide a more objective standard for when it is safe to operate a DUKW. Predicting whether a forecasted severe weather event will create conditions that exceed the COIâs permitted values is a difficult task, particularly for DUKW operating personnel who are not weather experts. NWS has recently augmented its severe thunderstorm warnings to indicate the severity of a storm, providing additional information applicable to safe DUKW operations. The three damage threat levelsâbase, considerable, and destructiveâvary by increasing size of hail and/or speed of wind. The definitions of the new damage threat levels are found in Box 4-3.5 Using the NWS alert system would allow USCG to restrict DUKWs from conducting waterborne operations during relevant warnings and advisories, such as a severe thunderstorm warning, tornado warning, high wind warning, small craft advisory, dense fog advisory, or other appro- priate alert. For DUKWs already on the water, the alert system would allow USCG to require DUKWs to immediately proceed to a safe refuge location during specified warnings. To be effective, both the vesselâs crew and land-based personnel would need to have access to the equipment necessary to be informed of severe weather alerts. Land-based personnel would also need to monitor the alert system as part of their routine activi- ties and communicate necessary information to the vessels. All activities designed to ensure safety during severe weather, including using the alert system, should be documented in operating manuals and be incorporated into personnel training. The NWS alert system also issues watches, which provide âadvance notice that conditions are favorable for dangerous weather.â6 USCG could take advantage of the alert systemâs watches to require DUKW operators to modify their routes in anticipation of severe weather. For example, during a severe thunderstorm watch, operating restrictions could instruct a DUKW to follow a water route that allows it to navigate to a safe refuge location within a specified amount of time. The amount of time would depend on the prevailing weather patterns in the vesselâs operating area, such that an area that experiences frequent popup thunderstorms with little advance notice would have a shorter specified amount of time to reach a safe refuge location than an area with more reliably predictable weather patterns. For DUKWs operating on very sheltered or benign waterways that are not significantly impacted by severe weather, it may be appropriate to reduce some or all of these severe weather requirements. 5 NWS, 2021, âNew âDestructiveâ Severe Thunderstorm Warning Category to Trigger Wireless Emergency Alerts on Mobile Phones,â July 22. https://www.weather.gov/news/072221-svr-wea. 6 NOAA Weather Partners, 2021, âFAQ: What Is a Watch,â March 6. https://www.youtube. com/watch?v=x3V3HZBs1Y4.
66 OPTIONS FOR IMPROVING THE SAFETY OF DUKW TYPE AMPHIBIOUS VESSELS In addition to its commitment to education and outreach, NWS has worked with USCG in some areas of the country to provide decision sup- port tools to help mariners and USCG officials make risk-based decisions regarding maritime operations. There is an opportunity for OCMIs who oversee DUKW operations to consult with their local NWS office on devel- oping operating restrictions and decision support guides. SUMMARY Under Subchapter T, OCMIs must exercise their professional judgment when defining the bodies of water and setting operating restrictions. Although there is a great deal of variability between waterways under USCG jurisdiction, the committee believes that it is feasible to develop a consistent set of standards for evaluating which bodies of water or portions thereof are suitable for the safe operation of a particular type of DUKW. Developing this consisted set of evaluation standards would require con- sidering the following factors: ⢠Vessel traffic, including commercial, pleasure, or government vessels ⢠Physical dimensions of the waterway (e.g., fetch) ⢠Depth of the water (i.e., is the water deep enough to fully submerge the DUKW?) ⢠Constraints on the waterway such as speed limits or horsepower limitations ⢠Waterway entry to and exit points for the DUKW BOX 4-3 National Weather Serviceâs Definitions of Types of Severe Thunderstorm Warnings Destructive damage threat is at least 2.75-inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. Warnings will automatically activate a Wire- less Emergency Alert (WEA) on smartphones within the warned area. Considerable damage threat is at least 1.75-inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. Warnings will not activate a WEA. Baseline or âbaseâ severe thunderstorm warning is 1.00-inch (quarter-sized) hail and/or 58 mph thunderstorm winds. Warnings will not activate a WEA. SOURCE: https://www.weather.gov/news/072221-svr-wea.
OPERATING AREAS 67 ⢠Proximity to available rescue craft ⢠Availability of safe refuge locations (see Box 4-2 above) For severe weather, incorporating the alert system run by NWS into DUKW operating restrictions is a means to reduce the risk that DUKW operators will misjudge the severity of the weather or capabilities of their craft. Such an effort would likely require USCG to consult with local NWS offices.