Boat Safety

A boat safety story. The following is an actual, real life story, although the outcome could have been tragic, it was not, due to some quick thinking.

Capt Matt
I work for a government agency that has a number of boats on the large rivers. In addition to my scientific duties, I serve as a motorboat operator instructor. This is the first serious accident to occur to any of my trainees. The district safety officer’s assessment (below) very accurately describes this avoidable accident. I never saw the boat in question, or it’s sampling arrangement, however, we did discuss the dangers of using the boom on another, larger, boat (where the boom was mounted centrally). Using boats for research in heavy current, often with debris such as large timber coming downstream, can be a very dangerous activity. More so when you throw in the barges and their wakes. I am always looking for ways to make this operation safer for our crews.

I have deleted the names of the persons on the boat, and of the agency in question. If you like, you may reprint the following for your page. At a minimum, it may keep someone else from dropping an anchor, or something that might become an anchor, off the stern of their boat in heavy current.
At about 2:10 P.M. July 8, 1998 three members of the [government research facility] office in [the Midwest] were involved in a boating accident on the Mississippi River. All three survived, but the boat (17 foot Monark) sank in about 50 feet of water and is considered a total loss. It is hoped that by careful analysis of the factors contributing to this accident and the survival of the three person crew all of us throughout the [agency] will benefit. It is not my intention to find fault or place blame here.

THE ACCIDENT:

In my view the major factors contributing to this accident and its severity are:
(1) location of reel/boom sampling equipment;
(2) the poor trim of the boat as a result of poor weight distribution;
(3) flow velocity;
(4) length of sounding cable versus depth;
(5) inability to cut the sounding cable;
(6) lack of maneuverability once the sampling equipment was fouled; and
(7) unsecured onboard equipment.

Location of reel/boom sampling equipment

There are four possible onboard locations for equipment used to suspend sampling or measuring equipment overboard. This equipment can be mounted to suspend equipment over the bow, over the side, through a well, or over the stern. The least favorable location is over the stern, and over the side at or near the stern is just as bad. With overboard equipment at or near the stern several inherently bad things can happen. The sounding line could become fouled in the engine's). The drag created by the equipment retards steering response. Fouled equipment at this point will result in pulling the boat into a stern-to-the-current orientation with little or no possibility of recovery. Among these, the only thing that didn’t happen here was fouling the sounding cable in the engine's).

Poor trim of the boat as a result of poor weight distribution

Placing the sampling equipment on the same side of the boat as the boat operator ensures that a concentration of weight will be there anytime samples are collected or measurements are made. This is particularly critical on a small boat. In this case, the concentration of weight resulted in the boat listing to starboard during normal operation. At the least this reduced the freeboard (distance between the water-line and the top of the hull at the gunwale), and contributed to sluggish maneuverability and lack of positive control.

Flow velocity

Based on the information provided by crew members during the post accident interviews, the flow velocity at the time of the accident was near 5 fps (feet per second). There is little doubt that the flow velocity is a major factor here. If the submerged object had been fouled in calm water the boat could have been stopped and easily held in place while the equipment was cleared or cut free. In this case, the force of the moving water immediately took over when the engine power was reduced and the boat began to swing downstream exposing the anchored stern to the current.

Length of sounding cable versus depth

The boat is estimated to have sunk in approximately 50 feet of water. If that is the case the length of sounding cable likely exceeded this depth. Through some deductive reasoning plus years of personal experience working from boats in big rivers it is estimated that the wet-line length of the sounding cable may have significantly exceeded the depth when the sampler contacted the submerged object and became fouled. The combined velocity encountered by the sampler and sounding cable would have exceeded 10 fps with the boat moving upstream opposing a 5 fps current. This would result in a large wet line correction necessary for the sampler to reach the bottom during a traverse through the sample vertical. If the bottom topography changed abruptly or large debris were encountered the sampler could easily become fouled.

To protect the safety of boat and crew a boom operator and boat operator must work as a team. There should be cross communication to ensure that the boom operator always knows the depth of flow at the sampled vertical. At the same time the boat operator should be aware of the amount of cable out. Because a boat must always be free to safely maneuver it is not a good practice to sound with cable suspended equipment unless the boat is stationary at anchor or attached to a tagline. If the boat is underway depths should be determined using an acoustical depth sounder unit so the boom operator knows the depth prior to releasing the cable.

Inability to cut the sounding cable

Because it was necessary to release the sounding cable from the reel and allow the boat to float downstream with the force of the current the cable was never stationary relative to the boat. This made it impossible to grip the cable with the cutting device and sever the line. Also, if the cutting device was a pair of side cutters it would have been difficult at best to sever the line even with a stationary cable.

Another problem is where to cut the cable. The best location for use of the cutting tool is near the reel spool behind the idler sheave. This allows the cut to be made in a confined space and gives the best chance to complete the cut with the cable in motion. Also, the energy stored in the cable under tension can be released without leaving a long segment of cable outboard of the boom that could whip back at the boom operator. Another advantage is keeping the boom operator’s weight inboard during the cutting procedure and eliminating the potential for being pulled overboard.

A better alternative cutting device is a pair of cable shears. A variety of tools designed to cut light cable are available on the market. Many of these tools can be used to easily sever light cable with one hand. Also, because these tools cut quickly and cleanly there is a possibility that the cable could be cut even while moving. In practice, however, this is probably much more difficult than it seems.

Some consideration should be given to designing a cable cutter that can be permanently affixed to standard A, B, or E reels. This device must be capable of cutting the cable quickly and cleanly with one smooth single- handed motion. Retrofitting onboard reels with the new breakaway kits available from the Hydrologic Instrumentation Facility is another fail- safe that could have allowed the boat and crew to escape even if the cable could not be cut.

Lack of maneuverability once the sampling equipment was fouled

Except for some specialty designs, boats are steered by directing the thrust of the propulsion system. Because the propulsion is at the stern of the boat the stern will always move first in response to a change at the helm. Therefore, if equipment at the stern is fouled on some stationary object or even a large floating object the steering system is immediately rendered useless no matter how much power is applied. At this point the boat operator has no possibility of maneuvering clear to save the boat and crew. In moving water boat position and bow angle of attack relative to the flow is the difference between being in control and being at the mercy of the river. Clearly this was the case here.

Unsecured onboard equipment

The fact that the boat operator was hit by a shifting tool box during the capsize illustrates that at least some heavy equipment was not secured in place. This could easily have been the difference between survival and disaster if he had been rendered unconscious.

All items placed onboard any boat should be considered movable ballast and as such must be firmly secured in place. If heavy unsecured items shift unexpectedly while underway they may cause injury or could severely effect the boats trim.

SURVIVAL:

The primary factors contributing to the survival of the three crew members are:
(1) personal flotation devices;
(2) certification as boat operators;
(3) relatively warm water temperature; and
(4) luck.

Personal flotation devices

First and foremost the fact that all crew members were wearing personal flotation devices saved their lives. Not only were they able to float free of the sinking vessel, they were able to stay afloat as the current carried them downstream while they attempted to swim to shore. Without personal flotation it is unlikely that all would have survived the ordeal.

Certification as boat operators

Both the boat operator and boom operator were certified boat operators under the Department of the Interior’s training policy. Both received operator certification training in May 1997. There is little doubt that this training contributed in some measure to the crew’s survival.

Relatively warm water temperature

Even though the actual water temperature at the time of the accident is unknown, typical summertime water temperatures associated with seasonably warmer air temperatures helped improve survivability. The crew estimated they were in the water 45 plus minutes, and floated about 2 miles down- stream.

If this accident had occurred during the winter months hypothermia would have certainly played a major role and could have claimed some or all of these crew members. The 50/50 rule states that an unprotected person in water less than or equal to 50 degrees Fahrenheit has a 50 percent chance of surviving for 50 minutes. In this case they would have been pushing their limits in colder water.

Luck

In any situation like this luck can play a major part in survival or disaster. This is no exception. There was no small measure of luck here particularly in the case of one employee who had to escape the confines of the submerged pilothouse as the boat sank.