Upstream and Downstream Threats: Firefighting Operations

Upstream and Downstream Threats

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The best way to prepare your team to be successful for any dive operation is through risk/benefit analysis and continuing education taught by an accredited public safety agency. (Photo by Eric Strohacker.)

As winter wears off, we all look forward to Spring warming things up. However, it also comes with the price of the thawing and potential flooding, providing a dangerous time for some public safety dive teams that have experienced three to four months of downtime with very little exposure to open water operations. Winter months are the perfect time to reevaluate your team’s operational needs and improvements as well as focus on equipment standardization, gear maintenance programs, diver “lifesaving skills” evaluations, and annual swim testing to be ready for the busy season ahead. As we all say in special operations, “If you don’t use it, you lose it!”

Training Review

Continuing education during the winter months can be challenging and should consist of both in-water pool sessions and current diving classroom reviews and hands-on skill sets. In this case, pool sessions can be just as valuable as open-water training to prepare your divers in a controlled environment to work on entanglement drills, obstacle courses, and skill sets. I cannot stress enough that not all dive equipment is made for cold or current diving use. Check with your dive gear manufacturer and manual to ensure proper application and its uses.

Diving in Current

With the Spring thaw comes the potential flooding of areas not commonly associated with our bread-and-butter diving operations. These areas can be a challenge with seen and unseen hazards both up and downstream. Remember, your diver is tethered on a line in current, which is a very dangerous thing if done incorrectly.

Teams are strongly encouraged to educate divers through an accredited certifying agency that teaches current diving prior to any in-water operations. Studies have shown that a well-conditioned diver can make very little headway in a one knot current (one knot =1.150779 mph). Anything over one knot impedes the diver’s forward progress and discontinues a thorough search pattern. Diving with the use of movable control points can be an option if done correctly. However, current poses a great danger for entanglement issues, and the forces of the water can dislodge dive gear. Risk vs. benefit and ongoing assessments should be a priority in every situation pertaining to current diving.

Calculating Current

It is important that your team can properly evaluate water speed prior to starting diving operations. Use Chart 1 to evaluate water speed in a 100-foot area by throwing a floating object in the center and timing it to the 100-foot mark. Anything over the one knot mark may not be suitable for diving.

Water Dynamics

Knowing the basics of water dynamics plays a large part in current diving. Water dynamics consist of the Laminar flow or layers of moving water that are slower on the bottom and along the banks because of increased friction with faster water toward the top center, midstream, and on the outside of bends. This is important for the divers to understand as they make their ascent/descent because the forces of the water could change drastically.

The second is Helical flow or the circular flow of water along the banks caused by friction of the current, debris, and materials along the bank. This can be a problem area for divers exiting the water as it tends to wash up debris and can force the diver back into midstream.

Your divers are most vulnerable in moving water situations because velocity and force play a very important role. For example: The velocity of water at three miles per hour will have the force of 16.80 lbf. on your legs, 33.60 lbf. on your body, and 168.00 lbf. on a swamped boat. As the velocity doubles, the forces quadruple, making it impossible to stand or swim. Pay attention to the rise or fall of the water, as the force and velocity can change quickly during flooding and you may have to change your operational approach. To better understand these key elements for safer diving, enroll your team in an accredited and certified course taught by a public safety diving agency.

Safe Diving

The ultimate goal for any dive operation is to remain safe and go home at the end of each shift. The best way to prepare your team to be successful for any dive operation is through risk/benefit analysis and continuing education taught by an accredited public safety agency.

Current Issue

April 2017
Volume 12, Issue 4
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Pennwell