By Sean Sheldrake and Alan Humphrey
Our previous blog posts have featured how EPA diving scientists support cleanups in the nation’s waterways. In this post, we talk about different ways in which we might dive to carry out EPA’s mission.
What is SCUBA?
Self-contained Underwater Breathing Apparatus, or “SCUBA,” is the mode of choice for many diving scientists, and many diving scientists at EPA. It involves carrying your entire breathing supply with you, and requires a fair amount of strategic planning, especially for difficult diving conditions such as low visibility, and cold or polluted water.
What is surface supplied diving?
Is that a trick question? Well no, it is what it sounds like—air is provided to the diver from above through a long hose. This can be quite limiting if you want to swim far from the boat, so it doesn’t work everywhere. Also, the dive vessel must be anchored to keep it from moving. If the vessel was moving, the diver working on the seafloor could become the boat’s anchor after drifting into a rock. Now that’s a bad day at the “office”!
Even though this kind of “dope on a rope” diving may feel restricting to the diver, it can be crucial in low visibility, contaminated water. Often times—especially where visibility is only a few inches—it can be difficult or impossible to keep track of your dive buddy.
I’ve been diving in the Willamette River in conditions where I’ve been close enough to hear my dive buddy’s breath, but we couldn’t see each other. In conditions like that, we might not be able to find each other in case of trouble. And even more basic than that, divers can’t check vital gauges such as pressure and air supply under such conditions. In those cases, surface supply is the way to go. Topside support can be your ‘buddy’!
Don’t hold your breath!
With a surface supplied diving system there is plenty of air to keep the diver working. That means no cutting dives short before the scientific mission on the bottom is completed, or needing to account for an air supply that includes keeping the diver completely sealed in for an extended decontamination process, like when they might be covered with oil (see picture). Surface supply offers more efficiency and safety for the diver for certain projects—in most cases the diver can continue to work until the sampling or other task is completed (or when nature calls).
Want to learn more? Download the EPA publication “Use of Surface-Supplied Gas for Scientific Diving” presented at the 30th symposium of the American Academy of Underwater Sciences: http://1.usa.gov/ZPxS6b.
Read more about the latest in EPA scientific diving at facebook.com/EPADivers.
About the authors: Sean Sheldrake and Alan Humphrey both serve on the EPA diving safety board, responsible for setting EPA diving policy requirements. In addition, they both work to share contaminated water diving expertise with first responders and others.