Diving the Mississippi: Current, Visibility and Barge Traffic

By Ray Whitfield, ADCI-certified commercial dive supervisor. Reviewed by Amanda McCallister, editor.

Underwater Inspection | Commercial Diving Contractors Alabama Last spring I was hanging a piezometer on a bridge pier just north of Alton, Illinois, when a 15-barge tow came around the bend a quarter-mile out. The current was running about 6 knots on a 20-foot stage, and we had a 45-minute window to set three pins before the tow passed. We pulled the diver and sat on the deck drinking coffee for an hour. That's the Mississippi for you. We do a lot of work on this river. Bridges, water intakes, pipeline crossings, lock and dam inspections. Sometimes it's green, sometimes it's gray, but it's always moving. I'm an ADCI-certified dive supervisor, 28 years on inland and industrial jobs. I've been in tanks, tailraces, culverts, and once a flooded boiler. But the Mississippi is the one that teaches you to respect the water. The river decides when you work. You can't schedule around it. So before I put a diver in the water, I check three things: current, visibility, and barge traffic. Here's what that means in practice.

The Current Is Everything

Current is the big one. It changes with the stage, and the stage changes with the rain up north. At normal summer stage near St. Louis, you're looking at 2.5 to 3.5 knots. During a flood, 6 to 7 knots, give or take. That doesn't sound like much until you're at the end of a 200-foot umbilical with a 60-pound helmet. We use the river's energy, but we never fight it. You plan moves from the surface, set your tenders accordingly, and always have a quick-release on the line. On a recent job at the Chain of Rocks Canal, we aborted twice because the current spiked at 4.5 knots. That's our cutoff for a diver on a light umbilical. We could have rigged more weight, but then the risk goes up. Call it a judgment call. Depends on the plant, honestly. The technique is to work with the current. You position the diver upstream and let the river carry him down to the work area. You run a downline and a tagline. Sometimes we use a 1,000-pound sled anchor to hold position. On one job, we even set a temporary cofferdam upstream to slow the flow to a walk. That's expensive, so it only happens on critical work. Most times you just accept the flow and plan shorter dives.

Visibility: Zero Is a Number

Visibility is the next thing. The Mississippi is silty, and most of the time you can't see your glove. Underwater, it's total blackness. We work by touch and, if needed, a sonar. We use a Marine Sonic imaging system, but it's rare we get a clean scan in the mud. So we rely on divers who know the structure. In 2009, I was diving on the Eads Bridge pier and spent 45 minutes feeling for a seam on a caisson. I had to come up because my umbilical got wrapped on a rebar. That's how it goes. We train new divers to do mock-ups with their eyes closed. If you can't do it blind, you can't do it in the Mississippi. There are days when visibility is a foot or two, usually in late winter when the river runs low and clear. Then you get to see what you're actually touching. That's a treat. But we never depend on it. Our tooling is all about minimum access. We use an SRT, a sleeved rotary tool with a camera, but you're driving by feel anyway. The camera is for the inspector on the surface, not for us. You learn to read rust and silt through your gloves.

Barge Traffic: Timing and Coordination

Barge traffic is the third rail. The river is a highway, and we are a pothole. We coordinate with the U.S. Coast Guard and the towing companies to set work windows. You might get two or three windows of 45 minutes each per shift. That's enough to cut and weld two bolts, maybe. On bigger jobs, we use an A-frame and a barge of our own to block a lane. But that requires notices, permits, and a pile of liability. Once, a tow cut across our work site — a misunderstanding between the pilot and a deckhand. We had divers down. That's the moment you earn your pay. I gave a direct order to surface, and I personally called the captain to chew him out. But you have to be respectful. They're on a schedule too. You learn the patterns. The Melvin Price Locks at Alton, the Chain of Rocks, they all have schedules. We plan around them. You cannot be under a 1,200-foot tow string. If you get caught, it's your fault. Speaking of tows, one time while we were waiting for a lock to cycle, we saw a deer swimming across the river. That takes your mind off the fear. We watched it for ten minutes until it hit the bank, shook its tail, and disappeared into the brush. Then we went back to work.

The Gear That Works

Equipment on the river is a mix of hard-won wisdom and commercial-grade gear. We use Kirby Morgan 37 helmets with hard-wire comms. No full-face masks for no-viz work. The comms are your lifeline. You better have a good intercom. We use a Miller 400 welder for salvage and repair, but only in specific conditions. The divers wear a DUI drysuit in winter and a wetsuit in summer. Water temp matters. In April it's 50 degrees; in August it's 80. But the cold is not the killer — the current is. And the mud. We wash the diver off every time he surfaces with a fire hose. The silt gets everywhere. We run all our operations off a dive barge, tethered to the bank. We use a compressor manifold and a 5/8-inch umbilical, with a diver-down flag on the bow. The flag is required, but towboats don't always see it. So we also use a radar beacon. On a big job, we have a spare diver suit and a standby diver in the water, per ADCI. You really cannot take shortcuts on the river. I've seen what happens when you do.

Frequently Asked Questions

How fast is the current on the Mississippi? It varies with stage and location. In normal summer near St. Louis, it's 2.5 to 3.5 knots. In flood, you can see 6 to 7 knots. We set a hard cutoff at 4.5 knots for a diver on a light umbilical. Can you see anything underwater? Almost never. The river is silty, so visibility is typically zero. On rare low-water days, you might get a foot or two. We work by touch and use sonar as a reference, but don't count on it. How do you work around barge traffic? We set work windows with the Coast Guard and tow companies. We have a standby diver and a radar beacon on the barge. When a tow comes through, we clear the water until it passes. No exceptions. What's the best time of year to dive the Mississippi? Fall gives you stable water, moderate current, and lighter barge traffic. Late winter can be low and clear but cold. Summer is busy and high. It all depends on the stage.