We Dewatered a Lock in January. Here Is What Was Down There
By Ray Whitfield, ADCI-certified commercial dive supervisor. Reviewed by Dana Whitcombe, technical reviewer.
Cathodic Protection & Anodes | Offshore & Subsea Diving January 19, the thermometer on the crane arm read 17°F. The Ohio River was carrying ice chunks the size of truck tires, and Lock 52's miter gate had taken a hit. The lockmaster looked at the gap around the portal plate and said: 'We've got to pull the water. You've got four days.' Dewatering a lock in summer is a chore—you pump it down, chip the mud, fix the seals, and go home. In January, it's a physics experiment. The river water stays around 38°F, which is warm enough to keep the concrete from cracking. But the steel gates, trunnion arms, and anchor bolts shrink. Clearances that passed inspection in September don't exist in January. I didn't figure that out until the first gate had already been set.
Why January Matters
The pumps themselves freeze. We run three 12-inch submersible pumps off a rented barge. If the discharge hose ices over, you've got a wall of water sitting behind a frozen line. So we wrap the hoses in heat tape and put a crew member on the barge whose only job is to watch the ice. The chamber holds millions of gallons, so the drain-down takes the better part of a shift. The lock's own valve system does most of the work; we only use the pumps for the last fifteen feet. Still, you are never dry. The sump well is at the bottom, and if that sump freezes before you get the pumps off, you are in the water business. There is also the smell. Cold mud is not as bad as summer mud, but it carries a whiff of diesel and pipe wax and old fish. You know it the minute you climb down the ladder.
The Five Down There
Once you can stand on the floor, you see it all. The mud is eight inches deep in spots, and the silt makes a sucking noise around your boots. We had been told to do a 'targeted cleanout' to inspect the miter gate track. Five things were worth writing down.
- A nine-foot white oak timber, water-logged and gouged, wedged against the gate track. It had marks like somebody had chopped it with a chainsaw, but it was pulled loose from a barge's headlog. If a closing gate hit it, the gate would ride up and out of its sill.
- A canvas tool bag, two feet long, the kind that snaps to a lineman's belt. Inside was a 36-inch pipe wrench and a rusted claw hammer. It had been down there at least a decade. Tools do not belong in a chamber; a pipe wrench can lodge in a culvert valve seat and prevent a gate from seating.
- A string of three tire fenders, tied to cleats with old mooring line. Tires are the cheapest cushion in the trade, but under water they break down into rubber crumbs that clog pressure-relief valves. We pulled them so we could inspect the concrete behind them for spalls.
- A broken chain-sling hook, two inches across, with a short length of chain. If it got drawn into a pump intake, it could score an impeller or jam a gate. We spent an hour looking for the rest of the chain and found nothing. That hook was a reminder that somewhere, a rigger should have cut the tag off a sling before it went in the water.
- A steel plate the size of a shoebox, welded to the wall with three beads that looked like bird droppings. It had no record in the lock's file—no purchase order, no drawing number. It was covering a vent that should have been open for the gate's balance system. Whoever put it there was trying to fix a leak and didn't know they'd made a check valve obsolete.
What We Did About It
The timber came out with a come-along; the silt suction was stronger than anyone expected. The tool bag went into a scrap bucket—someone probably is still missing that pipe wrench. The tires were cut free and sent up to be recycled, and we found two spalls behind them, each about the size of a dinner plate, which we patched the next day. The chain hook was logged, tagged, and put in the warehouse rack with a note: no chain found. The steel plate we cut out with an angle grinder, then rebuilt the vent opening to spec and installed a proper slide valve. That took the rest of the first day. The inspections themselves were mostly good news. The miter gate track was true, and the concrete sill had no cracks beyond the spalls. But we also found a hairline crack in the sill around one anchor bolt. It's a common winter thing—thermal cycling. We drilled a stop hole at each end and epoxied the crack, then finished the day by torquing the anchor bolts to a new spec that the engineer had sent over. He wanted them a half-turn looser than the summer spec, because the steel contracts in January.
Cold-Weather Lessons
Dewatering in January teaches you to respect viscosity. The rubber seals on the miter gates come out of storage like a slab of bacon. You have to warm them with a torpedo heater before they'll slide into the groove. The anchor bolts tighten differently—add a quarter turn? No, the engineer said back off half a turn, and he was right. A bolt that feels snug at 15°F is too tight when the steel expands in July. That's why you don't torque by feel. And the concrete: if you're patching, the mix water freezes if the air is below 40°F. You have to use low-heat cement with an accelerating admixture, and you have to keep the patch under a tarp with a heat source for at least a day. Not glamorous. But it's the difference between a four-day job and a six-week job. Also, the paperwork. Every item that comes out of a dewatered lock has to be logged—it's evidence, sometimes, of what went wrong in the past. The steel plate with the bad welds was photographed, tagged, and given to the lockmaster to send up to the district office. That's not bureaucracy. That's how you find out which prior contractor mailed it in.
Frequently Asked Questions
What happens to the fish and other aquatic life in the lock chamber when you dewater it? It's a standard part of the job. The lock operator notifies the state agency, and we walk the puddles with nets, putting the fish that didn't slip through the drains into buckets. We then lift them over the gallery and release them into the river above the upstream gate. It takes an hour or two, and it's not fun when the water is 35°F, but it's part of being permitted. Can you do this in the middle of winter? Why not wait for spring? You do it when you have to. If a miter gate is damaged, the lock is out of service anyway, and in the ice season there's usually less commercial traffic, so the closure costs less. But the cold makes the whole operation harder. You have to fight frozen pumps, rigid seals, and concrete that won't cure properly without heated enclosures. We had four days to return the chamber to service, so we could not wait for spring. How much does a dewatering job like this cost? I can't give you a specific number, because it depends on the scope. Dewatering work is typically priced per day for the pump barge, per man-hour for the crew, and per pound for the waste you haul out. The lock also has fixed costs like the pump rental and the environmental monitor. Every job is bid separately.