Repairing a massive lock and dam in sub-freezing temperatures: life during winter at Lower St. Anthony Falls
At 400 feet long and 56 feet wide, the Lower St. Anthony Falls lock can hold 4.2 million gallons of water -- but not until later this month.
Every 15 to 20 years, the lock and dam, which sits close to the I-35W bridge downriver from the Stone Arch Bridge, is dewatered. Once dry -- or almost dry, since inevitable leaks leave half-foot-thick ice on the lock's floor -- crews make repairs on the 45-foot vertical concrete lock chamber walls. They fix massive moving parts such as miter gates, tainter valve guides and staff gauges.
Repairs will be completed later this month, in time for navigation season. Last year, more than 3,000 vessels and 2 million tons of cargo avoided St. Anthony Falls with the lock's assistance.
This is St. Anthony Lockmaster Tim Meers' third dewatering. The Army Corps of Engineers operates the lock, but like most who actually work on locks and dams, Meers is not an engineer but an all-around handyman. He found work at the lock as a temporary laborer in 1975 after returning from the Vietnam War. He's been at the lock ever since, working his way up to permanent mechanic and eventually lockmaster in October 2001.
Meers replaced Joe Dvorak (pictured on cover) when Dvorak moved on to regional supervisor. Now Dvorak oversees some 10 locks and dams from Upper St. Anthony Falls (the lock closer to the Stone Arch Bridge) to Guttenberg, Iowa. A returning Vietnam vet himself, Dvorak started as a temp in the lock and dam system in 1972 after hearing about an opening while standing in the unemployment line. Now retirement is just "two years and a week" away -- not that he's counting.
Dvorak and Meers know this lock at mile 853.9 of the Mississippi River and could describe the function of its seemingly infinite joints and joists in their sleep. But on a layman's level, the Lower St. Anthony lock is basically a concrete chamber that is filled or drained of water to elevate or lower a vessel back into the river. Without the lock, ships would face a vessel-crunching 10-to 25-foot drop though the lower falls.
The chamber can fill with water as fast as eight minutes, but usually the crew takes 15 to 20 minutes, "just to keep things safe," says Meers.
Dewatering began in December; repair and maintenance work in Minnesota takes place in the off-season, which is winter. First, divers scout around in the freezing water to help pinpoint and diagnose problem areas. Meers was a diver in the '80s, helping do the underwater diagnostics for dewaterings. "Now, I leave it to the younger guys," he says.
Many of the younger guys working on the lock's concrete vertical walls live in Wisconsin. The laborers, who work for Wisconsin-based Norcon Corp., don their coveralls, steel-toed boots, massive gloves and hard hats and put in an eight-hour shift in the freezing Minnesota winter. Standing on scissorjacks (a sort of automated scaffolding), they chip out crumbly concrete, insert pegs and forms into the incisions, then fill them with concrete. After filling the lock's wounds, workers use insulated blankets to keep the new concrete warm in below-freezing temperatures during its 48-hour curing process.
An Army Corps repair crew takes care of the more sophisticated parts. They repair or replace the miter gates, tainter valve guides and staff gauges. The two tainter valves open and close to allow water into or out of the tunnel next to the chamber. The miter gates open to allow water in from the tunnel, then seal the chamber after the staff gauges indicate the appropriate level of water has been reached.
Of the 3,227 vessels that went through the lock last year, 1,241 were commercial, 1,511 were recreational and 475 were considered "other" -- including government watercraft. Dealing with commercial and government watercraft is fairly straightforward, but the pleasure boaters can get a little squirrelly.
Meers fondly recalls helping secure and coordinate 200 canoes passing through the lock at the same time last year. Hundreds of canoeists had to work together, holding each other's leads -- ropes that tethered them safely to the lock chamber walls. But canoeists, says Meers, are a mellow bunch to deal with.
Dvorak says people in pricier speedboats have a less collegial temperament. Crews usually wait until there's more than one recreational boat in the lock before moving 4.2 million gallons of water. Sometimes the boaters aren't in the mood to wait, and get a little argumentative. Even when other boats arrive, workers have to be wary to keep everyone apart, lest a million-dollar boat gets nicked by a $10,000 vessel. Then, when the lock has all the boats in it and crews start raising water levels, the more enthusiastic (or inebriated) boaters jump into the lock water for a swim.
Meers and Dvorak appear too bemused to muster looks of disapproval for the boaters' antics. It's all a matter of perspective, and they've seen much worse along this patch of the river. With every spring thaw, three to five bodies bubble up through the ice, mostly suicides. While some come from up north, Dvorak says, "The University is notorious for kids being gone a few weeks then turning up in the river in the spring."
Coast Guard lifeboats get called out four or five times a year for rescue attempts, mostly for suicidal jumpers. A year or so ago, Dvorak happened to witness a man jumping from the I-35W bridge. The Coast Guard got to him in time and, Dvorak says, "Turns out they knew him by name. They said. 'Steve, this is the third time we've had to come get you. When are you going to quit this shit?'"
About six months later, 'Steve' showed up near Lower St. Anthony, having made his fourth and final jump.
The tone around the conference and coffee table perks up when Meers recalls the deer they tried to save last winter. "It was trying to climb the wall to get out of the water," he says, mouth downturned, eyebrows lifted. The Corps crew managed to get the deer in a crane sling and hoist it out of the water in time for the DNR arrival.
"Unfortunately, they had to give it a tranquilizer, and that killed it," says Meers, looking wistfully at the photo of the deer in a crane sling on the bulletin board.
Meers looks out the window to see if he can spot the pair of bald eagles that frequent this stretch of the river. He says the falcons and other birds have been on the rise as well. A circle of bread and seed sits on the ice near the upper gate of the lock. "The guys like to feed the ducks," he says.
Dvorak remembers the days before the Clean Water Act was implemented, when the river was too dirty for even the birds. But last year, he says, "We didn't even have one spill from Downtown." Sewers and drains in Downtown flow straight into the river, so the Corps is the first environmental line of defense after a spill. However, a Congressional bill could change this, at least in part, by allowing the Department of Defense (the Army Corps' parent) to disregard all environmental laws.
At the state level, efforts are underway to create a whitewater rafting recreation area on the other side of the river, near the 3rd Avenue Bridge. "We don't have any say over that," says Dvorak, pursing his lips and looking heavenward as if someone suggested making the Basilica into a theme park.
Luckily, at least for him, the whitewater efforts have little hope of money during this year's deficit-plagued legislative session. If funding does go through, it'll be after Dvorak retires, when he plans to rededicate his life to building Habitat for Humanity houses. The one thing that will happen before then is the Upper St. Anthony lock and dam's dewatering. He leans back in his chair, takes a sip of his tea in his Styrofoam cup, and says, "Same thing -- twice as deep."