VICKSBURG, Miss. — Massive helpings of “gumbo” -- as the gray gunk that blankets the bottom of the Mississippi River is known – are on the menu for the Dredge Hurley as it works its way across a shallow reach of river near Helena, Ark. We are on board this massive ingesting machine on Day 9 of our trip down the river, learning the rudiments of river housekeeping and getting a first-hand look at one of the workhorses the U.S. Army Corps of Engineers uses to keep the crucial shipping channel open for business.
The Hurley typically operates 24 hours a day, seven days a week from June to November, seeking out shallow spots in a 355-mile stretch of river to maintain the congressionally mandated 9-foot deep, 30-foot wide shipping channel when the river is at its average historical low point. The vessel can stay out as long as the water level is low enough to allow for dredging, as it travels with its own fuel barge and has all the accoutrements for life at sea, including a fully equipped kitchen, sleeping quarters used on a rotating basis by the 30 to 35 people on board, and an on-board wastewater treatment plant.
The dredge looks like a cross between a boat and an oil platform as we first catch sight of it from the tender sent to pick us up from a nearby harbor.
The Hurley is 300 feet long, 58 feet wide, has five decks above its main deck and a forward section festooned with winches, cranes and the superstructure for its suction head. It also has a 1,000-foot pipe extending from its starboard side that is spewing a torrent of light-brown water into the shallows, where it makes a splashy entrance after encountering a deflection plate as it exits the pipe.
We get a look at the ship’s most unusual piece of equipment shortly after boarding.
Acting on a twirling hand signal from the dredge’s captain, Rick Niday, the dredge operator shuts down the suction head and hoists it from the water. Moments later we are staring at a 35-foot wide piece of machinery that -- if you ignore the water coursing off it and the logs caught in its jaws – closely resembles a giant Hoover vacuum cleaner head.
“The main difference between the two is that this one doesn’t have a bag,” said Niday, a rawboned 47-year-old from Collierville, Tenn.
Gulping gumbo and cannonballs
The Hurley’s vacuum also has a bit more power than your typical home carpet cleaner – generated by a massive pump capable of inhaling 68,300 gallons of water or 8,000 cubic yards of gumbo, or slurry as the mixture of sand and clay is officially known, every minute.
You can hear just how powerful it is by standing next to the discharge pipe and listening as gravel, small logs and other unidentified objects go rattling through. Crew member Amos Henry of Memphis said that another corps dredge once hit a field of Civil War cannonballs, which raised a real racket as they went pinballing through the pipe.
The Hurley crew begins the process of erasing a shallow spot by dropping anchor and then mapping an imaginary “dredge box” on the river’s bottom. The vessel then uses cables to pull itself systematically up and down the box, just as if it were vacuuming a living room rug.
Instead of an agitator to raise the dust, the suction head uses a dozen high-pressure water jets just above its intakes to blast away stubborn crud from the river bottom.
The resemblance to a home-cleaning implement has not gone unnoticed, as the Hurley is one of a class known as dustpan dredges. The corps also uses two other types of dredges on the river -- hopper dredges, which are used to clear the lower channel for seagoing ships, and cutter-dredges, which are used where the river-bottom is firmer.
While dredging can be as tedious as household drudgery, the river is fully capable of tossing an occasional surprise at you.
Niday said the crew has several times had to shut down the pump and then work to dislodge a swimming deer that had gotten caught in the suction-head chamber. The decomposing corpses of cows and pigs that fell in the river and drowned also have occasionally gotten stuck in the lifting cables with odious results, he said.
And dredge equipment operator David Woods remembers the night that the captain of a barge tow that had run aground upriver from the Hurley decided to try and pull his cargo loose in the middle of the night.
Suddenly the 40 barges broke loose and came cart wheeling down the river directly at the dredge.
“It was like playing pinball … ducking and dodging,” he said, explaining that the dredge’s ability to rotate its propellers a full 360 degrees helped him avoid disaster.
While dredging is unquestionably effective, it does have its disadvantages. Since the river initially deposited enough sediment to create a bar there, it is only a matter of time before it rebuilds it.
Environmentalists also argue that dredging severely impacts bottom-dwelling species and affects other river dwellers by increasing turbidity.
“Dredging is not environmentally friendly,” said David Carruth, president of the Arkansas Wildlife Federation. “… It degrades habitat and breeding grounds.”
Carruth said that the deepening of the river is responsible for problems in tributary streams and rivers, causing them to dig deeper where they join the river, and also is believed to be a major factor in the lowering of the aquifer, or water table, in bordering areas.
While not conceding that the program is causing much damage, the corps has been engaged since the 1950s in a massive dike-building and bank-reinforcement program designed to reduce the need for dredging.
The idea is to use the dikes “tickle” and “squeeze” the Mississippi at key points so that it doesn’t slow down enough to drop its sediment load, said Larry Banks, water management chief for the corps’ Mississippi Valley Division.
“Dredging is the last resort,” he said, adding that the 1,500 miles of dikes now in place have substantially reduced the need for vessels like the Hurley to clear the channel.
The dikes have the advantage of creating protected backwaters favored by fish and birds, including the endangered least tern, Banks said. The corps also creates “borrow pits,” water-filled holes created by digging material for levees, which are flushed out during high-water periods and also make for prime habitat for fowl, he said.
While some in the environmental community have charged that the use of the dikes is an attempt to force the river into an unnaturally narrow slot, Banks said the criticism is off the mark.
“We want a river that has diversity, not a ditch conveying water,” he said.
After sharing lunch with Niday and other crew members, we said our good-byes and were transported back to the shore and our waiting van. Minutes later we were again rolling southward, heading for a rendezvous with Civil War history at the Vicksburg (Miss.) National Military Park.
Reporter Mike Brunker and media producer Jim Seida are traveling the length of the Mississippi in August and will be filing daily dispatches along the way. If you have a question or comment, mail us at firstname.lastname@example.org.