The point in Port Allen where the Gulf Intracoastal Waterway meets the Mississippi River is arguably one of the most crucial water transportation choke points in America.
The Mississippi is the busiest waterway in the country — its lower section carries more than 300 million tons of cargo each year — and the Intracoastal is the third-busiest, according to the U.S. Corps of Engineers. Every day, grains, soy, chemicals, oil and other crucial staples the country depends on drift along on both.
The problem? One waterway is higher than the other — sometimes by about 40 feet, though it varies widely.
“The river is God-made, and the canal is man-made,” says Anthony Dents, a lock operator at Port Allen Lock. “The canal depth won’t change much, but the river will.”
Enter the Port Allen Lock.
The northernmost point at which barges can pass between the two waterways, the "water elevator" saves vessels a trip of about 160 miles, said Adam McFarlan, who oversees the lock's operations.
“If they couldn’t use it, they would have to go all the way to New Orleans and use the Algiers lock,” he said.
Every year, about 32,000 vessels haul about 25 million tons of cargo through the "water elevator" connecting the two bodies.
On Thursday, the Mississippi was about 4 feet higher than the Intracoastal. It was Dents' job to make up the difference.
When a boat wants to go from the higher river into the lower canal, the gates are shut and the lock is filled using a series of tunnels and valves. Once it is up to the river level, one gate opens and boat is let inside.
The gate closes, the water is let out until it reaches the canal level, then the other the other gate opens and the boat proceeds on its journey.
The process takes about 20 minutes, though it can vary depending on the water levels.
Dents and other operators work 12-hour shifts where they man a control room and coordinate with incoming boats.
"It doesn’t seem that interesting, but there are a lot of working parts," Dents says. "We walk boats in, maintain safety of the deck crew, and determine how many boats can come through at a time."
The lock can fit a boat that is 1,250 feet long and 80 feet wide, or multiple smaller boats using tug boats. The average boat length at the Port Allen Lock is 600 to 900 feet.
As boats pass through the lock, Dents records their times on a computer. He can also track incoming boats using VesselFinder, through another USACE-specific system, and on a closed-circuit camera.
On average, a locking occurs once every hour and a half, or about 6,000 times per year.
Bayou Plaquemine has been a commercial transport route since the 1700s, linking the Mississippi River with the Atchafalaya, Red and other rivers. A lock was built at Plaquemine in 1909.
After heavy traffic during World War II, the the Gulf Intracoastal Waterway was expanded to increase capacity. It links deep-water ports, rivers and other waterways from the Mexican border to Apalachicola, Florida. After 30 years of building, the “water interstate highway” was completed in 1949.
“It gave industry access from the Mississippi to the Gulf,” McFarlan says. “Barges could go places they couldn’t before.”
Today, the Intracoastal carries about 16% of the country’s total internal waterway tonnage, according to the Corps, including about three-quarters of the nation’s refined petroleum and petrochemical products. The GIWW is estimated to save shippers about $3 billion per year.
The Louisiana portion of the GIWW has the most traffic, carrying $75 billion worth of freight each year.
As the waterway was being completed, work started on the Port Allen Lock, which was finished in 1961 for about $13.9 million. It was built by the Corps, which still operates and maintains it. While the basic mechanisms haven’t changed, computerized control panels were implemented in 2009.
Aside from assisting barge traffic, the lock also helps prevent flooding of low-lying areas to the southwest of the lock, and diverts Mississippi River water through the structure to improve water quality of the Intracoastal.
One reason the lock is so important for the economy is that barge traffic is significantly more cost efficient than other forms of transportation, Corps officials say. One gallon of fuel can carry 1 ton of cargo 155 miles by truck, 413 miles by rail, or 514 miles by barge.
One barge of liquid cargo equals 46 rail cars or 144 trucks.
The Corps says using waterways cuts down on congestion and traffic accidents, keeps hazardous cargo away from populated areas, and reduces greenhouse gas emissions. A truck emits 71.61 greenhouse gasses per million-ton miles, a railroad car 26.88 tons, and a barge 19.27 tons, according to the Corps.
Like any machinery, the lock sometimes needs maintenance.
“Every now and then we have to change out the gates because of erosion,” McFarlan says. “But if we shut down for a month it costs industry a lot of money.”
The lock runs 24 hours a day, 365 days a year.
Safety is a big part of Dents’ job.
“If a boat is in motion, there are only certain places deck hands can walk. They can never be on the sides,” he says. “We try and talk to them, radio to them and make sure they’re always being safe.”
The lock is equipped with large steel boxes called crush blocks that can be lodged between a boat and the lock to stop someone from being crushed if they fall in the water. So far they have never been used at the Port Allen Lock.
“We hope we never have to use them,” Dents says.
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