The Bonneville Dam navigation lock will return to service at 10 a.m. Sept. 30, according to the Portland District of the U.S. Army Corps of Engineers.

A sill on the lock was found to be cracked, causing it to leak as barges and other vessels transited the dam. The Corps shut down the lock, blocking all river traffic.

Barge and elevator operators rely on the Columbia River to transport millions of bushels of wheat to market.

“It’s important to recognize the patience from our Columbia River users, who depend on this critical piece of infrastructure to run their businesses,” said Col. Aaron Dorf, Portland District commander for the Corps. “Between now and Sept. 30, our teams will be working around-the-clock to construct the new sill to restore Columbia River traffic.”

“One nice thing is we’re 95% done harvesting, so I think we’ve all put the crop away,” said Damon Filan, manager of Tri-Cities Grain and a member of the Washington Grain Commission.

Fourteen commercial vessels are impacted by the lock closure, according to the U.S. Coast Guard’s Columbia River Waterways Management Division — seven from Tidewater Barge, four from Shaver Transportation and three from American Cruise Line.

Shaver Transportation operates a fleet of 20 grain barges between Lewiston, Idaho, and export terminals on the lower Columbia River.

“This, of course, is a busy time of year post-harvest,” Rob Rich, vice president of marine services at Shaver, said.

Three Shaver barge tows are above Bonneville Dam 40 miles upstream from Portland and waiting to go through the locks. Ten barges are loaded. They are tied off at the Fort Raines barge storage area above Bonneville Dam, awaiting transit through the locks when they reopen, Rich said.

“All that wheat is going to move” despite the delay, Rich said.

The barges are closed-hatch and weather is moderate, so Rich doesn’t expect the delay to harm the grain.

“It is not uncommon for wheat to be in barges three or four weeks or more,” he said. “There isn’t a concern about quality degradation.”

Wheat exports have been relatively slow due to trade wars and global competition, Filan said.

Overseas customers tend to purchase wheat several months out, he said.

“If it was a very long-term deal, then we’d have some challenges, because I’m not sure the rail could handle the demand,” he said.

Railroad tracks line the river gorge, but they have much smaller capacity than barges. A four-barge tow carries 480,000 bushels of wheat, roughly the equivalent of 120 to 130 rail cars, Filan said.

About $2 billion in commercial cargo travels the entire system annually, according to the Corps. It’s the No. 1 export gateway in the U.S. for wheat and barley and the No. 2 export gateway for corn.

Navigation locks allow the large barges to pass through the massive concrete dams that were built across the Columbia and Snake rivers decades ago to generate hydroelectricity for the U.S. West.

A boat enters a sealed chamber filled with water — essentially like a giant concrete bathtub — and then the water level is lowered or raised to match the level of the river on the other side of the dam. Then the lock opens on the other side and the boat exits.

The concrete sill that is cracked in the Bonneville Dam is similar to a rubber threshold on the bottom of a door. Just as that rubber strip creates a seal to keep cold air and moisture from leaking in under the door, the concrete sill meets up with the lock’s gate and creates a seal to keep water in the lock.

The cracked concrete is on the downstream lock gate, but the damage was causing significant leaking in the whole system — so much so that water levels were falling when the lock was in operation, said Chris Gaylord, a spokesman for the Corps.