PORT HUDSON — The contractor flipped down his protective mask and set off a shower of sparks as he welded a seam across a long pipe set up in a pasture along the highway near here.

The people in cars and trucks zipping past on U.S. 61 as the scene unfolded last week likely had little idea of the significance of what was taking place. The welding being done under the shade of sun umbrellas was a sign work on the long-awaited Comite River Diversion Canal was finally underway.

Decades in the making, the flood protection project remained largely dormant for years but got a shot in the arm after the historic August 2016 flood that inundated tens of thousands of homes and businesses.

And if a reminder was needed of the project's urgency, it came with the arrival of Hurricane Barry this month — a storm that gave Baton Rouge area residents anxious flashbacks to the 2016 flood.

Forecasters were predicting on July 13 that the Comite River at Joor Road might even surpass the record levels reached that August nearly three years ago, though that crest prediction and high crests on the Amite River dropped significantly as Barry made landfall farther west than anticipated.

Conceived after a major flood in 1983, the 12-mile-long Comite diversion canal is designed to divert rainfall runoff to the Mississippi River and lower flooding levels along the Comite and Amite rivers in the Baton Rouge area.

The diversion was originally part of a two-part solution that also called for a major reservoir along the Amite at Darlington. That fizzled in the late 1990s over questions of cost-effectiveness, though it is now getting a fresh look.

The diversion went forward but was starved for sufficient funding despite years of contributions by local property tax payers until last year when Congress provided $343 million to fully fund the project. 

With money in hand, U.S. Army Corps of Engineers officials said, work on the canal is now underway and on schedule so far to be finished in the summer of 2021, though the dirt hasn't exactly started flying yet since a groundbreaking in April.

What's happening now, officials said, is land  acquisition, design work and utility relocation, officials said.

The workers busy doing the welding along U.S. 61 last week were preparing to move a petroleum line. It's among utilities and pipelines that must be relocated and rerouted under the future canal to make way for a new  bridge over the channel on U.S. 61.

The bridge is one of 13 features that have to be built for roads, railroads and other infrastructure that are now in the way of a canal that will slice cross-country through northwestern East Baton Rouge Parish, Corps officials said. The canal will also intercept smaller bayous on its path to the river.

"So, the diversion is just, that's, in a sense, the easy part," said Bobby Duplantier, Corps senior project manager for the Comite diversion. "The more challenging part is where we intersect these highways and these railroads, how are we going to come over … where our channel is going to be, acquiring the real estate, the relocations and all the different things that play into it."

The diversion starts at the Comite between Zachary and Baker and heads west to the Lilly Bayou control structure, which takes water to a bayou that leads to river. 

Congressional approval of full funding for the Comite Diversion Canal was significant because it means the Corps and other agencies can now work on different aspects of the diversion at the same time, officials with the Corps and Amite River Basin Commission said. For example, state highway officials are working on buying land while engineers design features that are part of the project.

The U.S. 61 bridge went first because design and land acquisition for it had already been finished, Duplantier said, adding that officials hope to start construction it later this year, possibly before all the utility relocation is finished.

Still, some believe the Corps' schedule remains "very aggressive."

Dietmar Rietschier, executive director of the Amite River Basin Commission, said the logistics of the complex diversion canal project could make it difficult to have it completed by 2021. 

"We're still pursuing the 2021 goal, but, most realistically, most likely what's going to happen is it's going to be another year or two years, maybe beyond that," said Rietschier.

Hurricane Barry, meanwhile offered a reminder that Mother Nature waits for no one, not even the federal government. 

The National Weather Service's projections for  the Comite River's crest at Joor Road on July 15 rose 8.5 feet over 24 hours between the evenings of July 12 and July 13, to 26 feet, then 31 feet and finally 34.5 feet.

Though actual rainfall amounts would end up being significantly less, the National Hurricane Center was projecting, at the time of the rising river forecasts, rain of 10 to 20 inches in the area, with localized amounts approaching 25 inches.

Jeff Graschel, a hydrologist with the National Weather Service's Lower Mississippi River Forecast Center, said the projected rain totals then were slightly less than what fell in August 2016 but rain was supposed to fall far more quickly than even happened in '16.

The compressed timing of the rain contributed to the high river forecasts for the Comite, he said. 

Forecasters had predicted a significant rise on the Amite as well but not beyond the levels reached in 2016. The Comite joins the Amite southeast of Joor Road.

Exactly how much a completed diversion could have lowered water levels had the Comite hit the highest predicted crest is unclea. A reduction of 2 to 4 feet is possible, some experts said, which would still mean some neighborhood flooding in the area. 

Corps estimates suggested the diversion will lower water levels by 3.8 feet in a 100-year flood on the Comite at Joor Road.

The diversion's ability to reduce flooding, however, decreases as the size of the flood increases, Corps estimates show.

At the highest crest the Weather Service had predicted for the Comite — a 34.5-foot crest at 7 p.m. July 15 — the river would have been three-tenths of a foot above the height reached on Aug. 14, 2016, when the river likely well surpassed a 100-year-flood. 

Bob Jacobsen, a hydrologist who works for the Amite River Basin Commission, one of the diversion's sponsors, added that the Corps' projections for the diversion are roughly 20 years old. The landscape has changed significantly since then and the amount data about the area has increased.

He said the Corps is finalizing the diversion's design, which should provide a better sense of what kind of flood reduction can be expected on the Comite and Amite.

Editor's note: This article was changed on Monday, July 22, 2019, to note that the workers were welding a pipe on U.S. 61 and that a bridge will have to be built over the diversion canal along that highway.

Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.