CEAC-2022-06-June

shows just how much earthmoving is happening. It is almost
as long as a football field across the top, and goes down
below the surface an estimated 42 feet.
Corps officials estimate the entire project will require the
removal of nearly 9.2 million cubic yards of earth, enough to
fill the Caesars Superdome in New Orleans just about twice.
A chorus of dump trucks is piling that material into large
spoil banks lining each side of the canal; they have removed
1.68 million cubic yards so far.
One of the most dramatic alternations to the landscape for
the diversion is still to come: three local bayous will be completely
redirected into the canal.
Though the diversion of the Comite River provides about
70 percent of the flood reduction benefit from the Comite
Diversion, Bobby Duplantier, a Corps senior project manager,
said shifting the flow of the bayous will also make a big
difference.
“That’s really going to provide ... a lot of benefit to those
neighborhoods in smaller events, you know, those events
when you get a lot of nuisance flooding,” Duplantier said.
Estimates from at least two decades ago — the latest
available, though new estimates are coming — suggest
the diversion’s strongest benefit will be in the Zachary and
Baker areas, where upwards of a 6-foot drop in water levels
during a 100-year flood are projected. The bayous will also
keep some water in the diversion canal when the Comite is
too low to be diverted. But the public benefit comes with a
permanent price.
The channel will cut the White, Baton Rouge and Cypress
bayous in half. Their water north of the canal will be permanently
rerouted, Corps plans say.
Manmade electric pumps will draw water up from the future
diversion canal and dump it back into the bayous to keep
water flowing in them below the canal. The diversion will
remain a permanent barrier to aquatic wildlife, however.
In this photo taken by a drone is an aerial view of the flooded Siegen Calais
apartments Tuesday, May 18, 2021, in Baton Rouge, La. A new waterway
being carved is designed to steer water away from the Amite River and into
a canal leading to the Mississippi River, with the goal of reducing flooding
in the Amite basin. (John Ballance/The Advocate via AP)
The chutes will gradually widen as the bayous approach the
canal.
In addition to cutting about $25 million in costs, Duplantier
said the chutes eliminated a safety concern: Dramatic
waterfalls would have likely drawn curious onlookers. The
diversion won’t be a public access waterway, including for
fishermen and boaters.
“This is a much less intrusive kind of flow into our channel
versus a big waterfall, I call it, into the channel,” Duplantier
said.
The Corps of Engineers has already awarded construction
contracts for two of those chutes, at White and Cypress bayous,
but work is just gearing up.
East Baton Rouge Parish, under a prior agreement with the
Corps, will have to keep those pumps running for the wildlife,
along with most other long-term maintenance costs like
debris removal, Corps officials said. Parish officials said they
and Corps are still working out what the canal’s full costs will
be.
Corps plans had originally called for costly concrete structures
that would have sent the bayou waters spraying over
25-foot waterfalls down into the canal, Duplantier explained.
But Corps officials met with counterparts in Mississippi,
where a less dramatic and less costly option was already
being used.
So-called “rock chutes” will slow down the bayou waters for
1,200 to 1,500 feet upstream, gradually easing the transition
and funneling water down into the diversion canal’s bottom.
Volume 87 · Number 6 | 11