Corps outlines pump procedures for Tensas-Cocodrie Pumping Station
posted Wednesday, January 23rd, 2013 @ 2:11 pm

Guidelines for operation of the Tensas-Cocodrie Pumping Station at the mouth of Wild Cow Bayou indicate when the gates are closed and pumps turned on, according to the U.S. Army Corps of Engineers.

When some areas of the parish began to flood after more than 10 inches of rain fell in 48 hours on Jan. 9-11, the pumps were not turned on because the water level on the land side was three feet higher than the level of Black River.

"That's why the gravity gates are open and functioning as designed," according to Greg Raimondo, Public Affairs Chief for the Corps' Vicksburg District.

While the Corps "owns" the structure, Rig Masters Inc. of Monterey is the contractor who operates the facility. Raimondo said Rig Masters operates the facility "in accordance with the project operation manual guidelines." These guidelines "determine when the gates are closed and pumps turned on" based on water levels on both the land and river sides of the structures.

"The pumps will do no more than the gravity structure" in releasing water into the Black River, Raimondo said. "As long as the river side is lower than the land side you could hurt those pumps by turning them on. If the river side is lower, the pumps will work at 30 percent reduced capacity and you lower the water at the level of the gravity gates which reduces effectiveness."

Raimondo said his office was swamped with phone calls from Concordia Parish residents during the heavy rain event. Most callers wanted to know why the pumps were not turned on, he said.

"I probably got 40 to 50 calls," he said. "The reason the water takes so long is that a large portion of Cocodrie Bayou, the parish's main drainage source, is filled with sediment, trees and debris."

Many public officials have compared it to trying to drain a bathtub with a straw.

For the past six years, the Police Jury has held a number of public meetings to discuss improving drainage. The construction of the ring levee a half century ago cut off many natural drainage sources from the river.

No funding for dredging Cocodrie was provided through previous flood protection or drainage projects.

The Tensas-Cocodrie pumping plant and gravity flow structures are located on two forks of Wild Cow between Eva and New Era off Hwy. 129.

"The pumping station and gravity gates are two separate structures," Roimando said.

He said the pumps are on the north fork of Wild Cow and gravity gates nearby on the south fork. The five pumps at the pumping station are capable of pumping 4,000 cubic feet of water per second.

A weir managed by the Corps is located on the south side of the Wild Cow Bayou bridge five miles upstream from the pumping station at a location southeast of the pumping plant.

Cocodrie winds its way from Ferriday southwesterly to its confluence with Cross Bayou, east of Horseshoe Lake. The bayou crosses under Hwy. 565 near Deer Park before snaking its way southwesterly to its confluence with Wild Cow Bayou.

On Jan. 12, Corps hydrodraulic engineers measured the flow of Cocodrie at its confluence with Cross Bayou at 4,500 cubic feet per second.

To the southeast at the 565 bridge, Cocodrie's flow had slowed to 3,600 cubic feet per second.

Roimando said measurements showed that Cross Bayou was backing up at 750 cubic feet per second and flowing into Horseshoe and Black River lakes instead of flowing down Cocodrie.

"The water just can't get down Cocodrie because it hasn't been cleaned out in so long," he said.

However, Roimando said that if the proposed Black River Lake Control Structure had been in place it would have improved the drainage.

"Black River Lake was six feet higher than the Black River at the time of the heavy rains," he said. "Had some of the water been able to pass through there it would have helped a lot."

In fact, Roimando said the structure proposed on Brushy Bayou to drain into the Tensas River "would be a feasible solution also. Both structures will work as a drain only if the river is lower than the landside."

The Brushy Project would help drain the northern end of the parish, including the Clayton, Ferriday, Lake Concordia and Lake St. John areas, according to Police Jury President Melvin Ferrington. By diverting water from Cocodrie and through the Black River Lake and Brushy structures, drainage in the Vidalia area would also be improved. The Vidalia Canal drains the Vidalia area into the Cocodrie at the end of Bothgowan Road.

More than 30 roads were impassable during the height of a storm system that dumped more than 13 inches of rain parishwide and resulted in a 12-ft. rise on the Black River. Two large culverts on parish roads were washed out, while a number of homes took in water.

Black River began to fall early this week. On Tuesday, the river stood at 38.4 on the upstream gauge and 37.4 feet on the downstream gauge.

An alternative drainage plan proposed by the Concordia Parish Drainage Committee and Black River Lake Commission, and adopted by the Police Jury, featured the proposed construction of control structures on Black River Lake and Brushy Bayou.

In December, Concordia voters rejected a one-mill drainage tax. Monies from the tax, about $133,000 annually, would have been used to finance the yearly operation and maintenance cost of the control structures, long-term sediment removal at the structures and long-term (50 years) replacement costs.

State funding is available to build the Black River Lake structure, while the Police Jury is seeking a grant from the Louisiana Department of Transportation & Development to finance construction of the Brushy Bayou structure. The Corps requires that maintenance and yearly operational costs be set aside locally before the structures can be built.