Fast-Track Precast Beefs Up Infrastructure After Hurricane

By Greg Snapper
gsnapper@precast.org

When Hurricane Katrina roared through New Orleans it crippled the central business district offices of mega-corporation the Shell Group. Fortunately for Shell, it had a training facility 50 miles to the north in the small rural town of Robert, La.

The Robert facility, used to train employees for off-shore jobs, accommodates a maximum of 120 people and also serves as the incident command center for the Shell Group in times of catastrophe. The influx of dislocated New Orleans Shell employees tripled the size of the facility overnight and caused serious stress on the training facility’s infrastructure.

Gainey’s Concrete Products Inc., which had already been working on a new wastewater collection line and treatment system for the Robert plant, came to the rescue.

“Before Katrina hit, our initial plans were to have the wastewater treatment system installed in October,” said Benny Buras, 31-year-veteran environmental specialist for Shell. “We put Gainey’s in a bind, but we knew we had to move that date up.”

The request to significantly move up the installation date from October to ASAP came Labor Day, Sept. 5, at the home of Lisa and Greg Roache, vice president and CEO of Gainey’s. In the phone conversation with Shell representatives, Lisa said it was indeed possible to achieve their timetable and construction at the Robert facility began the next day. This work added capacity to accommodate the facility’s new population and collection system, which provided tie-ins to numerous temporary offices. The lift station allowed the plant to be relocated to a remote part of the property, in an area away from the offices.

The precast concrete components of the 10,000-gallon per day extended aeration wastewater treatment plant – 48-inch diameter manholes, 12-foot deep lift station and 5,000-gallon equalization (EQ) tank – arrived the week of Sept. 12, all having been designed, manufactured and delivered in seven days. And by Sept. 16, the collection system and sewer treatment plant was completely installed. All were then left to settle for a week prior to final dress up, and work on the mechanical and electrical components began during the interim. This was the week Hurricane Rita blew through western Louisiana and shut the Robert facility down for one day. Work started right up the following Monday, Sept. 26, and the system was successfully tested Sept. 29.

That same day tests were completed, lines from the existing wastewater treatment plant at Robert were tied into the new system. The old system originally to be replaced in October was getting the boot early because of its inability to support the influx of Shell employees. “We had the existing plant pumped dry and then knocked in the sides of the plant,” Lisa said. “We bypassed this old system to connect to the new system.”

The extended aeration wastewater treatment plant brings with it infrastructure the Robert facility never had. “The plant treats 10,000 gallons of wastewater daily and has a 5,000-gallon holding capacity equalization tank,” Lisa said. “We’ve designed the EQ tank to be aerated and oversized the clarifying and disinfection chambers so that if Shell needs to expand at some point, then they can add additional treatment capacity through minor plumbing changes.”

Regardless of Shell’s desire to expand or not, the filtration process will stay the same.

From waste to water
In Shell’s system, raw wastewater is gravity-fed through a series of collection lines from the employee trailers. Upon reaching the lift station, the wastewater is then force-pumped using a duplex system of two submersible pumps to the oversized equalization basin. The more employees at Robert, the harder the pumps work. Each pump is capable of pumping 83,500 gallons of wastewater a day. The highly variable flow is normalized and fed and a slow, constant rate to the sewer treatment plant through another series of duplex dosing pumps installed within the EQ basin, thus assuring proper retention time and treatment through the sewer treatment plant. Wastewater is then pumped from the lift station to the aeration tank.

Aeration to the EQ tank assures proper mixing and begins the process of converting from anaerobic to aerobic digestion. Twenty-four hour retention in the sewer treatment plant provides an average 90 percent reduction in organic loading and the wastewater is then allowed to settle for four hours in the clarifier. The sewer treatment plant effluent then makes contact with a chlorine-fed tablet feeder and allowed to meander through the final chlorine contact chamber prior to discharge to its receiving stream. Over a period of approximately 30 hours, raw sewage with organic concentrations ranging between 200 and 250 mg/liter is reduced through aerobic digestion to a maximum of 30 mg/liter to achieve this facility’s discharge permits organic limit. Thoroughly clarified at this point in the filtration process, water is then pumped through an outlet pipe to the chlorine contact chamber, where it is disinfected. The clarified water is then gravity-fed to the receiving stream, which flows into Lake Ponchartrain, about 15 miles to the southeast.

“What literally comes out of the back end of the plant is like drinking water,” Roache said.

Clarifying wastewater has become second nature for Gainey’s. And in Roache’s experience with manufacturing, selling and installing the systems, no other building product would have met Shell Group’s immediate needs after Hurricane Katrina crippled the New Orleans office. “Steel would have been a six- to eight-week lead time for this type of project,” he said. “Precast was a tremendous material to get in the ground fast.”

Project: Shell Group Wastewater Treatment Plant, Robert, La.
Owner: The Shell Group
Contractor: Gainey’s Concrete Products Inc., Holden, La.
Precast Manufacturer: Gainey’s Concrete Products Inc., Holden, La.
Gainey’s Concrete Products Inc. is certified under the NPCA Plant Certification Program