Necessary upgrades

Projects at two Shreveport plants will boost capacity, improve efficiency

By Karla Wall

Upgrade projects have been underway since May 2005 at two Shreveport wastewater treatment facilities. The projects, under a single $22.3 million contract, will be completed by May.

Upgrades at the Lucas plant are being done to increase the capacity of the facility, said Barbara Featherston, project engineer with CDM of Shreveport.

"The plant was built in the late 1970s, and while there have been a few modifications made over the years, nothing has been done to increase the plant's capacity," Featherston said. The upgrades will allow the plant to meet the demands of the increased population in the area.

The North Regional plant projects are geared toward improving efficiency.

"The process just wasn't keeping up with the demand," Featherston added. "There were inflow problems in wet weather." The plant is in a low-lying area.

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The North Regional project includes the addition of a high-rate clarifier, said Bernie Isom, project manager with primary contractor Max Foote Construction of Shreveport. The 61- by 64- by 25-ft.-deep concrete tank is constructed of 4,000-psi concrete and sunk 10 ft. into the ground, Isom said.

About 3,600 cu. yds. of concrete were used for both facilities, Isom said.

Roughly 12,000 cu. yds. of dirt were removed at the North Regional facility to make way for the new additions, which also include a diversion box to divert flow during wet weather. The tank is 16 by 16 by 20 ft. deep and is also formed with 4,000-psi concrete.

An influent pump station is also being added that will include three 75-hp vertical turbine pumps from Fairbanks Morse of Beloit, Wis. Ductile iron piping measuring 48 in. diameter will take flow from the pump station to the new clarifier, Isom said.

He said about 6,000 ft. of ductile piping furnished by C & B Piping of Birmingham, Ala., were necessary for the project, including 36-in., 42-in. and 48-in. pipe. Piping is routed mainly underground at depths of 3 to 20 ft. throughout the plant. Exposed pipe at the pump station is routed 12 ft. above ground on concrete or steel supports.

About 10,000 sq. ft. of concrete roadway was removed to install the new piping, Isom said. Road excavation was handled in-house.

Ventilation and exhaust systems for administration and equipment buildings are also being installed at the North Regional Plant by Thermo-Technics of Shreveport. Raymond Hill of Thermo-Technics said the systems heat outside air to keep temperatures stable.

Specially-coated "hazardous duty" 10 kw electric heaters from Trane are being installed, Hill said. Coated with an epoxy-like substance, the heaters are less prone to corrosion, a problem in North Regional's damp environment. Heaters are wall- or ceiling-mounted. Ductwork for cooling and heating systems is aluminum, also to prevent corrosion.

Exhaust fans for the North Regional project are roughly 30 in. by 30 in. by 3 ft. tall. The fans move 3,600 cu. ft. of air per minute.

Electrical work at North Regional includes the installation of a dual-feed supply system with an automatic back-up for each system and each piece of equipment at the facility, said Kevin Johnson of Feazel Electrical Contracting of Shreveport, electrical subcontractor.

Power is routed through a 15-kw substation building to 16 localized transformers that bring the power down to 480 watts, Johnson said. Power is distributed through across-the-line starters and variable frequency drivers. About 20,000 ft. of 15-kw cable is routed 36 in. below grade in concrete duct bank.

A new automated control system includes programmable logic controllers at each equipment site and connected in a looped network. A local computer controls the network from the administration building. The computer, using MMI software, provides operators with a diagram rather than warning lights, Johnson said. About 18,000 ft. of fiberoptic cable was used.

The Lucas project requires the addition of a concrete high-rate clarifier tank as well as new air conditioning, ventilation and de-humidifying systems.

Hill said the environment at Lucas is reactive to most metals, so ductwork is also aluminum.