- Company: Balfour Beatty Infrastructure Inc.
- Industry: General Building
- Location: Galveston, Texas
- Project Website
Briefly describe your project? In 2008, Hurricane Ike struck Galveston, Texas, creating widespread destruction and making the city uninhabitable. The extended storm surge caused major failures through portions of the public wastewater facilities including the 10-mgd Galveston Wastewater Treatment Plant (WWTP). The storm left some areas of the plant submerged in six feet of water, taking weeks to bring service back to the returning area residents.
Balfour Beatty is restoring the 10-mgd WWTP, the FEMA-funded project is the largest Hurricane Ike recovery project. Once the WWTP reconstruction is completed, it will be a modern, highly efficient, and sturdy facility – one designed to withstand winds of up to 140 mph – for the system and its customers.
The major work included sequenced demolition of existing plant structures while constructing new plant facilities. The major structures include six sequential batch reactors (SBRs) which measured 158 x 98 ft. Supporting the SBRs, the plant’s headworks were reconstructed to include a new influent lift station, grit removal system, and bar screen modifications. The effluent was treated by a new ultraviolet (UV) disinfection facility before being discharged into Galveston Bay.
To ensure the plant could remain functioning during the construction process, the project was divided into three phases. The first phase included headworks and SBR #1, followed by SBRs #2 and #3 and UV disinfection. The third and final phase consisted of the final three SBRs. To control operations and house the major electrical equipment two operations buildings were also built, with the unique feature of housing all major equipment above the 1 in 500 year flood elevation.
To accomplish the excavation work required to construct the 5-ft-6-in-thick SBR tank foundation, Balfour Beatty used over 17,000 sf of support of excavation and maintained the groundwater via a perimeter well point dewatering system. During this time, over 22,000 cy of mass concrete was placed under a stringent mass concrete specification that required constant monitoring.
Balfour Beatty self-performed all sitework, site piping, cast in place concrete, miscellaneous metals, process mechanical equipment, mechanical piping and start-up. The complex sitework was supported by specialty subcontractors that performed support of excavation, demolition, dewatering, foundation piling, architectural precast, masonry, electrical and process controls.
The wastewater treatment plant serves about 70 percent of Galveston Island.
Scope of Work:
The reconstruction project was extensive and included the demolition of the existing structures at Galveston’s main wastewater plant (primary clarifiers, blower building, aeration basins, secondary clarifiers, chlorine contact basins, chemical storage and feed buildings, RAS/WAS pump station, lab building, storage building, and generator building) and the refurbishment of two multipurpose buildings. The team is also replacing a lift station, installing an UV disinfection facility, which replaces the chlorine contact tank with a cleaner and more environmentally friendly system, and an intermediate pump station. The work also includes construction of a grit removal system, gravity thickener, belt filter press feed pump station with a new belt press, odor control structure, and modifications to the existing headworks.
In addition, all of the new structures and buildings are built on elevated support systems to allow for continuous operation during major weather/storm surge events.
Functional testing and startup for phase 2 started for the sequence batching reactors (SBRs) and other processes through February 2015. The commissioning and turnover of the supervisory control and data acquisition automated system was completed at the end of February 2015.
“In terms of access and construction, phase 2 has been challenging compared to phase 1,” said Greg Frick, project manager. “But we’re making good progress and the team continues to work hard as we press toward our goals. We have to coordinate the tie-ins from phase 1 and phase 2 for commissioning before we can even begin phase 3. That requires a lot of careful planning.”
Three remaining SBRs will be built in phase 3.
The project was forced to work within several critical constraints including cost, construction schedule, a mandated upgrade to current codes and regulatory standards, site limitations, and tightening permit limits, the designer traded traditional design concepts for innovative technology and prepared 700 sheets of construction drawings, as well as 3D, 4D, and 5D models to help the city and team choreograph the complicated demolition and construction site plan. The current wastewater treatment plant remained in operation throughout the entire window of the new facility’s construction. Major Project Elements
The new system incorporates sequence batching reactors (SBRs), replacing the conventional treatment plant, which was a multistep process. The modernized system takes the primary and secondary clarifiers and aeration basin and combines them into one structure, a sequenced batching reactor, thus using a smaller, more efficient footprint. The Balfour Beatty team is building six sequenced batching reactors (SBRs) in four phases. Those reactors can handle about 2 MGs each. Sequenced batching reactors, a type of activated sludge process where reactors treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches, minimize the amount of piping required and are seen a more effective and efficient method for handling wastewater. “The reactor does in one structure what the primary clarifiers, aeration basin and secondary clarifiers do – but in one, efficient structure,” said, Greg Frick.
Wastewater treatment plant restoration project.
The reconstruction project was extensive and included the demolition of the existing structures at Galveston’s main wastewater plant (primary clarifiers, blower building, aeration basins, secondary clarifiers, chlorine contact basins, chemical storage and feed buildings, RAS/WAS pump station, lab building, storage building, and generator building) and the refurbishment of two multipurpose buildings.
The first SBR was built in phase 1, which also included building an operations building to house two generators and five aeration blowers. Two more SBR basins were added in phase 2 and three more SBR basins are planned for phases 3A and 3B, which were condensed into one phase.
What impact does this project have on America?
Reconstruction of the hurricane damaged Galveston Main WWTP reinforces confidence in Cities/Municipalities of the Government’s support and aid to re-build infrastructure.
Replacement of old infrastructure/plant systems provides for improved environmental efficiencies.
The project provided opportunities of construction employment for local craft within their respective skillsets as well as the acquisition of new skillsets through on-the-job training due to limited specialty trade availability.
“This is a milestone for Fru-Con, whose jobs have been largely confined to Maryland, Virginia and Washington, DC,” said Ray Bond, president and CEO of Fru-Con and Balfour Beatty Infrastructure. “It’s also significant because this job is a joint venture between Fru-Con and Southwest Region of Balfour Beatty Infrastructure, combining the strengths of a water specialist with a local civils specialist.”
“We’re building it on the exact site of the old one that works now. The new one will be resilient and will withstand the next hurricane and will withstand the next flood and it will with stand a 500 year storm,” said Galveston Mayor Joe Jaworski.
“Building this facility to such high standards will ensure the continued health and welfare of Galvestonians for generations,” stated City of Galveston Assistant City Manager Eric Wilson. “This modern facility will further affirm Galveston Island’s resiliency and expedite our recovery from future storm events,” he added.
What interesting obstacles or unusual circumstances did you overcome to complete the project?
Keeping an old plant with deteriorated infrastructure in continuous operation while subject to compromise/plant shut-down during sequenced construction phases. Temporary process (air and influent) lines to keep the plant alive were installed and managed as new construction was built about their footprint; the life line of the plant during construction.
Limited resources due to heightened local refinery work were mitigated through the sharing/acquisition of company resources from infrastructure projects in the Houston area.
Identification of plant infrastructure subsidence since first built in the 1950’s and modifying construction methods/requirements accordingly.
Potential suspect soils remained undisturbed through the use of a support of excavation system (sheet-pile) in lieu of open cut excavation in order to build some of the below grade structures.
The Sequence Batching Reactors (SBR’s) and Operation Buildings mass concrete foundations were 6.5 feet to 8.5’ in depth. In order to maintain the necessary concrete curing process (core temperature of the mass section no greater than 35 degrees relative to the extremities of the section for a period of 14 days), liquid nitrogen was used to obtain concrete placement temperatures of 75 degrees Fahrenheit or less; forms for placement were insulated; polyvinyl chloride (PVC) tubes for cooling water were placed within the mass section and sprinkler systems/curing blankets were used as needed.
Work in an Urban Setting:
All of the work progressed without interrupting the flow and operations of a plant that has remained online for the duration of the project.
“That was part of the challenge,” Frick says. “We had to keep the old plant running while we built the new plant virtually on top of it. We have had similar projects in the past, so that helped us plan and prepare. We certainly would like to have a greenfield, where you start from scratch, but we are capable of working in a running or existing plant.” Awards 2011 Bentley Be Inspired Award for Innovation in Water and Wastewater Treatment Plant to the City of Galveston and CDM Smith, Inc.
Additional Information and Project Resources:
Just one example of how construction crews found a way to keep everything flowing is that the old blower building had to be torn down in order to build phase 1 of the new plant, but the existing system required air to adequately complete the biological process that are part of wastewater treatment.
The team installed a temporary blower system to feed air to six existing aeration basins, piping raw sewage temporarily through the first operations building – from the headworks and over work being done on the first phase to the existing aeration basins.
What dangers and risks did you encounter, and describe any extraordinary methods used to keep workers safe?
As mentioned above, maintaining temporary air and influent process lines to keep the plant in operation while building new around them. The lines were elevated as much as possible and delineated for all personnel to clearly identify potential hazards to themselves and the plant process.
The plant was confined to an 8 acre footprint with powerlines on the south side; wetland to the east side; disposal site to the west and Galveston Bay on the north side. Some new structures were within 10 feet of the existing power lines. Power lines in these locations were relocated.
Exposure to high ground water tables and deep excavations were maintained through a tight well point system and soldier pile/lagging. At ground level, the perimeter of the excavation was protected by barricading/railing.
How did you leverage new technologies to work faster and reduce waste?
Through soil testing/analysis, existing on-site excavated materials were verified to meet specification requirements and re-used for backfill.
The SBR technology consumed less real estate than the traditional/existing plant process allowing for a sequenced approach to construction permitting the plant to stay alive while building adjacent new.