The City of...
Tank covers tackle a decade-long problem in Wyoming, Mich.
When people drive through the city of Wyoming, Mich., these days, they will likely be happy to notice some of the new parks. But they also will be happy not to notice the odor that can accompany a municipal wastewater treatment plant serving more than 140,000 local residents. In fact, they will not find any reference at all to the city’s wastewater treatment facility.
A suburb of Grand Rapids, Wyoming is responsible for processing wastewater from within the city, as well as four surrounding communities and discharging clean water into the Grand River. During the past 10 years, the need for odor control, as well as a focus on environmental issues, drove significant changes in the city’s wastewater treatment processes.
In 2004, the city came under legal pressure to control odor. The ensuing changes caused the city to alter its perspective on operating a wastewater treatment plant to its ultimate end goal: delivering clean water.
In 2000, in an effort to keep up with population growth, Wyoming installed a new 120-ft-diameter concrete biosolids storage tank with an flat aluminum cover to complement two concrete tanks with dome-style covers already in use. The city bid the project, and its selected contractor awarded a furnish-and-install contract to CST Covers (formerly Conservatek and Temcor). The odor containment cover was installed by CST’s certified construction crew.
The city selected a truss-supported, extruded flat aluminum cover for many reasons.
“The flat design significantly reduced the foul air volume being processed, versus a dome design, in which the encapsulated air volume is much greater,” said Jack Staat, regional sales manager for CST. “The reduced air volume of the flat covering system allowed downsizing and associated cost savings of the foul air handling and odor control system.”
In addition, the aluminum cover design was not only durable and corrosion resistant, but also weight bearing, which provided facility operators with walkable access to various locations on the tank without the need for an access bridge. The cover also featured a non-skid surface for safe, slip-resistant access.
“Once we understood that the weight-bearing cover provided access to the tank without the need for an access bridge, our choice and the installation process became much cleaner and simpler. It was an added benefit that the new flat cover provided much better aesthetics and overall appearance,” said Tom Wilson, maintenance supervisor for the city of Wyoming Clean Water Plant.
Five years later, the city chose to replace the dome covers on two existing concrete biosolids storage tanks with flat aluminum covers. Because the city had been pleased with the performance of the previously installed flat cover, it turned to Black & Veatch, which wrote a sole-source specification to purchase two new CST covers. The two 120-ft-diameter truss-supported extruded flat aluminum covers were placed on the existing biosolids storage tanks for more efficient odor control.
“After we saw how well the CST cover worked for looks, strength and odor reduction, we decided to remove the fiberglass domes and replace them with CST covers,” Wilson said.
In 2007, the city embarked on a major $36-million expansion to its wastewater treatment plant, which included upgrades to existing process equipment, new odor control systems, removal of trickling filters and construction of new aeration tanks. Even though this upgrade resulted in a significant overall improvement to the system, Wyoming’s work was not complete.
In 2009, the city began a rehabilitation project on the plant’s four existing primary clarifiers. The project included the addition of odor-containing covers and foul air handling. At the city’s request, designers Black & Veatch once again wrote a sole- source specification for CST flat covers to be used on the project. With its proven history working for the city, Davis Construction, a certified installer of CST Covers, was selected for the job.
The existing primary clarifiers and splitting chamber were upgraded with the intent of finalizing the plant’s odor control strategy. The city installed truss-supported extruded flat aluminum covers for four 103-ft-diameter primary settling tanks and its open-top flow-splitting chamber. It also chose to mount non-standard railings and man-lift sockets at various access hatches, so CST engineering staff worked those into the design.
This time, adherence to a strict critical path schedule for improvements to the primary clarifiers was essential. The city could not afford to take more than one clarifier off line at a time. In addition, it wanted the project completed as quickly as possible to meet mandated timeliness set by its odor control program. The entire four-tank installation needed to be completed within the shortest possible time frame.
Davis Construction submitted its bid, and within six weeks of signing the contract with the city, the materials for the first clarifier cover were staged and put in place. The upgrades to the primary clarifiers included repairs to the tanks, which had to be completed within a 10-day period. Once a tank was taken out of service, Davis Construction and CST had approximately one month to complete the repairs and cover installation, and place it back into service before moving to the next tank.
“Having worked with them several times before, we were confident in CST, Covers, as well as the quality and delivery efficiency of the product,” said Rob Kaliniak of Davis Construction. “In this case, a quick delivery and installation sequence was critical, and CST Covers delivered what we needed on time and without a hitch.”
The city allotted Davis Construction 12 months to complete the entire project, and because of the smooth installation process and delivery of materials, the installer finished three months ahead of schedule.
“There was excellent project planning on behalf of Davis Construction, which resulted in our upgrade completion significantly ahead of schedule. This was a challenge, and we were very happy with the outcome,” Wilson said. “The aluminum covers from CST have performed extremely well for our city in terms of odor containment.”
“The great design of the product made it easy for us to install and finish the construction using less labor and ahead of schedule,” Kaliniak said.
The city of Wyoming continues to be forward thinking and focused on providing high-quality services in a cost-effective manner.