Aluminum Domes

Tucked snugly along eight miles of northern Lake Michigan shoreline, including Little Traverse Bay, the City of Petoskey, Michigan, is a resort community and prime destination for both tourists and residents.

The City of Petoskey’s Department of Public Works is designed to treat 2.5-million-gallons of wastewater daily. Situated near the coastline, the wastewater treatment plant has a popular walking path that’s easily accessible to the public. Odor control and waterfowl, such as ducks and seagulls were some of the challenges the city needed to address during facility upgrades.

“Our greatest challenges are how to help prevent odor control, waterfowl from landing in the tanks as well as extreme weather conditions and other environmental contaminates,” said Sherrie Elliott, Wastewater Supervisor of the Department of Public Works. “Petoskey is a four-seasons tourist destination that offers attractions all year round; it is essential for us to maintain a good appearance and go unnoticed as much as possible.”

Needing to cover the wastewater tanks from these elements, the city brought in consulting engineer Hubbell, Roth Clark, who looked at several options for covering the tanks: steel, aluminum, flat covers and domes.  

“We were looking for a solution that would require little or no maintenance and was aesthetically pleasing to the community around the plant. Being in such a high-traffic area, it is important for us to blend in with the general area. Not to mention, keep leaves from getting into the tanks, protect equipment and water from subzero weather activity,” said Elliott.

After reviewing product options from three manufacturers, the Department went with the consultant’s recommendation of a geodesic dome: an all-aluminum flush batten OptiDome® from CST.

CST manufactured five custom painted OptiDomes for Petoskey, two primary tanks with a diameter of 45 feet each and three secondary clarifiers with a diameter of 50 feet each.

During the design phase the project team overcame three unique challenges. First, the two existing primary tanks had outboard launders.  Second, the load bearing wall to support the domed covers was inboard from the launder troughs. 

Because the Department wanted easy access to view and maintain the weirs, launders and scum trough, CST incorporated hinged covers around the entire perimeter of the tank. Each cover is about 4-foot wide and can be independently opened and closed to provide operators quick and easy access to the important areas of the clarifier.

Third, the three secondary clarifiers had inboard launders and the load bearing wall was the outermost wall of the tank.  To provide access for these tanks, CST incorporated vertical sidewalls that elevated the domed cover to a point where operators could literally walk within the launder trough around the perimeter of the tank while being inside the dome. 

“It was a complete product offering, working closely with the consulting engineer, general contractor and the City of Petoskey, giving them the most optimum and aesthetically pleasing design,” said Randy Hamlett of Hamlett Environmental Technologies, authorized Manufacturers Representative of CST.

“The new aluminum domes along with the structural design modifications will provide the City of Petoskey with a long-lasting cover solution for many years to come,” said Julian Perez, Project Manager of CST.

“I was impressed with the fact that we could pick colors and have the domes factory painted. Our operators needed to be able to access the inside of the tank, have the headspace to walk – see the process and to complete maintenance inside the domes,” said Elliott.

Elliott adds, “From the appearance of the domes, to its accessibility as well as its versatility, all our needs and expectations were met.”

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