Fairmount Reservoir Improvements

What was the challenge?

At over 100 years old, the Fairmount Reservoir is one of the Onondaga County Water Authority’s oldest assets and is the primary storage reservoir on OCWA’s Otisco Lake system, conveying nearly 20 million gallons of drinking water to Central New York every day. The existing storage reservoirs at Fairmount were outdated and in need of asset renewal. Additionally, the facility’s configuration within the transmission system contributed to high water age and low chlorine residual. Barton, Brown, Cylde, and Loguidice were retained in 1965 to construct the 10 million gallon storage tank at Fairmount to supplement the original 5.6 million gallon open reservoir constructed in 1908. With changing regulations eliminating the use of the open reservoir and the steel tank exceeding its useful life, B&L was once again retained in 2019 to design two new 6 million gallon prestressed concrete tanks in accordance with AWWA D110 standards to replace these obsolete storage facilities. To maintain a low profile with the surrounding residential community, the tanks were designed as column-supported flat slab roofs.

How did Barton & Loguidice provide a solution?

B&L analyzed and built a hydraulic model of the finished water transmission system from the Otisco Lake Water Treatment Plant to the Fairmount Reservoir to verify hydraulic capacity and possible restrictions to achieving maximum transmission capacity. The hydraulic model was also used to validate reservoir tank sizing, and overflow elevation, and evaluate operational scenarios. B&L’s analysis recommends adding three feet to the top of the tank to maximize available pressure in the transmission system, improving turnover and adding active storage to the tanks. Also, B&L developed a computational fluid dynamics (CFD) model of the tanks to analyze tank turnover characteristics.

The Fairmount facility is also a central shop and yard for OCWA’s pipeline crews. B&L’s final design included optimum site utilization for the storage tanks and storage and laydown space for OCWA’s maintenance crews. The improvements reconfigured and replaced all the yard piping, providing dedicated inlets and outlets to the tanks, and flexibility in the crossover piping to isolate tanks, operate in series, or operate in parallel.

Why was the project a success?

Throughout the project, B&L was sensitive and responsive to OCWA’s priorities and operational constraints. B&L provided a solution in the built assets to respect these priorities and improve operational flexibility, relieving these constraints. OCWA, B&L, and the Tank Constructor were all active partners throughout the project, acting in the best interest of the project, and addressing problems during construction proactively and collaboratively.