Fairfield Wastewater Treatment Facility, Fairfield, CT
The Town of Fairfield’s wastewater treatment facility was undergoing major rehabilitation. The plant was originally constructed in 1950 and was last expanded in 1972. This facility is surrounded by wetlands and discharges to the Long Island Sound. Three 105 ft diameter clarifiers were proposed to hold the wastewater during the treatment process. The facility’s close proximity to the Long Island Sound meant a high water table all year long. The clarifiers were to be constructed in an area formerly used as a municipal landfill, which brought about concerns for suitable bearing capacity. Another major concern was that the high water table would cause the clarifiers to uplift or float when empty. Helical piles were used to pin the clarifiers to the ground and resist the buoyancy force exerted by the water table, as well as support the dead load of the concrete structures. Each pile was connected to a 3 foot threaded adapter with square anchoring plates to transfer load to the pile. Five load tests were performed at each clarifier location and every tenth pile was load tested. After installation, the general contractor poured a six inch thick mud mat, FSI then pre-tensioned every pile to 8 kips to remove any possible slack. The clarifiers were formed and poured, all having a three foot thick concrete base on top of the mud mat.
Water Pollution Control Facility, Fairfield, CT
New construction, Wastewater Treatment Facility
114 helical piles for each clarifier, for a total of 342. Each pile consisted of a 1.75" shaft with an 8"x 12"x 12"x 14" lead, followed by a 14" x 14" twin helix extension installed to an ultimate load of 80 kips.
Ranging from 15-53 feet.
Each clarifier took 12 days