County staff cites failure of air release valve as cause
On Friday, June 5, about 30,000 gallons of raw sewage spilled from a manhole near the intersection of Bee Ridge Road and Mauna Loa Boulevard in Sarasota after an air release valve (ARV) associated with a 16-inch sewer force main failed, Sarasota County Public Utilities staff has reported to the Florida Department of Environmental Protection (FDEP).
An estimated 21,000 gallons of the sewage was recovered, the report noted.
Several stormwater structures were affected, the report acknowledged; however, it says, “no wastewater reached any waterways or surface waters …” Therefore, the report adds, no sampling was required in an effort to protect public health.
As Crane Engineering explains, “Air release valves are installed at the highest points in a pipeline where air naturally collects. Air bubbles enter the valve and displace the liquid inside, lowering the liquid level. When the level drops to where it no longer buoys the float, the float drops. This motion pulls the seat away from the orifice, triggering the valve to open and vent the accumulated air into the atmosphere. As the air is vented, liquid re-enters the valve, once again buoying the float, lifting it until the seat presses against the orifice, closing the valve. This cycle automatically repeats as often as necessary to maintain an air-free system.”
Additionally, the U.S. Environmental Protection Agency points out that sewer force mains “are pipelines that convey wastewater under pressure from the discharge side of a pump or pneumatic ejector to a discharge point. Pumps or compressors located in a lift station provide the energy for wastewater conveyance in force mains.”
Cleanup activities were being conducted at the site in accord with established protocols, the report continues. County staff planned to “replace the failed ARV components and evaluate the assembly to determine the cause of the failure,” it says. “New components will be installed to restore reliability and help prevent similar incidents in the future.”
The incident began at 7:15 p.m. on June 5 and was resolved by 9:30 p.m., the report notes.
The infrastructure involved is part of the Bee Ridge Water Reclamation Facility service area, the report adds. Located at 5550 Lorraine Road in Sarasota, the Bee Ridge wastewater treatment plant is the county’s largest.