County staff reports two related incidents to FDEP
A contractor performing work on behalf of Sarasota County on March 10 damaged an air relief valve (ARV) at the intersection of Bahia Vista Street and McIntosh Road, which led to two sewage spills, county staff has reported to the Florida Department of Environmental Protection (FDEP).
“The contractor quickly bermed the site,” the first report said. Then, with the help of county staff, the contractor attempted repairs to the line, the report noted. “However, the flows were too high to keep contained within the berm,” it added. Therefore, county staff “called in all of Sarasota County’s emergency sewage hauling contractors, as well as other outside local hauling resources,” to assist with the site conditions, the report pointed out.
Approximately 42,000 gallons of raw sewage spilled at the Bahia Vista/McIntosh Road site, the report said. About 8,000 gallons were recovered, with the remaining 34,000 gallons entering a tributary of Phillippi Creek, the report added.
Because of the ARV damage, a second report explained, staff had to shut down the South Gate Master Lift Station. That led to the collection system outside the lift station overflowing through two manholes in the vicinity of 2000 Tanglewood Drive, that report said.
Approximately 62,000 gallons of raw sewage spilled on Tanglewood Drive, that report noted. About 48,000 gallons of that sewage was recovered, the report added. The remaining estimated 14,000 gallons ended up in Phillippi Creek, the report said.
County staff worked with the Florida Department of Health in Sarasota County “to ensure notices were posted” in the appropriate areas, the reports pointed out. Water sampling, notifications to surrounding property owners and cleanup protocols were proceeding, the reports added.
The ARV incident happened at 10 a.m., the reports said. The contractor was installing a sewer force main with a large diameter when the ARV was struck, county staff explained. It took county workers until 1:30 p.m. on March 10 to resolve the resulting problems, the reports to FDEP noted.
During the County Commission meeting on Sept. 9, 2020, Commissioner Christian Ziegler voiced concerns about the number of ARV-related incidents that had led to county sewage spills.
“I would like to see a plan to protect those [ARVs]” that seem most vulnerable to damage, Ziegler told Public Utilities Director Mike Mylett. “Some things in Publix parking lots are protected more than these ARV valves. … Maybe it’s dropping a cement block in front of them, so cars don’t hit ’em and mowers don’t hit ’em.”
Ziegler added, “I think we need some sort of county comprehensive plan” to prevent such incidents, because “we get blamed for the spill …”
In a blog, 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.”
Approximately 5% of the county’s ARVs have redundant protection, Mylett explained. Those are structures that have been hit multiple times in the past, he added.
Staff has compiled a list of others in rights of way, which have high potential for damage, Mylett continued.
County Administrator Jonathan Lewis also noted that Mylett had “assigned a point person” in the Public Utilities Department to work on measures to protect the ARVs.
A June 2020 county report on measures being taken to improve wastewater infrastructure noted that the county has more than 900 “sewer ARVs in its force main system.” The document added, “The County implemented an ARV rehabilitation program in September 2019 to inspect, repair, or replace as needed all ARVs and upgrade associated valves, piping and hardware to stainless steel. The County has already begun adding bollards around all vulnerable ARVs,” the document pointed out.