MONROE COUNTY, N.Y. — Weather conditions caused a sewage discharge into the Genesee River over the course of 12 and a half hours over Friday night and Saturday morning. But Monroe County officials say the public has no cause for concern.

“Residents should not be concerned,” said Mike Garland, Monroe County director of environmental services.

County officials say rain coupled with melting snow caused a planned discharge into the river near East River Road in Henrietta. Some 750,000 gallons of partially treated sewage were released into the river over the 12 hours.

County officials say this was not an accident, but part of a coordinated plan to keep the advanced underground water and sewer system running functioning properly.

“What’s occurred over the last four days is really a perfect storm that can really challenge any wastewater system,” said Mike Garland, Monroe County director of environmental services. “We’ve had snow melt, with warming temperatures; saturated soils; and heavy, widespread rain. This has occurred over the last several days. In fact, up at the Frank E. VanLare Water Resource Recovery facility, we’ve treated over 1 billion gallons.”

Due to that “perfect storm,” the sewer system exceeded its design capacity. “We had discharges into the river from the tunnel system at permitted locations. So the system did what it is designed to do, and it has to protect the downstream infrastructure,” Garland said.

According to Garland, the water that was released into the river was not raw sewage but screened before it made its way into the river.

“We screen that effluent, we screen it for rags and any solid material we can capture. We also disinfect it with lime. So we try to minimize the impact to the receiving water body, in this case the Genesee River and the canal,” he said.

Garland described the effluent as very “dilute.”

“What we’re discharging is characterized as very low-grade sewage – highly dilute because we’re getting mostly inflow and infiltration coming into our system, which is causing the system to surcharge” — a term meaning overloading the carrying capacity — he said. “So again it’s dilute, we screen it, we disinfect it, so it’s partially treated, and it is pumped into the Genesee River, which is flowing at a much higher rate than it normally is. So that is really blended in and it really has very, very minimal impact. Residents should not be concerned.”