Where county crews responded to wastewater overflows 

Heavy rains from Sunday’s potent rain storm causing several wastewater overflows in Sonoma Valley.

Rainfall measured by Sonoma One Rain gages exceeded 7.5 inches in Sonoma Valley and nearly 9 inches on Sonoma Mountain, causing inflow into the two wastewater collection systems to temporarily exceed capacity.

Wastewater maintenance and work crews were staged in the field in anticipation of the heavy inflows, and used pump trucks and pumps to divert as much water as possible.

Signs were posted at overflow sites, and the State Office of Emergency Services and California Department of Fish & Wildlife were notified.

Crews continue to monitor the collection systems and to evaluate any impacts to public and environmental health. Overflows generally run into storm drains which then drain into nearby creeks.

Sonoma Water, which operates both collection systems, said is has made significant investments in projects to prevent overflows. The District is currently implementing a multi-year sewer main replacement project.

Another contributing factor to SSOs, which is being addressed by the District, is leaky private sewer laterals and illegal connections of roof downspouts, yard drains, sump pumps and other non-sewer discharges into the sewer system that can greatly increase the amount of wastewater entering the system during storms.

The SVSCD Board approved an ordinance that will require older laterals to be inspected and repaired, if necessary.

The Sonoma Valley wastewater treatment plant is capable of treating up to 12 million gallons per day (mgd) and storing up to 35 million gallons of untreated wastewater, but during heavy rain events inflow into the plant can increase by as much as nine times the average flow. Find out more about wastewater treatment by checking out Cleanawater