City Press Releases

Posted on: March 2, 2017

Modesto to Discharge Partially Treated Wastewater Due to Flooding

As a result of recent Tuolumne River flooding that inundated the sewer system, the City of Modesto will begin releasing treated wastewater that has not been disinfected into the San Joaquin River. This action is necessary to protect the pond levees and treatment process infrastructure at City’s Jennings Road wastewater treatment plant. As the ponds have reached capacity due to the flooding event. City staff has contacted the appropriate State agencies and they are fully informed of the actions the City will be taking to prevent pond levee failure and flooding at the Jennings Road facility.  The discharge of this water is scheduled to begin March 2, 2017 at 12:00 pm and will continue for as long as necessary to prevent pond levee failure. Completion could take weeks.


Treated wastewater that has not been disinfected is considered a potential health hazard because of bacteria and viruses present in wastewater, and as a precaution the public should avoid direct contact with the river during this discharge. Because of extremely high flows in the San Joaquin River, the potential hazard is lessened. The wastewater is greatly diluted. The discharge rate is estimated to be an average daily flow 30 to 45 cubic feet/second (cfs), whereas the current river flow is reported to be over 32,000 cfs downstream at Vernalis. The City is required to sample the river and report the data to the State to assess the impacts of this discharge. The public will be notified if other risks should arise.

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