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Wastewater Services

What We Do

The Wastewater Division is responsible for maintaining the City’s sewer system, collection of wastewater and storm drain run off, and the treatment process. This division assures safe discharge of treated water returning to the San Joaquin River. The Wastewater Division is housed in two locations – a primary treatment facility located on Sutter Avenue and a secondary treatment and tertiary facility located on Jennings Road. The Wastewater Division treats an average of 25 million gallons of wastewater per day received from Modesto residents and businesses.


Prior to 1910, the City's wastewater was discharged directly into the Tuolumne River through a 16" outfall line at the foot of 9th Street. In 1910, the city of Modesto purchased approximately 28 acres of land at the foot of Franklin Street (which is now known as the Primary Water Quality Control Treatment Plant), and built a septic tank on the property. A new line was constructed from the 9th Street outfall line to the septic tank. However, sewage continued to be discharged directly into the river from this location.

Moving into the 21st century, the equipment at the primary plant has been replaced with more up-to-date, more efficient equipment. An additional sewage trunk line was installed to handle only cannery waste during the high harvest season. The waste, which is clean water mixed with bits, pieces and juices of fruits or vegetables bypasses the treatment process and is pumped directly onto open fields.

Frequently Asked Questions

In an Emergency


Spills reporting 24/7:
(209) 577-6200
Non-Emergency Police Dispatch
(209) 522-2470

Contact Us

Wastewater Administration
Primary Plant
1221 Sutter Avenue
Modesto, CA 95351
Directions - Google

Report a Problem or Request a Service

(209) 577-6200 phone
(209) 577-6345 fax