Storm, Sewer, and Wastewater

Our underground collection system is comprised of 260 miles of sanitary sewer lines and 75 miles of storm drains. Storm drains, or "outdoor drainage," typically flows to the nearest creek or watercourse. Indoor wastewater drains are connected to a network of sanitary sewer lines that flow to San Mateo's wastewater treatment plant where the waste is treated before it is discharged into the San Francisco Bay.

Did you know we're currently upgrading our wastewater treatment plant? Find out more about the work we're doing at

Managing Our Underground Collection System

Maintaining the underground collection system is a 24-hour operation. The underground system, managed by our Public Works Department, is vital to the health and well-being of our community. To ensure that the wastewater treatment plant and underground collection system operates properly and provides reliable service to the community, we meet regulatory requirements, maintain infrastructure, and align with the environmental and sustainability goals of San Mateo.

Find out more about the Clean Water Program at

Responsibilities of Property Owners

Our private sewer lateral ordinance states that the property owner is responsible to repair, replace, and maintain their sewer lateral. In the ordinance details, a private sewer lateral is defined as the pipe running from the building to the city sewer main, including the wye connection at the city main. This DOES include any portion of the pipe that crosses into the public right-of-way and is buried underneath the sidewalk and street. 

In 2020, City Council approved an amended Private Sewer Lateral Ordinance, visit the Private Sewer Lateral Ordinance webpage.

Sewer Lateral Program

San Mateo residents and property owners are responsible for maintaining their sewer lateral, which is the line that connects a home or structure to the City's sewer system. If you are experiencing problems with your sewer lateral or if it needs replacement, our Sewer Lateral Cost Sharing Program may help.

Environmental Protection

Residents can also help protect the environment and our sanitary sewer and storm drain systems by reporting illegal dumping, pollution or nuisance conditions, and other maintenance concerns to the Public Works Department by calling (650) 522-7300 or use our online complaint form.

If you have questions about the environmental quality of our underground collection system or to learn more about how you can help, please call our Environmental Compliance Office at (650) 522-7342.

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