Protecting the Bay for a Sustainable Future


Have you ever wondered where used water (“wastewater”) goes after it leaves your home? Did you know that it eventually reaches the San Francisco Bay? It first travels through a series of sewer pipes and pumps called a sewer collection system and then gets treated at the Wastewater Treatment Plant before it is safe to flow into the Bay.

The Clean Water Program is a comprehensive plan to upgrade the aging wastewater collection and treatment system with advanced infrastructure that will provide reliable services for years to come. The Wastewater Treatment Plant components of the Clean Water Program are a joint effort between the City of San Mateo and City of Foster City/Estero Municipal Improvement District (EMID). The City of Foster City is a partial owner of the Wastewater Treatment Plant. The Goals of the Clean Water Program are to:


Replace aging infrastructure and facilities

Build wet weather sewer system capacity assurance to prevent overflows

Meet current and future regulatory requirements

Align with the City of San Mateo and Foster City's sustainability goals

Read Wastewater: The Basics to learn all about San Mateo’s sewer collection system and Wastewater Treatment Plant!

Please visit the Underground Flow Equalization System page for important information on this phase of the Clean Water Program.



Latest Info


UPDATE! Additional UFES Final Environmental Impact Report Documents Released

In addition to the Final Environmental Impact Report for the Underground Flow Equalization System Project, two other project documents were released on September 10, 2019: (1) Errata No. 1, which includes 40 additional comments and responses, and (2) the Mitigation Monitoring and Reporting Program, which summarizes the mitigation measures discussed in the EIR and implementation responsibilities. Both can be found on the Final EIR page.


Final UFES Environmental Impact Report Released

The Final Environmental Impact Report for the Underground Flow Equalization System Project is now available. This final version of the document includes responses to written and verbal comments and questions received during the public comment period, which ran from March 6 through May 31, 2019.

The Final EIR is available for download at the Clean Water Program website on our Final Environmental Impact Report page. Hard copies are available at City Hall and the San Mateo Main Library.

The Planning Commission will vote on a recommendation for Final EIR certification, and concurrent Special Use Permit approval, to City Council at its upcoming meeting on September 24, 2019. City Council will vote on certification of the Final EIR, and approval of the concurrent Special Use Permit, at their October 21, 2019 meeting. (Please note – this topic has been moved from the October 7 City Council meeting.)

Planning Commission meetings and City Council meetings are all held at 7:00 pm at City Hall Council Chambers, 330 West 20th Avenue, San Mateo, CA 94403.

Please visit our Underground Flow Equalization System page for additional project details and updates.


San Mateo Breaks Ground on New Wastewater Treatment Plant

On Wednesday, Sept. 4, 2019, the City of San Mateo welcomed Representatives Jackie Speier and Anna Eshoo, along with Foster City Mayor Sam Hindi to celebrate the groundbreaking of our new wastewater treatment plant.

The plant is the largest component of the Clean Water Program, a $1 billion initiative launched in 2015 to modernize the San Mateo sewer system, a response to a Cease and Desist Order from the State of California mandating a sewer system upgrade to eliminate sewer overflows from entering the San Francisco Bay.

“These infrastructure improvements are vital to the sustainability and future of San Mateo,” said Mayor Diane Papan. “We greatly appreciate the advocacy of our council and the support of our Senators Dianne Feinstein and Kamala Harris, as well as congressional representatives Jackie Speier and Anna Eshoo, the encouragement from the EPA and our partners in Foster City, who worked on our behalf to support low-cost funding alternatives for the program.”

The new plant will replace an aging plant that saw its last major upgrade in the 1970s. Construction on Phase I of the new plant begins this month.

“We are five successful years into the largest upgrade to our sewer facilities,” said Public Works Director Brad Underwood. “The Clean Water Program is a necessary and timely endeavor that we must deliver on for the sustainability of our City and the health of the San Francisco Bay.”

The new plant will feature a modernized treatment process meeting the program goals to replace the City’s aging infrastructure and comply with regulatory requirements to prevent sewer overflows and fully treat flows at the plant. The new plant also aligns with the City’s sustainability goals; the administration building will be LEED Silver certified and the plant will produce high-quality effluent that is ready for potential water re-use opportunities. The new plant is set to open in 2024.

Wastewater Treatment Plant Groundbreaking Ceremony

Officials Unite for Sept. 4 San Mateo Groundbreaking – Left to Right, Foster City’s City Manager Jeff Moneda, San Mateo’s Public Works Director Brad Underwood, Hillsborough Vice Mayor Alan Royce, Hillsborough Mayor Shawn Christianson, Foster City Mayor Sam Hindi, San Mateo Mayor Diane Papan, Representatives Anna Eshoo and Jackie Speier, San Mateo Councilmembers Maureen Freschet, Joe Goethals, Eric Rodriguez and Rick Bonilla, and Jim McGrath, Vice Chair, California State Water Resources Control Board.


Underground Flow Equalization System Update to Planning Commission

At the August 27, 2019 Planning Commission meeting, Clean Water Program staff provided an update on the UFES. The UFES project will help to reduce the risk of sewer overflows during heavy storms. The purpose of this UFES Informational Presentation was to familiarize Commission members with important information about the project that has been updated since publication of the Draft Environmental Impact Report in March 2019.   




Upcoming Events


Planning Commission Hearing on Special Use Permit @ City Hall - City Council Chambers
Jun 12 @ 7:30 pm

The Planning Commission meeting will include a public hearing about the application for a Special Use Permit for the planned wastewater treatment plant upgrade and expansion project. The Commission will then vote on its recommendation to the City Council. The wastewater treatment plant project includes changes to the existing facility, and construction of new facilities adjacent to the existing site. Some of the older facilities at the existing treatment plant will be removed or re-purposed. The project includes a pedestrian path around the treatment plant from Dale Avenue to John Lee Dog Park, modifications to the existing landscaping along East 3rd Avenue, and closure of a portion of Detroit Drive.

City Council Hearing on Special Use Permit @ City Hall - City Council Chambers
Jul 16 @ 7:00 pm

The City Council meeting will include a public hearing on the Special Use Permit discussed earlier at the June 12 Planning Commission meeting. The City Council will vote on the approval of the Special Use Permit at this meeting. The City Council will also vote on the approval of an addendum to the Program Environmental Impact Report.

Construction Symposium/Upcoming Opportunities @ City Hall - City Council Chambers
Aug 8 @ 10:00 am – 12:00 pm

The City of San Mateo Clean Water Program invites potential construction bidders, construction management consultants, labor compliance firms, safety management consultants, specialty inspection firms, and companies specializing in materials testing and laboratory services that may be interested in responding to upcoming opportunities under the City of San Mateo’s Clean Water Program.

Symposium topics will include the following: 

  • Overview of the Clean Water Program
  • Discussion of upcoming Requests for Proposals for professional services
  • Overview of Construction Contract Bid Packages for the wastewater collection system and treatment plant
  • Procurement schedule for professional services and construction bid advertisements

Please RSVP to Chris Bessa at

For more information, please email or call Chris Bessa at, 510-387-5498.

Wastewater Treatment Plant Upgrade and Expansion Informational Meeting @ Parkside Elementary, LGI Room
Aug 21 @ 6:00 pm

The Clean Water Program will be hosting a neighborhood meeting to update residents about upcoming work to upgrade and expand the wastewater treatment plant. You can download a meeting flyer for more information.

Public Scoping Meeting for the Underground Flow Equalization System @ City Hall - City Council Chambers
Oct 2 @ 6:00 pm

The Clean Water Program will host a public meeting to provide information and receive public input on the Underground Flow Equalization System project – formerly called the In-System Storage Facility.

The Underground Flow Equalization System helps eliminate the potential for sanitary sewer overflows during extreme storms and is part of the City’s Clean Water Program, a 10-year effort to improve and repair the aging sewer collection and treatment system.

In compliance with the California Environmental Quality Act, the City is preparing an Environmental Impact Report and is seeking public input on what factors to study. The October 2, 2018 meeting is one way for the public to learn more about the Underground Flow Equalization System project and provide input that the city will consider during preparation of the EIR. During storms, rainwater enters the sewer system through cracks and other defects. The amount of rainwater can overwhelm the system’s current capacity, resulting in overflows at the wastewater treatment plant and at locations around the city, such as manholes. These overflows containing a mixture of rainwater and untreated sewage are a danger to human health and the environment because they contaminate streets, creeks, lagoons, beaches and the San Francisco Bay.

The approximately 5-million gallon underground holding structure is proposed to be located in the eastern portion of the San Mateo County Event Center parking lot off Saratoga Drive. This location was selected by the City Council in 2017 after a lengthy series of public meetings and hearings. When the sewer system becomes overwhelmed during heavy rains, the facility will serve as a temporary holding area, generally for 24 hours or less, until the mixture of rainwater and sewage can be treated at the plant. This allows the wastewater treatment plant to “catch up” with the high flows. The structure will also include advanced odor control features, such as air-tight vaults and carbon filters, as well as mechanisms to flush and clean the structure. The design of the project is sixty percent complete, and more details about construction schedule and cost will be released when they are available.

Please click here for more information and answers to frequently asked questions.

All comments must be submitted by October 22, 2018.
Comments also can be submitted via email to or regular mail:
City of San Mateo
Clean Water Program
Attention: Heather Waldrop
330 W. 20th Avenue
San Mateo, CA 94403

City Council Study Session @ City Hall - Conference Room C
Feb 19 @ 5:30 pm

The Clean Water Program will provide a program update to City Council. As part of this update, staff will share information on the status of the collection system and WWTP design projects, schedule of construction activities, overview of the financial strategies adopted to fund the program, and mitigation efforts taken to address the current competitive market conditions.

Planning Commission Public Hearing on Wastewater Treatment Plant @ City Hall - City Council Chambers
Mar 26 @ 7:00 pm

Planning Commission Public Hearing on Wastewater Treatment Plant Planning Application Modifications.

Planning Commission Study Session and Public Hearing @ City Hall - City Council Chambers
Apr 9 @ 7:00 pm

Planning Commission Study Session and Public Hearing on Underground Flow Equalization System project and Draft Environmental Impact Report.

City Council Public Hearing on Wastewater Treatment Plant @ City Hall - City Council Chambers
Apr 15 @ 7:00 pm

City Council Public Hearing on Wastewater Treatment Plant Planning Application Modifications.

Sewer Lateral Ordinance Community Meeting @ Senior Center
Apr 25 @ 6:00 pm – 8:00 pm

For more information, click here.