Castro Valley Sanitary District (CVSan) owns a 25 percent interest in the Castro Valley/Oro Loma Wastewater Treatment Plant (Treatment Plant). The Treatment Plant, along with other CVSan infrastructure assets, is the backbone of our community’s utility infrastructure. All water and waste material that goes down your drain or is flushed down your toilet heads to the Treatment Plant. Every day, the CVSan wastewater collection system transports, treats, and disposes of more than 3.5 million gallons of wastewater from homes and businesses to the San Francisco Bay. We consistently repair, upgrade, and proactively initiate major capital improvement projects to maintain our wastewater collection system. In fact, the majority of CVSan’s funding goes towards wastewater collection, treatment and disposal. We know that investment is the key to a continued high-quality wastewater collection system, and that investment in infrastructure has a direct benefit to the quality of life in Castro Valley.  

The Castro Valley/Oro Loma Wastewater Treatment Plant treats wastewater from Castro Valley, as well as parts of Hayward and San Leandro that lie within CVSan’s service area. The wastewater is treated using primary and secondary treatment. At the Treatment Plant, energy required to run the facility is generated onsite by two renewable sources. The first source is methane gas, which is generated by the solids stabilization process, and is used to produce heat and power to run the treatment plant. The second source is solar power, which is generated by onsite solar panels. Together, these energy resources enable the Treatment Plant to be self-sustaining, both now and into the future.


Primary Treatment Process

Primary treatment is a simple mechanical process that uses bar screens, grit chambers, and settling tanks to remove trash and settleable solids from the wastewater.

Learn More About The Primary Treatment Process



Secondary treatment is a complex biological process that uses bacteria to convert dissolved organic matter into suspended matter that can be settled out as sludge. The remaining wastewater is then disinfected and discharged, while the solids are stabilized, dewatered and hauled away.

Learn More About The Secondary Treatment Process


Wastewater Treatment Plant Tours

Get a First-Hand Look at How Your Wastewater Treatment Plant Works.

When: 9:30 am – Second Wednesday of February, May, August, November

Where: 2600 Grant Avenue, San Lorenzo

Sign up for an upcoming quarterly public tour below:

August 14, 2024

November 13,2024

If you are interested in a special tour, please call (510) 756-0829 or email to schedule a date and time. Special Tours are conducted on dates other than those reserved for Quarterly Public Tours and are subject to staff availability.