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Sue Stephenson
(925) 875-2295 office
(925) 570-5739 cell

Lea Blevins
(925) 875-2294 office

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Primary Treatment Project to Increase Efficiency

Post Date:06/19/2019

Contact: Lea Blevins, 925-875-2294 (office), 925-557-0161 (cell), 

PLEASANTON (June 19, 2019)—Dublin San Ramon Services District has started a major capital improvement project at the Regional Wastewater Treatment Facility in Pleasanton that will increase efficiency to improve the wastewater treatment process and reduce energy costs.

An aerial view of the primary sedimentation construction at the wastewater treatment plant.

Photo: An aerial view of the demolished primary tank in May 2019. 

The $19 million project is the largest undertaken by the District since a treatment plant expansion in 2000.

Contractors began work in April on the Primary Sedimentation Expansion and Improvements Project, which will increase the primary treatment capacity by 33 percent. Construction is estimated to continue through fall 2021. View a time lapse video of primary sedimentation construction.

Currently there are four primary sedimentation tanks at the facility. The project involves constructing a fifth tank and partially demolishing and replacing an existing one. These two new tanks will be 100 feet long, 20.5 feet wide, and 15 feet deep. The project will also replace the internal mechanisms of the three remaining tanks (100 feet long, 20.5 feet wide, and 10.5 feet deep) as well as the motor control center, and an additional grit tank will also be added.

The grit tanks remove small material, such as gravel and sand, to protect equipment and prevent clogged pipes at the plant. Once the wastewater reaches the primary sedimentation step, scum is skimmed from the water’s surface and solids are scraped from the bottom of each tank. From here, the sewage is split into two separate streams of treatment for liquids and solids. Learn more about the treatment process.

Currently the primary treatment capacity is undersized for the facility’s average dry weather flow of more than 10 million gallons a day. Insufficient primary treatment capacity can add stress to the next steps in the wastewater treatment process.

The construction manager inspects the rebar in place before the concrete base is poured for the new primary sedimentation tanks.Photo: A construction worker inspects the rebar in place before the concrete base is poured for the two new primary sedimentation tanks on June 18.

Once the project is complete, having two deeper tanks as well as improving the internal mechanism configuration will allow the wastewater to spend more time in the primary tanks, which will improve separation of solids and liquids. Removing solids earlier in the process will also help reduce energy use in secondary treatment.

The improvements will also enable the plant to send more solids to digesters that create biogas, a renewable fuel used to generate electricity to heat and power the plant. The expansion and improvements will provide the needed primary treatment capacity for both current flows as well as anticipated community buildout.

Founded in 1953, DSRSD serves 186,000 people, providing potable and recycled water service to Dublin and the Dougherty Valley area of San Ramon, wastewater collection and treatment to Dublin and south San Ramon, and wastewater treatment to Pleasanton (by contract). DSRSD also operates the Jeffrey G. Hansen Water Recycling Plant and the backbone recycled water distribution system on behalf of the San Ramon Valley Recycled Water Program. The District office is located at 7051 Dublin Blvd., Dublin CA, 94568. For more information about the District, visit

Dublin San Ramon Services District logo, Water, wastewater, recycled water 

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