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$17 million water treatment plant to enable long-lasting recycled water supply 

tertiary treament plant

Diagram showing tertiary wastewater treatment facilities at the city’s wastewater treatment plant, 3200 Sulphur Springs Road.

Construction on city’s tertiary water treatment facility slated for mid-year

–Construction on new tertiary water treatment facilities at the city’s waste water treatment plant is slated to start mid-year. These facilities will cost approximately $17.2 million. The project is slated to begin in the summer of 2017 and will take approximately 18-months.

In a Feb. 7 presentation to the Paso Robles City Council, Public Work’s Wastewater Resources Manager Matt Thompson gave an overview of the facility design and the goals for recycled water usage to the council. “Tertiary treatment facilities will enable the city to turn its treated waste water, which was formerly a liability, into a new drought-proof water supply. This project will provide long-lasting benefits to our community.” said Thompson.

This project will be funded through the Sewer Enterprise Fund. Construction will be financed through a low-interest loan from the State of California’s Revolving Fund loan program. According to Thompson there is also the possibility the city may receive up to a $4 million grant in combination with the low-interest loan.

At the Feb. 7 meeting the city council approved contracts for the engineering, environmental, and construction management services that are needed as part of the tertiary treatment project.  The tertiary treatment project will make it possible to recycle treated wastewater for irrigation or recharging the groundwater basin instead of sending it down the Salinas River.

Thompson said that approximately 2900 acre feet of treated waste water is currently discharged into the Salinas River. The new tertiary facilities and associated recycled water distribution system makes it possible to reroute treated water for irrigation for existing golf courses, sports fields, vineyards and other non potable uses. “This will offset pumping of groundwater from the Paso Robles Groundwater Basin,” said Thompson.


Wastewater Resources Manager Thompson addressing the city council.

A purple pipe distribution system to deliver recycled water to east Paso Robles is being designed as part of the city’s recycled water program. Portions of the design are already being put in place. “Whenever the city rebuilds roadways, we refer to the city’s recycled water master plan. If that particular street is part of the planned route, we put in the purple pipe as part of the roadway reconstruction,” said Thompson. “This avoids the need to dig up the road later.  North River Road is an example. There is already a 1500 foot long segment of recycled water pipeline on North River Road.”

The tertiary treatment facilities will divert treated wastewater from the recently upgraded wastewater treatment plant and:

  • Route wastewater through equalization basins to smooth out the daily fluctuations in flow.
  • Filter the water with special cloth to remove particles and make the water very clear.
  • Disinfect the water with ultraviolet light to kill all harmful pathogens and salts.
  • Store this recycled water in a small storage pond with pumping facilities.


Thompson said the tertiary treatment facilities will not only produce recycled water, but also enable the city to comply with increasingly stringent requirements for discharge to the Salinas River. Last year the city was fined $495,000 for a number of infractions related to wastewater discharge from the Paso Robles Wastewater Treatment Plant. The fines were imposed by the Central Coast Regional Water Quality Control Board during the time the older facility was being upgraded. According to Assistant Executive Officer Michael Thomas the fines were imposed because water from the plant exceeded limits established in a 2011 permit 173 times between Oct. 3, 2013, and June 27, 2016.

Timeline for the tertiary wastewater treatment facilities

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About the author: Reporter Jackie Iddings

Jackie Iddings is a contributing reporter and photographer for the Paso Robles Daily News.

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