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Surface Water Integration Project


The City of Turlock (City) has historically relied entirely on groundwater from the Turlock Groundwater Subbasin as its primary drinking water source. Serving a population of approximately 73,000 residents, the current water supply is provided by 18 active groundwater wells.1

As groundwater quality standards become increasingly stringent, the cost for treatment and replacement wells will continue to increase. If the City were to rely solely on groundwater as the source for their drinking water, monthly costs to treat groundwater to current and future drinking water standards would increase dramatically. It is also likely all cities will have to reduce dependence on groundwater due to the State's Sustainable Groundwater Management Act (SGMA).

Like many communities across California, the recent prolonged drought strained the City's groundwater supply and intensified the need to invest in alternative, supplemental water sources. To build a more resilient water supply, the City of Turlock has diversified its water portfolio by partnering in the Stanislaus Regional Water Authority's (SRWA) Regional Surface Water Supply Project to build a new water treatment plant and utilize a new surface water supply from the Tuolumne River.

Over the years, the City has investigated a number of alternatives to the Project. None of these options were considered as dependable, technically feasible, cost-effective, or as sustainable as a drinking water plant on the Tuolumne River. As part of the Regional Surface Water Supply Project, Tuolumne River water will be treated at a new robust, state-of-the-art water treatment plant to meet and exceed all current federal and state drinking water standards. Unlike wells, the plant can be easily changed to comply with future changes in drinking water standards, as necessary.

As a result of the Regional Surface Water Supply Project, Turlock residents will continue to have clean and healthy drinking water for the future and will benefit from a more resilient water supply during times of drought. Long term benefits of the project include improved water quality and helping to replenish groundwater supplies.

To learn more about Regional Surface Water Supply Project, visit https://stanrwa.com/

Surface Water-Groundwater Integration

Turlock is leading the integration of the new surface water supply into its existing water distribution system. The City worked with a consultant to develop an Integration Plan that includes an evaluation of historical groundwater quality and future anticipated surface water quality. When introducing surface water to a groundwater dominant water distribution system, discolored water can occur in the distribution system for various reasons. This Plan offers recommended strategies for stabilizing and flushing the distribution system to avoid discolored water events.

Introducing a new water source into an existing distribution system can be challenging and must be carefully implemented. Turlock is working diligently to ensure this new water source is integrated into its water supply with a minimal amount of water quality disruption.

Part of this effort is the gradual introduction of chlorine into the water supply that began in May 2023. Chlorination prevents the growth of harmful bacteria and eliminates viruses and microorganisms in the water, which is imperative and mandated when surface water is used for drinking water purposes. The treated surface water has a similar level of chlorine as the City's groundwater, so integration is expected to have minimal effects on residents' water quality. For more information, visit our webpage on chlorination.

The City's primary concern is minimizing the potential for discolored water occurrence by implementing the strategies recommended in the Integration Plan. However, even the best implementation cannot prevent all discolored water events, and customers should contact the City Municipal Services Department at (209) 668-5590 if they encounter any changes in the color of their tap water.

To learn more about the work that went into ensuring the proper integration of surface water in the City's existing distribution system project, view the project webpage.

Frequently Asked Questions

How much water does Turlock receive from SRWA?

Turlock has the pipeline capacity to receive up to 30 million gallons per day (mgd) of water from the SRWA Regional Surface Water Supply Project.

Where does this new water source come from?

In partnership with Turlock Irrigation District (TID), water will be drawn from the Tuolumne River for treatment at the new SRWA Regional Surface Water Treatment Plant prior to delivery to the City to be used in conjunction with existing groundwater. This diversified regional water supply provides drought management, improves water quality, and helps to replenish groundwater supplies.

Will my water look different?

Discolored water events are not unusual when integrating a new water source into an existing water distribution system. The City is taking preventative measures like stabilizing the water chemistry through the treatment process and flushing pipelines before surface water is introduced to the system.

Will my water taste or smell different?

The gradual introduction of chlorine in the water supply reduced the likelihood of noticeable changes in taste and smell, as the new surface water will contain a similar level of chlorine to what you currently receive. Surface water has a lower mineral content so there could be changes at various times of the year depending on the amount of surface water and groundwater a customer receives.

Who regulates Turlock Drinking Water?

The State Water Resources Control Board Division of Drinking Water regulates public drinking water systems in California in conjunction with the Environment Protection Agency.

How is this project being funded?

This project is being funded by a combination of state grants and low-interest loans which reduced the cost to Turlock water rate payers. The current water rates were approved in Proposition 218 by rate payers of the City of Turlock in 2017. 2

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For questions about the surface water integration into a historically groundwater system, please contact the Turlock Municipal Services Department at (209) 668-5590.

12022 Water Quality Report, City of Turlock. July 1, 2023. https://www.cityofturlock.org/_pdf/files/CCR.pdf

2Water Rate Increases, City of Turlock. https://www.cityofturlock.org/watersewergarbageservice/billspayments/waterrateincreases/


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