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TID: Surface water supply project moving forward
Plant slated for completion in 2022
TID surface water plant
This image shows an overview of the Surface Water Supply Project, which will provide Turlock and Ceres treated water for drinking from the Tuolumne River. - photo by Photo Contributed

The Stanislaus Regional Water Authority and Turlock Irrigation District are looking to take the next step in constructing a water treatment plant that will provide drinking water to Turlock and Ceres with hopes to begin working on a component of the project in September.

The origins of the Surface Water Supply Project began in 1987 when TID initiated discussions with the SRWA regarding a drinking water project that would help offset deteriorating groundwater quality and supplement groundwater supplies by providing a portion of TID’s Tuolumne River surface water.

“The concept was to provide TID surface water to these cities for drinking purposes,” said Assistant General Manager of Water Resources Tou Her.

While discussions between TID and the cities have been intermittent, the water district constructed an infiltration gallery on the Tuolumne River downstream of the Geer Road Bridge in 2001 to divert river water to a future water treatment plant.

The City of Turlock approved the first Drinking Water Agreement in October 2005, followed by Ceres, Hughson, Modesto and Keyes. Three years later, TID purchased the water treatment facility site, which is a 49-acre parcel close to the river, and in 2011, the cities of Turlock, Ceres and Modesto formed the SRWA in order to negotiate a water supply agreement with TID.

“Currently SRWA is only the City of Ceres and the City of Turlock — Modesto is no longer a part of the SRWA,” said Her.

Director Rob Santos asked Her if there was any interest from the City of Hughson to join the SRWA as it is the nearest city to the proposed water treatment plant.

“Initially when we were negotiating this and an agreement was signed, there was the interest of the Board to want to make sure other cities would be considered and have their ability to get into SRWA at some point in time or at least have access to the water,” said Her. “I believe there’s a recent interest from the City of Hughson so they are still in discussions of that.”

In 2015, TID and SRWA approved the terms and conditions of a Water Sales Agreement, which detailed how TID would provide Tuolumne River water for domestic use to the SRWA. The agreement is a 50-year term and is limited to a maximum of 30,000 acre-feet of transfer water to SRWA per year.

Santos voiced his concerns regarding the infiltration gallery and how it has not been tested or utilized since it was installed in 2001.

“I think what makes me nervous is it hasn’t been used in 17 years and we don’t have a model to base it on,” said Santos. “Guess we’ll find out when we turn it on.”

In response, Her said that the infiltration gallery will be tested after the raw water pump station, which includes a wet well and up to six pumps, is constructed. According to Her, the SRWA Surface Water Supply Project team is currently 50 percent done with the wet well design, with construction slated to begin in September.

“The concept behind this is in order to truly test the capabilities of the infiltration gallery — the pressure, capacity, as well as water quality — we need to go through with that well construction ahead of time,” said Her. “This whole design of the wet well, as well as the anticipated construction in the fall will be very telling.”

Upon completion, the raw water pump station will then be connected to a delivery pipeline that will carry water to the water treatment plant, which will filter water through a point of delivery that will then meter the water out to Turlock and Ceres through transmission pipes.

According to Her, along with designing the wet well, the SRWA Surface Water Supply Project team is also busy with designing the water treatment processes. Her said that for this, the team has been conducting water quality sampling in the Tuolumne River for months.

“It was very fortunate, at least from a design standpoint, of the increased flows that we’ve received this year. We don’t normally see this, so when you have increased flows like you’ve seen this year, it really, really impacts the water quality,” said Her. “So now they’ve got a pretty good spectrum of what it is like with low flows to what it is like to have quite high flows — and all of those would dictate the water treatment plant on water treatment process.”

Her said that if all goes smoothly, the SRWA Surface Water Supply Project team anticipates beginning the design and construction of the water treatment plant and transmission pipeline in April 2019, with completion slated for March 2022. The team hopes to commence operations in May 2022.

Also on Tuesday, Her presented Directors two solutions currently being considered to repair Bonds Flat Road, which was removed downstream of the Don Pedro Reservoir in February to minimize the amount of debris washed down the Tuolumne River when the spillway was opened.

“It’s been about a month and a half that it’s been out of service, so there’s been a lot of questions asked of me as well as staff about when we are going to come back and rebuild Bonds Flat Road,” said Her. “But we’re looking at almost a 200 percent snowpack, which we still have over two million acre-feet of water coming down. So, until we have a better understanding and move farther along in the water year so we don’t have any risk of any unprecedented or anomalies in the hydrology to affect us, we’re not going to want to rebuild that road.”

One option includes replacing the section of the road that was removed with the same type of road that was there before, which is the least expensive and fastest way to get the road reopened. The approximate cost for this option is $300,000.

“The earliest the road could be available would be the end of June,” said Her. “If we go this route, our goal would be to get it in as soon as possible and see if we can get it in July 4 because this year is the first year after many, many years that DPRA is going to have a firework show.”

The second option proposes building a bridge to span all or part of the spillway channel, which would take at least several years to complete. According to TID, the cost to complete a project like this is unknown as it depends on how much of the spillway area needs to be crossed. If the Board chooses this option, they would still have to replace the road in the meantime.