Tri-Valley continues exploring potable water reuse

Tri-Valley water agencies recently reviewed results of a feasibility study on the prospect of bringing a potable water reuse system online to supplement the region’s water supply, liking what they’ve seen so far and asking for more research on potential project options.

Pleasanton joined Dublin and Livermore water service providers back in 2016 to finance a consultants’ study to see if potable reuse would be feasible in the Tri-Valley, based on regulatory, technical and financial considerations.

With the results now ready, governing boards for the local agencies in recent weeks have heard from the consultants and their staffs about where things stand (yes, potable reuse is feasible, but the price is high) and given a chance to step away from further analysis if opposed to the concept — and they all remain on-board.

“I just want to remind the public that we live in a desert, and we do need to go forward with this. We need to increase our water supply, or our reliability,” Pleasanton Vice Mayor Arne Olson said during the May 15 City Council meeting, adding that he’d like to see a potable reuse project pursued through a new Tri-Valley joint powers authority.

“I believe we’re in a period that single-use water, single usage of water, is done and over with, whether recycling or potable reuse. Moving forward in the future, the reliability factor and eventually the need for more water, it’s upon us to make these decisions now,” Councilman Jerry Pentin added.

The Pleasanton council voiced support for more technical studies and a more updated evaluation of the region’s water supply to help them make more informed decisions about the six project alternatives identified in the feasibility study.

Pleasanton leaders also made it clear they want their voters to weigh in at some point in the process, either earlier on with a ballot question about supporting the general concept or later when a final project proposal is available to take to the polls.

Councilwoman Karla Brown spoke about the need for more public input in the process, even before a possible citywide or regionwide vote.

“Check in with the public, because if we’re spending a lot of time and effort — staff and electeds and Zone 7 and contractors — for something the public absolutely isn’t ready for, then we try it again later,” she said.

Brown’s comments alluded to a major sticking point for potable reuse projects: public support for treating wastewater for use as drinking water — or overcoming the stigma or the so-called “ick factor.”

The Tri-Valley study stems from the need to look into other alternatives for long-term water supply options, according to the Zone 7 Water Agency, the wholesale water retailer serving the cities of Pleasanton and Livermore, along with Dublin San Ramon Services District (DSRSD) and Cal Water’s Livermore division. Currently, 80% of Zone 7’s water comes from the Sacramento-San Joaquin River Delta, a fact board members and staff alike repeated multiple times at the agency’s May 16 board meeting when Zone 7 directors received the report.

“Potable reuse” is recycled water that has been “safely incorporated into potable water supplies,” according to the feasibility study. Specifically in the context of this study, the original water source is “derived from wastewater effluent.”

Lydia Holmes from Carollo Engineers, presenting to Pleasanton and Zone 7 last month, stressed that potable reuse systems in California create safe drinking water and are protective of public health.

The water used for recycling goes through multiple steps: ultrafiltration, reverse osmosis, granulated activated carbon, a UV advanced oxidation process and an engineered storage buffer with Cl2 added. Each stage treats the water for different contaminants, including solids, protozoa and bacteria, viruses, salts and chemicals and contaminants of “emerging concern.”

California law regulates how potable reuse can be implemented into the water supply.

Currently, the state has approved potable reuse for groundwater augmentation or recharge (in use most notably in Orange County), in which purified recycled water is used to replenish a groundwater basin or aquifer that has been identified as a water source for a public water system, according to the study. This year, the state also approved regulations for reservoir water augmentation.

And the state is presently working to allow for raw water augmentation, with regulations expected to be in place by 2023. This method refers to the placement of purified recycled water into pipeline or aqueduct systems that “deliver raw water to a drinking water treatment plant that provides water to a public water system,” the study says.

The Tri-Valley agencies are essentially considering the groundwater and raw water augmentation options.

In determining the feasibility of potable reuse, the Carollo Engineers study looked into different possibilities for water sources, treatment plant sites and the water’s final destination locations.

The study identified two water sources: the Livermore Water Reclamation Plant and the DSRSD wastewater treatment plant. Both sites already have existing non-potable recycled water irrigation programs.

Staff identified five different locations as possible treatment sites, using criteria including available space, proximity to source water and end uses, and site accessibility.

The options include DSRSD space currently being used for dedicated land disposal, the Livermore plant in abandoned on-site facultative sludge lagoons, Mocho near the existing Zone 7 demineralization facility, the Pleasanton Corporation Yard and the Chain of Lakes, an ongoing project to convert depleted quarry sites into lakes that can be used for water-related purposes by the agency.

And in terms of the water’s final destination, the study has so far pinpointed three possible end uses for the purified water: groundwater augmentation through injection wells in two locations, groundwater recharge at one of the Chain of Lakes sites, and through raw water augmentation through Chain of Lakes to the Del Valle Water Treatment Plant.

The feasibility study found the project alternatives could supplement local water supplies by 5,500 to 10,000 acre-feet per year, with the options costing between $103 million and $222 million for construction, and then $6.5 million to $9 million annually for operations.

Though consumer costs are uncertain at this point, the study roughly estimated the use of potable reuse would add $10-$15 to the average household bill.

Even with the feasibility study in-hand, a local potable reuse operation would take at least eight years to come to fruition — assuming the agencies agree to move forward with a project.

But for now, the Tri-Valley agencies support collecting more data to help them make that future decision.

Overall, the Zone 7 board members said May 16 they were in favor of investigating the use of potable reuse.

Director Angela Ramirez Holmes raised the point that greater water conservation efforts statewide could limit the supply of source water to be used for the potable reuse.

“You hit on one of the issues that we’re going to investigate further,” consultant Amparo Flores said. “As indoor use drops, then we’re going to have less water available to recycle, to use for potable reuse applications.”

Pleasanton City Manager Nelson Fialho noted the next phase of analysis will include updating the region’s water demand and supply data to assess the current need compared to before or during the serious drought.

“The city of Pleasanton recognizes the need to plan for the future and explore the latest technologies that can help us weather any subsequent extreme drought situation,” Fialho said after the council meeting. “And we will be thorough and deliberative throughout this process and look forward to learning more as we move forward.”

A community survey was conducted in January, and according to staff, 55% of respondents supported supplementing water supplies with purified recycled water, and 55% would support a $5 monthly increase in their water bills. Respondents who opposed the potable reuse cited cost as the biggest barrier.