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Wastewater to wine? 

Experts say recycled water is fine for vines but public perception may lag

click to enlarge FINE FOR WINE? :  Warnings such as this one adorn areas where SLO City irrigates with recycled water. - PHOTO BY STEVE E. MILLER
  • PHOTO BY STEVE E. MILLER
  • FINE FOR WINE? : Warnings such as this one adorn areas where SLO City irrigates with recycled water.

Local vineyards pinched by drought and dwindling groundwater may get the opportunity, if they want it, to irrigate with water recycled from wastewater treatment plants.

The idea has bubbled up in a proposal for a new countywide water management plan, now being prepared by Carollo Engineers under a $685,000 contract approved by the San Luis Obispo County Board of Supervisors in April.

“The agricultural community, particularly for vineyard use, is beginning to pursue or at least accept recycled water as a beneficial and long-term supply,” the consultant’s report to supervisors stated.

Project manager Lou Carella confirmed that recycled water will be “a large component” of the new water management plan, adding, “But we haven’t drilled down what we’ll be doing with North County vineyards.

“I don’t know of any technical or regulatory reason why it wouldn’t work. But there is also a strong public perception issue. There are a lot of hurdles, including the economics and public perception,” Carella said in an interview from the firm’s Walnut Creek office.

If SLO County vineyards do go with recycled water, they wouldn’t be breaking new ground.

Seven vineyards in Napa Valley have been irrigated with recycled water from the Napa Sanitation District for years, according to the district’s general manager, Michael Abramson.
 
“The public perception issue is long since past,” he said.

Recycled water from the sanitation district’s wastewater treatment facility—highly treated and disinfected—is “excellent” for growing wine grapes, Abramson noted. It contains some plant nutrients, including nitrogen and phosphorus, so growers in Napa can cut down on fertilizer use, he explained.

It is also a reliable, drought-proof water supply that uses less energy and has a smaller “carbon footprint” than many potable water supplies, according to the Napa district’s website.

“Our recycled water receives tertiary treatment and disinfection. I’d have my kids swim in it. The only thing you can’t do is drink it.”

None of the Napa growers who have used recycled water have switched back to well water, said Abramson.
    Locally, the idea of irrigating wine-grapes with recycled water is “an interesting concept,” said Kris O’Connor, an irrigation expert and executive director of the Central Coast Vineyard Team, a network of about 300 local growers working on sustainable farming practices.

“There’s a lot to work out—the cost, water quality, and a pretty serious infrastructure issue in terms of the delivery,” O’Connor said. She also worried about the saltiness of recycled water, and whether using it would plug up drip irrigation systems.

“There haven’t been any serious conversations about using recycled water in vineyards here, but with the costs of water, there may be some acceptance,” she said.

Wine consumers are already embracing the concept of sustainable growing practices in SLO County vineyards. Fourteen local vineyards have received Sustainability in Practice Certification, she said, and their wines carry an SIP seal. The group’s consumer website, sipthegoodlife.org, includes details of their water-saving vineyard management.

A University of California study of recycled water’s suitability for vineyard irrigation focused on an unnamed Napa vineyard that has been irrigated solely with recycled water for eight years.

Soil samples from the vineyard did not show long-term salinity accumulation, according to the report. No extra risk of clogging drip irrigation systems was found, and trace elements and heavy metals were well below levels of concern. Organic grape growers can use recycled water in organically certified vineyards.

“Based on our results, there were no salinity or toxicity issues that would limit the use of this water for vineyard irrigation,” the study concluded.

Many Napa vineyards use around 100 gallons of water a year for each grapevine, according to the report, so irrigating the vines with recycled wastewater “helps to preserve the supply of potable water for human consumption.”

In Napa, a bigger issue is the cost of piping the water to more vineyards.

The price of a recycled water distribution system has been “a major obstacle to its use,” according to Abramson from the Napa Sanitation District. That district is looking for a combination of funding for a new recycled water pipeline to outlying vineyards, including state and federal grants, connection fees, and user fees.

As O’Connor of the Central Coast Vineyard Team said: “In the third year of a drought, nobody is more aware of the value of water resources than farmers. For some, irrigating with recycled water might make sense; for others maybe not. But it should at least be on the table.”

Contributing writer Kathy Johnston can be reached at kjohnston@newtimesslo.com.

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