For “The Water Squeeze” series of reports on water supply and planning, we’ve asked you what you wished you understood better about water issues. We heard from many people who wanted information about the environmental effects of the systems intended to improve supply, like desalination. KUSP’s Wes Sims reports on a plan to improve supplies on the Monterey Peninsula.
Salinas Valley farms rely heavily on the Salinas Valley Aquifer, 180-feet below the surface. But over-drafting and seawater intrusion threatens the viability of local agriculture. At the same time over-drafting of the Carmel River threatens the water security of cities on the Monterey Peninsula, which thrive on revenue from tourists who are drawn to hotels, restaurants and shops.
In order to comply with a state mandate to stop drawing water from the Carmel River, and pending approval from the California Public Utilities Commission, CalAm plans a $400 million desalination plant just north of Marina. The plant’s design includes some special characteristics that are a direct result of its location between the unique and delicate environment of the Monterey Bay and some of the world’s most productive cropland.
Richard Svinland, CalAm’s Director of Engineering explains that most desalination plants either use pipes that suck water straight from the ocean, “open-ocean intake” or they draw saltwater from wells reaching beneath the ocean floor, known as “sub-surface intake.”
Salt Water Drawn Not From the Ocean
“The debate on open-ocean intake versus sub-surface intake really comes down to impact on marine environment,” Svinland says.
CalAm’s project, in order to protect the bay, would not draw its salt water directly from the ocean.
“Open intakes have typically been known to have a high impact on entrainment and impingement of marine life,” he says.
“Entrainment,” meaning that when you draw water from the ocean from a big pipe, you can also pull in and kill fish and other sea life. (The technology may be improving – the desalination plant proposed by Santa Cruz and Soquel Creek Water District would use open intakes. Backers of that project argue their plant would not entrain sea life.) CalAm has opted to gather its salty water from wells, a choice partly influenced by government regulation.
“The National Marine Sanctuary guidelines for desal plants and the Coastal Commission and the impending plan for the state’s ocean plan, they all have a very strong preference for sub-surface intake,” Svinland says.
Svinland is saying that if you can get the salty water by boring so-called slant wells under the ocean floor rather than drawing in water directly from the sea, it’s considered more friendly to the ocean environment.
When Drilling, Protect Farmers’ Wells
CalAm’s plan to drill wells to supply the Monterey Peninsula drew close scrutiny from the agricultural community. Norm Groot is the executive director of the Monterey County Farm Bureau.
“We were concerned about how they were going to access source water and whether they were going to actually puncture the aquifer,” Groot says.
The water farmers use in their wells sits in layers of rock that extend down the Salinas valley toward the coast. So farmers have kept a close eye on the plan to make sure it won’t draw down the region’s already over-drafted wells. Right now he seems cautiously supportive of the plan.
“We think that this is a possibility that it could work here, based on the geology and what we know at this point.”
Finding the Water No One’s Using
The two layers the farmers draw from are called the “400-foot aquifer” and the “180-foot aquifer.” As CalAm’s chief engineer, Svinland believes the plant will be able to take its water from a source closer to the surface that the farmers aren’t using.
“We’ve said, ‘hey we’re going to try to make our slant wells work within the shallow dunes aquifer only,’” he says. “No one’s using that water for irrigation because it’s got a very high salt content.”
The goal is a project that can replace most of the water currently drawn from the Carmel River without hurting sea creatures or compromising Salinas Valley wells. A test-well seemed to show the plant could do so. In the spirit of making every possible use of this precious resource, that plan also involves filtering the peninsula’s waste water and using it to improve productivity of agricultural wells. More on that in our next report.
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