ENCINITAS — By early next year, OMWD (Olivenhain Municipal Water District) should have a better idea if it makes economic sense to tap groundwater in its district.
Recently, the five-member OMWD board agreed to sign a contract with Stoney-Miller, an engineering firm that will study the underground geography of the city’s Lusardi formation. Once the analysis is finished, OMWD will consider installing a groundwater well.
OMWD believes groundwater in the Lusardi formation could make up a significant chunk of its potable and recycled water portfolio down the line.
“With the cost of imported water going so exorbitantly high, projects that would have been outlandish 20 years ago are viable,” said Kim Thorner, general manager of OMWD.
Stoney-Miller will look at two parts of the Lusardi formation — the San Elijo and San Dieguito basins.
Thorner said the San Elijo basin appears more promising. For one, that basin has an outfall, potentially making it easier to dispose of brine after the water has been treated. And the water quality in that basin is slightly better than that of San Dieguito.
Past geological surveys indicate that the San Dieguito basin, while not as encouraging, is still worth examining because it contains quite a bit of water.
“We don’t want to leave a stone unturned,” Thorner said.
OMWD’s interest in groundwater began a year ago, when a 40-foot drill rig towered over the northbound lanes of Interstate 5 near the San Elijo Lagoon for two months.
Scientists used the rig to drill a 1,200-foot test well. The results from the project showed that the water below was less salty than anticipated, meaning it would be cheaper to treat the water through reverse osmosis.
But due to the depth of the terrain, it was difficult to tap the groundwater below. That led OMWD to the Lusardi formation.
OMWD always planned on moving out of the lagoon in the event it was going to build a production well. However, the Lusardi formation is even further inland than the district was once considering.
“The rock formation is more shallow as you move east,” Thorner said, she added that the district could hit groundwater at 600 feet, rather than 1,200 feet.
Reaching the groundwater will be easier. Plus, the water quality in the Lusardi formation, parts of which is near Rancho Santa Fe Road, should be similar.
Consequently, the cost of installing a well on the Lusardi formation — expected to be around $250,000 — isn’t as high as putting one closer to the coast.
Also, OMWD wants to reassess whether the San Dieguito basin is fit for “indirect potable reuse.” That process involves injecting recycled water into the basin, where it’s naturally treated as it filters through sand and gravel. At a later date, the water is pulled up from the basin. From there, it’s treated once again — this time through reverse osmosis technology, rendering the water safe for drinking.
Joey Randall, a management analyst with OMWD, noted a facility in Orange County uses a similar method to produce potable water.
OMWD is the one of first districts in North County to pursue groundwater.
“Groundwater, like ocean desalination, is an alternative,” Randall said. “We need to be more creative since imported water costs so much.”
The Lusardi formation study will be released at the end of this year. Shortly after that, OMWD’s board will vote on whether it wants to build a test well on the Lusardi formation next year.
Assuming that’s successful, more wells and a full-blown groundwater desalination facility could launch as early as 2019.
The cost of the Stoney-Miller study: $168,000. OMWD applied for a $50,000 grant from the Metropolitan Water District of Southern California that could partially offset the price.
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