The Coast News Group
A drill rig that burrowed a 1,200-foot test well at the San Elijo Lagoon. With the well, scientists gauged the quality and quantity of groundwater. The rig and well were removed in December, and based on data gleaned, the Olivenhain Municipal Water District continued its commitment to groundwater desalination. Photo by Jared Whitlock

OMWD continues pursuit of groundwater

ENCINITAS — The OMWD (Olivenhain Municipal Water District) proved that there is more than a passing interest in groundwater desalination at its board meeting on Wednesday. 

In fact, the district took another step toward making groundwater a permanent part of its water supply. Last year, OMWD directed scientists to drill a 1,200-foot test well at the San Elijo Lagoon with the aim of finding useable water. Encouraged by the exploratory effort, OMWD is seriously considering installing another well several miles east of the first site.

Kim Thorner, general manager of OMWD, and others in the district, will scope out the exact location of the new well, ask for bids from contractors and present a contract for board approval in the next few months.

Ultimately, the district’s goal is to reduce its dependence on imported water.

“Our board of directors today was clear: we need to diversify our water portfolio, and groundwater could be a big part of that,” said Thorner after the meeting.

OMWD is weighing whether it should build a desalination plant and a series of wells a couple of miles east of the San Elijo Lagoon to produce water for years to come. OMWD estimates that the desalination plant and wells could generate up to 1.5 million gallons of water per day, making up as much as 10 percent of the district’s potable water, and also a chunk of its recycled water.

In October, researchers set up a 40-foot drill, which loomed over Interstate 5, at the San Elijo Lagoon to tap the first well. All traces of the project were removed once it wrapped up in December. But scientists are still combing over data from the pump test. Specifically, they’re interested in the quality and quantity of the groundwater.

To that end, the water was much less salty than originally anticipated. The groundwater’s salinity is around 1,800 parts per million, lower than the estimate of 3,000 parts per million, making treating the water through reverse osmosis cheaper.

The well only produced 50 gallons of water per minute, a third of what was originally expected. But because the ground was tougher than expected to drill into, researchers said that could have skewed the gallons per minute lower.

As such, it’s likely the test wasn’t truly reflective of the aquifer’s yield.

For this reason, OMWD commissioned more research. The findings concluded that OMWD should try and install another well in the area of the underground Lusardi formation, further inland than the district was once considering, near Rancho Santa Fe Road.

At this spot, the gallons per minute should be higher, and the water quality should hopefully be similar.

The Lusardi formation would only require drilling 600 feet, not 1,200, to reach groundwater. And the terrain isn’t as hard. Due to these factors, the cost to install the well — expected to be around $250,000 — isn’t as high.

Considered uncharted territory, there’s a lot of knowledge to gain from the Lusardi formation, Thorner noted.

“The new well will tell us the capacity of the underground basin (of the Lusardi formation) and where that water is coming from,” Thorner said.

While the first well was for monitoring, Thorner said the new one will be similar to a production well that would actually send water to a desalination facility.

Also, with the analysis, OMWD learned that the Lusardi aquifer isn’t connected to the San Elijo Lagoon. That means the Lusardi aquifer could “recharge” quicker after water has been pumped from it.

“That’s really good news, that opens up a lot of doors for us,” Thorner said.

Southern California water districts, including OMWD, are reliant on imported water, leaving them open to supply disruptions and price hikes. Currently, groundwater is more expensive than buying imported water. But Thorner said groundwater will make economic sense in the next 10 years as the cost of imported water rises.

Thorner said that if the OMWD board signs the contract, the well could be built before the end of the year, although that’s only a loose timeline.

OMWD’s attempt is the first foray into tapping groundwater in North County, a method employed by a few districts in the city of San Diego.

Based on the Lusardi well results, OMWD could build more wells and a desalination facility. The project could go online as early as 2018.

“I’m excited there’s this opportunity, and I’m eager to analyze it,” Thorner said.