A picture of seawater intrusion in Marina's aquifers is unveiled.

It was a presentation about a serious problem—seawater intrusion—but there was so much giddiness in the air it almost felt like a party. 

That's because the presentation confirmed the existence of a resource that, locally, feels more valuable than gold: freshwater. 

On Aug. 8, the Marina Coast Water District board of directors were presented with a preliminary report from the team of Stanford professor Rosemary Knight, which analyzes groundwater data taken by helicopter to create incredibly comprehensive maps of underground aquifers.

Called airborne electromagnetics, or AEM, the data is collected by a suspended, electrified ring hanging under the copter that creates a magnetic field up 1,000 feet below the surface, which in turn sends signals back through the ring. 

Marina Coast hired Knight's team earlier this year to complete the study for $250,000, and a helicopter collected the data in May. 

Last night was the first look at the results, and the board members and public alike were impressed by a subterranean picture that they had previously only been able to imagine, and which monitoring wells could never fully illustrate. 

The images are two-dimensional slices, from the surface to about 1,000 feet deep, with a spectrum of colors to illustrate salinity levels, with red being salty and blue being fresh. 

One big takeaway from the images was that the chloride levels in the aquifers—the Dunes aquifer, the 180-foot and 400-foot—were highly heterogenous, meaning that saltwater intrusion cannot be fully understood by sampling a scattering of wells.  

But the biggest takeaway from the data was that there is a considerable amount of freshwater in Marina's shallower aquifers—the Dunes and 180-foot—which runs counter to the conventional wisdom that the shallower aquifers in the region are all intruded by seawater. 

Following the Stanford presentation, hydrologist Curtis Hopkins gave his own PowerPoint interpreting AEM results, and also presented data that appears to indicate the salinity of the groundwater around the Cemex sand mine's dredge pond—a man-made saltwater pond just north of Cal Am's test slant well under the beach—is artificially spiking the salinity levels of the shallow groundwater in the area. 

According to a well sampling taken in June, the groundwater Cal Am's test slant well is pumping under the beach is about 84-percent saltwater, well below the target of 95-96 percent. 

Because law prohibits the export of any freshwater from the Salinas Valley Groundwater Basin, that means Cal Am would have to pump more groundwater to reach it's production targets, as it's only able to export the percentage that is desalinated saltwater.

That means higher energy costs, which in turn means a higher cost of water. With the cessation of the Cemex operation by the end of 2020—per a consent order Cemex recently agreed to with the California Coastal Commission—that means the salinity of the slant well water could drop even further, driving up the cost of water to a point that could threaten the viability of the project. 

MCWD General Manager Keith Van de Maaten says the intent of the study is not to kill Cal Am's project.

"We just want to be objective and face the facts," he says. "What we’ve already shown is that Cal Am has completely mischaracterized what is going on right now."

Van der Maaten points to the amount of freshwater revealed to be in Marina's shallower aquifers—Cal Am has long contended it's drawing from an impaired source—and the hope that freshwater can continue to act as a bulwark to further seawater intrusion. 

"There isn’t water you can pull into these slant wells from the groundwater basin without causing harm," he contends. "It’s a delicate situation on the coast, as we have shown, and any additional stresses isn’t going to make it better."

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Correction 8/9/17 (2pm): The original version of this story stated that presently, the source water for Cal Am's slant well was about 90-percent saltwater, which is what Monterey Peninsula Regional Water Authority Executive Director Jim Cullem said immediately following the Aug. 8 meeting. However, an Aug. 1 report shows that samples from the slant well taken in June put that number at 84-percent saltwater, and that the declining salinity is likely result of the past winter's abundant rainfall.