Marina >> Starting Monday morning and continuing through much of the week, a helicopter will be flying low over a coastal section of Monterey County, sending pulses of electrical current underground.
The Marina Coast Water District-sponsored flights are part of a groundwater management effort aimed at assessing the extent of seawater intrusion in area water basins linked to the district’s water supply.
The helicopter will fly about 50-75 mph with instruments mounted on a large hexagonal frame that will employ electrical resistivity tomography technology, which sends the pulses of electrical current underground, to collect and record measurements down to about 1,000 feet below the surface. The information will be used to map groundwater aquifers and subsurface geology, and assess the level of seawater intrusion in the area.
Paso Robles-based Sinton Helicopters will oversee the helicopter flights over Marina, Castroville, Moss Landing and Salinas.
Electrical resistivity tomography was developed by Stanford professor Rosemary Knight, and has already been used to assess seawater intrusion along the Monterey Bay coastline, but not to this extent. The method is considered by some experts to be superior to drilling monitoring wells.
Marina Coast general manager Keith Van der Maaten said the data compiled during the flights will be processed and used by the district’s partners — Aqua Geo Frameworks and Stanford University’s Department of Geophysics — to produce a final report expected within 10 months. Van der Maaten said preliminary information should be available within a month.
The $250,000 project will be used to inform the district’s groundwater sustainability plan, Van der Maaten said, by providing a “more accurate” picture of groundwater quality and fill in key gaps in available data.
Van der Maaten said the report could also be used as a baseline to measure the impact of California American Water’s plans to pump brackish water from the Salinas Valley groundwater basin on the Cemex sand mining plant for a proposed desalination plant, and potentially show Cal Am is “mischaracterizing” the state of seawater intrusion south of the Salinas River.
Marina Coast has argued Cal Am’s desal plant feeder wells would negatively impact the district’s water supply and impact its ability to manage groundwater.
Meanwhile, on Tuesday, Marina-based Citizens for Just Water has planned a brief presentation on the data collection effort at 8:45 a.m. at Marina Municipal Airport, followed by observation of the apparatus setup.
Jim Johnson can be reached at 831-726-4348.
