Monterey Canyon—one of the world’s deepest submarine canyons—may soon become the source of water for a proposed desalination plant in central California.  While the canyon runs more than 3 kilometres deep into the earth, the proposed plant would draw water from an intake pipe located only 40 metres below ground level, and 300 metres from the shore.^[1]  This Deep Water Desal project would ameliorate the water shortages affecting the Monterey Bay region, which has no access to California’s State Water Project, a water system that includes reservoirs, aqueducts, and power plants (which store and deliver water to two-thirds of California’s population).^[2]  The water-scarce region suffers from a lack of reservoirs and low supplies of groundwater and surface water.^[3]

A primary advantage of drawing water from the canyon rather the ocean is that the facility will use 40 percent less energy than a conventional desalination plant.^[4] The water is very clean, and requires a less complicated pre-treatment as well as only one stage of reverse osmosis, rather than two stages.  The facility’s planners also hope to make the project carbon-neutral or carbon-negative, by creating a municipal power authority that will acquire all of its energy from renewable sources.^[5]  Additionally, the plant may be less harmful for marine life; the canyon from which the water will be drawn contains a quarter of the sea life compared to the shores of the Pacific.

Deep Water Desal aims to produce enough to serve 50,000 homes each year.^[6]  An environmental impact study is currently underway. But ultimately, the National Oceanic and Atmospheric Administration (NOAA) will have final approval over all proposals because part of the proposed facility is located inside the Monterey Bay National Marine Sanctuary.^[7]

^{Map of the Deep Water Desalination Plant at Monterey Canyon Credit: New Atlas}

OC WISE, a non-partisan organization committed to water use efficiency and increasing water supplies for Orange County, has released a new report concerning the proposed Huntington Beach Desalination Plant.^[8]  The report was authored by marine biologist Dr. Daniel Cartamil, who is currently a researcher at the Scripps Institution of Oceanography; it “concludes there is no scientific justification supporting the assertion that a Seafloor Infiltration Gallery (SIG) at a proposed Huntington Beach Desalination plant will significantly reduce mortality of marine life.”^[9]  According to Dr. Cartamil, “the construction and operation of a SIG at this location may have extensive and deleterious impacts to benthic habitat and organisms.”  The Appendix to the report, which was peer-reviewed and supported by 14 marine biologists, supports this assertion.

While the Coastal Commission will assess the proposed facility in early September, the report’s findings may inject new energy into the debate about the type of intake that the commission will require for the facility, particularly within the context of the updates for requirements for desalination plant intakes published in the 2015 California Ocean Plan.