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Resource Issues: Desalination and Water Supply Project Details
Monterey Bay Regional Water Project - #NOAA-NOS-2015-0069

Project Description

DeepWater Desal, LLC has proposed a 25,000 acre-feet per year seawater reverse osmosis (SWRO) desalination facility and co-located seawater-cooled 150-megawatt computer data center campus located approximately 1.5 miles east of Moss Landing, Monterey County, and associated seawater intake and brine discharge pipelines that would extend west from Moss Landing Harbor to the upper reaches of the submarine Monterey Canyon and the north shelf, respectively, within Monterey Bay National Marine Sanctuary.

The main entrance for the SWRO Desalination Facility site would be through an existing gate located at the western terminus of Via Tanques Road near the intersection of Via Tanques and Dolan Roads. The co-located seawater-cooled computer data center campus, an electrical substation, and water storage facilities would also be located on the site.

The SWRO Desalination Facility would produce 25,000 AFY of potable water from 55,000 AFY of seawater. Ten SWRO pumps (plus one stand-by) would pump the seawater through the SWRO membranes. Each pump has a rated capacity of approximately 1,600 gallons per minute (gpm), and would have discharge pressures ranging from 850 to 1,000 pounds per square inch (psi).

A seawater-cooled computer data center campus would include four two-story data center buildings. The total land footprint for the buildings is expected to be approximately 775,000 square feet. Each building would contain servers and related equipment requiring some portion of the targeted 150 megawatt (MW) total power load. The distribution of data center equipment (e.g., computer servers) would be roughly proportional to individual building size; approximately 27 MW of server load for the smaller buildings and 52 MW for the larger buildings. In addition to computer server space, each building would include office space, including restrooms, kitchen space and storage. A loading and trash enclosure area would be located to the rear of each building. Each data center building would include a closed loop cooling system designed to provide air-conditioning to both office and computer server areas of the buildings. In lieu of the chiller units and evaporative cooling systems typically employed for building air conditioning, the data centers would reject heat to the cold seawater being pumped to the inlet side of the SWRO desalination facility. Each data center would draw a slipstream of water from the cold seawater line and run that water through a non-contact, tube-and-shell heat exchanger where it would collect heat from the data center cooling system. The heat exchanger tube sheet would be made of either titanium or an admiralty metal to avoid problems with corrosion. Assuming 150 MW of data center capacity, the incremental change in temperature to the intake seawater would be approximately 5 degrees centigrade. This heated seawater would then be pumped through the SWRO membranes, reducing the energy required to facilitate desalination.

DWD would use horizontal directional drilling (HDD) technology to install two 42-inch-diameter HDPE intake pipelines and two 36-inch-diameter steel discharge pipelines beneath the ocean floor for the intake of sea water and discharge of brine. The HDD drilling is proposed offshore of Moss Landing State Beach and should be about 50 feet below the seafloor or greater until about 500 feet from the discharge and intake points. At that point, the drilling head would turn up at a 4° angle until it breaches the canyon wall for the intake pipeline or the seafloor for the discharge pipeline.

Seawater would be extracted from the ocean through a passive, wedge wire-screened, low-velocity intake mounted at the terminus of the two 42-inch intake pipelines. As proposed, the intake would be located on the uppermost northern slope of the Monterey Submarine Canyon approximately 2,565 feet offshore of the ordinary high water mark (OHWM), northwest of the Moss Landing Harbor entrance, at a depth of approximately 100 feet.

The Applicant’s preferred location for mixing brine with seawater is at the deep discharge site located at a depth of 35 meters. Two 36-inch-diameter steel discharge pipelines will extend to the discharge location approximately 5,675 feet offshore from the OHWM near the terminus of the existing oil pipeline on the north flank of the Monterey Submarine Canyon. The section would extend out to a diffuser system that would be oriented orthogonal to the shoreline. The system would consist of five discharge risers emerging from a manifold and fitted with duckbill diffuser nozzles to assure rapid and thorough mixing with ambient seawater. The diffusers would be attached to a distribution manifold and spaced approximately 3 feet apart.

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Reviewed: April 11, 2024
Web Site Owner: National Ocean Service

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