Skip to main content
Monterey Bay National Marine Sanctuary National Marine Sanctuaries Home Page National Oceanic and Atmospheric Administration Home Page

Resource Issues: Desalination and Water Supply Project Details
Monterey Peninsula Water Supply Project - #NOAA-NOS-2016-0156

Project Description

The purpose of the Monterey Peninsula Water Supply Project (MPWSP) is to replace existing water supplies for CalAm’s Monterey District service area. It comprises various facilities and improvements, including: a sub-surface seawater intake system; a 9.6-million-gallons-per-day (mgd) seawater reverse osmosis (SWRO) desalination plant; desalinated water storage and conveyance facilities; and expanded Aquifer Storage and Recovery (ASR) facilities. The desalination facility would be capable of producing 9.6 million gallons per day (MGD) of potable water on a 46-acre site located north of the City of Marina on unincorporated Monterey County property. The MPWSP proposes ten subsurface slant wells (nine new wells and conversion of an existing test well) to draw seawater from beneath the ocean floor in Monterey Bay to produce the source water for the desalination plant. The subsurface slant wells would be located primarily within the City of Marina, in the active mining area of the CEMEX sand mining facility. The slant wells would be approximately 700 to 1000 feet in length and extend beneath the coastal dunes, sandy beach, and the surf zone, terminating approximately 161 to 356 feet seaward of the Mean High Water line and at a depth of 190 to 210 feet below the seafloor. Up to 24.1 mgd of source water would be needed to produce 9.6 mgd of desalinated product water.

Under the proposed project, the desalination plant would generate approximately 13.98 mgd of brine, including 0.4 mgd of decanted backwash water. The brine would be discharged into Monterey Bay via a 36-inch diameter pipeline to a new connection with the existing Monterey Regional Water Pollution Control Agency’s (MRWPCA) outfall and diffuser located offshore.

For more information go to or

Previously Released and Archived Documents