Project Description

Why is the project needed?


The Monterey Peninsula currently receives the majority of its water from the Carmel River. To protect the threatened species that live in the river, the state of California has limited the amount of water we can use. It has ordered a “ramp down” schedule to reduce our reliance on the river to less than half of what it is today. Our only other current source of water – the Seaside Groundwater Basin – is also under a court-ordered reduction schedule. This is to protect the basin from overuse and prevent seawater from contaminating fresh water. Currently, the water use for residents of the Monterey Peninsula is among the lowest in the state. The ordered cutbacks to our existing water supplies cannot be met without a replacement source of water. To address these issues, California American Water submitted an application to the California Public Utilities Commission for the Monterey Peninsula Water Supply Project in April 2012.

Project Components

  • Desalination

  • Aquifer Storage and Recovery

  • Pure Water Monterey: A groundwater replenishment project


Desalination: The Monterey Peninsula Water Supply Project consists of sub-surface slant intake wells, a desalination plant, and related facilities including source water pipelines, product water pipelines and brine disposal facilities.

Aquifer Storage and Recovery: California American Water will expand its current ASR project – a partnership with the Monterey Peninsula Water Management District – which captures excess winter flows from the Carmel River for storage in the Seaside Aquifer and withdrawal during the dry, summer months. Winter flows are considered excess only when they exceed what is needed to protect the river’s threatened population of steelhead.

Pure Water Monterey: The proposed Pure Water Monterey project, a partnership between Monterey One Water and the Monterey Peninsula Water Management District, recycles wastewater through an advanced treatment process. The resulting highly purified drinking water will be injected into the Seaside groundwater basin.




Key features of the project include:

  • The desal plant will seek to employ energy recovery devices to lower the plant’s power consumption.

  • Slant wells draw water from under the sea floor, past the average high tide line and avoid the impacts to marine life posed by open ocean intakes.

  • The brine resulting from the desalination process will be discharged to the ocean through the Monterey Regional Water Pollution Control Agency’s existing outfall. 

  • Construction of a 7-mile pipeline to deliver water to the Monterey Peninsula from the desal and PureWater Monterey projects has already been constructed

  • The Pure Water Monterey project is expected to yield 3,500 acre-feet annually and be online at the end of 2019.

  • Working with Monterey Peninsula Water Management District, we will expand our current Aquifer Storage and Recovery project, which captures excess winter flows from the Carmel River for storage in the Seaside Aquifer and withdrawal during the dry summer months. We will construct three additional ASR wells, which will add an average annual capacity of 900 acre-feet.

With continued water conservation efforts, these projects will create a reliable water supply portfolio for the Monterey Peninsula. We will avoid fines and penalties from the state and provide environmental benefits to the Carmel River and Seaside Aquifer.

Project Timeline






Final EIR/EIS 





SWRCB CDO Milestone:
CPCN approval of MPWSP



CCC CDP Decision 


Start of desal project construction



SWRCB CDO Milestone:
Start desal construction


GWR Water available



SWRCB CDO Milestone:
Complete one well plant foundation

Storage basin excavation

25% transmission PL



SWRCB CDO Milestone:
Complete 50% wells mechanical storage

Water tanks

50% transmission PL


SWRCB CDO Milestone:
Substantial completion water in service

Q4 2020 - Q2 2021
Desalination facilities commissioning and start-up window

Project Cost

Total Cost = $322 Million

6.4 MGD capacity plant

Subsurface Intake - return facilities

$79 million 

Desalination plant

$115 million 

Pipeline facilities

$128 million