Pure Water Monterey Logo

Carmel RiverMonterey County is isolated from state or federal water projects. This requires the region to rely solely on its limited, local water resources. For Monterey Peninsula residents and businesses, water historically came from two sources: 1) a local river (Carmel River) and 2) the ground (Seaside Groundwater Basin). Overuse of these two sources threatened water quality and habitats, leading to state and court-ordered reductions in these resources. To help address this challenge, Monterey One Water and its partners came together to create a drought-resistant and independent water supply: Pure Water Monterey (PWM).

Using a proven, multi-stage treatment process, Pure Water Monterey turns wastewater into a safe, reliable, and sustainable water supply that complies with or exceeds strict State and Federal drinking water standards. After production the purified water is used for groundwater replenishment of the Seaside Groundwater Basin.

Quick Stats

Source Water:

4 Types of Wastewater 

are diverted to Monterey One Water for treatment prior to purification: 1) municipal wastewater, 2) industrial processing water, 3) crop drainage water, and 4) urban stormwater runoff


3,500 Acre Feet Per Year 

of purified water produced to replenish the Seaside Groundwater Basin—a critical drinking water source for California American Water’s Monterey Bay service district


4-Step Purification Process

will use 1) Ozone, 2) Membrane Filtration, 3) Reverse Osmosis, and 4) Advanced Oxidation to turn Monterey One Water’s treated wastewater into purified water

Facility Size:

5 Million Gallon Per Day

Advanced Water Purification Facility will use a 4-step treatment process to produce water that meets or exceeds all strict State and Federal drinking water standards

One Water

The finite amount of water on our planet moves through a cycle of use and reuse in watersheds around the world. The one water approach views all water—drinking water, wastewater, storm water, greywater, and more—as a resource that must be managed in a sustainable manner. Pure Water Monterey relies on multiple entities to move through the cycle of reuse.


Monterey One Water (M1W)
Collects, treats, and purifies the wastewater before conveying and injecting the water into the Seaside Groundwater Basin

Groundwater Replenishment

Monterey Peninsula Water Management District (MPWMD)
M1W sells its purified water to the MPWMD who has jurisdiction over the Seaside Groundwater Basin 


California American Water (Cal Am)
The MPWMD then sells the purified water to Cal Am who extracts the water from the Basin and delivers it to its customers in its Monterey Bay service district
Repeat: For Cal Am customers connected to the regional system, purified water is utilized before heading back to M1W where the process begins again

View the One Water Process (PDF)