Pure Water Monterey: A Groundwater Replenishment Project

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An environmental summary created by the ENVS 560/L Watershed Systems class at CSUMB.

Groundwater Replenishment Project System and Processes. The Paso Robles and Santa Margarita aquifers are the two main water supply aquifers within the Seaside Basin. Image from May 30, 2013 NOP [1]

Project summary

The Pure Water Monterey (PWM) Expansion Project is a collaboration between Monterey Peninsula Water Management District (MPWMD) and Monterey One Water (M1W), and its purpose is to supplement available water supply for parts of Monterey County. It was proposed in 2010, and exists now as an operational recycling plant in Marina and Seaside . It is currently an alternative to the California American Water Company desalination project (see Monterey Peninsula Water Supply Project). PWM will also simultaneously recharge the Seaside Groundwater Basin. The project is subject to an Environmental Impact Report (EIR) in accordance with CEQA, the draft of which has been reviewed (as of April 2016).[2] Before January 2014, PWM was titled the "Groundwater Replenishment Project." After December 2014, the project was officially given the name "Pure Water Monterey: A Groundwater Replenishment Project".[3] It is usually discussed and referred to as "Pure Water Monterey."


The PWM project proposes groundwater recharge of the Seaside Basin with Advanced Treated Wastewater through injection wells beginning in 2016, but officially started operations in February 2020. [4] The project goal is to provide Cal-Am with a supplemental water supply source separate from the Carmel River, Carmel Valley alluvial aquifer, and Seaside Basin. [1] Another benefit of the project is that it will decrease the impacts of groundwater overdraft and associated risks of seawater intrusion.[1] Cal-Am is pursuing alternative water supply due to the State Water Resources Control Board’s Cease and Desist Order to reduce diversions from the Carmel River, and to comply with the Seaside Basin Adjudication (see CalAm Use of Carmel River Groundwater Basin). [1] The PWM Project will produce 3,500 acre-feet per year (AFY) for sale to Cal-Am. Subsequently, Cal-Am will ideally be able to reduce the capacity of its desalination plant by the same amount, if it is built. [5]


Carmel Valley Aquifer and Seaside Groundwater Basin [6]
Retrieved April 7, 2014.

The PWM recycling plant is located in the cities of Marina and Seaside as well as some unincorporated areas of the Salinas Valley.[7] The project would replenish groundwater in the Seaside Groundwater Basin. The Seaside Groundwater Basin is located below Seaside, Sand City, Del Rey Oaks, Monterey and unincorporated areas of Monterey County, California.[7]


Since the 1960s, California American Water has been working on different ideas on how to maintain a steady water supply for the Monterey Peninsula. For example, in 1970, they proposed two more dams on the Carmel River, but didn’t build either of them. Five years later, the California Public Utilities Commission (CPUC) ordered a moratorium on new water hookups, and enacted water rationing due to a drought. The Monterey Peninsula Water Management District (MPWMD) was formed in 1978, with the purpose of working with Cal Am to protect and increase water supply – they are still serving that goal today. As early as 1987, Cal Am was accused of illegal summer pumping on the Carmel River, in a complaint submitted by the Carmel River Steelhead Association. Cal Am denied the complaint. Eight years after this, the State Water Resource Control Board (SWRCB) enacted Order 95-10 in 1995, which required Cal Am to reduce Carmel River pumping.

At this time, water tables in Monterey County had been on the decline, especially in 1995 when Cal Am transferred significant water supply from the Carmel River to the Seaside Groundwater Basin.[7] The increase in water drawn from the Seaside Basin has led to an overdraft of water and potential risk of seawater intrusion. [8] In 2006, the Seaside Basin was adjudicated by the California Superior Court to decrease the amount of water drawn from the Seaside Basin within three years, unless the appointed Watermaster board could secure more water sources. [7] To address these concerns Cal Am and the MPWMD jointly operate the Seaside Basin Aquifer Storage and Recovery (ASR) project that injects excess flow from the Carmel River into the Seaside Basin during periods of high flow. [8]

In 2009, the SWRCB revisited Order 95-10, extending the deadline for Cal Am to 2016.[9] Under Order 95-10, Cal Am had to reduce the amount of water is draws from the Carmel River by 70% from 2009 to 2016. [10] This goal was not met, and the current deadline is December 31, 2021. [11] The Pure Water Monterey Expansion Project Project is part of a portfolio of projects to address the decrease in water available from the Carmel River.


The general sequence of events for the PWM project is summarized by the initial plan from Monterey One Water and the Monterey Peninsula Water Management District plan, followed by the actual progression up to March 2020: (list from MPWMD plan or otherwise specified):[2]

  • 2013: 2013-2017 plan created by M1W and Monterey Peninsula Water Management District.
    • 2013: Begin CEQA assessment, and complete technical reports required for administrative draft environmental impact report (ADEIR and DEIR)
    • 2014: Continue creating DEIR and test plant wells
    • 2015: Release and certify final environmental impact report (FEIR)
    • 2016: Obtain final CEQA permits and consult with California Public Utilities Commision (CPUC). Begin construction.
    • 2017: Complete construction and begin testing facility [2]

The following progression is from the Pure Water Monterey Website, or otherwise specified. [12]

  • 9/9/2014: Monterey One Water, Monterey Peninsula Water Management District (MPWMD), Monterey County Water Resources Agency, agriculture, Marina Coast Water District and the City of Salinas meet to discuss project goals
  • 10/10/2014: Monterey County Board of Supervisors joins discussions, and is one of six agencies to approve a memorandum of understanding (MOU) to continue to discuss moving forward
  • 12/14/2014: Changes to Pure Water Monterey are opened to public comment
    • Changes include
      • 3,500 acre-feet per year of treated recycled water
      • 5,292 acre-feet per year to Monterey County Water Resources Agency for Castroville-area crops
      • Injecting 1,000 acre-feet per year into the Seaside groundwater basin
      • New pipeline for intake from Tembladero Slough
      • Inclusion of washwater from Salinas salad plants
      • Officially changing name to Pure Water Monterey
  • 12/18/2014: M1W files notice of preparation (NOP) of EIR
  • 4/22/2015: Monterey One Water and MPWMD release the DEIR for public comment
  • 5/7/2015: Monterey Peninsula Water Supply Project DEIR released for public comment.
  • 8/11/2015: Ord Community in south Marina would receive water alottment in pipeline going to Seaside groundwater basin
  • 8/27/2015: Cal Am petitions to push back deadline of Carmel River pumping reduction order
  • 9/28/2015: Final EIR completed, certification hearing set for October 8th
  • 10/12/2015: Final EIR certified
  • 1/22/2016: Monterey County Board of Directors and Peninsula Mayors Water Authority Board approves project purchase agreement
  • 1/21/2017: Monterey Peninsula water bills under Cal Am projected to increase 79% by March [13]
  • 3/9/2017: Central Coast Regional Water Quality Control Board approves permit for Pure Water Monterey expansion to inject tertiary-treated wastewater into Seaside groundwater basin [14]
  • 5/6/2017: Groundbreaking ceremony for recycling plant (May). [15]
  • 10/8/2017: Cal Am cutback deadline moved to December 31, 2021
  • 10/12/2017: Monterey Peninsula Water Management District manager Dave Stoldt says [Pure Water Monterey] expansion could meet the needs of the Peninsula before desalination project is built
  • 4/18/2018: Pure Water Monterey wins WaterReuse California award
  • 9/13/2019: Construction delays push back initial operations [16]
  • 11/7/2019: Draft environmental study for expansion released [17]
  • 12/20/2019: Pure Water Monterey environmental study public comment period extended through January 31 [18]
  • 2/5/2020: Pure Water Monterey expansion final state ok to begin delivering recycled water to Peninsula and Seaside groundwater basin in mid-February [4]

Water systems & facilities

Pure Water Monterey will artificially recharge the Seaside Groundwater Basin with tertiary treated wastewater. The treated wastewater will be injected underground using a series of shallow and deep injection wells.[1] The goal is to have injected water mix with existing groundwater for storage until Cal-Am begins to use the water to supply its customers. [1]

Water Sources

The project will use a combination of the following water sources (list from the GWR Notice of Preparation (NOP)):[1]


It will require the development of the following facilities (list adapted from the NOP):[1]

  • Source Water Conveyance Facilities: diversion and collection facilities, including pipelines and pump stations to convey source water to the new treatment facilities. Water sources to the treatment facility include: City of Salinas Treatment Plant water, Blanco Drain water, storm water from City of Salinas, effluent from the Regional Treatment Plant and Reclamation Ditch water,
  • Treatment Facilities: pretreatment facilities, a new Advanced Water Treatment Plant, and associated facilities at the existing Regional Treatment Plant site to filter and treat the source water,
  • Product Water Conveyance Facilities: pipelines, pump stations, and appurtenant facilities along one of two optional alignments to convey the treated water to the Seaside Basin, and
  • Replenishment/Recharge Facilities: pipelines, deep injection and shallow (vadose zone) wells, and backflush facilities to be located at one or both of two optional locations (coastal and/or inland recharge sites) within the Seaside Basin boundaries.

Laws, policies, & regulations

The development of Pure Water Monterey was subject to environmental laws and regulations by federal, state and local agencies. The project was be accountable to environmental review under the California Environmental Quality Act (CEQA), and various permits were required.


M1W prepared an Environmental Impact Report (EIR) in accordance with the California Environmental Quality Act (CEQA). M1W produced the draft and final EIR (April 2016).[3] They also prepared a notice of preparation (NOP) of a supplemental EIR on May 15, 2019. They released the Draft supplemental EIR on November 7, 2019. Public Comment closed on January 31, 2020. [19]

Required permits

A number of permits were required in the construction of the project. The following table is adapted from the original Notice of Preparation (NOP) and lists the regulatory agencies as well as the permits required for project construction.

Federal Agencies
U.S. Environmental Protection Agency Class V Underground Injection Control Program (Part C, Safe Drinking Water Act [SDWA])
Monterey Bay National Marine Sanctuary (MBNMS) Review and coordination of all RWQCB 404, Section 10, and NPDES permits
United States Fish and Wildlife Service Endangered Species Act compliance (ESA Section 7 consultation)
Fish and Wildlife Coordination Act (16 USC 661‐667e; Act of March 10, 1934; ch. 55; 48 stat. 401)
National Oceanic Atmospheric Administration Fisheries Endangered Species Act compliance (ESA Section 7 consultation)
United States Army Corps of Engineers Nationwide Section 404 Permit (Clean Water Act, 33 USC 1341)
Section 10, Rivers and Harbors Act Permit (33 U.S.C. 403)
Federal Aviation Administration Form SF 7460‐1 Notice of Proposed Construction & Alteration for Airport Airspace Aeronautical
State Agencies
California Public Utilities Commission Coordination regarding the MPWSP Certificate of Public Convenience and Necessity (Application No. 12‐04‐019)
State Water Resources Control Board, Regional Water Quality Control Board General Construction Activity Storm Water Permit (WQO 99‐08‐DWQ)
Water rights permit for development of new surface water diversions
Waste Discharge Requirements(Water Code 13000 et seq.)
401 Water Quality Certification (CWA Section 401)
National Pollutant Discharge Elimination System (NPDES) Permit (CWA Section 402)
California State Lands Commission Right‐of‐Way Permit (Land Use Lease)(California Public Resource Code Section 1900); Lease amendment
California Department of Fish and Wildlife Incidental Take Permits (CA Endangered Species Act Title 14, Section 783.2)
Streambed Alteration Agreement (California Fish and Game Code Section 1602)
California Coastal Commission Coastal Development Permit(Public Resources Code 30000 et seq.)
California Department of Public Health Permit to Operate a Public Water System (CaliforniaHealth and Safety Code Section 116525)
Approval for Recharge of Highly Treated Water
California Department of Transportation Encroachment Permit (Streets and Highway Code Section 660)
California State Historic Preservation Officer Section 106 Consultation, National Historic Preservation Act (16 USC 470)
California State University Monterey Bay Right of Way Agreements and/or Easements
Local Agencies
City of Salinas Electricity Power Purchase Agreement
Cities of Seaside and Marina, Sand City, Salinas (potential) Use Permits, encroachment/easement permits, grading permits and erosion control permits may be required pursuant to local city/County codes.
Fort Ord Reuse Authority Coordination with FORA for Right of Entry
Monterey Bay Unified Air Pollution Control District Authority To Construct (Local district rules, per Health and Safety Code 42300 et seq.) and Permit To Operate (Local district rules)
Monterey County Health Department, Environmental Health Division Well Construction Permit (MCC, Title 15 Chapter 15.08, Water Wells)
Hazardous Materials Business Plan (Health and Safety Code Chapter 6.95)
Hazardous Materials Inventory (Health and Safety Code Chapter 6.95)
Review of Discharges/WDR modifications
Variation on Monterey County Noise Ordinance (MCC 10.60.030)
Monterey County Public Works Department Encroachment Permit (Monterey County Code (MCC) Title 14 Chapter 14.040)
Monterey County Resource Management Agency Use Permit (MCC Chapter 21.72 Title 21)may be required pursuant to County codes.
Coastal Development Permit. (Public Resources Code 30000 et seq.)
Grading Permit (M.C.C., Grading and Erosion Control Ordinance, Chapter 16.08 – 16.12)
Erosion Control Permit (MCC, Grading and Erosion Control Ordinance, Chapter 16.08 – 16.12)
Monterey County Water Resources Agency Coordination/agreements for components within MCWRA‐controlled waterways and involving Castroville Seawater Intrusion Project and Salinas Valley Reclamation Project
Monterey Peninsula Water Management District Water System Expansion Permit (Monterey Peninsula Water Management District Board of Directors Ordinance 96)
Monterey Regional Waste Management District Electric Power Purchase Agreement
Seaside Basin Watermaster Permit for Injection/Extraction
Transportation Agency of Monterey County Easement
Water Agencies (other) Participation/purchase agreements
Private Entities
Landowners Land lease/sale; easements and encroachment agreements
California American Water Company (CalAm) Water purchase agreement with Monterey Peninsula Water Management District
PG&E Electric Power Will‐Serve Letter/Purchase Agreement

Resource goals


  • Quantity: Pure Water Monterey provides a secure source of fresh, potable water for the Monterey Peninsula under regular and drought conditions.[7] Specifically, it will provide 3,500 acre-feet of tertiary-treated water to residents on the Monterey Peninsula, and 5,292 acre-feet per year for irrigation on Castroville-area crops during regular water years. [12]
  • Additionally, the it will raise Seaside Basin water levels.[7]
  • Seawater Intrusion: It will also decrease the risk of seawater intrusion into the Seaside Basin.[7]
  • Contamination: If injected water is not treated to set standards there could be potential groundwater contamination issues.


  • It will decrease the amount of water that must be obtained through desalination in the future. A resultant decrease in the amount of energy and greenhouse gas emissions from the desalination process is expected.[7]
  • In 2015, the draft EIR report for the Monterey Peninsula Water Supply Project quoting an increase of 550% in energy regarding desalination pumping and treatment. This increase corresponded to a smaller plant than currently planned in 2020.
  • The Monterey Peninsula Water Supply Project would consume more energy. Pure Water Monterey is a lower-energy alternative. [20]


  • Surface Water: The project will decrease the amount of water drawn from the Carmel River,[7] which provides important habitat for threatened steelhead trout.
  • Pollution: Pure Water Monterey will decrease the amount of treated wastewater, storm water run-off, and water from the Blanco drain and Reclamation ditch and that flow into the Monterey Bay National Marine Sanctuary.

Future Projections

  • California’s climate is historically characterized by strings of drier, Mediterranean years with periodically-occurring years that are much wetter than average. These coincide with the El-Nino Southern Oscillation or the Pacific Decadal Oscillation in terms of annual precipitation. The wetter-than-average years inflate the average annual precipitation, which can be problematic if one is evaluating environmental policy by outlier years. Therefore, if this is not sufficiently calculated into future precipitation projections, environmental scientists may overestimate the amount of input into our surface and groundwater from rain. There is an MPWMD report that claims that Pure Water Monterey will adequately supply the Monterey Peninsula until 2043. [21]
  • There is an additional North Monterey County Drought Contingency report that says that as early as 2035, Pure Water Monterey alone will not be enough to supply the Peninsula's water demands. It asserts that the Monterey Peninsula Water Supply Project can provide a small surplus during normal and drought years. [22]




  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Original GWR Notice of Proposal. GWR NOP
  2. 2.0 2.1 2.2 Monterey One Water. Monterey Water Pollution Control Agency 2015 Memorandum, Published March 29, 2015. Retrieved April 5, 2020.
  3. 3.0 3.1 Previous GWR Website. Official GWR Website
  4. 4.0 4.1 Johnson, Jim. Pure Water Monterey Gets Final State Ok, Updated February 5th, 2020. Retrieved April 5, 2020.
  5. Renda, Matthew. Monterey Desalination Plant debated by California Coastal Commission. Published November 14, 2019. Retrieved April 5, 2020.
  6. Monterey Herald. Water Supply Project Monterey Herald May 2013
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 Cole, Jerry. The benefits of recycled water recharge to an over-drafted coastal groundwater basin
  8. 8.0 8.1 MPWMD Seaside Groundwater Basin ASR MPWMD Seaside Groundwater Basin ASR Accessed April 5, 2020.
  9. SWRCB Order 95-10 SWRCB WR 95-10 Published July 5, 1995. Accessed April 5, 2020.
  10. MPWMD. MPWMD FAQ on CDO Feb. 2011 Updated February 2, 2011. Accessed April 5, 2020.
  11. Coury, Nic. A look back and forward regarding the Monterey Peninsula's Water Supply Published November 28, 2019. Accessed April 5, 2020.
  12. 12.0 12.1 Pure Water Monterey. Pure Water Monterey in the News Updated 2020. Retrieved April 5, 2020.
  13. Johnson, Jim. Cal Am Water Bills to rise 79% for Monterey Peninsula, Published January 21, 2017. Retrieved April 5, 2020.
  14. Johnson, Jim. Central Coast Water Board Grants Recycling Project Basin Injection Permit, Published March 9, 2017. Retrieved April 5, 2020.
  15. Johnson, Jim. Pure Water Monterey hailed at May 2017 groundbreaking, challenges remain, Updated September 11, 2018. Retrieved April 5, 2020.
  16. Johnson, Jim.Pure Water Monterey Project Delays Continue, Updated September 16, 2019. Retrieved April 5, 2020.
  17. Johnson, Jim.Draft Environmental Study for Expansion Project Released Published Novemeber 7, 2019. Retrieved April 5, 2020.
  18. Johnson, Jim. Pure Water Monterey Expansion Environmental Study Review Extended Updated December 23, 2019. Retrieved April 5, 2020.
  19. Pure Water Monterey. Pure Water Monterey Website Updated 2020.
  20. Monterey Peninsula Desalination Plant Draft EIR Emissions
  21. Pure Water Monterey caps draft EIR Public Comment
  22. North Monterey County Drought Contingency Plan


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