Monterey Peninsula 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 Monterey Peninsula Groundwater Replenishment (GWR) Project, proposed in 2010, is a collaboration between Monterey Peninsula Water Management District (MPWMD), Monterey Regional Water Pollution Control Agency (MRWPCA), and California American Water Company (Cal-Am) to supplement Cal-Am water supply to the Monterey region (see Monterey Peninsula Water Supply Project). GWR 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] In January 2014, the GWR project was officially given the name "Pure Water Monterey: A Groundwater Replenishment Project".[3]


The GWR project proposes groundwater recharge of the Seaside Basin with Advanced Treated Wastewater through injection wells beginning in 2016. The project goal is to provide Cal-Am with a supplemental water supply source separate from the Carmel River and Carmel Valley alluvial aquifer. [1] Another benefit of the Groundwater Replenishment 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 Cal-Am Use of Carmel River Groundwater Basin). [1] The GWR Project will produce 3,500 acre-feet per year (AFY) for sale to Cal-Am. Subsequently, Cal-Am will be able to reduce the capacity of its desalination plant by the same amount.


Carmel Valley Aquifer and Seaside Groundwater Basin [4]

The GWR Project would be located in the cities of Marina and Seaside as well as some unincorporated areas of the Salinas Valley.[5] 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.[5]


Since 1987 water tables in the Monterey region have been on the decline, with a substantial drop in 1995 when Cal-Am transferred significant water supply from the Carmel River to the Seaside Groundwater Basin.[5] The increase in water drawn from the Seaside Basin has led to an overdraft of water and potential risk of seawater intrusion. [6] 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. [5] To address these concerns Cal-Am and 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.[7]

In 1995 Cal-Am was issued a cease and desist order (CDO) by the State Water Resources Control Board for drawing more water from the Carmel River than they were allocated.[8] In 2009 Cal-Am was issued another CDO for continuing to draw more water than allowed.[9] Under the CDO Cal-Am will have to reduce the amount of water is draws from the Carmel River by 70% from 2009 to 2016. [10] The Groundwater Replenishment 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 GWR project is (list from GWR website):[3]

  • 2013: Begin CEQA and pilot test facilities.
  • 2014: Complete CEQA, pilot plan testing, and develop final design criteria.
  • 2015: Prepare final design and obtain regulatory approvals/permits. Begin construction.
  • 2016: Construction.
  • 2017: Start up facilities (winter).

Water systems & facilities

The GWR Project will artificially recharge the Seaside Groundwater Basin with advanced, 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 GWR will use a combination of the following water sources (list from the GWR Notice of Preparation (NOP)):[1]


The GWR Project 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 GWR Project will be subject to many laws and regulations by federal, state and local agencies. The project will be accountable to environmental review under the California Environmental Quality Act (CEQA), and a number of permits will be required.


The GWR Project is required to prepare an Environmental Impact Report (EIR) in accordance with the California Environmental Quality Act (CEQA). The lead agency preparing the EIR is the Monterey Regional Water Pollution Control Agency (MRWPCA). MRWPCA has produced a draft EIR and is currently preparing the final EIR (April 2016).[3]

Required permits

A number of permits will be required in the construction of the GWR Project. The following table is adapted from the GWR Project 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: The GWR project may provide a secure source of fresh, potable water for the Monterey Peninsula under drought conditions.[5] Additionally, the GWR Project will raise Seaside Basin water levels.[5]
  • Seawater Intrusion: The GWR will decrease the risk of seawater intrusion into the Seaside Basin.[5]
  • Contamination: If injected water is not treated to set standards there could be potential groundwater contamination issues.


  • The GWR 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.[5]


  • Surface Water: The GWR will decrease the amount of water drawn from the Carmel River,[5] which provides important habitat for threatened steelhead trout.
  • Pollution: The GWR 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.




  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 GWR NOP
  2. GWR Project Update Mar. 2015
  3. 3.0 3.1 3.2 Official GWR Website
  4. Water Supply Project Monterey Herald May 2013
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 The benefits of recycled water recharge to an over-drafted coastal groundwater basin
  6. MPWMD Seaside Groundwater Basin ASR
  7. MPWMD Aquifer Storage and Recovery
  8. SWRCB WR 95-10
  9. SWRCB WR 2009-0060
  10. MPWMD FAQ on CDO Feb. 2011


This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.