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View responses to frequently asked questions related to Central Coast Blue. Reponses are routinely updated based on community interests and available information.

For questions not addressed below, contact CCBRRWA General Manager at


Download a printable version of Central Coast Blue FAQs below:

What is Central Coast Blue?

Central Coast Blue is a regional water reuse project that will create a new, local, drought-resilient water supply and protect the local groundwater basin from seawater intrusion. The program includes construction of an Advanced Water Purification Facility (AWPF), where water from Pismo Beach’s Wastewater Treatment Plant is purified using state-of-the art technologies before being injected into the groundwater basin. This collaborative effort is a partnership between the cities of Arroyo Grande, Grover Beach, and Pismo Beach that will benefit Southern San Luis Obispo County for generations.

Who is participating in Central Coast Blue?

Check back soon for updated information!

Why is Central Coast Blue needed?

Central Coast Blue will protect our groundwater basin from seawater intrusion and provide a drought-resilient water supply for the region. Southern San Luis Obispo County relies on three water sources to meet its diverse needs, these include local groundwater, surface water from Lopez Lake, and imported water from the State Water Project. However, Prolonged drought and changing environmental conditions have dramatically impacted southern San Luis Obispo County’s water sources. Projections by San Luis Obispo County indicate that Lake Lopez would reach a minimum pool condition in 2024, with no water available to downstream users. The State Water Project is an increasingly unreliable water source with the average allocations declining steadily over the past two decades. Additionally, extensive monitoring has shown early signs of seawater intrusion. Currently, the cities of Arroyo Grande, Grover Beach, and Pismo Beach cannot pump their full groundwater entitlement without risking seawater intrusion.

What are the benefits of Central Coast Blue?

Central Coast Blue will protect our groundwater basin from seawater intrusion, provide a new drought-resilient water supply for the region, and increase local control of our water resources. The program will produce up to 3,500 AFY of new local water supply. Phase I will provide up to 900 AFY, increasing municipal groundwater supplies by nearly 30%. Phase II is expected to add up to 2,600 AFY to the basin. Groundwater Protection: Central Coast Blue protects the local groundwater basin from seawater intrusion by creating a freshwater barrier using purified recycled water. Drought Resilient: Central Coast Blue creates a new, drought-resilient water supply for the region by capturing lost water and using it to recharge the Santa Maria Groundwater Basin. Local Supply: Central Coast Blue reduces the region’s reliance on unreliable imported water. Water Reuse: Central Coast Blue recovers and reuses a valuable water resource that is currently being discharged to the ocean. Regional Collaboration: Central Coast Blue leverages shared resources from three cities to minimize financial impact for ratepayers and maximize the benefits for the region.

How does Central Coast Blue work?

Treated wastewater from Pismo Beach’s Wastewater Treatment Plant will be sent to a new Advanced Water Purification Facility (AWPF), where the water will be treated to meet drinking water standards. Purified water is injected into the Santa Maria Groundwater Basin to protect against seawater intrusion and replenish the community’s water supply. For more than 40 years, this scientifically proven process, known as potable reuse, has been used throughout California in communities such as Monterey, Los Angeles, and Orange County, as well as within communities around the world.

What are the program components?

Phase 1 of the program includes the construction of an Advanced Water Purification Facility (AWPF), eight groundwater wells, and two miles of pipelines. In coordination with Phase 1, the City of Pismo Beach plans to construct a new production well to replace an existing failing well. This component will be fully funded by Pismo Beach. Phase 2 of the project would include an expansion to the AWPF to purify water from the South San Luis Obispo County Sanitation District (SSLOCSD) Wastewater Treatment Plant. Up to three additional injection wells and up to six additional monitoring wells would be constructed in Phase 2 along with interconnecting pipelines. The schedule for Phase 2 of the project has not been established. Phase 1 is a stand-alone, independent project and is in no way contingent upon Phase 2, which may be considered and constructed should additional water supply from SSLOCSD be needed in the future.

How must does the program cost?

Construction of Central Coast Blue is estimated to cost between $134 and $159 million in 2024 dollars. For comparison, the Lake Lopez Reservoir Project cost $16.5 million to construct in 1969, equivalent to $140 million in 2024 dollars. A $26 million retrofit to the dam was completed in 2002 and a $26 million upgrade to the Lopez Water Treatment plant was constructed in 2008, equivalent to $82 million in 2024 dollars.

Why did program costs increase?

The estimated cost of the project increased from $28 to 50 million in 2019 to between $134 and $159 million in 2024. The cost increases are due to additional project features identified as the design progressed and post-pandemic inflation in the construction market. Cost increases have affected all sectors of the economy and are not unique to the construction market or public infrastructure projects. Due to continuing inflationary factors, project delays may lead to further project cost increases.

How is Central Coast Blue funded?

Central Coast Blue is funded by a combination of grants, low-interest loans, and ratepayer revenues. It is expected that up to 50% of construction costs will be funded by state and federal grants. Central Coast Blue costs are shared among the cities of Pismo, Grover Beach, and Arroyo Grande and are based on a collaborative cost-share agreement. Pismo Beach is responsible for 39% of program costs, with Grover Beach and Arroyo Grande covering the remaining 36% and 25%, respectively. Each city will receive water supply benefits proportional to its capital investment.

What is the program timeline?

In consideration of the increased construction cost estimate, the partner agencies have paused design and permitting while they reassess their water supply needs, risks, and options. If the partner agencies decide to move forward with the project, construction could begin in 2025 and be completed in 2028.

Additional Community Questions

What is the water supply benefit of Central Coast Blue?

  • Injecting purified recycled water into the local groundwater basin will replenish groundwater supplies and create a drought-resilient solution that is much less dependent on precipitation than the region’s other water supplies. This water source would continue to flow even when other sources have become unreliable.

  • Treated wastewater – currently discharged to the ocean in Oceano – will be diverted and purified before injection into the groundwater basin. Up to 900 acre-feet per year (AFY) of new water supply will be injected into the groundwater basin, enough to meet the annual needs of approximately 11,000 residents. 

  • Injecting purified water through coastal injection wells raises groundwater levels, creating an intrusion barrier that prevents seawater from moving inland and contaminating groundwater supplies. 

  • Based on the hydrogeology of the basin, a seawater intrusion barrier will allow more groundwater to be extracted than what is injected. Groundwater modeling has indicated that injecting 900 AFY of purified water along the coast will allow pumping 1,420 AFY of groundwater beyond baseline levels without increasing the risk of seawater intrusion. 

Reference: Phase 1B Groundwater Model Report

Who controls local water rights?

  • The rights to pump groundwater from the Santa Maria River Valley Groundwater Basin (Basin) have been in litigation (adjudication) since the late 1990s. The 2005 Stipulation for the Santa Maria Groundwater Basin Adjudication (2005 Stipulation) and the January 25, 2008, Judgment After Trial (2008 Judgment) established requirements and goals for management of the entire Basin. The Northern Cities Management Area (NCMA) was established by the Superior Court of California, County of Santa Clara as one of the three separate management areas within the Basin.

  • The collaborative water supply management approach of the NCMA Agencies (Arroyo Grande, Grover Beach, Oceano Community Services District, and Pismo Beach) was recognized by the Court and incorporated into the 2005 Stipulation, which was agreed upon by numerous parties, including the NCMA Agencies. The approach was then adopted by the Court in its 2008 Judgment.

  • Water rights are defined in the adjudication and overseen by the court. The NCMA Agencies collectively manage the local groundwater basin according to a Management Agreement. The NCMA Technical Group (TG) currently contracts with WSC, GSI Water Solutions, and its subconsultant partner, GEI to serve as staff extension to assist in managing the water supply resources, conduct quarterly groundwater monitoring and sampling tasks, evaluate water demand and available supply, identify threats to water supply, and help prepare the TG’s annual report. This structure was supported in the 2005 Stipulation which states, “The Monitoring Parties may hire individuals or consulting firms to assist in the preparation of the Monitoring Programs and the Annual Reports.”

  • Central Coast Blue will not change the existing groundwater entitlements established by the adjudication. Existing groundwater entitlements can only be changed by the courts through a legal process. Purified water injected into the basin would be considered “New Developed Water” and the right to use it would be proportional to each agency’s financial contribution to the project. Groundwater pumping by all basin pumpers will still be subject to the adjudication and NCMA Agencies’ Management Agreement.

  • The NCMA TG meets monthly to coordinate items relevant to basin management.


Is seawater intrusion really a threat?

  • The potential for seawater intrusion in the Santa Maria Groundwater Basin is an ongoing concern dating back to the 1950s. The California Department of Water Resources (DWR) studied seawater intrusion in the late 1960s and published a report with their findings in 1970. This report identified the potential for seawater intrusion in the Paso Robles and Careaga Aquifers (the local deep aquifers used for municipal water supply). The 1970 report found that seawater intrusion in those aquifers was not an immediate problem but was likely occurring offshore and could, eventually, reach inland wells. The report recommended local agencies monitor the coastal sentry wells which would “serve to warn local water agencies when intrusion begins so that corrective measures can be taken in time to preserve the basin.”

  • A lowered nitrate drinking water standard by the CA Department of Health Services in the late 1960s and the threat of seawater intrusion were the primary drivers behind the construction of Lopez Lake.

  • In 2009, seawater intrusion was detected in Sentry Wells 32S/13E-30 N02 and N03 (located on Pier Avenue in Oceano). The 2009 NCMA Annual Report describes the conditions and response actions taken by the NCMA Agencies which included collectively and aggressively decreasing groundwater pumping, reestablishing the natural outflow of groundwater from the basin to the ocean and preventing the advance of seawater intrusion. 

  • An indicator of whether stakeholders are successfully averting the threat of seawater intrusion is the groundwater elevation in the coastal NCMA sentry wells. The average water elevations of three sentry wells make up the Deep Well Index which was developed by the NCMA in 2007 to gauge the ability of the aquifer to withhold potential landward migration of seawater. A Deep Well Index value above 7.5 feet generally indicates that sufficient freshwater is flowing offshore to prevent seawater intrusion. Historically, a prolonged period in which the Deep Well Index level is below 7.5 feet results in groundwater conditions conducive to seawater intrusion. 

  • The NCMA Agencies’ groundwater entitlements from the basin equal 4,330 acre-feet per year (one acre-foot is enough water for about 12 people for one year). When seawater intrusion occurred in 2009, the NCMA Agencies were pumping an average of 3,200 acre-feet per year. In recent years, NCMA Agencies reduced pumping to about 750 acre-feet per year. Despite the significant reductions in pumping, the Deep Well Index dropped below the 7.5-foot target during the latest drought, reaching a low of 4.4 feet in September 2022.


How will Central Coast Blue impact disadvantaged communities, as defined by Senate Bill 1000: The Planning for Healthy Communities Act (SB 1000)?

  • For the purposes of SB 1000, “Disadvantaged communities” are defined as either: 

    • An area identified by the California Environmental Protection Agency pursuant to Section 39711 of the Health and Safety Code; or 

    • An area that is a low-income and that is disproportionately affected by environmental pollution and other hazards that can lead to negative health effects, exposure, or environmental degradation. 

  • The California Environmental Protection Agency considers communities with CalEnviroScreen 4.0 assigned scores in the 75th to 100th percentiles as “disadvantaged communities.” All project area census tracts received scores less than the 50th percentile and are therefore not considered disadvantaged communities per Section 39711 of the Health and Safety Code.

  • A “low-income area” is defined as “an area with household incomes at or below 80 percent of the statewide median income or with household incomes at or below the threshold designated as low income by the Department of Housing and Community Development’s list of state income limits adopted pursuant to Section 50093.” Based on U.S. Census data, as of July 1, 2023, the median household income of Oceano ($73,084 from 2018-2022) is below 80% of the statewide median household income ($91,905 from 2018-2022). Therefore, Oceano is considered a low-income area.

  • Project impacts were studied for the 2021 Environmental Impact Report (EIR) and the 2023 Addendum to the EIR. The certified EIR determined the Original Project would result in potentially significant environmental justice impacts due to localized construction and operational impacts related to air pollutant emissions, the use of hazardous materials, noise, and traffic. However, with implementation of Mitigation Measures AQ-2(a), AQ-2(b), HAZ-1(a), HAZ-1(b), N-1, N-2, N-4, and T-1 outlined in the certified EIR, the project would not result in disproportionately high and adverse impacts to disadvantaged communities.

  • Phase 1 of the project includes the construction of one injection well and approximately 1,200 feet of pipeline within Oceano streets.

  • The NCMA Agencies are evaluating opportunities to engage residents who would be impacted and the community as a whole.


How will the project impact Grover Beach roads?

  • Phase 1 facilities proposed for construction within Grover Beach include approximately 5,500 feet (1.1 miles) of pipeline within Grover Beach streets. 

  • Pipeline alignments were selected to avoid utility conflicts, reduce pipeline lengths and construction cost, and minimize impacts to recently repaved streets.

  • In total, the equivalent of only two blocks of recently repaired streets will be affected. These streets will be fully restored once pipelines are installed. The Phase 1 pipeline routes are shown on the map linked below.

Reference: Map of Proposed Facilities

But the drought is over – why do we need a water supply project?

  • California droughts are cyclical. The state predicts that hotter and drier weather could diminish existing water supplies by up to 10% by 2040.

  • While recent precipitation has temporarily improved water supply conditions, drought conditions will recur. Temporary improvement to our local water supplies has afforded time to prepare for future droughts.

  • In December 2022, San Luis Obispo County projected that, even with average rainfall, Lopez would reach minimum pool conditions by June 2024 at which point all municipal water deliveries would cease.

  • The Northern Cities Management Area Technical Group (NCMA TG) partner agencies are evaluating the most cost-effective water supply alternatives to prepare for subsequent droughts. 


Why don’t we capture stormwater instead? 

  • Potential groundwater replenishment options for the Northern Cities Management Area (NCMA) of the Santa Maria River Valley Groundwater Basin were evaluated and included in an appendix to the San Luis Obispo County Regional Recycled Water Strategic Plan prepared in 2014. The study found that the potential areas for surface recharge were not well defined, in part because the target aquifers for municipal supply wells are at significant depth beneath surficial dune sand and/or alluvium. More detailed studies are needed to define areas where surface recharge can effectively migrate vertically downward through the surficial sediments into the underlying aquifers that supply municipal wells.

  • San Luis Obispo County approved a Stormwater Resource Plan in 2020 to identify and prioritize stormwater and dry weather runoff capture projects. The plan identified four proposed stormwater infiltration projects within the NCMA. These proposed projects have a combined estimated annual infiltration capacity of 26 acre-feet. Construction on one of the four projects identified began in November 2023 at Oceano Elementary School. 

  • Purified water injected into the groundwater basin is expected to average up to 900 acre-feet per year, 35 times more than the combined yield of the four stormwater projects.

Reference: San Luis Obispo County Stormwater Resource Plan

Is Central Coast Blue experimental?

  • Advanced purified water is a proven and effective method of providing safe drinking water, and purified water is often safer than other water sources.

  • California treatment plants delivered more than 700,000 acre-feet of recycled water (of all types) in 2021, according to the State Water Resources Control Board.

  • Similar California projects include:

    • Pure Water Monterey (Monterey)

    • Leo J. Vander Lans Advanced Water Treatment Facility (Long Beach)

    • Albert Robles Center for Environmental Learning (Pico Rivera)

    • Orange County Water District Groundwater Replenishment System (Fountain Valley)

    • Edward C. Little Water Recycling Facility (El Segundo)

    • Pure Water Soquel (Soquel Creek)


Water Rights
Seawater Intrusion
Grover Roads
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