Planning & Building

The purpose of this memorandum is to clarify and affirm how the County Department of Planning and Building (Department) applies the County’s Local Coastal Program (LCP) to development in Los Osos, considering recent correspondence from Coastal Commission staff.

Permitted Development in Los Osos

The County is currently accepting the following types of new permit applications for review:

• Construction and land use permit applications for remodels, expansions, additions, garages, and guesthouses on existing developed lots;
• Construction and land use permit applications for new residences outside the sewer service area that receive an intent-to-serve letter from their water purveyor or are served by a private well outside a water purveyor boundary until the Board of Supervisors approves an updated growth rate;

Individual water purveyors may not be providing water service for new primary residences.  Check with your water purveyor before starting the construction or land use permit application process.

Development applications for new structures with plumbing fixtures that use water from the Los Osos Groundwater Basin are required to retrofit plumbing fixtures in existing structures within the Los Osos Groundwater Basin to achieve a 2:1 offset of new water demand, per the County's Retrofit-to-Build Program.

On January 8, 1988, the California Regional Water Quality Control Board (RWQCB) imposed a building moratorium for the "Prohibition Zone" in Los Osos (now the sewer service area), which prohibited the County from issuing any permits for new on-site sewage disposal systems (commonly called "septic" systems) within the prohibition area until a community-wide wastewater treatment plant was completed to serve the area.

To find out if your property is within the Sewer Service Area/Prohibition Zone, use the map below.

Waitlist for Development of Undeveloped Parcels in the Sewer Service Area ("Waitlist")

Since undeveloped parcels in the sewer service area are unable to be developed due to the current 0% growth rate and permit limitations placed on the Los Osos Wastewater Project by the Coastal Commission, the County maintains a waitlist for development of these parcels ("Waitlist") until they are able to apply for construction permits.  The Waitlist was established in 1990.  To be added to the Waitlist, property owners pay a $32 admin fee per property and $500 deposit per dwelling unit.  Positions on the Waitlist are tied to the property and remain effective when properties are conveyed, but may not be transferred between properties.

Once development is allowed in the sewer service area, whether with the proposed 1.3% growth rate or any other growth rate above 0%, those on the Waitlist will be prioritized.  The County will notify property owners when they are eligible to apply for construction permits, and those property owners will have 90 days to [A] submit a complete construction permit application, or [B] request their position be deferred.  Property owners who choose to defer their position on the waitlist can notify the County when they are ready to submit a complete construction permit application and then proceed if the annual growth rate limit has not been met for the fiscal year or be prioritized for the next fiscal year. 

The Waitlist (for development of single-family and multi-family dwellings) and the request form to be added to the Waitlist are available at the following weblinks:

Waitlist (Single-Family Dwellings)

Waitlist (Multi-Family Dwellings)

Waitlist Request Form (Email to [email protected])

No construction permits are currently being issued for properties on the Waitlist.

The Los Osos Wastewater Project is complete.  The Los Osos Wastewater Project cannot serve undeveloped parcels until the County amends the Estero Area Plan - Los Osos Urban Area (hereafter referred to as the "Los Osos Community Plan" or "LOCP") to incorporate the following:

• [Water Resource Component]  A sustainable buildout target that indicatesthat there is water available to support such development (buildout) without impacts to wetlands and habitats
• [Habitat Conservation Component]  A community-wide Habitat Conservation Plan (HCP) for the long-term preservation of habitats of endangered species.

Note: Undeveloped lots have not been assessed fees for sewer connections.

The LOCP will provide the framework to allow new development in Los Osos.  On December 15, 2020, the Board of Supervisors approved and adopted the LOCP.  However, the Coastal Commission needs to approve and certify the LOCP before it takes effect.  A Coastal Commission hearing date is not yet scheduled.

The Board of Supervisors Adopted LOCP is available at the following weblink:

The Board of Supervisors Adopted LOCP

Due to historical water quality degradation of the Los Osos Groundwater Basin ("Basin"), new development is contingent to implementation of the Basin Plan for the Los Osos Groundwater Basin ("Basin Plan") and the County's Retrofit-to-Build program.  To ensure that growth does not result in further degradation of the groundwater basin, the County's Growth Management Ordinance serves as the tool for metering out residential construction permits (for more information regarding growth rate, see "Residential Growth Rate" section below).  In addition, the LOCP would only allow for the approval of new discretionary land use permits if the proposed development can be accommodated by the sustainable yield of the Los Osos Groundwater Basin without causing seawater intrusion (as identified in the Basin Plan and annual monitoring reports), unless the proposed development offsets the net increase in water demand at a 1:1 ratio or, for new structures, the 2:1 ratio required by the County's Retrofit-to-Build program.

Los Osos Groundwater Basin ("Basin")

The Basin is identified as a Level III severity.  The Basin is made up of several aquifer layers, underlying the Los Osos community and surrounding areas.  The Upper and Lower Aquifers are the main sources of municipal and domestic water supplies.  Nitrates from historic use of septic systems in Los Osos has caused the degradation of water quality in the Upper Aquifer, and in response, water purveyors increased pumping water from the Lower Aquifer.  However, the

increased groundwater extractions exceeded the sustainable yield of the Lower Aquifer in the western area, resulting in seawater intrusion.  The groundwater issues Los Osos faces pre-date the drought and the current development restrictions.

To address the groundwater issues, the County and water purveyors developed the Basin Plan (approved on October 14, 2015), a comprehensive groundwater management strategy to address problems faced by the basin, including seawater intrusion and elevated nitrate concentrations, and for restoration of basin water resources, while respecting existing water rights.

The Basin Plan established a sustainable yield estimate for the Basin and aims to maintain groundwater production at 80 percent or less of the sustainable yield estimate to provide a conservative buffer to account for uncertainty in the groundwater modeling assumptions. The sustainable yield is the maximum amount of water that may be extracted from the basin each year (a) using existing infrastructure, (b) without causing seawater to intrude further than the current extent, and (c) without active wells producing water with a chloride concentration exceeding 250 mg/L.

The current sustainable yield estimate for the Basin is 2,380 AF (BMC Annual Report, 2022). This is an updated sustainable yield estimate with more conservative groundwater modeling assumptions compared to the previous sustainable yield estimate of 2,760 AF (BMC Annual Report, 2021). The most recent (2022) groundwater production estimate (2,010 AF) is 84 percent of the current sustainable yield estimate (2,380 AF) and, as such, estimated groundwater production does not exceed the sustainable yield estimate.   

The Basin Plan infrastructure projects, along with their funding, fall into two phases.

     Infrastructure Projects:

• Phase 1 Infrastructure Projects intend to stabilize the Basin to serve current development with no or marginal future development
• Phase 2 Infrastructure Projects intend to increase the sustainable basin yield to allow new development and buildout of the Los Osos community

The Phase 1 Basin Plan Projects are fully funded and partially implemented.  The Los Osos Groundwater Basin Management Committee ("BMC") is responsible for implementing the Basin Plan and preparing annual reports documenting the status of infrastructure improvement projects, estimated sustainable basin yield, and monitoring data to evaluate Basin conditions.

The BMC Board of Directors is scheduled to hold regular meetings on the third Wednesday of every month, starting at 1:30 p.m.  Meetings are currently held remotely due to COVID-19 concerns (previously, meetings were held at the South Bay Community Center, located at 2180 Palisades Avenue, Los Osos).

For more information regarding the Basin Plan and BMC (including annual reports and meeting agendas), visit the following website:

     Los Osos Basin Management Committee Website

Residential Growth Rate

The County's Growth Management Ordinance ("GMO") requires the Board of Supervisors to approve an annual growth rate for the number of new dwelling units allowed to be constructed each fiscal year to ensure new residential development is appropriate based on the availability of community resources.  The GMO specifies that, each fiscal year, 65% of new dwelling units allowed are reserved for single-family dwellings and 35% of new dwelling units allowed are reserved for multi-family dwellings; while the following types of residential development would be exempt from the growth rate in Los Osos: affordable housing, accessory dwelling units, and agricultural worker housing.  Currently, the residential growth rate is 0% for undeveloped properties in the Los Osos sewer service area.

On December 15, 2020, the Board of Supervisors tentatively approved the following growth rates:

• Before the Phase 1 Basin Plan Programs are implemented - 0% growth rate
• After the Phase 1 Basin Plan Programs are implemented - 1.3% growth rate

The proposed growth rate has not yet taken effect and is subject to change, as it will be reviewed annually for appropriateness, based on ongoing basin monitoring data.  The Board of Supervisors Tentatively Adopted Growth Management Ordinance Amendment (2020) is available at the following weblink:

     Tentative Residential Growth Rate for the Los Osos Urban Reserve Line (as of December 15, 2020)

On October 27, 2021, in conjunction with transitioning to an adaptive management groundwater model that seeks to halt further seawater intrusion while the basin plan programs are being implemented, the BMC unanimously approved a new sustainable yield estimate of 2,380 acre-feet per year (AFY) for the Basin for calendar year 2022, a 380 AFY reduction from the 2020 estimate.  The County may propose an amended residential growth rate for Los Osos based on this new data and the results from the water offset study to update the Retrofit-to-Build program.

Retrofit-to-Build Program & Water Offset Study

The Retrofit-to-Build program (under Title 19) requires all new structures that use water from the Basin to retrofit older plumbing fixtures in existing homes and businesses to save twice the amount of water the new development will use prior to issuance of a construction permit to mitigate water supply impacts.

Maddaus Water Management Inc. completed a Los Osos Water Offset Study in June 2023 to evaluate the "retrofit-to-build" program and inform ongoing land use and water resources planning efforts for the community. The study includes updated estimates of average annual residential water use in Los Osos; an estimate of remaining water savings potential, considering historic conservation measures and remaining indoor and outdoor water efficiency retrofits; and recommendations for increasing program reliability. The Department may recommend amendments to the retrofit-to-build program policies based on the study findings, which would be subject to approval by the County Board of Supervisors at a public hearing.

The Retrofit-to-Build program requirements and Los Osos Water Offset Study are available at the following weblinks:

Retrofit-to-Build Program Requirements

Los Osos Water Offset Study

Los Osos Retrofit to Build (Title 19) and Retrofit Upon Sale (Title 8) Program Update

The County adopted a community-wide habitat conservation plan for Los Osos and obtained a 25-year programmatic incidental take permit from the U.S. Fish and Wildlife Service in February 2024 to balance residential and commercial development, infrastructure projects, and implementation of fire hazard reduction with the conservation of habitat for federally listed animals and plants. With an incidental take permit, the County has the ability to issue Certificates of Inclusion to confer incidental take coverage to landowners and other entities if their proposed activities are covered under the incidental take permit and they agree to satisfy all applicable conditions in accordance with the incidental take permit.  This programmatic approach allows the County to more effectively restore and conserve habitat, while eliminating the need for landowners and other entities to pursue individual incidental take permits with site-specific habitat conservation plans.

For more information and project files, please visit the LOHCP webpage

On April 4, 2023, the County adopted a Coastal ADU Ordinance that restricts ADU development using water from the Los Osos Groundwater Basin until water resource considerations are addressed. California Coastal Commission certified the ordinance on May 11, 2023. The redline ordinance is available at the following weblink:

Coastal ADUs

The Estero Area Plan is the current framework for development in Los Osos until the Los Osos Community Plan is certified by Coastal Commission and any requested modifications approved by the County Board of Supervisors.

     Estero Area Plan