Sonoma County Supervisors Consider Lifting Some Farm ADU Restrictions in August

Written By: Gary Quackenbush
Published: July 3, 2019

The Sonoma County Planning Commission is recommending to the Board of Supervisors that farmers on certain qualifying parcels be allowed to build one Accessory Dwelling Unit (ADU), defined as a non-farm residence on their property.

Such a decision would lift the second dwelling unit exclusion for Ag property within the Z Combining District that currently excludes ADUs. This exclusion has been in place for 26 years despite several attempts to remove it.

The recommendation came during a Planning Commission public hearing on May 2. The proposed change is currently scheduled to be reviewed by county supervisors on August 6.

If approved, this action would implement an adopted policy of Sonoma County General Plan’s Housing Element (HE-3.1) “to eliminate unnecessary regulatory constraints to the production of affordable housing, while continuing to protect and support agricultural and environmental resources.”

The proposal would also be in synch with state law (Govt. Code Section 65852.2) by removing obstacles to the creation of accessory dwelling units and ensure the application of uniform, ministerial standards for ADUs.

If endorsed, the action would come at a time when the county is supporting efforts to build 30,000 new dwellings in the wake of the 2017-18 wildfires that destroyed thousands of homes and keep pace with growing demand.

Permit Sonoma Director Tennis Wick said, “The housing crisis calls for bold and creative strategies to increase housing, especially affordable housing. This is just one more step designed to reduce regulatory roadblocks for housing, as well as a way to support agriculture.”

ADUs are a permitted use in nearly all agricultural zones, such as those classified for Land Intensive, Extensive and Diverse Agriculture (LIA, LEA, DA), except where the Z Combining District ADU exclusion exists.

He said General Plan Housing Element (HE-3c) calls for the County to “review the Z District policy on agricultural parcels of less than 10 acres countywide, and to consider removing restrictions where appropriate.”

Today Z District restrictions prohibit ADUs on 6,090 parcels throughout the county, including 3,985 agricultural parcels. Of the Ag total, 65%, or 1,924 parcels, meet the criteria developed by the Permit Sonoma staff and are eligible for rezoning if they meet the following criteria:

  • The farm property cannot be located in a high/very high fire hazard severity zone
  • The property cannot be within a critical biotic habitat area for the California Tiger Salamander
  • An ADU on the parcel must not present the potential for groundwater contamination
  • An ADU on the parcel cannot unduly contribute to declining groundwater levels
  • The property is not located in a Traffic Sensitive Combining Zone
  • The property is not subject to the Land Conservation Act (Williamson Act), other open space contract, or other recorded agricultural easements
  • Property is not located in the Coastal Zone

County Supervisors created the Z exclusion in 1993 to define areas where ADUs would not be allowed due to site constraints, and also to limit non-farming uses on parcels that may be eligible for farm-specific housing (such as employee housing). The Z District regulation was also applied to agricultural areas as a way to limit non-farming uses as well as to preserve agricultural activity in these areas.

In general, “site restraints” include having a minimum parcel size, adequate access to the property, meeting sufficient potable water supply standards and the age, quality and capacity of septic systems (determined by the number of bedrooms included). Other requirements also apply — including whether the treatment of wastewater produced must involve a private On-Site Wastewater Treatment System (OWTS).

If approved by the Board of Supervisors, and when eligible farm parcels are rezoned and all applicable standards are met, property owners would have to apply for an ADU building permit.

According to David Rabbitt, Chair of the Sonoma County Board of Supervisors, “From a county perspective, elected officials and planners primarily look at how regulations affect housing affordability by design to achieve General Plan consistency.”

With the ADU example, right now property owners with land in the Z District can still apply for an ADU permit, but this requires a zoning permit application that goes to the Board of Zoning Adjustments and the Board of Supervisors for approval. If the ADU was allowed on the property By Right, it wouldn’t need to go through a lengthy approval process.

“By Right” development refers to projects that are permitted under their current zoning and do not require any legislative action by the Board of Supervisors or the Board of Zoning Appeals. Instead, they are approved administratively and do not require public hearings.

Supervisor Rabbitt said, “The concept being applied today in a high-priced real estate economy involves building smaller, right-sized dwellings – such as ADUs and JDUs (Junior Accessory Dwelling Units) — which can lower the cost of construction along with the purchase price to make housing easier and more affordable for residents. Sonoma County and Santa Rosa are looking at every opportunity to achieve this.”

The Permit Sonoma staff has analyzed agricultural parcels within the Z District to address the potential for environmental impacts. Doing a collective review for all eligible parcels saves time from having to do each one individually. ADUs are statutorily exempt under the California Environmental Quality Act (CEQA) according to Public Resources Code Section 21080.17. Therefore, no environmental review or a Mitigated Negative Declaration (MND) would be required if this proposal is passed.

Under today’s standards, many affected parcels would qualify for an ADU. In addition, agricultural parcels that do not qualify for farm housing may qualify for an ADU.

Since the Z Combining District was adopted, the county has been reviewing applications on a site-by-site basis to remove the Z District ADU restriction. More than 40 applications have been received and approved.

“When reviewing these applications, the county learned that many agricultural areas that had site constraints no longer face these barriers,” said Wick.  “For example, farms connected to public sewers no longer have to meet criteria associated with septic systems.”

Three proposed text amendments to ADU policy were identified by the Permit Sonoma staff to improve compatibility and reduce potential impacts countywide:

  • An ADU would count as one of the eligible agricultural housing units on a farm property. This reduces the potential that non-farm residences (ADUs) will result in over-development of Ag parcels.
  • Groundwater standards requiring no additional water use for ADUs in low groundwater areas would also apply in critical habitat areas where depleted streamflow threatens the recovery of endangered salmonids in areas defined by the National Marine Fisheries Service as “Priority Areas for Protection and Restoration” of endangered fisheries habitat.
  • The staff recommends a third zoning text amendment to require that no permanent crops be removed to accommodate an ADU – thus mitigating potential construction-related impacts to Ag crops.

“The ADU concept is not new,” Wick noted.  “Early examples can be traced back to the beginning of the 20th century when small cottages were often provided for farm workers by landowners. After doing some quick math, if all eligible agricultural housing unit options were to be implemented by a farmer, total housing square footage allowed could exceed 13,000 square feet.”

Based on Permit Sonoma fact sheets, seven housing options for agricultural lands are allowed under existing rules, and a majority of these provisions – with the notable exception of those in Z Districts — have been in effect for 20 years or more. They include:

  • Accessory Dwelling Unit (ADU): One unit up to 1,200 sq. ft. not currently allowed in a Z Combining District, or parcels subject to the Williamson act. (Available since the 1990s)
  • Junior Accessory Dwelling Unit (JDU): One unit within an existing primary residence up to 500 sq. ft. Allowed in zoning districts DA, LIA, LEA, RRD (Resources and Rural Development zones), and AR (Agricultural and Residential District zones).
  • Farm Family Dwelling Unit(s): One for every: 50 dairy animals, 20 acres of permanent crops, 100 grazing animals, 20,000 broilers, 15,000 laying hens, 3,000 turkeys, 30 horses, or three-acres of field-grown nursery stock or one acre of greenhouse. Allowed in DA, LIA, LEA and RRD zoning districts.
  • Year-round Farmworker Housing: Five-acre minimum lot size, 38 workers or use permit required. Allowed in DA, LIA and LEA zoning districts/RRD zoning for parcels 10+ acres and subject to Williamson Act contract.
  • Seasoned Farmworker Housing: 5-acre minimum lot size, 19 workers; occupied no more than 180 days per year.  Allowed in DA, LIA, LEA and RRD zoning districts.
  • Caretaker Unit: One unit allowed for properties with seasonal farmworker housing.  Allowed in DA, LIA, Lea and RRD zoning districts.
  • Temporary Farmworker Camps: Up to four self-contained recreational vehicles or travel trailers; occupied no more than 50 days per year.  Allowed in DA, LIA, LEA, RRD and AR zoning districts.

Many agricultural lands throughout Sonoma County can accommodate a number of different agricultural housing units as previously described.  Most housing options require a planning application and filing fee prior to issuance of any development permits.

Applicants are responsible for contacting the State Department Division of Drinking Water to permit any agricultural housing that will have 25 or more residing on the project site for 60 or more days of the year. To determine if an agricultural property is in the Z Combining District, go online to:

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