Urban Growth Boundary (UGB)

Current Status

Urban Growth Boundary Map
Click to Download the Spheres of Influence Map

The City Council voted to place a measure on the November 2020 ballot to extend the City's Urban Growth Boundary (UGB).  More information can be found on the Ballot Measure W page.

Background, news items regarding this issue, and related documents can be found below.


An urban growth boundary (UGB) separates urban areas from the surrounding natural and agricultural lands, or greenbelts. It puts a limit on how far out a city can expand. UGBs are often set for a specified period of time, such as 20 years. Different cities may call these barriers by different names, such as “urban limit lines” or simply “growth boundaries,” and are created to prevent “urban sprawl” development and encourage sustainable growth practices.

November 7, 2000, Sonoma’s voters adopted a measure (Measure S) that created a UGB that modified the City’s adopted General Plan to restrict development beyond it. The location of the UGB at the time was, and for the most part today is, overlaps with the City’s Sphere of Influence (SOI). The approved measure included a timing mechanism that allows the City Council to make changes to the UGB after December 31st, 2020 without voter approval. In order to retain the same timing mechanism to require voter approval of any changes to the location of the UGB, an initiative would need to be placed on this November’s ballot.

January 27th, 2020, the City Council held a joint meeting with the Planning Commission to discuss land use planning topics that centered around recent housing legislation, an update to the City’s General Plan and Housing Element, possible amendments to the City’s Development Code and potential modifications to the City’s Urban Growth Boundary (UGB). See the staff report and PowerPoint Presentation.

City Council received a staff presentation, discussed matters with the Planning Commission and received public comment. City Council directed staff to prepare a new Measure to re-establish and renew the UGB in the same location as the City’s sphere of influence line (“SOI”) as it has existed historically with no boundary changes and to prepare this for the November 3, 2020 ballot. The general feedback from the Study Session was to explore the following language changes to the UGB measure:

  • Allow for the development of housing which is “100% affordable” and to have a minimum of 51% affordable to those with “low” and “very low” incomes.
  •  To recognize properties that are outside the UGB that have a vested right or contractual right (based on an enforceable contract with the City) to receive water service (e.g. the Thornsberry Road Area Water Assessment District, et al.)
  • Provide clearer language for the development of the 5-acre maximum that can be brought in to the UGB in any given year, to remove from that acreage calculation, riparian corridors and other natural resources.

February 3, 2020, City Council created an Ad Hoc City Council Subcommittee of Vice Mayor Hundley and City Council Member David Cook to work with staff to draft the necessary language to extend the UGB to 2040 and have that language presented to the full City Council.

March 11, 2020, the City Council Ad Hoc Subcommittee invited Planning Commissioners Steve Barbose and Larry Barnett to join in the review of a draft that was prepared by staff.  Additional feedback was provided and staff was asked to prepare an updated draft. The Sub-Committee has since reviewed the updated language and is supportive of the current draft ballot measure.

April 23, 2020,  The City Council Ad Hoc Subcommittee welcomed public input on Draft UGB Ballot Measure for November 2020 Election.

June 1, 2020, City Council reviewed a draft version of the Urban Growth Boundary (UGB) Ballot Measure for the November 2020 Election. After receiving public comment, City staff was directed to make changes to the draft. See full update.


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