Marin County, California

Marin County, population 252,409 (2010), is the peninsula that lies across the Golden Gate Bridge from San Francisco. The County has been concerned for decades about the impact of encroaching urbanization on the agricultural character of the County.

Nicasio Valley, an agricultural area in the center of the County, was the subject of a community plan adopted in 1979. The Nicasio Valley Community Plan discussed using clustered development as a means of preserving portions of farms for agricultural purposes. However the plan concluded that TDR was preferable to clustered development as a means of preserving agriculture because TDR is capable of locating development where it belongs within the entire community regardless of property ownership patterns. Consequently, the plan recommended that TDR be studied as a possible means of preserving agriculture and protecting water quality.

In 1981, the Marin County Board of Supervisors agreed that TDR could be effective in protecting agricultural land. As a result, TDR was added as an implementation measure to the Marin County wide Plan, the Nicasio Valley Community Plan and the Agricultural-Residential Planned District of the Marin County Zoning Ordinance.

The 2011 version of the Marin County Development Code retains the same code section used to write the program profile that appeared in Beyond Takings and Givings, published in 2003. Furthermore, it appears that Nicasio continues to have the only community plan in Marin County containing TDR provisions. Consequently, this case study largely duplicates the earlier profile.


Marin County’s Agricultural-Residential Planned (A-RP) zoning district allows flexibility for the inclusion of residential development in agricultural areas. Specifically, this zone allows development rights to be transferred from productive agricultural land and environmentally-sensitive areas to locations where impacts would be minimized. The TDR provisions are only available in areas where a community plan or County wide plan has identified TDR as an implementation measure. To date, the Nicasio Valley Community Plan is the only community plan in Marin County that recommends TDR and, consequently, TDR can only be used within Nicasio Valley at this time.

Under the A-RP zone, sending sites are not pre-designated. Developers propose sending sites through the master plan process. In the master plan process, the applicant must demonstrate that the sending site should be preserved and that the proposed receiving site can accommodate the transferred development. In addition, the applicant must outline how the proposed TDR will implement the conservation criteria set forth in the applicable community or County wide plan. The criteria in the Nicasio Valley Community Plan for sending areas include the following: property with steep slopes; property near streams or the Nicasio Reservoir; wooded property; property with prime agricultural soils; property needed for the continuation of agricultural activities; and properties on which development would be highly visible. When transfers are approved, restrictions against future development are secured through conservation easements recorded against the sending sites.

The master plan approval process allows bonus density to be awarded to the receiving site in addition to the density allowed by the base zoning plus the density transferred to the site. Receiving sites must be evaluated under the criteria established in the applicable community plan. The Nicasio Valley Community Plan contains the following criteria for judging the suitability of a proposed receiving site: the property should have the infrastructure and support services needed to accommodate the proposed development; the traffic generated by the proposed development should not significantly impact agricultural activities; the proposed receiving site should be large enough to accommodate the increased density; the site should not create landslide hazards; and the proposed site should not affect unique environmental resources.

Program Status

The Marin County TDR program benefits from purchase of development rights programs which have been active in the County for many years. For example, the Marin Agricultural Land Trust alone has protected over 41,000 acres of farmland by acquiring conservation easements. As a result, the concept of severing development rights is familiar to County property owners and the value of these rights is well established. The Marin County program also benefits from the fact that it is difficult to obtain additional density on receiving sites without using TDR unless affordable housing bonuses are used.

Even though the demand for new development in Marin County is high, the pace of development is relatively slow, about 0.3 percent per year; this may be due to the fact that prime sites have already been developed, leaving parcels with steep slopes and other development difficulties. According to County Planning Director Mark Riesenfeld, this slow growth rate partly explains why only one TDR project has been approved in Marin County since the TDR concept was introduced in the late 1970s.

In Marin County’s only approved TDR project, the sending site was a ranch located about a mile outside the village of Nicasio. The owner of this ranch also owned the receiving site: a 120-acre parcel immediately adjacent to the village of Nicasio. The sending site was deed restricted for agricultural uses. The 120-acre receiving site was granted development rights for two dwelling units by the underlying zoning. Ten more dwelling units were transferred in from the sending site and an additional five dwelling units were awarded as a transfer bonus, bringing the receiving site total to 17 units. This project is considered a success because it transferred development which could have occurred in the countryside to a location adjacent to an existing village. However, the one-dwelling-unit-per-seven-acre density of the approved development is a significant density reduction from the compact development pattern of the adjacent village.

In 2007, Kent Messer reported in the Journal of Conservation Planning that Marin County had preserved 670 acres using TDR.