San Mateo County, California

San Mateo County, population 718,451 (2010) lies immediately south of the City of San Francisco and extends 30 miles to the base of the San Francisco Peninsula. The northern and eastern portions of San Mateo County include several of the cities that surround the San Francisco Bay. But the central and western half of the County contains the sparsely-populated Santa Cruz Mountains and agricultural areas along the largely-undeveloped Pacific Coast.

The County adopted a Planned Agricultural District (PAD) zoning designation in order to keep prime agricultural land in production and minimize conflicts between agricultural and non-agricultural uses. To achieve these goals, the County approved several objectives.

  • Separate urban and rural areas with clear boundaries.
  • Allow the development of agricultural land in areas where land conversions would create viable neighborhoods.
  • Develop land that is not suitable for agriculture before developing prime agricultural land.
  • Do not allow public or private improvements which would impair agricultural viability.
  • Prohibit subdivisions which would reduce the productivity of prime agricultural land.

To achieve these goals, the PAD uses various implementation techniques including transfer of development rights.

San Mateo County has amended these PAD regulations many times, primarily to add new permitted and conditionally-permitted uses. But the TDR provisions remain largely unchanged. Consequently, the following Process section remains unchanged from the section that appeared in Beyond Takings and Givings.


San Mateo County’s Planned Agricultural District (PAD) includes three classifications of land in the Coastal Zone. Two of these classifications are farming-related: prime agricultural land and “lands suitable for agriculture” which are areas that are not classified as prime agricultural land but which can support some kinds of agriculture including animal grazing and forestry. Both of these classifications permit only agriculture and agricultural-related improvements as a matter of right. The third category, Other Lands, include all land that is not found in the first two classifications.

Property owners can apply for residential development in the PAD zone through a Planned Agricultural Permit. To receive a Planned Agricultural Permit, applicants must demonstrate that a proposed land division promotes the goals for the Planned Agricultural District stated above. In addition, each application must be found consistent with six general criteria, including the following: minimize encroachment on agricultural land; cluster all development; supply all non-agricultural development with on-site well water; maintain water supply for agriculture and wildlife habitat; and deed restrict the transfer of riparian rights.

Three specific criteria apply to proposed subdivisions on prime agricultural land: a parcel consisting entirely of Prime Agricultural Land cannot be subdivided; a land subdivision cannot reduce the agricultural productivity of any resulting parcel; and a subdivision cannot occur if the only building site would be on Prime Agricultural Land. In addition, 14 more special criteria apply to the conversion of agricultural land to recreational, agriculturally-related and other uses.

San Mateo County regulates density through density credits. One credit per 160 acres is allocated to prime agricultural land, land with landslide susceptibility, land with slopes of 50 percent or more and remote lands, meaning land more than one-half mile from an all-weather public road in existence prior to the initial certification of the County Local Coastal Program in 1980. One density credit per 80 acres is allocated to fault zones and lands with slopes greater than 30 percent but less than 50 percent. One density credit per 60 acres is assigned to flood hazard zones, agricultural preserves/exclusive Agricultural Districts and land with slopes greater than 15 percent but less than 30 percent. All other areas are assigned one density credit per 40 acres. If land falls into more than one category, it is assigned to the category that allows less density.

To apply for a land division, a property owner must submit a Master Land Division Plan showing how the initial parcel will be divided into agricultural and non-agricultural parcels.

Non-agricultural parcels cannot be larger than five acres. If the land division is approved, agricultural parcels must be permanently preserved for agricultural uses by granting an agricultural easement to the County.

San Mateo County allows bonus density credits to be created by the combination of contiguous parcels. A 25 percent density credit bonus is granted if all parcels in the merger are 40 acres or less in size. The bonus is ten percent if any of the parcels in the merger are greater than 40 acres.

Bonus density credits are also granted for the development of agricultural water impoundments. The amount of bonus density varies with the size of the water storage facility. A density bonus of one dwelling unit is granted for an agricultural water impoundment of at least 24.5 acre-feet of capacity. An additional density bonus of one dwelling unit is added for each additional 24.5 acre-feet of capacity.

Whether they are gained through lot consolidation or the construction of agricultural water storage facilities, bonus density credits can be transferred to approved receiving sites in the rural Coastal Zone. In approving these transfers, the Planning Commission must determine that the proposed transfer complies with the Local Coastal Program and that the transfer will not convert Prime Agricultural Land or scenic corridors. A maximum of four bonus density credits can be transferred to a receiving site. More than four credits can be transferred if the Planning Commission finds that additional density would not overburden coastal resources.

To finalize a transfer, a deed restriction must be placed on the sending parcel acknowledging that the bonus density credit has been relinquished. A covenant on the receiving parcel must also be recorded, noting that the parcel has been granted bonus density credits in addition to the density allowed by zoning.

In addition to transferring bonus density credits, the San Mateo program allows the transfer of density credits from rural Coastal Zone areas which have either Prime Agricultural Land or Prime Agricultural Land plus other land which is not developable under the Local Coastal Program. Once transfers have occurred, the sending parcels must be permanently restricted for agricultural use only through easements granted either to the County or another governmental agency. A deed restriction on the sending parcel must also record the fact that density credits have been relinquished.

Under this program option, the potential receiving sites include other Coastal Zone properties east of Highway 1 which have been determined by the Planning Commission to be suitable for transferred density under the Local Coastal Program. The Commission must also find that the density credits will not convert Prime Agricultural Land or scenic corridors. A deed restriction must be recorded to show that the receiving parcels have been granted additional density credits.

Program Status

The San Mateo County program has several features found in successful TDR programs. The restrictions placed on land in the Planned Agricultural District make it difficult to subdivide prime agricultural land, giving the owners of these parcels a motivation for using the transfer process. In fact, regardless of the level of transfer activity, the County is achieving its goal of agricultural preservation through its zoning ordinance. Potential receiving parcels are controlled by the Local Coastal Plan, making approvals of increased density difficult unless the proposed increase promotes a Coastal Plan goal, such as the preservation of agricultural land.

Despite these promising features, only two density credits were transferred between program inception in 1988 and 2001. The credits were bonus credits created by the development of an agricultural water impoundment. According to Diane Regonini of the San Mateo County Planning Department, there could be several reasons for the relatively low level of transfer activity. Under the bonus density credit program, there may be a limited number of contiguous land parcels with the ability to generate a significant number of bonus density credits through lot consolidation. Similarly, there may be a limited number of farmers with the ability to finance the development of water storage facilities; under the current program, the water storage improvement must be completed before the farmer receives the bonus density credits.

As described above, density credits can also be transferred from parcels that are completely prime agricultural land. It is possible that there are relatively few parcels which meet these requirements, further reducing the potential supply of density credits. At the receiving end of the transfer, it is also possible that there are a limited number of receiving sites that comply with the transfer criteria, reducing the demand for transfers.