Pima County, population 1,012,000 (2008), lies in southern Arizona on the U.S- Mexico border and surrounds the City of Tucson. Pima County was one of 42 communities in the country recognized for leadership in open space and habitat protection at www.GreenLegacy.net and in the book Green Legacy: Communities Worth Leaving to Future Generations. In 2001, Pima County adopted an award-winning comprehensive plan designed to protect entire ecosystems by requiring the conservation of up to 95 of the biological resources on private property. In addition, County voters approved more than $300 million in bonds for open space acquisition, resulting in a County natural resources and parks department that now manages over 277,000 acres of open space. In 2007, Pima County added to its preservation toolkit by adopting a TDR ordinance.

Pima County, Arizona, an acknowledged leader in habitat preservation, added TDR to its toolkit in 2007.

The mapped TDR sending areas fall into three categories: 1) Habitat, including important riparian areas, core management biological areas, special species management areas and critical landscape connections designated in the Pima County conservation lands system. 2) High noise or accident potential areas near a military airport. 3) Floodplains, geologic features, recreation areas or land with unique aesthetic, architectural or historic value.

The owners of potential sending properties apply to the County for a calculation of the number of development rights available for transfer. The County uses whichever of the following calculation methods produces the highest number of TDRs. The calculation also bases this calculation on the site’s zoning district, comprehensive plan designation or specific plan density/intensity allowance, whichever generates the greatest development potential.

• One TDR per foregone residential dwelling unit allowable on the sending site without a conditional use permit.
• One TDR for each 180,000 square feet of commercial, institutional or industrial gross square feet of floor area possible without a conditional use permit.
• If the subject sending site allows mixed use projects, the TDR calculation uses the combination of foregone dwelling units and non-residential floor area capable of generating the greatest number of TDRs.

Deductions are made for existing residences and non-residential development. TDRs are not calculated from land determined to be undevelopable by specific plans, zoning or conditions imposed by a rezoning action.

Sending site landowners may elect to transfer only a portion of their available development rights. But the portion of the sending sites preserved by such partial transfers must be identified. Various requirements pertain to partial transfers including a provision that the preserved portion of a sending site must be contiguous to preserved land on an adjacent parcel if such preserved land exists. Furthermore, the ordinance specifically limits the Rocking K South sending area to transferring no more that 500 TDRs.

To create TDRs, a permanent, non-revocable, restrictive covenant must be signed by all sending parcel owners and lien holders and recorded. The covenant specifies the number of development rights transferred and commits the landowner to maintaining the characteristics of the site that made it eligible to become a sending site. The covenant does not require public access but it does allow limited entrance for the purpose of monitoring compliance. Upon proof of recordation, the County issues one number development right certificate for each severed development right.

Receiving site projects must comply with all development standards that apply in whatever zoning district allows the same uses as the proposed project and “has a maximum development density or intensity equal to or greater than the development density or intensity shown in the application.”

Receiving areas are depicted on a map attached as an exhibit to the TDR ordinance. Individual parcels within these receiving areas can become receiving sites without a rezoning. This could turn out to be an attractive approach. In many communities, the bonus attainable via TDR is the difference between the density limit of current zoning and the higher density depicted in the general plan but developers must still apply for and be granted a rezoning before being able to use that higher density. In contrast, Pima County allows this higher density, subject to the limits listed below, without requiring a separate rezoning procedure as well as the hearing and discretionary approval requirements associated with rezoning. The County’s Fact Sheet lists this feature as the main benefit of the TDR program for property owners within the receiving areas.

Although TDR receiving projects need not undergo a rezoning process, they must still comply with other applicable approval procedures such as the subdivision plat or development plan process to ensure the adequacy of infrastructure and public services. Each TDR enables one additional dwelling unit on a receiving site if the project is approved. The maximum development allowed via TDR is limited to whichever of the following approaches produces the smallest maximum development.

• The maximum permitted by the comprehensive plan.
• The maximum permitted by a condition imposed by a prior rezoning.
• The development limitations of the site determined after a study of cultural resources, floodplain limitations and transportation right-of-way requirements.

In addition, the applicant can request a comprehensive plan amendment and, if approved, the County Board may impose a maximum development limit attainable via TDR.