(Profiled 3-30-2021)

Summit County, Colorado, population 31,011 (2019), surrounds the popular Breckenridge ski resort in central Colorado. Summit County adopted four TDR programs to protect environmental resources in the county’s four watershed basins. The Upper Blue Basin TDR Program is the most active and had protected 2,000 acres as of March 2021.

Summit County’s Climate Action Plan, adopted in 2019, recognizes that forest preservation and maintenance protect existing carbon sinks and promote the sequestration of future carbon emissions. Consequently, the plan calls for expansion of the existing TDR programs in the Lower Blue, Snake, and Ten Mile river basins and encouragement of the towns of Dillon, Frisco, and Silverthorne to use TDRs to protect forested lands from development.

The Upper Blue Basin TDR Program, launched in 2000, operates within the Upper Blue Basin which encompasses approximately 80,400 acres and has a permanent population of roughly 9,500 inhabitants. Development here mostly occurs in the valley near the Blue River, typically near the towns of Breckenridge and Blue River. Almost 80 percent of the basin lies within the National Forest Service system, primarily consisting of forested mountainsides. However, the backcountry is also dotted with hundreds of private mining claims that are technically capable of residential development even though they are often located on ridgelines and above the timberline in environmentally sensitive areas. Development here can also degrade important viewsheds and block access to national forest recreational sites. Consequently, the TDR program initially aimed to protect backcountry areas, natural resources, and open space in the mountains near Breckenridge and Blue River.     

The county attributes the success of the Upper Blue Basin TDR Program partly to the participation of the towns of Breckenridge and Blue River. Importantly, town and county policies prohibit upzonings without the use of TDR. In addition, owners of private mining claims are motivated to participate in transfers by the adoption of the Backcountry Zoning District, which rezoned hundreds of mining claims to a maximum density of one dwelling unit per 20 acres. Each TDR here represents the preservation of 20 acres of land.

In the Backcountry zoning district, existing roads cannot be improved without a conditional use permit and new roads must comply with standards that minimize disturbance. Snowplowing also requires a conditional use permit and can only occur if at least four inches of snow is left on road surfaces. The county may not provide public facilities, emergency response, or community services to properties in this zone.

Single-family dwellings in the Backcountry zone are limited to 2,400 square feet of floor area. Dwellings on legal nonconforming lots of two acres or less are limited to 750 square feet of floor area and can gain an additional 50 square feet for each acre in excess of two acres up to a maximum of 2,400 square feet. In addition, extensive requirements apply to accessory structures, decks, tree removal, and other site alterations.

The county designates sending and receiving areas on the Official Transfer of Development Rights Map. According to Code Section 3506.02, TDR Regulations, owners of land within the mapped receiving areas can apply to use TDR in conjunction with a zoning amendment or PUD modification that would increase density, increase floor area, increase vehicle trips for commercial/industrial uses, and/or increase the activity levels allowed by the applicable zone. Applicants can also propose TDR as a means of mitigating development impacts. Various types of development are exempt from these provisions including affordable housing and modifications of internal density within the Keystone and Copper Mountain Resort PUDs. 

Each TDR allows receiving site baselines to be exceeded by one single-family dwelling unit of up to 4,356 square feet, or one multi-family unit of up to 1,400 square feet, or three rooms of lodging not to exceed 467 square feet each, or 1,000 square feet of non-residential floor area. When receiving sites are proposed to exceed vehicle trip baselines, each TDR allows the number of trips generated by a single-family residence as stated in the most recent edition of the Trip Generation Manual of the Institute of Transportation Engineers.

Summit County prefers transfers between sending and receiving sites in the same basin. However, the review authority for the receiving site basin may consider an inter-basin transfer based on five criteria including conformance with planning goals and evidence that the needed TDRs are not readily available within the same basin. The code section on inter-basin transfers adds further conditions about where, when and how many TDRs can be transferred between specific basins.

In the Lower Blue, Snake River, and Ten Mile basins, developers may voluntarily propose alternatives to the TDR program requirements such as the dedication of land for open space, community facilities, or affordable housing. Such proposals are subject to five criteria including that the value of the proposed community benefit be roughly proportional to the value of the number of TDRs that the project would otherwise have to acquire. In addition, the county allows contributions in lieu of TDRs that are used to buy development rights from sending area properties.    

The TDR Bank is also a major success factor. The Bank has a separate account for each of the four TDR programs operating in Summit County’s four basins. The Bank’s sale price for a TDR from the Lower Blue River Basin account is the fair market value of that TDR determined on a case-by-case basis. The Bank sells Upper Blue Basin TDRs at prices established annually based on the median sales price of all vacant land zoned Backcountry in that basin sold after 2000, the year when that TDR program was instituted. The Bank sells TDRs from the Snake River Basin, and Ten Mile Basin at prices set each year and based on the median sales price from all vacant land zoned Backcountry since 2007, the year that the county adopted Backcountry zoning in those two basins. In March 2021, the bank sold Upper Blue TDRs for $99,045, roughly $4,952 per acre and Countywide TDRs for $63,065, or roughly $3,153 per acre.

The Upper Blue Basin TDR Program had preserved 2,000 acres as of March 2021 and generated roughly $4 million for further open space protection. Program amendments now allow TDRs to also be sold in return for the preservation of high-quality wetlands in receiving areas. As of March 2021, the program had protected roughly 14 acres within 27

In addition to the 2,000 acres protected by the Upper Blue Basin TDR Program, as of March 2021: the Snake River Basin TDR Program, adopted in 1998, had protected roughly 300 acres in nine separate transactions; the Ten Mile Basin TDR Program, adopted in 2006, had protected 199 acres in a single transaction; and the Lower Blue Basin TDR Program, adopted in 2007, had protected 20 acres in one transaction.