Issaquah, Washington

Issaquah, Washington, population 39,378 (2018), is located 18 miles east of downtown Seattle on I-90, the only interstate route heading east over the Cascade Mountain Range from Puget Sound. Issaquah and King County used the King County TDR program in March 2000 in a transaction that preserved a 313-acre sending area in King County and allowed an additional 500,000 square feet of floor area in an office complex within the City of Issaquah.

Issaquah uses TDR to preserve stream corridors and expand public open space within its city limits.

In 2003, the City began to explore the prospects for a TDR ordinance that could protect critical areas within the City. One year later, the City adopted a Comprehensive Plan amendment with the framework for a TDR program. In September 2005, the Issaquah City Council adopted a TDR ordinance which has since been amended and, as of October 2020, is codified as Section 18-10 of Issaquah’s Environmental Protection Chapter. 

The Issaquah TDR code section lists the following purposes for the program:

  • Preserve critical areas, particularly salmon habitat, riparian corridors, and floodways.
  • Expand opportunities for parks.
  • Promote development consistent with city plans.
  • Allow transfers directly between private parties, through a city TDR bank or through the King County TDR Bank.

Sending sites within the city are designated by map and contain at least one of the following criteria.

  • At least 30 percent of the site consists of critical areas or critical area buffers.
  • Site is contiguous with public open space.
  • Preservation of site would implement a Comprehensive Plan goal.
  • Site is adjacent to a creekside restoration site.
  • Site has limited access or infrastructure accessibility.

Sending sites outside the City must be consistent with the provisions of an interlocal agreement with King County.

Receiving sites are also designated by map, cannot consist of more than 50 percent critical area and must meet at least one of four sets of criteria regarding location, zoning, proximity to a transit center and mitigation of potential impacts. The ordinance includes a provision for allowing sites to be added to the map of TDR Sending and Receiving Sites.

In addition to the purposes typically established for a TDR bank, Section 18.10.2035(D) specifies that the Issaquah City TDR bank can sell TDR certificates in advance of property acquisition and use the funds to implement TDR goals including the purchase of land for open space or parks.  

TDRs available to sending sites within Issaquah are calculated as follows.

  • For residential sites, the number of TDRs available for transfer equals the number of units that can be developed on that site.
  • For commercially zoned sites, one TDR is granted for each 1,200 square feet of floor area that can be developed on the site.

TDR allocation for sending sites outside of Issaquah is established by interlocal agreements between the city and King County.

Receiving sites offering increased residential density include parcels in three zoning districts in which TDR can increase a baseline of 14.52 DUs per acre to 18 DUs per acre or from 29 to 36 DUs per acre. In other zones, including Urban Village zones, maximum with-TDR density is either 36 units per acre or determined by development agreement or the Central Issaquah Development and Design Standards.

TDR can also be used to exceed baseline building heights by 1,200 square feet of floor area per TDR. In five receiving site zones, the maximum with-TDR building height is specified in the code. In two other districts, maximum building height is determined by the most restrictive contiguous zoning. In the Urban Village district, maximum with-TDR building height is determined by development agreement.

In addition, one TDR can increase the baseline for impervious surface coverage by 1,200 square feet of lot area. In five zoning districts, TDRs can allow impervious surface coverage ratios to increase to as high as 90 percent.   

As mentioned above, Issaquah and King County used the King County TDR program in March 2000 in a transaction that preserved a 313-acre sending area in King County and allowed an additional 500,000 square feet of floor area in an office complex within the City of Issaquah. Within two years of adopting the program in 2005, Issaquah had entered into an interlocal agreement with King County, purchased two environmentally significant parcels, and stocked its TDR bank with the resulting 42 TDRs.