T1.5 Clustered development
Encourage clustered developments to conserve farmland and forests.
Planned rural residential developments, or rural cluster subdivisions, allow residences on smaller individual lots in exchange for the dedication of a large portion of the overall project to agriculture (including forestry), passive recreation, natural areas, and infrastructure related to water systems, stormwater, or drainfields. TRPC has a flyer about them; it notes that the density bonuses for employing them were removed in 2011, as part of ending a moratorium on them, and that only one has been built since. Thurston County currently limits their size to a maximum of 100 acres; multiple parcels under common ownership or developed as a unified project are considered a single project.
There’s currently a proposed amendment to the comprehensive plan which would allow the development of clustered subdivisions larger than 100 acres, if they were approved as part of a Master Plan.
The Sustainable Development Code website discusses a number of other examples around the country. A study of several different site designs for an 1,800 unit subdivision estimated that over 91% of existing carbon storage and 82% of sequestration could be maintained by planning for cluster development and taking different forest types and tree stand ages on the 1,700 acre site into account.