(1) Each county that is required or chooses to plan under RCW 36.70A.040 shall designate an urban growth area or areas within which urban growth shall be encouraged and outside of which growth can occur only if it is not urban in nature. Each city that is located in such a county shall be included within an urban growth area. An urban growth area may include more than a single city. An urban growth area may include territory that is located outside of a city only if such territory already is characterized by urban growth whether or not the urban growth area includes a city, or is adjacent to territory already characterized by urban growth, or is a designated new fully contained community as defined by RCW 36.70A.350.

(2) Based upon the growth management population projection made for the county by the office of financial management, the county and each city within the county shall include areas and densities sufficient to permit the urban growth that is projected to occur in the county or city for the succeeding twenty-year period, except for those urban growth areas contained totally within a national historical reserve. As part of this planning process, each city within the county must include areas sufficient to accommodate the broad range of needs and uses that will accompany the projected urban growth including, as appropriate, medical, governmental, institutional, commercial, service, retail, and other nonresidential uses.

Each urban growth area shall permit urban densities and shall include greenbelt and open space areas. In the case of urban growth areas contained totally within a national historical reserve, the city may restrict densities, intensities, and forms of urban growth as determined to be necessary and appropriate to protect the physical, cultural, or historic integrity of the reserve. An urban growth area determination may include a reasonable land market supply factor and shall permit a range of urban densities and uses. In determining this market factor, cities and counties may consider local circumstances. Cities and counties have discretion in their comprehensive plans to make many choices about accommodating growth.

Within one year of July 1, 1990, each county that as of June 1, 1991, was required or chose to plan under RCW 36.70A.040, shall begin consulting with each city located within its boundaries and each city shall propose the location of an urban growth area. Within sixty days of the date the county legislative authority of a county adopts its resolution of intention or of certification by the office of financial management, all other counties that are required or choose to plan under RCW 36.70A.040 shall begin this consultation with each city located within its boundaries. The county shall attempt to reach agreement with each city on the location of an urban growth area within which the city is located. If such an agreement is not reached with each city located within the urban growth area, the county shall justify in writing why it so designated the area an urban growth area. A city may object formally with the department over the designation of the urban growth area within which it is located. Where appropriate, the department shall attempt to resolve the conflicts, including the use of mediation services.

(3) Urban growth should be located first in areas already characterized by urban growth that have adequate existing public facility and service capacities to serve such development, second in areas already characterized by urban growth that will be served adequately by a combination of both existing public facilities and services and any additional needed public facilities and services that are provided by either public or private sources, and third in the remaining portions of the urban growth areas. Urban growth may also be located in designated new fully contained communities as defined by RCW 36.70A.350.

(4) In general, cities are the units of local government most appropriate to provide urban governmental services. In general, it is not appropriate that urban governmental services be extended to or expanded in rural areas except in those limited circumstances shown to be necessary to protect basic public health and safety and the environment and when such services are financially supportable at rural densities and do not permit urban development.

(5) On or before October 1, 1993, each county that was initially required to plan under RCW 36.70A.040(1) shall adopt development regulations designating interim urban growth areas under this chapter. Within three years and three months of the date the county legislative authority of a county adopts its resolution of intention or of certification by the office of financial management, all other counties that are required or choose to plan under RCW 36.70A.040 shall adopt development regulations designating interim urban growth areas under this chapter. Adoption of the interim urban growth areas may only occur after public notice; public hearing; and compliance with the state environmental policy act, chapter 43.21C RCW, and under this section. Such action may be appealed to the growth management hearings board under RCW 36.70A.280. Final urban growth areas shall be adopted at the time of comprehensive plan adoption under this chapter.

(8)(a) Except as provided in (b) of this subsection, the expansion of an urban growth area is prohibited into the one hundred year floodplain of any river or river segment that: (i) Is located west of the crest of the Cascade mountains; and (ii) has a mean annual flow of one thousand or more cubic feet per second as determined by the department of ecology.

(B) Urban development already exists within a floodplain as of July 26, 2009, and is adjacent to, but outside of, the urban growth area, and the expansion of the urban growth area is necessary to include such urban development within the urban growth area; or

(I) The permissible use of the land is limited to one of the following: Outdoor recreation; environmentally beneficial projects, including but not limited to habitat enhancement or environmental restoration; stormwater facilities; flood control facilities; or underground conveyances; and

(II) The development and use of such facilities or projects will not decrease flood storage, increase stormwater runoff, discharge pollutants to fresh or salt waters during normal operations or floods, or increase hazards to people and property.

(9) If a county, city, or utility has adopted a capital facility plan or utilities element to provide sewer service within the urban growth areas during the twenty-year planning period, nothing in this chapter obligates counties, cities, or utilities to install sanitary sewer systems to properties within urban growth areas designated under subsection (2) of this section by the end of the twenty-year planning period when those properties:

(10) Urban growth area boundaries shall follow parcel boundary lines existing when the land is included in the urban growth area and reasonable efforts should be made to avoid unnecessary divisions. When a parcel is or will be split by an urban growth area boundary, the part of the parcel outside of the urban growth area may only be added to the urban growth area if the land is needed to accommodate the growth management population projection or there is a corresponding reduction in the size of the urban growth area, the area to be added does not include critical areas or natural resource lands of long-term commercial significance, and the area to be added can be served by existing or planned public facilities and services during the twenty-year planning period. Any changes required by this subsection shall be made as part of the next comprehensive plan periodic update and shall not result in a finding of noncompliance before that time.