In addition to its advisory role under the GMA, WSDOT can influence local land use through environmental review under the State Environmental Policy Act (SEPA). The primary purpose of the 1971 SEPA is to determine whether a proposed state or local government action would result in significant adverse environmental impacts, to identify reasonable measures to mitigate those impacts, and to determine whether those measures are sufficient [RCW 43.21C.060]. Additionally, state and local government actions can be conditioned or denied based on the impacts disclosed under SEPA.
All local government actions (with limited exemptions) are subject to SEPA, including the adoption and amendment of comprehensive plans and development regulations and the approval of private development permits. One of the environmental impacts that must be addressed during the SEPA review process is traffic. This provides WSDOT with an opportunity to voice concerns regarding the impact of local plans, regulations, and development approvals on the state transportation system. WSDOT can request that local governments abandon, alter, or mitigate their land use policies or regulations to avoid or minimize their adverse impacts on state highways. Likewise, WSDOT can ask local governments to deny or condition a development permit to prevent or mitigate specific adverse impacts to state highways. WSDOT can suggest potential alternate ways to serve demand that may not involve use of state transportation facilities. Even if solutions to demand created by development are not readily available, WSDOT can still "get on public record" and disclose its assessment of the consequences of development. Local governments must consider WSDOT’s SEPA requests, but are not required to comply with them.
WSDOT’s region offices are responsible for reviewing local government actions under the State Environmental Policy Act. Following are links to more information about development mitigation and SEPA.