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The State Environmental Policy Act (SEPA) is a state law in Washington that requires state and local agencies to consider the potential environmental impacts of proposed projects before making decisions. This process is required for most sites requiring stormwater permit coverage.

The SEPA process involves a review of the probable environmental impacts a site may have, a determination of possible mitigation measures that may be taken to reduce impacts, an opportunity for public comment, and a determination by the lead agency if a proposal will have a significant environmental impact or not.

SEPA Requirements

Ecology or your local jurisdiction should inform you of the SEPA requirements, but it can be very beneficial to both parties to have a pre-application meeting to go over aspects of the SEPA review such as:

  • Determining whether SEPA is required
  • Discussing any regulations that may affect a site or proposal
  • Discussing the SEPA review process
  • Developing a rough timeline of the process

SEPA Checklist

One of the main components of the SEPA process that you will likely be responsible for is the SEPA checklist. A completed SEPA checklist is used by the lead agency as a guide to help determine the environmental impact of a project. Ecology has developed a Checklist Template that is helpful in completing this process. 

This checklist will require you to provide background information and to consider all potential impacts your site may have on the environment and surrounding areas including:


-Air Quality

-Surface Waters


-Trees and Other Native Vegetation

-Animal Species

-Environmental Health

-Land or Shoreline Use

-Energy & Natural Resources



-Light Pollution


-Sites of Historical Significance


-Public Services


SEPA Resources

Ecology has made a significant number of resources available to help walk applicants and jurisdictions through the SEPA process. Here are a few to help you get started: