We make a determination about whether, under the State Environmental Policy Act, an environmental impact statement is needed or whether it's possible to mitigate identified significant negative impacts using methods we recommend. This decision is called a SEPA threshold determination.
Steps in Environmental review
Select one of the steps to view details.
About this milestone
State laws and rules require us to make threshold determinations for all proposed facilities that meet the definition of “action” and aren’t exempt under WAC 197-11-600(3).
We have several ways to review a proposed facility’s effects and determine their significance. We can also identify ways to reduce any effects so they’re no longer significant, which we often refer to as "mitigation."
What “significant” means
Under the State Environmental Policy Act (SEPA), "significant" means negative effects are likely and will be more than moderately intense. Intensity depends on the size of the effects and how long they’ll last.
Effects can also be significant if they’re unlikely but would be severe.
Types of threshold determinations
We can make one of the following decisions about a proposed facility’s likely effects on the environment.
Determination of non-significance (DNS)
A DNS means the proposed facility is unlikely to have significant negative effects on the environment.
Mitigated determination of non-significance (MDNS)
An MDNS means the proposed facility may have negative effects on the environment, but an applicant can reduce them by using methods we recommend. We can only require applicants to use these methods if we include them in our decision.
If we believe that following our recommended methods will reduce any effects so they’re no longer significant, we may not need to prepare an environmental impact statement (EIS).
Determination of significance (DS)
A DS means the proposed facility is likely to have significant negative effects on the environment.
RCW 80.50.090(3) requires us to notify the applicant before making a DS. Applicants can also ask us to give them advance notice about whether we think a DS is likely. Either way, applicants will have the opportunity to change their application to address any significant negative effects.
Related steps
We must make a threshold determination within 90 days of determining an application is complete.
After making a threshold determination, we may use the information in our decision to prepare an environmental impact statement (EIS).
