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Cumulative Effects Analysis

Ecosystem Wetland photo Photo courtesy of U. S. Fish and Wildlife

Federal and State environmental regulations require consideration of indirect effects and cumulative impacts to provide decision makers with an understanding of the relationship between short-term uses and long-term productivity of the environment.

The information provided on this page is designed for a technical audience and is intended for use by WSDOT staff completing environmental documentation for WSDOT transportation projects.

WSDOT policy for completing the Indirect and Cumulative Effects is described in Chapter 412 of the Environmental Manual (EM)and complies with the following documents:

Greenhouse Gas and Climate Change Evaluations

WSDOT considers climate change and greenhouse gas impacts during the NEPA and SEPA environmental review process. Incorporate a qualitative discussion of potential climate change and greenhouse gas impacts into the cumulative effects section of your document. The guidance document listed below provides template language and links to assist you in understanding the potential future changes in the surrounding environment.

Indirect Impacts Analysis

Indirect effects are analyzed as part of the discipline specific environmental review. They should be discussed in the section of the environmental document. See Section 412.02(1) of the EPM for guidance.

  • Framework for analyzing indirect effects Flow Chart (pdf 88 kb)

Cumulative Impacts Analysis

The cumulative impact analysis should begin early in project development, usually during the NEPA scoping process. As the process continues, use the gathered data to further refine the cumulative impact analysis. The following eight--step process serves as a guide for identifying and assessing cumulative impacts. Note that the steps are iterative and may not necessarily be sequential. As new information becomes available, it could alter decision making resulting in changes in methods to avoid and/or minimize impacts and thereby changing the cumulative effects.

  • 8-Step Process Flow chart (pdf 21 kb)
  • Description of Step 1 (pdf 56 kb)
  • Description of Step 2 (pdf 68 kb)
  • Description of Step 3 (pdf 69 kb)
  • Description of Step 4 (pdf 65 kb)
  • Description of Step 5 (pdf 65 kb)
  • Description of Step 6 (pdf 63 kb)
  • Description of Step 7 (pdf 56 kb)
  • Description of Step 8 (pdf 58 kb)
  • Example Analysis (pdf 32 kb)

Example Document