Environmental Manual

Publication Number
M 31-11
Publication Version
M 31-11.27
Manual Manager
Environmental Manual Coordinator: Barb Steusloff; 564-233-9708; barbara.steusloff@wsdot.wa.gov
Environmental Services Office, Engineering and Regional Operations Division
Environmental policies and procedures for department employees and consultants

The Environmental Manual M 31‑11 is a compilation of environmental policies and processes that is to be used as a guidance resource for the Washington State Department of Transportation (WSDOT) and its environmental consultants. The Environmental Manual outlines WSDOT’s legal requirements related to environmental, cultural, historic, and social resources and is a keystone of WSDOT’s environmental compliance strategy.

The information contained in the Environmental Manual supplements the wide range of technical expertise among WSDOT Engineering, Environmental, Highway and Local Programs, and Planning staff, as well as local agencies and consultants. It provides consistent, current, and accurate guidelines for complying with federal and state environmental laws and regulations for all phases of project delivery. The guidance provided by the Environmental Manual assists WSDOT project proposals by encouraging early consideration and documentation of environmental issues during project scoping, alternative development, and preliminary design. It also provides guidance on complying with environmental requirements during the construction and maintenance phases of a project as well as addressing utilities and surplus property sales.

This manual includes information from many sources other than WSDOT, including a variety of state and federal agencies. Every effort has been made to make this information as current as possible. However, it is the user’s responsibility to ensure that any action taken to comply with the excerpted or referenced material is based on the most current information available from these outside sources.

Updating this manual is a continuing process, due to the ever‑changing status of environmental policies. Users are encouraged to submit the Feedback Form on page v to help guide future updates.

Individual Chapters

Contents (PDF 174KB)

Chapter 100 Purpose and overview (PDF184KB)

Chapter 200 Environmental considerations in transportation planning (PDF 274KB)

Chapter 300 Project scoping and programming (PDF 329KB)

Chapter 400 Environmental review (NEPA/SEPA) and transportation decision 
making (PDF 592KB)

Chapter 412 Indirect and cumulative effects (PDF 524KB)

Chapter 420 Earth (Geology and Soils) (PDF 154KB)

Chapter 425 Air Quality, Greenhouse Gases, Energy (PDF 312KB)

Chapter 430 Stormwater and water quality (PDF 341KB)

Chapter 431 Wetlands and other waters (PDF 223KB)

Chapter 432 Special flood hazard area (PDF 803KB)

Chapter 436 Fish, wildlife and vegetation (PDF 453KB)

Chapter 446 Noise (PDF 354KB)

Chapter 447 Hazardous materials (HazMat) and solid waste (PDF 275KB)

Chapter 455 Land use and transportation (PDF 385KB)

Chapter 456 Cultural resources (PDF 527KB)

Chapter 457 Section 4(f) evaluation (PDF 399KB)

Chapter 458 Social and community effects (PDF 313KB)

Chapter 459 Visual impacts (PDF 313KB)

Chapter 460 Environmental justice (PDF 330KB)

Chapter 490 Tracking environmental commitments during design (PDF 208KB)

Chapter 500 Environmental permitting (PDF 279KB)

Chapter 530 Working with Tribes (PDF 207KB)

Chapter 590 Incorporating environmental commitments into contracts (PDF 343KB)

Chapter 600 Construction (PDF 335KB)

Chapter 700 Maintenance and operations (PDF 325KB)

Chapter 800 Utilities, property management, and access (PDF 225KB)

Appendix A Executive orders (PDF 120KB)

Appendix B Interagency agreements (PDF 145KB)

Appendix C Letters, memos, and directives (PDF 1.2MB)


Revision History

December 2023

July 2022

September 2021

August 2021

October 2020

June 2020

June 2019

August 2018

July 2018

June 2018


166,800 electric vehicle

registrations in Washington in 2023, up from 114,600 in 2022.

87 wetland compensation sites

actively monitored on 918 acres in 2023.

25,000 safe animal crossings

in the Snoqualmie Pass East Project area since 2014.