Environmental Manual

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. 

Revision History / Individual Chapters

Publication Date: 
Wednesday, September 22, 2021
Publication Number: 
M 31-11
Last modified: 
09/22/2021 - 12:58
Publication Version: 
M 31-11.25
Manual Manager: 
Ashley Carle; 360-705-7493; CarleAs@wsdot.wa.gov
Environmental Services Office, Engineering and Regional Operations Division
Number of Pages: 
Environmental policies and procedures for department employees and consultants

Individual Environmental Manual Chapters

Contents (pdf 174 KB)
Exhibits (pdf 174 KB)

Chapter 100 Purpose and Overview (pdf 184 KB)

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

Chapter 300  Project scoping and programming (pdf 329 KB)

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

Chapter 412 Indirect and cumulative impacts (pdf 524 KB)

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

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

Chapter 430 Stormwater and Water quality (pdf 341 KB)

Chapter 431 Wetlands (pdf 223 KB)

Chapter 432 Special Flood Hazard Area (pdf 803 KB)

Chapter 433 Groundwater (pdf 264 KB)

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

Chapter 446 Noise (pdf 354 KB)

Chapter 447 Hazardous Materials and Solid Waste (pdf 275 KB)

Chapter 455 Land Use and Transportation (pdf 385 KB)

Chapter 456 Cultural resources (pdf 527 KB)

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

Chapter 458 Social and community effects (pdf 313 KB)

Chapter 459 Visual impacts (pdf 313 KB)

Chapter 460 Environmental justice (pdf 330 KB)

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

Chapter 500 Environmental permitting (pdf 279 KB)

Chapter 530 Tribal Approvals (pdf 207 KB)

Chapter 590 Incorporating environmental commitments into contracts during PS&E (pdf 343 KB)

Chapter 600 Construction (pdf 335 KB)

Chapter 700 Maintenance and Operations (pdf 325 KB)

Chapter 800 Property Management and Disposal (pdf 225 KB)

Appendix A Executive Orders (120 KB)

Appendix B Interagency Agreements (pdf 145 KB)

Appendix C Letters, Memos and Directives (pdf 1.2 MB)


Revision History

  Date Version Complete Revision

2021 September

M 31-11.25

PDF (5.4 MB)

PDF (553 KB)


2021 August

M 31-11.24

PDF (5.5 MB)

PDF (5.5 MB)


2020 October

M 31-11.23

PDF (3.4 MB)

PDF (3.5 MB)


2020 June

M 31-11.22

PDF (3.5 MB)

PDF (3.5 MB)


2019 June

M 31-11.21

PDF (3.5 MB)

PDF (3.4 MB)


2018 August

M 31-11.20

PDF (3.9 MB)

PDF (551 KB)


2018 July

M 31-11.19

PDF (3.9 MB)

PDF (568 KB)


2018 June

M 31-11.18

PDF (3.9 MB)

PDF (3.9 KB)


2017 June

M 31-11.17

PDF (3.8 MB)

PDF (3.8 KB)


2016 October

M 31-11.16

PDF (3.9 MB)

PDF (1.0 KB)


2016 June

M 31-11.15

PDF (3.2 MB)

PDF (2.8 KB)


2015 June

M 31-11.14

PDF (5.7 MB)

PDF (3.2 KB)


2014 June

M 31-11.13

PDF (4.8 MB)

PDF (4.8 KB)


2013 June

M 31-11.12

PDF (4.7 MB)

PDF (1.8 KB)


2012 June

M 31-11.11

PDF (5.8 MB)

PDF (5.9 MB)


2011 June

M 31-11.10

PDF (6.2 MB)

PDF (6.2 MB)


2010 October

M 31-11.09

PDF (8.4 MB)

PDF (8.3 MB)


2010 June

M 31-11.08

PDF (8.9 MB)

PDF (1.4 MB)


2010 February

M 31-11.07

PDF (10.1 MB)

PDF (1.6 MB)


2009 September

M 31-11.06

PDF (8.9 MB)

PDF (7.7 MB)


2008 October

M 31-11.05

PDF (8.6 MB)

PDF (298 KB)


2008 September

M 31-11.04


PDF (466 KB)