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Project Mitigation Cost Case Studies

The Washington State Department of Transportation (WSDOT) is committed to maintaining our existing infrastructure and improving the operations and safety of our transportation system. One of the integral parts of our project development and construction program is WSDOT’s environmental policy and implementation efforts. As a part of being good stewards of the environment, WSDOT conducts all of its activities in accordance with the most current environmental protection practices. The Department also meets or exceeds its commitments by either avoiding, minimizing or appropriately mitigating adverse environmental impacts. Fulfilling these commitments requires considerable effort during all phases of a project including planning, development, construction, maintenance, and operation of our transportation systems and facilities. Strategic measures are taken in order to integrate the built and natural environments, protecting our state’s environmental assets and resources. These measures are the “mitigation” we do to facilitate successful projects and meet our agency’s environmental objectives and commitments.

Environmental mitigation costs on WSDOT highway projects are considered by some to be too costly while others believe that it’s the right thing to do regardless of cost. This presents the challenge of striking a balance between costs and providing the appropriate amount and type of mitigation. These case studies illustrate mitigation features provided for specific projects, their costs, and the drivers behind their incorporation into the projects.

2013 Report Volume 4
WSDOT Project Environmental Mitigation Costs - Case Studies (Full Report, pdf 3.4 mb)
Executive Summary (pdf 422 kb)

2009 Report Volume 3
WSDOT Mitigation Costs- Full Report (pdf 3.4 mb)
Executive Summary (pdf 207 kb)
Methodology (pdf 537 kb)

2009 Case Studies

  1. SR 16 Burley Olalla Interchange
  2. I-5/SR 16 Westbound Nalley Valley Interchange
  3. I-5 Grand Mound to Maytown Widening
  4. US 290 Starr Rd. Intersection Turn Lanes
  5. SR 270 Pullman to Idaho State Line
  6. SR 24 – SR 241 to Cold Creek Passing Lanes
  7. US 12 Frenchtown to Walla Walla
  8. SR 539 Ten Mile Rd. to SR 546 Widening - Stage 1
  9. SR 522 UW/Cascadia Community College Campus Access
  10. SR 518 SeaTac Airport to I-5/I-405 I/C
  11. I-5/SR 502 Interchange
  12. SR 500/I-205 Interchange Improvements
  13. US 2/97 Peshastin East Interchange
  14. US 2/97 Wenatchee Trail Connection

Observations and Conclusions
Appendix (Permits/Why we mitigate?)

2006 Report Volume 2

Overview (pdf 319 kb)
Methodology (pdf 732 kb)
2006 Project Case Studies & Cost per Lane Mile (pdf 524 kb)

2006 Case Studies

  1. I-5 Everett, SR 526 to US 2 HOV (pdf 447 kb)
  2. I-405 Kirkland, SR 520 to SR 522 (pdf 1.39 mb)
  3. I-5 Tacoma HOV Improvements (pdf 2.43 mb)
  4. SR 16 HOV - Union to Jackson (pdf 1.96 mb)
  5. I-5 Tukwila HOV - Pierce to Tukwila Stage 2 (pdf 554 kb)
  6. SR 270, Pullman to Idaho State Line (pdf 1.86 kb)
  7. US 12 Walla Walla - Attalia Vicinity (pdf 751 kb)

Appendix (pdf 71 kb)
2006 Executive Summary (pdf 478 kb)

2003 Report Volume 1

Executive Summary
 (pdf 1.19 mb)
Project Case Studies Overview (pdf 75 kb)

2003 Case Studies

  1. US 2/20/153 Emergency Bridge Scour Repair (pdf 549 kb)
  2. SR 20 Bannon Creek to Aeneas Valley Road (pdf 886 kb)
  3. I-5 Overcrossing Marvin Road Interchange (pdf 623 kb)
  4. US 395 Hillsboro Street Interchange (pdf 434 kb)
  5. I-5 Maytown to 93rd Avenue (pdf 504 kb)
  6. US 12 McNary Pool to Attalia (pdf 538 kb)
  7. SR 510 Martin Way to Pacific Avenue (pdf 640 kb)
  8. I-90 Evergreen Road Interchange (pdf 793 kb)
  9. SR 14 SE 192nd Avenue Interchange (pdf 660 kb)
  10. I-90 Argonne to Sullivan Interstate Widening (pdf 768 kb)
  11. SR 18 - 180th to Maple Valley (pdf 1.29 mb)
  12. SR 202 - SR 520 to Sahalee Way (pdf 1.51 mb)
  13. I-90 Sunset Way Interchange (pdf 1.33 mb)
  14. SR 18 Maple Valley to Issaquah Hobart Road (pdf 1.56 mb)