what we do

NEPA Documentation

Streamlining environmental solutions

Parametrix is recognized as a go-to firm in the West when it comes to developing and delivering high quality environmental documentation on the most complex and controversial transportation projects.  We understand NEPA and state environmental laws and assist agencies in navigating the process. We have developed hundreds of environmental documents for FHWA and state DOTs. Our documents ensure accountability, improve decision-making, engage the public, and protect critical elements of the natural and built environment. Our staff routinely trains environmental professionals nationally on improving the quality of NEPA documents and streamlined environmental program approaches.

SR 520 Bridge Replacement | Parametrix
SR 520 Bridge Replacement and HOV Program 
Seattle to Redmond, Washington
Client: WSDOT
Partner: HDR Engineering & CH2M Hill

At $4.65 billion, the SR 520 program is one of the largest public infrastructure projects in Washington State. The program is composed of the Pontoon Construction project, Eastside Transit and HOV project, and the I-5 to Medina Bridge Replacement and HOV project. As prime consultant for the Trans-Lake Washington Study and as a member of the GEC team for the SR 520 program, Parametrix has provided NEPA documentation for the project, including all preliminary engineering to support the EIS. Through this work, a wide range of alignment, profile, and structural design options have been considered.

Other major technical challenges have included construction phasing on a narrow corridor with only one alternate route; creation of lidded sections over the highway at six locations; developing a tolling plan for revenue generation to assist with funding ; analyzing possible effects of tolling on system performance and congestion management; managing and treating stormwater runoff from the proposed bridge; and developing avoidance and mitigation approaches where trade-offs between the effects to the natural and the built environment are likely. In our work on this project, Parametrix has served as the State’s principal advisor on the broad range of engineering and regulatory compliance issues presented by the overlapping interests of 30 jurisdictions and community interest groups.

  • Grand Conceptor Award, ACEC, Washington, 2017
  • Gold Award, Structural Systems, ACEC Washington, 2017
  • 2040 Vision Award, Puget Sound Regional Council, 2016
  • Excellence in Design (Engineering), DBIA, 2016
  • National Award of Merit in Transportation,  DBIA, 2016
  • Quality of Life/Community Development Award,  WASHTO, 2016


  • Alaskan Way Viaduct | Parametrix

    Alaskan Way Viaduct Replacement Program

  • Parametrix NEPA Documentation - I-5 Columbia River Crossing, Vancouver Washington to Portland, Oregon

    I-5 Columbia River Crossing

  • Lynnwood Link Extension | Parametrix

    Lynnwood Link Extension

  • NMDOT On-Call Environmental | Parametrix

    NMDOT On-Call Environmental Services

  • Portland-Milwaukie LR | Parametrix

    Portland-Milwaukie Light Rail Project EIS

  • SR 520 Bridge Replacement and HOV Program