Greenhouse Gas Analysis

Congestion on I-5 through Hayden Island.

Congestion creates a concentration of idling cars along I-5 that contribute to local and regional greenhouse gas emissions.

The primary purpose of CRC’s Greenhouse Gas Emissions (GHG) analysis was to compare alternatives presented in the Draft EIS. The methodology used to calculate greenhouse gas emissions was based on energy consumed during construction and operation of the CRC project and the associated carbon dioxide that results. For example, the combustion of diesel to power buses through the project area emits carbon dioxide and other gases as a byproduct. Carbon dioxide is the primary component of greenhouse gases.

A similar approach was used to study GHG emissions for the Final EIS, with refinements to include a larger study area and the effects of bridge lifts and collisions.

GHG findings in the Final EIS concluded that the “build” alternatives resulted in fewer GHG emissions than a no build alternative. The LPA is expected to reduce regional emissions (including Washington, Clackamas, Multnomah, and Clark Counties) by approximately 0.5 percent. At a more local level (the 12.2-mile length of I-5 surrounding the CRC project area), the LPA is expected to reduce emissions by roughly 5.4 percent. The build alternative would carry lower volumes of traffic due to higher transit use, a tolled bridge, and higher traffic speeds in the project area.

Opportunities exist in the future to reduce GHG emission further through:

Improvement in system management to decrease Vehicle Mile Traveled (VMT)
Use of lower-carbon fuels
Vehicle efficiency

Project staff will continue to work with both states and transportation planning agencies to improve system management and decrease VMT.

GHG Emissions Review Panel Study affirms project analysis

During the selection process for the Locally Preferred Alternative, local partner agencies requested an independent review of greenhouse gas emissions analysis.

In 2008, a panel of independent experts reviewed and evaluated the greenhouse gas emissions analysis presented in the Draft EIS. The Greenhouse Gas Emissions Expert Review Panel found the CRC analysis and conclusions to be reasonable. The Panel agreed with the CRC finding that the Locally Preferred Alternative would generate lower greenhouse gas emissions than the no build alternative. Suggestions were provided to refine the calculations for the Final EIS. The Panel’s detailed findings can be found in the Greenhouse Gas Emission Analysis Expert Review Panel Report.

GHG analysis receives national recognition

In 2009 the CRC Greenhouse Gas Emissions and Climate Change Evaluation was awarded a National Environmental Excellence Award by the National Association of Environmental Professionals, stating that the project “demonstrates a novel method to assess the impacts of greenhouse gas emissions and through the environmental review process identify a less overall impacting alternative for a complex transportation project.”