Webinar: Improving Recreational Trail Accessibility with a Volcanic Ash Treatment

Thursday, February 23, 2023, 10:00am to 11:00am PST
Charles (C.J.) Riley and Ashton Greer, Oregon Institute of Technology
PDH: 1 | AICP: 1



Recreational trails serve as valuable transportation corridors and support the health of users. Wheelchair accessibility of recreational trails depends on a variety of conditions, including slope, cross-slope, and surface characteristics. This project focused on improving the firmness and stability of a 0.2-mile section of trail that was otherwise accessible. The existing trail surface consisted of loose ¼” off-specification aggregate on native soil. A volcanic ash-Portland cement binder, studied in prior research, was batched, distributed, mixed, wetted, and compacted on site to improve the firmness and stability of the surface resulting in a smoother surface with less rolling resistance. The webinar will present details of the trail conditions, materials, batching, placement, and surface characteristics before and after treatment.


Attendees will be able to:

  • Describe and differentiate pozzolanic and cementitious behavior
  • Describe how to practically use a raw volcanic ash with little processing as a binder for a soil-cement
  • Measure trail surface firmness and stability using a rotational wheel penetrometer
  • Mobilize small groups to practically treat a recreational trail with a cementitious binder to improve the firmness and stability of the trail surface


This webinar is based on a study funded by the National Institute for Transportation and Communities (NITC) and conducted at the Oregon Institute of Technology (Oregon Tech). Read more about the research, Trail Section Resurfaced Using Volcanic Ash in Oregon, or watch a recap video showing how the project was done.


Charles (C.J.) Riley, Oregon Institute of Technology

Dr. C.J. Riley is professor and graduate program director in the Civil Engineering Department at Oregon Institute of Technology. He is a Fellow of the American Society of Civil Engineers and has taught solid mechanics and structural engineering for over 15 years with a particular focus on hands-on demonstrations, field investigations, and active learning. Dr. Riley is a licensed professional engineer (OR) with professional experience in highway bridge rating and design as well as vibration-based structural health monitoring methods.




Ashton Greer, Oregon Institute of Technology

Ashton Greer is an assistant professor of civil engineering at Oregon Tech, with a focus on water resources. She is particularly interested in western water management and is passionate about utilizing remote sensing and spatial analysis techniques to develop solutions to complex water issues.





This 60-minute webinar is eligible for 1 hour of professional development credit for AICP (see our provider summary). We provide an electronic attendance certificate for other types of certification maintenance.


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This webinar is hosted by the Transportation Research and Education Center (TREC) at Portland State University. The research was funded by the Summit Foundation and the National Institute for Transportation and Communities (NITC), a program of TREC and one of seven U.S. Department of Transportation national university transportation centers. The NITC program is a Portland State-led partnership with the University of Oregon, Oregon Institute of Technology, University of Utah and new partners University of Arizona and University of Texas at Arlington. We pursue our theme — improving mobility of people and goods to build strong communities — through research, education and technology transfer.