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United States. Americans with Disabilities Act of 1990, Nature trails for people with visual disabilities -- Design and construction, Volcanic ash tuff etc. -- Pacific Northwest -- Analysis, Pozzuolanas


The Americans with Disabilities Act (ADA) provides specific guidelines and requirements that must be met in terms of accessibility. However, in the case of unpaved trails, the requirements are less defined. An ADA trail must be firm, stable and slip resistant. Some compacted aggregate material may meet this definition, but degrade over time and can no longer be ADA compliant. The benefits of using unpaved surfaces for ADA trails include fit to the natural environment, cost, sustainability and environmental benefits such as increased permeability. If an unpaved surface can be improved with the use of an additive, more could be used as ADA accessible trails. Naturally occurring, volcanic ash from the eruption of Mt. Mazama is a natural pozzolan. This study examined using this natural pozzolan, in addition to other materials, as a naturally occurring binder. This binder was applied to existing and newly created compacted aggregate trails in the laboratory and the field to determine the benefit as a stabilizer. ADA accessibility tools such as the rotational penetrometer were used to determine if the surface is improved to a firm and stable surface. By determining a low-cost, sustainable solution for improvement of ADA accessible trails, more people will have access and connectivity will increase in our community. This study outlines the long-term benefits of using naturally occurring, volcanic ash as a binder applied topically to unpaved trails and discusses the expected increases to firmness and stability.


This is a final report, NITC-RR-1131, from the NITC program of TREC at Portland State University, and can be found online at:

The Project Brief associated with this research can be found at:



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