Case Study: Evaluating Road Performance and Sediment Generation during Simulated Wet Weather Hauling

Authors : Erica KEMP, Ben LESHCHİNSKY, Kevin BOSTON

Pages : 22-34

View : 15 | Download : 7

Publication Date : 2016-09-05

Article Type : Research Paper

Abstract :Aggregate roads are the primary means of access to managed forestlands in western Oregon, but may facilitate sediment transport during rainfall, especially with traffic from heavy trucks. This transported sediment, typically in the means of suspended sediment or turbid effluent, may have detrimental effects on aquatic ecosystems, especially when roads are in proximity to creeks, streams and rivers. However, due to past construction practices and difficult terrain, many existing roads are stream-adjacent, and may require retrofitting to address potential delivery of fine sediment from its surface during rainfall. To evaluate a potential treatment to this problem, a heavily-instrumented field test was performed on a reconstructed aggregate forest road in Western Oregon which sought to test the potential of geosynthetic materials to sequester road sediment and improve road performance during wet-weather hauling. A sand filter berm wrapped with a non-woven geotextile provided 70% and more reduction in turbidity when tested under idealized laboratory conditions. Additionally, a geogrid reinforcement placed on the native road subgrade material prior to placing the aggregate layer reduced subgrade pressures experienced during loading, improving mechanical performance. When applied to well-graded aggregate, the geogrid reinforcement reduced rutting, a potential channel for flow of turbid runoff. When applied to a poorly-graded aggregate the geogrid reinforcement reduced relative breakage. Aggregate degradation and road performance may be improved with use of the geogrid reinforcement and road sediment may be effectively sequestered with use of a geotextile-wrapped filter sand berm when applied correctly. Targeted applications of these approaches are recommended where desired levels of road performance and water quality improvement may justify the additional labor and materials required. However, more replicates and larger scale application may address some levels of variability that are difficult to address under the constraints of an intensive field test.
Keywords : Forest roads, Geosynthetics, Wet Weather Hauling, Oregon