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An Evaluation of Highway Runoff Filtration SystemsBy Sean Tenney, M.S., Michael E. Barrett, M.S., Joseph F. Malina, JR., P.E., Randall J. Charbeneau, P.E., George H. Ward Ph.D. ABSTRACT A number of permanent runoff controls were constructed along new highways in the Edwards aquifer recharge zone and their performance has been monitored since the highways opened. The control systems consist of a hazardous material trap, a sedimentation basin, and a vertical sand filter. The filter is constructed as part of the wall of the basin and held in place with filter fabric and rock gabions. Numerous problems have been documented with these systems, mostly in conjunction with the performance of the vertical sand filter. Sedimentation was the most important pollutant removal mechanism for the runoff control systems. Modifications of runoff control systems which focus on extending the detention time of the basins may be more effective in controlling suspended solids in runoff than enhancing the filter performance. Scour and resuspension of sediments was observed in the detention basins. Sediment and suspended solids removal efficiencies can be increased and maintenance requirements reduced by the installation of rock gabions, baffles or another device which reduces resuspension of solids. Laboratory, bench-scale filtration columns using various media were investigated at the Center for Research in Water Resources. The performance of filtration media and adsorptive media was evaluated. Media selected for these experiments include a well-sorted medium grain size sand, a fine aggregate, grade 5 gravel, compost, and zeolites. The data indicate that the compost is a very effective medium. It out performed the other media for the removal of TSS, oil and grease, and metals. However, the compost decomposes and subsequent breakthrough occurs. The medium sand performed well for the removal of TSS and most of the metals. Zeolites, pea gravel and grade 5 gravel were not effective filtration media. The highlighted links that follow are connected to Adobe pdf files of the corresponding material. To view them you must have the Adobe Acrobat Reader 3.0. View the Whole Report...(610Kb) |
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