Jy S. Wu

Suspended sediment removal by vegetative filter strip treating highway runoff.

Structural best management practices (BMPs) are often used to mitigate the impact of storm water runoff on receiving waters. Vegetative filter strips (VFS) are an example of a structural BMP that has been used to treat storm water and highway runoff. Physical factors affecting the performance of VFS include pollutant characteristics, vegetation composition and density, soil properties, and the physical dimensions of the filter strip. In this study, field-suspended sediment data were collected from an experimental VFS treating highway runoff in eastern North Carolina. Field data were used to test the design concepts of the VFS treatment train and to validate a simulation model for evaluating the impact of these physical factors on sediment removal as a function of filter strip length. It was concluded that the experimental filter strip was effective in removing more than 85% of the incoming total suspended sediment (TSS). Simulation results support field observations that a 10-m or longer filter strip can retain most of the medium and large particles (> 8 μ m) transported in runoff. Simulations also indicate infiltration loss is largely responsible for the retention of small-size sediment particles (< 8 μ m). Saturated hydraulic conductivity and initial water contents have little effects on TSS removal. The condition of vegetative coverage, in particular vegetation density, is another factor affecting the performance of filter strip.

Hydrologic Connectivity for Highway Runoff Analysis at Watershed Scale

State transportation agencies are a potential stakeholder in the total maximum daily load process and, in some cases, NPDES stormwater permits could be issued …

Combined load and leachant pH effects on contaminant release from fly ash

Several studies have been performed recently on the suitability of particulate waste materials as substitute aggregate in load bearing and geoenvironmental structures. To investigate the long-term performance and durability of these recycled materials, the coupled effects of the interacting fluid chemistry and applied load are herein analysed experimentally. The leachability of heavy metals (copper, selenium and arsenic) from coal combustion fly ash as a function of load (under uni-axial stress of about 570 kPa, 1425 kPa, 2850 kPa and 5707 kPa) was assessed in a specially designed leaching device at leachant pH levels of 4, 6 and 8. The rate of release of Cu from fly ash is decreased by applied uni-axial load when compared to that of column leaching for the low L/S ratio of about 1. Release of Se and As is accelerated by uni-axial stress greater than 1425 kPa compared to leaching in a column.