Browsing by Subject "Highway runoff"
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Item Permeable friction courses : stormwater quality benefits and hydraulic profile modeling(2013-05) Sampson, Laura Carter; Barrett, Michael E.This paper presents the results of a study on the effectiveness of porous overlays on urban highways. Permeable Friction Course (PFC) is a layer of porous asphalt applied to the top of conventional asphalt highways at a thickness of around 50 mm. PFC is often installed for safety and noise benefits, and is being seen as an emerging technology for meeting environmental requirements for stormwater discharge. The first objective of the study was to determine the impact of porous asphalt on the quality of stormwater runoff on highways with a curb and gutter drainage system. The quality of highway stormwater runoff was monitored before and after the installation of PFC on an eight-lane divided highway in the Austin, Texas area for 2 years. Observed concentrations of total suspended solids from PFC are 92% lower than those in runoff from the conventional pavement. Concentration reductions are also observed for nitrate/nitrite and total amounts of phosphorus, copper, lead, and zinc. The data shows that the results with curb and gutter are consistent with past results where runoff sheet flowed onto vegetated shoulders. The effect of two different binder compositions is also compared, showing an increase in zinc when recycled rubber is used. The second objective focuses on the drainage capabilities of PFC. While porous overlays can reduce stormwater accumulation on roadways, capacity at high rainfall intensities is limited. Installing subgrade underdrains within PFC could further improve stormwater conveyance. This research attempts to model the hydraulic profile of runoff as it approaches an underdrain with varying flow rates and grades. The results could assist TxDOT in the sizing and configuration of drains based on rainfall intensity and roadway geometry.Item A protocol to evaluate the adsorptive removal of dissolved copper and zinc from highway runoff(2014-05) Ernst, Clayton Owen; Katz, Lynn EllenThe increasing urbanization of landscapes significantly alters the surface water hydrology of impacted watersheds. As a side effect, stormwater discharges to receiving water bodies are often of decreased quality due to pollutants deposited on impervious urban surfaces being entrained by runoff. A pertinent example of this problem is the presence of copper and zinc in highway runoff. Both copper and zinc have been shown to exert toxic effects on aquatic micro- and macro-biota. Copper in particular has been shown to harmfully disrupt the olfactory nervous system of fish species at concentrations as low as 3 [mu]g/L. To meet these limits, treatment of highway runoff for the removal of copper and zinc is necessary. However, due to the complexities associated with the behavior of heavy metals in natural systems, the appropriateness of removal techniques will necessarily depend on a variety of system-specific factors and chemical characteristics of highway runoff. Adsorption has been shown to be generally effective in the removal of dissolved heavy metals, but the choice of adsorptive media is again dependent on system-specific parameters. This study developed and evaluated a column testing protocol that can be used to quickly and reliably evaluate adsorptive removal of dissolved heavy metals from highway runoff. The protocol is demonstrated in an evaluation of iron oxide, manganese oxide, crab shell, concrete, and bone meal media for removing dissolved copper and zinc from highway runoff. The performance of these media was assessed as a function of various runoff characteristics including pH, ionic strength, alkalinity, and total organic carbon. The methodology was used to show that iron oxide media in combination with crab shell or concrete media provided the most effective removal of copper and zinc from highway runoff. Through this study, the convenience, flexibility, and robustness of the proposed protocol are compellingly established.Item Stormwater quality benefits of a permeable friction course on a curbed section(2012-05) Houston, Alexandra Victoria; Barrett, Michael E.; Charbeneau, Randall J.This paper presents the results of an experimental study aimed at determining the impact of porous asphalt on the quality of stormwater runoff on highways with a curb and gutter drainage system. A porous overlay, also known as permeable friction course (PFC), is a layer of porous asphalt applied to the top of conventional asphalt highways at a thickness of 50 mm to improve safety and water quality and reduce noise. The quality of highway stormwater runoff was monitored before and after the installation of PFC on an eight-lane divided highway in the Austin, Texas area for 15 months. Observed concentrations of total suspended solids from PFC are more than an 80% lower than from the conventional pavement. Concentration reductions are also observed for nitrate/nitrite and total amounts of phosphorus, copper, lead, and zinc. The data shows that the results with curb and gutter are consistent with past results where runoff sheet flowed onto vegetated shoulders.