Highway Runoff: Characterization, Controls and Iron Oxide Coated Sands as Engineering Amendments in Sand Filter
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Most highway and construction runoff originates from non-point or diffused sources. This runoff contains environmental pollutants, which when transferred to sensitive receiving waters, can result in deterioration of receiving water quality and downstream aquatic habitat. Unlike point source runoff such as industrial and sewage treatment plant discharge, which is comparatively easy to monitor, control and treat, non-point source runoff needs to be extensively researched to characterize its constituents and properties. This allows determination of the effect on receiving waters, in order to devise effective and economic techniques to contain or treat it. Commonly, stormwater controls or best management practices (BMPs) are incorporated by agencies and state department of transportations to treat or contain highway runoff depending on the purpose of a stormwater control. The work performed in this study consists of two parts: first, characterization of stormwater runoff from an interstate highway in Georgia for comparison of conditions before, during, and after construction, and second study of the field performance of a sand filter BMP, along with engineered amendments used for sorptive and thermal pollution control. In the first part of this study, highway runoff quality in Georgia, within the GDOT right of way, was characterized. Furthermore, factors affecting highway runoff quality were investigated. In-situ parameters were analyzed for temporal changes in water quality indicators. The effect of construction runoff and highway runoff during construction or precipitation events can contribute to either acute or chronic pollution of receiving water. In this study, the effect of construction runoff on a receiving stream was also investigated and compared with periods during and after construction. Temporal analysis of stream water quality indicators was conducted using wavelets to observe the behavior of stream water quality indicators at different temporal scales. In the second part of this study, a sand filter located in Georgia was studied for its performance in reducing contaminants and compared with other sand filters in United States, with an emphasis on design parameters. Sand filters, especially the ones with preceding sedimentation basins, perform well in removal of floatables, suspended solids and pollutants associated with suspended solids. Additionally, the potential of using iron oxide coated sands as engineered amendments in sand filters was tested as a means to enhance the BMPs performance in removing dissolved fractions of pollutants as well as diffusing thermal pollution. Laboratory prepared iron oxide coated sands as simulants were used to study their thermal behavior and interaction with dissolved fraction of metals.