Evaluation of Best Management Practices for Highway Runoff Control (2006) / Chapter Skim
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Pages 25-36
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25 4.1 Overview Identifying BMPs by unit operations and assessing BMPs partially on the basis of performance observed from monitoring data require an understanding and assessment of the water chemistry characteristics of an urban rainfall and runoff event (Sansalone et al. 1997; Sansalone et al.
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Various site characteristics may affect stormwater quality, including the following: • Climate -- including antecedent dry period between storms, average rainfall intensity, storm duration, and amount of snowmelt. Arid and semi-arid regions generally experience longer dry periods than areas with higher rainfall amounts.
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for more than 2,300 discrete storm events. Although the NURP data did not indicate statistically significant differences in pollutant concentrations from different land uses (i.e., residential, commercial, and mixed)
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• Season (snowmelt data are not included) , • Watershed area percent imperviousness, and • Time.
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effluent quality, and maintenance frequency, especially in areas that may observe a high variability in water quality. Influent chemical characteristics (such as pH and alkalinity)
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similar transport characteristics as other metals (Strecker 1994)
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(2002) found that dissolved mass, even for relatively insoluble metals, dominates particulate-bound mass at the edge of a highway shoulder, while major peaks in a runoff hydrograph tend to correspond to a decrease in the dissolved heavy metal mass, resulting from increased partitioning of metals to solids mobilized by higher flows.
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the dissolved and particulate form of the first flush, and lead was dominant only in the particulate form (Sansalone et al.
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BMP if appropriate maintenance measures are not undertaken (Sansalone et al.
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Most pollutants exhibit lower loadings for snowmelt than for rainfall events; however, hydrocarbons have been observed to average 30% higher loadings for snowmelt (Hoffman and Quinn 1987)
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• Speciation (the particular chemical form in which an element exists in water)
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between the range end points are also shown in Figure 4-6 ("exact") from which it can be seen that end point computations should suffice for most computations.
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