Guidelines for Evaluating and Selecting Modifications to Existing Roadway Drainage Infrastructure to Improve Water Quality in Ultra-Urban Areas (2012) / Chapter Skim
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Pages 8-19
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8Characterizing highway pollutants of concern supports the development of retrofit treatment objectives and selection and design of appropriate BMP strategies. 2.1 Retrofit Benefits of Water Quality Characterization Water quality characterization provides a basis for planning, evaluation, and design of BMP retrofit projects.
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9 Receiving Water Issues of Concern Hydromodification together with reduction in sediment supply can significantly intensify the erosion and sediment transport processes in receiving streams and often leads to stream channel adjustment, geomorphic impacts, and loss of habitat and associated riparian species. Retrofit Implications Hydromodification impacts to urban receiving streams are a regulatory issue of concern.
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10 addressed pollutant in urban stormwater. The primary sources of sediments and solids in highway runoff are pavement, tire, and vehicle abrasion (Oregon State University et al., 2006)
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11 l atory requirements, which often specify TSS. Furthermore, SSC measurements can skew BMP performance by showing high mass load reductions when there is diminished or ineffective treatment of the smaller particles that are more strongly associated with some pollutants and are mobilized by smaller, more frequent storms.
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12 and Granato, 2003; Oregon State University et al., 2006)
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13 Caltrans Litter Research Program Caltrans has an ongoing litter research program to evaluate litter management strategies and the effectiveness of various education and treatment BMPs (Caltrans, 2000)
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14 2.2.6 Nutrients Characteristics in Highway Runoff Nutrients are inorganic forms of nitrogen (nitrate, nitrite, and ammonia) and phosphorous.
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15 Receiving Water Issues of Concern DOT studies have found that road salting is not a widespread environmental threat and that impacts from road salting are site specific with greatest impacts occurring near the place of application where concentrations are greatest (MIDOT, 1993)
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16 Concentrations of contaminants in highway runoff have been found to increase as the adjacent land use becomes increasingly urban (e.g., Driscoll et al., 1990; Kayhanian et al., 2003, 2007) , in particular industrial and commercial land uses (Driscoll et al., 1990; Caltrans, 2003a)
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17 2005; Kayhanian and Stenstrom, 2008; Kang et al., 2006; Tucker, 2007)
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18 During cold weather, treatment systems can experience periods of no runoff followed by large volumes of runoff due to rapid snowmelt and/or rain-on-snow events. In other cases, melts can provide slow steady flows with low TSS.
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19 versus allowing the snow to stay in areas where it cannot be treated effectively. 2.4 Sources of Water Quality Information to Support Retrofit Planning Compiling and evaluating existing runoff data is the first step in characterizing highway runoff and receiving water quality.
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