American Society of Civil Engineers


Treating Highway Bridge Deck Runoff Using Bioretention and a Swale


by S. K. Luell, (Graduate student, Department of Biological and Agricultural Engineering, North Carolina State University, Campus Box 7625, NCSU, Raleigh, NC 27612. E-mail: skluell@ncsu.edu), W. F. Hunt, (Associate Professor and Extension Specialist, Department of Biological and Agricultural Engineering, North Carolina State University, Campus Box 7625, NCSU, Raleigh, NC 27612. E-mail: Bill_Hunt@ncsu.edu), and R. J. Winston, (Extension Associate Engineer, Department of Biological and Agricultural Engineering, North Carolina State University, Campus Box 7625, NCSU, Raleigh, NC 27612. E-mail: Ryan_Winston@ncsu.edu)
Section: 8th Urban Watersheds Management Symposium, pp. 364-374, (doi:  http://dx.doi.org/10.1061/41173(414)40)

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Document type: Conference Proceeding Paper
Part of: World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability
Abstract: A full sized bioretention cell, an undersized bioretention cell, and a swale were constructed in a bridge deck easement of I-540 in Knightdale, NC to treat bridge deck runoff. Runoff was piped from the northbound and southbound lanes to the bioretention cells and swale, respectively. Flow-weighted, composite water quality samples were collected at the inlets and outlets of the cells and the swale and were tested for nutrients, TSS, and heavy metals. The mean effluent concentration of TN released by the large cell, small cell, and swale were 0.38, 0.54, and 1.00 mg/L, respectively, while effluent TP concentrations were 0.10, 0.13, and 0.15 mg/L, respectively. Median TSS effluent concentrations were 16, 21, and 29 mg/L in the large cell, small cell, and swale, respectively. The large and small cells reduced runoff volumes by about 50% and 31%, respectively, for storms less than 2.54 cm. The swale reduced volumes by 3% for storms less than 2.54 cm. While both bioretention cells substantially reduced nutrient and sediment loads, the large cell outperformed the small cell. The small cell provided support for retrofitting undersized systems in areas with limited space. Both cells achieved greater pollutant and volume reductions than the swale.


ASCE Subject Headings:
Highway bridges
Bridge decks
Runoff
North Carolina
Stormwater management