Changes

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Performance of filter strips has also been evaluated based on the Roadside Vegetated Treatment Sites Study <ref name='Barrett2003'/> and the BMP Retrofit Pilot Study <ref>California Department of Transportation (Caltrans). 2004. BMP Retrofit Pilot Program, Final Report, CTSW-RT-01-050. Sacramento, CA.</ref>. These studies concluded that concentration reductions consistently occur for TSS and total [[heavy metals]] and frequently for dissolved metals. [[Water quality#Nutrients|Nutrients]] concentrations remained generally unchanged.  

Performance of filter strips has also been evaluated based on the Roadside Vegetated Treatment Sites Study <ref name='Barrett2003'/> and the BMP Retrofit Pilot Study <ref>California Department of Transportation (Caltrans). 2004. BMP Retrofit Pilot Program, Final Report, CTSW-RT-01-050. Sacramento, CA.</ref>. These studies concluded that concentration reductions consistently occur for TSS and total [[heavy metals]] and frequently for dissolved metals. [[Water quality#Nutrients|Nutrients]] concentrations remained generally unchanged. In a recent international research review on processes for improving stormwwater quality treatment of grass swales and vegetated filter strips, Gavric et al. note that while understanding of hydrology and hydraulics of these stormwater control measures is adequate, there are knowledge gaps in understanding water quality treatment processes, particularly for nutrients, traffic associated organic contaminants, and bacteria (Gavric et al., 2019 <ref>Gavric.S, Leonhardt, G., Marsalek, J., Viklander, M. 2019. Processes improving urban stormwater quality in grass swales and filter strips: A review of research findings. Science of the Total Environment. v 669. pp. 431-447. https://www.sciencedirect.com/science/article/pii/S0048969719310502?via%3Dihub</ref>).

'''NOTE:'''Water quality performance declines when vegetation cover on the filter strip falls below 80 %.

'''NOTE:'''Water quality performance declines when vegetation cover on the filter strip falls below 80 %.

[[Category:Performance]]

[[Category:Performance]]