Browsing by Subject "Swales"
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Item Assessing and Improving Pollution Prevention by Swales(Center for Transportation Studies, University of Minnesota, 2014-08) Ahmed, Farzana; Natarajan, Poornima; Gulliver, John S.; Weiss, Peter T.; Nieber, John L.Roadside swales are drainage ditches that also treat runoff to improve water quality, including infiltration of water to reduce pollutant load. In the infiltration study, a quick and simple device, the Modified Philip Dunne (MPD) infiltrometer, was utilized to measure an important infiltration parameter (saturated hydraulic conductivity, Ksat) at multiple locations in a number of swales. The study showed that the spatial variability in the swale infiltration rate was substantial, requiring 20 or more measurements along the highway to get a good estimate of the mean swale infiltration rate. This study also developed a ditch check filtration system that can be installed in swales to provide significant treatment of dissolved heavy metals and dissolved phosphorous in stormwater runoff. The results were utilized to develop design guidelines and recommendations, including sizing and treatment criteria for optimal performance of the full-scale design of these filters. Finally, the best available knowledge on swale maintenance was combined with information obtained from new surveys conducted to develop recommendations for swale maintenance schedules and effort. The recommendations aim toward optimizing the cost-effectiveness of roadside swales and thus provide useful information to managers and practitioners of roadways. The research results and information obtained from this study can thus be used to design swale systems for use along linear roadway projects that will receive pollution prevention credits for infiltration. This will enable the utilization of drainage ditches to their full pollution prevention potential, before building other more expensive stormwater treatment practices throughout Minnesota and the United States.Item Comparing Properties of Water Absorbing/Filtering Media for Bioslope/Bioswale Design(Minnesota Department of Transportation, 2017-11) Johnson, Kurt; Cai, Meijun; Patelke, Marsha; Saftner, David; Swanson, JoshDrainage from highways, particularly the first flush of runoff, contains high levels of contaminants such as suspended solids, metals, and organics. To restrict the discharge of polluted stormwater, the National Pollutant Discharge Elimination System (NPDES) State Disposal System (SDS) General Permit issued by Minnesota Pollution Control Agency (MPCA) in 2013 requires that the first inch of stormwater runoff from new impervious should be held on site through infiltration, harvesting or reuse. Multiple types of infiltration materials have been studied in the laboratory and the field, but few studies have considered the application of local materials for best management practices (BMP). The objective of this project is to determine the characteristics of various naturally occurring water adsorbing and filtering media, such as peat and muck, found along road construction projects in northern Minnesota. Salvage and reuse of these materials during road construction will be evaluated for stormwater treatment, including absorption, infiltration, filtration, and pollutant capture, in constructed vegetated slopes along highway right of ways. The naturally occurring material will be compared to leaf and grass feedstock compost.Item Iron-Enhanced Swale Ditch Checks for Phosphorus Retention(Minnesota Department of Transportation, 2019-07) Natarajan, Poornima; Gulliver, John S; Weiss, Peter TIron-enhanced ditch checks in roadside swales were developed specifically for capturing dissolved phosphorus and dissolved metals from roadway runoff in both urban and agricultural environments. One iron-enhanced ditch check constructed along CR 15 (formerly TH 5) in Stillwater, Minnesota, was monitored during 40 storm events from 2016 to 2018. The iron-enhanced sand filter insert generally captured phosphate, yielding lower phosphate concentrations and mass load reductions that varied between 22% and 50% during several events. However, the cumulative phosphate retention in the filter insert decreased from 42% in 2015 to 30% in 2016, 25% in 2017, and 23% in 2018. The filter insert was not an effective retention device for dissolved copper and zinc. The overall ditch check’s performance, although unexceptional in 2016 and 2017, appeared to improve in 2018. Sampling issues likely contributed to the low performance measured until 2017. The 2018 water sample collection method provided a better estimate of the ditch check’s performance and roughly matched that of the filter insert. Synthetic runoff testing supported the level of treatment achieved during storm events. Phosphate load from the degrading topsoil and the overutilization of the bottom filter media most likely affected overall treatment performance. Design improvements and recommended maintenance actions were developed based on the lessons learned from field monitoring. The iron-enhanced ditch check can improve net phosphate retention through roadside swales, as long as the recommended maintenance actions are performed as scheduled.