Browsing by Subject "swales"
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Item Characterization of Runoff Quality from Paved Low-Volume Roads and Optimization of Treatment Methods(Minnesota Department of Transportation, 2020-09) Natarajan, Poornima; Weiss, Peter T.; Gulliver, John S.Vehicular traffic contributes a large fraction of the pollutant load in stormwater runoff from roadways. While runoff concentrations have historically been characterized for urban roads with high average daily traffic (ADT), the runoff quality from paved rural roads that have relatively low ADT is largely unknown. In this study, runoff from low-volume roads (ADT < 1500) in Minnesota was monitored at 10 locations during 174 rainfall events in 2018 and 2019. The initial concentrations of total suspended solids (TSS), total phosphorus (TP), nitrate+nitrite, and heavy metals in the runoff, and the relationship between measured concentrations and site-specific conditions were analyzed. Concentrations were strongly influenced by the surrounding land use and soil type. Sites with agricultural lands had higher mean TSS, TP, and zinc concentrations, and lower nitrite+nitrate concentrations than wooded sites, which can be related to the type of soil that would get transported onto the roadways. When compared to existing urban runoff quality data, the estimated event mean concentrations (EMCs) in rural road runoff were substantially lower for copper and zinc and marginally lower for TSS, TP and nitrate+nitrite. Based on detailed cost-benefit analysis of various roadside treatment options, roadside drainage ditches/swales are recommended for cost-effective treatment of runoff from low-volume roads over ponds, sand filters and infiltration basins. Example road widening projects were also modeled to determine how stormwater management requirements can be achieved using drainage ditches/swales.Item Enhancement and Application of the Minnesota Dry Swale Calculator(Center for Transportation Studies, University of Minnesota, 2016-04) Garcia-Serrana, Maria; Gulliver, John S.; Nieber, John L.Roadside drainage ditches (roadside grassed swales) typically receive runoff directly from the road and water is infiltrated over the side slope of the ditch, similar to a filter strip. Water that runs off the side slopes then has a further opportunity to infiltrate as it flows down the center of the ditch. This research focuses on the volume reduction performance of grassed drainage ditches or swales by infiltration. A total of 32 tests were performed during three seasons in four different highways maintained by MnDOT in the Twin Cities metro area. The field-measured saturated hydraulic conductivities (Ksat) correspond to hydrologic soil group A, even though the soil textures indicated correspondence to hydrologic soils groups A, B and C. This means that the infiltration performance is better than expected for these types of soils. In addition, the trend was to have more infiltration when the saturated hydraulic conductivity was higher and for a greater side slope length, as expected. A coupled overland flow-infiltration model that accounts for shallow concentrated flow has been developed. The predicted infiltration loss has been compared with the actual infiltration loss determined from the monitored field tests. In this manner, the validity of the model as well as the associated soil hydraulic and surface geometry parameters have been evaluated. Using the coupled infiltration-overland flow model, multiple scenarios with sensitivity analyses have been computed, and the results have been used to generate a simplified calculator to estimate the annual infiltration performance of a grassed roadside drainage ditch.Item Performance of Low Impact Development Practices on Stormwater Pollutant Load Abatement(St. Anthony Falls Laboratory, 2011-08) Ahmed, Farzana; Gulliver, John S.; Nieber, John L.Stormwater runoff is a major contributor to the impairment of surface waters in the United States. With high connected impervious surfaces and concentrated human activities, urban land uses are involved in discharging most of the stormwater volume and pollutant loadings during a storm. Stormwater pollution prevention involves the installation and maintenance of stormwater low impact development (LID) practices in urban areas. These include infiltration basins and trenches, porous pavements, rain gardens, vegetative swales, and filter strips. LID practices infiltrate and detain stormwater to reduce stormwater runoff volume and improve water quality via filtration and other processes. The reasons for assessing the performance of the LID practices include fulfilling stormwater permit regulatory requirements, engineering and design due diligence, scheduling maintenance and TMDL studies. The results of the assessment allow for an improved understanding of the role of the various system components (i.e. soil, plants, etc.) in pollutant removal and volume reduction. This project is designed to assist MS4s in the assessment of their stormwater BMPs and the utilization of these BMPs in watershed TMDL analyses. Objective B of this project focuses on the infiltration performance of low impact development (LID) practices. The infiltration capacity testing developed for rain gardens (Asleson, et al. 2009) was to be refined, altered and expanded for other types of LID practices including infiltration basins and trenches, vegetative swales and filter strips. The Modified Philip Dunne (MPD) infiltrometer is implemented as a low-effort, low-cost method to determine saturated hydraulic conductivity, a predictor of infiltration capacity. This infiltration tests have been performed on rain gardens, infiltration basin, swales and turf areas.