Increases in impervious surfaces associated with urbanization change stream hydrology by increasing peak flow rates, storm-flow volumes and flood frequency, and degrade water quality through increases in sediment, nutrient, and bacteria concentrations. In response to water quality and quantity issues within the Stroubles Creek watershed, the Town of Blacksburg and Virginia Tech designed and constructed two innovative stormwater best management practices (BMPs). The goal of this project was to evaluate the effectiveness of a bioretention cell and a CU-Structural Soil™ infiltration trench. BMP construction was completed in July 2007. Twenty-nine precipitation events were monitored over a period of five months between October 2007 and March 2008. For each storm, inflow and outflow composite samples were collected for each BMP and analyzed for suspended sediment, total nitrogen, total phosphorus, fecal coliform bacteria and E-coli bacteria. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were then compared to evaluate how well each BMP reduces stormwater flows, decrease peak runoff rates and improves water quality of stormwater runoff. Results for the bioretention cell indicate average reductions in stormwater quantity, sediment, total nitrogen, total phosphorus and fecal coliform bacteria that exceeded 99% by mass. The CU-Structural Soil™ infiltration trench produced reductions in stormwater quantity, total phosphorus and sediment that averaged 60%, 45% and 51%, respectively. Preliminary bacteria results indicated that both BMPs served as sources of E-coli, and the infiltration trench served as a source of fecal coliform bacteria. / Master of Science

Stormwater runoff is one of the leading causes of water quality impairment in the U.S. Bioretention systems are ecologically engineered to treat stormwater pollution and offer exciting opportunities to provide local climate change resiliency by reducing peak runoff rates, and retaining/detaining storm volumes, yet implementation is outpacing our understanding of the underlying physical, biological, and chemical mechanisms involved in pollutant removal. Further, we do not know how performance will be affected by increases in precipitation, which are projected to occur in the northeastern U.S. as a result of climate change, or if these systems could act as a source or sink for greenhouse gas emissions. This research examines the design, construction, and development of monitoring methods for bioretention research, using the University of Vermont (UVM) Bioretention Laboratory as a case study. In addition, this research evaluates mobilization patterns and pollutant loads from road surfaces during the "first flush" of runoff, or the earlier part of a storm event. Finally, this research analyzes the comparative pollutant removal performance of bioretention systems on a treatment by treatment basis. At the UVM Bioretention Laboratory, eight lined bioretention cells were constructed with monitoring infrastructure installed at the entrance and at the subterranean effluent. A conventional, sand and compost based, bioretention soil media was compared to a proprietary media engineered to remove phosphorus, called Sorbtive Media™, under simulated increases in precipitation. Two drought tolerant vegetation mixes, native to the northeast, were compared for sediment and nutrient retention. Each treatment was sampled for soil gas emissions to determine if it was a source or a sink. The monitoring infrastructure designs used in this research allowed for the effective characterization of pollutant mass loads entering and exiting bioretention. Cumulative mass loads from stormwater were found to be highest for total suspended solids, followed by total Kjeldahl nitrogen, nitrate, non-labile phosphorus and soluble reactive phosphorus, in descending order by mass. Total suspended solids, total Kjeldahl nitrogen, and non-labile phosphorus mass were well retained by all bioretention treatments. However, the compost amendment in the conventional soil media was found to release labile nitrogen and phosphorus, far surpassing the mass loads in stormwater. When compared with conventional media, Sorbtive Media™ was highly effective at removing labile phosphorus and was also found to enhance nitrate removal. Systems containing deep-rooted vegetation (Panicum virgatum) were found to be particularly effective at retaining both labile and non-labile constituents. Overall, none of the bioretention treatments were found to be a significant source of N2O and were small sinks for CH4 in most treatments.

The urban drainage in Brazil has been focused historically in the hydraulic conduction of the runoff. From the 1990\'s a paradigm shift was initiated with the study of LID practices, aiming at adapting the local scenario to compensate the urbanization effects on runoff and reestablish the water cycle as close as possible to the natural. However, there is still a gap regarding the integration of qualitative-quantitative variables and their comprehension. In addition, the temperate climate regions have been in the center of the studies, with still few knowledge about other climates influence in its efficiency. Therefore, this research aimed to evaluate the operation of a bioretention structure in a subtropical climate region, regarding mainly its pollutant treatment capacity and water retention, in an integrated way. The results indicate a positive use of the bioretention in reducing the exceedance risks, by reducing the peak flow, the total volume and the pollutant load transferred downstream. However, adaptations the implementation and operation stages are necessary for subtropical climates. The local specific characteristics, such as soil highly weathered and rainfall with high intensities in short intervals of time, affect the water and pollutant retention efficiency. Further studies evaluating different applications locals and scales, and treatment key factors must be performed. / A drenagem urbana no Brasil esteve focada historicamente no tratamento hidráulico para a condução do escoamento superficial. A partir da década de 90 se inicia uma mudança de paradigma com o estudo de técnicas compensatórias (TCs), visando adaptar o cenário local para compensar os efeitos da urbanização sobre o escoamento superficial, de forma a manter o ciclo hidrológico o mais próximo possível do natural. No entanto, existe ainda uma lacuna quanto a integração das variáveis quali-quantitativas e sua compreensão. No mais, as regiões de clima temperado estiveram no centro dos estudos, havendo pouco conhecimento sobre a influência de outros climas em sua eficiência. Assim, a presente pesquisa teve como objetivo avaliar a operação de uma estrutura de bioretenção em uma região de clima subtropical, quanto a sua capacidade de tratamento da poluição difusa e retenção hídrica de forma integrada. Para tal, foram monitorados dois dispositivos em escalas distintas, sendo essas laboratório e campo. Os resultados obtidos indicaram um uso promissor da bioretenção em reduzir os riscos de enchente, reduzindo a vazão de pico e o volume total transferido à jusante, assim como a carga total de poluentes. No entanto, adaptações nas etapas de implantação e operação são necessárias para clima subtropical. As características específicas desses locais, como solos altamente intemperizados e regimes de chuva de alta intensidade em pequeno intervalo de tempo, afetam a eficiência de retenção hídrica e retenção de poluente. Novos estudos avaliando diversos locais, escalas de aplicação, e fatores-chave para o tratamento devem ser realizados.

Stormwater runoff from existing impervious surfaces needs to be managed to protect downstream waterbodies from hydrologic and water quality impacts associated with development. As urban expansion continues at a rapid pace, increasing impervious cover, and climate change yields more frequent extreme precipitation events, increasing the need for improved stormwater management. Although green infrastructure such as bioretention has been implemented in urban areas for stormwater quality improvements and volume reductions, these systems are seldom monitored to validate their performance. Herein, we evaluate flow attenuation, stormwater quality performance, and nutrient cycling from eight roadside bioretention cells in their third and fourth years of implementation in Burlington, Vermont. Bioretention cells received varying treatments: (1) vegetation with high-diversity (7 species) and low-diversity plant mixes (2 species); (2) proprietary SorbtiveMediaTM (SM) containing iron and aluminum oxide granules to enhance sorption capacity for phosphorus; and (3) enhanced rainfall and runoff (RR) to certain cells (including one with SM treatment) at three levels (15%, 20%, 60% more than their control counterparts), mimicking anticipated precipitation increases from climate change. Bioretention water quality parameters monitored include total suspended solids (TSS), nitrate/nitrite-nitrogen (NOx), ortho-phosphorus (Ortho-P), total nitrogen (TN) and total phosphorus (TP), which were compared among bioretention cells’ inflows and outflows across 121 storms. Simultaneous measurements of flow rates and volumes allowed for evaluation of the cells’ hydraulic performances and estimation of pollutant load and event mean concentration (EMC) removal. We also monitored soil CO2 and N2O fluxes, as they represent a potential nutrient loss pathway from the bioretention cells. We determined C and N stocks in the soil media and vegetation, which are critical design elements of any bioretention, to determine the overall C and N balances in these systems. Significant average reductions in effluent stormwater volumes and peak flows were reported, with 31% of the storms events completely captured. Influent TSS loads and EMCs were well retained by all cells irrespective of treatments, storm characteristics, or seasonality. Nutrient removal was treatment-dependent, where the SM treatments consistently removed P loads and EMCs, and sometimes N as well. The vegetation and RR treatments mostly exported nutrients to the effluent. We attribute observed nutrient exports to the presence of excess compost in the soil filter media. Rainfall depth and peak inflow rate undermined bioretention performance, likely by increasing pollutant mobilization through the filter media. While the bioretention cells were a source of CO2, they varied between being a sink and source of N2O. CO2 fluxes were orders of magnitude higher than N2O fluxes. However, soil C and N, and plant C and N in biomass was seen to largely offset respiratory CO2-C and biochemical N2O-N losses from bioretention soil. The use of compost in bioretention soil media should be reduced or eliminated. If necessary, compost with low P content and high C: N ratio should be considered to minimize nutrients losses via leaching or gas fluxes. In order to understand trade-offs stemming from compost amendments, we conducted a laboratory pot study utilizing switchgrass and various organic soil amendments (e.g., different compost types and coir fiber) to a sandy loam soil contaminated with heavy metals and studied potential nutrient leaching and pollutant uptake. Addition of organic amendments significantly reduced metal bioavailability, and improved switchgrass growth and metal uptake potential. While no differences in soil or plant metal uptake were observed among the amendments, significant differences in nutrient leaching were observed.

Bioretention gardens are stormwater management practices that offer numerous water quantity and quality benefits. However, previous studies have reported inconsistent removal of nitrogen and phosphorous in these systems. The first phase of this research involved the construction and monitoring of ten vegetated, mesoscale, bioretention cells in a field setting to provide a comparison of the performance of five alternative designs intended to provide nutrient removal. Results indicated that concentrations of total nitrogen and total phosphorous may be reduced by up to 53 and 79%, respectively, in specially designed bioretention gardens. In the second phase of the research, a GIS-based site selection tool was used to identify areas suitable for bioretention implementation based on physical site requirements. Applying this tool to selected urban catchments demonstrated that bioretention gardens may be integrated into existing urban landscapes on a scale large enough to accommodate runoff and associated nutrient loads from small (<15mm) storms.

Bioretention systems are best management practices (BMPs) that make use of the biogeochemical processes within a forest-type ecosystem to provide at-source stormwater retention and pollutant removal. Laboratory studies and field monitoring have shown great potential for water quantity and quality control through the use of bioretention, but reported nutrient removal has been inconsistent between these systems. In particular, the processes involved in the cycling of phosphorus within bioretention systems are not clearly understood. Some studies report high phosphorus removal from bioretention systems, while phosphorus leaching was observed in other systems. Phosphorus is a macronutrient required by all forms of life. It is also an important water pollutant, as it controls algal growth in most freshwater environments. High phosphorus loadings to these aquatic ecosystems can lead to eutrophication, which has significant ecological, environmental and economical impacts. The Bioretention Phosphorus Removal Model (BPRM), an event-based one-dimensional finite difference model, was developed to simulate phosphorus removal in bioretention systems. The model includes four completely-mixed layers to simulate hydrologic processes as well as both soluble and particulate phosphorus transport in a bioretention system. Model processes include evapotranspiration, infiltration, overflow, exfiltration to native soils, underdrain discharge, soluble phosphorus sorption and vegetative uptake, and particulate phosphorus capture. Monitoring data collected by the Toronto and Region Conservation Authority (TRCA) at a bioretention system installed on Seneca College’s King City campus, in Ontario, Canada, was used to evaluate the performance of BPRM. The model was found to overestimate total underdrain discharge volumes, but total phosphorus concentration and mass predictions were found to be useful for design purposes. BPRM correctly predicted phosphorus leaching from the Seneca College bioretention system for all storm events considered but one. The model can be used by practitioners to evaluate the potential for phosphorus leaching in a bioretention system. A detailed sensitivity analysis revealed that BPRM phosphorus transport predictions are particularly sensitive to the drainage properties of bioretention soils, which highlights the importance of hydrologic transport processes for water quality control in bioretention systems. Modelling results suggested that soluble phosphorus desorption from bioretention soils was responsible for phosphorus leaching from the Seneca College bioretention system. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-09-25 17:00:03.173

abstract: Bioretention basins are a common stormwater best management practice (BMP) used to mitigate the hydrologic consequences of urbanization. Dry wells, also known as vadose-zone wells, have been used extensively in bioretention basins in Maricopa County, Arizona to decrease total drain time and recharge groundwater. A mixed integer nonlinear programming (MINLP) model has been developed for the minimum cost design of bioretention basins with dry wells. The model developed simultaneously determines the peak stormwater inflow from watershed parameters and optimizes the size of the basin and the number and depth of dry wells based on infiltration, evapotranspiration (ET), and dry well characteristics and cost inputs. The modified rational method is used for the design storm hydrograph, and the Green-Ampt method is used for infiltration. ET rates are calculated using the Penman Monteith method or the Hargreaves-Samani method. The dry well flow rate is determined using an equation developed for reverse auger-hole flow. The first phase of development of the model is to expand a nonlinear programming (NLP) for the optimal design of infiltration basins for use with bioretention basins. Next a single dry well is added to the NLP bioretention basin optimization model. Finally the number of dry wells in the basin is modeled as an integer variable creating a MINLP problem. The NLP models and MINLP model are solved using the General Algebraic Modeling System (GAMS). Two example applications demonstrate the efficiency and practicality of the model. / Dissertation/Thesis / Masters Thesis Civil Engineering 2016

The urban drainage in Brazil has been focused historically in the hydraulic conduction of the runoff. From the 1990\'s a paradigm shift was initiated with the study of LID practices, aiming at adapting the local scenario to compensate the urbanization effects on runoff and reestablish the water cycle as close as possible to the natural. However, there is still a gap regarding the integration of qualitative-quantitative variables and their comprehension. In addition, the temperate climate regions have been in the center of the studies, with still few knowledge about other climates influence in its efficiency. Therefore, this research aimed to evaluate the operation of a bioretention structure in a subtropical climate region, regarding mainly its pollutant treatment capacity and water retention, in an integrated way. The results indicate a positive use of the bioretention in reducing the exceedance risks, by reducing the peak flow, the total volume and the pollutant load transferred downstream. However, adaptations the implementation and operation stages are necessary for subtropical climates. The local specific characteristics, such as soil highly weathered and rainfall with high intensities in short intervals of time, affect the water and pollutant retention efficiency. Further studies evaluating different applications locals and scales, and treatment key factors must be performed. / A drenagem urbana no Brasil esteve focada historicamente no tratamento hidráulico para a condução do escoamento superficial. A partir da década de 90 se inicia uma mudança de paradigma com o estudo de técnicas compensatórias (TCs), visando adaptar o cenário local para compensar os efeitos da urbanização sobre o escoamento superficial, de forma a manter o ciclo hidrológico o mais próximo possível do natural. No entanto, existe ainda uma lacuna quanto a integração das variáveis quali-quantitativas e sua compreensão. No mais, as regiões de clima temperado estiveram no centro dos estudos, havendo pouco conhecimento sobre a influência de outros climas em sua eficiência. Assim, a presente pesquisa teve como objetivo avaliar a operação de uma estrutura de bioretenção em uma região de clima subtropical, quanto a sua capacidade de tratamento da poluição difusa e retenção hídrica de forma integrada. Para tal, foram monitorados dois dispositivos em escalas distintas, sendo essas laboratório e campo. Os resultados obtidos indicaram um uso promissor da bioretenção em reduzir os riscos de enchente, reduzindo a vazão de pico e o volume total transferido à jusante, assim como a carga total de poluentes. No entanto, adaptações nas etapas de implantação e operação são necessárias para clima subtropical. As características específicas desses locais, como solos altamente intemperizados e regimes de chuva de alta intensidade em pequeno intervalo de tempo, afetam a eficiência de retenção hídrica e retenção de poluente. Novos estudos avaliando diversos locais, escalas de aplicação, e fatores-chave para o tratamento devem ser realizados.

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Stormwater runoff may contain high levels of pollutants and is regulated by the Federal National Pollution Discharge Elimination System (NPDES). Stormwater bioretention (BR) systems are often used to satisfy these regulations. BR systems collect accumulated runoff that leaches into groundwater. A greenhouse study evaluated nutrient and metal removal among plant species that are typically found growing in BR systems. A field demonstration study assessed citric acid enhanced metal bioaccumulation potential under typical BR system conditions. The greenhouse experiment examined pollutant retention, and bioaccumulation potential for six plant species undergoing three hydraulic and pollutant loads. Results verified there was 98% recovery of total phosphorous over the study period. Biomass increased with higher hydraulic and pollutant loads for all species. Phragmites australis, Carex praegracilis, and Carex microptera took up significantly more total phosphorous and nitrogen mass into shoots than Typha latifolia, Scirpus valid us, and Scirpus acutus. This study also found that 89% of applied metals were removed within the top 27 em of soil in all treatments. Similar results were found regarding copper, lead, and zinc concentrations and bioaccumulation. Carex praegracilis, and Carex microptera exhibited higher metal distribution in plant tissue and exfiltrate, and lower distribution in the soil media than the other species. This indicated species differences in biological and chemical processes taking place within the simulated BRsystems. The field experiment investigated citric acid enhanced metal bioaccumulation potential among three different plant species under representative BR conditions. Citric acid significantly increased metal concentrations in the soil pore water for the planted treatments, but this did not result in increased metal uptake into plant tissue. However, notable differences were found among species, where Carex microptera accumulated more AI, Cr, Cu, and Fe in the above ground tissue than Helianthus maximiliani and Typha /atifolia (except for Cu in Helianthus). These results provide greater insight into the biological and chemical process that affect transport, uptake and translocation of nutrients and metals, and confirm the importance of species selection in BR systems to optimize nutrient and metal retention and recovery from stormwater runoff to minimize subsequent groundwater pollutant loading.