Increases in impervious surfaces caused by urbanization has led to higher volumes and rates of stormwater runoff that transports urban pollutants directly into natural waterways. Bioretention cells (BRCs) are vegetated soil systems designed to intercept stormwater runoff and reduce loads of water and contaminants discharged to surface waters. Nitrogen removal efficiency is highly variable and improvements are constrained by a poor understanding of the physical, biological, and chemical processes that occur within a BRC. The objectives of this study are to characterize and quantify the microbial communities in a range of existing BRCs, and determine which design factors have the greatest impact on denitrification, a microbial process responsible for removing nitrogen from stormwater. We sampled 23 BRCs throughout MD, VA, and NC, and quantified patterns in populations of denitrifying bacteria, denitrification potential, and microbial community structure within the soil medium. We found the greatest denitrifier populations and denitrification potential in the upper layer of the soil medium, which does not coincide with the internal water storage zone that is engineered to harbor anaerobic conditions favorable to denitrifying bacteria at the bottom of recent BRC designs. Results indicate that BRC vegetative cover, soil media nitrogen, and organic carbon concentrations are among the variables that facilitate nitrifying and denitrifying bacteria populations in BRCs. Bacterial community composition was most different between the top and bottom samples of the BRCs while fungal community composition differed most by BRC vegetative cover. Both fungal and bacterial community compositions were influenced by nitrogen and carbon concentrations. / Master of Science

Watershed-based stormwater management (WSM) has been proposed as more effective for stormwater management than traditional methods of controlling stormwater, which are carried out based on jurisdictional lines at the parcel-scale. Because WSM considers the watershed as a total unit, this method is considered to be more effective in reducing problems associated with stormwater management including environmental degradation and flooding. However, larger watersheds encompass smaller watersheds, and therefore WSM can be implemented at a wide range of scales. There has been little research on what scale is most appropriate, and more specifically, only a modest amount of work has taken stakeholder opinion into account. The specific objectives of this study are to determine: 1) if watershed scale is an important factor in WSM, 2) whether stakeholder opinion has an effect on the appropriate scale used in WSM, and 3) what scale is most appropriate for WSM, if scale is an important factor. To meet these objectives, we delineated sub-watersheds within a watershed in southwestern Virginia, surveyed stakeholders within the watershed on their opinions of stormwater management methods, and compared the results at both watershed scales using statistical tests and decisions support software. The results of this study have important implications for geographic scale in WSM as well as the use of qualitative data in determining appropriate geographic scale in matters of implementation in the field of planning. / Master of Science

With new government regulations and emerging knowledge of the risk to the environment posed by the failure of stormwater pipelines, stormwater infrastructure asset management is becoming increasingly important in the U.S. An essential aspect of asset management practice is the accurate performance assessment of one's assets. This paper presents a weighted factor framework to determine the performance of stormwater pipes. This paper prepares a list of 50 parameters affecting the performance of stormwater pipelines; the list is based on a review of the literature, existing asset management plans, and feedback from utilities. This list is broken down into essential and preferential parameters. Indeed, not all utilities necessarily possess sufficient resources to collect such a large set of parameters. This study also develops a three-level hierarchical structure of the degradation of stormwater pipeline infrastructure. The structure consists of five failure modules and the essential parameters only. On the basis of the survey results gathered from 10 utilities across the EPA regions, the study combines the essential parameters into a performance index. The index is a scale of 1 to 5, similar to the National Association of Sewer Service Companies' Pipeline Assessment and Certification Program grading system. Grade 1 implies excellent condition and Grade 5 implies collapse is imminent. / Master of Science

Stormwater pipe infrastructure collects and conveys surface runoff resulting from rainfall or snowmelt to nearby streams. Traditionally, stormwater pipe systems were integrated with wastewater infrastructure through a combined sewer system. Many of these systems are being separated due to the impact of environmental laws and regulations; and the same factors have led to the creation of stormwater utilities. However, in the current ASCE Infrastructure Report Card, stormwater infrastructure is considered a sub-category of wastewater infrastructure. Stormwater infrastructure has always lacked attention compared to water and wastewater infrastructure. However, this notion has begun to shift, as aging stormwater pipes coupled with changes in climatic patterns and urban landscapes makes stormwater infrastructure more complex to manage. These changes and lack of needed maintenance has resulted in increased rates of deterioration and capacity. Stormwater utility managers have limited resources and funds to manage their pipe system. To effectively make decisions on allocating limited resources and funds, a utility should be able to understand and assess the performance of its pipe system. There is no standard rating system or comprehensive list of performance parameters for stormwater pipe infrastructure. Previous research has identified performance parameters affecting stormwater pipes and developed a performance index using a weighted factor method. However, the weighted performance index model does not capture interdependencies between performance parameters. This research developed a comprehensive list of parameters affecting stormwater pipe performance. This research also developed a performance index using fuzzy inference method to capture interdependencies among parameters. The performance index was evaluated and validated with the pipe ratings provided by one stormwater utility to document its effectiveness in real world conditions. / Master of Science / Stormwater pipe infrastructure collects and conveys the surface water resulting from rainfall or snowmelt to nearby streams. Traditionally, stormwater pipe system was integrated with wastewater infrastructure by combined sewer system. Environmental regulations forced creation of stormwater utilities and separate stormwater system, however, according to ASCE infrastructure report, stormwater infrastructure has been considered a sub-category of wastewater infrastructure. Stormwater infrastructure has always lacked attention compared to water and wastewater infrastructure. However, this notion has to shift, as aging stormwater pipes coupled with changes in climatic patterns and urban landscapes makes stormwater infrastructure complex to manage resulting in increased rate of deterioration and design capacity. Stormwater utility managers have limited resources and funds to manage their pipe system. To effectively make decisions on allocating limited resources and funds, a utility should be able to understand and assess the performance of its pipe system. There is no standard rating system for assessing the condition of stormwater pipe infrastructure. This research developed an index using fuzzy inference method to capture the interdependencies. Fuzzy inference method basically captures the interdependencies between parameters using if-then rule statements. Parameters are individual elements affecting the performance of stormwater pipes. The performance index was evaluated and validated with the pipe ratings provided by one stormwater utility to document its effectiveness in real world conditions.

Purpose: Climate change and increased proportion of hard surfaces due to urbanization is causing problems with flooding. Although it has been known for a long time that traditional stormwater management needs to be complemented, progress towards Sustainable Drainage Systems, SuDS, is slow. Techniques to locally handle storm water are available for most situations, but there is a lack of knowledge and experience. The aim of this thesis is to present a proposal on how implementation of SuDS can be promoted in urban development projects in Jönköping municipality. Method: Using literature review, interviews, document analysis and observation a qualitative study was conducted in two urban development projects; Ekostaden Augustenborg in Malmö and Munksjöstaden in Jönköping. Findings: The majority of the stormwater management techniques available in Augustenborg have also been discussed in Munksjöstaden by Jönköping municipality. Only one third of the techniques which has been discussed will be realized. Jönköping municipality lacks clear goals and a vision that is integrated into the planning process, which can explain this. During the interviews the site conditions were presented as arguments to why SuDS is difficult to implement. However the analysis showed that it is the other conditions that are decisive, something that also the scientific studies indicated. In order to promote the implementation of SuDS general and project-specific actions were elaborated. Implications: The local plan is the municipality’s sharpest tool for control of the physical development and demands must be submitted in the local plan in order to promote SuDS. The municipality needs to reprocess a practice level and equate SuDS with traditional stormwater management in order to make relevant demands on developers. To promote the implementation of SuDS, the authors suggests that Jönköping municipality carry out a pilot project focusing on sustainable stormwater management in an upcoming urban development project. Limitations: Since the thesis only includes two projects, there is a limitation of the conditions treated. Since the other conditions and the recommended actions are based on the factors identified in a national survey, the applicability is considered to be good. Although the project-specific actions are based on Jönköping municipality, it is possible for other municipalities to apply the PDSA-wheel to the extent that is suitable for the municipality. / Syfte: Klimatförändring och urbanisering med ökad andel hårdgjorda ytor orsakar problem med översvämningar. Trots att det sedan länge är känt att den traditionella dagvattenhanteringen behöver kompletteras går utvecklingen mot Sustainable Drainage Systems, SuDS, långsamt. Tekniker för att ta hand om dagvattnet lokalt finns för de flesta situationer men det saknas kunskap och erfarenhet. Målet med arbetet är därför att presentera ett förslag på hur implementering av SuDS kan främjas i stadsbyggnads-projekt i Jönköpings kommun. Metod: Med hjälp av litteraturstudie, intervjuer, dokumentanalys och observation har en kvalitativ studie genomförts på två stadsbyggnadsprojekt; Ekostaden Augustenborg i Malmö och Munksjöstaden i Jönköping. Resultat: Majoriteten av de tekniker för dagvattenhantering som finns i Augustenborg har diskuterats även i Munksjöstaden från Jönköpings kommuns sida. Det visade sig dock att endast en tredjedel av det som diskuterats kommer att förverkligas. Detta kan bland annat förklaras av att Jönköpings kommun saknar tydliga mål och en vision som är integrerad i planeringsprocessen. Vid intervjuerna lyftes platsen förutsättningar fram som argument till varför SuDS är svårt att tillämpa. Analysen visade dock att det är de övriga förutsättningarna som är avgörande, något som även de vetenskapliga studierna pekat på. För att främja implementeringen av SuDS har därför generella och projektspecifika åtgärder riktade mot de övriga förutsättningarna utarbetats. Konsekvenser: Detaljplanen är kommunens skarpaste verktyg för att styra den fysiska bebyggelsen och för att främja SuDS är det därför viktigt att det finns krav i detaljplanen. Kommunen behöver upparbeta en praxisnivå och likställa SuDS med traditionell dagvattenhantering för att kunna ställa relevanta krav på exploatörer. För att främja implementeringen är författarnas förslag att Jönköpings kommun genomför ett pilotprojekt med fokus på hållbara dagvattenlösningar i ett kommande stadsbyggnadsprojekt. Begränsningar: Eftersom arbetet endast innefattar två projekt finns det en begränsning i vilka förutsättningar som behandlats. Eftersom de övriga förutsättningarna och de rekommenderade åtgärderna utgår från faktorer som identifierats i en nationell enkät-undersökning bedöms ändå tillämpligheten vara god. Även om de projektspecifika åtgärderna utgår från Jönköpings kommun, är det möjligt för andra kommuner att tillämpa PGSA-hjulet i den omfattning som passar den aktuella kommunen.

Sustainable Built Environments Senior Capstone Project / During Tucson rainstorms, many roads and neighborhoods experience high levels of flooding on the city’s street networks. This phenomenon creates unsafe road conditions, damage to the road infrastructure, and excessive urban stormwater runoff that is potentially polluted. The vast quantities of impervious surfaces in the urban landscape impede the rainwater’s ability to infiltrate the ground, thus resulting in increased volumes of runoff during a rainstorm. Stormwater management is used by municipalities and communities to address the previously mentioned adverse impacts of stormwater runoff. Various techniques and strategies used in stormwater management include, low impact development (LID), green infrastructure, and better site design (BSD) strategies implemented during design stages to reduce stormwater runoff levels. In addition, local governments can establish stormwater utilities and policies in order to help address and better manage the issue of stormwater runoff within urban areas. The primary research questions of this study will include: What are the most effective best management practices and techniques to address urban runoff? What combination of best management practices and government policies will be the more effective in addressing Tucson’s urban runoff problem? Accordingly, this study will examine a variety of policies and techniques to address stormwater runoff, and then, based on this information, provide a suggestion of the best practices and techniques that may be feasible for implementation in Tucson.

Sustainable Built Environments Senior Capstone Project / During Tucson rainstorms, many roads and neighborhoods experience high levels of flooding on the city’s street networks. This phenomenon creates unsafe road conditions, damage to the road infrastructure, and excessive urban stormwater runoff that is potentially polluted. The vast quantities of impervious surfaces in the urban landscape impede the rainwater’s ability to infiltrate the ground, thus resulting in increased volumes of runoff during a rainstorm. Stormwater management is used by municipalities and communities to address the previously mentioned adverse impacts of stormwater runoff. Various techniques and strategies used in stormwater management include, low impact development (LID), green infrastructure, and better site design (BSD) strategies implemented during design stages to reduce stormwater runoff levels. In addition, local governments can establish stormwater utilities and policies in order to help address and better manage the issue of stormwater runoff within urban areas. The primary research questions of this study will include: What are the most effective best management practices and techniques to address urban runoff? What combination of best management practices and government policies will be the more effective in addressing Tucson’s urban runoff problem? Accordingly, this study will examine a variety of policies and techniques to address stormwater runoff, and then, based on this information, provide a suggestion of the best practices and techniques that may be feasible for implementation in Tucson.

Mikroplast, här definierat som plastobjekt mindre än 5 mm, befaras kunna göra stor skada på vattenlevande djur. Fram tills idag har studier av mikroplastreduktion främst utförts i kommunala avloppsreningsverk där mycket av plasten avskiljs. De stora spillvattenflödena gör ändå reningsverken till betydande utsläppspunkter av mikroplast till sjöar och hav. Information har hittills till stor del saknats om mikroplastförekomst i dagvatten, vilket ofta släpps ut orenat och i större volymer än spillvatten. Förekomst av mikroplast >20 µm (>0,02 mm) har undersökts för tre tätorters dagvatten samt för två avloppsreningsverks utloppsvatten. Avskiljning av mikroplast har undersökts för två spillvattenvåtmarker och två dagvattendammar. Båda anläggningstyper är relativt billiga och effektiva när det gäller reduktion av tungmetaller och övergödande näringsämnen. Örsundsbro våtmark och våtmark Alhagen tar båda emot behandlat spillvatten från kommunala avloppsreningsverk. I våtmark Alhagen finns även ett inlopp för dagvatten från Nynäshamn. Till dagvattenanläggningen Korsängens vattenpark leds en stor del av Enköpings dagvatten, medan Tibbledammen tar emot det dagvatten som kommer från Kungsängen i Upplands-Bro kommun. Vatten från anläggningarnas inlopp och utlopp, samt från två punkter inuti våtmark Alhagen har pumpats genom 20 µm-filter och 300 µm-filter. Provtagningen har kompletterats med insamling av mindre vattenvolymer som har filtrerats på laboratorium. Kvantifiering av mikroplast har gjorts med hjälp av stereomikroskop och vanligt förekommande objekts material har undersökts genom FTIR-spektroskopi. I våtmark Alhagens inkommande spillvatten var mikroplastkoncentrationen 4 objekt/liter, vilket liknar de koncentrationer andra svenska studier uppmätt i behandlat spillvatten. I inkommande vatten till Örsundsbro våtmark var koncentrationen över 950 objekt/liter, långt över vad andra svenska studier uppmätt i helt obehandlat spillvatten. I dagvatteninloppen var mikroplastinnehållet 5,4–10 objekt/liter, vilket indikerar på att mikroplatsutsläpp via dagvatten kan befaras vara minst lika stora som via spillvatten. I alla anläggningars inkommande vatten, förutom i våtmark Alhagens dagvatteninlopp, uppmättes höga koncentrationer av rödfärgade partiklar. Partiklarna kan vara av plast eller av annat okänt material och är till utseendet relativt lika de som andra studier påträffat i svenska kustvatten. Svarta partiklar påträffades i alla inflöden och ofta i mer än 100 gånger högre halter än de för mikroplast och röda partiklar, förutom i våtmark Alhagens spillvatteninlopp där de röda partiklarna var något fler. Partiklarna tros kunna vara däck- och vägrester eller förbränningspartiklar. Alla anläggningar visade på en tydlig avskiljning, ofta 90-100 %, för mikroplast, svarta och röda partiklar >20 µm. Till följd av resultatet samt anläggningarnas variation i ålder, storlek och utformning bör dagvattendammar och anlagda våtmarker generellt kunna förväntas fungera som effektiva barriärer mot spridning av mikroplast, svarta partiklar och röda partiklar. / Microplastics (MPs), here defined as plastic objects smaller than 5 mm, are suspected to cause great harm to fish when released into lakes and oceans. Studies of MP retention have until recently mainly been done for sewage treatment plants (STPs), where much of the plastics are shown to be retained in the sludge. However, due to large water flows in STPs, they can be seen as significant points for the spreading of MPs to recipient waters. Today there isn’t much information to be found about MP contents in stormwater. Stormwater is often released untreated and depending on climate it can be released in greater volumes than sewage water from urban areas. The occurrence of MPs >20 µm (>0.02 mm) has been studied in two STP effluents, and in stormwater from three urban catchments. The retention of MPs has been studied for two stormwater ponds, and for two free water surface wetlands constructed for tertiary treatment of sewage. Wetland Alhagen and Örsundsbro wetland both receive the effluents of secondary STPs. In wetland Alhagen there is also a stormwater inlet from the town of Nynäshamn. To the stormwater pond Korsängens vattenpark, stormwater is lead from the town of Enköping, while the stormwater pond Tibbledammen receives stormwater from Kungsängen in Upplands-Bro municipality. Influents and effluents from the facilities, as well as water from two points within wetland Alhagen was pumped through 20 µm and 300 µm filters. In addition, water from every sampling point was collected in minor volumes for later filtration carried out in a laboratory. Quantification was done with microscopy and a number of objects were analyzed with FTIR spectroscopy for material determination. In wetland Alhagen, the sewage inlet contained 4 MPs/liter, which is similar to results for STP effluents in other Swedish studies. In Örsundsbro wetland, the incoming water contained more than 950 MPs/liter, far greater than what other studies have shown for untreated sewage. The MP concentrations in the three stormwater inlets were between 5.4-10 MPs/liter. This indicates that untreated stormwater could be seen as a pathway for MPs at least as big as treated sewage. In almost all inlets, characteristic red particles were found in great numbers and in sizes of 20-300 µm. Analysis of some of the red particles indicated that they contained plastic while others were of unknown materials. The particles had a similar appearance to red particles commonly found in Swedish coastal waters. Black particles, a kind of microscopic particles that may originate in tyre wear (i.e. MPs) or combustion, was also found in large quantities. Except for in the main influents of wetland Alhagen, where the number of red particles was slightly higher, the black particles were always found in far greater numbers than both regular MPs and red particles (often >100x greater). The retention of MPs, black particles and red particles >20 µm was high in all the facilities, often around 90-100 percent. Based on these results and the variation of size, design and year of construction, stormwater ponds and constructed free water surface wetlands can be seen as effective barriers against the spreading of MPs.

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.

Rainfall derived inflow and infiltration (RDII) is a cause of sanitary sewer overflows and sewers exceeding capacity before the end of their design lives, but it is not well understood. Several methods exist to model RDII in existing sanitary sewers. These models are not applicable for design, which is frequently accomplished by applying constant unit rates. Two analytical probabilistic models are developed to estimate the contribution of RDII to peak flow and volume. The analytical models have been tested against computer simulations using long-term rainfall records and parameters calibrated using actual field data. One model relies on calibrated parameters from the RTK method; a commonly used method requiring a time-consuming calibration process. The second model relies on the R-value parameter of the RTK method, and a time of concentration parameter. By providing better information to designers, these analytical models aim to improve engineering decision-making in the design of sewer systems.