Monitoring of a regional stormwater management facility, located on the Virginia Tech campus in Blacksburg VA, was conducted in order to assess its efficacy in reducing nonpoint source pollutant losses downstream. The facility design includes both an upper water quality (wet) pond and a lower 100-yr-event quantity (dry) pond. These on-stream ponds capture both baseflow and storm runoff from the southern portion of the Virginia Tech campus and surrounding lands, and release the water back to the unnamed stream shortly above its conjunction with Stroubles Creek, a tributary of the New River. Monitoring sites for flow measurement, water quality sampling, and biotic assessments (habitat evaluation and rapid bioassessment of benthic macroinvertebrates) were located above and below each of the ponds. Both grab samples and automated samples were collected at these stations. Between 1997 and 1999, water quality grab samples included 35 baseflow samples and 22 stormflow samples. The grab samples were analyzed for concentrations of total suspended solids (TSS), metals, bacteria, and nutrients as well as temperature, pH, dissolved oxygen, conductivity, total organic carbon (TOC), and chemical oxygen demand (COD). Automated flow-weighted sampling was initiated in February of 1999 and results are reported through the end of October 1999. Thirty-three storms in 1999 were monitored for flow and various water quality parameters (TSS, TOC, COD, and nutrients). Pollutant loads and pollutant removal estimates were calculated with regard to the wet pond, dry pond, and the combined facility. Two types of pollutant removal efficiencies were calculated: (1) the EMC efficiency, based on pollutant concentrations from individual storms; and (2) the SOL efficiency, based on pollutant loads, to estimate long-term performance over the study period. Benthic macroinvertebrate sampling and habitat assessment were performed in both 1997 and 1999. In addition, a preliminary investigation of pond characteristics was conducted, including measurements of water quality and composition, sediment deposition and composition, and residence time. As a system, the stormwater management facility appears to have minimum impact on improving the downstream water quality. Pollutant concentrations and loads both appear to increase downstream of the facility as compared to upstream, during both storm event and baseflow periods. Monitoring results of the benthic assemblages showed evidence of moderate to high impairment at all sampling locations, and habitat assessments showed evidence of high sedimentation levels within the stream, even after installation of the stormwater management facility. Total suspended solids (TSS) concentration removal efficiency was 10% for the combined wet pond and dry pond system, much lower than the 80 to 90% TSS removal expected for properly functioning stormwater management facilities (Hartigan, 1989). There is some evidence of sedimentation within the ponds because of a slight reduction in sediment-bound constituent export, but the dissolved nutrient constituents had either very low and most often negative (indicating pollutant export) removal efficiencies. Concentrations of metals measured in the stream often exceeded their respective acute and chronic water quality criteria at all sampling locations. Pollutant removal efficiencies measured in the wet pond are atypical of those reported in the literature (Schueler, 1993). Insufficient residence time (two days compared to the optimal two weeks), and wet pond embankment failure are likely the principal causes of the wet pond's inadequate performance and thus, the inadequate performance of the overall facility. TSS removal efficiencies were low in the wet pond (19% for concentrations and 33% for loads) compared to the 80 to 90% expected for similar ponds. Nevertheless, the wet pond reduced the concentrations of several pollutants typically associated with TSS and not likely to be associated with the fill material for the wet pond embankment. Zinc concentrations in sediment cores were highest near the pond inlet, where the majority of sedimentation occurs. During storm events, the following results were noted. Copper and zinc concentrations in 1998 were lower at the pond outlet as compared to the pond inlet, and TOC concentrations and loads were also reduced by the wet pond (13% for concentrations and 12% for loads). However, sedimentation is also expected to remove phosphorusl, and wet pond phosphorus loads were only reduced by 10% and 3% for orthophosphorus and total phosphorus, respectively. Because the wet pond is undersized with respect to the watershed it serves (surface area less than 1% of the watershed area (0.87 ha), as compared to the 3% ratio often recommended for optimal pollutant removal (Athanas, 1988)), higher removal efficiencies were found during baseflow periods. The greatest reductions in baseflow concentrations were for ammonia (67%), nitrate (57%), total nitrogen (54%), and COD (45%). However, the residence time of two days appears to be insufficient to reduce fecal coliform concentrations in the stream, and over 40% of the fecal coliform samples collected exceeded the water quality standard for contact recreation (DEQ-WQS, 1997). Furthermore, the wet pond did not appear to reduce TSS or TOC during baseflow periods. Export of TSS (-29% EMC efficiency) and TOC (-44% EMC efficiency) from the wet pond during baseflow periods is likely due to the wet pond embankment failure as well as pond eutrophication. Eutrophication processes are favored by the water temperature increase as flow passes through the shallow wet pond. The wet pond increased downstream temperatures by approximately 8°C above inflow temperatures during the summer, and to levels above 21°C which cannot be tolerated by sensitive coldwater species (Schueler, 1987). The dry pond did not remove dissolved nutrient constituents or other pollutants during baseflow periods, but there is some evidence of sedimentation within the dry pond during storm events. During storm events, the dry pond was effective in removing TSS, with a concentration removal efficiency of 69% (EMC efficiency) and loading removal efficiency of 43% (SOL Efficiency). Removal of TKN and total phosphorus (36% and 37% respectively for concentrations) within the dry pond is further evidence of sedimentation within the dry pond. The wet pond embankment was built in 1997, and monitoring occurred during a potential stabilization period when evidence of water quality benefits are slow to appear, especially with respect to downstream habitat and aquatic communities. Some benefits which could have been observed more immediately may have been negated or masked by the progressive erosion of the wet pond embankment as a result of a design flaw. Further complicating the results is the appearance; based on observations of extended drawdown time and results from a water budget analysis in the wet pond (where inflow substantially exceeds inflow); that groundwater interacts with the pond in a complicated fashion, possibly including both recharge and discharge. To fully understand the impact of the stormwater management facility on the water quantity and quality within this tributary of Stroubles Creek, monitoring efforts should continue after the wet pond embankment is repaired and is fully operational. If biotic community improvement is desired, the stabilization period could be defined by the time necessary to flush out accumulated sediment within the channel. Monitoring efforts should also expand to include the investigation of the groundwater regime and water level fluctuations within the wet pond. Further measurements of pollutant removal processes and influences upon those processes within the wet pond should also be considered. Last, the influence of the stormwater management facility on downstream flow regimes should be investigated to assess the adequacy of its performance with regard to flow control and prevention of stream channel degradation. / Master of Science

The environmental issues of storm water in the urban environment is addressed in political policies on many different governance levels. The concept of “sustainable storm water” in Europe uses the natural water cycle as a template for urban drainage, and the EU has a water framework directive (WFD) with a systems approach, using drainage basins as the starting point of all actions. In Stockholm, a new storm water strategy was adopted in 2015 with a sustainability approach, using much of the terminology from the WFD and the Swedish Water & Wastewater Association. To find new aspects related to sustainable development of storm water management in Stockholm, this study used a resilience framework of seven principles to analyse the implementation of the Stockholm storm water strategy (SSWS). A mixed method approach was used for a qualitative study, using interviews and a review of policy documentation as the main data sources, complemented by a desk study of literature on the subject of storm water management, as well as participation in some relevant workshops. To broaden the study, examples from a developing area within the Stockholm municipality, Stora Sköndal, was used, as well as another municipality in the Baltic Sea region; Helsinki (Finland). The SSWS leans on the legislation of the environmental quality standards (EQS) but is lacking in authority coordination on a national and municipal level in Stockholm. Diversity in problem formulations and solutions for infrastructure is high, so is the diversity of involved stakeholders, which is an indication of resilience. This in combination with the structure and communicational links having questionable functionality, leads to a complex and inefficient structure in management of storm water, which undermines the resilience of the system. However, since the SSWS and other connected policies (such as local programmes of measures and sustainability requirements) are new, the system is undergoing change, which shows some level of adaptability and complex adaptive systems (CAS) thinking, another resilience indicator. The implementation of the WFD on a municipal level is also connected to CAS thinking, as well as a polycentric governance system -one of the seven resilience principles of the framework used. Some of the main issues found within this study for building resilience in the SES are related to follow-up and responsibility division. / Miljöfrågor inom dagvatten hanteras i policyarbete på flera olika institutionella nivåer. Begreppet ”hållbart dagvatten” utgår i Europa från den naturliga vattencykeln och EU:s vattendirektiv (WFD) har en systeminriktning som utgår från avrinningsområden istället för andra geografiska gränsdragningar. Stockholms Stad antog en ny dagvattenstrategi 2015 med en hållbarhetsinriktning, som innehåller mycket terminologi från WFD och publikationer från branchorganisationen Svenskt Vatten AB. För att hitta nya aspekter för en hållbar utveckling av dagvattenhantering i Stockholm använder denna studie ett teoretiskt ramverk inom resiliens,, som bygger på sju principer, i en analys av stadens dagvattensstrategi (SSWS). Blandade metoder användes för att genomföra en kvalitativ studie, där policydokument granskades tillsammans med intervjuer av nyckelpersoner, vilket kompletterades med en skrivbordsstudie av litteratur om dagvattenhantering samt deltagande i relevanta workshops. För att bredda studien användes exempel från ett planprogramsområde inom Stockholms kommun, Stora Sköndal, liksom en annan kommun i Östersjöområdet; Helsingfors (Finland). SSWS bygger juridiskt på miljökvalitetsnormerna, men brister i myndighetssamordning på nationell och kommunal nivå i Stockholm. Problemformuleringar och infrastrukturlösningar har hög mångfald, precis som involverade aktörer, vilket är en indikation på att systemet bygger upp resiliens. Detta i kombination med att struktur och kommunikationslänkar är något bristfälliga leder till en komplex och ineffektiv dagvattenhantering, vilket underminerar resiliensen i systemet. Eftersom SSWS och andra relaterade styrdokument (t.ex. lokala åtgärdsprogram och hållbarhetskrav) är nya, genomgår systemet förändringar, vilket visar på anpassningsförmåga och komplext, adaptivt systemtänk (CAS), vilket är en ytterligare resiliensindikator. Implementeringen av WFD på kommunal nivå är också kopplad till CAS-tänkande, liksom ett polycentriskt styrsystem - en av de sju principerna för resiliens i det teoretiska ramverket som används. Några av de huvudsakliga problem för att bygga resiliens som hittades i denna studie är relaterade till uppföljning och ansvarsfördelning.

Atmospheric mercury deposition, known to be a major source of mercury to aquatic and terrestrial environments, was studied at an urban site in Orlando, FL. Precipitation sampling was conducted from September 2003 to May 2006 at a Mercury Deposition Network site located on the University of Central Florida campus. Weekly rainfall and mercury wet deposition data were gathered from this site, which provided the framework of data for this study. Historical mercury wet deposition data from several sites in Florida were used to develop a regression model to predict mercury deposition at any location in Florida. Stormwater runoff from a 2-acre impervious surface at this study area was monitored during the spring and summer of 2005. Runoff water quality was analyzed to characterize mercury dry deposition. Atmospheric monitoring was also conducted during this period to study the interaction of atmospheric constituents on wet and dry deposition patterns. Spatial and seasonal trends for the entire state suggest 80% of Florida's rainfall and mercury deposition occur during the wet season. A strong linear correlation was established between rainfall depth and mercury deposition (R2 = 0.8). Prediction equations for the entire state, for both wet and dry seasons, were strongly correlated with measured data. The results of two unique methods to quantify dry deposition were similar at this site during this study period. Runoff monitored at this site contained significant levels of mercury, primarily in particulate form (58%). The vast majority of particulate mercury was flushed from the surface during storm events, while significant dissolved fractions remained. Runoff mercury concentrations were consistently higher than rainfall mercury, suggesting dry deposition accounted for 22% of total mercury in runoff. Atmospheric monitoring at this location showed gaseous elemental mercury was the dominant form (99.5%) followed by reactive gaseous mercury (0.3%) and particulate mercury (0.2%). Comparison of the contributions of wet and dry deposition suggested 80% of total mercury deposition was wet deposited during this study, while dry deposition accounted for the remaining 20%. Statistical correlations revealed rainfall scavenging of reactive gaseous mercury was the main factor controlling dry deposition.

No description available.

No description available.

An extensive literature survey revealed there have been no in-depth studies of the quantity of water entering Orlando area drainage wells. Previous values ranging from 30 to 85 MGD were based on water supply withdrawal information or gross drainage area estimates. This paper presents a detailed study of the quantity of water entering 208 drainage wells in the Orlando Ubran Stormwater Management Manual (OUSWMM) area. Extrapolation of results to the remaining wells in Orange County is discussed briefly. Field experiments on one 20 in drainage well yielded a mathematical relationship that was reasonable for estimating acceptance rates for drainage wells of all sizes. One hundred seventeen drainage sub-basins have been identified in the 54,000 acre OUSWMM area. Seventy-four of these sub-basins contain or contribute flow to one or more of the 208 drainage wells. Weighted mean daily runoff in the 74 sub-basins was estimated between 39.1 and 53.4 MGD. Storage effects reduce this to 17 to 31 MGD, which is the maximum quantity of runoff available to the drainage wells. Other effects could reduce this more. A well hydraulics estimate of the inflow quantity was 18 to 47 MGD. This agreed reasonable well with the estimate of the available runoff. Deviation between the two could be due to the limited amount of data on heads on the well.

Behovet av dagvattenhantering har förändrats. Klimatförändringarna medför förändringar i nederbörden med oförutsägbara väder. Om det sedan kombineras med en högre exploateringsgrad kan det ge översvämningar och skadade byggnadsverk som följd. I Gävle kommun exploateras just nu Södra Hemlingby med en blandning av bostadstyper. Dessutom byggs en ny skola, vårdboende och förskola samt idrottshall i kommunens regi. Kraven för omhändertagandet av dagvatten är skärpt från de vanliga 10-årsregnet till det mer omfattande 20-årsregnet för lokalt omhändertagande. Recipienten i området, Hemlingbybäcken, är sedan tidigare överbelastat. Detta är ett examensarbete om dagvattenhanteringen med utgångspunkt i området Södra Hemlingby, med marken för samhällsnyttiga funktioner som underlag för det lokala omhändertagandet. Den valda lösningen, kassetter, ställs mot den traditionella stenkistan. Dessutom utreds vilken påverkan det högre kravet om projektering för 20-årsregn har för de projektet. Resultatet visade att kassettmagasinet är den lösning som uppnår flest krav. Ett kassettmagasin har ett större antal möjliga fördelar än magasin utformade med stenkista. Ett dimensionerande för högre årsregn motiveras med den pågående klimatförändringen. / The need to manage stormwater in urban areas, urban runoff, has changed. With a climate that continues to change, the weather and precipitation are becoming more unpredictable each year. When this is combined with even further urbanisation of our cities, urban flooding’s will be more frequent, with immense damage as aftermath. Södra Hemlingby is currently being exploited by Gävle kommun, with a mixture of accommodations. Furthermore, Gävle kommun will build a new school, gymnasium, retirement home and pre-school, all constructed in the municipal regime. By increasing the regulations regarding how to dimension the system designed to locally deal with the urban runoff, from a 10-year rain-plan to a more comprehensive 20-year rain-plan. Hemlingbybäcken, the local recipient in the area, is already at its maximum capacity. With the core of this thesis being urban runoff, Södra Hemlingby and its surrounding area planned to contain the social structure will be the area used as a foundation when estimating the local demand for processing the urban runoff. Furthermore, this thesis will also investigate how the increasing demand for a 20-year rain-plan will influence this project. The results indicated that the solution that best fulfils the requirements, and was within the of scope this thesis, was the kassettmagasin. When compared against a tried-and-tested method stenkista, the kassettmagasin proved to have more advantages. With the effect that comes with changing in climate and weather conditions, it is motivation enough to increase the demand to dimension for a 20-year rain-plan.

Urbanization alters land cover by increases in impervious areas, resulting in large increases in runoff, sediment, and nutrient loadings downstream. These changes cause flooding, eutrophication, and harmful algal blooms. Stormwater control measures (SCMs) are used to address these concerns and are designed based on inflow loads. Thus, estimating nutrient and sediment loads from developed watersheds is vitally important for meeting the impacts of urbanization. Today, stormwater events are characterized mainly by watershed models using little, if any, actual field monitoring data. The simple event mean concentration (EMC) wash-off approach by land use is a common practice used by practitioners for estimating loads. Pollutants accumulate on surfaces during dry periods, making EMC a function of antecedent dry period (ADP). An EMC results from wash-off of accumulated pollutants from catchment surfaces during runoff events. However, it assumes concentration is constant across events from a particular land use and several studies found little to no correlation between constituent concentrations in stormwater and ADP. Build-up/wash-off equations were developed to account for variation of concentrations between events; however, the required parameters are difficult to estimate. This study applied machine learning approaches with a national dataset along with monitoring and modeling studies at watershed scales to improve predictions of stormwater quantity and quality. First, we obtained stormwater quality data from the National Stormwater Quality Database (NSQD), which is the largest data repository of stormwater quality data in the U.S., and used Bayesian Network Structure Learner (BNSL), a machine learning approach, to discover which climatological or catchment characteristics most significantly affect stormwater quality. Second, we developed and applied Random Forest (RF), a data-driven method, to predict nutrients and sediment EMCs in urban runoff. Third, we applied the Storm Water Management Model (SWMM), a widely used urban watershed model, to an urban watershed and assessed the best fit estimates of SWMM parameters and hydrological response of the watershed during dry and wet hydroclimatic conditions. Last, we conducted a monitoring and modeling study at a catchment scale and assessed the role of land use on stormwater quantity and quality to optimize and investigate the build-up/wash-off parameters for multiple urban land uses for nutrients and sediment. The results presented in this dissertation can help stakeholders, urban planners, and SCM designers improve estimates of nutrients and sediment loads and thus achieve more effective treatment of stormwater, better attain water quality goals, and protect downstream water bodies. / Doctor of Philosophy / Urban development results in increased hardscapes (impervious surfaces), which increases runoff and subsequent pollution from nutrients and sediment carried off land surfaces. This negatively impairs the health of receiving streams, lakes, rivers, and estuaries. A variety of management practices are available for reducing these impacts. Practice size is based on the water quantity and quality it will receive. Thus, estimating the quantity of nutrients and sediment from developed areas is crucial to meet water quality goals. However, designs of stormwater management practices typically use historical data based on land use; rather than conducting new monitoring studies to determine actual pollution loads. Event mean concentration (EMC) is a common method used to estimate wash-off of pollutants from the land. Pollutants accumulate on surfaces during dry periods, making EMC a function of antecedent dry period (ADP) which is the time between storm events. An EMC results from wash-off of accumulated pollutants from urban areas during a storm event. However, EMC assumes pollutant concentration is constant across any storm event from a particular land use. Several studies found little to no correlation between nutrients and sediment concentrations in stormwater and ADP. Build-up/wash-off equations were developed to account for variability of concentrations between storm events; however, there are several parameters that are difficult to estimate. This study applied machine learning approaches to a national stormwater quality dataset and conducted monitoring and modeling studies at progressively smaller scales to improve the predictions of stormwater quantity and quality. First, we obtained stormwater quality data from the National Stormwater Quality Database (NSQD), which is the largest data repository of its type in the U.S., and used Bayesian Network Structure Learner (BNSL), a machine learning method, to discover which climatological or catchment characteristics most significantly affect stormwater quality. Second, we developed and applied Random Forest (RF), also a machine learning method, to predict nutrients and sediment EMCs in stormwater. Third, we applied the Storm Water Management Model (SWMM), which is the most widely used rainfall/runoff model, to an urban area and assessed the best fit estimates of SWMM parameters during dry and wet years. Last, we conducted a monitoring and modeling study at smaller scales and assessed the role of land use on stormwater quantity and quality and estimated build-up/wash-off parameters for multiple urban land uses for nutrients and sediment using optimization. The results presented in this dissertation can help stakeholders, urban planners, and stormwater practice designers improve estimates of the quantity of nutrients and sediment in stormwater, achieve more effective treatment of stormwater, attain water quality improvement goals, and protect the health of receiving streams and downstream water bodies.

The purpose of this research was to investigate the relationship between watershed land use and seasonal changes on THM-formation potential from the waters of four streams located in northern Virginia. Specific objectives were to observe the effect of impoundment on downstream THM precursor concentrations and to evaluate the molecular-size distributions of THM-precursors in stream waters as to the influence of seasonal changes, storm events, and watershed land use. Raw water samples were collected from October 1989 through May 1990 during baseflow and storm conditions. The samples were fractionated through 500, 1000, 5000, 10000, and 30000 dalton ultrafilters and were then chlorinated to determine the THM-formation potential based on the total organic concentration of the water fraction. From the data collected, it was shown that seasonal changes influenced the TOC and THM-precursor loadings in runoff from the watersheds. Fall runoff from Broad Run contributed the highest mass loading. Impoundment was seen to increase the amount of THM precursors downstream of Lake Manassas on Broad Run with the largest difference observed during the fall event. The more-rural watersheds draining into Broad Run contributed the most TOC and THM precursors during the fall runoff event, while the more-urban watersheds (Bull Run and Holmes Run) contributed more TOC and THM precursors in the winter and spring runoff. / Master of Science

The relationships between contaminant removal from impervious pavements and raindrop impact energy, cumulative kinetic energy of rainfall events, and rainwater fit were evaluated. A commercial urban area was chosen to perform simulated rainfall experiments. The runoff from these experiments was collected and analyzed for total suspended solids, volatile suspended solids, total Kjeldahl nitrogen, soluble Kjeldahl nitrogen, oxidized nitrogen, ammonia, ortho-phosphate, total phosphorus, soluble phosphorus, total lead and total zinc. Raindrop impact energy, rainfall intensity, rainfall duration, and rainwater pH were factors which were varied to examine their effect on contaminant wash-off phenomena. The present exponential decay theory of contaminant removal was verified and modified to incorporate the cumulative kinetic energy of rainfall events. An empirical model for contaminant removal was also developed. Data showed that both raindrop impact energy and cumulative storm energy had significant effects on contaminant removal. Contaminant wash-off was found to be independent of rainwater pH except for solids removal at low rain intensities. Additional results indicated that there is a "threshold impact energy" necessary before significant removal of contaminants associated with insoluble material can occur. The kinetic energy attributed to surface runoff overflow was found to be very important in the mechanisms responsible for contaminant removal at high rainfall intensities. / M.S.