This paper presents the results of an experimental study aimed at determining the impact of porous asphalt on the quality of stormwater runoff on highways with a curb and gutter drainage system. A porous overlay, also known as permeable friction course (PFC), is a layer of porous asphalt applied to the top of conventional asphalt highways at a thickness of 50 mm to improve safety and water quality and reduce noise. The quality of highway stormwater runoff was monitored before and after the installation of PFC on an eight-lane divided highway in the Austin, Texas area for 15 months. Observed concentrations of total suspended solids from PFC are more than an 80% lower than from the conventional pavement. Concentration reductions are also observed for nitrate/nitrite and total amounts of phosphorus, copper, lead, and zinc. The data shows that the results with curb and gutter are consistent with past results where runoff sheet flowed onto vegetated shoulders. / text

Thesis (Ph. D.) -- University of Maryland, College Park, 2007. / Thesis research directed by: Civil Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Stroubles Creek is registered on Virginiaâ s 303(d) list of impaired waters for both benthic and fecal coliform impairments. The upper reach of the creekâ s watershed drains into two ponds on the Virginia Tech campus. The area draining to the ponds, approximately 715 acres, encompasses most of the Town of Blacksburg and the Virginia Tech campus. Below the ponds, the creekâ s watershed is primarily forested and agricultural, with some areas of residential development. In order to improve water quality downstream, the two ponds will be converted to a water quality facility by redirecting all flow from the northern branch of Stroubles Creek into the upper, smaller pond, which then flows into the larger pond below. With flow into the upper pond increasing dramatically, the dam between the two ponds and associated overflow structures were evaluated and redesigned to protect the dam from overtopping and possible washout. In addition, concrete weirs were designed and will be constructed on both branches of Stroubles Creek above the ponds for future installation of flow and water quality monitoring equipment. Above the ponds, the banks along both branches of the creek have become severely eroded. Interlocking concrete block armoring was designed for the stream banks to reduce erosion and protect the trees growing along the creek. This project was jointly funded by Virginia Tech and a grant from the Virginia Department of Conservation and Recreation Water Quality Improvement Fund. Construction will be performed by the Capital Design department of Virginia Tech. / Master of Science

With a growing concern for the environment and increasing urbanization of rural areas, understanding the characteristics of urban non-point source pollution has become a focus for water quality investigators. Once thought to be a small contributor to the pollution problem, urban non-point sources are now responsible for transporting over 50% of all pollutants into natural waterways. Assessing non-point source pollution is the key to future water quality improvements in natural receiving waters. The purpose of this research was to investigate the water quality of an urbanized watershed, analyze current prediction methods and to investigate the effectiveness of an extended dry detention basin as a pollutant removal management practice on a 21.68-acre urban watershed on the Virginia Tech Campus. This research included extensive stormwater monitoring and sampling to characterize the runoff and water quality from an urban watershed. The resulting analysis included comparing well-known desktop prediction methods with pollutant removal rates using an extended dry detention basin and comparison with different literature values. Finally, the study team calibrated the PSRM-QUAL model for watershed prediction of non-point source runoff and pollution. The results of the stormwater monitoring process show that water quality prediction methods are not very successful on a storm by storm basis, but can be fairly accurate over longer periods of time with little or no storm water quality sampling. The extended dry detention basin is a simple yet effective management practice for the removal of sediments and sediment bound pollutants. / Master of Science

One of the many issues communities will face when trying to protect their local watershed is the lack of background their policy makers have in environmental protection and watershed health. The purpose of this study is to test a range of on-site stormwater management policies against a selection of new development projects from a specific small city of the United States in order to determine what combination of policies works best in a particular urban environment. Three policies were selected to test the range of stormwater approaches being used in the United States. These policies were then measured in a spreadsheet analysis against three years’ worth of new development from the city of Starkville, Mississippi. The outcomes of this research can provide communities and municipalities with a tool to help them determine which combination of application trigger and detention requirement for on-site stormwater management will best serve their watershed needs.

Proper stormwater management acknowledges both water quantity and water quality. Historically, stormwater quantity and quality have been separately considered; runoff was routed as quickly as possible into the nearest body of water. Although this alleviates potential flooding concerns, water quality is often compromised. Common stormwater quality problems include gross pollutants, sediment, nutrients, and heavy metals. The chronic elevated presence of these pollutants is detrimental to the environment. As a result, the government has passed legislature to protect waterways. The passage of the National Pollution Discharge Elimination System (NPDES) permit requires that municipalities implement stormwater treatment techniques, known as Best Management Practices (BMPs). Unfortunately, the NPDES document suggests treatment to the maximum extent possible, a vague description at best. This thesis reports a two-part study that endeavors to evaluate three of these proprietary treatment units manufactured by Stormceptor, BaySaver Separation Systems, and Continuous Deflective Separator (CDS) Technologies, Inc. to determine their performances. Each manufacturer produces a separator system that physically removes contaminants through the use of hydrodynamic flow principles. Phase I of the study focuses on monitoring two Stormceptor units and a CDS device in field conditions, while the second phase of the study evaluates each of the three treatment systems under laboratory conditions. The data analyses from the field study show the importance of proper maintenance. Storm events monitored after sump material removal showed great improvement over storm events occurring some time after the sump material removal. Furthermore, the treatment devices show a greater ability to remove pollutants from smaller storm events when compared with larger storm events. It is suggested that large storms cause scour of sediment previously trapped within the sump of the devices. An increase in the total suspended solid and nutrient concentrations, which were higher than the influent concentrations, was observed in both the field and laboratory studies. This could be explained by the fact that organics trapped by the treatment system decompose over time, therefore producing nutrient-rich water in the sump of the devices with higher concentration than the subsequent storm events. Some results are close to the minimum detection limit of the parameters being tested and small differences between influent and effluent load exaggerate the percent load differences. Consequently, there is little statistical significance between influent and effluent data, thus the data are summarized utilizing two methods. The methods include graphical representation of concentration and percent load difference, a method that normalized storms based on event size. In addition, a mass balance of gross litter was performed during the laboratory study.

The potential real-time control (RTC) has to improve the performance of existing stormwater management systems is a topic of increasing interest as hydraulic and hydrologic modeling capabilities proliferate. The benefits of incorporating precipitation forecast data into a RTC algorithm to allow for prediction-based control of an urban watershed is explored using an EPA SWMM 5.1 watershed model. One reactive and two predictive RTC algorithms are simulated in various configurations across seven dry detention ponds located in the 162 hectare urbanized watershed. The hydraulic benefits they provide at the site and watershed outlet in regards to peak flow and the flow duration curve are compared to conventional, static control. The ponds retrofit with the novel predictive RTC algorithm had lower peak flows during 24-hour design storms more consistently than when retrofit with reactive RTC. The duration of erosive flows at the site level was decreased by the novel predictive RTC in most cases. Improvements at the watershed outlet depended on where RTC was applied as hydrograph compounding was observed during some RTC implementations. / Master of Science / The consequences of watershed urbanization on nearby waterways has become a more relevant concern as urbanization increases and climate change continues to develop. Conventional stormwater management practices are employed to control peak flows from urbanized drainage areas for certain design storm criteria. Real-time control (RTC) technology has the potential to enable existing stormwater facilities to improve their performance during storm events different from their design conditions. This study compares the performance of several reactive and predictive rule-based RTC algorithms simulated as retrofits on seven dry detention ponds in a 162 hectare urbanized watershed. The results indicate that RTC algorithms that use rainfall forecast data for predictive decision making have the most potential to reduce stream erosion when applied appropriately throughout the watershed.

Residential infill development and the associated increases in impervious cover and stormwater runoff have the potential to overwhelm aging infrastructure causing erosion, flooding, and ecological degradation of waterways. The lack of greenfield sites available for new development around urban centers coupled with a desire for maintaining a traditional neighborhood aesthetic drives residential infill and replacement of existing smaller homes by significantly larger structures, minimizing open space available for stormwater mitigation. An analysis of residential infill development trends in Fairfax County was performed to characterize the effects of intensified development. Development patterns were identified and assessed using digitized impervious cover data extracted from aerial imagery of the study area for six selected years from 2002 to 2015. The average annual increase in percent impervious area was computed to be 0.3%. Redevelopment was found to be mainly occurring in areas zoned as lower-density residential. The spatial distribution of redevelopment showed trends of clustered increases as opposed to isolated events. The hydrologic analysis performed revealed that from 2002 to 2015, there was an 8,930 m3 (7.2 acre-ft) increase in stormwater runoff volume, 38% of which is contributed to by runoff generated from development that is considered exempted from regulation in Fairfax County. Additionally, there was a 28 kg/year (62 lb/year) increase in total phosphorus loads attributable to the change in impervious cover due to residential development throughout the study area. The results of this study provide a quantitative basis for municipalities to amend policies regulating residential development and its associated stormwater management. / Master of Science

No description available.

<p>An approach to incorporate the effect of flood routing through a channel reach for use with the analytical probabilistic stormwater models (APSWM) was developed earlier in 2005. That earlier approach relied on adding the Muskingum K value of the channel reach into the catchment time of concentration and treating the whole drainage area including the channel reach as a lumped catchment. This is insufficient since other factors such as the X value in the Muskingum routing method also affects the routing results. In this study, a new approach to incorporate the routing effect of channel reaches in APSWM was developed where not only the K value but also the X value of a channel reach are considered. A number of continuous simulations were conducted to verify the proposed approach. It was demonstrated that the proposed approach performs better than the earlier one.</p> / Thesis / Master of Applied Science (MASc)