In 1999, Phase II of the National Pollutant Discharge Elimination System engaged operators of small Municipal Separate Storm Sewer Systems (MS4) in the control of runoff from urban areas.  The complex task of urban runoff mitigation has been investigated for several decades, resulting in a large variety of available computing and measurement tools for urban stormwater management.  Unfortunately, these tools may not be available to the MS4 operator in a format that is both concise, and directly applicable.  To address this need, this thesis recommends stormwater model creation and refinement strategies for Phase II MS4s using GIS and Python scripting.  Further recommendations on using a popular discharge measurement technique for model calibration are provided.  This workflow is then demonstrated in a watershed in Blacksburg, Virginia, where a unique MS4 permitting partnership allowed the development of these tools.  Finally, further improvements to the workflow are suggested along with ideas for additional research for stormwater management in Phase II MS4s. / Master of Science

This thesis project monitors the quantity and quality of stormwater entering and leaving a bioretention system in Coralville, Iowa. Bioretention is among many engineered solutions designed to provide treatment for runoff that might otherwise be drained directly to a body of water. Increased quantities of stormwater can impact stream morphology, degrade aesthetics, increase flood frequency, peak flow, and peak duration; as well as increased sedimentation and sediment transport. Decreases in water quality can impair fish or other aquatic populations, and increase the treatment requirements for downstream intakes. The number of communities, presently 47, affected by stormwater control ordinances increases as the Environmental Protection Agency continues to require smaller Municipal Storm Sewer Systems to adhere to National Pollutant Discharge Elimination System permits. The City of Coralville is setting an example by using infiltration practices to treat runoff from a 4-lane divided thoroughfare. Preliminary monitoring shows that the system in Coralville provides an average reduction in effluent temperature g of 3.7°C, an average reduction in peak flow of 2 cfs, and an average peak delay of 45 minutes. The project provides infiltrative treatment for the water quality volume and the empirical curve number for the project is 77.4. The urban runoff to the project is within literature values and the pollutant concentrations in the project effluent are below legal limits.

In March 2003, many communities in Mississippi fell under National Pollutant Discharge Elimination System (NPDES) regulations and were required to develop Stormwater Pollution Prevention Plans (SWPPPs). This study surveyed those in charge of SWPPPs in Mississippi’s regulated communities to determine the knowledge, efforts, and associated expenses, of complying with Stormwater Phase II regulations as well as what attempts regulated communities made to include urban forestry in their SWPPPs. While results indicated that all respondents were compliant with Stormwater Phase II regulations, regulated communities can improve efforts in several areas to best mitigate stormwater runoff pollution (e.g., public education and urban forestry). Findings will be useful when presented to current and, soon to be, regulated communities in an educational and outreach effort to increase their knowledge levels, reduce incurred costs, increase the effectiveness of their SWPPP, and enhance their ability to utilize urban and community forests as a stormwater mitigation tool.

Municipal separate storm sewer system (MS4) permittees face costly obligations to reduce pollutant loadings needed to achieve waste load allocations (WLAs) and meet total maximum daily loads (TMDLs). Street sweeping is potentially an effective BMP since streets exist throughout urban watersheds, often are directly connected to the storm sewer, and are found to contain an abundance of contaminants. Although pollutant removal from street sweeping has been evaluated for decades, an understanding of the impact on water quality in receiving streams is elusive. Due to numerous variables, the large number of samples necessary to measure impact in receiving streams may never be obtained. In response, modeled pollutant removal efficiencies based on frequency of sweeping have been recommended to the Chesapeake Bay Program, but these results are suspect. Alternatively, the amount of swept material has emerged as a method to quantify reductions. A sampling study was conducted to measure pollutants in swept material. The study identified the fraction of material susceptible to transport in runoff based on timing of sweeping in relation to runoff events. Based on observed pollutant concentration associations with particle size, the study results in estimates of pollutant concentrations for the fraction of material susceptible to downstream transport, dependent on duration since the last rainfall and type of surface swept, whether the area is a streets or a parking lot. Pollutant loadings and required reductions to achieve the Chesapeake Bay WLAs for various land use sample areas are computed for an average year. Modeled removal efficiencies and results from the sampling study were employed to assess impacts from street sweeping. Modeled efficiencies predict significantly lower impact than measurements of pollutants susceptible to runoff in swept material. Modeled loadings are inconsistent with measurements of swept materials and the rigorous sweeping frequency required for modeled removal efficiency credit appears to be unnecessary. / Doctor of Philosophy / Many localities, state agencies and other public entities that own storm sewer systems are increasingly required to reduce pollutants discharged from their systems to surface waters as a result of programs stemming from the Clean Water Act. Traditional stormwater management practices, such as retention ponds, appear limited towards providing the total pollutant reductions necessary due to physical constraints, opportunity and cost. Street sweeping is potentially an effective alternative practice since streets exist throughout urban watersheds, often are directly connected to the storm sewer, are found to contain an abundance of contaminants and can be cost effective. Although pollutant removal from street sweeping has been evaluated for decades, an understanding of the pollutants removed from stormwater is elusive. Past studies suggest the large number of samples necessary to measure impact from sweeping in receiving streams may never be obtained. In response, pollutant removal estimates have been made using computer models, but modeled results are suspect since they cannot be calibrated. Alternatively, a measure of swept material has emerged as a method to quantify pollutant reductions. A sampling study was conducted to measure pollutants in swept material. Results identify the fraction of swept material washed from the swept surface dependent on timing of sweeping in relation to the duration since the last rainfall. Based on observed pollutant concentration associations with particle size, the study results in estimates of concentrations for the fraction of material susceptible to downstream transport, dependent on duration since the last rainfall and type of surface swept, whether the area is a streets or a parking lot. Application of the results are compared to modeled removal efficiencies towards achieving regulatory compliance within various land use sample areas. Modeled efficiencies predict significantly lower impact than measurements of pollutants susceptible to runoff in swept material. Rigorous sweeping frequency required for modeled removal efficiency credit appears to be unnecessary.

This dissertation argues that stormwater management is fragmented both at that vertical fragmentation (at the level of intergovernmental relations) and horizontal fragmentation (within the level of governments). The first essay focuses on the institutional arrangements used by states to implement stormwater management policies. Building on the race to the bottom literature, I examine the impact of the institutional arrangement centralization on state water quality in California, Texas, Virginia, and Minnesota. A five-year (2013-2018) permitting cycle was used to analyze five dimensions: formalism, coercion, education, prioritization, and accommodation.There is an inverse relationship between the quality of stormwater and the degree of centralization in the institutional arrangements adopted by state governments to implement their stormwater management policies. The second essay focuses on a local government's decision to join an inter-local agreement to comply with federal/state stormwater management policies. Building on the transaction cost framework, the study used a cross-sectional design to analyze a case study. The case study consists of 119 cities subjected to stormwater regulation requirements in northern Texas during 2017. The dependent variable is the membership of the regional inter-local agreement, and the independent variables are the number of neighboring cities and population density. Community wealth, public works spending, stormwater fees, government type, and the percent of the population over 65 were used as control variables. Logistic regression was used for data analysis. This study concludes that the increase in the number of neighboring regulated local governments is associated with an increase in the likelihood of a decision by the regulated local government to join an interlocal agreement (ILA), as well as finding that an increase in the population density is associated with an increase in the likelihood of a decision by the regulated local government to join the ILA. In addition, the study found that the type of government also affects a decision to enter into a cooperative relationship to meet the regulative burdens associated with implementing the stormwater management policies imposed by state/federal governments. The results found in this dissertation contribute to bridging the gap in our knowledge on the impact of the institutional framework adopted by the states to implement environmental policy through empirically evaluating the effect of institutional arrangements (as represented in the States general MS4 permits) on the policy output (reducing the level of stormwater pollution).