Jenny Zhen

A watershed-scale design optimization model for stormwater best management practices

U.S. Environmental Protection Agency developed a decision-support system, System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN), to evaluate alternative plans for stormwater quality management and flow abatement techniques in urban and developing areas. SUSTAIN provides a public domain tool capable of evaluating the optimal location, type, and cost of stormwater best management practices (BMPs) needed to meet water quality and quantity goals. It is a tool designed to provide critically needed support to watershed practitioners in evaluating stormwater management options based on effectiveness and cost to meet their existing program needs. SUSTAIN is intended for users who have a fundamental understanding of watershed and BMP modeling processes. How SUSTAIN is setup described here using a case study, conducted by actual data from an existing urban watershed. The developed SUSTAIN model was calibrated by observed rainfall and flow data, representing the existing conditions. The SUSTAIN model developed two BMP cost-effectiveness curves for flow volume and pollutant load reductions. A sensitivity analysis was also conducted by varying important BMP implementation specifications.

Development of a multi-criteria index ranking system for urban runoff best management practices (BMPs) selection

Low impact development best management practices (LID-BMPs) are considered to be cost-effective measures for mitigating the water quantity and quality impact of urban runoff. Currently, there are many types of LID-BMPs, and each type has its own intrinsic technical and/or economical characteristics and limitations for implementation. The selection of the most appropriate BMP type(s) for a specific installation site is therefore a very important planning step. In the present study, a multi-criteria selection index system (MCIS) for LID-BMP planning was developed. The selection indexes include 12 first-level indices and 26 second-level indices which reflect the specific installation site characteristics pertaining to site suitability, runoff control performance, and economics of implementation. A mechanism for ranking the BMPs was devised. First, each individual second-level index was assigned a numeric value that was based on site characteristics and information on LID-BMPs. The quantified indices were normalized and then integrated to obtain the score for each of the first-level index. The final evaluation scores of each LID-BMP were then calculated based on the scores for the first-level indices. Finally, the appropriate BMP types for a specific installation site were determined according to the rank of the final evaluation scores. In order to facilitate the application of the MCIS BMP ranking system, the computational process has been coded into a software program, BMPSELEC. A case study demonstrating the MCIS methodology, using an LID-BMP implementation planning at a college campus in Foshan, Guangdong Province, is presented.

BMP Analysis System for Watershed-Based Stormwater Management

Best Management Practices (BMPs) are measures for mitigating nonpoint source (NPS) pollution caused mainly by stormwater runoff. Established urban and newly developing areas must develop cost effective means for restoring or minimizing impacts, and planning future growth. Prince Georges County in Maryland, USA, a fast-growing region in the Washington, DC metropolitan area, has developed a number of tools to support analysis and decision making for stormwater management planning and design at the watershed level. These tools support watershed analysis, innovative BMPs, and optimization. Application of these tools can help achieve environmental goals and lead to significant cost savings. This project includes software development that utilizes GIS information and technology, integrates BMP processes simulation models, and applies system optimization techniques for BMP planning and selection. The system employs the ESRI ArcGIS© as the platform, and provides GIS-based visualization and support for developing networks including sequences of land uses, BMPs, and stream reaches. The system also provides interfaces for BMP placement, BMP attribute data input, and decision optimization management. The system includes a stand-alone BMP simulation and evaluation module, which complements both research and regulatory nonpoint source control assessment efforts, and allows flexibility in the examining various BMP design alternatives. Process based simulation of BMPs provides a technique that is sensitive to local climate and rainfall patterns. The system incorporates a meta-heuristic optimization technique to find the most cost-effective BMP placement and implementation plan given a control target, or a fixed cost. A case study is presented to demonstrate the application of the Prince Georges County system. The case study involves a highly urbanized area in the Anacostia River (a tributary to Potomac River) watershed southeast of Washington, DC. An innovative system of management practices is proposed to minimize runoff, improve water quality, and provide water reuse opportunities. Proposed management techniques include bioretention, green roof, and rooftop runoff collection (rain barrel) systems. The modeling system was used to identify the most cost-effective combinations of management practices to help minimize frequency and size of runoff events and resulting combined sewer overflows to the Anacostia River.

Design of a Decision Support System for Selection and Placement of BMPs in Urban Watersheds

The U.S. Environmental Protection Agency (USEPA) has funded the development of a decision support system for selection a nd placement of best management practices (BMPs) at strategic locations in urban watersheds. The primary objective of the system is to provide stormwater management professionals with a BMP assessment tool based on sound science and engineering that helps develop, evaluate, select and place BMP options based on cost and effectiveness. The system is called the Integrated Stormwater Management Decision Support Framework (ISMDSF) and is being designed through a systematic review of modeling needs, technical requirements, current and emerging data management technology, and available watershed and BMP models. The ISMDSF will be applied to a real urban watershed to evaluate its ability. There are four major design aspects for the ISMDSF development. First, t he system provides a robust computer platform for BMP selection, sizing, and placement in the context of several integrated watershed factors and influences. Second, it is applicable to mixed land use urban watersheds, and can perform watershed simulation based on watershed size, scale, anthropogenic, and natural characteristics. Third, it incorporates hydrologic/hydraulic and water quality modeling, integrating surface runoff and direct discharges to surface water bodies, based on relevant data collection. Finally, it will have the capability to objectively evaluate multiple solution alternatives based on cost and the desired water -quality objectives. Programs that would benefit from the application of the ISMDSF include Municipal Separate Storm Sewer System (MS4) permits under the NPDES Stormwater Program (Phase I and II), Total Maximum Daily Load (TMDL) evaluations, and source-water protection. The ISMDSF will provide a means for objective analysis of management alternatives among multiple interacting and competing factors. The desired outcome

BMP Model for Low-Impact Development

Low-impact development (LID) techniques can be used for controlling stormwater impacts from new development and redevelopment / urban retrofit. Prince Georges County has developed a Best Management Practices (BMPs) evaluation module to assist in assessing the effectiveness of LID technologies. This module uses process-based algorithms to simulate BMP function and removal efficiency and accepts flow and water quality time series either from observation or generated by runoff models such as the Hydrologic Simulation Program, FORTRAN (HSPF) as input data. Process-bases algorithms include weir and orifice control structures, storm swale characteristics, flow and pollutant transport, flow routing and networking, infiltration and saturation, evapotranspiration, and a general loss/decay representation for a pollutant. The module offers the user the flexibility to design retention style or open-channel BMPs, define flow routing through a BMP network, and compares BMP controls against pre-development conditions. BMP effectiveness can be evaluated and estimated over a wide range of storm conditions, site designs, and flow routing configuration approaches. The simulation processes of the model have been validated using available monitoring data and literature values. The BMP Module has been applied to several real land development projects using actual long-term meteorological data recorded at Washington National Airport. These development projects were designed based on the State stormwater management requirements and regulations. The simulation results indicate that LID can actually minimize water quantity and quality impacts of the developments. For all cases, the results indicate that post-development condition with LID BMPs exceeds existing condition (assumed to be completely forested) in terms of hydrologic attenuation benefit and pollutant control benefit. This paper provides an overview of the model and demonstrate the simulation results. The results also raise an interesting question: Is using the Natural Resources Conservation Services (NRCS) Rainfall Type II Distribution appropriate for the design of stormwater BMPs? With the U. S. Environmental Protection Agencys support, the model is currently being enhanced to include the following: linkage to the CSO model, development of an optimization module, and integrating with GIS platforms.

BMP Decision Support System for Evaluating Watershed-Based Stormwater Management Alternatives

The proper selection and placement of Best Management Practices (BMPs) is a critical part of the stormwater planning effort. Established urban and newly developing areas must establish cost effective means for restoring existing sites, minimizing impacts to new sites, and provide general site planning for future growth. Prince Georges County, Maryland in the Washington D.C. metropolitan area has developed a BMP analysis system to support analysis and decision making for stormwater management planning and design at the watershed level. This system supports watershed hydrologic and water quality analysis, simulation of various innovative BMPs, and selection/placement optimization of suitable BMPs that will achieve the goals, defined by a user. This system helps planners determine which alternatives will yield the greatest benefit by automatically assessing several key site-specific factors. Housed in the ESRI ArcGIS environment, the system provides visualization and GIS processing support for developing networks including sequences of land uses, BMPs, and stream reaches. ArcGIS also serves as an interface for BMP placement, BMP attribute data input, and as a platform for managing the decision optimization component. The system then launches a stand-alone BMP simulation and evaluation module. Since the module is a process based simulation model for BMPs, it provides a technique that is sensitive to local climate and rainfall patterns as well as BMP size, design, and relative placement on the site. The system incorporates a meta-heuristic optimization technique to find the most cost-effective BMP placement and implementation plan that best satisfies a controlled target and fits within a fixed cost budget. A case study application is presented to demonstrate the application of the system. The case study involves a highly urbanized area in the Anacostia River watershed, located within the boundaries of Maryland and the District of Columbia. Several BMPs such as bioretention, green roof, porous paving and rain barrels are proposed, which minimize runoff, improve water quality, and provide water reuse opportunities. The modeling system is used to identify and evaluate various alternatives to determine the most cost-effective types and combinations of BMPs that best minimize the frequency and size of runoff events thereby also reducing the magnitude and frequency of combined sewer overflows to the Anacostia River.

Economic Consideration in Water Quality Improvement Practices under Extreme Flow Conditions: Water Quality Design Storm

Various Total Maximum Daily Loads (TMDLs) developed for Los Angeles County watersheds require comprehensive implementation plans to strategize specific best management practices (BMPs) to meet required pollutant load reductions during storm events. Ongoing efforts for assessment of BMPs in Los Angeles County have repeatedly indicated a need to identify a water quality design storm for both regulatory and BMP design purposes. The Los Angeles County Flood Control Districts Watershed Management Modeling System (WMMS) has served as the enhanced platform for the design storm development approach. The analysis is dependent on three key factors: (1) storm sizes and associated treatment volume, (2) BMP costs, and (3) achievement of water quality standards. Finally, this paper proposes threshold storm sizes that can be treated for best pollutant reduction benefits while considering economic impact. The results are also presented as BMP sizing recommendations for TMDL attainment purpose. Ultimate analyses of costs and benefits can potentially lead to identification of the maximum extent practicable (MEP) target with which BMPs can be implemented to achieve water quality standards within receiving waters.

Packaging Management Alternatives for the Lake Tahoe Clarity TMDL: Application of a Meta-Heuristic Optimization Technique for Developing a Recommended Basin-Wide Management Strategy

Lake Tahoe is a designated Outstanding National Resource Waterbody. However, lake clarity has dropped at a rate of 9 inches per year since the late 1960s, with ultra-fine sediment and nutrient driven algae production as the primary stressors. The primary sources have been identified as urban runoff and forest upland erosion, atmospheric deposition, and stream channel erosion. With more than

Integrating On-Site Water Management Practices: A Field Study in Prince George's County, Maryland

1.5 billion estimated as the cost to restore lake clarity, a premium has been placed on developing informative decision support analyses. Following an expert-led effort to characterize potential pollutant reduction opportunities and associated cost information for the primary sources identified, a meta-heuristic optimization technique was applied to evaluate the costs-benefits and selection trade-offs among controls associated with the various pollutant sources. This paper highlights the methods and results that were applied to assist stakeholder decision making for an integrated water quality management strategy.

BMP decision support system for evaluating stormwater management alternatives

Decentralized and integrated stormwater management is becoming an efficient alternative to more conventional centralized structural Best Management Practices (BMPs). Decentralized management techniques, targeted to provide infiltration and minimize runoff closer to the sources, not only meet the stormwater control targets but also maintain the natural ecosystem integrity. On the other hand, conservation and reuse of rainwater and grey water are also emerging as environmentally sensitive green architectural techniques. Although both stormwater management and green architecture techniques have similarities, the disciplines have had limited interaction in practice. This study takes a holistic approach to site-level water management by examining both in-home and on-site water management concurrently. An integrated assessment of site-scale water balance provides a quantitative assessment of the benefits of a comprehensive approach that results in virtually no off-site runoff. The analysis was performed on a demonstration site location in Bowie, Maryland, that is representative of single family home. A comprehensive site characterization and evaluation of water uses were performed. The site characterization includes a review of site information (e.g., soils, land use, topography, percolation test, and septic system history) and a field exploration including soil borings, infiltrometers, and chemical sampling of rooftop runoff. Water use profiles for the site potable water, grey water, wastewater, rooftop runoff, and stormwater were evaluated to understand the opportunities and alternatives for integrated stormwater management. A number of alternative scenarios were screened through technical, economical, and social feasibilities and potential alternatives were recommended. The study also evaluated and recommended innovative alternatives for designing the site landscaping for cleansing runoff and conserving water through stormwater recycling, and on-site wastewater treatment (septic) system that integrates opportunities to efficiently utilize water at a site scale.