Fu-hsiung Lai

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.

Costs of Urban Stormwater Control

This paper presents information on the cost of stormwater pollution control facilities in urban areas, including collection, control, and treatment systems. Information on prior cost studies of control technologies and cost estimating models used in these studies was collected, reviewed, and evaluated. The collection phase involved identifying, screening, and consolidating publications associated with capital costs of stormwater conveyance systems and control technologies. The resulting data were evaluated to develop a critical review of costs for urban stormwater control technologies, including identification of cost information gaps and research needs.

Framework Design for BMP Placement in Urban Watersheds

A number of stormwater control strategies, commonly known as best management practices (BMPs), are used to mitigate runoff volumes and associated nonpoint source pollution due to wet-weather flows (WWFs). BMP types include ponds, bioretention facilities, infiltration trenches, grass swales, filter strips, dry wells, and cisterns. Another control option is “low impact development” (LID) – or hydrologic source control – which strives to retain a site’s pre-development hydrologic regime by combining impervious area controls with small scale BMPs, reducing WWFs and the associated nonpoint source pollution and treatment needs. To assist stormwater management professionals in planning for BMP/LID implementation, the U.S. Environmental Protection Agency (EPA) initiated a research project in 2003 to develop a decision support system for selection and placement of BMP/LID at strategic locations in urban watersheds. The BMP/LID assessment tools based on sound science and engineering will help develop, evaluate, select, and place BMP options based on cost and effectiveness. The system is called the Integrated Stormwater Management Decision Support Framework (ISMDSF). The ISMDSF will provide a means for objective analysis of management alternatives among multiple interacting and competing factors. The desired outcome from the system application is a thorough, practical, and informative assessment considering the significant factors in urban watersheds. The ISMDSF will be applied to several diverse urban watersheds to evaluate and demonstrate its capability (Lai et al. 2003, Lai et al. 2004, Riverson et al. 2004). The initial phase of this research is expected to be completed in 2005 and will include a comprehensive design and a functional system with all pieces in place but not all functionalities. The subsequent phase will include enhanced geographical information system (GIS) capabilities for visualization of placement options, more powerful post-processors, expanded cost estimating functions, improved BMP simulation processes, and more importantly, a multiple objective optimization

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

SSOAP A USEPA Toolbox for SSO Analysis and Control Planning

The United States Environmental Protection Agency (USEPA) has identified a need to use proven methodologies to develop computer tools that help communities properly characterize rainfall-derived infiltration and inflow (RDII) into sanitary sewer systems and develop sanitary sewer overflow (SSO) control plans. To accomplish this goal, the USEPA entered into a cooperative research and development agreement (CRADA) in 2003 with a technology partner Camp Dresser & McKee (CDM) Inc. to develop a public-domain Sanitary Sewer Overflow Analysis and Planning (SSOAP) Toolbox. The CRADA also prepared a technical guide for analyzing RDII, performing capacity analyses of sanitary sewer systems, and developing SSO control plans using the toolbox. This paper describes the CRADA outcomes and individual tools in the SSOAP Toolbox to perform capacity analyses of sanitary sewer systems and develop SSO control plans.

Toxic Pollutants in Urban Wet-Weather Flows: An Overview of the Multi-Media Transport, Impacts, and Control Measures

This paper presents an overview of the transport of toxic pollutants through multiple media and drainage systems in the urban watershed during wet-weather periods. It includes the origin of the toxic substances; their transport via atmospheric deposition, overland washoff, and urban sewer systems; and, their impacts on both surface and ground waters. During dry-weather periods, incompletely combusted hydrocarbons from automobiles combine with atmospheric particulates from a host of other sources and deposit on urban streets and other urban surfaces. During a storm event, these solids, in addition to solids from industrial and commercial parking lots, material storage areas, and vehicular service stations are washed off by surface runoff and drained into either separate storm sewer or combined sewer systems. Field studies have identified that a major portion of hazardous waste priority pollutants including benzene, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, and heavy metals (e.g., arsenic, cadmium, chromium, copper, lead, mercury, and zinc) contained in urban stormwater runoff are in particulate form or sorbed onto particles. These stormwater particulate pollutants contribute significant toxicity to receiving waters. Mortality, epidermal lesions, or fin erosion can occur in fish and other aquatic life forms that are exposed to these toxic suspended solids and sediments. Methods for intercepting the cross-media transport of toxic constituents in the urban environment include best management practices to control surface runoff pollution; steeper sewer slopeage and improved pipe bottom shapes to maintain high velocity solids-carrying capacity during low-flow periods; and upstream sewer flushing and sediment trapping to reduce clogging and sediment in sewers.

Sewer-Sediment Control: Overview of an EPA Wet-Weather Flow (WWF) Research Program

This paper presents an historical overview of the sewer-sediment control projects conducted by the WWF Research Program of the U. S. Environmental Protection Agency (EPA). Research includes studies of the causes of sewer solids deposition and development/evaluation of control methods that can prevent sewer-sediment accumulation. Discussions focus on the relationship of wastewater characteristics to flow carrying velocity, abatement of solids deposition and solids resuspension in sewers, and sewerline-flushing systems for removal of sewer sediment.

Planning for SSO Control: Henrico County, VA -- Case Study

This paper illustrates how a state-of-the-art systemwide collection system modeling approach employed by the County of Henrico, Virginia enhanced the planning and design of its sanitary sewer overflow control facilities. The paper discusses the following planning components: (1) development of dry-weather wastewater flow projections using a geographical information system equivalent data of existing and projected land uses, existing and projected population density and distribution, existing base wastewater flows from water consumption records, and flow monitoring data from their supervisory control and data acquisition system; (2) prediction of wet-weather rainfall dependent infiltration/inflow using a predictive model with model parameters calibrated and verified with recorded wet-weather flow data; (3) analysis of the capacity of the existing sewer system under present and future conditions using the SWMM EXTRAN model; (4) analysis of the wastewater treatment facility to assess hydraulic and process capacity of unit processes and determine expansion requirements for treating increased flows; and (5) development of a capital improvement program for phased implementation of additional facilities (sewers, storage tanks, pump stations, force mains, and wastewater treatment plant expansion or process retrofitting) to meet the available projected capital investment budget and provide flexibility in the future for constructing improvements when they are needed. This paper also presents the steps that the County has taken to actually implement the capital improvement plan.

Collection System Modeling for Planning/Design of Sanitary Sewer Overflow (SSO) Control

The nations sanitary sewer infrastructure is aging with some sewers dating back over 100 years. There are more than 19,500 municipal sanitary sewer collection systems nationwide serving an estimated 149 million people and comprising about 500,000 sewer miles. Potential health and environmental risks associated with poor performance of many of these systems highlight the need to increase federal regulatory oversight of the management, operation, and maintenance of these systems. As a result, EPA is in the final stage of preparing and issuing a SSO Rule that will add control of SSO to the NPDES permit requirements. This paper provides a preview of the Rule and describes the advantages of employing a collection system modeling approach for capacity assurance of various components of a collection system and development of SSO mitigation plan. A case study at Henrico County, VA is provided to illustrate the application of a collection system modeling approach to plan for sanitary sewer system improvements.