Stormwater Best Management Practices in an Ultra-Urban Setting: Selection and Monitoring

1.    Introduction and Purpose

Best management practices (BMPs) are used to mitigate the effects of highways and roads on local conditions, in terms of both water quantity and water quality effects. BMPs are used to reduce peak flows, to reduce runoff volumes, and to reduce the magnitude and concentrations of constituents in runoff. Numerous studies have been done on the effectiveness of BMPs, although past studies have emphasized more traditional BMPs such as wet and dry ponds and vegetative practices. A new, emerging area of BMPs includes technologies for highly urbanized, highly impervious ("ultra-urban") areas. Many of these practices use existing stormwater and wastewater technologies, modifying them to fit into the ultra-urban environment.

The purpose of this document is to provide a planning-level review of the applicability and use of new and more traditional BMPs in ultra-urban areas. This report is the result of extensive research to identify and document BMP practices in ultra-urban areas. The term "ultra-urban" has been used to describe metropolitan areas of the country where space for stormwater BMP implementation is limited (Bell, 1996). The goal of ultra-urban technology is to provide cost-effective, low-maintenance solutions to stormwater management problems in the ultra-urban environment.

This document is not intended to be a design manual. Other recent manuals by the Federal Highway Administration (FHWA) provide design guidance for more traditional BMPs, while design specifications for new, commercially available BMPs can be obtained from their manufacturers. This report supplements the other recent FHWA manuals, which are described below, by expanding and presenting additional data, design criteria, and monitoring study results on BMPs implemented in ultra-urban areas. Evaluation and Management of Highway Runoff Water Quality (Young et al., 1996) was developed to support highway practitioners by synthesizing the results of past documentation and research on highway stormwater runoff into a unified user's manual on water quality impact assessment and mitigation. Urban Drainage Design Manual Hydraulic Engineering Circular 22 (Brown et al., 1996) was developed to provide a comprehensive and practical guide for the design of storm drainage systems associated with transportation facilities. Retention, Detention, and Overland Flow for Pollutant Removal from Highway Stormwater Runoff; Volume I: Research Report (Dorman et al., 1996a) and Volume II: Design Guidelines (Dorman et al., 1996b) were developed to provide design guidelines and specifications for measures to reduce or eliminate the impacts of highway runoff on surface waters.

1.1    Background

The water quality impact of runoff from highways and developed land is an environmental concern that is addressed by both state and Federal Department of Transportation (DOT) personnel tasked with stormwater management responsibilities. A number of current regulatory requirements, at the Federal, state and local levels, set the framework for stormwater management (Young et al., 1996). The box below lists some of the Federal programs which, along with state and local regulatory requirements, need to be incorporated into stormwater management planning considerations. A brief discussion of selected relevant programs is presented below.

The National Environmental Policy Act (NEPA) establishes judicially enforceable obligations that require all Federal agencies to identify the environmental impacts of their planned activities. The NEPA legislation and its requirements provide the framework under which environmental impacts of all substantial Federal projects are evaluated and have been the starting point from which many other environmental regulations are applied and enforced. Any major effort that involves Federal funding, oversight, or permits, such as highway operations and projects, is subject to the NEPA process to ensure environmental concerns are considered before implementation.

Regulatory Framework

• National Environmental Policy Act (NEPA)
• Clean Water Act: National Pollutant Discharge Elimination System (NPDES)
• Clean Water Act: Nonpoint Source Pollution Control Program (Section 319)
• Coastal Zone Act Reauthorization Amendments (CZARA)
• State regulatory requirements
• Local regulatory requirements

The Clean Water Act contains the primary mechanism for protecting and improving water quality. The purpose of the Clean Water Act is "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters" by declaring unlawful the unregulated discharge of pollutants into all waters of the United States. The Act makes the states and the U.S. Environmental Protection Agency (EPA) jointly responsible for identifying and regulating both point sources and nonpoint sources of pollution. The Act allows for both environmental quality-based approaches (water quality standards) and technology-based approaches (treatment processes and BMPs) to water quality control. Water quality management planning is focused on priority water quality issues in geographic areas. A number of relevant programs operate under the Clean Water Act, including Water Quality Certifications (section 401), the National Pollutant Discharge Elimination System (NPDES) (Section 402), and the Nonpoint Source Pollution Control Program (section 319).

The purpose of section 401 of the Clean Water Act is to ensure that federally permitted activities comply with the Act and appropriate state laws. Any applicant for a Federal permit for an activity that could result in a discharge of a pollutant to a state's waters is required to obtain certification from the state where the activity will occur. The state certifies that the materials or pollutants discharged comply with the effluent limitation, water quality standards, and other applicable state laws.

Amended section 402 of the Clean Water Act authorizes the NPDES program, under which discharge permits are granted by EPA or by states with EPA-approved programs. The NPDES permit program regulates any discharges by point sources, including stormwater discharges (except for agricultural stormwater runoff and return flows from irrigated agriculture) from municipalities serving a population of 100,000 or more. The overall approach to controlling stormwater runoff from local roads and highways is through stormwater management programs developed by municipalities. Many state DOTs participated in the NPDES permitting process where they were designated as permittees by EPA or the states.

In 1987, Congress amended the Clean Water Act to focus greater national efforts on nonpoint sources. Congress enacted section 319, which established a national program to control nonpoint sources of water pollution. Under section 319, states address nonpoint pollution by assessing nonpoint source pollution problems and causes within the state and developing and implementing management programs to control nonpoint source pollutants. The management programs include BMPs for different categories of sources, a schedule of implementation milestones, and appropriate regulatory measures. Section 319 authorizes EPA to issue grants to states to assist them in implementing these management programs.

Congress enacted the Coastal Zone Act Reauthorization Amendments of 1990 (CZARA) to address several concerns, one of which was the impact of nonpoint source pollution on coastal waters. To participate in the CZARA program, each coastal state must develop a Coastal Nonpoint Pollution Control Program for implementing management measures for nonpoint source pollution to restore and protect coastal waters, working in close conjunction with other state and local authorities (USEPA, 1993). The central purpose is to strengthen the links between Federal and state coastal zone management and water quality programs and enhance state and local efforts to manage land use activities that degrade coastal waters and coastal habitats. CZARA identified distinct source categories of nonpoint pollution, one of which is urban areas. Areas addressed by the management measures for urban areas are listed in the box below.

CZARA Management Measures for Urban Areas

• Roads, highways, and bridges
• Runoff from developing areas
• Runoff from construction sites
• Runoff from existing development
• On-site disposal systems
• General sources (households, commercial activities, and landscaping)

Programs developed in response to the Federal regulations vary significantly among states. Activities associated with the construction, operation, and maintenance of roads and highways are also subject to state regulations and programs addressing nonpoint source pollution (USEPA, 1992). Most states have refined their nonpoint source management programs to include BMPs that have proven effective in their area for mitigating water quality impacts. Among the projects most often included in state nonpoint source programs are:

• Production of guidance materials on stormwater management that include the application of BMPs, planning guidance, permitting requirements, and monitoring practices.

• Demonstration projects for particular BMPs under differing land use practices.

• Groundwater and surface water monitoring programs to expand water quality and nonpoint source impact assessments, and provide ongoing water quality data to measure nonpoint source program performance and BMP efficiency.

In large metropolitan areas, watersheds often extend over more than one community and potential problems related to runoff may affect more than one jurisdiction. Intergovernmental cooperation is required in these situations to provide effective stormwater management. Typically in these situations, the local public works agency has the ultimate responsibility for implementation, maintenance, and enforcement of nonpoint source programs. DOTs need to be aware of state and local regulations and their implication for a DOT's activities. Frequently, the DOT will join with local municipalities in developing stormwater management programs and applying for permits. The responsibility for stormwater management related to highway runoff becomes shared between the DOT and the local jurisdictions.

The DOT must determine the relative contribution that its activities make to the total stormwater system within the local jurisdiction and what structural components of the system will be the DOT's responsibility. Once this has been established, the DOT typically determines the runoff volume and constituents associated with these areas, assesses the potential impacts, and establishes a series of structural and nonstructural measures to control the impacts. Establishing the performance of BMPs in ultra-urban areas provides key information for DOT personnel that will aid them in evaluating structural and nonstructural measures.

1.2    Report Development

This report was developed based on an extensive literature search and a comprehensive analysis of documented information currently available. Search criteria were used to identify stormwater BMP monitoring studies that address ultra-urban areas. The focus of the data gathering and analysis effort was to identify new and successful technologies for ultra-urban areas. The following factors were used to distinguish between studies addressing ultra-urban BMPs and studies addressing urban BMPs:

• Limited space available for BMP implementation (less than 0.5 ha [1 ac]).

• Drainage area imperviousness greater than 50 percent.

• Property value of land over $215 per square meter ($20 per square foot).

• Location of BMP in right-of-way (only available space).

• Existence of build-out conditions at the site (lot-line to lot-line development).

Also identified was literature that provided the most recent information available addressing some or all of the issues regarding BMP design and evaluation in ultra-urban settings, including issues such as:

• Stormwater quality, particularly highway and roadway runoff characteristics.

• Site considerations.

• Design criteria.

• Constituent removal effectiveness.

• Operation and maintenance requirements.

• Issues related to the design or operation of the system.

• Monitoring protocols and sampling methods.

• Conclusions and possible recommendations for areas of additional study.

The literature review built on previous compilations, including Evaluation and Management of Highway Runoff Water Quality (Young et al., 1996), Guidance Specifying Management Measures For Sources Of Nonpoint Pollution In Coastal Waters (USEPA, 1993), Design of Stormwater Filtering Systems (Claytor and Schueler, 1996), and A Review and Evaluation of Literature Pertaining to the Quantity and Control of Pollution from Highway Runoff and Construction (Barrett et al., 1995), among others, along with original abstract listings with particular emphasis on recent material and reports. Contacts with stormwater personnel across the country, including academic, state and local government, and DOT personnel tasked with stormwater management, were also used to locate recent studies and additional "gray" literature, those monitoring studies that are not identified through the typical literature search process. In addition, design manuals from various jurisdictions across the country and studies evaluating design criteria for stormwater BMPs were reviewed.

The studies identified in the literature review included monitoring done on stormwater BMPs in an ultra-urban setting and monitoring done on BMPs in urban settings applicable to ultra-urban sites. These studies were entered into a database to facilitate review and analysis of the study results and evaluation of new and innovative technologies. This CD-ROM database describes these selected monitoring studies on stormwater BMPs. The information can be accessed in a number of ways: by study title, by location, by general BMP type, by specific BMP type, and by drainage area size.

The identified studies evaluate stormwater BMPs in both urban and ultra-urban settings and address various design factors in both laboratory (bench-scale) and field settings. Relating the results of these studies to other geographic areas of the country requires comparison and evaluation of site conditions and specific factors that affect the effectiveness of stormwater BMPs. Monitoring protocols and data evaluation techniques significantly affect the representativeness of data and their transferability to other regions of the country.

Of the stormwater BMPs evaluated, most of the studies have concentrated on detention/retention ponds and wetlands. However, recent studies on various filtering systems and water quality inlets appear to be broadening the scope of stormwater BMP evaluation. With a limited number of studies conducted on each technology, defining the performance of each BMP in different regional settings is a difficult task. This report focuses on the unique characteristics specific to ultra-urban settings and provides specific guidance for selecting and siting stormwater management technologies in ultra-urban settings.

1.3    Report Organization

This report illustrates various technologies available for use in ultra-urban settings, and it provides specific design criteria and reported effectiveness of various BMPs where possible. The information is structured in an informative, user-friendly format, with case studies highlighting examples of BMP monitoring throughout the country and tables illustrating the characteristics of each BMP to facilitate comparison and identification of specific technologies appropriate to a given site. The report is organized into separate chapters that address ultra-urban considerations, BMP design criteria, monitoring program design, and BMP selection. The reader can review the report in its entirety, or it can be used as a reference for specific areas of interest.

The specific design criteria for each BMP build on the information presented in the FHWA Manuals: Evaluation and Management of Highway Runoff Water Quality (Young et al., 1996), Urban Drainage Design Manual Hydraulic Engineering Circular 22 (Brown et al., 1996), and Retention, Detention, and Overland Flow for Pollutant Removal from Highway Stormwater Runoff; Volume II: Design Guidelines (Dorman et al., 1996b). When appropriate, and to avoid redundancy between the documents, the reader is referred to the FHWA manuals and other selected sources for additional design information.

Chapter 2 presents the characteristics of ultra-urban areas, including stormwater quantity and quality characteristics, land use description, and an overview of BMPs that can be used in ultra-urban areas. The concerns typical of ultra-urban areas are addressed to highlight factors that may need to be considered when siting BMPs in ultra-urban areas.

Chapter 3 includes specific design information, tailored to the ultra-urban environment, for both structural and nonstructural BMP technologies. These criteria can facilitate determination of the feasibility of various BMPs for a given site. The BMP information addresses applicability, effectiveness, siting and design, maintenance, and cost considerations. Comparison tables are provided at the beginning of the chapter, and a section on innovative technologies (those whose performance was still under evaluation at time of publication) is also provided.

Chapter 4 addresses the process of designing a BMP monitoring program through a discussion of the four different phases involved-planning, design, implementation, and program evaluation. A thorough discussion of ultra-urban runoff characterization is provided to aid in targeting specific runoff constituents in the ultra-urban environment. Methods for monitoring the effectiveness of stormwater BMPs are presented, along with data evaluation techniques and quality control measures. Case study examples of selected BMP monitoring studies are provided in Chapter 5.

Chapter 5 contains selected BMP monitoring studies chosen because they illustrate one or more of the objectives of a monitoring program discussed in Chapter 4, and provide excellent examples of the type of information that can be gained from a BMP monitoring program.

Chapter 6 uses the information presented in the previous chapters to present a decision-making framework for effectively selecting BMPs, based on the goals and objectives of the program, siting considerations, and implementation costs.

References

Barrett, M.E., R.D. Zuber, E.R. Collins III, J.F. Malina, Jr., R.J. Charbeneau, and G.H. Ward. 1995. A Review and Evaluation of Literature Pertaining to the Quantity and Control of Pollution from Highway Runoff and Construction. 2nd ed. Technical Report CRWR 239. Center for Research in Water Resources, the University of Texas at Austin.

Brown, S.A., S.M. Stein, and J.C. Warner. 1996. Urban Drainage Design Manual Hydraulic Engineering Circular 22. FHWA-SA-96-078. Federal Highway Administration, Office of Technology Applications.

Bell, W. 1996. BMP Technologies for Ultra-urban Settings. In Proceedings of Effective Land Management for Reduced Environmental Impact, Tidewater's Land Management Conference on Water Quality, August 22, 1996.

Claytor, R.A., and T.R. Schueler. 1996. Design of Stormwater Filtering Systems. The Center for Watershed Protection, Silver Spring, MD.

Dorman, M.E., J.P. Hartigan, R.F. Steg, and T.F. Quasebarth. 1996a. Retention, Detention, and Overland Flow for Pollutant Removal from Highway Stormwater Runoff. Volume I: Research Report. FHWA-RD-96-095. Federal Highway Administration, Office of Research, Development and Technology.

Dorman, M.E., T.S. George, J.P. Hartigan, and T.F. Quasebarth. 1996b. Retention, Detention, and Overland Flow for Pollutant Removal from Highway Stormwater Runoff. Volume II: Design Guidelines. FHWA-RD-96-096. Federal Highway Administration, Office of Research, Development and Technology.

USEPA. 1992. State and Local Funding of Nonpoint Source Control Programs. EPA-841-R-92-003. U.S. Environmental Protection Agency (USEPA), Office of Water, Washington, DC.

USEPA. 1993. Guidance Specifying Management Measures For Sources Of Nonpoint Pollution In Coastal Waters. EPA-840-B-92-002. U.S. Environmental Protection Agency, Office of Water, Washington, DC.

Young, G.K., S. Stein, P. Cole, T. Kammer, F. Graziano, and F. Bank. 1996. Evaluation and Management of Highway Runoff Water Quality. FHWA-PD-96-032. Federal Highway Administration, Office of Environment and Planning.

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