National Academies Press: OpenBook
« Previous: Summary
Page 40
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 40
Page 41
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 41
Page 42
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 42
Page 43
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 43
Page 44
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 44
Page 45
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 45
Page 46
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 46
Page 47
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Identification of Research Needs Related to Highway Runoff Management. Washington, DC: The National Academies Press. doi: 10.17226/13791.
×
Page 47

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

40 CHAPTER 1 INTRODUCTION 1.1. REGULATORY ENVIRONMENT FOR STATE DEPARTMENTS OF TRANSPORTATION Runoff water quality from highways and developed land is an environmental concern for federal, state, and local agen- cies involved in the planning, design, construction, and main- tenance of transportation facilities. As conveyances of urban stormwater runoff, state department of transportation (DOT) facilities carry suspended metals, sediments, algae-promoting nutrients (nitrogen and phosphorus), floatable trash, used motor oil, raw sewage, pesticides, and other toxic contami- nants into streams, rivers, lakes, and estuaries across the United States (64 CFR 68,722,4,7, Dec. 8, 1999). In 1985, 75% of the states surveyed cited urban stormwater runoff as a major cause of waterbody impairment, and 40% reported construction site runoff as a major cause of impairment (64 CFR 68,726). Congress enacted the Clean Water Act (CWA) in 1948 to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” [33 USC § 1251(a)] (origi- nally codified as the Federal Water Pollution Control Act, 62 Stat 1155). The CWA prohibits the discharge of pollutants from a “point source” (any discernible, confined, and discrete conveyance) into the waters of the United States without a per- mit issued under the terms of the National Pollutant Discharge Elimination System (NPDES) [33 USC § 1311(a), § 1342]. An NPDES permit requires dischargers to comply with technology-based pollution limitations (generally accord- ing to the “best available technology [BAT] economically achievable”) [33 USC § 1311(b)(2)(A)]. Storm sewers are established point sources subject to NPDES permitting requirements [Natural Res. Def. Council v. Costle, 568 F.2d 1369, 1379 (DC Cir 1977)]. In 1987, to better regulate pollution conveyed by stormwater runoff, Con- gress enacted CWA § 402(p), 33 USC § 1342(p), Municipal and Industrial Stormwater Discharges. Sections 402(p)(2) and 402(p)(3) mandate NPDES permits for stormwater dis- charges “associated with industrial activity,” discharges from large and medium-sized municipal storm sewer systems, and other activities, including construction sites. In CWA § 402(p), Congress also directed a second stage of stormwater regula- tion by ordering the Environmental Protection Agency (EPA) to identify and address sources of pollution not covered by the Phase I Rule and to establish procedures and methods to Laws and Regulations Affecting Department of Trans- portation Water Quality Management The National Environmental Policy Act and the Clean Water Act of 1972, as amended. These acts hold federal decision makers accountable for activities having the poten- tial to impact features of the natural environment—in par- ticular, water quality (Bank et al., 1995). The National Pollutant Discharge Elimination System. This program requires discharge permits for industrial and municipal (point source) effluents containing pollutants. Effluent regulations include characterization of stormwater runoff, possibly originating directly from highways and the construction and maintenance of the highway systems. The Nonpoint Source Management Programs, Title 3, Section 319. This program also promotes the implemen- tation of best management practices regarding highway runoff, as a potential nonpoint source pollutant of surface and ground water. The Department of Transportation National Transpor- tation Policy, the Federal Highway Administration Environmental Policy Statement, and the Intermodal Surface Transportation Efficiency Act. These policies and acts specify increased environmental responsibilities for policies and programs developed by federal and state transportation agencies. The Coastal Zone Reauthorization Amendment. This amendment regulates highway runoff water quality and its environmental impacts in coastal areas. Other legislation—such as the Safe Drinking Water Act, the Endangered Species Act, the Resource Conser- vation and Recovery Act, and the National Wild and Scenic Rivers Act—also contains provisions that may pertain to the water quality of highway runoff. control them as “necessary to mitigate impacts on water qual- ity” [33 USC § 1342(p)(5)]. For municipal-type stormwater systems, the technology- based requirements in the federal stormwater regulations call for the implementation of controls [procedures and best man- agement practices (BMPs)] to reduce the discharge of pollu- tants to the maximum extent practicable (MEP). In Septem- ber 2003, the Ninth Circuit Court of Appeals amended an

41 earlier decision concerning the Phase II program and recon- firmed that the CWA requires that municipal stormwater dischargers (including state transportation agencies) have to remove pollutants to the MEP. Attainment of water quality standards is not required but may be added at the discretion of the state. For construction projects that disturb areas of one acre or more, technology-based requirements include the use of BAT and best conventional pollutant control tech- nology (BCT). DOTs meet these obligations through the implementation of control programs and technologies—BMPs. As used in this document, the term BMP refers to operational activities or physical controls applied to stormwater and other runoff to reduce pollution. BMP refers to structural and nonstruc- tural controls that have direct effects on the release, transport, or discharge of pollutants. 1.1.1. Total Maximum Daily Loads for Impaired Waters The CWA, amendments, and associated regulations require that states assess the condition of surface waters within their jurisdictions to determine whether they are impaired. Where water quality is not adequate to sustain beneficial uses, sur- face waters must be listed as required by Section 303(d) of the CWA. For specific constituents, a total maximum daily load (TMDL) must be developed for each of the listed seg- ments for the constituents that are contributing to the impair- ment of beneficial uses. The TMDL is the maximum pollu- tant load that can be assimilated by the waterbody without impairing the water’s beneficial use. The task of properly determining TMDLs for constituents is staggering; more than 20,000 such impaired waters have been identified nationally, comprising more than 300,000 miles of rivers and streams and more than 5 million acres of lakes. Once a TMDL is developed for a surface waterbody, a waste load allocation (WLA) must be developed. The WLA speci- fies how much of a given constituent can be contributed by each discharge and discharger, including highway agencies, to the waterbody. As TMDLs and WLAs are developed for the impaired segments, dischargers, including highway agen- cies, have to implement BMPs to reduce their contribution of a constituent from transportation land uses and associated facilities. 1.1.2. Other Laws and Regulations Imposing Water Quality Requirements on Departments of Transportation In addition to NPDES and TMDL requirements, highway runoff management techniques must be consistent with the objectives of nonpoint source control programs under Sec- tion 319 of the CWA and state coastal nonpoint pollution control plans developed under Section 6217 of the Coastal Zone Act Reauthorization Amendments. Other legislation such as the Safe Drinking Water Act, the Endangered Species Act (ESA), the Resource Conservation and Recovery Act, and the National Wild and Scenic Rivers Act also contain provisions that may pertain to the water qual- ity of highway runoff. The water quality requirements for species listed as threatened or endangered under ESA have presented particular challenges for DOTs. Often state and EPA requirements for attaining water quality standards may not replicate necessarily what the National Oceanic and Atmo- spheric Administration’s (NOAA’s) National Marine Fisheries thinks is needed or what the U.S. Fish and Wildlife Service deems appropriate. On a state-by-state basis, DOTs face a wide range of water quality control requirements with which they must comply. Many of these requirements are based on previous research, not conducted necessarily by those same DOTs. In some cases a DOT’s requirements have been based on the require- ments of other DOTs or on a limited amount of supporting data. These requirements then become the basis for the guidelines and manuals. Research results indicate that 60% of state DOTs have developed highway runoff manuals for designers. Many DOTs also have developed training for con- struction and maintenance staff. However, much research remains to be done in order to implement the most effective and efficient water quality programs and measures possible and to improve continuously runoff water quality. 1.2. SUMMARY OF GKY STUDY AND GAPS In March 1998, the AASHTO Standing Committee on Research (SCOR) met to review and select projects for the FY1999 NCHRP program. SCOR noted that there were 10 dif- ferent problem statements addressing the impacts and man- agement of highway runoff. SCOR directed an NCHRP panel to convene a panel of experts to investigate the existing state of practice; identify research issues, gaps, and needs; under- take research on high-priority topics; and recommend proj- ects for future funding. The first effort initiated by the panel was Project 25-20. The resulting report (from GKY and Associates, Inc.), Manage- ment of Runoff from Surface Transportation Facilities: Syn- thesis and Research Plan, was published in March 2001. The GKY report was accompanied by the Water Quality Knowl- edge Database (CD-based), which includes 14 full-length doc- uments from the existing literature. Also on the CD is a lim- ited annotated bibliography of 127 items listed by author; however, the annotations generally consist of only an abstract, which briefly reviews what was studied but only occasion- ally includes research results. GKY listed 916 unannotated references on the CD. GKY asked a variety of transportation practitioners each to specify three areas in which they thought research was needed. GKY then categorized those areas according to the “a priori ranking of panel issues” or “high-likelihood priority

areas” given to them by the NCHRP 25-20 oversight panel. Subsequently, GKY produced a research needs statement for each of the 11 areas (approximately one per topic area iden- tified in advance by the panel). The following subsections summarize briefly the contents of each chapter in GKY’s report. 1.2.1. GKY Report, Chapter 2 Summary: High-Likelihood Research Need Topic Areas Chapter 2 summarizes and ranks topic areas of highway runoff research gaps and needs identified a priori by the NCHRP panel. The panel’s high-ranking topic areas of interest included receiving waters assessment, BMPs, and information systems and technology exchange. Medium- ranked topic areas of interest included systems planning, constraints and regulations, and stormwater hydrology and hydraulics related to water quality. Low-ranking topic areas of interest included constituents and loadings and ground- water. 1.2.2. GKY Report, Chapter 3 Summary: Information Technology Chapter 3 describes the following: how the information compiled on the CD is organized and how it can be searched, a listing of the 14 primary references included on the CD, sources of information, an evaluation of the com- piled information, and identification of the gaps in the literature review. The evaluation of the compiled informa- tion is organized according to three primary topic catego- ries related to highway runoff: loadings, intervention, and impacts. Under the loadings category, highway runoff pollutant sources are identified, and several studies are referenced. Three primary subcategories are discussed briefly: the influence of average daily traffic on pollutant loadings, land use-based pollutant loads characterization, and the correla- tion of suspended sediment with nutrients and metals. Although the topic of highway runoff water quality charac- terization has been well studied, several more subtopics either were mentioned only briefly or were overlooked entirely in the GKY study. Those subtopics include, but are not limited to, first flush characterization, highway construction and maintenance, atmospheric deposition, cold weather studies, and fate and transport of highway pollutants. Under the intervention category, stormwater BMPs are discussed according to BMP type: conventional structural BMPs, space-limited BMPs, and nonstructural BMPs and related considerations. General BMP design is discussed and a few design manuals are referenced; however, specific 42 information on individual BMP types is not included. Fur- thermore, despite the breadth of the category of BMP per- formance, only one BMP performance study is included in the document. This is considered the product’s largest shortcoming. Hundreds of studies evaluate BMP perfor- mance, but since there are so many different BMP types and configurations, this is an area of study that is still develop- ing, particularly in relation to highway runoff and space- limited BMP designs. The GKY report provides the most information under the “impacts to receiving waters category” (more than it pro- vides in the loadings and intervention categories). The report presents an adequate discussion of the steps involved in assessing receiving water impacts: obtaining and reviewing existing data, the use of water quality and ecological impact models, conducting bioassessments, and toxicity testing. Although these are important areas of study, other topics related to receiving water impacts were not discussed ade- quately, including channel stability (e.g., sedimentation and scour), wetland mitigation, groundwater quality impacts, mixing zone dynamics, bioaccumulation and bioavailability, and in-stream BMPs. 1.2.3. GKY Report, Chapter 4 Summary: Practitioner Survey Chapter 4 describes the results and conclusions of a survey of transportation practitioners. The GKY report indicated that the practitioners surveyed had little agreement on where research gaps and needs are, but the report provided a ranking of potential research topic areas in the following order of per- ceived priority: water quality receiving water impacts, deicing, data collection and information transfer, habitat assessment and ecological issues, bridge BMPs, BMP site constraints, nonstructural BMPs, and BMP effectiveness and performance. In addition, the report noted that practitioners expressed an overall need for information, with an emphasis on erosion and sediment control, to assist in the selection and design of appropriate BMPs. GKY judged the lack of information exchange as the most likely cause of the discrepancy in prac- titioners’ opinions on research gaps and needs, as a number of DOTs made suggestions for improved information transfer such as an Internet-based bibliographic database. 1.2.4. GKY Report, Chapter 5 Summary: Analysis of Information GKY ranks the following as the highest priority research topics: receiving water quality assessment, space-limited BMPs, information systems, constituents and loads, biological/ ecological impacts, groundwater, habitat quality, BMP design, systems planning, BMP maintenance, and BMP selection.

1.2.5. GKY Report, Chapter 6 Summary: Research Program Based on the ranked research topic areas identified in Chapter 5, Chapter 6 presented a 12-project, 5-year research program organized according to ranked problem statements. Each problem statement includes the research topic and needs, the project objectives, estimated budget and timeline, and the urgency and payoff potential of the project. The proj- ect titles and associated problem statements are listed in Table 1-1. 1.2.6. GKY Report, Overview and Conclusions The GKY study identifies primary highway runoff manage- ment research topics in need of additional study. However, the context is broad and describes inadequately the research top- ics identified. For instance, the research topic of BMP effec- tiveness and performance is extensive and may involve several levels of investigation. Furthermore, the GKY study defines neither BMP effectiveness nor performance even though there are several different definitions currently in use (Strecker et al., 1999). The document focuses on ecological and biologi- cal impacts and provides some valuable references and iden- tifies some important topic areas. With regard to the broader range of highway runoff management research and research needs, the GKY findings require expansion in the areas of receiving water impact assessment, highway runoff charac- terization, BMP evaluation, systems planning, and data col- lection and analysis. NCHRP 25-20(02) attempts to identify the gaps in the GKY study. Based in part on the recommendations of the GKY study, the panel initiated Project 25-20(01): Evaluation of Best Management Practices for Highway Runoff Control. The project was contracted to Oregon State University and has been combined with a study on low-impact development; the final report is scheduled for completion in the winter of 2004. The research will evaluate the basic scientific and technical criteria that can be used for the quantitative assessment of wet-weather flow control alternatives (often referred to as BMPs) for highways and other highway-related facilities and will apply the results of the evaluation to facilitate effective implementation of these controls. To avoid duplication of project 25-20(01), the current project, 25-20(02) limits the category of evaluation of best management control practices to include only a summarization of related topics, gaps, and research needs found during the literature review. A detailed assessment of BMP unit processes and treatment perfor- mance in relation to BMP design will be provided in the NCHRP 25-20(01) report. The GKY report includes an overview of potential fund- ing sources. Identification of funding sources is not part of the scope of NCHRP 25-20(02), but related information on potential funding sources is included in the original report. 43 1.3. GOALS AND OBJECTIVES OF NCHRP 25-20(02) NCHRP 25-20(02) will identify and describe research proj- ects that will address priority needs in the area of highway runoff management and control. The assessments described in this document are based on DOT research priorities and a broader search of the available data, studies, and DOT research in progress than was available in the initial 25-20(01) research. Final research statements will be presented in the final report, subsequent to panel approval of the research team’s assessment. 1.4. RESEARCH METHODOLOGY This comprehensive highway runoff investigation includes a review of readily available highway runoff literature and state highway transportation agencies’ unpublished literature, current research efforts, and research priorities that could be acquired through contact with all 50 states. A discussion fol- lows on the methodology used for each portion of the research for this project. 1.4.1. Contact with Water Quality Professionals Realizing that information on stormwater quality research and needs may occur in different and often multiple parts of a state transportation agency, researchers contacted state trans- portation agencies and divisions within these agencies to ascertain current practices, problems and issues, and research related to stormwater quality. Research directors identified on AASHTO’s list of members for SCOR were contacted by phone and e-mail to locate existing research and research in progress. Lead stormwater professionals in each agency were asked about research in progress and research priorities. The practitioner contact effort for 25-20(02) started with a long list of research needs areas, including questions raised in TRB Committee A2AO3, AASHTO’s Natural Resources Subcommittee, and through the Standing Committee on the Environment’s Environmental Technical Assistance Pro- gram. Questions also were identified by calling leading state DOTs regarding water quality issues (California, Maryland, and Washington State). The list of potential questions was reviewed by practitioners and researchers in the aforemen- tioned states, by the NCHRP 25-20 Chair, and by the full team of consultants involved in this effort. The resulting sug- gested revisions and additional questions were incorporated into the list of priority research areas ranked by DOTs. All 50 state DOTs were contacted successfully to provide their level of prioritization of the final list of 45 research areas. Each state DOT provided a low-medium-high ranking of research interest to attain a finer gradation of understand- ing of DOT research needs than indicated by the GKY study. In addition, to ensure that the full range of potential research

44 TABLE 1-1 Summary of potential research projects identified by GKY and Associates No. Project Title Problem Statement 1 Identification and Development of Regional Aquatic Biological Indicators to Assess Impacts of Highway Runoff Biological indicators can be used to assess receiving waters impacts of highway runoff and to evaluate the effectiveness of stormwater best management practices (BMPs). Practitioners need guidance on the appropriate use and interpretation of cost-effective methods of regional biological indicators. 2 Research Methods for Assessing the Toxicity of Highway Runoff Several toxicity testing methods are available to assess the acute and chronic toxicity of water quality samples. However, results are highly variable depending on the method used, and each method has a limitation on its applicability. Highway practitioners need toxicity testing protocols to address specifically the runoff entering different receiving water ecosystems. 3 Water Quality Management Information System Highway practitioners rely on published literature for addressing highway runoff management and control. Practitioners need a readily accessible, up- to-date information system for searching and reviewing existing studies and reports, as well as for adding new information as it becomes available. 4 Isolation of Pollutants in Transportation Runoff Highway runoff has been recognized as a potential contributor to water resources impairment, but the specific water quality parameters causing impairment are not well known. Practitioners need access to statistically significant runoff quality data from highway facilities for the development of cost-effective monitoring programs. 5 Causal Analysis of Pollutants in Transportation Runoff In order to manage effectively the quality of highway runoff at the source, practitioners need to understand the factors that influence the chemical characteristics of the highway runoff, such as average daily traffic, climate, rainfall chemistry, construction materials, and more. 6 Integration of Multidisciplinary Methods for Evaluation of Transportation Runoff Impacts to Aquatic Ecosystems The goals of highway runoff quantity management and runoff quality management often conflict. Practitioners need methods and alternatives for dealing with both issues of highway runoff management. 7 Expert System for Transportation BMPs Practitioners need readily available access to BMPs information and a means of quickly applying applicable portions of the information to site-specific situations. 8 Design Criteria for Bridge BMPs NCHRP Project 25-13 is investigating the impacts of bridge runoff on receiving waters. When the project is complete, practitioners will need design guidance on BMPs for bridge runoff. 9 Heavy Metals Management Options Heavy metals are known highway runoff pollutants that tend to migrate from the roadway to receiving streams. Practitioners need effective ways to confine heavy metals to the rights-of-way. 10 Demonstration of Ultra-Urban BMPs Practitioners need access to case studies that evaluate the performance of ultra-urban BMPs, so that applicable and effective space-limited BMPs can be selected. 11 Hydraulics and Hydrology of BMP Retrofitting Practitioners need practical guidance for retrofitting existing flood control and drainage structures to maximize water quality benefits. 12 Enhanced Expert System for Transportation BMPs Building upon the system developed under No. 7, an enhanced expert system would include additional information and results made available since the system’s initial deployment.

interests was covered, DOTs were asked to describe agency research interests in an open-ended manner for design, con- struction, maintenance, and receiving water assessment. This intensive interview and survey effort was designed to pro- duce a current and accurate basis for identifying present gaps and research needs. The following DOT professionals par- ticipated in identifying and ranking research needs: • Environmental, stormwater, and civil engineers; • Research engineers; • Senior hydraulics engineers and heads of hydraulic divisions; • Chiefs of design; • Directors of location and environment; • Managers of roadside development sections; • Agronomists, geologists, and landscape architects; • Environmental program managers and other section chiefs; • Wetlands unit supervisors; • Bioengineering managers (for Section 401 and 404 concerns); • Natural resources specialists and unit managers; • Water quality and resources specialists; and • Directors of university stormwater research centers who, on referral, worked closely with the DOTs. The survey, included as Appendix A in this report, was conducted by phone and on line. All information was entered into an online system, so that results may be viewed easily (go to www.vennerconsulting.com/stormwater and click “View Results”). In an effort to minimize inconvenience to DOT participants and to rationalize the broad scope of information being collected, two state-initiated water-quality surveys were combined. Researchers pooled the existing data, voluntarily assisted the Virginia Transportation Research Center (VTRC) in completing the survey effort they had started, and focused on reaching all 50 state DOTs for participation in sections 2 through 8, which provide information most directly pertinent to NCHRP 25-20(02). At the same time they were completing previously started surveys, researchers solicited information on the whole set of questions and presented the current state of knowledge about practice in each state for completion and updating as neces- sary or desired by the DOT. A large number of states con- tributed information, facilitating related research efforts at VTRC and providing a basis for further research and infor- mation sharing about water quality best practices. DOT research directors were contacted separately to report on the water quality research performed or funded by their state DOT and to provide electronic copies or online links if avail- able. In many cases researchers were referred to the water quality practitioners who were the focus of the survey effort. This wide level of involvement produced input about exist- ing research programs and about state DOTs’ research pref- 45 erences. In conjunction with the literature review below, the input has provided a solid foundation for identified research needs. 1.4.2. Review of Literature and Current Research Information on current practices, problems and issues, and research related to highway runoff management was reviewed to identify relevant work and where the work is occurring. Data sources included, but were not limited to, the following: • 2001 GKY report (materials related to the survey effort were not available from GKY and Associates); • ASCE/EPA BMP Database and other ASCE publications; • FHWA studies and publications; • EPA publications; • Water Environment Research Foundation and Ameri- can Water Works Research Foundation; • Environmental research in progress online database at the Center for Transportation and the Environment; • TRIS database at TRB; • TRB A2A03 Hydrology, Hydraulics, and Water Quality Committee; • University water research centers online publications; and • Recent, current, and planned research by state DOTs (internally conducted research or research conducted in conjunction with universities and other contractors). A database was created using the above sources to hold the available citations as well as to enable the categorization of the publications. Researchers identified and obtained more than 2,500 annotated bibliographies related to highway run- off management. More than 900 of the most relevant cita- tions were categorized on the basis of various combinations of key word searches. The categorization scheme in the data- base was designed to reflect closely the major categories of this document. Table 1-2 shows a breakdown of the number of documents under each primary category. In addition to the primary categories, each citation is cat- egorized further with objective statements and by document type. The database was created with an initial set of objective statements that represented various areas of interest and pos- sible knowledge gaps on the subject of highway runoff man- agement. The ability to extend the initial set of the objects was built into the database enabling researchers to add objec- tive statements as the need arose during the literature review process. The number of unique objective goals is more than 300 for the categorized documents. More than 400 of the cat- egorized documents were assigned more than one objective. Researchers further grouped the research objectives under each primary category into groups such as general objectives, water quality objectives, hydrologic/hydraulic objectives, and in some cases, economic objectives and public percep- tion objectives. In addition to categorizing object statements,

researchers reviewed the BMP types and pollutants studied and discussed in the documents and extracted study loca- tions, study goals, and monitoring information where avail- able. The BMP names were selected from a list of more than 100 practices, some of which may refer to similar BMPs. Currently, the database contains links to more than 300 full- text online documents. The database was used mainly as a tool to expedite the literature review process; however, with additional refinement, an online version of the database could become a valuable information exchange tool for DOTs, con- sultants, and researchers. 1.4.3. Delivery of Findings The knowledge gleaned from the survey of state DOTs and the literature review was compiled to identify and prior- itize research needs and gaps in highway runoff management and receiving waters impacts. For the most part, researchers found that the gaps and needs identified during the literature review agreed with the gaps and needs identified by the sur- vey of state DOTs. However, a few research areas not iden- tified during the literature search were identified by state DOTs and vice versa. This paired approach arguably offers a more comprehensive compilation of research needs than would have resulted if the review of literature were conducted first and the survey second, as the research team would have recommended in a more lengthy research period. The findings of the DOT survey are presented primarily as tables of ranked and sorted research priorities and associated text. The findings of the literature review are presented in summary paragraphs identifying potential research gaps and needs for each subtopic area. The findings of both investiga- tions are compiled and summarized in a final narrative and matrix of ranked and sorted research topic areas. 1.4.4. Ranking of Research Needs The three separate rankings were used to prioritize (on a scale from 1 to 5) the research needs shown in Table 5-1. The DOT rankings are based on the results of the practitioner sur- veys, which include both the average score assigned to each topic area and the self-identified research gaps and needs. 46 Subject areas that were assigned lower priorities by DOTs were assigned lower rankings. The literature review rankings are based on the availability of documents on the subject matter and the amount of research that has been done or is being done on the subject as well as on the recommended areas of additional research often included in the conclusion of reported research. Using a rating scale from 1 to 5, well- covered subject areas are assigned a lower ranking and less covered subject areas are assigned a higher ranking. The third ranking—the ranking from the researchers—is based on a combination of the literature review ranking, the DOT rank- ing, and professional judgment of the research gaps and needs encountered in the extensive work in the field of stormwater management. The third ranking also is based on a scale of 1 to 5, with 1 being assigned to lower priority research needs and 5 being assigned to higher priority research needs. 1.4.5. Document Organization The document begins with an overview of the 45 research priority areas ranked by DOT water quality practitioners and an overview of further (often overlapping) research topics recommended by DOTs (in their own words, in various cate- gories). This section is followed by the literature review, which attempts to summarize key studies and knowledge in each area, and in some cases, provides examples for use in developing the prioritized research needs. The literature review is not an exhaustive discussion of the details of all related highway runoff research work that has been completed. Due to the nature of the primary research categories, an individual study may include components of multiple cate- gories or subcategories, making these studies difficult to clas- sify. Effort was made to cross-reference studies that span more than one category or subcategory for the maximum ben- efit to the reader and for a more complete assessment of research gaps and needs. Study classification is partially sub- jective and dependent upon the depth of information included in the reviewed literature, which in many cases is limited to only an abstract. Consequently, it is possible that the reader may not completely agree with the inclusion of some research topics within a chosen research category. Therefore, in addi- tion to cross-referencing studies, effort also was made to TABLE 1-2 Database document summary by primary categorization Primary Category Number of Documents Evaluation of Stormwater Control Facilities and Programs 332 Watershed-Based Approaches 73 Highway Runoff Characterization and Assessment 232 Receiving Waters Impact Assessment 80 Design of Stormwater Control Facilities and Programs 108 Other 59 TOTAL 884

describe the rationale for including some studies under a par- ticular research category for those studies where classifica- tion was not obvious. This report includes a table of the identified research needs with explanations on how the needs were ranked by the state DOTs as well as the researchers’ assessment of the needs based on the literature. Researchers then gave an overall ranking to a research need and identified the top priorities. 47 Research statements developed by the team are included in the Executive Summary. Following this introductory section, the main section headings are DOT Research Preferences, Review of Pub- lished Literature and Potential Research Needs, and Sum- mary of Identified Research Gaps and Needs. The review of published literature has been organized according to the pri- mary research categories identified in Table 1-2.

Next: Chapter 2 - Department of Transportation Research Preferences »
Identification of Research Needs Related to Highway Runoff Management Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB's National Cooperative Highway Research Program (NCHRP) Report 521: Identification of Research Needs Related to Highway Runoff Management summarizes significant stormwater management practices and research efforts, and it identifies the most pressing gaps and needs in the current state of knowledge in over more than 30 subject areas. The report includes full research project statements for the topics considered to be of highest priority.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!