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

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