This report documents the results of NCHRP Project 25-13, “Assessment of Impacts of Bridge Deck Runoff Contaminants on Receiving Waters” in two volumes. The first volume is the project final report (Assessing the Impacts of Bridge Deck Runoff Contaminants in Receiving Waters—Volume 1: Final Report) and the second volume is a handbook for practitioners (Assessing the Impacts of Bridge Deck Runoff Contaminants in Receiving Waters—Volume 2: Practitioner’s Handbook). The project included the http://gulliver.trb.org/publications/nchrp/nchrp_rpt_474v2.pdffollowing: a critical review of scientific and technical literature on water quality impacts and This report may be accessed by Internet users at assessment methods associated with bridge deck runoff, maintenance practices, and spills (see Final Report); a survey of state and provincial highway agencies to obtain information on mitigation measures being used or considered for bridge runoff, maintenance, andspills (see Final Report); development and testing of biological studies including a time-variable bioassay methodology, field monitoring of the benthic macroinvertebrate community, and chemical analyses of runoff and sediments at two bridge sites: I-85/Mallard Creek, North Carolina, and the San Francisco-Oakland Bay Bridge (see Final Report); and the design of a process to evaluate the impact of bridges on water quality and to develop, if necessary, strategies for mitigating impacts on water quality (see Practitioner’s Handbook). The results of the literature review, survey, and biological studies demonstrate that consideration of the unique characteristics of each bridge is crucial to effective evaluation of the potential impacts of bridge deck runoff on receiving waters. Bridge deck length, width, runoff chemical concentrations, traffic volume, and receiving water type (e.g., river, lake, or estuary) are a few of the characteristics of any bridge deck and receiving water environment that must be considered in an evaluation of the potential impacts of bridge deck runoff on receiving waters. The results of NCHRP Project 25-13 also show that three factors have been central in the consideration of bridge deck mitigation systems: (1) state and federal regulatory requirements; (2) state and federal regulatory agency and interested party concerns with the impact of the bridge (e.g., water quality, spills, and endangered species); and (3) receiving water characteristics and designated uses, particularly with high-quality and Outstanding Natural Resource Waters. The results of NCHRP Project 25-13 were incorporated into a process that practitioners can use to analyze the characteristics of a particular bridge deck and receiving water environment, decide whether mitigation is needed, and, if necessary, choose a mitigation strategy. This process, developed with extensive input from stakeholders, is documented in the Practitioner’s Handbook. A more detailed discussion of the study’s conclusions, as well as recommendations for additional research, can be found in chapter 4 of the first volume, Final Report. (A)
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