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.
2019 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 922 Stormwater Infiltration in the Highway Environment: Guidance Manual Aaron Poresky Eric Strecker Myles Gray Kelly Havens Yang (Leon) Li Geosyntec consultants Portland, OR Kevin Koryto City of Boulder, CO Tom Dietrich Mark McCabe Gresham, smith and Partners Columbus, OH Scott Taylor Laura Larsen michael Baker international Carlsbad, CA Robert Pitt university of alaBama Tuscaloosa, AL Subscriber Categories Highways â¢ Environment â¢ Hydraulics and Hydrology Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniquesâthe National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRBâs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs identified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the Federal Highway Administration. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iâs recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 922 Project 25-51 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-48100-7 Library of Congress Control Number 2019955510 Â© 2019 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Boardâs varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.
C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS This Guidance Manual was performed under NCHRP Project 25-51 by Geosyntec Consultants, with assistance from Gresham, Smith and Partners; Michael Baker International; and Dr. Robert Pitt. Primary authors of this report were Aaron Poresky, Principal Investigator; Eric Strecker, Principal Investigator; Myles Gray, Kelly Havens, and Yang (Leon) Li, Geosyntec Consultants, Portland, Oregon; Kevin Koryto, City of Boulder, Colorado (formerly with Geosyntec Consultants); Tom Dietrich and Mark McCabe, Gresham, Smith and Partners, Columbus, Ohio; Scott Taylor and Laura Larsen, Michael Baker International, Carlsbad, California; and Dr. Robert Pitt, Emeritus, University of Alabama, Tuscaloosa, Alabama. The authors would like to recognize the contributions of the following additional authors: Dan Bourdeau, Njoroge Wainaina, Paul Hobson, and Ron Johnson, Geosyntec Consultants. CRP STAFF FOR NCHRP RESEARCH REPORT 922 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs William C. Rogers, Senior Program Officer Jarrel McAfee, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Kami Cabral, Editor NCHRP PROJECT 25-51 PANEL Field of Transportation PlanningâArea of Human and Natural Environment Holly Louise Huyck, Evergreen, CO (Chair) Wendy N. Terlizzi, Idaho Transportation Department, Boise, ID Sajjad Ahmad, University of NevadaâLas Vegas, Las Vegas, NV Henry L. Barbaro, Massachusetts DOT, Boston, MA Henry J. Foster, South Dakota DOT, Fort Pierre, SD Tracey J. Olexa, NTM Engineering, Inc., State College, PA Robert E. Pearson, Wisconsin DOT, Madison, WI Kenneth M. Stone, Washington State DOT, Olympia, WA Nicklas âNickâ Tiedeken, Minnesota DOT, St. Paul, MN Cynthia Nurmi, FHWA Liaison Stephen F. Maher, TRB Liaison
NCHRP Research Report 922: Stormwater Infiltration in the Highway Environment: Guidance Manual (Guidance Manual) provides information, guidance, and tools for planners, designers, regulators, and policymakers to determine when it is appropriate to use infil- tration approaches to manage stormwater in the highway environment. The limitations, risks, and benefits of infiltration best management practices (BMPs) are examined in the context of the built and natural environments (e.g., surface water, groundwater, soils, and infrastructure). The Guidance Manual supports decision-making about the siting, selec- tion, and design of stormwater infiltration BMPs, including effective system design in cases when projects include infiltration. While stormwater permits and other regulations have increasingly prioritized or man- dated the consideration of infiltration BMPs, there is growing concern that requiring infil- tration BMPs may inadvertently lead to other consequences to the natural and built envi- ronments. For instance, research has shown that the upper layers of soil generally capture heavy metals and hydrocarbons, but there is potential for groundwater contamination from stormwater infiltration in some conditions and for some pollutants. Additionally, research has shown that infiltration BMPs can be susceptible to premature failure or substandard performance because of excessive sedimentation, soil compactions, groundwater mound- ing, and other issues. The results of this project will help practitioners better understand the capabilities of infiltration BMPs in different environmental settings and identify the potential limitations and overall environmental effects of infiltration BMPs. In NCHRP Project 25-51, Geosyntec Consultants and its team were asked to develop guidance to address a broad range of issues and needs associated with selecting, siting, and designing infiltration BMPs for mitigating roadway stormwater that may include but not be limited to the following: (1) limitations (e.g., cost, maintenance, regulatory, receiving waters, and geotechnical); (2) effects of climate, soils, topography, geology, vegetation, and land use; (3) effects of pollutants of concern on surface water and groundwater quality; (4) effects on surface water and groundwater quantity (e.g., recharge, baseflow augmenta- tion, and groundwater mounding); (5) identification of gaps in the body of knowledge; and (6) options for improving effectiveness and reducing risk. The report contains a decision-making framework for the various phases of the project design and delivery process. Several topical appendices provide focused technical guidance on key steps in the framework, including extensive guidance on the appropriate investiga- tions to conduct; three software tools to support users with efficient calculations to address groundwater mounding, groundwater quality, and BMP clogging; and a PowerPoint pre- sentation. These additional products can be found on the TRB website (www.trb.org) by searching for âNCHRP Research Report 922â. F O R E W O R D By William C. Rogers Staff Officer Transportation Research Board
1 Chapter 1 Introduction and Orientation 1 1.1 Key Features and Uses of this Guidance Manual 3 1.2 Introduction to Infiltration Approaches for Stormwater Management in the Highway Environment 4 1.3 Rationales for Considering Stormwater Infiltration 5 1.4 Key Limitations to Infiltration as a Stormwater Management Approach 6 1.5 Classes of Infiltration Approaches 7 1.6 Menu of Infiltration BMPs 10 1.7 Overall Infiltration Assessment and Decision-Making Framework 15 Chapter 2 Planning Framework for Early Decision-Making and Tentative BMP Selection 16 2.1 Establishment of Infiltration Objectives 20 2.2 Preliminary Feasibility Analyses to Support BMP Selection 40 2.3 Selection of Preliminary Infiltration Approach 42 2.4 Tentative BMP Selection 61 Chapter 3 Confirmation of BMP Selection Through Prioritized Analyses and Investigations 61 3.1 BMP Confirmation Process by Planning Track 66 3.2 Design Infiltration Rate 67 3.3 Sizing and Performance Feasibility 71 3.4 Geotechnical Findings and Recommendations 72 3.5 Groundwater Quality Findings and Recommendations 75 3.6 Alternative Project Delivery 76 3.7 Step 3 ResultsâFeasibility Findings 79 Chapter 4 Key Considerations for Design, Construction, and Maintenance of Infiltration BMPs 79 4.1 Overview 80 4.2 Soil and Media Clogging and Associated Design Decisions 82 4.3 Selection of Pretreatment BMPs 83 4.4 Adaptable Design Approaches for Infiltration BMPs 86 4.5 Other Design Approaches to Extend Design Life or Improve Resiliency 88 4.6 Construction Site Management and Phasing to Reduce Impacts to Infiltration and Filtration BMPs 92 4.7 Design to Facilitate BMP O&M 94 4.8 O&M Manual 97 4.9 Post-Construction Monitoring C O N T E N T S
99 Chapter 5 BMP Selection and Sizing Case Studies 99 5.1 Case StudyâWSDOT Filter Strip Design Methodology 101 5.2 Case StudyâAdaptive Design Approach for a New Project 106 5.3 Case StudyâBallard Rain Gardens Lessons Learned 109 5.4 Summary 110 Acronyms 111 Glossary of Key Terms 119 References 120 Appendix A Infiltration BMP Fact Sheets 210 Appendices B through J* * Appendices B through J can be found on the TRB website (www.trb.org) by searching for âNCHRP Research Report 922â.