Achieving Highway Runoff Volume and Pollutant Reduction Using Vegetated Compost Blankets: A Guide (2023)

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2023 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 1040 Achieving Highway Runoff Volume and Pollutant Reduction Using Vegetated Compost Blankets A GUIDE Allen P. Davis Ahmet Aydilek Gary K. Felton Erica R. Forgione University of Maryland College Park, MD Subscriber Categories Environment • Hydraulics and Hydrology Research sponsored by the American Association of State Highway and Transportation Ofcials 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 techniques—the 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 (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. 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 TRB’s 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; TRB’s 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 iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s 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 https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 1040 Project 14-39 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-69843-6 Library of Congress Control Number 2023934300 © 2023 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trade- marks of the 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA 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; the FHWA; or the program sponsors. The Transportation Research Board does not develop, issue, or publish standards or spec- ifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. 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 manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.

e 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. e 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. e 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. e 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. e 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.nationalacademies.org. e Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. e 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. e Board’s 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. e 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 CRP STAFF FOR NCHRP RESEARCH REPORT 1040 Christopher J. Hedges, Director, Cooperative Research Programs Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Christopher T. McKenney, Senior Program Officer Sheila A. Moore, Program Associate Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications NCHRP PROJECT 14-39 PANEL Field of Maintenance—Area of Maintenance of Way and Structures Robert A. Armstrong, Wisconsin Department of Natural Resources, Madison, WI (Chair) Anne Katherine Ewing, Arkansas Department of Transportation, Little Rock, AR Robert LaRoche, John Turner Consulting, Bowdoinham, ME Alex Nguyen, Washington State Department of Transportation, Seattle, WA Natalia M. Sanabria-Andino, FCMC Consulting, LLC, Orlando, FL Dwayne Stenlund, Minnesota Department of Transportation, Saint Paul, MN Scott M. Taylor, Michael Baker International, Inc., Carlsbad, CA Susan Cheung Jones, FHWA Liaison Stephen F. Maher, TRB Liaison

NCHRP Research Report 1040: Achieving Highway Runoff Volume and Pollutant Reduction Using Vegetated Compost Blankets: A Guide presents a state-of-the-art investigation into vegetated compost blankets (VCBs) used for stormwater control and their resulting impacts on vegetative establishment, stormwater volume reduction, and water quality improvement. The research was based on a comprehensive analytical, field, and laboratory assessment. This report will be of immediate interest to design and maintenance engineers. Selecting cost-effective low-impact development (LID) treatments is essential for state departments of transportation (DOTs) to address increasing requirements for water quality and hydrologic management. Vegetated filter strips along highways, an accepted LID best management practice (BMP), are a cost-effective alternative to hydraulically engineered BMPs. However, these treatments may be limited by site constraints (such as limited right- of-way and steep side slopes), and their effectiveness may vary depending on climate, soils, and other factors. VCBs can overcome some of these limitations by promoting stormwater filtration, reten- tion of runoff, and infiltration of stormwater into the underlying soils while potentially removing pollutants and reducing flow volumes. As a simple retrofit on roadside embank- ments, VCBs’ low maintenance requirements have the potential to prove a good return on investment. In order to provide state DOTs with an effective and economical BMP to assist them with effective uses of VCBs in highway projects, research was needed to evaluate the hydro- logic and water quality benefits of VCBs as used in a wide variety of roadway settings. This involved determining pollutant removal capability and capacity; assessing VCBs’ ability to detain and retain runoff; and gauging the effect of climate, soils, compost composition, compost blanket thickness, and other parameters on VCB performance. Under NCHRP Project 14-39, “Using Vegetated Compost Blankets to Achieve High- way Runoff Volume and Pollutant Reduction,” the University of Maryland was asked to (1) develop performance curves for surface-applied VCBs on slopes of 3:1 or flatter that remove pollutants of concern, control erosion, reduce volume, and support vegetation when it is placed on an existing roadway embankment; and (2) provide construction specifications, standard details, and a decision matrix that provides guidance on the use, limitations, design, and implementation of VCBs on existing roadway embankments. F O R E W O R D By Christopher T. McKenney Staff Officer Transportation Research Board

1 Summary 5 Chapter 1 Introduction 5 Project Background 10 Project Goals and Objectives 12 Chapter 2 Literature Review 12 Introduction 12 Compost Characteristics and Types 20 Compost Use in Stormwater Control Measures 25 Compost, Erosion Prevention, and Sediment Control 34 Integrity and Resilience of Compost Blankets 37 Compost Applications and Water Quality 39 Synthesis 41 Chapter 3 Experimental Design and Methods 41 Field Site Selection and Design 44 Field Site Construction and Monitoring 51 Greenhouse Site Experimental Design 57 Greenhouse Experiment Construction and Setup 61 Vegetative Establishment Measurements 64 Soil Analysis 67 Chapter 4 Vegetative Establishment 67 Grass Height and Cover Data 77 Biomass Data 81 Soil Improvement 83 Practical Observations 86 Design 89 Chapter 5 Hydrologic Performance 89 Underlying Soils 89 Flow Patterns 89 Field 104 Greenhouse 108 Field and Greenhouse Comparison 111 Design 117 Chapter 6 Water Quality Performance 117 Introduction 125 Total Suspended Solids 131 Nutrients Summary 137 Total Nitrogen 146 Total Phosphorus C O N T E N T S

146 Heavy Metals Summary 154 Total Copper 163 Total Zinc 163 Summary 167 Design 178 Chapter 7 Summary and Conclusions 178 Summary of Research 178 Conclusions 186 Project Recommendations 187 New Research Questions 189 References 198 Appendix A Acronym Table 200 Appendix B Methods 213 Appendix C Hydrology 221 Appendix D Water Quality