Permeable Shoulders With Stone Reservoirs Requested by: American Association of State Highway and Transportation Officials (AASHTO) Standing Committee on the Environment Prepared by: David K. Hein, P.Eng. Principal Investigator Applied Research Associates, Inc. 100 Trade Center Boulevard, Suite 200 Champaign, Illinois 61820 and Eric Strecker, P.E., Aaron Poresky, P.E. and Dr. Robert Roseen, P.E. Geosyntec Consultants Marie Venner Venner Consulting (October 4, 2013) The information contained in this report was prepared as part of NCHRP Project 25-25, Task 82, National Cooperative Highway Research Program, Transportation Research Board. SPECIAL NOTE: This report IS NOT an official publication of the National Cooperative Highway Research Program, Transportation Research Board, National Research Council, or The National Academies. Page | ii Acknowledgements This study was requested by the American Association of State Highway and Transportation Officials (AASHTO), and conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 25-25. The NCHRP is supported by annual voluntary contributions from the state Departments of Transportation. Project 25-25 is intended to fund quick response studies on behalf of the AASHTO Standing Committee on the Environment. The report was prepared by David K. Hein, P.Eng. and Lori Schaus, P.Eng. of Applied Research Associates, Inc., Eric Strecker, P.E., Aaron Poresky, P.E. and Dr. Robert Roseen, P.E. of Geosyntec Consultants and Marie Venner of Venner Consulting. The work was guided by a task group co-chaired by Frannie Brindle, Oregon DOT and Scott McGowen, California DOT. The project was managed by Nanda Srinivasan, NCHRP Senior Program Officer. The panel for this project included: Ms. Frannie Brindle (Oregon DOT), Mr. Scott McGowen (CA DOT), Mr. Andrew Gisi (KSDOT), Mr. Kent Hansen (National Asphalt Pavement Association), Mr. Gary Lantrip (Texas DOT), Mr. Robert Rodden (American Concrete Pavement Association), Mr. Brian Toombs (Burgess and Niple. Incorporated), Mr. Njoroge W. Wainaina (NC DOT). The FHWA liaison was Brian Beucler. Disclaimer The opinions and conclusions expressed or implied are those of the research agency that performed the research and are not necessarily those of the Transportation Research Board or its sponsors. The information contained in this document was taken directly from the submission of the author(s). This document is not a report of the Transportation Research Board or of the National Research Council. Page | iii Abstract The objective of this study is to evaluate the suitability of using permeable pavement for roadway shoulder applications. Permeable pavement systems are designed to minimize environmental impacts, stormwater runoff, and flooding and to treat or remove pollutants by allowing stormwater to infiltrate through the pavement in a manner similar to pre-development hydrologic conditions State Departments of Transportation (DOTs) and other municipal organizations have expressed interest in permeable shoulders to assist in the overall management of stormwater. Water from the surface of the roadway would flow into the permeable shoulder into a stone reservoir to temporarily store and treat runoff before infiltration into the roadway subgrade soils and/or discharge to other stormwater conveyance and treatment systems. The primary benefits of permeable pavements are to reduce stormwater runoff volume, reduce stormwater runoff peak flows, reduce surface ponding, reduce stormwater pollutant load, decrease downstream erosion and increase groundwater recharge. Careful consideration of design features and construction techniques are necessary to ensure their success. Key design features include a careful assessment of the permeable pavement site and its surrounding land use to ensure that the pavement surface does not become contaminated with sand/dust or vegetative matter. A rational assessment of the traffic to which the pavement will be exposed will permit the designer to ensure that the pavement has sufficient structural capacity for its design life. A hydrological design taking into account rain water landing on the pavement and water shed from the highway lanes can be accommodated into the permeable pavement and then properly treated for water quality improvements and permitted to exit the pavement either through infiltration into the subgrade or controlled through underdrains. Construction processes and techniques should consider the protection of the permeable pavement from contaminants during construction and to ensure that the pavement is able to accommodate both vehicle loading and water infiltration and exfiltration in accordance with the pavement design. Finally, with all pavements, maintenance practices should including occasional vacuum sweeping to ensure the longevity of the permeable surface with repairs completed to address any localized deficiencies. Page | iv Table of Contents Table of Contents .................................................................................................................................... iv List of Tables ............................................................................................................................................. v List of Figures ........................................................................................................................................... v List of Appendices ................................................................................................................................... vi 1. Introduction ...................................................................................................................................... 1 2. Scope ................................................................................................................................................. 1 2.1 Structural and Hydrologic Design ........................................................................................................... 2 2.2 Construction Issues................................................................................................................................. 2 2.3 Maintenance Standards ......................................................................................................................... 3 3. Permeable Pavement Technology .................................................................................................... 3 3.1 Permeable Pavement System ................................................................................................................. 4 3.2 Porous Asphalt........................................................................................................................................ 6 3.3 Pervious Concrete .................................................................................................................................. 7 3.4 Permeable Interlocking Concrete Pavement .......................................................................................... 8 4. Permeable Shoulder Feasibility Decision Criteria ............................................................................. 9 4.1 Permeable Shoulder Feasibility Decision Matrix .................................................................................. 14 5. Structural and Hydrological Design of Permeable Pavements ....................................................... 16 5.1 Design for Pavement Structural Capacity ............................................................................................. 16 5.1.1 Porous Asphalt and PICP Structural Design ............................................................................ 17 5.1.2 Pervious Concrete Structural Design ...................................................................................... 19 5.2 Hydrologic Design of Permeable Shoulders ......................................................................................... 21 5.2.1 General Hydrologic Analysis Framework ................................................................................ 24 5.2.2 Design Hydrologic Calculation Framework for Simple Volumetric Sizing Approaches (Presumptive Sizing) ................................................................................................................ 25 5.2.3 Design Hydrologic Calculation Framework for Design Event Hydrograph and Continuous Simulation Sizing Approaches (Performance Based Sizing) .................................................... 26 5.3 Design for Cold Climate Frost Considerations ...................................................................................... 33 5.4 Balancing Structural and Hydrological Designs .................................................................................... 33 6. Permeable Shoulder Use and Configurations ................................................................................. 34 6.1 Conceptual Designs .............................................................................................................................. 35 7. Detailed Design Element Guidance and Discussion ........................................................................ 37 8. Shoulder Construction .................................................................................................................... 42 8.1 New Construction Sequencing ............................................................................................................. 43 8.2 Retrofit Construction Sequencing .......................................................................................................