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Errata Replaces page 137 Reconstruction Using a Detour When the reconstruction and resulting berm are significant, the work space takes all or most of the road surface, leaving no room for traffic to negotiate past the work activities. An agency may need to reconstruct the unpaved roadway by correcting the drainage and/or adding surface materials. With this type of work, additional equipment may be used and a large amount of material may create a large berm (12 inches or more across). This will present significant hazards for the traveling public. To improve safety for mo torists and workers, a detour may be the best TTC. Not all road users will be familiar with the local road system and some may be confused by the road closure, so signing should be used to assist users negotiating the detour. Reconstruction work space. (Source: Greg Vavra, SDLTAP). Notes: 1. Not all local agencies use route makers for their system. MUTCD Section 6F.59 states “A Street Name sign should be placed above, or the street name should be incorporated into, a DETOUR (M49) sign to indicate the name of the street being detoured.” 2. With an increase in traffic at the intersections where the detour begins and ends, a review of the usage of the STOP and YIELD signs should be completed. 3. Flashing warning lights and/or flags may be used to call attention to advance warning signs. 4. Flashing warning lights may be used on the Type 3 Barricades, which should be installed at the point where the road is closed. 5. For more complex TTC signing situations, technical assistance can be obtained from the local LTAP/TTAP or State DOT. Figure 4. TTC application for reconstruction using a detour. 7 August 2015 GRAVEL ROADS CONSTRUCTION & MAINTENANCE GUIDE Acknowledgements The original “Gravel Roads Maintenance and Design Manual” was published in 2000. It became an invaluable resource for managing gravel surfaced roads throughout the Nation and in other parts of the world. As in all fields, change occurs and resources need to be updated. This revised manual has been produced as a joint effort by the Federal Highway Administration (FHWA) and the South Dakota Local Technical Assistance Program (SDLTAP) located at South Dakota State University in Brookings, SD. New information was gathered from local agencies across the United States and from other countries. In addition, current photographs have been included to this update. Acknowledgment and appreciation is extended to the technical review committee, which helped guide this revised manual. Advisory Panel Members: Mark Sandifer – Advisory Panel Chair, FHWA Technology Partnership Programs Rafiq Darji – FHWA Florida Division Office Hamilton Duncan – FHWA West Virginia Division Office Megan Chatfiel – FHWA Western Federal Lands Division Office Jason Harrington - FHWA Office of Infrastructure Bernie Kuta – FHWA Resource Center Roger Surdahl – FHWA Central Federal Lands Division Office Deborah Vocke – FHWA Office of Public Affairs Contributors: Ken Skorseth, Program Manager, South Dakota Local Technical Assistance Program (SDLTAP) Richard Reid, Ph.D., P.E., Associate Dean, Lohr College of Engineering, Director of SDLTAP Katherine Heiberger, Program Assistant at the SD Jerome J. Lohr College of Engineering, South Dakota State University, provided support for update text and photos for the manual. Photos: Source of photos used on front and back cover, and pages 44, 56, and 86: istockphoto.com Permission to use all other photos throughout and printed herein, provided by their source: Ken Skorseth, Program Manager, SDLTAP Notice: This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The United States government assumes no liability for its contents or use thereof. This publication does not constitute a national standard, specification or regulation. ii GRAVEL ROADS CONSTRUCTION & MAINTENANCE GUIDE List of Acronyms AASHTO American Association of State Highway and Transportation Official AADT Average Annual Daily Traffic ADT Average Daily Traffic ASTM American Society of Testing and Materials DEP Department of Environmental Protection DOT Department of Transportation EPA Environmental Protection Agency FHWA Federal Highway Administration LL Liquid Limit LTAP Local Technical Assistance Program MR Resilient Modulus MUTCD Manual on Uniform Traffic Control Device PI Plasticity Index = LL – PL PCF Pounds per cubic foot PL Plastic Limit PSI Pounds per square inch ROW Right-of-Way SDLTAP South Dakota Local Technical Assistance Program TTAP Tribal Technical Assistance Program iv Gravel Roads Construction and Maintenance Guide Table of Contents Subject Page Acknowledgements..................................................................................................ii List of Acronyms .....................................................................................................iv Table of Contents .....................................................................................................v Foreward............................................................................................................... viii Introduction .............................................................................................................ix Definition of Terms ...................................................................................................x Section 1: Routine Maintenance & Rehabilitation 1 1.1 Understanding the Gravel Road Cross Section ...........................1 1.2 Routine Shaping Principles .........................................................5 1.3 Operating Speed .........................................................................6 1.4 Moldboard Angle .........................................................................6 1.5 Moldboard Pitch ..........................................................................7 1.6 Motorgrader Stability ...................................................................9 1.7 Articulation ..................................................................................9 1.8 Windrows .................................................................................10 1.9 Crown ........................................................................................ 11 1.10 Road Shoulder ..........................................................................15 1.11 High Shoulders (Secondary Ditches) ........................................17 1.12 Causes of High Shoulders ........................................................18 1.13 Recovering and Spreading on Roadway ..................................19 1.14 Breaking up Sod and Vegetation in Recovered Material ..........20 1.15 Pulling Shoulders and Removing Material .................................22 1.16 Benefit of Mowing .....................................................................23 1.17 Gravel Road Rehabilitation ......................................................24 1.18 Reshaping Surface and Shoulder .............................................25 1.19 Reshaping Entire Cross Section ...............................................26 1.20 Erosion Control .........................................................................27 1.21 Areas of Crown .........................................................................28 1.22 Dealing with Corrugation ...........................................................28 1.23 Intersections ..............................................................................31 1.24 Intersection with Paved Roads .................................................32 1.25 Bridge Approaches ....................................................................33 1.26 Superelevation in Curves ..........................................................34 1.27 Rail Crossings ...........................................................................35 1.28 Driveways .................................................................................36 1.29 Cattle Guards ............................................................................37 1.30 Soft and Weak Subgrades .........................................................38 Section 2: Drainage 45 2.1 Introduction........................................................................45 2.2 Ditches .............................................................................48 2.3 Culverts and Bridges ........................................................50 2.4 Underdrains ......................................................................54 Gravel Roads Construction and Maintenance Guide v Table of Contents Subject Page Section III: Surface Gravel 57 3.1 What is Good Gravel? .................................................................57 3.2 Difference in Surface Gravel and Other Uses ..............................58 3.3 Good Gradation ...........................................................................58 3.4 Benefit of Crushing ......................................................................59 3.5 Recycled Asphalt .........................................................................59 3.6 The Benefit of Testing Aggregates ...............................................60 3.7 Reasons for Testing ......................................................................62 3.8 Sampling ......................................................................................62 3.9 Sieve Analysis ..............................................................................62 3.10 Fines and Plasticity