Design and Operation of Ice Roads
i
Design and Operation of
Ice Roads
February 1, 2023
DESIGN AND OPERATION OF ICE ROADS
by
Steven Daly, PhD PE D.WRE
Piermont, NH
Billy Connor, P.E.
University of Alaska Fairbanks, Institute of Northern Engineering
Jessica Garron, PhD,
International Arctic Research Center, University of Alaska Fairbanks
Svetlana Stuefer, PhD,
Department of Civil, Geological, and Environmental Engineering, University of
Alaska Fairbanks
Nathan Belz, PhD,
Department of Civil, Geological, and Environmental Engineering, University of
Alaska Fairbanks
Kevin Bjella, MSc, P.E.,
US Army Corps of Engineers - Cold Regions Research and Engineering
Laboratory, Fairbanks, Alaska
for
Arctic Infrastructure Development Center
University of Alaska Fairbanks
ELIF Suite 240, 1764 Tanana Drive
Fairbanks, AK 99775-5910
Sponsored by the U.S. Department of Transportation,
Federal Highway Administration
Design and Operation of Ice Roads
i
DISCLAIMER
The contents of this report reflect the views of the authors, who are responsible for the facts and the
accuracy of the information presented herein. This document is disseminated under the sponsorship of
the University of Alaska Fairbanks, in the interest of information exchange. FHWA and the University of
Alaska accept no liability for the content or use of this manual.
ACKNOWLEDGEMENTS
The authors of this report would like to acknowledge support from the following organizations and
individuals. Amit Armstrong, Ph.D, P.E., who provided oversight of the project on behalf of the Federal
Highway Administration. We appreciate his guidance and patience as developed the manual. The
Technical Advisory Group consisting of Adam Larsen (FHWA), Tod Brockmann (FHWA), Spyros Beltaos
(Canada), Miles Brookes (FHWA), Paul Barratte (NRC) who provided through reviews of all work
products throughout the project. Their input provided the team with numerous suggestions which have
been incorporated into this document. We especially appreciate the assistance provided by Mark Leary
(Napaimute). Mark’s experience constructing and maintaining the Bethel Ice Road proved invaluable as
we developed the manual. He was always available to help ground the contents of this manual.
ii
ATECHNICAL REPORT DOCUMENTATION PAGE
1. Report No.
2. Government Accession No.
3. Recipient’s Catalog No.
INE/AIDC 23.01
4. Title and Subtitle
5. Report Date
Design and Operation of Ice Roads
December 21, 2022
6. Performing Organization Code
7. Author(s) and Affiliations
8. Performing Organization Report No.
Steven Daley), Billy Connor, Jessica Garron, Svetlana Stuefer, Nathan Belz -University of Alaska
Fairbanks
Kevin Bjella, US Army Corps of Engineers/Cold Regions Research and Engineering Laboratory
INE/AIDC 23.01
9. Performing Organization Name and Address
10. Work Unit No. (TRAIS)
Center for Safety Equity in Transportation
ELIF Building Room 240, 1760 Tanana Drive
Fairbanks, AK 99775-5910
11. Contract or Grant No.
G00013644
12. Sponsoring Organization Name and Address
13. Type of Report and Period Covered
United States Department of Transportation
Federal Highway Administration
14. Sponsoring Agency Code
69056720C-000029
15. Supplementary Notes
Report uploaded to: Scholarworks.alaska.edu
16. Abstract
This manual provides for the safe and efficient design, construction, maintenance, and operation of ice roads over freshwater. As such,
it provides the parties responsible for the ice road guidelines for ensuring the safe operation of the ice road including route selection,
minimum ice thicknesses, repair strategies, maximum vehicle weights and speed, and proper signage. The information provided in the
manual represents best practices compiled from existing literature and from those who have experience working on ice roads. While
every scenario cannot be foreseen, the information contained in this manual should provide sufficient knowledge to extrapolate safe
solutions which are not explicitly covered here.
17. Key Words
18. Distribution Statement
Ice Roads, River Ice, Lake Ice
19. Security Classification (of this report)
20. Security Classification (of this page)
21. No. of Pages
22. Price
Unclassified.
Unclassified.
89
N/A
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized.
Design and Operation of Ice Roads
iii
SI* (MODERN METRIC) CONVERSION FACTORS
iv
TABLE OF CONTENTS
Disclaimer ............................................................................................................ i
Technical Report Documentation Page ............................................................... ii
SI* (Modern Metric) Conversion Factors ............................................................ iii
Table of Contents ............................................................................................... iv
List of Figures ..................................................................................................... ix
List of Tables ....................................................................................................... x
Executive Summary ............................................................................................ 1
Chapter 1. Introduction ................................................................................ 1.1
1.1 Purpose ...................................................................................................................................... 1.1
1.2 Background ................................................................................................................................ 1.1
1.3 Organization of the Manual ....................................................................................................... 1.2
1.4 Limitations.................................................................................................................................. 1.2
1.5 Safety Considerations ................................................................................................................ 1.2
Chapter 2. Ice Roads Framework .................................................................. 2.1
2.1 Introduction ............................................................................................................................... 2.1
2.2 Ice Road Phases .......................................................................................................................... 2.1
2.3 Pre-Season ................................................................................................................................. 2.3
2.3.1 Route Planning ................................................................................................................... 2.3
2.3.2 Ice Road Risk Management ................................................................................................ 2.3
2.3.3 Signage Requirements ....................................................................................................... 2.3
2.3.4 Equipment Requirements .................................................................................................. 2.3
2.4 Pre-Construction ........................................................................................................................ 2.3
2.4.1 Route Planning ................................................................................................................... 2.3
2.4.2 Surveying ............................................................................................................................ 2.3
2.5 Construction ............................................................................................................................... 2.4
2.5.1 Preparing Travel Lanes ....................................................................................................... 2.4
2.5.2 Increasing the Ice Strength ................................................................................................ 2.4
2.5.3 Surveying ............................................................................................................................ 2.4
2.5.4 Signage ............................................................................................................................... 2.4
2.6 Ice Road Operation .................................................................................................................... 2.4
2.6.1 Vehicle Control ................................................................................................................... 2.4
2.6.2 Monitoring. ........................................................................................................................ 2.4
2.6.3 Maintenance. ..................................................................................................................... 2.5
2.7 End of Season ............................................................................................................................. 2.5
Chapter 3. Ice Roads Background ................................................................. 3.1
3.1 Introduction ............................................................................................................................... 3.1
3.2 Bearing Capacity ........................................................................................................................ 3.1
3.3 Flexural Rigidity .......................................................................................................................... 3.1
3.4 Flexural Strength ........................................................................................................................ 3.2
Design and Operation of Ice Roads
v
3.5 Stationary loads vs. Moving loads.............................................................................................. 3.2
3.6 Creep .......................................................................................................................................... 3.3
3.7 Progressive ice cover failure ...................................................................................................... 3.4
3.8 Gold’s Formula ........................................................................................................................... 3.4
3.9 Ice Types..................................................................................................................................... 3.5
3.9.1 Fine grained ice .................................................................................................................. 3.5
3.9.2 Columnar Ice ...................................................................................................................... 3.6
3.9.3 Snow Ice ............................................................................................................................. 3.6
3.9.4 Aufeis ................................................................................................................................. 3.7
3.9.5 Multiple ice types in the ice column .................................................................................. 3.7
Chapter 4. Ice Road Hazards ......................................................................... 4.1
4.1 Introduction ............................................................................................................................... 4.1
4.2 Crack Types ................................................................................................................................ 4.1
4.3 Causes of Crack Formation ........................................................................................................ 4.1
4.3.1 Vehicle induced .................................................................................................................. 4.1
4.3.1.1 Excessive loads ........................................................................................................... 4.1
4.3.1.2 Moving Loads ............................................................................................................. 4.2
4.3.1.3 Multiple Loads ............................................................................................................ 4.2
4.3.1.4 Frequent Loads........................................................................................................... 4.2
4.3.1.5 Long-Term Loads ........................................................................................................ 4.2
4.3.2 Ice Road Layout .................................................................................................................. 4.2
4.3.3 Environment Induced Cracks ............................................................................................. 4.3
4.3.3.1 Thermally Induced Cracks .......................................................................................... 4.3
4.3.3.2 Pressure Ridges .......................................................................................................... 4.3
4.3.3.3 Water Level Changes .................................................................................................. 4.3
4.4 Blowing Snow ............................................................................................................................. 4.3
4.5 Warming Periods ........................................................................................................................ 4.4
4.6 End of Season ............................................................................................................................. 4.4
Chapter 5. Ice Road Design ........................................................................... 5.1
5.1 Introduction ............................................................................................................................... 5.1
5.2 Route Selection .......................................................................................................................... 5.1
5.2.1 Previous Experience ........................................................................................................... 5.1
5.2.2 Local Climate ...................................................................................................................... 5.1
5.3 Ice Road Widths and Channel Bank Offsets. .............................................................................. 5.1
5.4 Route Selection for Ice Roads following Rivers.......................................................................... 5.2
5.4.1 Year-round River Observation. .......................................................................................... 5.3
5.4.2 Access Points. ..................................................................................................................... 5.3
5.4.3 Optimum River Channels for Ice Routes. ........................................................................... 5.3
5.4.4 Required Depth. ................................................................................................................. 5.4
vi
5.5 Route Selection for Ice Roads Crossing Lakes ............................................................................ 5.4
5.6 Route Selection for River Crossings ........................................................................................... 5.4
5.7 Required Ice Thickness ............................................................................................................... 5.5
5.7.1 Lighter Loads. ..................................................................................................................... 5.5
5.7.2 Traffic loads. ....................................................................................................................... 5.5
5.7.3 Extreme Loads. ................................................................................................................... 5.8
5.7.4 Examples of estimating required Ice thickness .................................................................. 5.8
5.8 Effective Ice Thickness ............................................................................................................. 5.10
Chapter 6. Ice Road Construction ................................................................. 6.1
6.1 Ice thickness surveying .............................................................................................................. 6.1
6.1.1 Manual ice thickness measurements ................................................................................. 6.1
6.1.2 Ground Penetrating Radar profiling ................................................................................... 6.2
6.2 Pre-Construction ........................................................................................................................ 6.4
6.2.1 Surveying Ice Thickness during Pre-Construction .............................................................. 6.4
6.2.2 Minimum Ice Thickness during Pre-Construction .............................................................. 6.4
6.2.3 Spacing of Manual Measurements during Pre-Construction ............................................. 6.5
6.3 Construction ............................................................................................................................... 6.5
6.3.1 Minimum Ice Thickness during Construction..................................................................... 6.5
6.3.2 Surveying Ice Thickness during Construction..................................................................... 6.5
6.3.3 Rough Ice Surface ............................................................................................................... 6.5
6.3.4 Increasing the Ice Cover Thickness .................................................................................... 6.6
6.3.4.1 Snow Clearing ............................................................................................................. 6.6
6.3.4.2 Flooding ...................................................................................................................... 6.7
6.4 Suggested equipment ................................................................................................................ 6.9
6.5 Safety features ......................................................................................................................... 6.10
6.5.1 Safe operations ................................................................................................................ 6.10
6.5.2 Worker safety ................................................................................................................... 6.12
6.5.3 Record Keeping ................................................................................................................ 6.12
Chapter 7. Ice Road Signage ......................................................................... 7.1
7.1 Purpose and Intent .................................................................................................................... 7.1
7.2 Design ......................................................................................................................................... 7.1
7.2.1 Signs and Plaques Sizes ...................................................................................................... 7.1
7.2.2 Visibility .............................................................................................................................. 7.1
7.3 Application ................................................................................................................................. 7.2
7.3.1 Construction Signs.............................................................................................................. 7.2
7.3.2 Entry Signs .......................................................................................................................... 7.2
7.3.3 Regulatory and Advisory Signs ........................................................................................... 7.3
Chapter 8. Ice Road Vehicle Control ............................................................. 8.1
Design and Operation of Ice Roads
vii
8.1 Introduction ............................................................................................................................... 8.1
8.2 Maximum Speed Limits .............................................................................................................. 8.1
8.3 Minimum distances between vehicles ....................................................................................... 8.3
8.4 Stationary loads ......................................................................................................................... 8.3
8.5 Load Management ..................................................................................................................... 8.3
Chapter 9. Ice Road Monitoring and Maintenance ....................................... 9.1
9.1 Monitoring ................................................................................................................................. 9.1
9.1.1 Visual Inspection ................................................................................................................ 9.1
9.2 Maintenance .............................................................................................................................. 9.3
9.2.1 Crack Repair ....................................................................................................................... 9.3
9.2.2 Snow Removal .................................................................................................................... 9.5
Chapter 10. End of Season Closure ............................................................ 10.1
10.1 Overview .................................................................................................................................. 10.1
10.2 Ice Cover Melting ..................................................................................................................... 10.1
10.3 End of Season Monitoring ........................................................................................................ 10.1
10.4 Closing Procedures ................................................................................................................... 10.2
10.4.1 When is closing required? ................................................................................................ 10.2
10.4.2 Closing Access .................................................................................................................. 10.2
10.4.3 Announcing Closure ......................................................................................................... 10.2
10.4.4 Removing Signage ............................................................................................................ 10.2
10.5 Emergency Procedures ............................................................................................................ 10.2
Chapter 11. Use of Uncrewed Aircraft Systems ......................................... 11.1
11.1 Benefits and Limitations of UAS for Monitoring Ice Roads...................................................... 11.1
11.2 Open Water .............................................................................................................................. 11.1
11.3 Freeze-Up ................................................................................................................................. 11.1
11.4 Solid Ice .................................................................................................................................... 11.2
11.5 Break-Up .................................................................................................................................. 11.2
Appendix A Uncrewed Aircraft Systems (UAS) ................................................ A-1
A.1 Types of Small UAS to Support Ice Road Monitoring ................................................................ A-1
A.2 Sensor Payloads and UAS Data Products to Support Ice Road Monitoring .............................. A-2
A.2.1 Sensor Payloads ................................................................................................................ A-2
A.2.2 UAS Data Products ............................................................................................................ A-3
A.3 UAS Flight Requirements, Operational Considerations, and Recommendations ................. A-5
A.3.1 UAS Flight Requirements .................................................................................................. A-5
A.3.1.1 UAS Crew Qualifications and Responsibilities .............................................................. A-5
A.3.1.2 Airspace ......................................................................................................................... A-6
A.3.1.3 Airspace Authorizations ............................................................................................... A-6
A.3.1.4 Part 107 Waiver Requests ............................................................................................ A-6
A.4 UAS Flight Operational Considerations ..................................................................................... A-7
A.4.1 Land Ownership ................................................................................................................ A-7
A.4.2 Weather ............................................................................................................................ A-8
viii
A.4.3 Wildlife .............................................................................................................................. A-9
A.4 Data Management ................................................................................................................ A-9
A.5 Conclusion on UAS for Ice Road Support ............................................................................ A-11
Appendix B Examples of MUTCD Signage ........................................................ B-1
B.1 Reference Location Signs ........................................................................................................... B-1
B.2 Regulatory signs ......................................................................................................................... B-1
B.3 Hazard Markers .......................................................................................................................... B-2
B.4 Closure Sign ................................................................................................................................ B-2
B.5 Supplemental Warning Plaques ................................................................................................. B-3
B.6 End of Roadway ......................................................................................................................... B-3
B.6 Channelizing Devices .................................................................................................................. B-4
B.7 Barricades .................................................................................................................................. B-4
B.8 Road Closure .............................................................................................................................. B-5
B.9 Examples of Enhanced Conspicuity for Signs ............................................................................. B-5
Appendix C References .................................................................................... C-1
Design and Operation of Ice Roads
ix
LIST OF FIGURES
Figure 3.1 Cross section of the deflection bowl created by a point load on the ice (not to scale). .......... 3.1
Figure 3.2 Critical velocity as a function of water depth and ice thickness (Nevel 1970). In this figure, u
c
=
the critical velocity; g = gravity; H = water depth; and h = the ice thickness. ........................................... 3.3
Figure 3.3 Steps leading to ice cover collapse (Ashton (1986) with changes) ........................................... 3.4
Figure 3.4 Characterizing Failure Risk (Adapted from Hayley and Proskin 2008) ..................................... 3.5
Figure 3.5 Candle ice formed from columnar ice crystals ......................................................................... 3.6
Figure 4.1 Heavy snow drifts on ice roads (Image courtesy of Stan Zuray) ............................................... 4.4
Figure 5.1 Cross section of ice road (Adapted from Alberta Government 2013) ...................................... 5.2
Figure 5.2 Allowable Loads in Pounds for Effective Ice Thickness and A Values ....................................... 5.6
Figure 6.1 Hand operated and gas-powered augers. ................................................................................ 6.1
Figure 6.2 Photos showing river ice cores and coring equipment. ............................................................ 6.2
Figure 6.3 Photo of GPR system pulled by snowmachine (Photo credit T. Sullivan). ................................ 6.3
Figure 6.4 Examples of GPR surveying on the Delta River (a) and Yukon River (b) in Alaska. Top panel (a)
shows the annotated “Image” (Radargram) of the subsurface. on the Delta River, Alaska. Bottom panel
(b) shows GPR measurements on the ice road across the Yukon River near Tanana (Richards et al., 2022).
................................................................................................................................................................... 6.4
Figure 6.5 Constructing an ice road in rough ice (Image courtesy of Mark Leary, Bethel, AK) ................. 6.6
Figure 6.6 Snow removal (Image courtesy of Mark Leary, Bethel, AK) ..................................................... 6.7
Figure 6.7 Example of pumps for flooding ice surface ............................................................................... 6.9
Figure 7.1 Example of Entry Signage (Saskatchewan Ministry of Highways and Infrastructure 2009) ..... 7.3
Figure 8.1 Critical Wave Speed as a function of water depth, H, and ice thickness, h. ............................. 8.1
Figure 8.2 Stages of Ice Cover Deflection as a function of the Vehicle speed relative to the Critical Speed.
................................................................................................................................................................... 8.2
Figure 9.1 Examples of ice cover cracks. A shallow dry crack and refrozen wet cracks are shown. ......... 9.2
Figure 9.2 Assessing Ice Cracks for Maintenance (Alberta Government 2013) ......................................... 9.4
Figure 10.1 Ice Road closure sign mounted on barricade (Saskatchewan Ministry of Highways and
Infrastructure 2009) ................................................................................................................................. 10.2
Figure A.1.The electromagnetic spectrum; opranic.com ............................................................................. 3
Figure B.1 Reference Location Signs ............................................................................................................. 1
Figure B.2 Regulatory signs (Example. MUTCD (pg. 534)) ............................................................................ 1
Figure B.3 Hazard Markers (Example. MUTCD pg. 536) ............................................................................... 2
Figure B.4 Closure Sign (Example) ................................................................................................................ 2
Figure B.5 Supplemental Warning Plaques ................................................................................................... 3
Figure B.6 End of Roadway (Example. MUTCD pg. 536) ............................................................................... 3
Figure B. 7 Channelizing Devices ................................................................................................................... 4
Figure B. 8 Barricades ................................................................................................................................... 4
Figure B.9 Road Closure ................................................................................................................................ 5
Figure B.10 Examples of Enhanced Conspicuity for Signs ............................................................................. 5
x
LIST OF TABLES
Table 2.1 Ice Road Framework ................................................................................................................... 2.2
Table 5.2 Effective ice thickness requirements for lighter loads ............................................................... 5.5
Table 6.1 Snow Clearing Procedure recommended .................................................................................. 6.7
Table 6.2 Required Safety Equipment ..................................................................................................... 6.10
Table 7.1 Sign and Plaque Sizes on Low Volume Road (Example. MUTCD (2009) pg. 532) ...................... 7.2
Table 7.2 Entry Sign Information ............................................................................................................... 7.3
Table 7.3 Regulatory and Advisory Sign Information ................................................................................ 7.4
Table 8.1 Maximum Speed Limits .............................................................................................................. 8.3
Table 8.2 Minimum Distances Between Vehicles ...................................................................................... 8.3
Table 9.1 Monitoring Program ................................................................................................................... 9.1
Table 9.3 Suggested Checklist for Visual Inspection of Ice Sheet .............................................................. 9.3
Table 9.4 Maintenance Program................................................................................................................ 9.4
Table A.1 The three most common types of small UAS, primary characteristics, and sample aircraft of
that type. NOTE: Images of UAS are not to scale ..................................................................................... A-2
Table A.2 Airports Requiring Airspace Authorization ............................................................................... A-6
Table A.3 Conditions that require a Part 107 Waiver ............................................................................... A-7
Table A.3 Summary flight report information to support archiving of UAS flights ................................ A-10
Design and Operation of Ice Roads
1
EXECUTIVE SUMMARY
The primary purpose of this manual is to provide for the safe and efficient design, construction,
maintenance, and operation of an ice road. This manual has ten chapters and three appendixes.
Chapter 1. Introduction. This chapter describes the purpose, background, and the organization of the
manual. This manual does not present an in-depth development of the principles of ice mechanics.
Safety is stressed throughout the manual.
Chapter 2, Ice Road Framework. This chapter presents a framework for the design, construction, and
operation of ice roads. The framework is a series of phases (or steps) to be followed for establishing an
ice road or crossing. The phases are Pre-Season, Pre-Construction, Ice Road Operation, and End of
Season. A very brief description is provided of the main activities that occur in each Phase, and the
chapter of the manual that provides information on each activity is referenced.
Chapter 3, Ice Road Background. This chapter starts with an overview of bearing capacity. In addition to
ice thickness and quality, two factors that can impact the bearing capacity, vehicle motion and creep of
the ice cover are described. Gold’s formula for estimating the bearing capacity provides a way of
estimating the risk associated with a minimum ice thickness requirement for a specified load. Finally, the
distinct types of ice that can be encountered and how those types of ice impact the load bearing are
described.
Chapter 4, Ice Road Hazards. This chapter reviews the hazards that can affect the integrity of the ice
road and the safe operation of vehicles on the ice cover. A primary hazard to the ice cover integrity is
the formation of cracks. There are two basic types of cracks, dry cracks, and wet cracks. The causes of
cracks are described. Other hazards, including blowing snow, warming, and end of the season are
discussed.
Chapter 5, Ice Road Design. The design of ice roads starts with route selection. Steps for route selection
are then described for ice roads located on rivers, located on lakes, and for river crossings. The minimum
road widths are presented. The required ice thickness is described in terms of Ice Road Risk
Management. Ice Road Risk Management allows the ice road operators to balance the needs and
requirements of the ice road users and the resources available to the operators at an acceptable risk
level. The risk level is set by the selection of the A value for Gold’s Formula. Loads are divided into three
classes: Lighter loads, Traffic Loads, and Extreme Loads.
Chapter 6, Ice Road Construction. Ice thickness surveying is a fundamental part of Ice Road Construction
and is discussed first in this chapter. Ice road construction starts with the pre-construction phase. During
the pre-construction phase the layout of the road across lakes and along rivers is finalized, and the ice
thickness along the route is systemically surveyed and recorded. When the ice thickness is sufficient to
support construction vehicles, then the actual construction can begin. During the construction phase the
travel lanes are prepared, the ice cover is strengthened by removing the snow cover from the ice and
flooding the ice surface if necessary, and access points are developed. The required equipment is
described, along with safety features, safe operations, worker safety, and record keeping.
Chapter 7, Ice Road Signage. Winter ice road traffic signs are an important part of ice road safety. It is
required that ice road signage follows standard Manual on Uniform Traffic Control Devices (MUTCD)
standards and guidance (FHWA 2009), where applicable. Ice roads are considered Low Volume Roads as
defined by the MUTCD. Ice road signage shall be designed in accordance with the provisions contained
2
in Part 5 of the MUTCD, “Traffic Control Devices for Low-Volume Roads”, and where required, in other
applicable parts of the MUTCD. Generally, all required signage must be in place before an ice road or
crossing is open to the public. There are three categories of signage: Construction, Entry signs, and
regulatory and advisory signs.
Chapter 8, Ice Road Vehicle Control. This chapter describes the maximum speed limits, minimum
distances between vehicles, control of stationary loads, and load management for ice roads.
Chapter 9, Ice Road Monitoring and Maintenance. Monitoring the ice cover is done through visual
inspection and ice thickness surveying. The required frequency of monitoring activities is described.
Maintenance involves repairing dry and wet cracks, controlling loads, directing traffic during repairs,
modifying, replacing, or adding to signage, and other tasks required to keep the ice road in good order
and allow traffic to move. The required frequency of maintenance activities and the process of repairing
cracks are described.
Chapter 10. This chapter covers the issues that are associated with the End-Of-Season closure of the ice
road. These are ice cover melting, end-of-season monitoring, closure procedures, and emergency
procedures.
Chapter 11. Use of Uncrewed Aircraft Systems (UAS). This chapter gives an overview of how UAS may be
used to select routes and monitor the condition of the ice road.
Appendix A, Uncrewed Aircraft Systems (UAS). Small uncrewed aircraft systems (UAS) or drones can be
used in support of ice road monitoring by collecting still images and dynamic videos over target areas of
rivers, lakes, and their surrounding landscapes throughout the year. Types of UAS, their payloads, data
products, flight requirements, operation considerations, and recommendations are described.
Appendix B, Examples of MUTCD Signage. This chapter provides illustrations of MUTCD signage that is
applicable to ice road use.
Appendix C, References.
Design and Operation of Ice Roads
1.1
Introduction Design and Construction of Ice Roads
CHAPTER 1. INTRODUCTION
1.1 Purpose
The primary purpose of this manual is to provide for the safe and efficient design, construction,
maintenance, and operation of an ice road over freshwater. As such, it provides the parties responsible
for the ice road guidelines for ensuring the safe operation of the ice road including route selection,
minimum ice thicknesses, repair strategies, maximum vehicle weights and speed, and proper signage.
The information provided in the manual represents best practices compiled from existing literature and
from those who have experience working on ice roads. While every scenario cannot be foreseen, the
information contained in this manual should provide sufficient knowledge to extrapolate safe solutions
which are not explicitly covered here.
Some of the information presented in this manual is new. As such the experience base may be limited.
Such information will be clearly identified as new with limited testing.
1.2 Background
Frozen rivers and lakes have been used for travel for millennia because of the relative ease of
movement whether walking, sledding behind a team of dogs, riding on a snowmobile- or riding in a
vehicle. As man moved from walking, to sledding, and finally to motorized vehicles, the need to engineer
the ice road became increasingly important. Recent increases in traffic are causing an increased interest
in developing standards of practice in the routing, construction, maintenance, and operations of ice
roads.
While the science of ice mechanics and floating ice sheets are well established, the complexity of the
formation of ice on rivers and lakes requires the use of judgment by those who are responsible for the
ice roads. Varying ice thickness, ice strength, varying temperatures, and other parameters simply do not
lend themselves to a purely mathematical solution. Consequently, it is necessary to blend science with
experience and judgement. Rather than require ice road operators to understand the ice science,
hydrology, and the subtleties of floating ice sheets, this manual provides tables and graphics based on
that science which can be used to determine minimum ice thicknesses for the anticipated traffic stream,
to establish appropriate speeds, and other operational characteristics.
The formation of ice is highly variable due to the dependence on temperature, river stage, changing
slope of the river bottom, and precipitation. Unfortunately, those responsible for the ice road have no
influence over any of these factors. As a result, operators must wait for nature to run its course. Ice
thickness and strength may be estimated or measured which in turn can provide the information
required to allow travel over the frozen surface.
As with most engineered structures, there are inherent risks of failure. Understanding and managing
those risks must be a conscience decision. This manual uses a risk-based approach pioneered in the
Canadian Provinces. Using this approach requires an understanding of the risks involved and keeping
those risks within acceptable limits. That said, the operators must remain vigilant to ensure changing
conditions are closely monitored and appropriate action taken.
Finally, users and operators must ensure the operational parameters, especially weight and speed, are
strictly adhered to. Failure to stay within these parameters could result in the vehicle falling through the
ice, or worse result in the loss of life.
1.2
Design and Construction of Ice Roads Introduction
1.3 Organization of the Manual
The organization of the manual is intended to enhance the user’s ability to find information easily. While
it is not necessary to read the manual in the order it is written, the information is presented in the order
in which the novice reader might need the information, that is each chapter builds on the previous
chapters. Consequently, it is important that the user be familiar with the entire contents of the manual.
Rather than describing each chapter, it is suggested that the reader review the Table of Contents to get
a global understanding of the depth and breadth of the information contained here.
1.4 Limitations
An in-depth development of the principles of ice mechanics is not presented here. For those who wish
to gain a more in-depth knowledge of the fundamental relationships used in developing this manual,
please refer to the references. However, an overview of the principles required to operate an ice road is
provided so that the practitioner has a basic understanding of the performance of an ice sheet under
traffic loadings.
1.5 Safety Considerations
While safety is stressed throughout the manual, it is impossible to consider every safety scenario. It is
the responsibility of everyone, including those responsible for the operation of the ice road as well as
the user to know and adhere to the safety requirements. It is important that all safety requirements be
readily available to anyone who ventures out on the ice and that the ice conditions and user behavior be
continuously monitored. The frequency of monitoring depends on the condition of the ice, traffic
loadings and level of risk selection. In general, worse conditions along with higher risk require more
frequent monitoring.
Follow the old rule: If it looks unsafe, it probably is.
Design and Operation of Ice Roads
2.1
Ice Roads Framework Design and Construction of Ice Roads
CHAPTER 2. ICE ROADS FRAMEWORK
2.1 Introduction
This chapter presents a framework for the design, construction, and operation of ice roads. The
framework is a series of phases (or steps) to be followed for establishing an ice road or crossing. The
phases follow each other in time: The order of the phases is as follows:
Pre-Season. The Pre-Season phase covers the open water period before the rivers and/or lakes to be
used for the ice road freeze up. The main activity of the Pre-Season is planning for the ice road
construction and operation.
Pre-Construction: In the Pre-Construction phase, the route is selected, and the ice thickness is surveyed
along the route. Surveying the ice thickness during Pre-Construction can be the most dangerous period
of the winter season due to the relatively thin and unknown ice conditions.
Construction: The Construction phase begins when the ice is thick enough to allow safe transit of the
construction vehicles. Ice road construction involves setting the ice road widths, increasing the ice cover
thickness, if necessary, through snow clearing and flooding of the ice cover, and installing signage.
Ice Road Operations: During the Ice Road Operations phase the Ice Roads and crossings are opened for
public use. The three main activities during this phase are Monitoring, Maintenance, and Administration.
End of Season. During the end of season phase the public use of Ice Roads and crossings is ended,
signage is removed or modified, and barricades set up as needed.
2.2 Ice Road Phases
The Ice Road Framework is shown in Table 2.1 with the Phases shown in Column 1. Next the Ice Road
Phases are briefly described along with references to the chapters in the manual where the phases are
described.
2.2
Design and Construction of Ice Roads Ice Roads Framework
Table 2.1 Ice Road Framework
Phase
Main Activities
Tasks
Pre-Season
Planning
Route Planning
Select Operations Level
Determine Signage
Requirements
Determine Equipment
Requirements
Pre-Construction
Surveying
Manual Surveying
GPR Surveying
Route Selection
Route Selection
Access Points
Construction
Ice Road Establishment
Preparing Travel Lanes
Snow Clearing
Ice Strengthening
Surveying
Signage
Construction Signs
Entry Signs
Regulatory and Advisory Signs
Ice Road Operation
Monitoring
Visual Inspection
Surveying
Maintenance
Repairing Cracks
Traffic Control
Updating Signage
Administration
Controlling Loads and Speeds
Safety
Training
End of Season
Shutdown
Close Ice Road to Public Use
Design and Operation of Ice Roads
2.3
Ice Roads Framework Design and Construction of Ice Roads
2.3 Pre-Season
The primary activity of the Pre-Season is planning for the upcoming winter construction and operation
of the ice roads. The major tasks of the Pre-Season are route planning, selection of the operations level,
determination of the signage requirements, and determination of the equipment requirements. It would
be appropriate during the pre-season to review Chapter 3, Ice Road Background, and to be familiar with
the physical concepts that impact ice road design, construction, and operations.
2.3.1 Route Planning
Pre-season route planning lays on the basic routes and access points that will serve the needs of the
public with a recognition of certain site features that will directly influence the safety and practicality of
the proposed route. Pre-season route planning provides information on the ice road lengths, level of
effort, required material and equipment, and other important factors for the upcoming winter season.
Route planning is covered in Chapter 5 Design of Ice Roads
2.3.2 Ice Road Risk Management
Ice Road Risk Management sets the level of risk associated with use of the ice road. The level of risk is
determined by the required ice thickness for a given load level. The levels of risk are described as Low
Risk, Tolerable Risk, Moderate Risk, and Substantial Risk. The level of risk is described in Chapter 5
Design of Ice Roads. “Low Risk” is expected to be the most common level of risk used in ice road
construction and operations. At this point in the Pre-Season, the hazard controls that will be needed and
the overall resources for operating the ice road can be assessed.
2.3.3 Signage Requirements
Signs are considered an important part of safety. It is important in the pre-season to determine the
signage requirements for the ice road so that the necessary signage can be ordered and/or constructed.
Signage requirements are described in Chapter 7, Ice Road Signage.
2.3.4 Equipment Requirements
The equipment needed for ice road construction and maintenance is described in Chapter 6, Ice Road
Construction.
2.4 Pre-Construction
During the pre-construction phase the layout of the ice road across lakes and along rivers is determined,
access points are located, and the ice thickness along the route is systematically surveyed and recorded.
When the ice thickness is sufficient to support construction vehicles, then the actual construction can
begin.
2.4.1 Route Planning
The final route selection is made during the Pre-Construction phase. This includes setting the ice road
alignment and lane widths, the development of access points, and other factors. Route planning is
covered in Chapter 5 Design of Ice Roads.
2.4.2 Surveying
Surveying the ice thickness during pre-construction can be the most dangerous period of the winter
season due to the relatively thin and unknown ice conditions. Surveying can either be done manually or
using GPR. Surveying is described in Chapter 6, Ice Road Construction.
2.4
Design and Construction of Ice Roads Ice Roads Framework
2.5 Construction
During the Construction phase the Ice Road is established and Signage is installed. The Ice Road was
established by preparing travel lanes, increasing the natural ice cover strength by thickening the ice
cover through snow removal and flooding the ice surface if necessary, and developing access points. The
final step of the construction phase is the installation of signage to communicate with users. After
Construction is completed, the Operations phase begins.
2.5.1 Preparing Travel Lanes
Constructing travel lanes includes developing access points, setting the lane alignment and the lane
widths. Preparing Travel Lanes is described in Chapter 5 Design of Ice Roads.
2.5.2 Increasing the Ice Strength
There are two approaches for increasing the ice cover thickness to increase the bearing capacity of the
ice cover: clearing the snow cover from the ice road and flooding the ice cover. Increasing the ice cover
thickness is often referred to as “strengthening the ice cover.” Strengthening the ice cover is discussed
in Chapter 6, Ice Road Construction.
2.5.3 Surveying
Monitoring the ice thickness during Construction is done to meet the ice thickness required for
construction equipment and to ensure that the final thickness required for the Ice Road is achieved.
Surveying is described in Chapter 6, Ice Road Construction.
2.5.4 Signage
All required signage must be in place before an ice road or crossing is open to the public. There are three
categories of signage: Construction, Entry signs, and regulatory and advisory signs. Signage
requirements are described in Chapter 7, Ice Road Signage.
2.6 Ice Road Operation
The primary activities during Ice Road Operation phase are Vehicle Control, Monitoring, and
Maintenance. It would be appropriate to review Chapter 4, Ice Road Hazards, to be familiar with the
hazards that require vehicle controls, and the need for monitoring and maintenance.
2.6.1 Vehicle Control
Vehicle control involves setting maximum speed limits, setting minimum distances between vehicles,
prohibiting stationary loads, and load management. This can be done by posting maximum loads,
maximum speeds and minimum vehicle spacing on signage when low risk levels are adopted. (See
Chapter 5 Design of Ice Roads for a discussion of risk levels.) At higher risk levels there may need to be
active enforcement of speed limits and requirements for scale tickets for all applicable vehicles. Vehicle
controls are described in Chapter 8, Ice Road Vehicle Control.
2.6.2 Monitoring.
The frequency and intensity of monitoring is determined by the Ice Road Risk Management level that is
adopted. Monitoring the ice cover is done through visual inspection and ice thickness surveying. Visual
inspection requires personnel to travel the entire route of the ice road looking for dry cracks, wet cracks,
water on the ice cover, snow drifts, and other problems that may compromise the integrity of the ice
cover and interfere with the movement of vehicles. Visual inspections are conducted at fixed intervals
determined by the risk level assumed. Records of the visual inspections should be made and archived.
Any problems encountered should be reported. Monitoring programs are described in Chapter 9, Ice
Road Monitoring and Maintenance. Ice thickness surveying can be done manually or using GPR. Manual
Design and Operation of Ice Roads
2.5
Ice Roads Framework Design and Construction of Ice Roads
surveying is acceptable at low risk levels. All survey data should be recorded and archived. Thin sections
of the ice cover should be reported. Surveying is described in Chapter 6, Ice Road Construction.
2.6.3 Maintenance.
The frequency and intensity of maintenance is determined by the Ice Road Risk Management level that
is adopted. Maintenance involves repairing dry and wet cracks, controlling loads, snow removal, and
directing traffic during repairs, modifying, replacing, or adding to signage, and other tasks required to
keep the ice road in good order and allow traffic to move. Maintenance can be conducted on a ‘as
needed’ basis at low risk level. The interval of maintenance should be shortened if higher risk levels are
adopted, with daily maintenance occurring at higher, less conservative values. Maintenance programs
are described in Chapter 9, Ice Road Monitoring and Maintenance.
2.7 End of Season
End of season describes the shutdown of the ice road when the season ends. Details of the process are
given in Chapter 10, End of Season Closure. Hazards associated with End of Season are described in
Chapter 4, Ice Road Hazards. Appropriate signage is described in Chapter 7, Ice Road Signage.
Design and Operation of Ice Roads
3.1
Ice Roads Background Design and Construction of Ice Roads
CHAPTER 3. ICE ROADS BACKGROUND
3.1 Introduction
Loads allowed on an ice road must be supported by the ice cover within an acceptable level of risk.
Bearing capacity is the ability of the ice cover to support a load and is of fundamental importance to the
use of ice roads for transportation. This chapter starts with an overview of bearing capacity. Two factors
that can impact the bearing capacity, vehicle motion and creep of the ice cover are described. Gold’s
formula for estimating the bearing capacity provides a way of estimating the risk associated with a
minimum ice thickness requirement for a specified load. Finally, the distinct types of ice that can be
encountered and how those types of ice impact the load bearing are described.
3.2 Bearing Capacity
When a load is placed on an ice cover, the ice cover deflects in response to the load. The amount of
deflection is proportional to the magnitude of the load and the thickness and strength of the ice. The
ability of the ice cover to support a load is the bearing capacity of the ice cover. The cover deflects until
the water pressure on the bottom of the ice cover has increased sufficiently to balance the load, as
shown in Figure 3.1. It is the water pressure on the bottom of the ice cover that is the source of bearing
capacity. The load is supported by the water, not directly by the ice cover. The ice cover merely governs
the area over which the load is distributed. It deflects to distribute the weight of the applied load over
an area larger than the footprint of the load. The sum of the increased water pressure over the area of
the deflected shape equals the weight of the applied load. The deflection profile shown in Figure 3.1
shows the cross section of a “deflection bowl” caused by a point load on the ice. The vertical scale in the
figure is exaggerated for clarity. In typical ice road operation, the deflection caused by a load does not
exceed the freeboard of the ice cover.
Figure 3.1 Cross section of the deflection bowl created by a point load on the ice (not to scale).
3.3 Flexural Rigidity
The actual shape and size of the deflection bowl is determined by the ice cover resistance to bending.
The resistance of an ice cover to bending is known as its flexural rigidity or stiffness. The greater the
flexural rigidity of an ice cover the less it deflects and the larger the area over which the ice cover
deflects. The two basic parameters that determine flexural rigidity are the ice cover thickness and its
elastic modulus. The elastic modulus (also known as Young’s modulus) quantifies the relationship
3.2
Design and Construction of Ice Roads Ice Roads Background
between stress (σ) and strain (ε) for the ice cover (see Eq. 1). It takes a lot of stress to strain (compress
or extend) competent freshwater ice. A typical value of the elastic modulus (E) of ice for relatively small
strain levels is around 1.2 million psi (Ashton 1986). Because it is difficult to measure the elastic modulus
of ice in the field, it is rarely done. The value of the elastic modulus for freshwater ice can be assumed
with fair accuracy if the ice cover is competent and of decent quality. (This will be discussed further in
Chapter 3,) This leaves ice thickness as the primary determiner of the flexural rigidity of the ice cover. As
a result, the only field measurements used in practice to estimate the bearing capacity of competent,
decent quality, freshwater ice is the ice thickness.
=
= 1,000,000 (Eq. 1)
3.4 Flexural Strength
Deflection of the ice cover creates both compressive and bending stresses in the ice cover. The flexural
strength of the ice cover is defined as the bending stress (tensile stress) at which the first crack forms.
This occurs at the bottom surface of the ice cover, where tensile strain is maximum and ice temperature
is at 0°C. For a given load, the greater the flexural rigidity of the ice cover, the lower the deflection, the
lower the bending stress, and the less likely a crack is formed.
Ice is 7-8 times as strong in compression as it is in tension. Note from Figure 3.1 that during deflection
from a load, the top of the ice cover is in compression and the bottom of the cover is in tension. The
compressive strength of the ice is often referred to as the crushing strength. The compressive strength
of ice is between 725 and 3600 psi while the tensile strength of is between 100 and 450 psi (Ashton
1986). Consequently, the ice roads rarely fail due to crushing.
3.5 Stationary loads vs. Moving loads
The deflection bowl created by a vehicle moves with the vehicle (see Figure 3.1). As it moves, the
deflection bowl pushes the underlying water aside in a manner comparable to a shallow draft boat. The
interaction with the underlying water and the properties of the ice cover both combine to modify the
maximum deflection and the shape of the deflection bowl compared to a stationary load. The influence
of the water and ice properties changes as the vehicle speed increases. A key point is the existence of
critical speed, so called because at this speed “a phenomenon similar to resonance occurs and ice sheet
deflection and stresses are amplified” (Ashton 1986). Field measurements show that at low speeds, the
deflection bowl maintains its symmetric shape around the vehicle and there is minor impact from the
fluid motion created by the deflection. As the vehicle speed increases the deflection bowl becomes
deeper and narrower, and the rim around the bowl rises. At critical speed, the maximum ice cover
deflection is roughly two times the deflection that occurs when the vehicle is stationary. At high speeds,
140% of the critical speed or more, the ice cover deflection for a moving vehicle is less than the
deflection for a stationary vehicle and the vehicle assumes a position approximately half-way up the
forward slope of the deflection bowl. In effect, the vehicle is climbing up onto the wave being formed
beneath the ice sheet much like a boat getting on step. Unfortunately, the stresses that occur as the
vehicle reaches critical speed will likely result in failure of the ice.
It is difficult to estimate critical speed because it depends on the water depth, and the thickness and
material properties of the ice cover as shown in Figure 3.2.The critical speed is controlled by the water
depth in shallow water, roughly twenty feet deep or less, and by the thickness and material properties
of the ice cover in deep water. In deep water there is usually little or no additional risk for vehicles that
match or exceed the critical speed. The chief risks happen when a vehicle enters shallow water at
excessive speed. Critical speed drops rapidly as the water depth decreases and vehicles can
Design and Operation of Ice Roads
3.3
Ice Roads Background Design and Construction of Ice Roads
inadvertently exceed critical speed even if their speed is unchanging. This is an especially important
consideration at access points to and from the ice cover where the water depth is always shallow.
Figure 3.2 Critical velocity as a function of water depth and ice thickness (Nevel 1970). In this figure, u
c
=
the critical velocity; g = gravity; H = water depth; and h = the ice thickness.
The discussion above clearly shows speed has a dramatic impact on the safety of ice travel. Speed limits
will be discussed further in Chapter 8, Ice Road Vehicle Control.
3.6 Creep
As described above, when a load is placed on an ice cover, the ice cover deflects immediately in
response to the load, and the deflection is proportional to the magnitude of the load. This deflection
and support of the load defines the bearing capacity of the ice cover. However, it is observed that the
immediate deflection is often followed by a gradual increase in the magnitude of the deflection over
time. The additional deflection is known as creep. Creep begins almost immediately when a load is
placed, for example “by vehicles parked for more than a few minutes” (Saskatchewan Ministry of
Highways and Infrastructure, 2009). In effect, creep reduces the bearing capacity of the ice cover with
time. If the load is close to or at the maximum bearing capacity of the ice cover, creep can lead to an
eventual failure and breakthrough of the ice cover. The occurrence of creep requires that stationary (or
long-term) loads placed on the ice must be treated differently than moving loads.
3.4
Design and Construction of Ice Roads Ice Roads Background
3.7 Progressive ice cover failure
The process of ice cover failure under loading occurs through the formation of cracks as the ice cover
deflection increases with time. In most cases, the increase in deflection is caused by creep. The pattern
of crack formation with time is shown in Figure 3.3. The location of the load is shown in Figure 3.3 by the
black circle. The plan view of the cracks is shown and the deflection bowl due to the load is not
indicated. The progression starts on the left with the formation of one or two radial cracks. The radial
cracks occur when the bending stress of the ice cover immediately at the load exceeds the flexural
strength of the ice cover. The number of radial cracks increases as the deflection increases. Radial cracks
can propagate outward from the load for a considerable distance. Eventually the radial cracks form ice
wedges surrounding the load. While the presence of radial cracks reduces the bearing capacity of the ice
cover, the wedges can still support some load. As the deflection continues to increase, successive
circumferential cracks form. Each new circumferential crack forms at a smaller radius than the previous
cracks. Breakthrough occurs along the innermost circumferential crack, typically located several ice
thicknesses away from the load. Breakthrough leaves a failure hole in the ice cover. In many cases,
water seeps through the cracks and partially floods the deflection bowl prior to the breakthrough.
Figure 3.3 Steps leading to ice cover collapse (Ashton (1986) with changes)
As shown in Figure 3.3, there are a series of steps before final breakthrough, with the ice cover
becoming more unsafe with each step. A valid question is at what step does ice cover failure occur? The
first crack criterion was developed to address this question. Rather than select one step of this process
and declare that the ice cover has failed at that step, the first crack criterion prevents the very first crack
from occurring. Limiting the load on the cover limits the tensile stress and prevents the first radial cracks
from forming.
3.8 Gold’s Formula
Gold (1971) developed an approach for estimating allowable loads has found wide acceptance and
application. This approach, known as “Gold’s Formula,” is specifically for short-term moving loads on the
ice where creep is not an issue, and the vehicle speed does not influence the bearing capacity. Gold’s
Formula is an estimation of the allowable load for a given ice thickness and maximum allowable flexible
strength:
2
P Ah=
(Eq. 2)
where P = the magnitude of the load, A = a coefficient that is proportional to the allowed flexural
strength, and h = the ice thickness. Note that in Equation 2 the units of the load, P, is pounds force (lbf);
the units of the ice thickness, h, is inches (in); and the resulting units of A are lbf in
-2
. Rather than
estimate A based on a formula, Gold selected an empirical value for A based on field observations. He
collected dozens of observations of loads supported by ice covers and noted whether the ice cover had
failed. This provided a range of A values and a range likelihoods of ice failure.
Design and Operation of Ice Roads
3.5
Ice Roads Background Design and Construction of Ice Roads
The selection of an A value sets an allowable load for a given ice thickness, and it sets a level of risk in
using the ice road for transportation. In fact, A is sometimes described as “a risk factor that determines
the likelihood of failure” (IHSA 2014). The level of risk increases with increasing A values. The limits of A
suggested by Gold (1971) can be placed in a “commonly used risk paradigm,” as shown in Figure 3.4. In
this figure, risk of failure is shown as extending from the category of “Very Unlikely” through the
category “Very Likely.” The limits of “Normal Operation” extend from A = 50 to A = 100 based on the
observations of Gold and ice road usage in Canada. Note that the risk of failure over the range of Normal
Operation is labeled “Possible.” Operation of an ice road with an A value above 50 must balance the
“level or risk with operational controls.”
Figure 3.4 Characterizing Failure Risk (Adapted from Hayley and Proskin 2008)
3.9 Ice Types
Every ice cover is composed of myriads of individual ice crystals that are frozen into a continuous mass
of solid ice or are deposited under the cover as a mixture of ice crystals and liquid water. It is only the
completely solid ice portion of the ice cover that can provide bearing capacity necessary to allow the ice
cover to be used for transportation. The ice type is a product of the formation process that created the
ice cover. The ice type is identified by the size, shape, and orientation of ice crystals within the solid ice.
The three ice types that have the most application to ice roads are fine grained ice, columnar ice, and
snow ice.
3.9.1 Fine grained ice
Fine grained ice is derived from frazil ice. It is formed when the water between the frazil crystals freezes
to form solid ice. It is called “fine-grained” in reference to the small size of the individual crystals,
generally in the range of 0.04 - 0.20 inches (1-5 mm). The crystals are randomly oriented. In general,
fine-grained ice forms strong, competent ice covers. It tends to be resistant to decay caused by the
3.6
Design and Construction of Ice Roads Ice Roads Background
absorption of sunlight within the cover. It is quite common to find ice covers composed of fine-grained
ice in flowing rivers. Typically, fine-grained ice is not found in lakes unless turbulence was induced in the
surface layer of the lake by winds at the time of freeze up. The fine-grained ice will be a relatively thin
layer at or near the surface of the ice cover in a lake.
3.9.2 Columnar Ice
Columnar ice (also known as congelation ice), forms due to heat transfer from the bottom of the ice
cover to the atmosphere above. (Figure 3.5) It is also called blue or black ice. The ice crystals comprising
columnar ice tend to be much longer than wide – hence the name columnar, and the long axis of the
crystals tends to form vertically in parallel with the heat flow direction. The diameter of columnar ice
increases as the ice cover grows downward – and can reach one inch or more. In general, columnar ice
forms strong, competent ice covers. Columnar ice may include air bubbles. The air bubbles form during
periods of rapid thermal growth and are incorporated into the ice cover. Often the air bubbles will be in
layers corresponding to the thickness of the ice when the ice growth was rapid.
Figure 3.5 Candle ice formed from columnar ice crystals
3.9.3 Snow Ice
Snow ice is formed when an ice cover covered with snow floods and the saturated snow/water layer at
the ice cover surfaces freezes. It is also called white ice. The size of snow ice crystals ranges from less
than 1 mm to 5 mm, the shape is round to angular, and the grains are equiaxed with a random crystal
orientation. When snow ice forms air is usually trapped in the ice as small bubbles. This gives snow ice
its whitish appearance. The density of snow ice is less than that of fine-grained ice or columnar ice and
can vary from 90%-98% of the density of pure ice. Snow ice strength is assumed to be half the strength
of clear ice. Consequently, the equivalent thickness of snow ice is assumed to be one half the thickness
of clear ice, i.e., one inch of snow ice equals one-half inch of clear ice.
Design and Operation of Ice Roads
3.7
Ice Roads Background Design and Construction of Ice Roads
3.9.4 Aufeis
Aufeis (also called overflow or icing) forms when the water is forced to the top of the ice sheet through
cracks due to hydraulic pressure forming successive layers of ice. The ice can be several feet thick and
may create aufeis which cover the entire width of the river valley. This form of ice tends to be quite
strong. However, aufeis may create other dangers including thin sheets of water on the ice which create
slippery conditions or pressure domes due to the hydraulic pressures. The use of aufeis for ice roads is
not discussed in this manual.
3.9.5 Multiple ice types in the ice column
The literature debates the impact of ice columns which contain multiple types of ice. While the
formation of the types of ice above provides insight into the flexural strength of the ice there are but
two types of ice of interest, clear ice and white or snow ice. Clear ice is fine grained ice, or columnar ice
which is generally quite strong. Snow ice is formed when the snow on the top of the ice is flooded and
freezes. Because snow ice contains a high air content it tends to have less strength than clear ice
Referring to Figure 3.1, the bottom portion of the ice beneath the load is in tension while the upper
portion of the ice is in compression. Since snow ice is generally at the top of the slab, it is in compression
while the clear ice is in tension. As stated earlier, the tensile strength of ice is much smaller than the
compressive strength. Consequently, it is unlikely that the compressive strength of the snow ice will be
exceeded.
Design and Operation of Ice Roads
4.1
Ice Road Hazards Design and Construction of Ice Roads
CHAPTER 4. ICE ROAD HAZARDS
4.1 Introduction
This chapter reviews the hazards that can affect the integrity of the ice road and the safe operation of
vehicles on the ice cover. A primary hazard to the ice cover integrity is the formation of cracks. There are
two basic types of cracks, dry cracks, and wet cracks. The causes of cracks are described. Vehicles
traveling on the ice cover can cause cracks to form, and the many ways that vehicles can induce crack
formation are presented. Cracks can also form due to the layout of the road itself with thickened ice in
the road and the placement of snowbanks to either side. Finally, cracks can form due to conditions of
the ice road environment, such as rapid changes in air temperature, winds, and changes in water level.
Various vehicle controls for reducing or preventing crack formation, such as speed limits, vehicle
spacing, prohibiting stationary loads, and load control are reviewed. Finally, other hazards, including
blowing snow, warming, and end of the season are discussed.
4.2 Crack Types
Cracks form in the ice cover when stress fractures the ice cover. There are basically two types of cracks
that are of interest: dry cracks and wet cracks. Generally, dry cracks that do not penetrate deeply into
the ice cover are not considered an immediate problem while dry cracks that extend through more than
50% of the ice cover thickness may need immediate attention. Remediation of the cracks is discussed in
Chapter 9. The water in wet cracks indicates that the cracks extend to the bottom of the ice cover. Wet
cracks that extend in plan for more than several feet reduce the bearing capacity of the ice cover.
Calculations show that the bearing capacity of the ice cover is reduced by 50% (Ashton 1986) by the
presence of wet cracks. Areas with wet cracks in the roads are a definite hazard and should be dealt
with immediately,
4.3 Causes of Crack Formation
Causes of crack formation fall into three broad categories. These are cracks that are vehicle induced,
cracks that result from the ice road layout, and cracks that are caused by the environment.
4.3.1 Vehicle induced
4.3.1.1 Excessive loads
A load that exceeds the first crack criterion is excessive. Overloading the ice cover leads to three stages
of cracking, as shown in Figure 3.3. The first stage is the formation of radial cracks. Radial cracks are a
warning that the ice cover is overloaded, and the load should be removed immediately. The second
stage is the formation of circumferential cracks. Circumferential cracks are a warning that the load is
about to break through the ice and personnel should be evacuated from the loaded area. The final stage
is the formation of pie-shaped wedges that indicate that the ice cover has failed.
At this point the load can break through at any moment. The time from first loading to complete
breakthrough can vary depending on the load, the bearing capacity of the ice sheet, and the time the
load remains at one location on the ice. If the load is only slightly larger than the bearing capacity, the
first crack will happen, but it may take a relatively long time for breakthrough to occur. If the load is
much greater than the bearing capacity, breakthrough may occur immediately, leaving personnel little
time to evacuate.
4.2
Design and Construction of Ice Roads Ice Road Hazards
4.3.1.2 Moving Loads
As discussed in Chapter 3, Ice Road Background, a load on the ice cover creates a deflection bowl that
moves with load and creates waves in the ice cover and water beneath the ice cover. The speed of the
waves is dependent on the depth of the water, the thickness of the ice cover, and the strength of the
ice. The greatest deflection and the most severe stresses occur when the vehicle moves at the critical
speed. At this speed “a phenomenon similar to resonance occurs and ice sheet deflection and stresses
are amplified” (Ashton 1986). In deep water, greater than about 20 feet, the critical speed will be much
greater than the vehicle speed and the vehicle moves without inducing excessive stresses in the ice
sheet. However, when the water depth beneath the ice cover is shallow, for example, if the ice road
passes over sandbars or shoals, or when the vehicle is near an access point, the critical speed will be
much less, and it is more likely that the vehicle will match the critical speed. The formation of cracks is
much more likely when the vehicle travels at the critical speed on an ice cover in shallow water. In
addition, the waves created by moving loads can reflect from the shoreline. Reflected waves are
greatest when a vehicle approaches a shoreline at a right angle. This reflected pattern can be critical
when the vehicle weight is close to the load-bearing limit of the ice. Ultimately, this could lead to what is
called a ‘blowout,’ induced by the pressure exerted by the water onto the ice cover.
Maximum speed limits are presented in Chapter 8, Ice Road Vehicle Control.
4.3.1.3 Multiple Loads
When two or more vehicles approach each other, the overall deflection bowl created by all vehicles is
the sum, at every point of the ice cover, of the deflection bowl created by each vehicle. In the same
manner, the stress in the ice cover created by all the vehicles is the sum, at every point of the ice cover,
of the stresses created by each vehicle. Minimum distances between vehicles and equipment are
required to prevent large stresses in the ice cover. If two vehicles are moving in the same direction, they
should maintain a minimum distance and the rear vehicle should not attempt to pass the forward
vehicle. If two vehicles are approaching each other they should minimize their speed when passing.
Minimum vehicle spacings are presented in Chapter 8, Ice Road Vehicle Control.
4.3.1.4 Frequent Loads
Frequently repeated loadings will cause damage such as rutting, potholes, and cracking. Gold (1971)
reported that the “quality of the ice cover can … deteriorate because of fatigue.” There are no
quantitative observations relating frequency of loading to ice cover deterioration.
4.3.1.5 Long-Term Loads
The ice cover under any stationary load will creep. Creep begins almost immediately when a load is
placed, for example “by vehicles parked for more than a few minutes” (Saskatchewan Ministry of
Highways and Infrastructure 2009). The time required for a stationary load to be considered a long-term
load varies from a few minutes to 6 hours. If the deflection under the load exceeds the freeboard of the
ice cover, the ice surface will flood, and the bearing capacity of the ice cover will be compromised. If the
load is close to or at the bearing capacity of the ice cover, creep can lead to the formation of radial and
circumferential cracks with time, and breakthrough can result.
Prohibitions against stationary loads on ice roads are presented in Chapter 8, Ice Road Vehicle Control.
4.3.2 Ice Road Layout
Stresses caused by the layout of the ice road, with thickened ice in the road itself and bounded by
snowbanks on either side, can lead to the formation of “longitudinal” cracks in the ice cover. They are
referred to as longitudinal cracks because they run parallel to the long dimension of the road. The
Design and Operation of Ice Roads
4.3
Ice Road Hazards Design and Construction of Ice Roads
thicker ice in the cleared lane rises above the ice that is depressed beneath the heavy snowbanks. This
causes an upward bending of the ice cover that reaches a maximum in the middle of the cleared lane.
When the bending becomes severe enough, cracks form on the surface of the ice to relieve the stresses.
In most cases, the cracks do not extend deep enough to create a breakthrough hazard. Longitudinal
cracks can occur under snowbanks built along the edge of the road during snow clearing. The
snowbanks act as a heavy long-term load causing the ice cover to creep beneath them. The snow also
insulates the ice from the frigid air above so that the ice under the snowbank tends to be thinner than
the ice in the ice road. These cracks extend upward from the bottom of the ice cover. Some of the cracks
may extend completely through the ice cover creating wet cracks.
4.3.3 Environment Induced Cracks
Three significant environmental causes of cracks in the ice cover are changes in the air temperature
(thermally induced cracks), the stress of wind blowing across the ice (pressure ridges), and water level
changes.
4.3.3.1 Thermally Induced Cracks
Abrupt decreases in air temperature can cause cracks to form. The decrease in air temperature causes
the temperature of the top surface of the ice cover to drop. The bottom surface of the ice cover, in
contact with water, remains at a constant temperature of 32°F. The top portion of the ice contracts in
response to the change in temperature. This causes the ice cover to bend upwards, in concave fashion.
Cracks form where the bending stress exceeds the flexure strength of the ice. Often the cracks are very
regularly spaced. Most often these cracks are dry cracks. The bottom of the cracks is sealed because the
cracking does not result in separation of the pieces. If the temperature drop is large enough or there is
movement of the ice cover due to wind or water flow the crack can open and become a wet crack.
4.3.3.2 Pressure Ridges
Pressure ridges typically form in larger lakes where the thermal expansion effect and the wind stress can
accumulate over several miles. Pressure ridges form when a portion of the ice cover is driven into a
stationary portion due to thermal expansion or wind stress. Typically, pressure ridges form at weak
locations in the ice cover, weakened by the presence of thin ice or the formation of thermally induced
cracks. As in-plane compressive pressure builds, the ice cover fails, either in flexure or by buckling,
creating rubble blocks that accumulate to form the ridge structure. Pressure ridges can reach heights of
10 feet or more and extend for hundreds or thousands of feet across the lake. Pressure ridges are
significant hazards because they can be areas of reduced bearing capacity, loss of freeboard, or be
difficult to cross.
4.3.3.3 Water Level Changes
Changes in water levels can cause cracks. These usually occur in rivers, but they can occur in any body of
water that is subject to water level changes. Changes in water levels can result from tides or from the
wintertime decline in the river discharge. These cracks are almost always wet, tend to follow the
shoreline, and occur around grounded ice features. Changes in water levels may produce cracks near
and generally parallel to the shoreline where the floating ice drops or rises while the ground fast ice
remains fixed. This can create hanging ice where the ice cover can separate completely and form a
significant drop.
4.4 Blowing Snow
High winds can cause blowing snow with reduced visibility which can make it difficult to see the limits of
the safe travel way on the ice road. Extreme winds can stress the ice cover, especially in large lakes, and
lead to the formation of wet cracks and pressure ridges. In some cases, drifted snow along with snow
4.4
Design and Construction of Ice Roads Ice Road Hazards
placed in windrows along the ice road can cause thawing beneath the snow because of the insulation
provided by the snow on the ice. Regions above tree line are especially prone to blowing snow, snow
drifting across ice roads (Figure 4.1), and poor visibility due to whiteouts. Enhanced marking of the road
edges can improve visibility. Ice road operators should make regular checks of the weather to identify
potential storms and whiteout conditions in advance. Road closures during these periods may be
necessary. Finally, individual drivers should be equipped with appropriate survival equipment if they are
stranded for an extended period of time in whiteout conditions.
Figure 4.1 Heavy snow drifts on ice roads (Image courtesy of Stan Zuray)
4.5 Warming Periods
If the air temperature remains less than 32°F, the ice temperature should remain below freezing. Heat
resulting from penetration of solar radiation into the ice cover can be relatively efficiently transferred to
the frigid air above to keep the ice cover cold and strong. However, once the air temperatures rise
above 32°F heat transfer from the cover is suppressed by the stability of the atmosphere. At this point,
the interior of the ice cover warms to 32°F, and penetration of solar radiation into the ice cover causes
internal deterioration. This results in a loss of structural integrity and a general weakening of the cover.
The result is a substantial reduction in the cover bearing capacity.
Warming becomes an issue when the air temperature remains above 32°F for 24-48 hours or more.
When this happens the allowable load for the minimum ice thickness currently present is reduced by
50%. The ice conditions need to be monitored for signs of decay, cracking, and water. The reduction of
the allowable load can be re-evaluated if the average air temperature falls below 32°F and remains
below for 24 hours or more, and inspection of the ice cover does not reveal any problems or cracking.
4.6 End of Season
Proper quality control and monitoring measures will extend the safe operating life of most ice roads. In
general, ice roads are forced to close at the end of the winter season due to deteriorating road surface
conditions before the integrity of the ice cover has been compromised. Surface degradation can include
the accumulation of excessive water on the surface from surface melt and softening of the upper
portion of the ice cover to a degree that prohibits travel. In late winter, the energy of the sun provides
Design and Operation of Ice Roads
4.5
Ice Road Hazards Design and Construction of Ice Roads
enough energy to melt the ice surface, even when the air temperatures remain below freezing. Dark
material on the ice cover such as sand, gravel, and dust from vehicles will reduce the surface albedo and
increase the absorption of sunlight. Maintenance at the end of the season can extend the length of the
season by scraping dark material off the ice road surface at regular intervals.
Design and Operation of Ice Roads
5.1
Ice Road Design Design and Construction of Ice Roads
CHAPTER 5. ICE ROAD DESIGN
5.1 Introduction
The design of ice roads starts with route selection. Steps for route selection are then described for ice
roads located on rivers, located on lakes, and for river crossings. The minimum road widths are
presented. The required ice thickness is described in terms of the Ice Road Risk Management. Ice Road
Risk Management allows the ice road operators to balance the needs and requirements of the ice road
users and the resources available to the operators at an acceptable risk level. The risk level is set by the
selection of the A value for Gold’s Formula. Loads are divided into three classes: Lighter loads, Traffic
Loads, and Extreme Loads.
5.2 Route Selection
Development of ice roads requires route planning and recognition of features that will influence the
safety and practicality of the proposed route. There are three different applications of ice roads
discussed in this section: ice roads over lakes, ice roads following rivers, and ice roads that cross rivers
(referred to as crossings).
5.2.1 Previous Experience
The chief benefit of constructing ice roads in the same location every year is being able to build on
previous experience by thoroughly evaluating the previous use. However, caution is advised when
considering field experience because water levels, channel locations, weather and ice conditions vary
from year to year and methods and equipment need to adapt to changing conditions.
5.2.2 Local Climate
The thickness of the ice cover and the resulting ice cover bearing capacity are determined by the
climatic conditions along the proposed routes. The primary parameters controlling ice thickness are the
daily average air temperature and the snow cover depth. Local climatic variations and year to year
variability may need to be considered if data from local weather stations are used in route selection.
Throughout the Arctic and near Arctic, warming trends associated with climate change are affecting the
function and design of infrastructure that relies on frozen conditions. In Alaska, these trends include fall
and winter air temperatures warmer than average, fewer very cold days, river break-up happening
earlier, annual precipitation increase, increase in the occurrence of freezing rain, and a shrinking snow
season, among other impacts.
5.3 Ice Road Widths and Channel Bank Offsets.
Ice road widths determine the distance perpendicular to the direction of vehicle travel where snow is
cleared (Figure 5.1). The cleared width includes the driving lanes. The driving lanes allow vehicle traffic
to simultaneously travel safely in opposite directions. The snowbanks created by snow plowing are
formed outside of the cleared width. Channel bank offset is the minimum distance from the cleared
width to the channel bank that forms the limit of the channel width at each point along the ice road. The
effective channel bank can be the two shorelines of the river, the shore of an island, or even a sandbar.
The river channel should be wide enough to accommodate the cleared width of the ice road and a bank
offset on either side (Table 5.1).
5.2
Design and Construction of Ice Roads Ice Road Design
Figure 5.1 Cross section of ice road (Adapted from Alberta Government 2013)
Table 5.1 Minimum Road Widths
Operating Vehicles
Cleared width -
Between snowbanks
Driving lanes -
Total width
Channel Bank Offsets
on each side
Light vehicle traffic
(11,000 lbs)
65 ft 32 ft 32 ft
Construction
(50,000 lbs)
82 ft 50 ft 50 ft
Super B Train
(140,000 lbs)
100 ft 65 ft 65 ft
The ice road widths and bank offsets can be adjusted at locations where the channel width is not
sufficient to accommodate the cleared width of the ice road and a bank offset on either side. However,
adjustments in widths and/or offsets may lead to reductions in the maximum loads that can be
supported by the ice road.
The ice road widths can be reduced if the travel lanes are separated, for example if each travel lane is
routed on the opposite sides of an island.
5.4 Route Selection for Ice Roads following Rivers
Route selection for ice roads following rivers is challenging for three main reasons.
Design and Operation of Ice Roads
5.3
Ice Road Design Design and Construction of Ice Roads
Variable Channel Geometry. The overall shape and layout of the river or stream can vary widely from
location to location along the length of the channel. Rivers with a single channel that is wide, deep, and
straight present the fewest problems in route selection. However, few rivers are consistently straight,
consistently deep, or even consistently wide. More often rivers meander and each bend can have a
different curvature. Associated with bends is varying channel geometry that can include shallows, sand
bars, sudden changes in depth, changes in the velocity of the water and other variations. Rivers can also
have islands, and multiple channels, and their form and layout can change from year to year. Reaches
may have several small channels, often referred to as braided rivers, which present many difficulties for
route selection that may be difficult if not impossible to overcome.
Complex Ice Formation Process. Ice cover formation in rivers is a complex process that can result in
varying ice thickness along the channel and across the channel. A stable ice cover progresses from
downstream to upstream as it forms. The ice cover initially forms from the slush ice, ice pans, and ice
floes transported downstream with the flow. Variations in the channel flow velocity caused by changes
in the channel slope, width, direction, and depth influence the ice cover formation. In high velocity
reaches a stable ice cover may not be able to form at all and the reach can remain open throughout the
winter. Once an ice cover forms, its thickness increases as the ice grows downward due to heat transfer
from the bottom of the ice cover it to the frigid air above it.
Wintertime Decline in River Discharge. The wintertime flow consists only of groundwater drainage after
the surface runoff, channel drainage, and interflow are depleted. As a result, the channel discharge
declines throughout the winter as the groundwater levels are reduced. The water surface elevation
drops as the discharge declines. This can cause the floating ice to contact the bed or nearly contact the
bed in areas near the riverbanks and in shallow areas. Ice close to or in contact with the bed can melt
due to the seepage of groundwater. Ice frozen to the banks can be suspended by the banks as the water
level decreases. Ice in contact with the bed or banks can reduce the expected bearing capacity of ice
cover. This can happen even if the ice in contact with the bed or banks is remote from the traveled lanes
of the ice road.
5.4.1 Year-round River Observation.
River observations during the open water season can provide valuable information to use in ice road
route selection, including river channel locations, estimate of water depths, and areas of bank erosion
and buildup. Take time to note the velocity of the water, any waves, falls and location of riffles.
5.4.2 Access Points.
The locations of access points onto and off the river ice cover are key factors in deciding on the ice road
route. The shoreline at the access point should be stable from hydrological, geotechnical, and
environmental perspectives. The vehicle speed becomes critical when vehicles are approaching the
shoreline at an access point. The interaction of the waves created by the moving vehicle and their
reflection from the shorelines are greatest when a vehicle approaches a shoreline at a right angle. If
possible, access points should allow vehicles to meet the shoreline at a 45° angle or less. It is critical that
drivers obey the posted speed limit when a road meets the shoreline at an access point.
5.4.3 Optimum River Channels for Ice Routes.
If possible, ice roads following rivers should use channels that allow proper ice road widths and channel
bank offsets, have the required depth, and can provide the proper conditions throughout the winter
season as the discharge declines. In general, select routes with uniform depths and water velocities.
5.4
Design and Construction of Ice Roads Ice Road Design
5.4.4 Required Depth.
The ice road route must provide for sufficient depth beneath the ice cover (the depth is measured from
the bottom of the ice cover to the bed directly below). There is no minimum water depth requirement,
however, the ice cover must not contact the channel bed within the cleared width at any time over the
course of the operating season. The ice cover may contact the channel bed and banks only at the outer
edges of the channel bank offset, if necessary. It is preferable that there is no contact in the cleared
width of the ice road and the channel bank offsets on either side at any time. The actual depth under
the ice will decrease as the season progresses due to the combined effect of an increase in the ice cover
thickness and a decrease in the water surface elevation. If the depth beneath the ice cover is shallow,
less than 20 feet, then the vehicle speed will need to be reduced to prevent problems related to the
critical speed.
5.5 Route Selection for Ice Roads Crossing Lakes
The two key factors to be considered during the planning phase when the proposed route crosses lake
ice are the access points onto and off the lake ice cover and the water depth along the route. Access
points near river and stream outlets or inlets should be avoided as the lake ice near these locations is
usually unreliable. The shoreline at the access point should be stable from hydrological, geotechnical,
and environmental perspectives.
The water depth along the route is an important consideration because the hydraulic conditions created
by moving loads can interact with sandbars and other shallows, leading to ice cracking and blowout. The
route should follow the deepest water in the lake even if this is not the shortest route. The critical
velocity increases with water depth. Consequently, over very deep water, the vehicle is usually traveling
at lower velocity than the critical velocity. The vehicle speed becomes critical near the shoreline. The
interaction of the waves created by the moving vehicle and their reflection from the shorelines are
greatest when a vehicle approaches a shoreline at a right angle. If possible, roads and vehicles should
meet the shoreline at a 45° angle. It is important that drivers obey the posted speed limit when a road
meets the shoreline at a 90° angle and when a vehicle's weight is close to the maximum load limit for
the ice.
5.6 Route Selection for River Crossings
Site selection. The best crossings have the deepest water and most uniform bottom conditions. This is
often the widest crossing site. Nearby islands, sandbars, and other features created by active erosion or
deposition can indicate channel shifting and unpredictable currents.
Variable ice thickness. The greater variability of river ice results from drifting snow, under ice currents,
frazil ice deposition, and other factors. This places stress on monitoring ice thickness and its variability. It
is recommended that river ice thickness be monitored and verified with technical aids such as Ground
Penetrating Radar (GPR) profiling along with manual measurements, and/or corings.
River bottom conditions. Sand bars and other features that determine bottom topography (bathymetry)
can affect ice cover thickness and extent. It is recommended that river bathymetry be mapped with
either manual water depth measurements or with geophysical methods (sonar or GPR).
Riverbank stability. Like lake ice access points, river access points should be stable from hydrological,
geotechnical, and environmental perspectives.
Changing water levels. As described in Chapter 3, Ice Road Background, river water levels should slowly
decline during the winter season following the freeze up period. However, dams located upstream or
Design and Operation of Ice Roads
5.5
Ice Road Design Design and Construction of Ice Roads
downstream can impact water levels at any time. Rivers connected to the ocean or to estuaries can be
impacted by tides.
5.7 Required Ice Thickness
In this section the required ice thickness is described in terms of the Ice Road Risk Management. Ice
Road Risk Management allows the ice road operators to balance the needs and requirements of the ice
road users and the resources available to the operators at an acceptable risk level. The risk level is set by
the selection of the A value for Gold’s Formula. The selection of the A value determines the maximum
load that is acceptable for the ice cover thickness. The risk levels are characterized as Low Risk,
Tolerable Risk, Moderate Risk and Substantial Risk. The frequency and intensity of ice road monitoring
and maintenance must increase with increasing A values to offset the level of risk. Ice road monitoring
and maintenance are described in Chapter 9.
There are three ranges of loads to be considered: Lighter Loads, loads less than 11,000 lbs, in which a
minimum effective ice thickness is required; Traffic Loads, greater than 11,000 lbs and less than 140,000
lbs, which cover most of the loads transported on the ice road; and Extreme Loads which are greater
than 140,000 lbs and require special analysis by a Professional Engineer with expertise in ice bearing
capacity.
5.7.1 Lighter Loads.
These are loads of less than 11,000 lbf. In these cases, there is a minimum effective ice thickness
required. The ice thickness requirements for lighter loads are listed in Table 5.2.
Table 5.2 Effective ice thickness requirements for lighter loads
Load/Situation
(Slow-moving Loads)
Estimated Weight
(lbf)
Minimum Effective Ice Thickness
(Inches)
Person walking
260
4
Snowmobiles
(machine + rider)
< 1100 7
3/4-ton 4x4 vehicles
GVW* < 11,000
15
*GVW = Gross Vehicle Weight
5.7.2 Traffic loads.
Traffic loads are moving loads on the ice. Creep is not an issue with traffic loads as explained earlier, and
the vehicle speed does not influence the bearing capacity (because it is below the critical speed). The
Traffic Loads should apply to most of the loads that the ice roads are designed to support. Traffic Loads
range from 11,000 to 142,000 lbs. The allowable loads in pounds for a given effective ice thickness and A
value is listed in and shown in Table 5.3. The required effective ice thickness for a given load and A value
is listed in Table 5.4.
5.6
Design and Construction of Ice Roads Ice Road Design
Figure 5.2 Allowable Loads in Pounds for Effective Ice Thickness and A Values
Design and Operation of Ice Roads
5.7
Ice Road Design Design and Construction of Ice Roads
Table 5.3 Allowable Loads in Pounds for Effective Ice Thickness and A Values
H = Effective Ice
Thickness (in)
A = 50
A = 57
A = 71
A = 85
Low Risk
Tolerable Risk
Moderate Risk
Substantial Risk
4
*
*
*
*
6
*
*
*
*
8
*
*
*
*
10
*
*
*
*
12
*
*
*
*
14
*
11200
13900
16700
16
12800
14600
18200
21800
18
16200
18500
23000
27500
20
20000
22800
28400
34000
22
24200
27600
34400
41100
24
28800
32800
40900
49000
26
33800
38500
48000
57500
28
39200
44700
55700
66600
30
45000
51300
63900
76500
32
51200
58400
72700
87000
34
57800
65900
82100
98300
36
64800
73900
92000
110200
38
72200
82300
102500
122700
40
80000
91200
113600
136000
42
88200
100500
125200
**
44
96800
110400
137500
**
46
105800
120600
**
**
48
115200
131300
**
**
50
125000
**
**
**
** Professional engineer required for design
* Minimum ice thickness Required (See Table 5.2)
Low Risk Allowable Load (P=lbs) Substantial Risk
5.8
Design and Construction of Ice Roads Ice Road Design
Table 5.4 Required ice thickness for a given load and corresponding risk values
P = Load (lbs)
A = 50
A = 57
A = 71
A = 85
Low Risk
Tolerable Risk
Moderate Risk
Substantial Risk
200
*
*
*
*
400
*
*
*
*
600
*
*
*
*
800
*
*
*
*
1000
*
*
*
*
5000
*
*
*
*
10000
*
*
*
*
15000
17
16
15
13
20000
20
19
17
15
30000
24
23
21
19
40000
28
26
24
22
50000
32
30
27
24
60000
35
32
29
27
70000
37
35
31
29
80000
40
37
34
31
90000
42
40
36
33
100000
45
42
38
34
110000
47
44
39
36
120000
49
46
41
38
130000
51
48
43
39
140000
53
50
44
41
150000
**
**
**
**
** Professional engineer required for design
* Minimum ice thickness Required (See Table 5.2)
5.7.3 Extreme Loads.
Extreme loads are those over 140,000 lbs. A professional engineer should provide recommendations for
required ice thickness and procedures for these loads.
5.7.4 Examples of estimating required Ice thickness
There are three ranges of loads to be considered: Lighter Loads, under 11,000 GVW, in which a
minimum effective ice thickness is required; Traffic Loads which cover most of the loads transported on
the ice road; and Extreme Loads which are greater than 140,000 lbs and require special analysis by a
Professional Engineer with expertise in ice bearing capacity.
Low Risk Req. Ice thickness (h = in) Substantial Risk
Design and Operation of Ice Roads
5.9
Ice Road Design Design and Construction of Ice Roads
A person walking on ice. This is considered a Lighter Load. The required ice thickness is taken
directly from Table 5.2 Effective ice thickness requirements for lighter loads. The required ice
thickness is 4 inches.
Pickup truck with a total load of 8000 lbs. This is considered a Lighter Load as the weight of the
vehicle is less than 11,000 GVW. The required ice thickness is taken directly from Table 5.2
Effective ice thickness requirements for lighter loads. The required ice thickness for vehicles
under 11,000 lbs GVW (Gross Vehicle Weight) is 15 inches.
Truck with 40,000 lbs GVW. This is a Traffic Load as the weight of this vehicle is greater than 11,000
GVW. The required ice thickness can be taken from Table 5.4 or calculated directly.
Table 5.4: The required ice thickness can be estimated directly from “Table 5.4 Required ice
thickness for a given load and corresponding risk values.” It is necessary to first select the risk
factor, A, which is applicable to the ice road. The results from the table are
• A value of 50, Low Risk: 28 inches of ice.
• A value of 57, Tolerable Risk: 26 inches of ice.
• A value of 71, Moderate Risk: 24 inches of ice.
• A value of 85, Substantial Risk, 22 inches of ice.
Calculated Directly: Gold’s Formula (Eq.2, Section 3.2) can be rearranged to estimate ice
thickness directly as
=
P
h
A
(Eq. 3)
where P = the magnitude of the load, A = the risk factor, and h = the ice thickness. Note that in
Equation 3 the units of the load, P, is pounds force (lbf); the units of the ice thickness, h, is
inches (in); and the resulting units of A are lbf in
-2
. In this example, P= 40000. The calculations
are rounded to the nearest whole inch. The results are
• A value of 50, Low Risk: 28.28 inches of ice, rounded to 28 inches.
• A value of 57, Tolerable Risk: 26.49 inches of ice, rounded to 26 inches.
• A value of 71, Moderate Risk: 23.74 inches of ice, rounded to 24 inches.
• A value of 85, Substantial Risk, 21.69 inches of ice, rounded to 22 inches.
5.10
Design and Construction of Ice Roads Ice Road Design
5.8 Effective Ice Thickness
The effective ice thickness describes the decent quality, well-frozen, white, and blue ice that is
measured in an ice cover. Poor quality or poorly frozen ice should not be included in the measurement
of ice thickness. Table 5.6 lists examples of ice that should be excluded from measurements.
Table 5.5 Ice Types that should be excluded from thickness calculations
Ice layer with visible water lenses with a cumulative volume greater than 10% of the total volume.
Ice layer with visible incompletely frozen frazil (slush) ice.
Ice layer that is not completely frozen to the adjoining layer.
Ice layer that has been found to have a strength less than 50% of decent quality blue ice (a
number of specialized methods are available for determining ice strength).
Ice that has wet cracks.
Design and Operation of Ice Roads
6.1
Ice Road Construction Design and Construction of Ice Roads
CHAPTER 6. ICE ROAD CONSTRUCTION
Ice thickness surveying is a fundamental part of Ice Road Construction and is discussed first in this
chapter. Ice road construction starts with the pre-construction phase. During the pre-construction phase
the layout of the road across lakes and along rivers is finalized, and the ice thickness along the route is
systemically surveyed and recorded. When the ice thickness is sufficient to support construction
vehicles, then the actual construction can begin. During the construction phase the travel lanes are
prepared, the ice cover is strengthened by removing the snow cover from the ice and flooding the ice
surface if necessary, and access points are developed. The required equipment is described, along with
safety features, safe operations, worker safety, and record keeping.
6.1 Ice thickness surveying
Systematic ice thickness surveying along the route provides the information required to allow travel
over the ice cover.
6.1.1 Manual ice thickness measurements
Manual ice measurements are made directly by personnel on the ice using augers to drill through the ice
and then measure and record the ice thickness information (Figure 6.1). The safety of the personnel on
the ice is a priority. There should be at least two surveyors on the ice at all times. The safety protocol
will vary between pre-construction, construction, and operation phases of the ice road. The safety
protocols are discussed in the respective sections of this Manual.
The simplest and most common method for measuring ice thickness is to auger holes in the ice, lower a
tape or a stick in the hole, and take a reading of ice thickness. A measuring tape with a weight attached
at the leading edge works well in holes 2-inches in diameter. A graduated rod with a right angle at the
bottom works better for holes that are larger in diameter. Sometimes, in the presence of frazil ice under
the ice cover, it can be challenging to determine the frazil and columnar ice interface. Poor quality or
poorly frozen ice should be excluded from the measurement of effective ice thickness (see Section 5.9
for descriptions of poorly frozen ice).
Figure 6.1 Hand operated and gas-powered augers.
6.2
Design and Construction of Ice Roads Ice Road Construction
If detailed description of ice column is needed, ice coring can be helpful. Ice cores are extracted by
drilling a rotating core barrel with sharp cutters at the end through the ice sheet. The ice core is then
accurately removed from the barrel and used for analysis. Total ice thickness, effective ice thickness,
and the measurement of the thickness of individual layers within the ice cover (fine grained, columnar,
and snow ice) can be derived from ice core inspection. Thin sections can also be made from the cores, to
examine the ice internal structure. It should be noted that, while ice coring provides considerable
information, it is not as fast as auguring for simply determining the ice thickness.
If ice is covered by snow, a collocated measurement of snow depth is recommended. Snow depth is
measured by vertically inserting graduated rod into the snow cover and reading associated depth
measurement. The presence of liquid water in the snow or within the ice cover should be reported.
The position of each manual ice thickness measurement is commonly determined with a hand-held
Global Positioning System (GPS). If a GPS device is not available, a marker can be placed in each hole and
position can be marked on the map.
Systematic record of date, time, GPS coordinates, snow depth, total ice thickness, and effective ice
thickness provides information to calculate allowable loads over the ice cover. Canadian guidance calls
for measurements every 33 to 100 feet on rivers, and for lakes up to 820 feet apart, away from shore,
with closer spacing near shore (
Alberta Government, 2013; Northwest Territories, 2015; Saskatchewan
Ministry of Highways and Infrastructure 2009). During early season (pre-construction and construction),
it is important to take ice thickness measurements closely together for identifying and mapping sections
of thin ice.
Figure 6.2 Photos showing river ice cores and coring equipment.
6.1.2 Ground Penetrating Radar profiling
Ground-Penetrating Radar (GPR) is a non-intrusive technique that uses radar pulses to image the
subsurface of the ice cover and, after analysis and interpretation, produce a continuous estimate of the
ice thickness. The GPR equipment consists of the radar itself, a compatible computer system, data
cables connecting the computer to the radar, and a system of deploying the radar on the ice. In ice road
Design and Operation of Ice Roads
6.3
Ice Road Construction Design and Construction of Ice Roads
applications, the GPR equipment is typically towed directly on the ice cover surface by snowmobile,
pickup truck, or another vehicle (Figure 6.3).
Figure 6.3 Photo of GPR system pulled by snowmachine (Photo credit T. Sullivan).
The GPR transmits an electromagnetic (EM) pulse of extremely short duration, which is partially
reflected from the interface between the bottom of the ice cover and the water below. The EM pulse
can also be reflected from any discontinuities within and below the ice cover. An example of the
continuous image produced by the GPR is shown in Figure 6.4. It requires a trained operator to identify
spurious reflections and arrive at an accurate estimation of the ice thickness. Snow, snowdrifts,
overflow, liquid water intrusions and air bubbles in the ice affect GPR estimate of ice thickness and
should be reported (Richards et al 2022). Manual ice thickness measurements are required to obtain
calibration data. The Saskatchewan Ministry of Highways and Infrastructure (2009) recommends
calibrating GPR “at the start of each day, after four hours of use, and whenever erratic or questionable
readings are obtained.”
During construction and operation of ice roads, GPR is often used to produce continuous estimates of
ice thickness along the length of the ice road. Several commercially available GPR systems are available
to estimate ice thickness. A typical ice profiling GPR system includes transmitting and receiving antennae
and a digital data logger, GPS, and battery. The GPR system is connected by cable or wirelessly to a
portable control unit with a monitor or laptop computer to display radargrams in the field. The antenna
central frequency of 450 or 500 MHz is commonly used for ice thickness profiling.
6.4
Design and Construction of Ice Roads Ice Road Construction
Figure 6.4 Examples of GPR surveying on the Delta River (a) and Yukon River (b) in Alaska. Top panel (a)
shows the annotated “Image” (Radargram) of the subsurface. on the Delta River, Alaska. Bottom panel
(b) shows GPR measurements on the ice road across the Yukon River near Tanana (Richards et al., 2022).
6.2 Pre-Construction
6.2.1 Surveying Ice Thickness during Pre-Construction
Surveying the ice thickness during pre-construction can be the most dangerous period of the winter
season due to the thin and unknown ice conditions. An ice cover hazard assessment must be conducted
and reviewed by field personnel prior to surveying. Suitable equipment and personal protective
equipment (PPE), listed in Table 6.2, must be available. Initial testing should be conducted by at least
two trained crew members travelling separately over the ice.
6.2.2 Minimum Ice Thickness during Pre-Construction
A conservative minimum ice thickness requirement is used during the pre-construction phase. An A
value of 57 lbf-in
2
is required for heavy equipment. A minimum thickness is required for lighter loads,
such as foot traffic, snowmobiles, or amphibious vehicles, as specified in Table 5.2
Design and Operation of Ice Roads
6.5
Ice Road Construction Design and Construction of Ice Roads
6.2.3 Spacing of Manual Measurements during Pre-Construction
The spacing of manual measurements during preconstruction should be such that significant variations
in the ice thickness are measured. Canadian guidance calls for measurements every 33 to 100 feet on
rivers, and for lakes up to 820 feet apart, away from shore, with closer spacing near shore (
Alberta
Government, 2013
; Northwest Territories, 2015; Saskatchewan Ministry of Highways and Infrastructure
2009) The ice thickness should be checked every two to three days to monitor the ice growth until
minimum ice thickness is achieved to deploy heavier pieces of equipment. If GPR is used test holes are
only required for calibration and mapping thin areas.
6.3 Construction
The construction phase involves creating ice roads with sufficient width and bearing capacity to support
the expected vehicular loads. In addition, the ice surface trafficability must allow vehicles to move at the
allowed speeds. Ice surface trafficability requires that the snow cover be removed from the ice road,
and areas of rough ice are smoothed. Snow cover removal achieves two goals. It improves trafficability
and increases bearing capacity. Bearing capacity is increased by removing the weight of the snow off of
the road and exposing the ice surface to the air resulting in increased ice cover thickness.
6.3.1 Minimum Ice Thickness during Construction
A conservative minimum ice thickness requirement is used during the construction phase. An A value of
57 lbf-in
2
is required for all equipment.
6.3.2 Surveying Ice Thickness during Construction
The ice thickness should be checked every two to three days as the ice grows, to monitor its progress
and approve the use of heavier vehicles. The most current ice profile data should be used to determine
allowable load for construction equipment. If GPR is used test holes are only required for calibration and
mapping thin areas.
6.3.3 Rough Ice Surface
In some river locations the initial ice cover formation is formed from ice floes that have overturned.
Overturning occurs at locations where the river flow velocity is fast enough to overcome the floe
stability when it is carried against a stationary ice cover. A rough ice surface must be made smooth
during ice road construction. Snowplows mounted on heavy equipment will be able to smooth rough ice
and create a relatively smooth ice road.
6.6
Design and Construction of Ice Roads Ice Road Construction
Figure 6.5 Constructing an ice road in rough ice (Image courtesy of Mark Leary, Bethel, AK)
6.3.4 Increasing the Ice Cover Thickness
There are two approaches for increasing the ice cover thickness to increase the bearing capacity of the
ice cover: clearing the snow cover off the ice road and flooding the ice cover. Each will be discussed in
turn. Increasing the ice cover thickness is often referred to as “strengthening the ice cover.”
6.3.4.1 Snow Clearing
Snow clearing involves the use of snowplows and other equipment to move snow from the ice road to
each side of the road (Figure 6.6). The snow is left in long windrows – snow piles with their long
dimension parallel to the roadway. The windrows become a long-term load on the ice cover and can
lead to crack formation directly under each windrow. It is important that sufficient room for snow
storage is created on each side of the snow road so that the height of the windrows and their resultant
load on the ice cover is minimized to the degree possible.
The snow clearing process recommended by Saskatchewan Ministry of Highways and Infrastructure
(2009) is summarized in Table 6.1:
Design and Operation of Ice Roads
6.7
Ice Road Construction Design and Construction of Ice Roads
Table 6.1 Snow Clearing Procedure recommended.
The outside limits of the ice road should be marked in advance so that the operators know the
portion of the ice cover where the ice thickness was surveyed and found to be of sufficient thickness.
Ensure that only as much road is opened as can be completed within one shift. Windrows should not
be left on the ice road area for any appreciable length of time.
If the snow is heavy the clearing should start on the outside edges and continue towards the center.
If the snow is heavy additional ice thickness surveying may have to be done so that there is more area
for snow storage.
If there is limited snow cover, clearing operations can start at the center and move to the outside
clearing limits.
Ensure that windrows are flattened out so that excess weight is not put on the ice cover
Care must be taken not to leave large windrows in the area to be cleared. Water may appear on the
ice cover if the weight of a windrow is sufficient to depress the ice cover below its freeboard. If this
occurs, it is impossible to move the windrow safely.
Figure 6.6 Snow removal (Image courtesy of Mark Leary, Bethel, AK)
6.3.4.2 Flooding
Flooding is a technique for increasing the ice thickness by pumping water onto the surface of the ice
cover. Most often the water is pumped directly on the ice cover surface, but it can also be sprayed into
6.8
Design and Construction of Ice Roads Ice Road Construction
the air to increase the heat loss from the water and the production of ice. The cover thickness is
increased when the layer of water on the ice cover surface freezes solid. This process can increase the
ice thickness faster than the process of ice growth on the bottom of the ice cover that normally occurs.
A water layer on the ice surface is exposed directly to the air above and the heat transfer rate is greater
than by heat conduction through the entire thickness of the ice cover. Over one inch of ice a day can be
grown by flooding depending on the air temperature (Masterson 2009). Ice created by flooding by
qualified personnel with good practices can generate ice that is comparable to freshwater blue ice in
strength and uniformity.
Flooding is usually accomplished with low head, high volume pumps which pump water from beneath
the ice cover directly onto its surface. The pumps should be capable of operating in very cold
temperatures, be submersible or Archimedes screw type which have no hoses to freeze and drain
readily when shut down. An example of pumps used for flooding the ice surface are shown in Figure 6.7.
The water is applied in layers of about one thick and allowed to freeze before another layer is applied. It
is important to “plug” or bank snow around each hole after flooding is completed to prevent water from
flowing back into the hole. It is best practice not to dike or confine the water but to allow it to flow
freely and achieve a tapered cross section of the road or pad. This avoids sharp transitions and the
formation of cracks at the edge of the flooded area. Snow dikes may be necessary in some cases to
prevent water from escaping and to achieve the required ice accumulation. Flooding should only be
done on bare ice or after any snow cover has been compacted. If uncompacted snow is flooded this will
produce a layer of snow ice, which is weaker and less uniform. It is exceedingly difficult to pack slush
that forms from flooded uncompacted snow and should only be attempted with extreme caution.
Design and Operation of Ice Roads
6.9
Ice Road Construction Design and Construction of Ice Roads
Figure 6.7 Example of pumps for flooding ice surface
6.4 Suggested equipment
Much of the equipment used for the construction of ice roads is the same as that used for snow removal
from roadways. This includes motor graders, one and two-way plows, front-end loaders, and smaller
support equipment such as pick-up trucks and compact track loaders (skid-steer loaders). Additionally,
water trucks play a crucial role in ice road construction as they carry and distribute the water needed to
grow and thicken the road (described in 4.6). It is imperative that the equipment be in good working
order with lubricants and fluids appropriate for cold-weather operations. Tires must be appropriate for
working on ice, and in some cases, chains may be needed. For ice management on traditional roadways,
motor graders are sometimes equipped with serrated blades (also known as “scarifiers”) for the purpose
of cutting small grooves along the ice. This creates better conditions for traction with rubber tires. Along
an ice road, conditions may develop that warrant the use of this same technique in order to decrease ice
6.10
Design and Construction of Ice Roads Ice Road Construction
slickness. Equipment utilizing metal or rubber tracks will require ‘grousers’ installed on alternating track
links. Dangerous ‘skate’ conditions can occur when traversing side slopes with metal tracks not grouser
equipped.
6.5 Safety features
In general, the safety features and practices observed for standard road construction may also be
applicable to ice road construction, but a few points should be added and emphasized due to the unique
nature of the construction process. Because ice road construction may often take place in dark winter
seasons, each vehicle should have all work and safety lights functional, and, if necessary, equip
additional lighting to ensure effective visibility both for the operator and others outside the vehicle.
Each vehicle should have a working 2-way radio for communications for both operational activities and
for safety considerations. Radios should be verified over long ranges and function in harsh conditions
because of the unique and often remote locations. Marine safety equipment such as personal floatation
devices (PFD) or similar should be included in the cab of each vehicle for use by the operator in the
event of a breakthrough. In-cab heat should be fully functional for each vehicle, and an additional,
stand-by heat source may be a consideration in some cases. Finally, operators should routinely ensure
vehicles are equipped with basic safety equipment such as the following:
Table 6.2 Required Safety Equipment
• Reflectors or flares
• Shovel
• Hatchet, axe or saw
• Tow strap, rope, or chain
• Basic tool kit
• Jumper cables
• Flashlight
• First aid kit
• Personal survival kit (including
thermal blankets)
• Food (rations)
• Matches
• Personal Flotation Device
• Knife
• Rescue Ropes
•
Ice cleats (or similar)
6.5.1 Safe operations
Construction equipment operation begins with a thorough daily inspection of the vehicle by the
operator. Figure 6.6 shows an example of a checklist that can be used for such an inspection.
Design and Operation of Ice Roads
6.11
Ice Road Construction Design and Construction of Ice Roads
Figure 6.6 Example of pre-operation checklist.
As construction proceeds, operators should perform regular scans of the ice surface ahead, behind and
on each side of the vehicle wherein they look for cracking or other hazards indicating poor ice quality.
Operators should know the vehicle weight and the ice thickness in the area of operation. Construction
vehicles should maintain safe speeds (Table 8.2) at all times. They should keep safe distances while
working near other equipment in order to avoid overloading the ice cover.
Construction vehicles that may be equipped with metal tracks may damage the ice cover surface with
zero-degree turns, and operators instead may consider multi-point turns if sufficient, safe area exists.
6.12
Design and Construction of Ice Roads Ice Road Construction
Construction and support vehicles should maintain the safe speed limit for their weight and ice thickness
as discussed in section 4.3 and chapter 10.
6.5.2 Worker safety
As with any construction project, worker safety is the number one priority. Ice road construction is no
different, and much of the same personal protective equipment (PPE) used on traditional jobsites is
applicable here (Table 6.2). Equipment movement, environmental conditions, and other hazards are
some of the primary considerations for worker safety. Any personnel walking or working near an
operating piece of equipment should ensure clear communication with the equipment operator
verifying that the operator is always aware of their proximal position. Given that any foot traffic on the
ice cover is inherently slippery, appropriate footwear should be worn.
6.5.3 Record Keeping
Inspection reports, when properly kept, provide useful information such as weather conditions,
operational and maintenance activities, unusual traffic, ice conditions, etc. This data can be reviewed at
a later date to help make decisions about operational changes, develop correlations between observed
data and performance, and identify conditions leading up to a failure. It is important that the
information included in the inspection report provides only defendable data without opinion or
interpretation. Figure 6.7 provides a suggested template for an inspection report.
Design and Operation of Ice Roads
6.13
Ice Road Construction Design and Construction of Ice Roads
Figure 6.7 Inspection Report Template
Prepared by:
Date:
Ice Road for The Village of
Weather
Ice Conditions
Traffic
Maintenance
Activities
Unresolved
Issues
Ice Road Inspected by
Design and Operation of Ice Roads
7.1
Ice Road Signage Design and Construction of Ice Roads
CHAPTER 7. ICE ROAD SIGNAGE
7.1 Purpose and Intent
Winter ice road traffic signs and route markers are an important part of ice road safety. It is required
that ice road signage follows standard Manual on Uniform Traffic Control Devices (MUTCD) standards
and guidance (FHWA 2009), where applicable. However, ice road conditions can change rapidly, and
certain situations may require additional or different signage than permanent all-season roads.
The information presented in this chapter is intended solely for the purpose of signing and delineating
ice roads. Where deviations from the MUTCD exist, the use of that signage may not be transferred or
used in other conventional roadways applications.
Examples of MUTCD signage appropriate for ice roads are shown in Appendix B, Examples of MUTCD
Signage.
7.2 Design
Ice roads are considered Low Volume Roads as defined by the MUTCD. Ice road signage shall be
designed in accordance with the provisions contained in Part 5 of the MUTCD, “Traffic Control Devices
for Low-Volume Roads”, and where required, in other applicable parts of the MUTCD.
7.2.1 Signs and Plaques Sizes
The typical sizes for signs and plaques installed on low-volume roads shall be as shown in Table 7.1. The
sizes in the minimum column shall be used given the ice road speed limits listed in Chapter XX. The sizes
in the oversized column should be used where engineering judgment indicates a need based on high
vehicle operating speeds, driver expectancy, traffic operations, or roadway conditions. Signs and
plaques larger than those shown in Table 7.1 may be used (see MUTCD Section 2A.11).
7.2.2 Visibility
All signs shall be retroreflective or illuminated to show the same shape and similar color both day and
night. The requirements for sign illumination shall not be satisfied by street, highway, or strobe lighting.
All markings shall be visible at night and shall be retroreflective unless ambient illumination provides
adequate visibility of the markings.
Conspicuity is defined as the quality of a sign or plaque to appear prominent in its surroundings. It is a
measure of how a sign can attract or gain the driver's attention. Based upon engineering judgment,
where the improvement of the conspicuity of a sign or plaques is desired, a number of methods may be
used, as appropriate, to enhance the sign’s conspicuity (see MUTCD Section 2A.15, Enhanced
Conspicuity for Standard Signs).
7.2
Design and Construction of Ice Roads Ice Road Signage
Table 7.1 Sign and Plaque Sizes on Low Volume Road (Example. MUTCD (2009) pg. 532)
Sign or Plaque
MUTCD Manual
Sign Sizes
Sign
Designation
Section
Typical
(inches)
Minimum
(inches)
Oversized
(inches)
Stop
R1-1
5B.02
30x30
—
36x36
Yield
R1-2
5B.02
30x30x30
—
36x36x36
Speed Limit (English)
R2-1
5B.03
24x30
18x24
36x48
Do Not Pass
R4-1
5B.04
24x30
—
36x48
Pass With Care
R4-2
5B.04
24x30
18x24
36x48
Keep Right
R4-7
5B.04
24x30
18x24
36x48
Do Not Enter
R5-1
5B.04
30x30
—
36x36
No Trucks
R5-2
5B.04
24x24
—
30x30
One Way
R6-2
5B.04
18x24
—
24x30
No Parking (symbol)
R8-3
5B.05
24x24
18x18
30x30
No Parking
R8-3a
5B.05
18x24
—
24x30
No Parking (plaque)
R8-3cP,3dP
5B.05
24x18
18x12
30x24
Road Closed
R11-2
5B.04
48x30
—
—
Road Closed, Local Traffic Only
R11-3a
5B.04
60x30
—
Road Closed to Thru Traffic
R11-4
5B.04
60x30
—
—
Weight Limit
R12-1
5B.04
24x30
—
36x48
7.3 Application
Generally, all required signage must be in place before an ice road or crossing is open to the public.
There are three categories of signage: Construction, Entry signs, and regulatory and advisory signs.
7.3.1 Construction Signs
While an ice road is under construction and not yet open to the public, barricades and signs are posted
at the entrance to the ice road stating that it is closed. Best practices include regular checks and patrols
to ensure barricades are always in place.
7.3.2 Entry Signs
Signs are posted at each major river crossing and at the entrance to all ice roads. The types of
information that can be included in entry signs is listed in Table 7.2. Examples of entry signs are shown
in Figure 7.1.
Design and Operation of Ice Roads
7.3
Ice Road Signage Design and Construction of Ice Roads
Table 7.2 Entry Sign Information
Whether the road or crossing is open or closed
Maximum allowable Gross Vehicle Weight
Maximum Speed limit
Minimum distance between vehicles
Phone number to call for road information
Services available on the road if any
Advisory on tire chains and survival gear
Distance to next community
Figure 7.1 Example of Entry Signage (Saskatchewan Ministry of Highways and Infrastructure 2009)
7.3.3 Regulatory and Advisory Signs
Signs can be posted along the ice roads to provide information, reinforce regulations, delineate the
travel lanes, advise travelers of road conditions. The types of information that can be included in entry
signs are listed in Table 7.3.
7.4
Design and Construction of Ice Roads Ice Road Signage
Table 7.3 Regulatory and Advisory Sign Information
Type Application
MUTCD
Section
Speed Limit.
Speed limit signs should be posted as required.
5B.03
Weight Advisory.
Maximum allowable Gross Vehicle Weight
2B.49
Traffic Control.
Traffic control devices such as flags and barricades can be used to
direct the flow of traffic.
Chapter
3H
Delineators
Delineators are particularly beneficial for marking the edges/limits
of the maintained ice road which may not be apparent due to lack
of contrast between ice and snow. Delineators provide additional
guidance at night and during adverse weather. Delineators shall
consist of retroreflective devices that are capable of clearly
retroreflecting light under normal atmospheric conditions from a
distance of 1,000 feet when illuminated by the high beams of
standard automobile lights. Retroreflective elements for
delineators shall have a minimum dimension of 3 inches.
Chapter
3F
Warning and
Hazard Signs.
Signs/markers are used to identify and mark hazards on the ice
road. When a hazard cannot be removed, road users should be
alerted to the nature of the hazard.
Chapter
5C
Barricades.
Barricades may be installed in an emergency to attract attention to
a sign message or to identify a particular hazard or obstruction.
6F.63
Information and
Mile Markers.
Signs on ice roads inform users of the distance and route to the
next community where fuel, accommodation and food are
available. Mile markers are placed every 5 miles to indicate the
distance from the start of the ice road.
2H.05
Acknowledgment
Signs
To indicate the village/person who “adopted” or maintains the
roadway
2H.08
Design and Operation of Ice Roads
8.1
Ice Road Vehicle Control Design and Construction of Ice Roads
CHAPTER 8. ICE ROAD VEHICLE CONTROL
8.1 Introduction
This chapter describes the maximum speed limits, minimum distances between vehicles, control of
stationary loads, and load management for ice roads.
8.2 Maximum Speed Limits
The maximum speed limit allowed depends on vehicle loading, ice conditions, and the situation of the
vehicle, such as approaching a shoreline, approaching an oncoming vehicle, etc. In addition, the
interaction of the vehicle with the ice cover and the water beneath the ice cover can have a significant
impact on the stresses on the ice. A stationary vehicle on the ice cover creates a symmetric deflection
bowl. As the vehicle moves the deflection bowl it creates moves with it. The deflection bowl moves the
underlying water aside in a manner like that of a shallow draft boat. At low speeds, the deflection bowl
moves with the vehicle and maintains its symmetric shape around the vehicle. There is little impact from
the fluid motion created by the deflection at these low speeds. As the vehicle speed increases the
deflection bowl changes shape and rims of the bowl begin to rise. When the vehicle reaches the “critical
speed” the ice sheet deflection and stresses are amplified. The critical speed is a well-defined speed at
which the maximum ice deflection is approximately twice that of a stationary load. Critical speed is a
function of both the water depth and ice thickness. It is shown in Figure 8.1. In shallow water the critical
speed is determined by the water wave speed which is equal to the square root of the product of
gravity, g, and the water depth, H. In deep water, the critical speed is determined by the ice thickness, h.
Figure 8.1 Critical Wave Speed as a function of water depth, H, and ice thickness, h.
The deflection of the ice cover goes through several stages as the vehicle approaches the critical speed
and exceeds it. These stages are shown in Figure 8.2. The first stage occurs when the vehicle speed is
8.2
Design and Construction of Ice Roads Ice Road Vehicle Control
less than 70% of the critical speed. This is the quasi-static stage where the actual deflection is about the
same as for a stationary load. The next stage, between 70% to 85% of the critical velocity is a symmetric
transition stage where the deflection bowl becomes deeper and narrower, and the rim around the bowl
rises. The next stage, between 85% to 100% of the critical velocity is an asymmetric transition stage. In
this stage the main ice deflection becomes deeper and narrower, and two asymmetric features start to
develop: the forward rim of the ice depression begins to evolve into a wave-like pattern, and the center
of the deflection bowl lags increasingly behind the vehicle. At speeds greater than the critical speed the
vehicle enters a wave-generating mode with a well-defined wave train in the ice ahead of the vehicle.
The vehicle assumes a position approximately half-way up the forward slope of the deflection bowl and
retains this position at all higher vehicle speeds. The ice wave pattern changes progressively with
increasing speed.
Figure 8.2 Stages of Ice Cover Deflection as a function of the Vehicle speed relative to the Critical Speed.
Moving loads traveling at and above the critical depth cause increased stress in the ice cover. The
greatest risks occur when moving loads transit from deep water to shallow water over a short distance.
This can happen at access points, sand bars, and other channel bottom changes and lead to ice cracking
and blowouts. It is important to control vehicle speeds to reduce the chance of travelling at critical
speed and cracking the ice cover during a depth transition.
The ice thickness recommendations listed in Chapter 4 are strictly for stationary loads. It is important
that the set speed limits keep the vehicles in the quasi-static stage or less than 70% of the critical speed
Design and Operation of Ice Roads
8.3
Ice Road Vehicle Control Design and Construction of Ice Roads
so that the weight limits remain applicable. The maximum speed limits for vehicles on ice are listed in
Table 8.
Table 8.1 Maximum Speed Limits
Vehicle Situation
Maximum Speed Limit
Vehicle operating at the minimum ice thickness
for its weight
15 mph (25km/h)
Vehicle operating at 2 x minimum ice thickness
for its weight
25 mph (35km/h)
Approaching or leaving shore access points
5 mph (10km/h)
Meeting oncoming vehicles
5 mph (10km/h)
Passing work crews
5 mph (10km/h)
GPR Profiling
5 mph (10km/h)
8.3 Minimum distances between vehicles
Minimum distances between vehicles prevent the deflection bowl created by each vehicle from
combining and causing excessive stress levels in the ice cover. Minimum distances also allow time for
decay of any waves or hydraulic disturbances to the underlying water column that are generated by the
moving load before the following load arrives. Recommended minimum distances between vehicles are
listed in Table 8. (Northwest Territories 2015).
Table 8.2 Minimum Distances Between Vehicles
Vehicle Weight
Minimum Distances
Time Spacing at 25 mph
Vehicles < 11,000 lbs
660 ft (200m)
18 seconds
Vehicles > 11,000 lbs
1,640 ft (500m)
45 seconds
8.4 Stationary loads
Stopping or parking loaded trucks on the ice is always prohibited. Arrangements must be made to move
disabled vehicles off the ice cover as soon as possible. Vehicles approaching a disabled vehicle should
not stop but should slowly move past the disabled vehicle with as much spacing as possible.
8.5 Load Management
Traffic should be restricted to vehicles with a Gross Vehicle Weight that meets the requirements for
bearing capacity of the current ice conditions. The ice cover bearing capacity is discussed in Chapter 4. It
is important that the bearing capacity information be posted at every Access Point so that users can
compare the Gross Vehicle Weight of their vehicles before accessing the ice road. However, it is not
uncommon for the Gross Vehicle Weight including equipment, cargo, passengers, and fuel to be
unknown within a large margin. If the Ice Road is operating under the Substantial Risk level, vehicles
8.4
Design and Construction of Ice Roads Ice Road Vehicle Control
should be weighed using a portable vehicle scale “with all the components, fuel, tools, and gear
included.” This information should be affixed to the vehicle or equipment where the operator can read it
to make sure it is safe to go on the ice.
Design and Operation of Ice Roads
9.1
Ice Road Monitoring and Maintenance Design and Construction of Ice Roads
CHAPTER 9. ICE ROAD MONITORING AND MAINTENANCE
9.1 Monitoring
Monitoring the ice cover is done through visual inspection and ice thickness surveying. The frequency of
the monitoring program is described in Table 9.1. Visual inspection requires personnel to travel the
entire route of the ice road looking for dry cracks, wet cracks, water on the ice cover, snow drifts, and
other problems that may compromise the integrity of the ice cover and interfere with the movement of
vehicles. Visual inspections can be conducted at fixed intervals of one week or more when conservative
A values for Gold’s Formula are adopted, for example A values in the range of fifty-seven or less. The
interval of inspection should be shortened as the A value is increased, with daily inspections occurring at
higher values. Records of the visual inspections should be made and archived. Any problems
encountered should be reported.
Ice thickness surveying can be done manually or using GPR. Manual surveying is acceptable for
conservative A values. However, as the A value is increased GPR surveying becomes mandatory. One
critical point of surveying is to locate areas of the ice cover that are thin. GPR surveying of ice thickness
provides a continuous record of ice thickness along the ice road. All survey data should be recorded and
archived. Thin sections of the ice cover should be reported.
Table 9.1 Monitoring Program
A Value
Level of Risk
Visual Inspection
Surveying
50 Low
-At least once every three days
-checking of ice quality
-Manual measurements every 10-14
days
57 Tolerable
-Regular Ice quality monitoring
program
-Program of regular manual ice
measurements
71 Moderate -Daily Ice quality monitoring program
-Daily program of regular ice
measurements or program for
regular GPR ice profiling plus manual
ice measurements
85
Substantial –
Special
Procedures
-Daily Ice quality monitoring program
-Daily program of regular ice
measurements or program for
regular GPR ice profiling plus manual
ice measurements
9.1.1 Visual Inspection
Inspectors on frozen water bodies can deduce much simply by visual inspection of the ice cover surface.
An example of cracks is shown in Figure 9.1. Some features that provide insight into ice quality are listed
in Table 9.2.
9.2
Design and Construction of Ice Roads Ice Road Monitoring and Maintenance
Figure 9.1 Examples of ice cover cracks. A shallow dry crack and refrozen wet cracks are shown.
Table 9.2 Ice Cover Features of Interest
Cracks
Wet or Dry
Wet cracks extent completely through the
ice thickness and liquid water is visible at
surface. Dry cracks can be of any depth.
Quantity
Density of cracks per unit surface area
Length and Width
Cracking across the expanse of the water
body could indicate a preferred failure
point and should be marked.
Ice Color
Clear, blue generally indicators of favorable ice
White, milky generally indicators of snow ice or ice with more air
bubbles which can be less favorable though still satisfactory
Brown, grey, or other off colors generally indicate frozen objects
within ice such as sticks, rocks, or other organics which can
decrease the load bearing capacity of an ice sheet.
Ice Condition
Openings
If there are openings, inspectors should
determine if the ice sheet has been
undercut and, if so, to what extent.
Undercut or overhanging sections of ice are
generally unfavorable.
Rough ice
If there are jagged or uneven sections of
ice, it may indicate a rock or other larger
frozen object below.
Standing Water
If possible, determine the source of the water
The following table is a suggested checklist for visual inspections of ice sheets.
Design and Operation of Ice Roads
9.3
Ice Road Monitoring and Maintenance Design and Construction of Ice Roads
Table 9.3 Suggested Checklist for Visual Inspection of Ice Sheet
Date:
_________
Time:
_____________
Location:
Cracking Extent and Geometry
Dry Cracks
Number:
Max Penetration: ________%
Wet Cracks
Number:
Max Width: ____________In.
Comments:
Ice and Surface Characterization
Ice Color
Clear/Blue/Black
Thickness: ____________In.
White
Thickness: ____________In.
Other__________
Thickness: ____________In.
Snow Cover
Depth: ____________In.
Surface
Roughness
Water on Ice
9.2 Maintenance
Maintenance involves repairing dry and wet cracks, controlling loads, directing traffic during repairs,
modifying, replacing, or adding to signage, snow removal, and other tasks required to keep the ice road
in good order and allow traffic to move. Maintenance can be conducted on a ‘as needed’ basis when
conservative A values for Gold’s Formula are adopted. The interval of maintenance should be shortened
as higher A values are adopted, with daily maintenance occurring at higher, less conservative values.
9.2.1 Crack Repair
It is possible to repair dry cracks by flooding the ice surface, filling in the cracks, and allowing the water
to freeze. Wet cracks can also be repaired by allowing them to freeze and then flooding them if
required. The allowable vehicle load may need to be reduced while the cracks are being repaired, or the
traffic may need to be detoured around the affected area, or in severe cases, the existing alignment may
need to be abandoned. The procedure for crack remediation and load management is shown as a flow
chart in Figure 9.2. Wet and dry cracks are handled separately. Three options are provided for wet
cracks: close area to loads, close area and repair crack, and bridge crack with rig mat or an engineered
mat. The ice road operators would need to select the option that best matched the actual field
9.4
Design and Construction of Ice Roads Ice Road Monitoring and Maintenance
conditions and their level of operations. The options for dry cracks depend on the depth of the crack
compared to the ice cover thickness. If the crack depth is less than 25% of the ice cover thickness the
crack should be monitored and repaired as required. If the crack depth is between 25% and 50% of the
ice cover depth, the area should be closed in sections and the cracks repaired. If the crack depth is over
50% of the ice cover thickness three options are provided: close area and divert loads, close area and
repair crack before reopening, or reduce load by 50%.
Table 9.4 Maintenance Program
A Value
Level of Risk
Maintenance
50
Low
- Repairs and maintenance as needed
57
Tolerable
- Repairs and maintenance as needed
71 Moderate
- Regular program of repairs and
maintenance
85
Substantial –
Special
Procedures
-Daily program of repairs and
maintenance
Figure 9.2 Assessing Ice Cracks for Maintenance (Alberta Government 2013)
Design and Operation of Ice Roads
9.5
Ice Road Monitoring and Maintenance Design and Construction of Ice Roads
9.2.2 Snow Removal
Keeping ice roads free from extensive buildup of snow covers is an important part of ice road
maintenance. The buildup of snow covers can result from snowfall, snow drifting, or a combination of
both. Generally, trucks, graders, and other available equipment are mounted with snowplows to remove
the snow from the ice road. Large truck-mounted snowblowers can also be used. The best results are
achieved when the snow is cast away from the ice road as far as possible.
The stress that snow removal places on equipment and personal depends on how rapidly snow builds up
on the ice road through snowfall and drifting. If snow removal only occurs once when the snow road is
constructed and then only intermittently during the period that the ice road is open, then the stress
level will be relatively low. In this case, there will be enough time between snow removal periods that
the equipment can be kept in good repair and the crews rested. If snow removal is required
continuously and over an extended period of time, then the stress level will be high. Maintaining all the
equipment in good working order will be difficult and the crew will be worked hard. There will be a
premium on having new equipment as older equipment will tend to need to be repaired more often.
There can be problems with the long-term loads that result from the windrows on each side of the road
that can lead to the formation of wet cracks. If the height of the windrows exceeds the ability of the
snowplows to cast the snow off the road, then the ice road may need to be abandoned and a new road
constructed.
Design and Operation of Ice Roads
10.1
End of Season Closure Design and Construction of Ice Roads
CHAPTER 10. END OF SEASON CLOSURE
10.1 Overview
The integrity of ice roads declines in late winter due to increases in air temperature and sunlight. This
decline is the result of surface degradation, internal deterioration through penetration of sunlight, and
thinning of the top and bottom of the cover. Eventually the ice road integrity declines to the point
where public safety is compromised and the road must be closed for the season.
This chapter covers the issues that are associated with the End-Of-Season closure of the ice road. These
are ice cover melting, end-of-season monitoring, closure procedures, and emergency procedures.
10.2 Ice Cover Melting
Ice cover melting includes several processes that occur when ice covers absorb heat. Surface
degradation results from the accumulation of excessive water on the surface of roads or ice crossings
due to surface melting and the softening of the upper portion of the ice sheet to a degree that inhibits
travel for most vehicles. Deterioration generally refers to internal melting of the ice cover due to the
absorption of sunlight within the cover. Internal melting increases the porosity of the ice cover and leads
to significant losses in strength. Ice covers can deteriorate significantly with little or no change in
thickness. The thinning of ice covers describes the reduction in the thickness of the ice cover through
melting at the top and/or bottom surface of the ice cover.
In late winter, the energy of the sun is often strong enough to cause surface degradation, even when
ambient temperatures remain below 32°F. Dark surfaces from sand, gravel, and other debris on the ice
surface absorb energy from the sun due to their dark color. This results in melting in areas where there
is a large concentration of dark sand/gravel. Maintenance crews can extend the length of the season by
scraping these areas clean on a regular basis. Canadian sources (Northwest Territories 2015) report that
most ice roads will be forced to close as a result of surface degradation, long before the integrity of the
ice road is jeopardized.
Deterioration of ice covers is caused by sunlight penetrating the surface and melting the internal ice of
the cover. Deterioration will happen most rapidly when the ice cover is bare and is exposed to long
hours of sunshine. Deterioration is difficult to detect because it cannot be easily measured in the field.
The integrity of the ice cover is directly degraded by deterioration.
Ice cover melting can occur at both the top and bottom surface of the ice cover. Generally, the water
temperature is at or very near 32°F when an ice cover is in place so little or no melting occurs on the
bottom of the ice cover. However, if open water leads form, then the flowing water is warmed by
absorbing sunlight. This can cause rapid melting downstream of the leads.
10.3 End of Season Monitoring
The frequency of ice cover monitoring should increase near the end of the season. Ice thickness
measurements should be a part of the monitoring program to determine if thinning has occurred.
Ground Penetrating Radar cannot be used to measure the ice thickness when there is water on the ice
surface. Cracks, excessive water, and areas of surface degradation should be located.
10.2
Design and Construction of Ice Roads End of Season Closure
10.4 Closing Procedures
10.4.1 When is closing required?
As the ice cover melts eventually, the ice road will need to be closed. It is not possible to provide precise
conditions when an ice road is unsafe to operate. However, the following guidelines are recommended
to the ice road supervisors when exercising their judgement when an ice road should be closed. Ice
roads can continue to be operated safely for as long as supervisors can maintain confidence in the
minimum ice thickness, the overall integrity of the ice, the trafficability of the ice surface, and the
accuracy of the loading conditions. When ice cover melting prevents the ability to maintain confidence
in ice thickness, ice integrity, and the ice surface, the crossing should be closed.
10.4.2 Closing Access
When the ice road is closed all access points should be blocked with the use of signage, barricades, snow
berms, or other practical means. Signage should be a Road Closed sign described in Table 7.1 and shown
in Figures B.2 and B.4. (MUTCD designation R11-2.) Signs can be mounted on barricades located across
the access roads as shown in Figure 10.1. The road closed signs and barricades should be monitored to
ensure that they remain in place.
Figure 10.1 Ice Road closure sign mounted on barricade (Saskatchewan Ministry of Highways and
Infrastructure 2009)
10.4.3 Announcing Closure
Signs located at access points are the primary means of announcing closure. In addition, public service
announcements advising of the closure can be made on local radio stations, TV, newspaper, and social
media.
10.4.4 Removing Signage
All signage should be removed from the ice road at the end of the season.
10.5 Emergency Procedures
Safe operation on ice and required safety equipment are discussed in Chapter 6. Ice incidents are always
possible and especially near the time of Ice Road Closure. In the event of an ice incident the first priority
is to secure the site to ensure that no one is in danger from further incidents. When visibility is poor and
traffic is likely, it is important to ensure that those working on the incident site are not endangered by
approaching vehicles.
Design and Operation of Ice Roads
10.3
End of Season Closure Design and Construction of Ice Roads
Assess the scene. Determine if anyone is in immediate danger. A rescue effort may be required if a
person is trapped in a vehicle and the vehicle is in an unstable position. Similarly, an injured person may
need immediate medical attention. Deal with life threatening situations or injuries immediately. Deploy
warning signs, flares or barriers to warm approaching traffic and protect those working on the incident.
Call for Help. Call for assistance at the first opportunity. Calls can be made by satellite phones, or 2-way
radios as described in Chapter 6. Provide the following information
• Location
• Brief description of the accident
• Description of injuries
• Assistance required
o Ambulance
o Road closure
o Additional personal or equipment
• Request that the police or other authorities be notified
Wait for Assistance. After calling for assistance, stabilize casualties and provide warmth and shelter.
Maintain the security of the site and stability of casualties until assistance arrives.
Transport. Transport casualties to the nearest medical facility or a location where further transportation
can be provided.
Long Term Response. Remove vehicles from vicinity of ice road and determine if ice road should be
reestablished or closed for the season.
Design and Operation of Ice Roads
11.1
Use of Uncrewed Aircraft Systems Design and Construction of Ice Roads
CHAPTER 11. USE OF UNCREWED AIRCRAFT SYSTEMS
11.1 Benefits and Limitations of UAS for Monitoring Ice Roads
Small uncrewed aircraft systems (UAS) or drones can be used in support of ice road monitoring by
collecting still images and dynamic videos over target areas of rivers, lakes, and their surrounding
landscapes throughout the year. Small UAS are defined as those that weigh more than 55 lbs. and less
than 55 lbs., including all aircraft and payload components, during flight. UAS can provide a broad
overview of an area by flying well above the water surface but can also zoom in to collect more detailed
images using either the aircraft itself or sensors with zoom capacity. Using drones to identify and
monitor ice roads reduces the uncertainty of land or ice-based visual observations and supports the
identification of potential hazards to the road or crossing from a safe distance. The specific use cases of
UAS to support monitoring of ice roads include but are not limited to, route selection, road
establishment, regularly scheduled monitoring, post-storm inspections, and indicators of seasonal ice
road deterioration.
11.2 Open Water
Before a seasonal ice road is established, understanding the baseline river, lake, and landscape
conditions of a particular location where an ice road could be constructed is important. UAS can be used
to collect high resolution baseline imagery of water bodies and the surrounding land from above
allowing for rapid reconnaissance of potential routes. Prior knowledge of a given location can guide UAS
operations towards likely ice road routes, where detailed examinations of channel locations, water
depth, and erosional influences of that area can be performed well before freeze-up conditions. UAS can
also be used during open water seasons to document the changing conditions of those water bodies and
landscapes used to support ice roads from year-to-year that may influence the establishment or safe
operation of an ice road. Commercially available UAS cannot be reliably used to penetrate the water’s
surface, or “see through” the water, to systematically examine channel bed characteristics or other
bathymetric features. In unique cases where the water is exceptionally clear, bathymetric features, as
well as fish and other wildlife, can be seen in the UAS footage through the water, but the 3D
interpretation of those images is currently limited to research and development applications.
11.3 Freeze-Up
Once the water begins to freeze, UAS can be flown over sections of lakes and rivers to identify open
water, regular eddies that are not consistently freezing, and other features that will influence the water
and ice formation throughout freeze-up and potentially throughout the winter season. These shoulder
season flights can also provide information on the ice types developing in the water and rates of
formation of pack ice that will eventually support construction. Commercially available UAS cannot be
used as the only technology to reliably determine ice thickness. However, drones can be used to
monitor ice development and be flown in tandem with manual surveys that are directly measuring ice
thickness. Drone flights can also be used to establish freeze-up patterns of a given water way and the
potential ice road routes once the ice is determined thick enough to support vehicle traffic. Drones can
also be used to monitor the ice road construction progress, to identify efficiencies or in support of
training ice road engineers.
11.2
Design and Construction of Ice Roads Use of Uncrewed Aircraft Systems
11.4 Solid Ice
Once the ice road has been established, UAS can be flown in combination with on-ice visual inspections
to identify dry cracks, wet cracks, water on the ice surface, snow drifts, and other problems that may
compromise the ice road integrity and may not be visible from the inspector’s location on the ice.
Anomalous features identified during UAS flights over established ice roads can be further examined
using zoom features on the sensor being carried by the drone, or by investigating on foot if the
conditions are safe for foot traffic. UAS also can be flown after major storm events to ascertain the
condition of the road to support what maintenance or repair steps need to be undertaken to return the
ice road to safely passable conditions.
The roughness of the ice road surface can be measured using commercially available drones to create
3D models of the ice surface using commercial data processing programs. Ice roughness can be an
indicator of instability of ice depending on the time of year, recent weather, and the surrounding
conditions of the ice and landscape, and is a component of the ice that can be measured confidently by
using UAS as the only tool. A specific example of ice roughness that can be measured with drones are
pressure ridges on lakes, which can be large or small, but indicate areas of unstable ice. Unlike surface
roughness, commercially available sensors on small UAS cannot see through ice, thus cannot be the sole
method used to determine ice thickness or continued ice growth throughout the season. However,
investigations are still needed to determine if these commercial off the shelf UAS and sensor packages
can determine if the ice has grounded to the bottom of the lake or river channel based upon the color or
other components of the UAS-collected information.
11.5 Break-Up
Ice break-up, because of anomalous weather conditions or seasonality, is variable by the ice, the
underlying water, and the weather conditions of the year. As described in Chapter 8, when the air
temperature remains above 32°F for 48 hours or more, the ice road can decay significantly. Using UAS as
a regular monitoring tool for ice roads can help ice road managers identify early indicators of ice
changes that could lead to break-up conditions, thus reducing risk to operators on the ice roads.
Upwelling, wet cracks, and open water can be observed with UAS when snow is not obscuring the
surface and can be mapped relative to the shoreline to identify detours and other risk reduction
strategies. Other ice features that may indicate break-up is imminent that can be observed with UAS
include arched ice (indicating flow beneath), lifted ice (when ice breaks from the shoreline and is
floating on the river, but not moving), and different ice.
One of the most powerful applications of UAS to increase safety prior to and during break-up is change
detection analysis. To effectively monitor changes in ice roads using UAS, regular flights over a defined
area need to be performed. The images and videos can be reviewed manually by ice road managers, but
that process can be very time-consuming depending on how large the flight area is, and how much
corresponding imagery or video has been collected. A more efficient method of reviewing larger flight
areas is to use software designed to ingest UAS images to produce a single 2D map, or orthorectified
map image, which can be displayed on a computer or printed in large format. If the same flight plan is
used, and the same processing methods, subsequent 2D maps of the same area can be created and
systematically compared to each other to identify changes from one flight to the next. This is the
fundamental concept behind the structure from motion (SfM) processing, also known as
photogrammetry, which is becoming more popular for landscape level change detection analyses. The
repeated flights, maps, and analyses allow ice road managers to watch the dynamics of the ice over time
to support management decisions, which are critical during break-up conditions. Artificial intelligence is
ideally suited to support change detection analyses by identifying anomalous features from one ice road
Design and Operation of Ice Roads
11.3
Use of Uncrewed Aircraft Systems Design and Construction of Ice Roads
image to the another taken later in time, though a human reviewer should confirm any identified
feature of the ice.
Larger river break-up trends can also be visualized safely using UAS. Once the ice sheets start to move,
ice jams are a common occurrence in rivers which can cause flooding in communities upstream from the
ice jam location when the flow of the river is blocked; this is also true of log jams during different
seasons. Once these ice jams are released, either naturally or via intervention, communities can also
experience flooding directly downstream from an ice jam, functionally transferring that flood risk
downstream. UAS can be used to identify the ice jam itself, but also can be used to calculate volume of
ice in the jam, changes in river height resulting from the jammed outlet, and aid ice road managers in
the identification of jam release solutions, i.e., strategic ice dam release methods. Observations of these
small to large-scale phenomena with UAS can also be submitted to the National Weather Service (NWS)
River Watch Program (https://www.weather.gov/aprfc/riverWatchProgram
). The Riverwatch program
collects opportunistically acquired river condition observations made by pilots flying throughout Alaska.
Observations are either relayed via radio from the pilot through the FAA, or provided to the NWS via
electronic reports, or digital images that can be used to support community decision-making during
break-up. This observational information is then synthesized by the NWS into maps for community
planning, most often for emergency response because of ice jams, but also planning for non-emergency
components of river break-up as well.
Multiple technologies, such as photogrammetry, live video, thermal imaging, and change detection
analyses, can use UAS-collected data from over ice roads to support decision-making for ice road
managers. The key to utilizing these valuable information streams is following through on all
components of UAS information collection, processing, and dissemination of results to the ice road
managers in a timely way so that important safety decisions can be made as close to when the UAS
collected the data, and before the ice conditions change again.
Design and Operation of Ice Roads
A-1
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
APPENDIX A UNCREWED AIRCRAFT SYSTEMS (UAS)
A.1 Types of Small UAS to Support Ice Road Monitoring
Numerous manufacturers are building UAS for commercial use that could be used to support ice road
monitoring. Those commercial-off-the-shelf UAS that are best suited for use in ice road inspection are
those that can provide a real-time video feed to the operator and that records imagery collected during
the UAS flight. There are three types of small UAS that are available for monitoring ice roads: multi-
rotor, vertical-take-off and landing (VTOL), and fixed-wing UAS. Multi-rotor UAS are the most common
UAS and operate by sets of paired propellers and are most similar in operation to crewed helicopters.
These UAS are the easiest of the three types to operate, are typically easy to pack for transport in rigid
plastic cases or backpacks, tend to be reasonably priced, and are well suited for operations when
hovering over an area is a requirement. Like multi-rotor UAS, VTOL UAS have a small footprint for take-
off and landing, are easy to transport, but these aircraft are not well-suited for hovering, as the vertical
component of VTOL flights are exclusively take-off and landing during which the sensors are non-
operational. VTOL UAS are good for surveying larger areas quickly, are typically more robust than multi-
rotor UAS and can normally carry heavier payloads than multi-rotor aircraft but tend to be expensive in
compared to multi-rotor UAS. Like other types of UAS, fixed wing UAS vary widely in complexity, but are
fundamentally the most like airplanes of the three UAS body types. Fixed-wing UAS can be launched by
hand or by dedicated mechanical launchers; those fixed-wing UAS requiring a launcher also require a
larger dedicated area for take-offs. Fixed-wing aircraft can land by a number of means including belly
landings, runway landings, or via the use of small clips on the end of the wings that fly into a taught,
vertical rope, and slide down the rope to the ground (i.e., skyhook). Fixed wing UAS are well-suited for
large area surveys, carrying heavier payloads, and when flights of long duration are needed, though all
of these flight components vary by aircraft. Costs of purchasing fixed-wing UAS vary widely based on
body composition, take-off and landing method, and power source, rendering these types of UAS either
the most expensive or most cost effective of the small UAS depending on application. Table X highlights
the differences among the three-common small UAS body types.
A-2
Design and Construction of Ice Roads Appendix A Uncrewed Aircraft Systems (UAS)
Table A.1 The three most common types of small UAS, primary characteristics, and sample aircraft of
that type. NOTE: Images of UAS are not to scale.
Multi-Rotor UAS
Vertical Take-Off and Landing
(VTOL) UAS
Fixed Wing UAS
Easy to operate, good for
hovering operations and slower
flights, easily transported, e.g.,
Skydio X2E
Easy to operate, good for
surveying larger area and faster
flights, easily transported, e.g.,
Wingtra Gen II
Easy to operate, good for
surveying larger areas and
faster flights, can carry heavier
payloads, typically quiet
operation, e.g., Sensefly eBee
Cost of the UAS, difficulty of operation, sensor payload, flight endurance, and operating range
(temperature, wind, radio line-of-sight) are the key components to consider when selecting a UAS for ice
road inspection applications. It should be noted that if UAS flights for inspections are being contracted
from a UAS service provider, the choice of aircraft is irrelevant if the resulting information from the UAS
service provider meets the informational needs of the ice road manager.
A.2 Sensor Payloads and UAS Data Products to Support Ice Road Monitoring
A.2.1 Sensor Payloads
UAS can carry a wide variety of sensors as payloads, some of which are quite easy and intuitive to use,
and others that are very complex and require specialized training to use. The two types of sensors that
are the most developed for commercial uses are electro-optical (EO) and infrared sensors. These two
sensors can be used for a broad set of environmental monitoring missions to support ice road
establishment and monitoring throughout the season.
The most common commercially available sensors in use are EO sensors, which capture still images and
videos much like a digital camera. These sensors measure red-green-blue (RGB) light signals from the
visible portion of the electromagnetic spectrum (Figure 9.2). EO image and video uses range from
situational awareness about an area to detailed 2D and 3D mapping efforts. UAS outfitted with EO
sensors are key tools for UAS support of ice roads.
Design and Operation of Ice Roads
A-3
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
Figure A.1.The electromagnetic spectrum; opranic.com
Infrared sensors measure the portion of the electromagnetic spectrum between visible light and
the microwave region (Figure 9.2). Longwave infrared sensors, also known as thermal infrared
sensors, are the most common type of infrared sensors and are used in many environmental
surveys as well as search and rescue efforts. Infrared sensors measure the energy emitted off an object
as compared to the background environment. Infrared sensors are particularly good at identifying water
or warm spots in an ice road as compared to cold background ice, or people lost or hiding in the
environment. Besides EO sensors, infrared sensors have been the most extensively miniaturized in
support of UAS operations.
There are other sensors that are commercially available that could be valuable for monitoring ice roads,
but the data they can provide requires specialized training to collect and process. Light detection and
ranging (LIDAR) mapping techniques are popular surveying tools for determining fine-scale differences
in elevations on the ice roads that can be indicative of underlying ice or water changes or for measuring
hydrodynamic processes. The complexity of data processing as well as the volume of data created by
LIDAR target inspections conducted from a UAS reduce the accessibility of this sensor for operational
decision-making on short time scales. LIDAR are energetically expensive and only recently effectively
miniaturized for UAS and are not developed commercially for non-expert users.
Multispectral sensors provide imagery from multiple ranges of the electromagnetic spectrum as
discrete bands that can be fused into an image composite or kept discrete to discern unique features
about a target that would not visible otherwise. Multispectral sensors mounted on UAS have been used
to examine water quality (i.e., ground water filled with silt, spring water from a creek, silty water from a
glacier), and multispectral sensors on satellites have been used to successfully monitor river ice but
adapting the technique to multispectral sensors mounted on a UAS is not yet common.
All of these sensors require light, or sunlight to be able to identify ice road features. An alternate sensor
that can image an area at night or when it is precipitating is radar. Synthetic aperture radar (SAR) is a
valuable tool for surveying an area at night or through a precipitation event and can be used to identify
open water and wet ice. SAR sensors on UAS have not been commercialized due to the high energy
requirements of the sensor, as well as the complexities and requirement for significant background
knowledge to operate and to process into flight maps and reports.
A.2.2 UAS Data Products
The still images and videos collected by the UAS can be processed through specialized computer
software into flight summary maps, or data products, which can be used by ice road managers for
A-4
Design and Construction of Ice Roads Appendix A Uncrewed Aircraft Systems (UAS)
decision-making. These summary maps functionally stitch together the digital images collected by the
UAS into a single map so that decision-makers do not need to examine each individual image or review
minutes to hours of video collected by a UAS, but instead can get a holistic view of the entire area of
interest in one map. Creating these types of summary maps is becoming easier as the image processing
routines become more and more computer automated. Most of the software that is commercially
available for creating summary maps for UAS-collected data only requires the UAS operator to input the
UAS-collected imagery and select the type of map they want the software to create. UAS operators or
analysts can then share the summary maps via electronic transfer (e.g., email, shared drives, alternative
file transfer protocols) or by printing them, though printing will prevent any zoom capacity for areas of
interest. The most common post-processing software to create summary maps with UAS-collected data
are: DroneDeploy, Pix4D, DJI Terra, Global Mapper, and Drone2Map from ESRI.
The data collected with these light-dependent sensors (EO, infrared, LIDAR, and multispectral sensors)
can be processed using specialized computer software to create maps and other useful information for
ice road managers. Digital surface models (DSM) and orthorectified maps, or orthomosaics, are the two
most popular products generated from UAS-collected data. DSMs are three dimensional maps of an area
that include all natural and fabricated features and are used to calculate changes in height or
topography. DSMs can be used to monitor ice road elevation at specific anomalous location or across
the entire road and are used to support 3D mapping of landscape and riverbed features. The two
primary sensors used for DSM generation are LIDAR and EO sensors. Using post-processing software,
raw data collected from LIDAR or EO sensors is processed into a point-cloud to create a DSM. Once a
DSM of an area of interest has been created, geospatial software packages can be used to create
orthorectified (geometrically corrected) maps to identify or monitor environmental change of the area.
Structure from motion (SfM) is a popular processing and mapping technique used to make
detailed orthorectified maps from georeferenced digital images collected with an EO sensor. The maps
made from the SfM technique are most commonly used for change detection studies, or time-series
information over a given area. SfM is an easier and cheaper data post-processing solution for DSM and
subsequent orthorectified map creation than processes using LIDAR. SfM does not require ground
control points for situating EO images in relative space, but instead relies on overlapping images of a
target to develop orthorectified maps of an area. There are a number of commercially available
software programs that can perform SfM processing that vary in price and complexity. One of the most
powerful applications of SfM processing of UAS data over ice roads has to do with the different
components of change detection. Consistent UAS flights over a given area and processed using the SfM
technique may allow for ice thickness estimations across a season by looking at the elevation differences
in the DSM created by the SfM software. These consistent flights and processed images of the ice roads
may also provide early indicators of lateral ice movement in the spring or estimates of ice jam volumes
to identify management strategies.
Artificial Intelligence, or AI, can be used to identify problem areas along an ice road. AI-based change
detection algorithms can be trained to distinguish irregularities in an ice road image by detecting and
flagging those irregularities for analysts and decision-makers to further examine. Using AI reduces the
amount of time it takes to review UAS flight imagery by focusing the analyst’s attention on what the AI
has identified as potential problem areas. Currently, AI support of ice road feature identification is
limited to post processing of the UAS-flight imagery after landing. Innovations are underway to integrate
these semi-automated AI detection routines into UAS flight image processing during UAS flights, which
would functionally be real-time detection of hazardous ice road components.
Design and Operation of Ice Roads
A-5
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
As with the type of commercially available UAS aircraft selection, the type of sensor and software that
should be used to monitor a range of conditions or specific anomalies of ice roads depends on the type
of information and information summary that will be most useful for ice road managers.
A.3 UAS Flight Requirements, Operational Considerations, and Recommendations
A.3.1 UAS Flight Requirements
There are several requirements that must be met for safe and legal UAS operation over ice roads, or
potential ice road locations. These requirements are not limited to flights over ice roads, but instead are
the general requirements that must be met when flying UAS for other than recreational use.
A.3.1.1 UAS Crew Qualifications and Responsibilities
UAS operations are under the authority of the Federal Aviation Administration (FAA). The UAS Team is
typically composed of UAS Pilots and UAS Visual Observers, with the liability of the mission lying with
the Remote Pilot in Command (PIC). The key responsibilities of the UAS Team are to provide situational
awareness by collecting real-time imagery and to transmit real-time imagery or verbal assessment to ice
road managers to support planning and decision-making. Costs will be dependent on the UAS service
providers.
UAS Pilot UAS pilots collecting imagery of ice roads need to be able to safely operate UAS under one of
two FAA regulations, 14 CFR Part 107 or 49 US Code 40102(a) and 40125 COA.
• 14 CFR Part 107 - Small Uncrewed Aircraft Systems; regulation addresses legal operation of
aircraft less than 55 lbs. flown following Subpart B (Operating Rules) performing the role of
Remote Pilot in Command as outlined in § 107.19; pilots flying using Part 107 certification as
defined in Subpart C (Remote Pilot Certification) will be considered to have acceptable
credentials for individuals representing Federal, State, Tribal or themselves as citizens; civil
operator.
• Certificate of Waiver or Authorization (COA); regulation addresses legal operation of UAS
performing governmental functions (Federal, State or Tribal) and statutory requirements of 49
US Code 40102(a) and 40125 for public aircraft; public operator.
UAS pilots are responsible for maintaining Flight Logs for each individual UAS flight (see Data
Management guidelines below). Each log should at a minimum include date, crew, aircraft, sensors, and
additional notes. UAS Pilots can operate a maximum of 8 consecutive hours and a maximum of 14 hours
per day under specific direction and permission from the ice road manager (Augmented Operations as
per 14 CFR Part 117). All responsibilities of the flight, including acquisition of waivers and reporting
mishaps to the FAA are the responsibility of the Pilot in Command.
UAS Visual Observer (Observers) – Observers are responsible for scanning the airspace where the small
UAS is operating and maintaining awareness of the position of the small UAS through direct observation.
Observers must remain in communication with the pilot in command at all times and be able to
coordinate collision avoidance maneuvers with the pilot in command, as necessary.
A-6
Design and Construction of Ice Roads Appendix A Uncrewed Aircraft Systems (UAS)
Other crew members can provide value by managing data, helping to secure a sterile cockpit (i.e.,
keeping the pilot safe from distractions), or by helping ice road managers interpret the information
provided by the UAS. As with all field work, UAS operations should be undertaken in teams of at least
two people: the PIC and the Observer.
A.3.1.2 Airspace
It is important that UAS operations over ice roads and adjacent areas are flown following the FAA
requirements and guidelines for UAS. Do determine if your operational flights can be conducted without
any prior approval from the FAA or if the UAS operation will require an Airspace Authorization because
the area of interest is near a LAANC enabled airport, or if the operation will require a Flight Waiver to be
conducted, visit B4UFLY, either at, https://b4ufly.aloft.ai/
, or through the B4UFLY app on a smart phone.
B4UFLY synthesizes all national airspace to provide a fast indication of regulations governing a given
airspace of interest, and how to manage a UAS operation in that airspace.
A.3.1.3 Airspace Authorizations
Flights that need to take place near a LAANC enabled airport will require an Airspace Authorization
request submitted through the LAANC system via one of the approved third-party LAANC portals. A
detailed list of LAANC enabled airports is available from the FAA at,
https://www.faa.gov/uas/programs_partnerships/data_exchange/laanc_facilities/#all
. The Alaskan
airports included in this list that are:
Table A.2 Airports Requiring Airspace Authorization
Anchorage (Ted Stevens
International)
Deadhorse Homer McGrath Talkeetna
Anchorage (Lake Hood)
Dillingham
Iliamna
Nome
Unalakleet
Anchorage (Merrill Field)
Fairbanks
Juneau
Northway
Yakutat
Barrow
Fort Yukon
Kenai
Sitka
Bethel
Galena
Kodiak
St. Mary’s
Cordova
Gulkana
Kotzebue
Tanana
To see the different UAS flight altitude restrictions for any of the LAANC enabled airports, visit the online
UAS Facilities Maps, https://faa.maps.arcgis.com/apps/webappviewer/index.html. The UAS Facilities
Maps can be used to identify unrestricted airspace nearby or to help build your LAANC Airspace
Authorization request if operations within the restricted airspace around a LAANC enabled airport is
required.
A.3.1.4 Part 107 Waiver Requests
For all UAS operations that fall outside of the permitted actions outlined under 14 CFR Part 107, or those
that can be permitted through LAANC airspace authorizations, a Part 107 waiver will need to be
requested from the FAA up to 90-days in advance of the UAS operation. The conditions under which a
Part 107 Waiver would need to be requested are listed in Table A.3
Design and Operation of Ice Roads
A-7
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
Table A.3 Conditions that require a Part 107 Waiver
Fly a small UAS from a moving aircraft or a vehicle in populated areas
Fly a small UAS at night without anti-collision lighting
Fly a small UAS during periods of civil twilight without anti-collision lighting
Fly a small UAS beyond your ability to clearly determine its orientation with unaided
vision
Use a visual observer without following all visual observer requirements
Fly multiple small UAS with only one remote pilot
Fly over a person with a small UAS which does not meet operational categories 1, 2, 3, or
4
Fly a small UAS:
Over 100 miles per hour groundspeed
Over 400 feet above ground level (AGL)
With less than 3 statute miles of visibility
Within 500 feet vertically or 2000 feet horizontally from clouds
Fly over moving vehicles with a small UAS which does not meet operational categories 1,
2, 3, or 4 or other conditions
Part 107 Waiver applications and Airspace Authorization requests for non-LAANC airports can be
submitted for review and approval by the FAA through DroneZone, https://faadronezone.faa.gov/#/
.
The DroneZone portal, operated by the FAA, requires the UAS pilot to be registered to access the waiver
application system. To apply for a flight waiver through DroneZone, create an account, or log into an
existing account. Select "Fly a sUAS under Part 107." Users of this service do not need to register a drone
to request a waiver, but without a registered drone, a user must register with LAANC prior to each
operation. In these cases, when prompted to input make/model information for the drone, users can
move through the screen and keep selecting "next" to bypass the payment forms. Submit the
application, including all supporting documents and attachments, through the FAA DroneZone account.
Select the "Operational Waiver" option. Review and approval or disapproval of waiver requests will be
completed within 90 days of submission. Processing times will vary based on the complexity of the
request and the completeness of the initial application. Requesting a Part 107 Airspace Authorization
and/or a Part 107 Waiver, is described in additional detail with additional links to FAA resources here,
https://www.faa.gov/uas/commercial_operators/part_107_airspace_authorizations/
A.4 UAS Flight Operational Considerations
A.4.1 Land Ownership
Another legal consideration for UAS operations is the land ownership status of where the UAS is being
piloted from and the land ownership status over which the UAS is flying if not immediately adjacent to
the water. Rivers large enough to sustain ice roads are those that are deemed Navigable Waters under
33 CFR 329, meaning that permitted access is only to the lands and water below the ordinary high-water
mark of the river. Land ownership status and maps are available from the State Departments of Natural
Resources. It is important to receive permission from the landowner prior to commencing UAS
operations from the property, or over the property if passing over on the way to perform ice road
monitoring. These permissions can be easily obtained or not obtained at all, as such requesting
A-8
Design and Construction of Ice Roads Appendix A Uncrewed Aircraft Systems (UAS)
permission to access the land should be made one to four weeks in advance if possible. Agreements can
be obtained with landowners to cover seasonal access, and it is suggested to get the land access
permissions in writing. These landownership principles also apply to ice roads and bridges over lakes.
It is important to note that UAS operations are currently illegal in U.S. National Parks, and often require
special permitting when flying over other federal or state lands. Contact the representative office for
those tribal, state, and federal offices well in advance of planned operations to allow for the processing
of any permit applications that may be required for that area.
A.4.2 Weather
Small UAS are sensitive to weather. Each commercially available UAS has published tolerance ratings for
wind, precipitation, and temperature, and most UAS are not rated for harsh winter conditions such as
those encountered in Alaska and other northern tier states in the U.S. that could support ice roads. The
primary risk of flying UAS outside of the environmental conditions that it is rated for is potential
equipment failure that could lead to injury.
Wind can significantly impact UAS flights. Most multi-rotor UAS cannot operate in sustained winds
greater than 15 miles per hour. Some UAS also have built in sensors that prevent the UAS from even
taking off if the winds are too high. The most common impact of wind on drones is that flight times are
greatly reduced because the UAS is using battery power to fight the wind to maintain stability, instead of
flying over the target area collecting data. Some UAS can fly in winds up to 20 mph, but in those cases,
most automated functions such as pre-planned flights, do not work, and data collection needs to be
done with manual flights, i.e., not flying a pre-planned pattern that is uploaded to the aircraft. VTOL and
fixed-wing UAS are more tolerant to wind during operation, but still have the challenges associated with
launching on a windy day. It is recommended that UAS operators only fly within acceptable wind speeds
as reported by the manufacturer. If winds are unexpectedly encountered during a UAS operation, it is
recommended that the aircraft be landed as soon as possible so that it remains under the operator’s
control at all times.
Precipitation as rain or snow can damage exposed electronics on a UAS, causing malfunction or failure.
Precipitation also can obscure the sensors as water droplets on the sensor lens. UAS flight operations
should not be initiated during rain or snow events and should cease if rain or snow occurs. Part 107
regulations require flights to only be conducted when visibility of three miles from the ground control
station can be maintained.
Extreme temperatures, both cold and hot, are known to impact UAS operations primarily through
battery performance. Under the cold temperatures experienced during Alaskan winters, many UAS will
not operate according to specifications, thus should not be flown due to the danger of losing control of
the aircraft. Some UAS are outfitted with “smart batteries;” this is a regular feature on DJI batteries.
Smart batteries prevent the UAS from taking off when temperatures are below the operating range
specified by the vendor. The problem is using smart batteries in northern states during fall, winter, and
spring as the operating temperature range is defined as 32-104 F/0-40 C, thus eliminating the value of
the UAS to perform ice monitoring flights. Non-DJI multi-rotor aircraft (e.g., Skydio, Autel, etc.) do not
use smart batteries thus have a larger operating temperature range. For example, the Skydio X2E has
been demonstrated to fly well at temperatures as low as -10F/ -23 C, though they are only rated down
Design and Operation of Ice Roads
A-9
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
to 23 F/ -5 C. As with wind, fixed-wing aircraft tend to be less sensitive to the impact of temperature, but
not entirely. It is suggested that UAS operator know exactly what their UAS will do in different
temperature conditions prior to flying at temperatures colder than the rated temperatures of the
batteries and aircraft.
A.4.3 Wildlife
Flying over wildlife can be dangerous to both the animal and the UAS. Both the sound and sight of the
UAS impacts wildlife, and not all wildlife responds the same to these disturbances. UAS operators should
use due diligence identify the land management status over which they are flying and adhere to wildlife
protection guidelines. Guidance on UAS operations from wildlife managers is not always clear, nor
accessible when in remote locations, and needs to be undertaken early in the flight planning process. In
cases where wildlife managers have jurisdiction over the lands or animals near or directly involved in a
UAS operation, direct coordination with those resource managers needs to take place in advance of UAS
operations. In many cases, specific permits are required to fly UAS over designated wildlife habitat or
refuge areas and these permits require one to four weeks to process, and often have an associated
processing fee. Any permits that have been acquired to support UAS flights over animals need to be
included with other UAS operations documentation and be available for inspection on-site with the UAS
team.
Special considerations and actions are needed if UAS are being operated over state or federal lands that
are characterized as critical habitat for endangered species or migratory birds. The Endangered Species
Act, the Marine Mammal Protection Act, the Bald and Golden Eagle Protection Act and the Migratory
Bird Treaty Act are laws that are applicable to all operations that could impact the animals these laws
have been put in place to protect. If the UAS operation is taking place in an area where any of these Acts
apply, additional coordination with resource managers will need to take place in advance of UAS
operations. The result of not complying with these laws is criminal prosecution.
To reduce wildlife disturbance in areas where no permitting or resource manager coordination is
required, conduct UAS operations between 150 and 400 feet above the coastline/water so as not to
directly impact wildlife. UAS operators need to avoid buzzing, hovering, landing, taking off, taxiing,
excessive speed or sudden changes in speed or direction near wildlife on land or in the water. If animals
appear to be alarmed or are responding by trying to get away from the UAS, the UAS pilot needs to
increase altitude and vacate the area until the wildlife leaves the area, even if it means returning to the
site a different day to perform the UAS flights. UAS operators also need to be aware that birds of prey
(eagles, falcons, and hawks) as well as members of the Corvus family of birds (ravens, crows, magpies),
commonly attack small UAS. If one of the types of birds becomes interested in the drone operating, it is
advised to land the aircraft immediately and wait for those birds to move on. Not landing or moving the
drone away from these types of birds may result in a direct attack on the drone, with the possibility for
significant damage or destruction to the UAS
.
A.4 Data Management
UAS are used to collect still images and video of target objects. Those images and videos, along with
flight logs recorded on the aircraft, should be archived along with the visual inspection and/or ice
thickness measurements each day according to data archiving and sharing protocols established by the
ice road managers. Minimum archival should include preserving all summary flight reports
(requirements below), manually recorded UAS Flight Logs (scanned as PDF or JPG), digitally recorded
A-10
Design and Construction of Ice Roads Appendix A Uncrewed Aircraft Systems (UAS)
flight logs (T-logs and .DAT files), raw data files and any processed data products, such as maps. (See
Table A.4)
Table A.3 Summary flight report information to support archiving of UAS flights
Information
Date:
Crew members (UAS pilot and
UAS observer):
Type of UAS platform (multi-
rotor, fixed wing, VTOL):
Type of sensor used:
Location where the flights
were conducted from (the
ground control station;
geographic location and land
ownership status):
Flight description
(latitude/longitude of flight
area, # of flights at location):
Mission objectives (visual
inspection support, post storm
reconnaissance, etc.) :
Type of survey or sampling
method (e. g. line/strip
transects, sunburst patterns,
etc.):
Altitude of flights:
Total time flown:
Total distances flown:
Number of batteries used:
Weather and other factors
affecting visibility and
detectability of targets (i.e.:
fog/glare):
Data file names:
Data file archive location:
Flight mishaps:
Other notes:
Quality data management is critical for being able to use UAS data of the ice roads over time. Combining
Design and Operation of Ice Roads
A-11
Appendix A Uncrewed Aircraft Systems (UAS) Design and Construction of Ice Roads
quality data records with high quality data products allows for analyses of anomalous features, 3D maps
of the ice surface, open water leads and specific damage from weather events. Ensuring high quality
UAS data records are also important in the case of ice road accidents where review of imagery along a
particular section of river can be critical to determine causes or impacts of accidents along these
seasonal roadways.
A.5 Conclusion on UAS for Ice Road Support
UAS are useful tools for monitoring river and lake ice for road establishment and maintenance. UAS can
be used to identify unique open water features that will influence ice during formation or stability of the
ice near those features throughout the winter season. UAS can also be used to monitor ice dynamics
and ice stability for ice road establishment, monitoring and maintenance before break-up. Though UAS
can provide detailed images of ice roads and potential ice road routes, analyses of the observed ice road
features and anomalies that can influence road safety still require trained interpretation by ice road
managers.
As the impacts of climate change continue to influence weather including ice conditions, reducing
uncertainty in ice road stability will continue to increase in importance. Combined with manual
observations and measurements, the information that can be provided by a UAS can be used to reduce
risk and uncertainty in ice road conditions across the seasons, which in turn could reduce costs and
increase human safety. By combining regular ice observations that are collected from the road surface
via GPR or direct thickness measurements, with UAS flights, a matrix of ice thickness as compared to
UAS observations can be developed to maximize efficiency and safety for future ice roads. The primary
benefit of using UAS to monitor ice roads is the reduction of risk and cost by providing the ability to
safely observe the road and surrounding river without putting people on the ice or into a crewed
aircraft.
Design and Operation of Ice Roads
B-1
Appendix B Examples of MUTCD Signage Design and Construction of Ice Roads
APPENDIX B EXAMPLES OF MUTCD SIGNAGE
B.1 Reference Location Signs
Figure B.1 Reference Location Signs
B.2 Regulatory signs
Figure B.2 Regulatory signs (Example. MUTCD (pg. 534))
B-2
Design and Construction of Ice Roads Appendix B Examples of MUTCD Signage
B.3 Hazard Markers
Figure B.3 Hazard Markers (Example. MUTCD pg. 536)
B.4 Closure Sign
Figure B.4 Closure Sign (Example)
Design and Operation of Ice Roads
B-3
Appendix B Examples of MUTCD Signage Design and Construction of Ice Roads
B.5 Supplemental Warning Plaques
Figure B.5 Supplemental Warning Plaques
B.6 End of Roadway
Figure B.6 End of Roadway (Example. MUTCD pg. 536)
B-4
Design and Construction of Ice Roads Appendix B Examples of MUTCD Signage
B.6 Channelizing Devices
Figure B. 7 Channelizing Devices
B.7 Barricades
Figure B. 8 Barricades
Design and Operation of Ice Roads
B-5
Appendix B Examples of MUTCD Signage Design and Construction of Ice Roads
B.8 Road Closure
Figure B.9 Road Closure
B.9 Examples of Enhanced Conspicuity for Signs
Figure B.10 Examples of Enhanced Conspicuity for Signs
Design and Operation of Ice Roads
C-1
Appendix C References Design and Construction of Ice Roads
APPENDIX C REFERENCES
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Publication Number SH010. Occupational Health and Safety Contact Centre. Alberta Government
https://open.alberta.ca/dataset/612530c3-9f41-41f3-ad45-4b62b47a0b06/resource/74decde6-
8120-46be-b137-158bb63ee569/download/whs-pub-sh010.pdf
Ashton, G.D. (1986) River and Lake Ice Engineering. Water Resources Publications, Littleton, CO.
Daniels DJ (2004).
Ground Penetrating Radar (2nd ed.). Knoval (Institution of Engineering and
Technology). pp. 1–4
FHWA (2009) Manual on Uniform Traffic Control Devices 2009 Edition. Federal Highway Administration
https://mutcd.fhwa.dot.gov/pdfs/2009/pdf_index.htm.
Gold, L.W. (1971) Use of Ice Covers for Transportation. Canadian Geotechnical Journal. Vol. 8,
No. 2, 1971 pp 170-180
Hayley, D., and S. Proskin (2008) Managing the Safety of Ice Covers Used for Transportation in an
Environment of Climate Warming. 4th Canadian Conference on Geohazards, Université Laval,
20-24 May 2008, Québec, Qc, Canada
Infrastructure Health and Safety Association (IHSA) (2014) Best Practices for Building and Working Safely
on Ice Covers in Ontario. Report IHSA029, Infrastructure Health and Safety Association, Ontario,
CA. Report IHSA029
http://devnet.ihsa.ca/Free-Products/Downloads/IHSA029-Best-Practices-
for-Building-and-Working.aspx
Masterson, D. M. (2009) State of the art of ice bearing capacity and ice construction. Cold Regions
Science and Technology 58 (2009) 99–112
Nevel, D. (1970) Moving loads on a floating ice sheet. Research Report 265. US. Cold Regions Research
and Engineering Laboratory.
Northwest Territories (2015) Guidelines for Safe Ice Construction. Booklet published by the Department
of Transportation of the Government of the Northwest Territories.
https://www.inf.gov.nt.ca/sites/inf/files/resources/0016-001_norex_ice_road_constr._web.pdf
Saskatchewan Ministry of Highways and Infrastructure (2009) Winter Roads Handbook. Ministry of
Highways and Infrastructure, Engineering Standards Branch, 350 Third Ave. N. Saskatoon, Sask.
S7K 2H6
http://www.highways.gov.sk.ca/Doing%20Business%20with%20MHI/Ministry%20Manuals/Wint
er%20Roads%20Handbook/Winter%20Roads%20Handbook.pdf
Richards, E., Stuefer, S.L., Rangel, R., Maio, C., Belz, N., Daanen, R.P., (2022) An evaluation of GPR
monitoring methods on varying river ice conditions: a case study in Alaska. Cold Regions Science
and Technology, in review.
