This document summarizes a presentation on managing gravel road maintenance. It discusses critical issues like road geometry, gravel quality and quantity, and maintenance practices. It provides examples of proper gravel road cross sections and recommendations for drainage. Test results show that meeting minimum gravel specifications reduces loose gravel and corrugation compared to substandard gravel. A study in South Dakota found that using higher quality gravel increased road life and reduced maintenance needs. Stabilizing gravel with additives like cement or chlorides can further improve durability and reduce maintenance costs. Training for managers and operators was identified as important to ensure best practices are followed.

1. Managing Gravel Road Maintenance
2015 NACE Conference – Daytona Beach, FL
4-22-2015
Presented by:
Ken Skorseth, Program Manager
South Dakota Local Transportation Assistance Program
South Dakota State University
Brookings, South Dakota, USA

2. Overview of Presentation
• Critical Issues:
–Roadway Shape or Geometry
–Gravel Quality and Quantity
–Maintenance Practices
–Training needs (if time allows)

3. A good resource:
The FHWA Gravel
Roads manual –
currently out of print,
but is available online

4. Good example of a Low Volume Rd Design Guide
Good guidance, non-
technical, accommodates
unpaved road design.

5. Basic Cross Section

6. Sketch of One Half of Roadway – Rural Section
(from center to left)
Foreslope:
recommended at 3:1
slope
A flat bottom ditch
is recommended,
hard to build at less
than eight feet.
Backslope as ROW
allows
3 ft. (example only)
The challenge is often
working in a confined R-O-W.

7. From AASHTO Guidelines for Geometric Design of Very
Low-Volume Local Roads (ADT < 400)
Agricultural Access Classification:
Minimum roadway width is 24 ft at 20 to
40 mph design speed, increases to 26 ft if
design speed is 50 mph

8. Great project, but few new gravel roads
are built

9. Good ditch construction and drainage

10. Gravel Road Rehabilitation: Often the Best
Improvement Possible

11. Any tool to help break sod and clumped soil is
helpful

12. Sometimes this is reality in confined ROW

13. No real cross section – You have to do
better than this!

14. Not many gravel surfaced roads are being built
in the US. Many existing gravel roads need
rehabilitation
Some best practice examples:

15. Complete rehabilitation of a county road
in Day County, SD -2013 Season

16. Recovery of aggregate from foreslope and
reestablishing shoulder line
Road originally constructed in 1970s

17. Modern tools can make the job easier

18. Salvage of remaining gravel

19. Soils in this area are weak – generally silty
clays

20. Done entirely with county equipment

22. Mixing & processing subgrade soil

23. Doing the best they can with what they have

24. Good tool
if other
compaction
equipment is
not available

25. Picking rocks the easy way!

26. Spreading the salvage gravel

27. Finished slopes

28. Finished surface

29. Finished shoulder line

30. First lift of new gravel – 2.5 inches

31. Project done with same process two years
earlier – road is so much easier to maintain

32. Another Challenge – Reverting Asphalt Surfaces
to Unpaved Surfaces:

33. Recycle Process
Virgin gravel
course added on
roadway prior to
recycling.

34. Recycle Process (Con’t)

35. Reshape & compaction of the material

36. Outstanding performance
Performance documentation
on 2-7-2013. This road had
no blade maintenance since
May, 2012. ADT is 75

37. Maintenance Challenges After Construction or
Rehabilitation:

38. 10 inches average
annual rainfall
65 inches average
annual rainfall

39. Maintaining no crown

40. A crown gauge is helpful

41. Electronic Slope Reading
In the motorgrader cab: On-board electronics
are coming to the market very quickly

42. Slope Control systems on motorgraders are a
great aid in construction and rehabilitation

43. Poor surface drainage
Electronics only work if the operator accepts it!

44. Good surface drainage

45. Crown Example on 20 Ft Road Surface

46. The Next Challenge – High Shoulders!

47. Reasonably good cross section on low volume road
with poor horizontal and vertical alignment

48. Some thoughts on roads with severe horizontal
and vertical alignment problems

49. Drainage is critical

50. Just as critical is surface aggregate quality

51. Most of the surface is tightly bound here

52. Surface aggregate has good overall gradation
and relatively small top size.

53. Virtually no corrugation on day of observation

54. Recent roadway reshape is very good

55. Drainage run-out to carry water away from
road with erosion control – good practice.

56. Good culvert installation under driveway

57. Vertical alignment makes maintenance very
challenging – grade checked at 23.4% at one
location!

58. Managing Gravel Quality and Quantity

60. Recent validation check of material quality in SD

61. Gradation/PI Tests
61
List of Gravel Sources
Deuel County A
Deuel County B
Beadle County
Miner County
Hughes County
Mitchell Township
Lincoln County
Clay County
Jerauld County
Why these sites chosen?
Previous data seems inaccurate
Study contrast in local
materials used on unpaved
road

62. Summary
62
Source Gradation PI
Deuel County A Failed Failed (No PI)
Deuel County B Failed Failed (No PI)
Beadle County Failed Passed (5)
Miner County Failed Passed (6)
Hughes County Failed Passed (4)
Mitchell Township Failed Failed (No PI)
Lincoln County Passed Failed (no PI)
Clay County Failed Passed (7)
Jerauld County Failed Passed (4)

63. Gravel Quality Issues
• Gradation problems generally confined to small
percentage retained on 1 in. sieve (SDDOT Gravel
surfacing spec requires 100% passing 3/4 in. sieve.
• Generally good on the split between coarse and fine
aggregate on the #4 sieve.
• SDDOT Standard Specification requires minimum
plasticity index (PI) of 4 and maximum of 12
– Only five of nine samples had PI.
– Maximum PI tested was 7.

64. Part of the problem in not getting plasticity:

65. Managing Layer Thickness: Coring a Gravel Road:

68. Over two inches of thickness deviation

69. Example of test pit in existing gravel road

70. Calculate spread
rates on gravel
projects

71. It requires 407 cubic yards (570 tons) to place
one inch of gravel on a one mile 20 ft wide.

72. A 25-ton load of gravel covers only 320 linear ft to
place one inch of gravel on one mile 20 ft wide.

73. Nice job of processing and placing gravel

75. The skilled
operator is the key
to controlling
gravel road shape
and placing gravel.

76. Note: this is an adequate layer for maintenance,
but not adequate thickness to carry legal loads
in all conditions!

77. Deep Layer Needed to Carry Heavy Loads
14.5 inches of gravel needed
to carry 25 to 50 trucks per
day over weak subgrade!
From SDDOT Rural Road Design, Maint, & Rehab Guide
77

78. More on Gravel Quality
Same operator
Same road
Same day
Different gravel

79. Updates From the SDDOT/SDLTAP
Surface Gravel Study Project
Brookings Site Constructed in 2011

80. Reason for Project
• More than 50% of local roads in SD are unpaved –
managing them is a challenge!
• Biggest complaints from public are: rough condition
(generally from corrugation or “washboard” in
surface) and too much loose aggregate on the
surface makes it hard to control a vehicle.
• How critical is gravel quality to this and how does it
affect total cost of maintenance?

81. • Primary focus is on effect of gravel quality on
life-cycle cost of gravel road maintenance
• Three types of gravel used in study:
1. Substandard but commonly used – meets no
spec except top size control – one inch minus.
2. Barely meets SDDOT Gravel Surfacing Spec –
percent passing #200 sieve is low and/or
plasticity index (PI) at bottom of range at 4
3. Modified SDDOT Spec – higher minimums of
10% passing #200 sieve and PI at 7.
Focus of Test Project

82. Substandard
Gravel
SD Standard
Specification
Modified
Specification
Compacted and
Uncompacted
Sections
Compacted and
Uncompacted
Sections
Buffer Sections

83. One of the biggest challenges was finding
gravel that meets the modified SDDOT
Specification: “Shall have minimum plasticity
index (PI) of seven”. (Even higher minimum
was considered in project planning)

84. One way to meet modified spec – blend
different material from separate sources
This was done on one
section in Brookings Co
and one section in
Custer Co

85. Is this the future? More blending or “manufacturing” to
get high quality gravel – processing from a natural clay
source here:

86. Road mixing natural clay to get a high quality
surface gravel

87. Please
note this
area

88. Current Status of Project
• SDLTAP has accumulated photo documentation
on all sections over the past two years.
• Measurement and documentation has been done
on these distress types in 2012 & 2013:
1. Accumulation of loose aggregate (float)
2. Changes in top width from time of construction
3. Presence of corrugation (washboard) on surface
4. Change in roadway crown

89. The float test (loose aggregate)

90. Simply remove
loose aggregate
from a 10 inch
cross section,
weigh it and
convert that to a
one-mile section

91. Change in top-width is measured on traveled
way – hinge point to hinge point
XX ft.

92. Corrugation (washboard):
Hard to quantify in extent,
fairly easy to measure severity

93. Brookings Section – Loose Aggregate 2012
(Tons per mile)
Substandard
Compacted Uncompacted
Standard Spec
Uncompacted Compacted
Modified
Spec
405 tons
71 tons

94. Cooler, wetter season in
2013 – 2.94 inches of rain in
previous 20 days – most of
that in three days prior to
the last test.
Difference in 2012 & 2013 maintenance seasons:

95. Brooking Section – Loose aggregate 2013
0
20
40
60
80
100
120
140
160
180
200
Tons per mile (October 2013)
Tons per mile
(October 2013)
186 tons
16 tons

96. Loose aggregate comparison 2013 & 2012
0
50
100
150
200
250
300
350
400
450
Tons per mile
(October 2013)
Tons per mile
(October 2012)

97. 2014 Spring Measurement of Loose Aggregate
0
50
100
150
200
250
300
350
Substandard C Substandard UC Standard UC Standard C Modified C
6/20/2014 Measurements
Substandard
Compacted Uncompacted
Standard Spec
Uncompacted Compacted
Modified
Spec
44 tons
310 tons
118 tons

98. Corrugation (Washboard)
• No corrugation observed on any sections
meeting at least minimum standard
specification.
• However, substandard section had the
beginning of light corrugation only two days
after blade maintenance after nearly three
inches of rain.

99. Change in Roadway Surface Width
Constructed Width – 21.5 ft on all sections
Constructed Width – Modified Section
Current Width – Oct 2013
Constructed Width – Standard Spec Section
Current Width – Oct 2013
Constructed Width – Substandard Section
Current Width – Oct 2013
Current width ranges from 22 ft on modified section (top
bar) to 25.25 ft on substandard section (bottom bar)

100. Substandard section – aggregate has moved
outward over 4 ft since construction

101. Modified section has moved outward only six
inches since construction

102. View of Substandard section – 10-18-13

103. View of Modified section – 10-18-13

104. Does the modified section rut in wet weather?
No, virtually no rutting observed.

105. Any traffic on
this road?

106. Concluding Points
• Meeting basic SDDOT standard surface gravel
specification reduces loose aggregate by 1/3 to 1/2.
• Widest differential was in Brookings County near end
of corn harvest in 2012 with 405 tons of loose
aggregate on substandard section to only 71 tons on
modified section.
• No corrugation ever observed on standard or modified
material.

107. • Most interesting fact thus far: Brookings has done
blade maintenance up to four times on substandard
section to only once on modified!
• A negative aspect: we are getting a lot of push-back
from aggregate producers who would prefer to
produce as they always have – no close control of %
passing the #200 sieve and plasticity index.
Concluding Points (Con’t)

108. Feasibility of Dust Control
or Stabilization

109. $-
$20,000.00
$40,000.00
$60,000.00
$80,000.00
$100,000.00
$120,000.00
$140,000.00
$160,000.00
0 200 400 600 800 1000
ADT
AgencyCost($)
HMA
Blotter
Gravel
Linear (HMA)
Linear (Blotter)
Linear (Gravel)
Gravel Blotter HMA
Summary of gravel, AST and HMA surface
life cycle costs related to ADT – SDDOT Surface
Selection Criteria Study
Gravel – cost
effective to 150 ADT
AST (Blotter) – cost
effective to 650 ADT
HMA Pavement – cost
effective above 650 ADT
109

110. Cass County, ND Cement Treated Gravel

111. Excellent stability in the gravel layer
May 15, 2014 – cold, late spring in a slough area

112. Remarkable success with stabilized gravel in SD
A Chloride Stabilized Road Since 1998!
112

113. Portland Cement Railcar Offloading Facility
113

114. Less than 200 tons of gravel replaced in 14 yrs!
Carries up to 80 portland cement haulers
per day in addition to regular traffic.
114

115. Brief Coverage of Chloride Treatment Process
• Must have good surface gravel in place:
– Needs to meet surface specification (ND Class 13 or SD
Gravel Surfacing Specification)
– Prefer minimum four inches thickness on good base
• Gravel must be prepared well:
– Loosen the top one to two inches uniformly across the
surface.
– Gravel must be in a moist condition while preparing and
just prior to treatment.
• Apply chloride evenly and uniformly.
• Don’t use rollers too soon! (Sometimes not at all)

116. Bit-type cutting edges are excellent for
preparing surface

117. Excellent example – surface is loose and open
in moist condition

118. Don’t apply too much chloride in one pass –
watch for absorption

119. Second application being made after complete
absorption of first application

120. Case Study from Meade County, SD
Experience with Alternatives to
Paving
Information from:
Mr. Ken McGirr
Meade County Highway Supt
Sturgis, SD

121. • Elk Vale Road
– Located directly east and north of Rapid City
– Serves a growing area just off of exit 61 on
Interstate Highway 90
– Classification: Rural Major Collector
– Became impossible to maintain as gravel surface
121

122. Recent Traffic Count Breakdown
• Northbound
– 12/04/2012 299 total vehicles 22 trucks
– 12/05/2012 319 total vehicles 28 trucks
– 12/06/2012 317 total vehicles 22 trucks
• Southbound
– 12/04/2012 331 total vehicles 69 trucks
– 12/05/2012 339 total vehicles 92 trucks
– 12/06/2012 319 total vehicles 76 trucks
• Total*
– 12/04/2012 610 total vehicles 91 trucks
– 12/05/2012 658 total vehicles 120 trucks
– 12/06/2012 636 total vehicles 98 trucks
*Meade County count tallied over 700 vehicles in earlier count with 25% trucks
122
Average 635 vehicles per day and average 103
trucks per day (16% of total volume)

123. A difficult area for road management

124. Originally constructed in May, 2011
Excellent performance after first year
124

125. Close-up view of stabilized surface
125

126. Stabilization was done with .75 gal of liquid MgCl2
per sq yd mixed into top three inches (75 mm) of
good quality surface gravel layer
126

127. No significant loose aggregate and no
corrugation even on 7% grade.
127

128. No blade maintenance was done
between construction in summer
of 2011 and surface retreatment
in summer of 2012!
128

129. Phone call from citizen – “If you had
enough money to pave this road, why
didn’t you save enough to put striping
on it”
129

130. End of season condition assessment 10-24-13

131. Skid marks from recent incident

132. Observation– 2-29-14
Treatment done in May, 2013

133. A little about training
• A great need in our industry
–Management level
–Field supervisors
–Operators

134. Management Training
• Clear communication on expectations must
be conveyed to field staff.
• Does everyone have the same goals?
• Is management too preoccupied with the
primary roads?
• Gravel roads become very low priority and
consequently reach failed or near failed
condition before work is done?

135. Field Supervisor Training
• May not understand the right geometry needed
on a gravel road (different than pavement).
• Consequently do not know how to convey to
operators (in-house or out sourced) what is
needed for good maintenance.
• Supervisors and operators develop adversarial
relationship – the team breaks down!

136. Operator Training
• Too often no training given on desired
roadway shape (geometry) and bad habits
are developed.
• Little or no mentoring by skilled operators
who could communicate what they know.
• Great lack of training in our technical colleges
or trades training centers for this field.
• No recognition for doing a good job!

137. SD Recent Training Efforts
Administrative and Field Supervisor Training

138. Operator Training

139. Results:
• Positive Outcomes:
– Excellent attendance and participation
– Significant request for more training
– Operators and supervisors understand each other’s
positions much better
• Challenges:
– Lack of good training material
– Agencies want training very condensed and fast
– Very hard to find good trainers, especially for
operator level
– Hands-on field training is expensive

140. A new education
resource in the
US:
The Gravel Roads
Academy
Easy to find online
by doing a simple
search

141. Get ready to face the challenges of
maintaining gravel roads in the future!
Good Luck and Thank You!