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| 5.8. Maintenance
of Dirt and Gravel Roads |
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Over 1.6 million miles of unpaved roads (53 percent
of all roads) are unpaved. Many of these roads will
remain unpaved due to very low traffic volume and/or
lack of funds to adequately improve the subgrade and
base before applying pavement layer(s). In some countries,
economic constraints mean gravel roads are the only
type that can be provided.
Dirt and gravel roads represent a very small percentage
of roadways maintained by state DOTs in almost all
cases; counties and federal agencies manage the large
majority of the dirt and gravel roads in the United
States. Nevertheless, a few state DOTs have become
very involved in managing dirt and gravel roads and
have developed environmental stewardship practices
and partnerships that may be useful for other state
DOTs.
General practices for pollution prevention from dirt
and gravel roads include:
- Stabilize exposed soil areas to prevent soil from
eroding during rain events. This is particularly important
on steep slopes.
- For roadside areas with exposed soils, the most
cost-effective choice is to vegetate the area, preferably
with a mulch or binder that will hold the soils in
place while the vegetation is establishing. Native
vegetation should be used if possible.
- If vegetation cannot be established immediately,
apply temporary erosion control mats/blankets; a comma
straw, or gravel as appropriate.
- If sediment is already eroded and mobilized in
roadside areas, temporary controls should be installed.
These may include: sediment control fences, fabric-covered
triangular dikes, gravel-filled burlap bags, biobags,
or hay bales staked in place.
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| 5.8.1
Partnerships to Identify and Address the Most Pressing
Erosion Problem Areas |
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The Pennsylvania
Task Force on Dirt and Gravel Roads is a cooperative
effort between PennDOT and several other state and
private agencies to improve the environmental quality
of Pennsylvania's streams and waterways. PennDOT started
working with Trout Unlimited in the early 1990s to
mobilize volunteers to identify sedimentation problem
areas from eroding roads and shoulders and areas of
adverse impacts to streams. Initial efforts concentrated
on Pennsylvania' protected watersheds, designated
as either High Quality (HQ) or Exceptional Value (EV),
and including drinking water reservoirs and cold water
fisheries. Trout Unlimited's volunteer effort culminated
in the identification of over 900 sites, which became
the basis for the Dirt and Gravel Road Pollution Prevention
Program. In 1999-2000, a statewide committee followed
up with a statewide inventory and assessment of all
17,000+ miles of Pennsylvania's dirt and gravel road
network. Conducted by County Conservation Districts,
this effort identified more than 9600 specific pollution
sites impacting more than 3,000 miles of roadway.
All 9600+ worksites were mapped, rated (on a 12-step,
100 point scale) and recorded in GIS program files.
Top priority in the first three years was given to
pollution "trouble spots" identified in
watersheds protected as "exceptional value" and "high
quality." As of 2000-01, a new allocation formula
was used to distribute funding to affected communities
statewide, with verified pollution sites on unpaved
roads. Pennsylvania's 65 Conservation Districts administer
the program at the county level with annual allocations
from the State Conservation Commission. With the help
of a local Quality Assurance Board (QAB), they:
- Work directly with applicants to develop plans
for projects
- Assist with logistics of project work whenever
possible
- Keep track of records of projects in their County
using GIS system
- Develop a prioritization ranking incoming applications
through the QAB
- Decide which project will be funded each year,
through the QAB, and
- Conduct project inspections after site work is
completed
To be eligible to apply for funding, an official
form a municipality must attend a free 2-day training
on environmentally sensitive maintenance for unpaved
roads that explains basic environmental principles
and introduces new techniques and ideas in unpaved
road maintenance. The Center for Dirt & Gravel
Road Studies at Penn State conducts "Environmentally
Sensitive Maintenance," a 2-day course that includes
modules on drainage, road maintenance techniques, erosion
prevention & sediment control, bank stabilization,
roadside vegetation management, and grant procedures.
In assessing progress toward addressing priority
erosion control areas statewide, the program tracks:
- Drainage Outlets Stabilized (Sq Ft)
- Eroded Ditch Stabilized (Sq Ft)
- Road Bank Stabilized (Sq Ft)
- Stream Bank Stabilized (Sq Ft)
- Fabric Used (Sq Ft)
- Stream Culverts Replaced (#)
- Cross Pipes Added (#)
- Road Stabilized (Sq Ft)
- Vegetative Management (Sq Ft)
- Length of stream culverts replaced (Ft)
- Length of cross-pipes added/replaced (Ft)
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| 5.8.2
Tools and Techniques for Erosion Reduction/Prevention |
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PennState's Dirt and Gravel Roads Center provides
extensive resources and program information for managing
dirt and gravel roads. The Center provides an extensive
Dirt & Gravel Roads training program that is available
upon request. Technical bulletins available on-line
include:
The Center's list of environmentally
acceptable products for petroleum emulsion dust
suppressant, acrylic polymer dust suppressant, road
fill materials, soil amendments is also available
on-line.
A variety of other technical resources are available
from federal agencies, teams, and other states in some
instances. The Local Technology Assistance Program
maintains a listing which includes the following of
potential interest to state DOTs: [N]
South Dakota's Gravel
Roads Maintenance and Design Manual is a comprehensive
manual available in both html and pdf formats
that addresses most issues that deal with gravel road
maintenance. The practices included in the manual
are available via the links below:
Example
14 : South Dakota DOT Gravel Roads Maintenance and
Design Manual Sections
Section
I: Routine Maintenance and Rehabilitation
Understanding
Road Cross Section
Routine
Shaping Principles
- Operating Speed
- Moldboard Angle
- Moldboard Pitch
- Motorgrader Stability
- Articulation
- Windrows
- Crown
- Road
Shoulder
- High Shoulders ( Secondary Ditches )
- Causes of High Shoulders
- Recovering and Spreading on Roadway
- Breaking up Sod and Vegetation in Recovered
Material
- Pulling and Covering
- Benefit of Mowing
- Gravel
Road Rehabilitation
- Reshaping Surface and Shoulder
- Reshaping Entire Cross Section
- Erosion Control
- Areas
of Concern
- Dealing with Corrugation
- Intersections
- Intersection with Paved Roads
- Bridge Approaches
- Superelevation in Curves
- Rail Crossings
- Driveways
- Cattle Guards
- Soft and Weak Subgrade
- Section
II: Drainage
- Ditches
- Culverts and Bridges
- Underdrains
Section
III: Surface Gravel
- What is Good Gravel?
- Difference in Surface Gravel and Other Uses.
- Good Gradation
- Benefit of Crushing
- Recycled Asphalt
- The Benefit of Testing Aggregates
- Reasons for Testing
- Sampling
- Sieve Analysis
- Fines and Plasticity Index
- Reduced Blading and Maintenance Costs
- Process for Obtaining Good Gravel
- Establish Specifications
- Communicate with Suppliers
- Handling Gravel.
- Pit/Quarry Operations
- Loading from Stockpiles
- Roadway Preparation
- Calculating Quantity
- Hauling and Dumping
- Windrowing, Equalizing and Spreading
Section
IV: Dust Control/Stabilization
- Types of Stabilizers
- Chlorides
- Resins
- Natural Clays
- Asphalts
- Soybean Oil
- Other Commercial Binders
- Benefits of Stabilization
- Reduced Dusting
- Reduced "Whip Off" of Aggregate
- Reduced Blade Maintenance
- Application Tips
- Need for Good Surface Gravel
- Road Preparation
- Applying the Product
- Optimum Moisture
- Test Sections
Section
V: Innovations
- Changes in Gravel Maintenance
- Changing Conditions—Equipment, Trucks,
Cars
- New Innovations
- Innovative Equipment and Methods
- Windrow Pulverizers
- New Cutting Edges
- Shouldering Disks
- Grader-Mounted Dozer Blade
- Grader-Mounted Roller.
- Rakes
- Other Tractor-Mounted Blading Devices
Summary
References
Appendix
A : Gravel Road Thickness Design Methods
Appendix
B: Gradation and P.I. Determination
Appendix
C: Quantity Calculations
Appendix
D: When To Pave a Gravel Road
Appendix
E: Walk-around Grader Inspection
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to Section 6.1 » |
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