Erosion and sediment control is a critical maintenance
activity and should not only be considered on previous
land-disturbing activities such as road construction,
but also on any roadside land-disturbing activity,
including slide or flood emergencies. Best management
practices are available to effectively treat most yards,
facilities, and roadside erosion and sediment problems.
Consequently, maintenance staff should become familiar
with their DOT's Erosion and Sediment Control Manual.
BMPs are available for perimeter, surface, slope, ditch,
channel, and inlet and outlet protection, among others.
Revegetation of disturbed or bare areas is the key
component to long-term erosion and sediment control
and should be used in most instances. Erosion and sediment
control measures are used for all areas where maintenance
activities involve clearing, grubbing, grading or excavating.
Information on environmental stewardship practice
in erosion and sedimentation control and links to selection
guidance, drawings, and implementation are included
in the Design and Construction chapters; however, some
basic environmental stewardship practices for erosion
control in maintenance include the following:
- Use temporary vegetation to provide immediate ground
cover until permanent landscaping is in place. It
is desirable to re-seed and mulch any disturbed areas
at the end of the day.
- Other "positive" erosion control measures
(such as silt fence , check dam, etc.) should be installed
prior to commencing work and left in place and maintained
until the site is stabilized
- Areas should be re-vegetated with native seed mixes
that require minimal care
- Temporary structural erosion control measures should
be installed when cleaning culverts or cleaning ditches
that discharge into streams, wetlands, lakes or ponds
- When cleaning ditches, temporary check dams should
be used wherever they are necessary and placed so
that the crest of the downhill dam is at the same
elevation of the toe of the uphill dam.
- Check dams should be left in place until the ditch
is re-vegetated.
- Temporary sediment traps should be placed at the
inlet of a culvert that drains into a stream, wetland
or other water body. Sediment traps should be constructed
by excavating an additional 1/3 meter (one foot) below
the ditch invert for a distance of six meters (20
feet).
- Temporary turbidity curtains should be placed around
culvert outlets in low water velocity situations for
additional protection at, or close to, very sensitive
sites, such as drinking water supplies, angler parking
areas, or swimming facilities. Turbidity curtains
should only be installed parallel to the shoreline
and should never be placed across streams.
- After the project site is stabilized, any accumulated
sediment should be removed before removing check dams
or turbidity curtains.
- To improve habitat and reduce erosion, consult
with the environmental staff regarding incorporation
of appropriate soil bioengineering practices, such
as live willow cuttings/ stakes/posts and live willow
wattles to stabilize disturbed and/or eroding stream
banks.
- Sediment control structures should not be placed
in streams
- The smallest practicable work zone is cleared to
minimize erosion
- Length and steepness of slopes should be minimized.
Place terraces, benches, or ditches at regular intervals
on longer slopes.
- Maintain low runoff velocities in channels by lining
with vegetation riprap, or using check dams at regular
intervals, in addition to minimizing steepness and
slow length.
- Trap sediment on-site. Many conventional BMPs are
available, in addition to always evolving new ones.
DOT environmental staff, Roadside Managers, or Landscape
Architects should be consulted for more detail or if
problems arise. Links to existing erosion and sediment
control resources and a brief overview of environmental
stewardship practice related to erosion and sediment
control is included under section 4.6, Erosion and
Sedimentation Control.
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| 10.12.1
Evaluating and Ranking Roadside Erosion Control Problem
Areas |
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| PennState's
Dirt & Gravel Roads Center System for Identifying
and Ranking Erosion Control Problem Areas
Penn State University operates a Dirt & Gravel
Roads Center with DOT support. The center has developed
a system to identify and rank erosion control problem
areas, based on the following criteria:
- Ranking of road sediment in stream: None, Slight,
Moderate, or Severe/Stream Encroachment.
- Wet site conditions: Dry, Saturated Ditches, Roadside
Springs, Flow in Ditches, Saturated Base.
- Road surface material: Hard Gravel, Mixed Stone,
Soft Stone/Dust, Stone/Dirt/Dust, and Severe Dust.
- Road slope/grade: <10 percent, 10-30 percent,
or >30 percent.
- Road shape: Good, Fair, or Poor.
- Distance to stream: >100 ft., 50-100 ft., <50
ft. crossing.
- Slope to stream: <30 percent, 30-60 percent, >60
percent.
- Outlet to stream: None, Near Stream, Directly into
Stream.
- Outlet bleeder stability: Stable, Moderate, Unstable.
- Road ditch stability: Stable, Fair, Poor, Unstable.
- Road bank stability: Stable, Fair, Poor, Unstable.
- Average canopy cover: Moderate, Minimal, Heavy.
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to Section 10.13 » |
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