States Focus on Erosion Control
in Construction and Maintenance Activities
Triangular silt barriers, geotextile
filter bags, and concrete blocks are just some of the products and
ideas State highway agencies are using to better control soil erosion
and sedimentation resulting from highway construction projects. The
roadbuilding process often disturbs soil, which is then vulnerable
to being washed downstream when it rains, causing a build-up of soil
and other matter in waterways that is known as sedimentation. Excessive
sedimentation can destroy fish habitat; clog streams, storm drains,
and culverts; and pollute waterways, among other problems.
Since 1987, when an amendment to the Clean Water Act more broadly
defined point source pollutants to include stormwater discharge from
such industrial activities as construction, an increased number of
environmental regulations have addressed the mitigation of highway
runoff. In 1999, the U.S. Environmental Protection Agency (EPA) issued
a final rule expanding its National Pollutant Discharge Elimination
System stormwater program to include the regulation of construction
sites that disturb one to five acres of land.
With the increased emphasis on erosion control resulting from the
Clean Water Act and the 1991 Intermodal Surface Transportation Efficiency
Act legislation, States are implementing a variety of new control
methods. The Georgia Department of Transportation (DOT), for example,
has started using geotextile filter bags to trap silt when pumping
water from sediment basins and bridge footings. The bags are usually
placed on a stone or gravel bed that has been sloped to ensure the
filtered water will exit at the desired location. "We have used
the filter bags on four bridge projects so far and they have worked
out well," says David Graham of the
Georgia DOT. For more information, contact Graham at 404-656-5306
(email: david.graham@dot.state.ga.us).
Delaware DOT is using what is known as a skimmer dewatering device
to better trap soil in sediment basins. The device is a floating riser
that attaches to the outlet by way of a flexible pipe. Compared to
the perforated riser used previously, the floating riser better traps
sediment at the surface of the basin. "It works really well,"
says Vince Davis of the Delaware DOT. "It is a walk-away device
and relatively maintenance free." For more information, contact
Salvador Palalay at Delaware DOT, 302-760-2188 (email: spalalay@mail.dot.state.de.us).
size="1"> Georgia
DOT is using the geotextile silt filter bags shown above to trap silt
when pumping water from sediment basins and bridge footings.
The Illinois DOT has found success
using articulated block mats, which are concrete blocks held together
with cables. The blocks can be used for a number of erosion control
applications, such as stabilizing slopes or as channel or ditch liners.
Illinois has used them to control high velocity runoff in river bottom
wetlands and as work pads at bridge construction sites. The block
mats are laid on the river bed, so machines can run across them without
kicking up too much silt. Richard Nowack of the Illinois DOT also
reports success in using triangular silt barriers, which are employed
to remove suspended particles from drainage water. The barrier consists
of a permeable urethane foam core surrounded by a woven geotextile
fabric and fixed to the ground with wire staples. For more information,
contact Nowack at 217-785-2943 (email: nowackrj@nt.dot.state.il.us)
or John L. Rowley at 217-785-2834 (email: rowleyjl@nt.dot.state.il.us).
Several States, including Georgia and North Carolina, are also experimenting
with using the substance polyacrylamide (PAM) to accelerate the settlement
of sediments. PAM, which comes in powder, emulsion, and gel-block
form, binds small soil particles together so as to accelerate the
settlement of suspended particles in sediment traps and ponds. For
more information on PAM test projects in Georgia, contact James Magnus
at the Georgia DOT, 404-656-5306 (email: james.magnus@dot.state.ga.us).
For more information on North Carolina's PAM study, contact Byron
Moore at North Carolina DOT, 919-733-2920 (email: bjmoore@dot.state.nc.us).
Through using the range of new erosion control methods outlined above,
States are minimizing the impact of construction and maintenance operations
and mitigating sediments and erosion concerns, resulting in not only
better roads but a better environment.
| To assist State highway
agencies in implementing erosion and sediment control measures
and clarify FHWA and EPA requirements in this area, FHWA
and EPA are jointly developing a National Highway Institute
course, "Design and Implementation of Erosion and Sediment
Control." Intended for designers, contractors, and
inspectors, the course will address such topics as current
regulatory requirements, erosion and sediment control principles,
and management techniques for controlling erosion and sedimentation
on highway construction and maintenance operations. The
pilot for the course is tentatively scheduled to be held
in late summer or early fall of this year. For more information,
contact John Perry at FHWA, 202-366-2023 (fax: 202-366-9981;
email: johna.perry@fhwa.dot.gov). |
|
Other
articles in this issue:
In
brief
States
focus on erosion control in construction and maintenance activities
Recycle
Texas: A success story
Thinking beyond the pavement with context sensitive
design
Highway Technology Calendar
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