Geosynthetics June/July 2023 - 44

FINAL INSPECTION
GEOWEB® Slope Protection
System provides transmission
line stabilization solution
T
ransmission lines are integral to supplying power to homes and businesses
throughout the country. Confronted with variable terrains, geohazards, and
other site complications, transmission line construction projects must contend with
a wide range of complexities, including the extreme challenge of traversing mountainous
regions. Often at these locations, the hillside needs to be benched to create
a level pad for the electrical transmission line tower foundations. If not properly
mitigated, the cutting of these slopes can lead to erosion, potentially endangering
the long-term stability of the towers.
A major U.S. electric utility company encountered these challenging terrains
on three of its towers on a transmission line running through the Appalachian
Mountains near Baileysville, W.V. Parts of the tower pads were originally created
using previously excavated material, but surficial sloughing at two of the sites
occurred due to the steep slope angles and loosely placed materials. At the third
location, similar issues arose with added complications due to water flow over the
bench, which caused tension cracks along the steepest part of the bench.
To address these issues, the project engineer chose to incorporate the GEOWEB
TOP The GEOWEB® Soil Stabilization
System (geocells) provides vegetated slope
protection solution for three Appalachian
Mountain transmission towers.
BOTTOM Nine days after hydroseeding, the
GEOWEB Slope Protection System is covered
in lush vegetation, protecting against erosion.
Photos courtesy of Presto Geosystems.
Slope Protection System into the project design, citing the long-term erosion protection
and resilience as the main reasons. Using Presto Geosystems' free project
evaluation service, the project engineer reached out to the Geosystems design team
for assistance with product and anchoring selection. Prior to placing the GEOWEB
system at each location, the contractor, Cook's Excavating LLC, had to excavate the
slide material and replace it in 8-inch (20.3-cm) compacted lifts.
The area of concern at the first structure location consisted of 2:1 (26.5°) slopes
PROJECT HIGHLIGHTS
TRANSMISSION LINE
STABILIZATION SOLUTION
LOCATION
Baileysville, W.V.
GENERAL CONTRACTOR
Cook's Excavating
GEOSYNTHETIC PRODUCT
GEOWEB® Soil Stabilization
System (geocells)
GEOSYNTHETICS MANUFACTURER
Presto Geosystems
44
Geosynthetics | June July 2023
with a maximum vertical height of 55 feet (16.8 m) (123 foot [37.5 m] slope length).
The recommended solution was GW30V6 (6 inch [15.2 cm] depth) geocell filled
with topsoil, anchored with three TP-225 tendons (polyester strap with 5,100 pound
[ 2,313 kg] break strength) per panel, and an ATRA® Tendon Clip tied to the tendons
every sixth cell downslope. At the crest, the tendons were tied to a 6 inch (15.2 cm)
diameter PVC pipe buried 4 feet (1.2 m) below grade.
At another structure location, the area of concern consisted of 50 foot (15.2 m)
tall slopes at a 1.2:1 slope angle (40°), creating 78 foot (23.8 m) slope lengths. The
recommended solution at these two locations was again GW30V6 filled with topsoil.
Due to the increased slope angle, six TP-225 tendons were used per panel, with an
ATRA Tendon Clip every sixth cell downslope. At these locations, the tendons were
tied to an 8 inch (20.3 cm) diameter PVC pipe buried 6 feet (1.8 m) below grade.
After installation, the slope was hydroseeded with a special seed blend supplied
by the contractor, with nearly full vegetative cover just nine days after the hydroseeding.
The GEOWEB Slope Protection System provided a structurally stable
environment for topsoil and sustainable vegetation through a structured network
of interconnected cells. The 3D GEOWEB system confined and reinforced the
vegetated upper soil layer, thereby increasing its resistance to erosive and sliding
forces, and reducing its susceptibility to surficial sloughing for improved longterm
slope protection. G

Geosynthetics June/July 2023

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