Geosynthetics October/November 2019 - 44

Nature area drainage control with GCCM

FIGURE 4 Completed GCCM gutter

The selected GCCM could be used
for multiple functions and applications
besides armoring a drainage ditch,
including slope protection, weed control,
fire control, geosynthetic liner armoring, relining inverts of culverts, shoring line protection and more. The city
could inventory the material and then
use it when a need arose, especially when
extreme rainstorms occur, to minimize
erosion and water quality issues at unexpected locations throughout the city limits. The GCCM material can be delivered
to the site in large bulk rolls weighing
nearly 3,500 pounds (1,587.6 kg). The
rolls can also be supplied in batch or
person-portable sizes, which are less than
150 pounds (68.0 kg). The lighter rolls
can be transported by smaller equipment
and installed without large equipment
footprints. A summary of comparative
options is shown in Table 1.

Installation procedures for
concrete cloth GCCM at the
project site

FIGURE 5 The completed GCCM
presediment basin

Product
Turf Reinforcement Mat (TRB)

Minimum
Installation
Overall
Impermeable
Maintenance
Disturbance
Time
Cost
X

Riprap

Tied or Articulated Concrete Block Mats

Shotcrete/Poured Concrete

Fabric-Formed Concrete

X
X

Geosynthetic Concrete Composite Mat (GCCM)

The contractor initially graded the trail
to reverse the drainage toward the proposed trapezoidal gutter design (back
toward the toe of the slope). To minimize
excavation and construction time, the
contractor manufactured a steel template
to attach to the mini-backhoe and cut a
trapezoidal gutter that provided a flat
8 inches (20.3 cm) at the bottom and

a 1H:1V side slope with a flat 6 inches
(15.2 cm) on top. The flat bottom was
selected to allow for easy maintenance
using a flat shovel to remove any silt,
leaves or debris compared to a typical
V-gutter shape. Once the gutter was cut,
the contractor crews deployed the GCCM
and laid it within the gutter. The crews
used and deployed bulk rolls along the
gutter, which minimized the number of
overlaps of the GCCM fabric. At overlaps, crews used construction caulk or
adhesive and screws. Once the GCCM
was installed, the crew used a water tank
attached to a pickup truck with a pump to
hydrate it. The completed gutter is shown
in Figure 4.
After the gutters were completed, the
crews used the GCCM to construct a
presediment basin. The completed basin
can be seen in Figure 5.
The GCCM was also used for the construction of midslope interceptor weirs
to slow down sheet and concentrate flow
from the steep hillside slopes to minimize
erosion issues. Gravel geotextile bags
were stacked three courses high, and the
GCCM was draped over to protect the
geotextile bags from UV and abrasion to
create a long-term structure that could
be removed with minimal effort. The
weirs are shown in Figure 6. The city
used to replace gravel bags and/or fiber
rolls annually and hoped that the use of a
GCCM would eliminate the need for this
annual chore.

Geosynthetics | October November 2019

Safety Hydraulics

Erosion
Water
Protection Quality

Geosynthetics October/November 2019

Table of Contents for the Digital Edition of Geosynthetics October/November 2019