Geosynthetics July/August 2024 - 20

Navigating landfill leachate requirements with geosynthetics
In Black Hills, S.D., Gilt Edge Mine,
FIGURE 3 Clarksburg Landfill saw significant material and labor cost reductions through the use of
an AGRU Integrated Drainage System (IDS).
FIGURE 4 The Ruby Waste Rock Repository
contained over 65 acres of waste from the
Gilt Edge Mine. A robust closure cap with
drainage was necessary to reduce acid rock
drainage (ARD) from contaminating the
local water supply.
AGRU lining systems for
leachate management
An essential component of any leachate
management plan is managing infiltration.
Below is a summary of an AGRU
case study demonstrating the successful
implementation of closure solutions
to significantly reduce infiltration and,
therefore, help reduce leachate generation.
The second AGRU case study details
how a cap was installed in a mining waste
pile to protect against water infiltration.
After the Clarksburg, W. Va., landfill
decommissioned, the city initiated the
construction and design of a remedial
landfill closure cap. To manage costs,
the city chose a design incorporating
HDPE geomembrane, double-sided geocomposites
and geotextiles. The chosen
approach utilized AGRU IDS, a Subtitle
D-compliant closure and containment
solution, in conjunction with a geocomposite
venting system. The project was
completed in 2019. The landfill cap is
expected to reduce infiltration and provide
environmental protection throughout
its service.
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Geosynthetics | Summer 2024
operating since 1876, accumulated
approximately 20 million cubic yards
of waste material, leading to acid rock
drainage (ARD) and groundwater contamination.
To provide adequate protection
against water infiltration, a cap
system was designed using a structured
geomembrane with an integral drain
layer. This barrier would be installed over
the 65 acres (26.3 hectares) of waste rock.
One challenge with this large area was
controlling the stability of the cap system
along with the flow of water along the
slope, which extended longer than 1,804
feet (550 m). A series of nine 8-meter side
slope benches were created. These drainage
ditches can control the water flow for
even 100-year storm events.
The final cover system comprised six
layers. At the top was processed topsoil
seeded with native grasses. Beneath that
was a 900 mm (.9 m) layer of rock and
soil. A 450 mm (.45 m) layer of crushed
25 mm (.025 m) rocks separated the soil
from a 10 oz/yd2 grade nonwoven geotextile.
The last two layers comprised
an 80 mil LLDPE structured geomembrane
with an integrated drain layer.
The ditches were lined with a geocomposite
lining system with a high-grade
geosynthetic material. This project
was completed in 2003. The approach
offered significant material and labor
cost reductions by not having to purchase
and install a separate geonet drain
layer thanks to AGRU IDS.
Summary
Geosynthetics are essential in helping
manage landfill leachate to mitigate environmental
and public health risks associated
with hazardous materials.
References
Li, Q. et al. (2023). " Challenges and engineering
application of landfill leachate concentrate treatment. "
Environmental Research, 231.

Geosynthetics July/August 2024

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