Geosynthetics February/March 2023 - 8

Q &
LANDFILL GAS
EMISSIONS MODELING
THE GEOSYNTHETIC
INSTITUTE ANSWERS
YOUR QUESTIONS
gmatechline@textiles.org
View past questions and answers
at geosyntheticsmagazine.com/
category/gma-techline.
Email gmatechline@textiles.org anytime
for fast, free, direct technical answers.
Q: I'm writing to see if you are aware of any
research on landfill gas (LFG) emissions
modeling through various geomembranes,
particularly for temporary covers?
A: Landfill gas modeling is the practice of
forecasting gas generation and recovery
based on past and future waste disposal
histories and estimates of collection system
efficiency. It is an important step in the
project development process because it
provides an estimate of the amount of
recoverable LFG that will be generated
over time. LFG modeling is performed for
regulatory and non-regulatory purposes.
Regulatory applications of LFG models are
conducted for landfills in the United States
to establish the requirements for installation
and operation of the gas collection and
control system. In short, geomembranes
work well as major components of these
control systems. There are many references
for LFG control using geomembranes, even
as temporary covers. I strongly recommend
the 2020 paper by Y. Feng, M. Mausavi and
J. Eun " Field Monitoring of Landfill Gas
Emissions through Intermediate Cover
with Co-Extruded EVOH Geomembrane in
an Operating Landfill, " presented at ASCE's
GeoCongress held in Minneapolis, Minn.
A
GMA TECHLINE
MODERATED BY
George R. Koerner
OVERLAP SEAM SPECIFICATIONS
FOR GEOTEXTILE SEPARATORS
Q: What is the typical overlap for a geotextile
used as a separator in a highway project?
A: This is a very simple question requiring
an involved answer. Overlap seam
specifications for geotextile separators are
all over the place depending on material
type and application. It is best to check
the plans and specification, consult the
project engineer for details or check the
manufacturer's recommendations. Note
that if you install an overlap " too small, " the
mistake is not reversible. With the above
written, there are general rules of thumb.
The typical overlap for a geotextile used
as a separator on " firm " subgrade (i.e., CBR
>2) is 12 to 18 inches. The overlap for a
geotextile separator on " soft " soil subgrade
(i.e., CBR < 2) is 24 to 36 inches. However, in
addition to the overlap width, one needs to
shingle the overlap correctly plus push the
backfill in the right direction. This discussion
takes a nasty turn when considering curves.
In such cases, the geotextile is either
pleated or overlapped. I would strongly
recommend consulting Propex Operating
Co. LLC's " GEOTEX Installation Guidelines for
Separation and Stabilization. " It is available
online and is excellent.
8
Geosynthetics | February March 2023

http://www.geosyntheticsmagazine.com/

Geosynthetics February/March 2023

Table of Contents for the Digital Edition of Geosynthetics February/March 2023

Geosynthetics February/March 2023 - Cover1
Geosynthetics February/March 2023 - Cover2
Geosynthetics February/March 2023 - 1
Geosynthetics February/March 2023 - 2
Geosynthetics February/March 2023 - 3
Geosynthetics February/March 2023 - 4
Geosynthetics February/March 2023 - 5
Geosynthetics February/March 2023 - 6
Geosynthetics February/March 2023 - 7
Geosynthetics February/March 2023 - 8
Geosynthetics February/March 2023 - 9
Geosynthetics February/March 2023 - 10
Geosynthetics February/March 2023 - 11
Geosynthetics February/March 2023 - 12
Geosynthetics February/March 2023 - 13
Geosynthetics February/March 2023 - 14
Geosynthetics February/March 2023 - 15
Geosynthetics February/March 2023 - 16
Geosynthetics February/March 2023 - 17
Geosynthetics February/March 2023 - 18
Geosynthetics February/March 2023 - 19
Geosynthetics February/March 2023 - 20
Geosynthetics February/March 2023 - 21
Geosynthetics February/March 2023 - 22
Geosynthetics February/March 2023 - 23
Geosynthetics February/March 2023 - 24
Geosynthetics February/March 2023 - 25
Geosynthetics February/March 2023 - 26
Geosynthetics February/March 2023 - 27
Geosynthetics February/March 2023 - 28
Geosynthetics February/March 2023 - 29
Geosynthetics February/March 2023 - 30
Geosynthetics February/March 2023 - 31
Geosynthetics February/March 2023 - 32
Geosynthetics February/March 2023 - 33
Geosynthetics February/March 2023 - 34
Geosynthetics February/March 2023 - 35
Geosynthetics February/March 2023 - 36
Geosynthetics February/March 2023 - 37
Geosynthetics February/March 2023 - 38
Geosynthetics February/March 2023 - 39
Geosynthetics February/March 2023 - 40
Geosynthetics February/March 2023 - 41
Geosynthetics February/March 2023 - 42
Geosynthetics February/March 2023 - 43
Geosynthetics February/March 2023 - 44
Geosynthetics February/March 2023 - Cover3
Geosynthetics February/March 2023 - Cover4
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https://www.nxtbook.com/ata/geosynthetics/geosynthetics-june-july-2023
https://www.nxtbook.com/ata/geosynthetics/geosynthetics-april-may-2023
https://www.nxtbook.com/ata/geosynthetics/geosynthetics-february-march-2023
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https://www.nxtbook.com/ifai/geosynthetics/geosynthetics-june-july-2021
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