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Geotechnical News September 2011
WASTE GEOTECHNICS
ternative materials such as low-density
polyethylene (LDPE) geomembranes
are widely used for daily and interim
covers. The improved operation prac-
tices at second-generation controlled
landfills have certainly resulted in a re-
duction in leachate production.
Leachate production in the southern
cities of China is still more than expect-
ed due to the high initial water content
of the MSW. High leachate mounds are
still observed at many of the second-
generation controlled landfills in Chi-
na. Field evidence indicates that the de-
velopment of high leachate mounds is
mainly attributed to the clogging of the
bottom LDCS. Maintenance of LDCS
such as retro-flushing of collection
pipes during landfill operations has not
been practiced in China. It appears that
the LDCS at landfills in China are more
susceptible to high leachate produc-
tion as well as heavy mass loadings of
leachate. The high leachate mounds in
the landfills tend to cause slope failures
in landfills, increase risks of environ-
mental pollution, and inhibit landfill
gas collection. High leachate mounds
within landfills appear to be one of the
major technical difficulties discourag-
ing landfill gas recovery in China.
Technical Challenges Associated
with MSW Landfills
Landfilling will remain the dominant
disposal method for MSW in China
for the foreseeable future. Further
development of controlled landfills
in China will encounter the following
challenges:
1. Stability and safety of the land-
fills with a continuous increase in
height: Many landfills in China
have reached a height of 60 m and
will reach a height of over 100 m
in the future. In recent years, there
has been an increase in the num-
ber of landfill failures, including in
Chengdu, Shanghai, Shenzhen, and
Xian. Most of the landfill failures
were triggered by a high leachate
mound. With an increase in landfill
height, the stability problem will
become more critical if there are no
effective solutions to control high
leachate mounds.
2. High leachate production and treat-
ment: High leachate production
and high mass loadings result in ex-
pensive leachate treatments. Many
landfills are not able to afford the
high cost of treatments required to
meet the new leachate discharge
standard in GB 16889-2008.
3. Land shortage and increased land-
fill capacity: Many cities lack land
for disposing increased masses of
waste. Increasing the capacity of
existing landfills is an effective but
temporary solution. This is usu-
ally done by expanding the existing
landfill, increasing the slope angle,
and accelerating waste decomposi-
tion and settlement. Landfill stabil-
ity should be assured when imple-
menting these measures.
4. Recovery of landfill gas: Collection
and recovery of landfill gas can re-
duce greenhouse gas emissions and
provide energy (and income) for
landfill operation. The efficiency
of gas collection in China is lower
than 40% due to the high leachate
mounds in landfills. Breakthrough
technologies addressing this diffi-
culty will encourage the recovery
of landfill gas at the 366 controlled
landfills in China.
5. Control of soil and water pollution
by leachate: Different degrees of
underground pollution have been
reported at many landfills in China.
The major challenge of this issue
lies in the durability of barriers,
especially when the barriers are
subjected to a high leachate head.
In addition, quality assurance and
control for the construction of bar-
riers should be made more strin-
gent.
6. Closure, post-closure care, and re-
use of closed landfills: There are
thousands of simple dumps requir-
ing proper closure as well as long-
term post-closure care. Financial
assurance for this activity has not
yet been considered in munici-
pal budgets. Financial sources for
closure and post-closure activi-
ties may come from land reuse of
closed landfill sites. Land reclama-
tion activities will encounter diffi-
culties associated with post-closure
settlement and environmental im-
pacts from the landfills.
Acknowledgements
The authors would like to acknowledge
the research grants (50878194;
51010008; 51009121) provided by the
National Natural Science Foundation
of China (NSFC) and the Science and
Technology R&D Program of Suzhou
(520324).
References
Chen, Y.M., and Zhan, L.T. (2007):
Geoenvironmental issues associ-
ated with landfills of municipal
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ceedings of 13rd Asian Regional
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Dong, Y.X. (2009): The status of engi-
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Y.M. Chen, Professor, Department of
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