Waste Containment
Craig H. Benson, PhD, PE
Geo Engineering Program
University of Wisconsin-Madison
NSF Workshop on Emerging Geoenvironmental
Technologies for Pollution Control and Remediation
Where Did We Come From?
Uncontrolled waste disposal is birthplace of
geoenvironmental engineering
Impacts on Policy
• Remediation of uncontrolled sites (CERCLA)
• Implementation of policy and technology criteria
for waste containment (RCRA)
- Hazardous waste containment (Subtitle C)
- Non-hazardous waste containment (Subtitle D)
Key Elements of RCRA
• Definition of acceptable waste types
(hazardous vs. non-hazardous, liquid
wastes, etc.)
• Development of criteria for containment
technology
Containment Technology
• Liners
– clay liners
– geomembranes
– composite liners
• Covers
• Leachate collection systems
Where we are …
Modern engineered containment facilities
A Success Story
• Effective Waste Containment
- virtually eliminate leakage
- reduce mass transport to very low rates
- highly protective of environment in near term
• Effective Liquid Control
- leachate collection systems
- leachate treatment systems
• Mature technology (top of the learning curve)
Do we have all the problems licked?
Exposed Vertical face
clay liner of solid waste
ent
vem
Mo
Massive slide and liner failure at Metro Landfill, Franklin, WI
Emerging Research Issues
Questions on Existing Technology:
• Long-term risks of ‘dry tomb’ landfilling
• Long-term post closure (how long? when do we quit?)
• VOC transport (are liners effective?)
• Alternative materials (new clays, geomembranes,
nanocomposites)
• Non-destructive testing and monitoring methods
• Long-term field data on performance
Emerging Research Issues
Currently Emerging Technologies:
• Bioreactor landfills (liquid collection and distribution,
degradation rate and effectiveness, settlement)
• Mechanical and hydraulic properties of wastes
• Alternative covers
• Reactive liners (can we make transfer PRB technology to
liners?)
• Performance- based design vs. regulatory engineering
• Sensors and remote monitoring systems for cost-effective
long-term stewardship
Remaining Research Issues
Other Waste Forms:
• Radioactive wastes (1000 yr lifespan, or 200 yr if
practical)
• Mining wastes (very strong liquids, oxygen
transport)
• Agricultural wastes (factory farms, mad cow,
chronic wasting disease)
Emerging Research Issues
In Situ Containment:
• Verification of effectiveness of walls and
PRBs
• Emplacement and verification of in situ
floors
Emerging Research Issues
Other important themes:
• Dealing with uncertainty, quantifying risks,
and addressing risk in design
• Sustainable practices (re-use rather than
permanently landfill)
• Long-term field assessments to evaluate
whether we really understand and can
predict how waste containment systems
behave.
Emerging Educational Issues
• We have done a good job developing
curricula dealing with containment issues
• Too much focus on practical physical
aspects; not enough focus on
fundamentals including chemical aspects
and mass transport
• Variety of short courses available
Emerging Educational Issues
• Geoenvironmental engineering requires
interdisciplinary training. Less focus on
fundamentals in core discipline (e.g.,
foundations for a geotechnical engineer)
and more focus on hydrology, chemistry,
and mass transport.
• Interdisciplinary MS may leave engineer
vulnerable to changing marketplace (i.e.,
inadequate training in a core area).
Emerging Practice Issues
• Difficulty bringing new technology and lessons
learned into practice (e.g., Metro Landfill)
• Too little emphasis on innovative design (meet
the regulation rather than a performance goal)
• Commodity engineering with budgets and
margins that are too small
• Need to read (i.e., self educate and continuing
education) along with meeting goals for billable
hours