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ENGI 7718 – Environmental Geotechniques
ENGI 9621 – Soil Remediation Engineering
Spring 2011
Faculty of Engineering & Applied Science
Lecture 1: Introduction to
Environmental Geotechniques
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The science and practice of applying technical means in
order to achieve a lasting balance in the ground environment,
a balance which does not implement any harm to the organic
life
Ground means natural and man made ground including
all constituents (e.g. the groundwater) of the subsurface space
Balance may be of chemical, physical, mechanical,
hydrological, biological or of other character, and imbalance
may be caused by human activity, or by natural processes
Organic life means present and future, human and
natural life
1.1 Environmental geotechniques
(1) Definition
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Environmental geotechniques a combination/blend of
Geotechnical Engineering and Environmental Engineering
Geotechnical engineering a branch of civil engineering
Civil engineering serves the human community by
constructing various kinds of protection against natural
disasters, and building the infrastructure design/build the
quality of life
Environmental engineering is the application of science
and engineering principles to improve the natural environment
(air, water, and/or land resources) to provide a healthy
environment for human habitation and for other organisms,
and to remediate polluted sites.
(2) Relationships with other subjects
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Rock Mechanics
Foundations Retaining Structures Seepage/Slopes/Dams
Soil Mechanics
Geomechanics Geoenvironmental problems
Geotechnical Engineering
Challenge
Civil Engineering
Face it solve problems
Environmental
Geotechniques
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Contaminated site remediation remediation of
already contaminated soils and groundwater
Waste containment safe disposal of newly
generated wastes in engineered impoundments and
landfills
Waste minimization by recycling minimization
of waste generation and disposal by recycling and
using waste materials in various civil engineering
applications
(3) Type of geoenvironmental problems
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A sub-discipline of environmental engineering
The development and implementation of
strategies to clean up (remediate) the environment
by removing the disposed hazardous soil
contaminants
Muti-disciplinary involvement
Various sources and complex cocktail of
contaminants
1.2 Site remediation engineering
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1.2.1 Sources of soil contamination
Infiltration of contaminated surface water
Land disposal of solid and liquid wastes
Accidental spill
Fertilizers and pesticides
Disposal of sewing and water treatment plant
sludges …
(1) Originating on the ground surface
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Waste disposal in excavations
Landfills
Leakage from underground storage tanks
Leakage from underground pipelines …
(2) Originating above the water table
(Vadose Zone)
Waste disposal in wet excavations
Deep well injection
Mines …
(3) Originating below the water table
(Saturated Zone)
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1.2.2 Common soil contaminants
Heavy metals (Pb, Cd, Cr, Ni…)
Arsenic (inorganic and organic forms)
Chlorinated solvents (PCE, TCE, TCA, MC…)
Polycyclic aromatic hydrocarbons (PAH)
Polychlorinated biphenyl (PCBs)
Pesticides (organochlorines, organophosphates
and carbamates)
More information Visit Web of Federal Contaminated Sites at
http://www.federalcontaminatedsites.gc.ca/index-eng.aspx9
1.2.3 Selecting and/or designing a right
remediation technology
complex contaminants as well as unique site
features (geology, hydrology, etc)
tailored technologies are required on a site-
by-site basis
(1) Site characterization：
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end goal for clean-up how clean the site is
required to be
risk
stakeholder concerns
technological feasibility and convenience
effectiveness/practicality
ease of integration into remediation systems
cost and acceptance
(2) Comprehensive consideration for a
particular site
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Steps involved in remedial action
Source: USEPA, 1991
Site discovery
Preliminary assessment
Site inspection
Hazard ranking analysis
National priorities list
Remediation investigation
Remedy selection/
Record of decision
Remedial design
Remedial action
Project closeout
No federal remedial
action required
Feasibility study
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1.2.4 Overview of remediation technologies
(1) Technologies to remediate contaminated
soil fall into two principal clean-up approaches
In-situ (which is always done on-site)
deals with contamination without removing
material from the ground
Ex-situ (which can be done on- or off-site)
requires the removal of contaminated soil for
treatment or land-filling
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(2) Popular soil remediation technologies
Soil vapor extraction
In situ bioremediation
Soil flushing
Soil fracturing
Phytoremediation
Stabilization and solidification
Thermal desorption
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Soil vapor extraction
Source: Suthersan, 1997
Schematic of SVE implementation in the field
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SVE treatmentSource: WRScompass, 2008 16
In situ bioremediation
Source: Hardisty, 2005
In-situ bioremediation implementation17
Injection of enhanced bioremediation productSource: G&R Remediation , www.envirocoregr.com 18
Soil flushing
Source: Sharma and Reddy, 2004
Typical in-situ soil flushing in vadose zone19
Soil fracturing
Source: Sharma and Reddy, 2004
Two types of soil fracturing
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Hydraulic FracturesSource: Slack , 1998 22
Phytoremediation
Source: Suthersan, 1997
Phytoextraction of heavy metals
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Hybrid poplar tree for phytoextractionSource: Chappell, 1997 24
Stabilization and solidification
Source: Suthersan, 1997
In-situ S/S process
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Application of reagents to the S/S treatment siteSource: Jones, 2009 26
Thermal desorption
Source: US Ecology, Inc., 2007
A thermal desorption process
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On-Site Thermal Desorption (30,000 tonnes)
Source: DRL, 1997 28
(3) Popular groundwater remediation technologies
In situ air sparging
Vacuum extraction
In situ bioremediation and natural attenuation
Pump and treat systems
In situ reactive walls
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In situ air sparging with VES
Source: Hardisty, 2005 Schematic of AS-VES
(VES)
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Natural attenuation
Source: Hardisty, 2005
Schematic of natural attenuation
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Source: NAVFAC POC, 2009
Contaminant plume formed during natural attenuation
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Pump and treat
Source: Hardisty, 2005
Schematic of pump and treat34
In situ reactive walls
Source: Grubb, D. G. and N. Sitar, 1994
Reactive walls
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Source: U.S. Department of the Interior, 2003 Building reactive walls 37
1.3.1 Solid waste generation
Municipal solid waste (MSW) solid wastes which are responsibility of a municipality (also named "refuse")
1.3 Waste containment
Composition of disposed MSW in Canada
Source: Natural Resources Canada, 2002 38
Per capita MSW generation in 2005
Source: Environment Statistics by Country, 2009 39
1.3.2 Solid waste reduction and processing options
Landfill most economical and most common method for
MSW treatment
Composting aerobic decomposition of organic matter in
MSW (~ 45%) by microorganisms (bacteria and fungi)
Incineration MSW contains ~ 50% combustible material
when burned, its volume is reduced
Reuse, reduction, and recycling
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90% MSW in UK, Canada, USA
over 60% MSW in Western Europ
fires, water pollution, odors,
rats and flies, blowing papers
better compaction
leachate collection
site monitoring
liner system
1.3.3 Landfill
Old landfill = town dump
Sanitary landfill
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Problems with landfill
MSW landfillorganic matter is decomposed aerobically firstly, and then
anaerobically during decomposition
liquid from waste and water from rainfall/runoff percolate through MSW
produce contaminated liquid (named "leachate" - contain BOD, COD, metals)
leachate migrate through the underlying soil
to groundwater table contaminate groundwater
Leachate generation
Methane gas release
Anaerobic decomposition in landfill
gas generation => take place over a long time (about 30 yrs)
methane production rate = 2.5 to 3.7 L/yr per kg of MSW
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Landfill system design
Surface capping system
Gas collection system
MSW landfill cell system
Leachate collection system
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Source: Shanahan, Waste Containment and Remediation Technology, 2004
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Source: Federal Remediation and Technologies Roundtable, 2003
Surface capping system
Landfill cap
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Source: Fernald Environmental Management Project, 2002 Geomembrane46
Gas collection system
Gas vent layer
Waste
Source: Shanahan, Waste Containment and Remediation Technology, 2004
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(Shanahan, Waste Containment and Remediation Technology, 2004)
MSW landfill cell system
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Source: Shanahan, Waste Containment and Remediation Technology, 2004)
Leachate collection system
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