Site Remediation
Management Program
The key issues in managing contaminated sites are:
 |
Status of potential pathways
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Receptor protection
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Source identification and control
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Nature and extent of soil,
groundwater, and vapor impacts
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Physical characteristics of the
subsurface
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Properties of the chemicals present
in the soils and groundwater
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Timely, cost-effective, and
environmentally-sound remedial action
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Develop/implement the appropriate
technology sequence
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Site Assessment
Basic Objectives
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Define the nature and extent of the affected soil and
groundwater and the risk to the public health and the environment
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Determine the site-specific critical issues that drive the
overall response action
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Develop the technical basis for a timely, cost-effective, and
environmentally sound response plan
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Develop long-term, site-specific environmental liabilities
management plan
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Principles
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Driven by need to effectively manage the site and to protect the
public health and the environment
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Evaluate local media: soil, surface water, groundwater,
and air
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Identify at-risk receptors and likely exposure pathways
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Determine all chemicals of concern
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Focus on source definition and control
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Focus on dissolved plumes
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Develop sufficient data to manage all site issues
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Design, Construction, and Operation
The critical issues are:
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Health, safety, and quality take priority
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Use standard sized pumps, meters, valves, controls,
instruments, etc.
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Allow for "easy" changes and modifications in response to
progress results
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Field fit most of mechanical and electrical
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Realistic cost and schedule
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Commit the necessary resources
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Technology Selection and Sequence
The major factors are:
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Properties of the chemicals present in the soils and groundwater
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Status of potential pathways and receptors
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Site facilities, utilities, and support systems
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Project specific remediation criteria
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Cost and schedule considerations
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Progress monitoring and response
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Remediation Technology Sequencing
(This table illustrates technology sequencing based on remedial
effectiveness (cost and progress))
|
Technology |
*Application range (ppb of
VOCs in soils or groundwater) |
|
³100,000 |
10,000-100,000 |
1,000-10,000 |
500-1,000 |
<500 |
|
Excavation/Disposal/Treatment |
X |
|
|
|
|
|
In-Situ Thermal Desorption |
X |
|
|
|
|
|
Biopile Treatment |
X |
|
|
|
|
|
Soil Vapor
Extraction/Thermal Oxidation |
X |
X |
|
|
|
|
Pump and Treat |
X |
X |
|
|
|
|
Chemical Oxidation |
|
X |
|
|
|
|
Air Sparging |
|
X |
|
|
|
|
Ex-Situ Groundwater
Bioremediation |
|
X |
X |
|
|
|
Bioventing |
|
|
X |
|
|
|
In-Situ Groundwater
Bioremediation |
|
|
X |
X |
|
|
Granular Activated Carbon |
|
|
|
|
X |
|
Monitored Natural
Attenuation |
|
|
|
|
X |
|
* Approximate ranges based
on cost and progress.
Technology selection and
sequence tends to be site-specific, depending on hydrogeology,
receptors, chemicals present, etc. |
Progress Measurement and Control
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Define the site-specific progress parameters
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Focused database management and reporting
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Regular reviews of progress trends
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Test progress trends with field tests
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Performance based measurement systems
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Flexible analytical and QA/QC
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Covers all media and matrices
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Analytical database drives process
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Program
Controlled Analytical Capability
Typical examples of progress curves
are:
Physical
Behavior of LNAPL Constituents
An understanding of the physical behavior of organic chemicals is critical
to the design and operation of the remediation sequence.
Physical Behavior of DNAPL Constituents
Free Product Removal
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Continuous belt separation
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Spiral pump at the interface
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Smart pumps
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Deep wells with deep sumps
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Solvent flushing
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Surfactant Enhanced Aquifer
Remediation (SEAR)
|
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Two-phase extraction (vapor and
liquid extracted together)
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Bioslurping - a type of TPE that
maximizes LNAPL removal and bioventing |
|
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Dual-phase extraction (gas and liquid extracted separately)
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Dual Phase Extraction (DPE)
Install dual phase (vapor and water) extraction wells on most projects to
expedite sequencing and response to progress data.
Relative Oxidizing Power of Chemical
Oxidants
Note: The chemicals of concern, residual oxygen
demand, and site-specific physical conditions determine the best chemical
oxidant.
|
Reactive Species |
|
Relative Oxidizing Power
(CI2-1.0) |
|
Fluorine |
|
2.23 |
|
Hydroxyl Radical
(Fenton's) |
|
2.06 |
|
Sulfate Radical |
|
1.91 |
|
Ozone |
|
1.77 |
|
Persulfate Anion |
|
1.72 |
|
Hydrogen Peroxide |
|
1.31 |
|
Permanganate |
|
1.24 |
|
Chlorine Dioxide |
|
1.15 |
|
Chlorine |
|
1.00 |
|
Bromine |
|
0.80 |
|
Iodine |
|
0.54 |
Intrinsic Biodegradation Processes
This schematic illustrates the relative performance range for the major
biodegradation processes.
Biocatalysis/Biodegradation Database
Biological conditions exist that will biodegrade most combinations of
organic chemicals at most sites. Need to design systems to optimize the process.
|
131 Pathways
|
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831 Reactions
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785 Compounds
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530 Enzymes
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326 Microorganisms
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110 Biotransformation rules
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50 Organic functional groups
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Predict microbial
catabolic reactions
Biochemical
periodic table
Ways to Deliver Oxygen to the
Subsurface
The oxygen needs to be available to the subsurface biological community to satisfy
the stimulated oxygen demand.
|
Method |
O2 |
|
Demand
|
|
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Hydrogen peroxide
injection |
High |
|
Air/oxygen sparging, pulsed |
Medium |
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Diffusive
oxygen emitters |
Medium |
|
Eductors,
supersaturate, P & T |
Medium |
|
In-well
oxygenation
(course/fine bubble, gas aphrons)
|
Medium |
|
Electrolysis (H2O ? H2
and O) |
Low |
|
Solid forms
(oxygen/magnesium) |
Low |
In-Situ Bioremediation
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Most Volatile Organic Compounds (VOCs) are biodegradable
|
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Optimize electron acceptors/donors, nutrients, pH and other
factors
|
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Several approaches:
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Direct injection of amendments to subsurface
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Extraction/reinjection of water with amendments
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Membrane diffusion of amendments into groundwater
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In-Situ Bioremediation, Schematic
System Layout
Mobile Well Service Unit
Most in-situ bioremediation systems only require periodic treatment in
terms of extraction, water treatment, and injection of nutrients and electron
donors. A single service unit can handle up to 8 sites within a 50-mile
radius.
Phytoremediation
|
|
HC |
Cl-HC |
|
Gradient control/evapotranspiration |
|
ü |
ü |
|
Rhizosphere biodegradation |
|
ü |
ü |
|
Native species perform best |
|
ü |
ü |
|
Low maintenance conditions |
|
|
|
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Plant selection influenced by water balance |
|
ü |
ü |
·
Model transpiration rate, stand density
|
|
|
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Irrigation required to establish stand |
|
ü |
ü |
·
Deep watering stimulates root growth
|
|
|
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Water/soil quality affects establishment |
|
ü |
ü |
·
Salt concentration, pH
|
|
|
Note:
HC - hydrocarbon; organic chemical
Cl-HC - chlorinated organic chemical
Natural Attenuation Processes
|
|
HC |
Cl-HC |
|
Destructive (mass reduction) |
|
|
|
·
Intrinsic biodegradation
|
ü |
ü |
·
Abiotic chemical reactions
|
ü |
ü |
|
Non-destructive (mass conservative) |
|
|
|
·
Adsorption to organic fraction
|
- |
- |
·
Dispersion
|
ü |
ü |
·
Advection
|
ü |
ü |
·
Diffusion
|
ü |
ü |
·
Volatization
|
ü |
ü |
·
Dilution
|
ü |
ü |
Microbial Metabolism of Organic Matter
|
Respiration Process |
Electron Acceptor |
Metabolic Products |
Relative Potential Energy |
|
|
|
|
|
|
Aerobic Respiration |
O2 |
CO2, H2O |
High |
|
Denitrification |
NO3- |
CO2, N2 |
|
|
Iron reduction |
Fe3+ |
CO2, Fe2+ |
|
|
Sulfate reduction |
SO42- |
CO2, H2S |
|
|
Methanogenesis |
CO2 |
CH4 |
Low |
|
Suflita
and Sewell (1991) |
|
|
|
|
|
|
|
|
Transition to Natural Attenuation
|
Active remediation end point
|
·
Analytical basis
·
Physical basis
·
Chemical basis
·
Modeling
|
Cost/benefit analysis
|
|
Human health and environmental risk assessment
|
·
Attenuation action levels
·
Concentration reduction factors
·
Final compliance goals
Transition to Natural Attenuation
|
Monitoring network adequate to track progress
|
|
Expect some rebound : equilibration
|
|
Evaluate rebound and overall database
|
|
Periodically reevaluate risk to nearest receptors
|
|
Allow time for natural attenuation to work
|
|
Develop rebound response plan
|
|
Everything is site-specific
|
Chlorinated Hydrocarbon Remediation
Extraction Well Progress
Monitoring Well Progress
Chlorinated Hydrocarbon Remediation,
Intermittent System
Progress Curve, Mixed Chemical Site
Remediation Technology Sequencing
|
Technology |
*Relative Cost, $x103 |
Typical Effective Range,
ppb VOCs |
Typical Duration Months |
|
|
Design |
Construction |
Monthly O&M |
|
|
|
Excavation/Disposal/Treatment |
10 |
40 |
2 |
>100,000 |
2-3 |
|
In-Situ Thermal Desorption |
10 |
70 |
50 |
>100,000 |
3-5 |
|
Biopile Treatment |
5 |
20 |
4 |
>100,000 |
3-6 |
|
Soil Vapor
Extraction/Thermal Oxidation |
10 |
50 |
12 |
100,000-10,000 |
6-12 |
|
Pump and Treat |
10 |
40 |
10 |
100,000-10,000 |
12-24 |
|
Chemical Oxidation |
5 |
40 |
7 |
100,000-10,000 |
3-6 |
|
Air Sparging |
10 |
45 |
10 |
100,000-10,000 |
10-15 |
|
Ex-Situ Groundwater
Bioremediation |
10 |
40 |
12 |
100,000-1,000 |
12-24 |
|
Bioventing |
5 |
30 |
4 |
10,000-1,000 |
18-36 |
|
In-Situ Groundwater
Bioremediation |
7 |
45 |
12 |
10,000-1,000 |
18-36 |
|
Granular Activated Carbon |
3 |
20 |
12 |
<500 |
NA |
|
Monitored Natural
Attenuation |
4 |
20 |
2 |
<500 |
5-15 yrs |
|
*These costs are relative
to each other for a specific site. The costs are based on timely,
cost-effective technology sequencing. These costs are for a
typical gas station site. Actual site-specific costs may vary. |
|
