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“RECENT USES OF IN SITU STABILIZATION, IN SITU
CHEMICAL OXIDATION, AND IN SITU CHEMICAL
REDUCTION USING SOIL MIXING”
Presented by: Ken Andromalos & Daniel Ruffing
RE3 – Remediation, Renewal, Results
Soil Mixing – Development Timeline
First Used in US: Geotechnical and Earth Retention Applications
Developed in Japan and Europe
Re-introduced into US market: Jackson Lake
Dam
First used for Solidification /
Stabilization of wastes
Expanded use on environmental sites for
stabilization & treatment
1960 1970 1980 1990 2000 2010
Any technique used to mechanically mix soils with or without additives
More commonly, the term refers to processes by which reagents are injected and mixed with the soil
Processes vary:
In Situ vs. Ex Situ
Dry vs. Wet Reagent Addition
Single Auger vs. Multi Auger
Auger vs. Bucket vs. Rotary Drum
Purpose : the efficient creation of a soil-reagent composite with improved properties relative to the in situ soils.
Soil Mixing
Widely accepted means for cost effective site remediation
Other related acronyms:
Shallow Soil Mixing (SSM)
Deep Soil Mixing (DSM)
Stabilization & Solidification (S/S)
In Situ Stabilization (ISS)
In Situ Solidification (ISS)
In Situ Chemical Oxidation (ISCO)
In Situ Chemical Reduction (ISCR)
Soil Mixing – Background Conclusions
Soil Mixing – Equipment for Environmental Applications
Auger Mixing Excavator Mixing
Excavator Mounted Rigs
Or
Crane Mounted Rigs
Buckets
Or
Arm Attachments
Auger Mixing
• Auger mixing most commonly used soil mixing method for environmental projects
• Generally the most cost effective auger mixing for environmental applications is large diameter single auger mixing (pictured here)
Auger Mixing – general aspects
Columns installed in an overlapping pattern that ensures 100% coverage of the target area
Wet mixing is more common for environmental applications, but occasionally project or site conditions neccesitate the use of dry mixing methods or the use of air as a drilling fluid
Solidification vs. Treatment
Solidification / Stabilization (ISS) –
Contaminants are not purposefully chemically changed to less harmful forms, but are locked in low permeability matrices that reduce the contaminants’ impact on the surrounding soils and groundwater.
Treatment (IST) –
Reagents are used to actively promote a chemical change in the impacted material
Contaminants are purposefully chemically changed to less harmful constituents via reduction or oxidation
Sources: ITRC (2011)[6]; Gardner, F.G., et. al., (1998)[8]; Irene M.C., (1996)[9]; USEPA (2009)[10]; U.S Department of Defense (2000)[11]; U.K
Environmental Agency (2004)[12]; Raj, D.S.S; Rekha, C.A.P, Bindhu, V.H; Anjaneyulu, Y., (2005)[13]; Conner, (1990) [14].
Reagents
Solidification vs. Treatment – conclusions
ISS generally cheaper than IST
Lower reagent cost
Less material handling safety concerns
Similar schedules
Both viewed as acceptable remediation approaches, but IST often viewed as a more robust solution
Promotes active degradation of contaminants
Require similar equipment and labor, but IST projects are harder to implement Project staging more difficult
Material handling more difficult
Case Studies - Introduction
Case Study 1 – East Rutherford, NJ In situ chemical oxidation and stabilization of solvent impacted soils
Case Study 2 – Robbinsville, NJ In situ chemical oxidation of xylene & pesticide impacted soils
Case Study 3 – Waukegan, IL In situ chemical reduction of solvent impacted soils
Case Study 4 – Norwich, NY In situ chemical oxidation of acetone impacted soils
Case Study 5 – Columbus, IN In situ stabilization / solidification of wood treating impacted soils
Case Study 1 – East Rutherford, NJ
Original site use:
Glassware manufacturing facility
Contaminant of Concern
TCE and related byproducts
Performance Schedule
Bench Scale Study: Fall 2009
Site Prep Work: Spring 2010
Soil Mixing: Spring – Summer 2010
Treated Volume Dimensions 6,800 CYs – treated twice (13,600 CYs total)
Up to 20’ BGS
Reagents
Potassium Permanganate @ 17.5 lbs / CY
Portland Cement @ 202 lbs / CY (applied 3 days post oxidation)
Case Study 1 – East Rutherford, NJ (2)
Work performed in a “bowl” to control spoils
A number of obstructions were removed, including deep
foundations
Potassium permanganate is bright purple at very low concentrations – material handling was a big part of the project.
Case Study 1 – East Rutherford, NJ (3)
242 nine foot diameter columns installed
Quality Control
Post construction groundwater monitoring showed 99% reduction in TCE concentration
Wet grab samples were collected from recently mixed columns
Average UCS = ~270 psi @ 28 days
Average Permeability = 4.1 x 10-7 cm/s @ 28 days
Case Study 2 – Robbinsville, NJ
Original site use:
Chemical manufacturing facility
Contaminant of Concern
Xylene and pesticides
Performance Schedule
Soil Mixing: Summer 2011
Treated Volume Dimensions
2,500 CYs
Up to 15’ BGS
Reagents
Hydrated lime @ 72 lbs / CY (pH adjustment)
Sodium Persulfate @ 28 lbs / CY (oxidant)
Case Study 2 – Robbinsville, NJ (2)
Work performed in a “bowl” to control spoils
Project staging important because of post treatment soil properties
The oxidation reaction was evident at the surface as the material bubbled and
changed colors
Case Study 2 – Robbinsville, NJ (3)
91 nine foot diameter columns installed
Quality Control
Process controls were utilized to ensure the proper amounts of reagents were added to and mixed with the soils
Case Study 3 – Waukegan, IL
Original site use:
Outboard marine engine manufacturing
Contaminant of Concern
TCE and related byproducts (vinyl chloride)
Performance Schedule
Soil Mixing: Fall – Winter 2011
Treated Volume Dimensions
7,800 CYs
Up to 25’ BGS
Reagents
Zero Valent Iron (ZVI) @ 54 lbs / CY
Bentonite Clay @ 27 lbs / CY
Case Study 3 – Waukegan, IL (2)
Potassium permanganate is bright purple at very low concentrations – material handling was a big part of the project.
The sands and gravels presented very difficult drilling conditions
The ZVI soil mixing work was the first part of a much larger remediation effort at this Superfund site. The soil mixing was used to target the source
zone.
Iron storage very important – prevent rust!
Case Study 3 – Waukegan, IL (3)
224 nine foot diameter columns installed
Quality Control
Samples of mixed material were subjected to magnetic seperation tests to ensure the iron was well distirbuted.
Post construction sampling for TCE concentration to be conducted later.
Case Study 4 – Norwich, NY
Original site use:
Chemical manufacturing
Contaminant of Concern
Acetone
Performance Schedule
Soil Mixing: Winter – Spring 2012
Treated Volume Dimensions
19,500 CYs
Up to 30’ BGS
Reagents – Post hot air mixing
Ammonium Sulfate @ 0.5 lbs / CY
Potassium Chloride @ 0.25 lbs / CY
Phosphoric Acid @ 18 lbs / CY
Calcium Peroxide @ 21.5 lbs / CY
Case Study 4 – Norwich, NY (2)
Work performed in a “bowl” to control spoils
Two drill rigs used throughout the project. The first rig was used for hot air mixing and the second rig was used to add and mix in the chemical reagents
Project staging was very important given the liquid consistency of the soils post treatment.
Case Study 4 – Norwich, NY (3)
324 nine foot diameter columns installed
Quality Control Process controls were
utilized to ensure the proper amounts of reagents were added to and mixed with the soils
Post construction sampling to be conducted
Case Study 5 – Columbus, IN
Original site use:
Wood treating
Contaminant of Concern
Creosote
Performance Schedule
Soil Mixing: Spring 2012
Treated Volume Dimensions
4,600 CYs
Up to 17’ BGS
Reagents
Portland Cement @ 480 lbs / CY
Powered Activated Carbon (PAC) @ 120 lbs / CY
Case Study 5 – Columbus, IN (2)
Work performed in a “bowl” to control spoils
Two drill rigs used throughout the project. The first rig was used for hot air mixing and thesecond rig was used to add and mix in the chemical reagents
Carbon combined with creosote gave the material it’s dark color
Automated batch plant for proportioning grout components
Powdered carbon delivered in supersacks
Case Study 5 – Columbus, IN (3)
247 nine foot diameter columns installed
Quality Control
Wet grab samples were collected immediately after mixing
Conclusions
Soil Mixing
Widely used to treat & stabilize a number of wastes
Stabilization vs. Treatment
Stabilization less expensive, but contaminants remain relatively chemically unchanged
Numerous reagents for both stabilization and treatment
Case Studies
Recent case studies highlight the use of soil mixing for the treatment and stabilization of subsurface contamination
Material handling and storage very important
Careful planning and staging required