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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


Xylene and pesticides


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)


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)


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


TCE and related byproducts (vinyl chloride)


Soil Mixing: Fall – Winter 2011


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)


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


Acetone


Soil Mixing: Winter – Spring 2012


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)


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)


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


Creosote


Soil Mixing: Spring 2012


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)


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)


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

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