“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: Expanded use on Re-introduced into US Geotechnical and Earth environmental sites for market: Jackson Lake Retention Applications stabilization & treatment Dam First used for Developed in Japan Solidification / and Europe Stabilization of wastes 1990 1960 1970 1980 2000 2010
Soil Mixing 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 – Background Conclusions 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 – Equipment for Environmental Applications Auger Mixing Excavator Mixing Excavator Mounted Rigs Buckets Or Or Crane Mounted Rigs 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
Reagents 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].
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) Potassium permanganate is bright purple at very low concentrations – material handling was a big part of the project. A number of obstructions were removed, including deep Work performed in a “bowl” to control foundations spoils
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) The oxidation reaction was evident at the surface as the material bubbled and changed colors Work performed in a “bowl” to control Project staging important because spoils of post treatment soil properties
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) 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. Potassium permanganate is bright purple at very low concentrations – material handling was a big part of the project. Iron storage very important – The sands and gravels presented very prevent rust! difficult drilling conditions
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) Project staging was very important given the liquid consistency of the soils post treatment. Work performed in a “bowl” to control Two drill rigs used throughout the project. The first rig was used for hot air spoils mixing and the second rig was used to add and mix in the chemical reagents
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) Powdered carbon delivered in supersacks Automated batch plant for proportioning grout components Carbon combined with creosote gave the Work performed in a “bowl” to control Two drill rigs used throughout the project. The first rig was used for hot air material it’s dark color spoils mixing and thesecond rig was used to add and mix in the chemical reagents
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
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