In-Situ Solidification/Stabilization For Arsenic Impacted Soils/Sediments. Raj Singh Kleinfelder Inc.

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1 In-Situ Solidification/Stabilization For Arsenic Impacted Soils/Sediments Raj Singh Kleinfelder Inc. RE3 Conference 2014

2 Solidification/Stabilization (S/S) Solidification Entrap contaminants within a solid matrix Coating of contaminant molecule Organics are generally immobilized due to reduced hydraulic conductivity Stabilization Bind or complex contaminants May involve chemical transformation Metallic contaminants are stabilized by precipitation or by interaction (e.g. sorption) with cement matrix Example: Lead Pb(HCO 3 ) 2 +CaSO 4.2H 2 O PbSO 4 + CaCO 3 +3H 2 O +CO 2

3 Cement-Based S/S Technology Solidification Process forms a granular or monolithic solid that incorporates the waste material A solid matrix, calcium-silicate-hydrate (C-S-H) is formed in presence of water Cement Hydration Reaction (Thomas, 2004): xcasio + yh 2 O xcao.ysio.zh 2 O + wca(oh) 2 + Heat Calcium Water Calcium Silicate Hydrate Lime Silicates (C-S-H) Reduces mobility of chemicals of concern Increases strength Reduces permeability Minimizes free liquid

4 Contaminants Trapped in Porous Matrix Cement grains Trapped contaminants Low permeability reduces the mobility of hazardous substance in the environment Treated Catalyst Untreated Catalyst

5 Why is Relative Hydraulic Conductivity Important?

6 Factors Influencing S/S Material Leaching Moisture Transport H 2 O Environmental Attack H + CO 2 O 2 Cl - SO 4 2- Chemical Factors Equilibrium or Kinetics Liquid-to-solid ratio Potential leachability ph Complexation Redox Sorption Biological activity Physical Factors Particle size Leachant flow rate Hydraulic conductivity Porosity Fill Geometry Temperature Hydrological conditions Ca 2+ Leachant Composition Water Acids Chelants DOC OH - Erosion Cracking Soluble salts Trace elements DOC Ref. Internal and external factors influencing the leaching process (modified from Garrabrants and Kosson, 2005)

7 Arsenic Standard Groundwater NJDEP NRDCSRS (non-residential) for Arsenic is 19 mg/kg NJDEP RDCSRS (residential) for Arsenic is 19 mg/kg NJDEP Groundwater Quality Standard is 3 ug/l GW Quality Criterion PQL Higher of PQL and GWQC 0.02 ug/l 3 ug/l 3 ug/l Standard based on PQL: GWQC IS HEALTH BASED 7

8 Common Arsenic Forms As 0 - Semi-Metallic As 3+ - Arsenite As(III), Toxic, Mobile As 5+ - Arsenate As(V), Less Toxic and Less Mobile Note - As 3+ and As 5+ are commonly found in water/environment 8

9 Eh ph Diagram of Aqueous Arsenic 9

10 Arsenic Eh ph Diagram with Sulfur 10 10

11 Arsenic S/S Consideration Geochemistry important for S/S design Convert Arsenite (3 + ) to Arsenate (5 + ) (less soluble) through oxidation, if needed Maintaining ph in a certain range is important to control leachability Tiered treatability testing very important 11

12 Possible Arsenic Immobilization Mechanism Portland Cement Reaction: 1. Precipitation formation of Ca 3 (AsO 4 ) 2(s) & CaHAsO 3(s) 2. Inclusion Physical encapsulation by creating solidified monolith Chemical inclusion in CSH and CAH by isomorphic substitution 3. Sorption on clay and pozzolanic reaction product, cation/anion exchange 12

13 Possible Arsenic Immobilization Mechanism Chemical Reaction/Precipitation Ferrous Sulfate Reaction: 4Fe 2+ +2AsO H 2 O 2 Fe(OH) 3 + 2FeAsO 4(S) + 6H + 13

14 Solubility Products of Some Common Arsenic Species Arsenic Species Solubility Product Ag 3 AsO x AlAsO x Al(HAsO 4 ) x As 2 S x Ba 3 (AsO 4 ) x Ca 3 (AsO 4 ) x FeAsO x Mg 3 (AsO 4 ) x

15 Case Study 1 Approximately 44,700 CY of soil 1 to 10 feet thick Elevated levels of TPH, PCBs, As, Cr +3, Cr +6 Pre-treated SPLP As concentrations above the GWQS Mix Design 4% Ferrous Chloride (Aq.) 15% Portland Cement

16 Case Study 1 Contd. Post S/S Results Parameter Range Average UCS psi 202 psi Permeability 6x x10-06 cm/sec 5x10-07 cm/sec SPLP As ND(3) 6.9* ppb 0.6 ppb SPLP Cr ND(10) 81* ppb 34 ppb Couple of cells failed initially

17 Case Study 2 Approximately 11,000 CY of sediment 1 to 10 feet thick, containing 8 27% tar like material Elevated TPH, PCBs, benzene, As, Be, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene SPLP concentrations for the pre-treated sediment Sb ND(5) 8.3 ppb; > GWQS of 6 ppb As ND(1) 40 ppb; > GWQS of 3 ppb Pb ND(5) 16 ppb; > GWQS of 5 ppb Mix Design 10% Bed Ash (CaO &SO 3 ) with 8% Class C Fly Ash and 6% Enviro Blend (MgO & Calcium Phosphates)

18 Case Study 2 Contd. Post S/S Results Parameter UCS Permeability SPLP As SPLP Be SPLP Pb SPLP Sb Results (Avg) 30 psi 1.2x10-06 cm/sec ND(3) ppb ND(0.2) ppb ND(1) ppb ND(5) ppb

19 Case Study 3 Approximately 3,000 CY of soil 1 to 10 feet thick SPLP concentrations for the pre-treated sediment Bis(2-Ethylhexyl)phthalate: ND(6.6) 54.6 ppb; above the GWQS of 3 ppb Di-n-octyl phthalate: ND(5.7) 39.3 ppb; above the default leachate criteria of 20 ppb As: ND(3) 3.8 ppb; above the GWQS of 3 ppb Pb: 1 23 ppb; above the GWQS of 5 ppb Mix Design 10% Portland Cement+5% Enviro Blend

20 Case Study 3 Contd. Post S/S Results Parameter UCS Permeability SPLP As SPLP Be SPLP Pb SPLP Di-n-octyl phthalate SPLP bis(2-ethylhexyl)phthalate Results 75 psi 5.8x10-07 cm/sec 1.6 ppb 0.2 ppb 3.4 ppb ND(0.5) ppb ND(0.75) ppb

21 Conclusions S/S reduces potential risk of groundwater impacts S/S eliminates direct contact risk S/S will support future use Cost of S/S is $83/cy - (including GW Dewatering with Onsite Treatment) Cost of S/S $75/cy- (w/o GW Dewatering)

22 S/S Mixing Equipment Shallow Depth (1 3 ft) Rototiller, bucket, power shovel, etc. Intermediate Depth (3 23 ft) Lang tool, ALLU, bucket, etc. Deep Mixing ( ft) Rotary auger, jet grouting injection Mixing Under Structures Jet grouting injection 22

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26 THANK YOU QUESTIONS

Treatability Testing Evaluation and Implementation of In-Situ Stabilization/Solidification at a Former MGP Site

Treatability Testing Evaluation and Implementation of In-Situ Stabilization/Solidification at a Former MGP Site Rajesh (Raj) Singh Kleinfelder Inc. David Guirguess PSE&G James Mikochik Michael McGowan