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

Transcription

1 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 John Bracken Kleinfelder Inc.

2 Presentation Outline ISS and Leachability Testing Overview Site Description Proposed Remediation ISS Bench-Scale Treatability Testing Overview Bench-Scale Treatability Testing Results Conclusions Lessons Learned

3 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

4 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

5 S/S Technology Process Source Zone Footprint Contaminants Solidified Columns Water Table Groundwater Flow Direction Bedrock Low Hydraulic Conductivity Soil Before S/S After S/S

6 S/S Technology Advantages/Challenges Advantages: Effective in treating many contaminants Applicable for in-situ (ISS) or ex-situ treatment Treatment period relatively short Can improve structural property of soil Usually more cost-effective than off-site disposal Disadvantages: Contaminants are neither destroyed nor removed Uncertainties associated with prediction of long-term performance Volume increases in the treated mass Requires removal of large debris and obstructions

7 Key ISS Performance Parameters Leachability Reduced contaminant solubility/leaching retains contaminants (SPLP Method 1312), Method 1315, etc) Hydraulic Conductivity Reduced hydraulic conductivity = reduced water flow through treated material Measured by permeability testing (ASTM 2010b) Strength Increased by cementitious reagents Measured by UCS (ASTM D1633)

8 Relating Leachability to Cleanup Goals Remedial goals often established at POC away from S/S treatment area Leaching tests should not be considered to directly represent POC values ITRC, 2011

9 Leaching Assessment Tests Single-Batch Extraction Equilibrium Tests TCLP (EPA Method 1311) Ground, Acid, RCRA Characteristics, Landfill Disposal, Equilibrium Controlled SPLP (EPA Method 1312) Ground, acid rain, acceptable for ISS, equilibrium controlled Flux-Based Leaching Tests ANSI/ANS Whole, water, nuclear waste, up to 90 days, diffusion controlled LEAF Method EPA Method 1315, similar to ANSI/ANS 16.1, DI water, inorganics/organics, diffusion controlled.

10 Leaching Assessment Tests LEAF Method 1315 (Cont d) Interval Label Cumulative Leaching Time (d) ITRC, 2011 T (2 hrs) T2 1 T3 2 T4 7 T5 14 T6 28 T7 42 T8 49 T9 63 Method 1315 setup

11 Site Description Approximately 3 acre former MGP Site in NJ Contaminated soils exceed site-specific Impact to GW Soil Remediation Standards (IGWSRS) Soils and GW impacted with BTEX, PAHs, metals (As and Pb) NAPL Oily Material, Tarry Material Gravelly fill material with Wissahickon formation Bedrock bgs Groundwater ~ 8 10 bgs

12 Site Description (continued) Area 2 ~2 acres Area 1 ~ 0.12 acres

13 Site Description (continued) Area 1 COCs: PAHs, As, Pb Area 2 COCs: NAPL (OM, TM), BTEX, PAHs, As, Pb

14 Proposed Remediation Remediation Objective Remediate soil to below the site-specific NJDEP IGWSRS Proposed Remediation (Areas 1 and 2) Excavate top 8 feet of contaminated soils and dispose off-site ISS treatment of soils from 8 ft. bgs to bedrock (~20 30 bgs) Area 1-1,887 CY Area 2-44,181 CY ISS bench-scale treatability testing was undertaken to assess feasibility, reagents, leachability, design mix.

15 Bench-Scale Treatability Testing Performance Criteria Strength: Achieve 50 Psi Hydraulic Conductivity (K): Achieve 1 x 10-6 cm/sec Leachability: Meet the NJDEP Class II GWQS using leachability tests SPLP (EPA 1312) - Screening LEAF (EPA Test Method 1315) Final Assessment

16 Bench-Scale Treatability Testing - Methodology Reagent Selection Portland Cement Type II Ground Granular Blast Furnace Slag Bentonite (Area 1 only) CETCO Organoclay PM-199 (Area 2 only) Ferrous Sulfate EnviroBlend Standard Coarse

17 PSE&G Warren Street Bench-Scale Treatability Testing - Methods Baseline Laboratory Testing Establish a bench-mark for comparison of treated samples against untreated Physical Screening (Tier 1) Eliminate mix designs not meeting strength (50 Psi) and hydraulic conductivity (1x10-6 cm/s) criteria Leachability Screening (Tier 2) Eliminate mix designs not meeting the site-specific IGWSRS through SPLP (Method 1312) Final Leachability Assessment (Tier 3) Assess leachability using LEAF Method 1315

18 Bench-Scale Treatability Testing - Methodology Target Parameter Tests Physical Testing Unconfined Compressive Strength (UCS) (ASTM D1633) Hydraulic Conductivity (K) (ASTM 2010b) Analytical Testing (Total, SPLP and LEAF) VOCs PAHs TAL Metals DOC Conductivity ph

19 Bench-Scale Treatability Testing - Results Area Area1 Reagent Components 5% Portland Cement 4% Blast Furnace Slag 5% Portland Cement 4% Blast Furnace Slag 1% Bentonite 5% Portland Cement 4% Blast Furnace Slag 1% Bentonite 2% EnviroBlend UCS (PSI) K (cm/sec) SPLP (EPA 1312) LEAF (EPA 1315) E-07 Failed - Naphthalene, Pb Passed E-07 Passed Passed E-07 Failed - Naphthalene, Pb Failed - Xylenes 5% Portland Cement 4% Blast Furnace Slag E-08 Failed - Benzo(a)anthracene, Naphthalene, As, Pb Failed - Benzo(a)anthracene Area 2 5% Portland Cement 4% Blast Furnace Slag 2% Oleophilic Clay 5% Portland Cement 4% Blast Furnace Slag 2% Oleophilic Clay 2% EnviroBlend E-08 Failed - Benzene, As, Pb Passed E-07 Failed - Benzene, Pb Passed

20 Bench-Scale Treatability Testing Area 1 Results

21 Bench-Scale Treatability Testing Area 2 Results

22 PSE&G Warren Street Bench-Scale Treatability Testing - Results Conclusions Results indicated that several mix designs met criteria The majority of mix designs failed leachability testing for SPLP, but majority passed for LEAF Area 1: Mix 1 5% cement, 4% BFS Mix 2 5% cement, 4% BFS, 1% bentonite Area 2: Mix 1 5% cement, 4% BFS, 2% OC Mix 2 5% cement, 4% BFS, 2% OC, 2% EnviroBlend TM Cost Excavation/offsite disposal ~$28 million. ISS $18 million.

23 PSE&G Warren Street Bench-Scale Treatability Testing - Results Lessons Learned Particle size reduction Saturated vs. unsaturated soils Untreated soil batches should be thoroughly homogenized Water to create slurry mix should be inert and low TDS/alkalinity Lab reporting limit work out issues ahead of time

24 THANK YOU QUESTIONS?