Leachability Evaluation in In Situ Stabilization / Solidification

Transcription

1 Leachability Evaluation in In Situ Stabilization / Solidification Beth Liu, Ted Telisak, EA Engineering, Science, and Technology, Inc., PBC Camille Hueni, Environmental Protection Agency, Region 6

2 Presentation Outline In Situ Stabilization / Solidification (ISS) Key Performance Parameters Leachability Evaluation and Methods Case Study Lessons Learned Conclusions Questions

3 In Situ Stabilization / Solidification (ISS) Processes that mix reagents with contaminated material to transform it into a material that is: Durable Solid Low in hydraulic conductivity To reduce the rate of contaminant migration through leaching Used for NAPL Source Treatment/Control

4 ISS (Cont.) Technology Process Source Zone Footprint Contaminants Solidified Columns Water Table Groundwater Flow Direction Bedrock Low Hydraulic Conductivity Soil Source: ITRC 2013 Before S/S After S/S

5 Key Performance Parameters Strength Withstand loads Indirect indication of durability Unconfined compressive strength (UCS) measured by ASTM D1633 UCS > 50 psi Hydraulic Conductivity Reduce water flow through treated material Measured by ASTM D5084 < 10-6 cm/s Leachability Retain contaminants Various methods (SPLP, TCLP, LEAF Methods ) Goal comparable with cleanup goal

6 Leachability Evaluation and Methods Overall Purpose of Leachability Evaluation Screening and Predict Meeting the Remedial Goals Regulatory Tests Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) Issues with SPLP and TCLP Leaching Environmental Assessment Framework (LEAF) Methods 1313, 1314, 1315, and 1316

7 Case Study Former wood preserving operations 26 Acres, vacant lot Listed on the NPL on June 10, 1986 Groundwater: Creosote free product, PCP, and naphthalene as COCs Limited to the shallow water bearing zone (SWBZ). Creosote to about 20 feet below ground surface (bgs) SWBZ depth to water: ~ 16 feet bgs 350 feet to offsite Days Creek

8 Case Study (Cont.) Groundwater Naphthalene Concentration Groundwater Pentachlorophenol Concentration

9 Case Study (Cont.) ISS Objectives Source Control Bench Study (2004) Focused on leaching measured by SPLP ISS Mix Selected (by weight of soil): 10% Portland cement 4% powdered activated carbon 11% water Field Pilot Study (2010) Full Scale Implementation (2012) A total of 48,000 CY treated, 1,645 columns mixed Site under MNA

10 Naphthalene SPLP Concentration (mg/l) Naphthalene SPLP Concentration (mg/l) Case Study (Cont.) 100 HYD Conductivity and Naphthalene SPLP Results 100 UCS and Naphthalene SPLP Results Meeting the cleanup goal and UCS > 50 psi. 1 Cleanup Goal = 0.49 mg/l 1 Cleanup Goal = 0.49 mg/l Meeting the cleanup goal and hydraulic conductivity < 10-6 cm/s E E E E E E E E E-06 Hydraulic Conductivity (cm/s) Unconfined Compressive Strength (UCS) (psi)

11 UCS, Hydraulic Conductivity, and Naphthalene SPLP Results Sample UCS (psi) K (x1e-7 cm/s) SPLP (x0.1 µg/l) SPLP (x0.1 µg/l) K (x1e-7 cm/s) UCS (psi) Note: K = hydraulic conductivity

12 Case Study (Cont.) Groundwater Naphthalene Plume Before ISS Groundwater Naphthalene Plume 4 Years After ISS

13 Hydraulic Conductivity (cm/s) Lessons Learned ISS Objective Source Control Treatability Study Essential Physical Criteria vs. Leachability Criterion LEAF Application 1.00E E E-06 Unconfined Compressive Strength (UCS) and Hydraulic Conductivity SPLP > 0.49 mg/l Cleanup Goal 1.00E E-08 Physical performance parameters accepted Some Other Project: UCS > 150 psi and Hydraulic Conductivity < 10-7 cm/s UCS (psi) Case Study Pilot Case Study Full Scale

14 Conclusions Goal Source Control Treatability Study Approach Tied to remedial objectives Focused on reducing leaching or strength and permeability Leachability evaluation method - SPLP Implementation Approach Performance monitoring: dosing, grout, UCS, hydraulic conductivity, leachability (SPLP) Performance acceptance criteria

15 Questions