Example Application of Long Term Stewardship for the Chlorinated Vapor Intrusion Pathway (and VOC sources)

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1 Example Application of Long Term Stewardship for the Chlorinated Vapor Intrusion Pathway (and VOC sources) Megan Hamilton Director of Vapor Intrusion and Risk Assessment EnviroForensics March 24, 2015 EPA VI Workshop at AEHS West Coast Conference San Diego, California

2 Scenario Background Indiana Site Operated as a dry cleaner from early 1980s until 2007 Operational releases over time Conceptual Site Model (CSM) Early Stages Upper 10 feet of soil is cohesive Clayey Silt, underlain by a poorly graded fine-medium grain Sand Soil impacts of tetrachloroethene (PCE), max 36 ppm Groundwater at 30 feet bgs, max 125 ppb beneath source Soil gas plume extends beyond site boundaries Located in a mixed residential and commercial area Multi-family, senior housing building adjacent

3 Scenario Background Indiana Site Maximum Soil >36,000 ug/kg PCE Maximum GW < 125 ug/l PCE

4 PCE Distribution in Soil

5 Scenario Background Indiana Site Soil Gas Concentrations on Site 7,580,000 ug/m 3 PCE Clay, upper unit 1,400,000 ug/m 3 PCE Sand, lower unit

6 VI Conceptual Site Model Scenario Background Indiana Site

7 Risk Evaluation and Point of Exposure Assessment Groundwater plume is stable and dilute. No current, but potential exposure. Soil impacts are in excess of migration to groundwater levels, but not direct contact thresholds. Potential exposure. Vapor Intrusion exposure pathway is potentially complete, and largely a result of impacted soils in shallow fine-grained zone, and residual soil gas plume in deeper sand. Potential exposure.

8 Remedial Planning Selected approach will result from analysis of variable amounts of contaminant mass removal in soil and groundwater, vs. scope of anticipated VI Long-Term Monitoring & Stewardship requirements. $ Remedy $ LTS

9 IDEM Vapor Remedy Guidance

10 Structures Analyzed for VI Long Term Stewardship Assessment

11 Potential Remedial Approaches Scenario 1 Scenario 2 Scenario 3 Remediation Approach No Source Treatment Excavation Excavation with Soil Vapor Extraction and Groundwater Treatment Long-Term Monitoring Duration 50 Years of Monitoring (50 total years) 25 Years of Monitoring (25 total years) 5 Years of Monitoring (10 total years)

12 Further Site Investigation Remediation Work Plan Preparation Excavation Soil Vapor Extraction Groundwater Remediation Remediation Progress Monitoring Long-Term Monitoring Regulatory Fees and Case Closure Remedial Approach Comparison Basis Scenario 1 X X X Scenario 2 X X X X X X Scenario 3 X X X X X X X X

13 Long Term Monitoring Components Groundwater Monitoring All Scenarios assume ICs & some term of groundwater monitoring GW monitoring duration shorter than VI in all scenarios Vapor Intrusion Monitoring Scenario 1: Addresses future VI concerns only by monitoring Scenario 2: Eliminates shallow source of ongoing contaminant flux into soil gas Scenario 3: Adds removal of residual soil gas plume in deeper zone and groundwater treatment to Scenario 2

14 Scenario 1 Further Site Investigation Long-Term Monitoring (50 Years) Annual Institutional Control Verification/Inspection Groundwater use restriction Future excavation/construction restriction Operation of existing/proposed SSDS systems Annual Sampling Annual groundwater sample collection Annual worst-case vapor intrusion sampling Monitoring Well Abandonment and Case Closure

15 Scenario 2 Further Site Investigation Building Demolition and Shallow Excavation Activities Long-Term Monitoring (25 Years) Annual Institutional Control Verification/Inspection Groundwater use restriction Operation of existing/proposed SSDS systems Annual Sampling Annual groundwater sample collection Annual worst-case vapor intrusion sampling Monitoring Well Abandonment and Case Closure

16 Scenario 3 Further Site Investigation Building Demolition and Shallow Excavation Activities Soil Vapor Extraction in Deeper Sand Groundwater Polishing Long-Term Monitoring (5 Years) Annual Institutional Control Verification/Inspection Groundwater use restriction only Operation of existing/proposed SSDS systems Annual Sampling Annual groundwater sample collection Annual worst-case vapor intrusion sampling Monitoring Well Abandonment and Case Closure

17 Cost Summary of Scenarios Scenario 1 Further Site Investigation 50 Years Long-Term Stewardship Regulatory Fees and Case Closure Scenario 2 Further Site Investigation Source Excavation Progress Monitoring 25 Years Long-Term Stewardship Case Closure Scenario 3 Further Site Investigation Source Excavation SVE and Groundwater Remediation Progress Monitoring 5 Years Long-Term Stewardship Case Closure Further Site Investigation $ 60,000 $ 60,000 $ 60,000 Remediation $ 25,000 $ 465,000 $ 1,410,000 Remediation Planning and Coordination $ 25,000 $ 50,000 $ 70,000 Transport and Remediation Modeling $ - $ 50,000 $ 75,000 Source Excavation $ - $ 285,000 $ 285,000 Soil Vapor Extraction $ - $ - $ 350,000 Groundwater Remediation $ - $ - $ 200,000 Remedial Action Design Report $ - $ 20,000 $ 30,000 Progress Sampling and Plume Behavior $ - $ 60,000 $ 400,000 Long-Term Stewardship $ 3,366,330 $ 1,713,165 $ 390,633 Closure Costs $ 50,000 $ 50,000 $ 50,000 Regulatory Review Fees $ 75,000 $ 37,500 $ 15,000 20% Contingency $ 715,266 $ 465,133 $ 385,127 PROJECT TOTAL $ 4,291,596 $ 2,790,798 $ 2,310,760 Years Cost/Year $ 85, $ 111,632 $ 231,076

18 Phase Breakdown of Scenarios $2,500,000 $2,000,000 $1,500,000 $1,000,000 $500,000 $0 FSI Remediation Work Plan Preparation Scenario 3 Further Site Investigation Source Excavation SVE and Groundwater Remediation Progress Monitoring 5 Years Long-Term Stewardship Case Closure Remediation Remediation Monitoring Closure Scenario 2 Further Site Investigation Source Excavation Progress Monitoring 25 Years Long-Term Stewardship Case Closure Scenario 1 Scenario 2 LTS (0-5 years) Scenario 3 LTS (5-25 Scenario 1 years) LTS (25-50 Further Site Investigation years) 50 Years Long-Term Stewardship Regulatory Fees and Case Closure

19 Cumulative Cost Summary of Scenarios $4,500,000 $4,000,000 $3,500,000 $3,000,000 $2,500,000 $2,000,000 $1,500,000 $1,000,000 $500,000 $0 FSI Remediation Work Plan Preparation Remediation Scenario 3 Further Site Investigation Source Excavation SVE and Groundwater Remediation Progress Monitoring 5 Years Long-Term Stewardship Case Closure Remediation Monitoring Closure Scenario 2 Further Site Investigation Source Excavation Progress Monitoring 25 Years Long-Term Stewardship Case Closure LTS (0-5 years) Scenario 1 Scenario 2 Scenario 3 LTS (5-25 years) LTS (25-50 Scenario 1 years) Further Site Investigation 50 Years Long-Term Stewardship Regulatory Fees and Case Closure

20 Thank You! Megan Hamilton Director of Vapor Intrusion and Risk Assessment EnviroForensics