1. FAQs for Evaluating the Soil-to-Groundwater Pathway
David Hayes
Voluntary Remediation Unit Coordinator
GIEC Workshop
December 4, 2018

2. overview Draft guidance document released October 2018
Soil-to-Groundwater Pathway (a.k.a. “Leaching”)
Importance of leaching evaluation
Overview of document, including key sections
Next steps

3. What is leaching?
Migration of contaminants from soil to groundwater

4. Importance of leaching Evaluation
Exposure pathway evaluated to determine soil cleanup standards
Soil Cleanup Standard
Direct Contact
Leaching

5. How is leaching evaluated?
Model
Laboratory leaching test
Observation-based approach (e.g., old soil release but no groundwater impacts)

6. Document overview Frequently Asked Questions format
Partition Equation (basic model)
Leaching Tests
Analysis of leaching test results
Recommendations for data collection and reporting
Models
Comparing soil concentrations to leaching values
Observation-based approach

7. Partition equation Conservative
Can be used with least amount of site-specific data
Used by EPD in determining default soil cleanup standards

8. Leaching tests TCLP (SW-846 Method 1311) SPLP (SW-846 Method 1312)
Others:
LEAF methods (SW-846 Methods 1313 – 1316)

9. Leaf methods

10. Analyzing TCLP & splp results
Adapted methodology from New Jersey guidance
Method 1: direct comparison
Method 2: linear regression
Method 3: determine site-specific Kd for use in model

11. Analyzing TCLP & splp results
Method 1: direct comparison
sample identification
total contaminant concentration in soil
(mg/kg)
field leachate concentration
(mg/L)
target leachate concentration
Sample 1
0.5
0.04
0.1
Sample 2
0.8
Sample 3 2
0.002
Sample 4 12
0.03
Sample 5 30
0.09
Sample 6 75
0.3
Sample 7
120
0.2
Sample 8
150
0.08
Sample 9
180
Sample 10
300

12. Analyzing TCLP & splp results
Method 2: linear regression

13. models
Partition Equation
SESOIL
VLEACH
VS2DT
Others

14. Demonstrating compliance
Comparing measured soil concentrations to leaching values
Maximum measured concentration
Mean concentration in soil borings
95% upper confidence limit (UCL) of the mean

15. Appendix Parameter determination Dilution Attenuation Factor (DAF)
Groundwater Recharge Rates
Soil-Water Partition Coefficient, Kd
Fraction of Organic Carbon, foc

16. summary Determining site-specific soil cleanups standards
Several options available (basic to advanced)
Updates include:
SPLP data collection & analysis
Borehole averaging & 95% UCL of mean
Observation-based approach

17. Next steps Public comment period through December 14th
Review comments and finalize document

18. Questions & comments
David Hayes