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

overview Draft guidance document released October 2018 Soil-to-Groundwater Pathway (a.k.a. “Leaching”) Importance of leaching evaluation Overview of document, including key sections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

What is leaching? Migration of contaminants from soil to groundwater

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

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

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

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

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

Leaf methods

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

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

Analyzing TCLP & splp results Method 2: linear regression

models Partition Equation SESOIL VLEACH VS2DT Others

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

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

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

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

Questions & comments David Hayes david.hayes@dnr.ga.gov 404-657-8672