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LDEQ

LDEQ. RECAP Miscellaneous Topics. Exposure Assessment. Site-specific under MO-3 only Construction worker scenario Greatly reduced ET, EF, and/or ED Site-specific data should be documented. Exposure Assessment. Absence of site-specific data  Default values

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LDEQ

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  1. LDEQ RECAP Miscellaneous Topics

  2. Exposure Assessment • Site-specific under MO-3 only • Construction worker scenario • Greatly reduced ET, EF, and/or ED • Site-specific data should be documented

  3. Exposure Assessment • Absence of site-specific data  Default values • Permanent vs non-permanent structures • Enclosed structures

  4. Exposure Assessment Additional exposure considerations when the site-specific GW2 or GW3 DAF is large: • Construction worker exposure • Volatile emissions to ambient air (GWair) • Cross-media transfer - migration to deeper zones

  5. Toxicity Assessment • Unavailability of toxicity values • Develop a toxicity value(s) • Identify a surrogate toxicity value based on structure/activity and/or targets • Route-to-route extrapolation • Qualitative evaluation

  6. Toxicity Assessment • No speciation data ex) Cr+3 vs Cr+6 • New slope factor ranges in IRIS • Dermal toxicity values • If GI absorption efficiency < 50%  adjust oral tox value • If GI absorption efficiency > 50%  do not adjust • RAGS HHEM Supplemental Guidance Dermal Risk Assessment Interim Guidance (EPA 1998)

  7. Background Data • Where should samples be collected? • How many samples??? • How should the data be used? • Calculate arithmetic average • Obtain Department approval • Compare to arithmetic average for AOI • What if there are high anthropogenic bg levels???

  8. TPH Issues • TPH-G, TPH-D, and TPH-O • Physical/chemical properties presented • Soilsat and Watersol not applicable • Target organs/critical effects identified

  9. Wet Weight vs Dry Weight • Data is routinely reported on wet-weight basis • Wet weight used for exposure concentrations • Dry weight used for EF&T calculations • Wet weight  Dry weight

  10. Soil to Groundwater PathwaySPLP Data • Where should SPLP samples be collected? • How is the SPLP data used to evaluate the soil to gw pathway? • SoilGW1: Compare SPLP to GW1 x DFSummers • SoilGW2: Compare SPLP to GW2 x DFSummers x DF2 • SoilGW3: Compare SPLP to GW3 x DFSummers x DF3

  11. Soil to Groundwater PathwaySPLP Data • If SPLP <, then screen out soil to gw pathway • If SPLP >, then delineate area of concern • SPLP vs TCLP • SPLP vs LRS

  12. Estimation of Sd Sd = Thickness of impacted groundwater within permeable zone Sd = 5’ 10’ 5’ Un-impacted groundwater Impacted groundwater 15’

  13. Estimation of Sd Sd = Thickness of permeable zone if thickness is not known or if the zone is not impacted Sd = 15’ 10’ Un-impacted groundwater 15’

  14. Alternate RS • MO-3 only • Technically impracticable and/or economically infeasible ONLY • Corrective Action Study • Requires Department Approval

  15. Workplans • Required for MO-3 • Recommended for some MO-2 • The more detailed, the better • Id of AOI/COCs • CSM • Id of approaches/methods • Id of assumptions/site-specific and default inputs

  16. Fractional Organic Carbon Fractional Organic Carbon (foc) - Estimated by dividing the percent organic matter (POM) by a conversion factor of 174 - POM determined using ASTM D2974 - Samples should be collected from a non- impacted area at a depth consistent with the depth of impact - Default foc = 0.006

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