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Empirical Attenuation Factors Predictions & Observational Data

This study evaluates empirical attenuation factors for volatile organic compounds (VOCs) based on extensive observational data collected from 2001 to 2004. Conducted by Ian Hers, Robert Truesdale, and Helen Dawson, it summarizes results from 15 sites across different VOCs and examines measured factors for groundwater to indoor air. The evaluation includes variables like chemical type, foundation and soil type, and depth to the source. Results indicate attenuation factors range from 10^-2 to 10^-7, with variations observed for BTEX compounds and influences that remain unclear.

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Empirical Attenuation Factors Predictions & Observational Data

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  1. Empirical Attenuation FactorsPredictions & Observational Data Ian Hers, Ph.D. Golder Associates Vancouver, BC, Canada Robert Truesdale RTI International RTP, North Carolina Helen Dawson, Ph.D. US EPA Region VIII Denver, CO

  2. Empirical Attenuation Factors • 2001-2002 Evaluations (Helen Dawson) • 2004 Evaluations (Ian Hers) • Future Evaluations (Robert Truesdale)

  3. Measured Attenuation Factors2001-2002 Database Summary • 15 sites, 15 VOCs, 274 total residence/chemical combinations • 35 BTEX; 239 CHC residence/chemical combinations • 99 sites with IA > 10-6 IA RBC(84 CHC, 14 BTEX) • 68 sites with IA > 10-5 IA RBC

  4. 2001 – 2002 Empirical Attenuation FactorsGroundwater-to-Indoor Air All residences and chemicals with concentrations above MDLs

  5. Factors evaluated (2001 – 2002) • Chemical type • Foundation type • Soil type • Depth to source

  6. 2001 – 2002 Empirical Attenuation FactorsChlorinated Hydrocarbons vs. BTEX

  7. 2001 – 2002 Empirical Attenuation FactorsInfluence of Foundation Structure? Groundwater

  8. 2001 – 2002 Empirical Attenuation FactorsInfluence of Foundation Structure?

  9. 2001 – 2002 Empirical Attenuation FactorsInfluence of Soil Type?

  10. 2001 – 2002 Empirical Attenuation FactorsDepth to Groundwater?

  11. 2001 – 2002 Empirical Attenuation FactorsConclusions • Measured attenuation factors range from 10-2 to 10-7 with median values around 10-4. • Influence of foundation type, soil type, and depth to water on the empirical attenuation factors is unclear. • Higher ranges of attenuation factors are observed for BTEX compounds; median value is around 10-5.

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