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Organoclay Cap Performance

Organoclay Cap Performance. Methods. Hexane Extractible Material (EPA 9071B) Surrogate for oil content (85 ± 5% of NAPL extractible) Extractible portions with no NAPL Sediments (<1%) Sands (negligible) Organophylic clays PM-199 (1.25±0.77%) ET-1 (3.5±0.81%)

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Organoclay Cap Performance

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  1. Organoclay Cap Performance

  2. Methods • Hexane Extractible Material (EPA 9071B) • Surrogate for oil content (85 ± 5% of NAPL extractible) • Extractible portions with no NAPL • Sediments (<1%) • Sands (negligible) • Organophylic clays • PM-199 (1.25±0.77%) • ET-1 (3.5±0.81%) • Organic matter (OM)/carbon (OC) content • Indicator of organophylic component content of clays • PM-199 (34.67 ± 0.22%) OM • ET-1 (24.13 ± 0.51%) OM Ranges shown are estimated 95% confidence limits

  3. Hexane Extractible Material • Fresh Samples • 2.1% ± 1.2% • Field samples • 2006 ET-1 1.7-6.6% • Significant oil capacity remaining correlation with water content • 0.76 ±0.46 g/g dry OC • 0.61±0.25 g/g dry OC excluding two outliers • 2008 ET-1 1.32-5.42% • 2009 samples ET-1 1.1-7.9% • Conclusions • Significant NAPL capacity remaining • HEM not a sensitive indicator (but can indicate high NAPL %) • Field ET-1 samples exhibit higher and more variable HEM than fresh samples (not seen in PM-199- field and mat samples avg. 1.25%)

  4. Profiles - 2009 WC-01 Intermixing at top HEM normal variations WC-02 HEM slightly elevated Possible lateral NAPL movement?

  5. Organic Matter • Fresh Samples • ET-1 24.1±0.16% • PM-199 34.7±0.07% • 2008 Field Samples • ET-1 15.9±2.6% (~ half-life 6.7 years) • PM-199 32.4±0.37% (~half-life of >30 years) • 2009 Field Samples • ET-1 16.2±1.7 (~half-life of 8.7 years) Ranges shown are measured standard deviations

  6. Conclusions • HEM • Not a sensitive indicator of NAPL • Will indicate significant NAPL contamination (>10%) • No evidence of NAPL contamination at that level • Organic matter • ET-1 more variable and showing potential degradation • Half-life of 6.7-8.7 years • Alternative- rapid reduction initially, more stable now • Recommendation • Continue organic matter monitoring (extend interval)

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