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 %
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 %
2009 samples ET %
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 2008 Field Samples 2009 Field Samples
ET ±0.16%
PM ±0.07%
2008 Field Samples
ET ±2.6% (~ half-life 6.7 years)
PM ±0.37% (~half-life of >30 years)
2009 Field Samples
ET ±1.7 (~half-life of 8.7 years)
Ranges shown are measured standard deviations

6. Conclusions HEM Organic matter Recommendation
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 years
Alternative- rapid reduction initially, more stable now
Recommendation
Continue organic matter monitoring (extend interval)