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(PH146) Development of site-specific remedial objectives (SSRO) for weathered petroleum hydrocarbons in peat soil environments.

Harris, C1, Jackson, R1, 1 AMEC Earth & Environmental, Edmonton, Alberta, Canada

ABSTRACT- Petroleum hydrocarbon (PHC) soil and groundwater criteria are not designed for organic rich, peat soils, common in the northern boreal forest. In the absence of site-specific assessment and toxicological data, the Alberta regulatory authority applies a de-minimis criteria for remedial action. Since petroleum crude exploration, production and pipeline transportation in the northern boreal forest is increasing, hydrocarbon spills are possible and applying de-minimis criteria may be unnecessarily conservative. AMEC developed a site-specific remedial objectives (SSRO) for a historical petroleum crude oil release on organic rich peat soil in the northern boreal forest. The release occurred over 10 years ago and periodic active aeration has resulted in a weathered profile dominated by the heavier end C10 - C50+ fractions, especially those in the C16 - C36 range. In these less mobile and less biodegradable fractions, the ecotoxicological hazards, and regulatory criteria, are primarily related to direct soil contact with invertebrates and plants. Site soils containing a wide range of PHC concentrations were tested for 14 day Eisenia foetida survival and growth; 28 day Folsomia candida survival and reproduction; germination and root elongation with a standard crop, Latuca sativa, and two native tree species, Picea mariana and Larix laricina. Qualitatively, the dose response relationships indicated the C10 - C50+ cumulative value best explained the observed responses, rather than individual fractions. A database of 37 no effects, low effects, threshold effects endpoints was compiled using parametric (probit) and non-parametric (bootstrap) statistical techniques. Those endpoints which failed to produce a probit linear fit with a p value of greater than 90%, and endpoints which appeared as extreme outliers, were eliminated from the dataset. The SSRO was established as the lower 25th percentile of the species sensitivity distribution (SSD) generated with the remaining 34 endpoints. The resulting C10 - C50+ SSRO value of 5,560 mg/kg would be met by approximately 75% of the residual heavy end petroleum hydrocarbons remaining on the spill site, and represents a 65% increase over de minimis criteria.

Key words: soil , hydrocarbons, criteria


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