Stabilization and solidification technology for treating heavy oil-contaminated sediments

Stabilization and solidification mixtures of contaminated material with 60% weathered, oily crust, and 40% sediment were made, and acute toxicity ( Vibrio fischeri bioassay), hydrocarbons in leachates, and resistance to compression were determined. For stabilized materials, the hydrocarbon concentration expected in base soil (underneath stabilization cells) was calculated from hydrocarbon concentrations in laboratory leachates using a modified test that better simulates real site conditions (acid extraction of complete formed blocks). In the modified tests, an asymptotic behavior in the hydrocarbon concentration in leachates was observed, nearing a maximum after 15 days. The calculated hydrocarbon concentration in base soil was < 3000 mg/Kg in all concentrations of agglomerate and pozzolan used (3.75–15% CaO, 1.25–5.0% diatomaceous earth). Acute toxicity was null or indeterminate with respect to background levels. For solidified materials, in two of the treatments (3.75 and 7.5% CaO, 1.25 and 3.75% diatomaceous earth; plus gravelly backfill at 1:1), unconfined resistance to compression was sufficient for the material to be used as sub-base for rural roads (> 17.6 ton/m 2 ), but with higher concentrations of reagents (15% CaO, 5% diatomaceous earth; plus gravelly backfill at 1:1), the resistance was insufficient. In all solidification treatments, no toxicity above background was encountered, and Total Petroleum Hydrocarbons in leachate tests resulted in calculated hydrocarbon concentrations in base soil of < 3000 mg/Kg. From these data, it was concluded that stabilization and solidification were feasible for this site using low concentrations of reagents, and that it was not necessary to use a plastic liner to prevent subsoil contamination.