The sidewalk and a natural gas pipeline prevented local cleanup crews from removing all of the contamination immediately after the spill. Over a period of several weeks, the fuel spread and contaminated groundwater, found at a depth of 10 feet. Cedar Creek Engineering was then asked to take over the project.
Cedar Creek proposed removing the sidewalk and securing the gas line to allow excavation of contaminated soil. Soil and groundwater in the saturated zone would be treated via in-situ chemical oxidation.
Temporary sheet piling was installed to prevent pea gravel in the underground storage tank pit from spilling into the excavation and destabilizing the USTs.
The sheet piling and UST vent pipes were anchored securely.
Once groundwater was encountered, it was no longer feasible to continue excavation. Chemical oxidants were used to eliminate residual hydrocarbon.
An excavator was used to mix reagents into the soil and groundwater. Substantial amounts of heat and steam were produced when the hydrogen peroxide contacted the catalyst-rich slurry.
Soil and groundwater samples were collected from the open excavation. Backfilling then began immediately.
Excavation, chemical treatment and backfilling were completed in three days. Final landscaping and concrete repair took three more days.
All soil and groundwater samples yielded hydrocarbon concentrations below closure limits and the site was closed by state regulators with no further action required.