Home Remediation Case Studies Case Study F5: Removal of UST’s, Groundwater and Soil Contamination (Exeter)
Case Study F5: Removal of UST’s, Groundwater and Soil Contamination (Exeter)

Client

Imperial Tobacco Pension Trustees Limited

Location

Exeter

Project

Decommissioning and removal of underground storage tanks (UST’s) and associated infrastructure. Excavation and disposal of impacted groundwater and soils.

Challenges

Site investigation data indicated the presence of contamination in soils and groundwater around the tanks.

Solutions

Two 5000 gallon USTs were removed in accordance with Safe System of Work. Prior to removal tanks were cleaned and purged with a high pressure washer and any residual fuel of contaminated liquids removed for storage on site prior to disposed of to a licensed contractor.

Approximately 250lt of wash water and contaminated sludge were removed from the tanks during the clean out. Following a certified gas check the concrete surrounds around the tanks were broken out and removed to expose the tanks and then tanks removed and disposed of site to a metal recycling facility.

Pumps and associated pipework were already decommissioned and pipelines foam filled. These were dismantled and associated pipework chased out prior to disposal off site.

Following removal of USTs, associated infrastructure and concrete surrounds, CRL undertook excavation and disposal of contaminated soils associated with the tanks. All excavation works were overseen by an experienced remediation engineer/scientist who used visual and olfactory methods to identify any grossly impacted soils which were subsequently removed. Following excavation works, soil validation sampling was undertaken. A total of 425 tonnes of grossly impacted soil was removed.

Following excavation of soils, groundwater within the base of the excavation was treated. The original strategy proposed to use skimming units to remove free-product, however onsite observations showed there to be minimal free-product, only a slight hydrocarbon sheen. Skimming units would not be effective in this case. Total fluid pumps were used to remove contaminated groundwater into a storage tanks prior to offsite recycling at a suitability licensed facility. A total of 40000lt of liquid (hazardous groundwater) was removed from the excavation for disposal off site by vacuum tanker.

Following removal of free-phase product and validation of excavation CRL undertook enhanced aerobic bioremediation works through the addition of Advanced Formula Oxygen Release Compound (ORC Advanced®) to the base of the excavation prior to backfill.

After these works were completed CRL backfilled the excavated areas, and reinstated the infrastructure.

 

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