How do you remediate contaminated soil beneath buildings and structures at an active fuelling station without the need for expensive demolition, excavation, and pumping? This was the challenge Uno-X Automat presented to Ejlskov.
To answer that question Ejlskov provided a tailor-made plan using unique drilling and pumping technology. The result was over 500 injection points to depths of 5.5 m covering a 1400 m2 site, including under buildings and subterranean utilities. Ejlskov executed the plan in just over 3 months, without any demolition or excavation, and minimal disturbance for Uno-X Automat. The station was kept operational during the entire remediation work.
Project Objectives
The biggest challenge at the Præstø Uno-X Automat fuelling station was the large oil contamination plume that lay beneath buildings up to 5.5 m depth. An added difficulty was the shallow groundwater table. Ejlskov’s site surveys showed that there was approximately 5000 kg of oil contamination in the soil. The objective was to prevent migration of the oil contaminant plume, and provide total remediation of the soil to safe levels below the standards set by the Danish Environment Authority after 3-5 years.
Site Characterization
As a leading European expert in the revolutionary Membrane Interface Probe (MIP) technology, Ejlskov completed a high-resolution site characterisation that modelled the geology and the contaminant plume, and enabled efficient planning and injection of the Trap & Treat® BOS 200®. In all, 505 injections to a depth of 5.5 m were made in just over 3 months at the 1400 m2 site. Ejlskov’s flexible drilling equipment and technical expertise enabled a unique approach to remediating soil beneath buildings: drilling from within the building. Ejlskov also used a triangular injection grid pattern with vertical offset injection levels, high pressure top-down injection techniques, and adjustment of the lateral and vertical injection spacing in relation to the buildings and subterranean utilities.
Remediation technology
As a proven technology effective at remediating oil contaminated soils, the Trap and Treat® technology works by trapping the contaminants via carbon absorption, and by removing the contamination by biological degradation. These two mechanisms provide immediate contaminant mass-reduction and plume control. The product consists of an active carbon powder with calcium sulphate, nitrate, phosphate, and ammonia that is mixed a blend of microbes and water before being injected. Ejlskov included additional sulphate nutrients to the injected material to enhance the anaerobic microbial activity and accelerate the biological degradation of the oil contaminant.
Results
Ejlskovs new method took approximately 3 months to complete. The initial 14 months of monitoring after the injection reveal that Ejlskov’s Trap & Treat® BOS 200® injection technology reduced the levels of BTEX and MTBE oil contamination in the groundwater over most of the site to below the standard set by the Danish Environment Authority. Ejlskov is on track to handing over a fully-cleaned site to Uno-X Automat within the time period promised.
The advantages of Ejlskov’s remediation plan included:
- Environmentally friendly technology
- Removal of the contamination by degradation, not by dilution or simply transplanting the contamination
- Minimal interruption to Uno-X Automat operations at petrol station
- No permanent installations requiring power or maintenance