A 12-15 m³ gasoline spill was discovered in 2003 at a main retail petrol station outside Copenhagen (Denmark). Since the spill, the site owner had worked in close cooperation with the local municipality to prevent the contamination from spreading to the drinkingwater aquifer. Furthermore a range of clean-up methods had been tested but without reaching satisfactory results. In march 2012 a pilot test to assess effectiveness of Ejlskov Trap & Treat^® BOS 200^® was conducted in conjuntion with a full scale Remedial Design Characterization event. During the pilot test approximately 4,000 kg of BOS 200^® were injected across an approximate 100 m² area. After test completion, Ejlskovs BOS 200^® Trap & Treat^® technology was found to be the right solution. 

Project Objectives

In September 2014, a BOS 200^® full scale Performance Based Remediation contract was signed. Treatment objectives included:

• Elimination of LNAPL in all performance monitoring wells.
• Maintained site operations and minimum business interference.
• Fulfillment of risk based clean-up criteria of <500 ug/l in boulder clay formation located above primary limestone aquifer. 
• Achievement of Danish EPA’s requirements regarding <1 ug/l benzene in the primary limestone aquifer.
  
  

Site Characterization

Despite several environmental investigation events had been carried out over the years at the site, in 2012 it was decided to conduct a full round of Remedial Design Characterization (RDC) by first completing a MIP campaign aiming at delineating the lateral and vertical extent of the contamination present at the site. 

The campaign allowed to identify the areas where soil contaminant mass was present across the site and which depths were mostly impacted. Based on the evaluation of the contamination at the site, Ejlskov provided a tailor-made turnkey solution using unique drilling and pumping technology. The result was over 250 injection points to depths of 13.5 m covering the 1,271 m² site, including under buildings and subterranean utilities. The injection works started in October 2014 and were conducted over 2 phases of work (3 months each).

Remediation technology

Trap & Treat^® BOS 200^® technology stands out for its ability to degrade components under aerobic and anaerobic conditions. A sustainable slurry, containing activated carbon, nutrients and microorganisms, is injected into the ground. The active carbon mixture actively traps the contaminants, which are then degraded by the microorganisms. Ejlskov is the only supplier of this highly efficient, sustainable and patented technology in Europe.

Results

Injection works were completed in May 2015. After 14 months the following results have been monitored:

• No reoccurring LNAPL is observed in any of the perfomance monitoring wells.
• Target equilibrium benzene groundwater concentrations have been achieved in 6 of the 10 performance monitoring wells.
• 90% average reduction for BTEX is observed in the 10 performance monitoring wells.
• Negotiations for site closure and obtainment of NFA letter are currently underway with the local environmental authorities.