The Akacievej field site

Highlights
Description of the field site

The field site: Akacievej, Hedehusene Fig.1: Location of the remediation system and extent of contaminant plume in 2006 and 2015. Site history At the Akacievej site, a dry cleaning facility was operating in the period 1973-2003. In 2002, the site was screened for contamination by analyzing the contaminant concentrations in soil and in the pore air. This revealed high concentrations of PCE and TCE close to where dry cleaners were operating in the years between 1973 and 1975. Most of the contamination is likely to be from the operation of the dry cleaning facility and a release during a fire at the site in 1975. An array of boreholes was drilled to localize the source zone and to delineate the contaminated area The contamination was evaluated to pose a potential risk for the drinking water extraction at the Fløng waterworks, which has its closest extraction well about 600 meters north of the Akacievej site. In 2007, the most contaminated soil containing PCE as DNAPL was removed and extensive remedial activities were started. The goal of the remedial activities was to remove the hotspot and to achieve hydraulic control of the groundwater contamination. The following actions were taken: Removal of contaminated soil in the source area 0-6 m bgs. Local excavation down to the limestone surface at about 8 m bgs. (limestone is found below ca. 7.5 m bgs.) Establishment of venting pipes and a drainage pipe Remedial pumping with 2.5 m3/h from the upper 6 meters of the limestone to establish hydraulic control Activated carbon filtering of the pumped water and infiltration of the purified water through infiltration cassettes with an overflow connected to a deep borehole Until 2015, a contaminant plume with a length of approximately 500 m had developed. The plume extent and the location of the remediation system are shown in Figure 1. From 2014 to 2016, various measurements were taken at the site, including different contaminant sampling techniques, slug tests, geophysical measurements, analyses of borehole cores. In spring 2016, a long-term pumping test and several tracer tests were conducted at the site to further enhance the understanding of contaminant transport dynamics in fractured limestone. Fig.2: Geologic cross section at the Akacievej site. Geology The geology at the Akacievej site is depicted in Figure 2 and consists of a carbonated sand limestone (København Kalk) on top of a bryozoan limestone (Stevns Klint formation), both with a strongly varying hardness. Due to glacial activity, the uppermost 1 to 5 meters of the limestone are crushed. Most of the crushed limestone is in the carbonated sand limestone, but at some places it also penetrates into the bryozoan limestone. The bryozoan limestone at Akacievej does not show strong bank structures and is rather even. Return to Content