A significant portion of the near-surface geology in Denmark includes glacial moraine deposits, much of which consists of clayey till. Consequently, subsurface releases and spills of chlorinated solvents at industrial facilities in Denmark often end up as a sorbed phase or nonaqueous phase liquid (NAPL) that resides in clayey till.
Historical use of chromated copper arsenate (CCA) for treatment of building lumber has resulted in legacy arsenic and chromium contamination at dozens of wood treatment sites in Denmark.CCA is a highly acidic (pH 1-2) solution of salts (chromium oxide [CrO3] and copper oxide [CuO]) and arsenic acid (H3AsO4) that is pressure-injected into wood to protect it against insect and fungi damage. Arsenic (As[V]) serves as an insecticide, copper (Cu[II]) as a fungicide, and hexavalent chromium (Cr[VI]) as a fixing agent. Estimates indicate that CCA-treated waste wood in Denmark increased from 17,000 tons in 1992 to 100,000 tons in 2010.
The Høfde 42 pesticide waste disposal site is recognized as the most toxic contaminated site in Denmark. Between 1953 and 1962, the agrichemical manufacturing company Cheminova, with approval of Danish authorities, disposed of hundreds of tons of organophosphorus pesticide (OPP) and pesticide manufacturing wastes in pits at this site, which is located at a beach adjacent to the North Sea.
Groundwater in Denmark that has been contaminated with chlorinated solvents is often remediated using in situ chemical oxidation (ISCO) with permanganate, or bioremediation via in situ enhanced biological reductive dechlorination (ERD). Although ISCO using Fenton's reagent is a commonly used technology in North America for remediation of chlorinated solvents present in the subsurface as dense nonaqueous phase liquid (DNAPL), in Denmark the technology is still considered relatively unproven.
Groundwater supplies at many locations throughout Denmark have been impacted by chlorinated solvents including tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA). Much of the contamination has occurred due to releases from dry cleaning facilities, and solvent plumes are often found in residential neighborhoods. As a result, private and public stakeholders in Denmark are focusing increasingly on cost-effective remediation technologies.
Groundwater beneath a former manufacturing facility in a small Danish town is contaminated with part-per-million levels of trichloroethene (TCE) and cis-1,2-dichloroethene (cDCE). The TCE and cDCE contamination occurs primarily in a low-permeability clay layer that is not amenable to an active forced-gradient bioremediation design.
Trichloroethene (TCE) and hexavalent chromium (CrVI) have impacted shallow groundwater beneath an active manufacturing facility in Svendborg, Denmark. The site is primarily underlain by moraine clay deposits, and a thin sand layer is continuous across much of the site.
Kærgård Plantage is one of the most widely publicized contaminated sites in Denmark, and is often referred to as a "mega-site" because of the scale of the potential liabilities and breadth of wastes disposed at this shoreline location.
Groundwater beneath the Høfde 42 Harboøre Tange site is contaminated with some of the highest concentrations of organophosphorus pesticide wastes found anywhere in the world. From 1957 to 1962, pesticides and pesticide manufacturing wastes from a neighboring agrichemical plant were discharged to sand dunes at this site, which is located on the shore of the North Sea on the western coast of Denmark. Today, an estimated 267 tons of pesticides and pesticide manufacturing wastes remain at the site, primarily consisting of the highly toxic chemicals parathion, methyl parathion, and malathion. Largely immiscible in water, much of the pesticide contamination at the site is present as a dense, nonaqueous phase liquid (DNAPL). The site groundwater is highly acidic (pH of 3 to 4), and the groundwater toxicity is further increased by the presence of an estimated 60 Kg of mercury that is co-mingled with the pesticide wastes.
Microscale zero valent iron (mZVI) and nanoscale ZVI (nZVI) are often effective amendments for remediation of chlorinated solvents in aquifers, but success with mZVI and nZVI in aquitards such as clay till is rare when conventional injection techniques are used. Jet Injection, a technology developed by FRx that involves a combination of hydraulic fracturing and jetting, was previously demonstrated to effectively distribute sodium permanganate in a tight clay formation. Jet injection forces large volumes of water under very high-pressure into the subsurface inducing fractures that can be filled and further propagated with a slurry of remediation treatment agents such as permanganate or mZVI. Recognizing that Geosyntec possesses expertise with this technology, the Capitol Region of Denmark retained the team of Geosyntec, FRx, and COWI A/S to design and execute a jet injection pilot test in clay till at a Danish site.
© 2026 Geosyntec Consultants, Inc. All Rights Reserved.
