Remediation of contaminated site T5 T5 Rum roofing felt factory

Between 1908 and 1959, a coal tar oil distillation facility had been run at the old location of the Rum roofing felt factory which mostly produced roofing felt, asphalt and other tar products. In 1960, the raw material used to run the plant was switched to crude oil in the course of company restructuring.

1.5 hectares of soil below the factory premises had been heavily contaminated with tar and tar oils, among others. Certain spots also showed contamination with mineral oils. At the central damage areas, a large batch of PAH (polycyclic aromatic hydrocarbons) had been mobilised which, in turn, caused a widespread contamination plume in the ground water. Due to the contaminated site’s risk potential, it was classified as a priority 2 site.

In accordance with the project which had been approved under the Water Act, the remediation of the contaminated site included the following:

• Decontamination through removal of heavily contaminated soil (hot spots), mostly by means of replacement bores and subsequent filling
• Hydraulic measures (depression well, ground water purification, infiltration well, pump-and-treat technology)
• Pilot trial to evaluate the applicability of in-situ measures

Ground water purification
For purposes of discharge safety, the project team installed a ground water purification system. Thereby, ground water is extracted at a rate of 72m³/h by means of an extraction pump and directed over a dual-line purification system. Every line is equipped with an automated, backwashable sand filter and two activated carbon filters (18m³ of carbon volume each). The purified water is either made available to the industrial operation for cooling purposes or further filtered to be fed back into the ground water system.

The facility installed in a hall includes the operation of the remediation system for a total of ten years (until 2022). A thermal in-situ method including a successful five-month pilot trial employing a hot water flushing system was implemented in order to remediate those areas that could not be reached by means of large bores. For the purpose of said trial, a trial field with three extraction and infiltration wells as well as 13 additional temperature measurement gauges was installed. A total of 10.8m³ of ground water were extracted per hour, treated by means of sand and carbon filtration and heated to a temperature of up to 70°C. The heated water was infiltrated to make the contaminated soil heat up to a temperature of up to 50°C. The pollutants’ mobility was thus increased in such a way that they could be removed via the extraction wells.

• Earth excavated: 12,100t
• Residual material: 85,500t
• Tar oil: some 300l
• Re-filling: 130,000t of A2 / A2G material
• Construction waste: 17,300t
• Non-disposable: 28,500t
• Selective, open removal: 23,400m³
• Demolition work: some 5,000m³