A former wood impregnation facility, which had been in operation for approximately 65 years, had led to contaminated soils and sediments at the site and these needed to be remediated. The site is located about 3 km east of Söderhamn city, next to the Bothnian Sea in Gävleborg County.
The wood impregnation was executed using creosote (1937 – 1997) and using a cupper, chromium, arsenic (CCA) agent between 1972 – 2002. The contamination mostly consisted of Polycyclic Aromatic Hydrocarbons (PAH) and arsenic, chromium, cupper and oil hydrocarbons were also present in isolated spots.
Contamination was encountered in the soil, sediments and the ground water. Additionally, pyrite ash (“Kisaska”) that was used as filling material contributed to the presence of heavy metals.
The project entailed the remediation through the excavation of approximately 70,000 m3 of contaminated soil and dredging of around 7,000 m3 of contaminated sediments, the transport of contaminated materials to an approved receiving facility for treatment/landfilling, water treatment and restoration works.
During the project, DEC treated a substantial amount of the soil through immobilisation in order to stabilise leachable metals. This made it possible to reuse the soil as the cover layer for the municipal landfill Långtå, in the Söderhamn municipality.