Remediation of Kolho impregnation area

Ekokem-Palvelu Oy carried out remediation of the timber impregnation plant site of Kolho in 2003 and 2005. Timber has been impregnated in the site since the 1950s. Compounds from creosote oil and CCA-impergnants, including PAH-compounds, arsenic, chrome and copper, had polluted the area. Constant creosote oil effluents flew from the site to Strait of Kolho, which launched remediation works to be commenced.

Remediation was carried out in three phases in 2001, 2003 and 2005. Ekokem-Palvelu Oy carried out remediations of 2003 and 2005. Ekokem-Palvelu Oy excavated ca. 53 500 m ³ of contaminated soil from the site, including massive quantities of impregnated timber covered by soil.

Contaminated soil was transported to different receptory sites depending on level of its pollution. An elemental part of the project was construction of Loila hazardous waste landfill nearby the site, where 30 000 m3 of moderately contaminated masses were disposed.

Part of the area is filled former lake bottom, which enables free groundwater flow between the site and Strait of Kolho. Therefore drainpipes and pile planking had to be built under groundwater surface. Large quantities of water contaminated by creosote oil accumulated to excavation pits, which demanded robust pumping and sound treatment systems. The deepest parts of polluted groundwater aquifer are remediated in situ. After excavation works a protective structure for plant’s railroad was built, and the site was covered by an impervious asphalt layer.