Remediation of the former Sahanmäki landfill, Hyvinkää Finland

Remediation of the former landfill was carried out as excavation of the contaminated soil and waste. Excavated landfill mass was replaced with uncontaminated, mainly surplus, soil.

The landfill site was challenging in terms of remediation, as the depth of the waste varied up to 5 meters below ground level. In addition, buildings in use were located on the property. Another challenge was the silt/clay layer that holds perched groundwater under the waste backfill. The site was partly located in an important groundwater area. Hyvinkää groundwater area is an artesian aquifer at the site, so the mass change had to be carried out without causing a hydraulic fracture of the bottom. This was accomplished by excavating and filling small sub sections at a time.

AFRY's experts have taken care of contamination surveys, groundwater monitoring programs and monitoring, carried out geotechnical planning of mass exchange, prepared a risk assessment and carried out remediation planning for contaminated soils. For remediation, we have drawn up a notification on the clean-up of contaminated soil, prepared applications for the Soil Condition grant to the Pirkanmaa Centre for Economic Development, Transport and the Environment (ELY Centre), supervised the remediation work and prepared the final report of the remediation.

Project details:

• Client: City of Hyvinkää
• Project: Remediation of an old landfill site
• Time: 2014 – 2023
• Location: Hyvinkää
• AFRY's role: groundwater and soil surveys, geotechnical planning, environmental monitoring of remediation, reporting