Damage caused by mineral oil products discovered and remediated as part of a construction project

In northern Lower Saxony, odorous and visually conspicuous soil areas were encountered in the course of a construction project.

The approx. 3,000 m² property in a medium-sized town north of Hanover has several buildings of different ages and uses. The majority are small businesses and offices. The aim was to modernise the existing buildings. In the course of this, dilapidated buildings were to be demolished and the supply lines renewed.

During the unsealing of the surface after the demolition work, areas were found in the subsoil that smelled strongly of mineral oil. The owners then informed the relevant authorities. The local lower soil protection authority recommended that the property owner consult an expert office to assist with the remediation of the contaminated soil areas.

M&P Ingenieurgesellschaft mbH was commissioned in September 2022 to provide expert support for the construction work.

Various commercial uses have taken place on the project site over the last 100 years. The uses as a car workshop and car wash had the highest environmental relevance. Pollutants such as MKW and PAH were released into the subsoil. The contaminated areas were to be excavated as part of the current construction project and disposed of in accordance with the applicable regulations.

Due to the proximity of a receiving watercourse and the peaty layers there, the level of the stratum water was approx. 0.80 m below the top edge of the site, so that dewatering had to be carried out. The stratum water was pumped out and treated using an activated carbon filtration system. The purified water was regularly analysed and, with the approval of the local water authority, discharged into the municipal sewage system.

In the course of this project, M&P Nord employees sampled a total of 30 piles and containers. Samples were also taken in situ several times, as it was not possible to stockpile the excavated soil for sampling and waste declaration due to the limited space available.

All work was carried out in close consultation with the local authorities. Once this measure has been completed, a comprehensive project report will be drawn up documenting the fundamental upgrading of this property.