Supplementary Geophysical Survey in Urban Park for New Metro, Fælledparken, Copenhagen

The new metro line in Copenhagen, Cityringen, is currently under construction and is expected finalized in July 2019. As part of the preinvestigations urban geophysical site investigations were carried out including 13.9 km of seismic lines, 29 VSP (Vertical Seismic Profiles) as well as a geo-electrical survey covering Fælledparken, the largest urban park in Copenhagen (ca. 400,000 m²).

The purpose of the geoelectrical survey was to provide detailed hydrogeological information in the urban park area where only sparse borehole information was available.

A total of 68 criss-crossing DC-soundings were collected and interpreted using a Spatially Constrained Inversion (SCI). Due to this approach and detailed planning only 4 out of the 68 soundings were affected by electrical coupling effects from buried cables.

The results showed a 5–10 m thick secondary aquifer underlaid by approximately 10 to 35 m clay till indicating a minimal recharge from the secondary to the primary aquifer. Below the lower till the top of the limestone was seen dipping from approximately 25 m depth in the eastern part of the park to approximately 35 m in the western part.

The results contributed to a detailed hydrogeological understanding of the area and therefore a more realistic hydrological model.