Joint application of shear wave seismics and direct push methods in the site investigation of an urban aquifer

In a highly permeable urban aquifer with a lower cretaceous mudstone aquiclude in the district Sudstadt of Hannover/Lower Saxony, a stationary plume of chlorinated hydrocarbons was investigated within a research framework on the use of monitored natural attenuation. In the vicinity of the isolated contaminant source a glacial channel was detected as a possible secondary source supplying the plume. Due to dense housing the channel morphology and possible pathways could not be mapped accurately by classical geological methods. Therefore, the structure of the aquifer was mapped with shear wave seismics on seven profiles covering a range of more than 3.5 km, utilizing a newly developed mobile land streamer unit. The seismic profiles were adjusted with 16 electric conductivity (EC) and penetration logs measured with direct push, delivering a high resolution image of the near surface bedrock. Due to its mobility and the characteristics of shear wave seismics this combination of methods is ideally suitable for work on sealed surfaces.