The source borehole (SB) was equipped with a borehole sparker SBS42 (http://geotomographie.de/assets/equipment/Productsheet-SBS42.pdf) generating a highly repeatable signal. The sparker was moved from 13 - 8 m depth connected to an impulse generator IPG5000 (http://geotomographie.de/assets/equipment/Productsheet-IPG800+5000.pdf) that operates at 5 kV for high voltage power supply. Two hydrophone strings (BHC5 - http://geotomographie.de/assets/equipment/Productsheet-BHC5.pdf) with 17/24 hydrophones of small diameter were mounted to receiver borehole 1 (RB1) and receiver borehole 2 (RB2) accordingly from 8 - 13 m depth with a spacing of 1 m between each hydrophone. The first set of shots was released at 13 m depth and the sparker was pulled up with a shot increment of 1 m.In both receiver boreholes we recorded and stacked 10 (5 regular + 5 repetetive) shots for each depth during the baseline measurement and every monitoring cycle.Our sampling intervall was 20.833 µs and the recording length covered 30 ms.