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Part B - Minimum Requirements on geological survey 
Table 5: Requirements of seismic investigations. 
Geological survey 
Objectives 
• Detecting the type and location of geological units 
Scope 
• Use of grids for exploration of the offshore construction site 
Recommendation: Spacing of the seismic grid of 500 m in longitudinal and 
transverse directions. In case of differences in similar grid positions due to 
certain features of the construction site, a maximum spacing of 1000 m 
must not be exceeded. 
Timing 
• Once 
Method 
• Boomers or alternative systems with comparable or better performance 
and sufficient signal penetration, resolution of at least 1 m required close 
to the surface 
• Supplementary sub-bottom profilers or chirp sonar for areas close to the 
surface (e. g. along the planned cable route corridors), vertical resolution of 
at least 0.5 m 
• Cruising speed: max. 4 kn 
• Usage up to sea state of 4, when systems are used together with a so- 
called “motion sensor” then usage up to swell 5 or 6 is justifiable 
Presentation of 
results 
• Section with interpretation (i.e. geological longitudinal sections and 
transects) 
• Map with the geographical location of geological units and structure ele 
ments (e. g. isolines map) 
• Data must also be submitted in digital format and with sufficient support 
ing documentation (internal format). 
Before carrying out geotechnical surveys (boreholes, probes), an investigation should be car 
ried out for reasons of safety in accordance with DIN 4020 to determine whether ordnance or 
cables are present with a magnetometer or an active metal detection system.