14 
Part B - Minimum Requirements on geological survey 
Part B - Minimum Requirements on geological survey with geophy 
sical methods 
1 General 
Geological survey is one of the requirements for identifying ground types (sediment types), 
describing their characteristics and for assessing their suitability for construction work. It 
makes use of modern, high-performance geophysical processes, the results of which must be 
verified based on direct explorations (drillings). Due to the lack of accessibility to the seabed, 
geophysical processes are an extremely efficient method to get a general overview of the 
ground conditions in selected areas within a short period of time and therefore the sediment 
distribution and tectonic elements are detected in such a manner which enables e. g. the iden 
tification of areas with heterogeneous or problematic ground conditions. 
Geological exploration is the basis for preliminary and main geotechnical survey and investi 
gation (see Part C, section 2). 
Geological investigations can be divided into two steps: 
• Geological reconnaisance should prove the general suitability of an area and also allow for 
detailed geological interpretation within an offshore construction site on the basis of a suf 
ficient number of geological sections. In such cases the local conditions for the compo 
nents of an offshore construction project should be drawn up for all sites as this ensures 
that unsuitable local ground conditions are identified and if necessary, relocation or optimi 
sation of individual sites is supported. 
Different regulations are illustrated for geological survey of offshore stations in Part B, sec 
tion 6. 
• During inspection individual sites must be monitored after erection of the structures with 
regard to potential scouring as well as checking that the minimum cover of submarine 
power cables is adhered to. In such cases the use of geophysical methods such as e. g. 
high-performance sonars corresponding to the state of the art should be allowed for in or 
der to adequately detect the local influence of structures on the seabed. The findings must 
be submitted in a inspection report to the approval authority in the prescribed time periods 
(see Tables 3 and 4). 2 
2 Quality assurance 
• The persons in charge must be able to prove that they have sufficient qualifications and 
proven experience. Their names must be listed in the geological report. 
• he data and the assessment thereof must be correct and verifiable. 
• Measurement protocols are to be kept; these contain i. e. the external conditions during sur 
vey (e. g. wind and ocean conditions, stratification of water bodies, algal bloom), vessel, 
measurement equipment, measurement configurations and the person in charge for such. 
• Position and depth accuracy must conform to the specifications of the International Hydro- 
graphic Organisation (2008) for Order 1 a and 1 b Surveys. Detailed requirements can be 
seen in Tables 3 and 4. 
• The measurement conditions must adhere to the required quality standard in all cases. 
Based on previous experiences, data quality is no longer guaranteed with a sea state of 5 
or higher.