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Part C - Minimum Requirements on geotechnical investigations 
1.3 Transitional, deviation and supplementary rules 
Transitional arrangements must be agreed with the Federal Maritime and Hydrographic 
Agency on a case-by-case basis. 
Differences from the codes of practice named in Part C, section 1.2 are permitted when taking 
the unusual conditions for offshore structures into account. Differences should be made 
known and reasons for such should be stated by the geotechnical engineer. Final approval 
from the Federal Maritime and Hydrographic Agency to such changes is necessary, so that 
they can consult appropriate inspectors. 
Supplements to the stated standards by means of further codes of practice, guidelines and 
recommendations are to be carried out, if and provided that the latter do not contain any 
guidelines or are not applicable for a topic on a case-by-case basis, and if certain aspects of 
geotechnical surveys and investigations for offshore wind farms are not or insufficiently taken 
into account. 
2 Requirements on offshore investigations 
2.1 Planning of field investigations 
The geotechnical expert, in co-operation with the design engineer, selects suitable survey and 
investigation methods on the basis of the preliminary geological report and determines the 
number and arrangement of exploration sites and the site survey depth in each case. 
In the course of the geotechnical site investigations, the geotechnical expert has to decide 
whether additional investigations or different methods are required, which are then applied 
according to his/her instructions. This is particularly likely in case of inhomogeneous or other 
wise unfavourable soil conditions. 
The geotechnical expert may commission adequately qualified personnel to assist him/her in 
monitoring the field investigations. 
2.2 Investigation methods 
Direct and indirect investigation methods will be distinguished in the following. 
Important technical normative information for direct and indirect investigation methods as 
part of geotechnical surveys can be found in DIN EN ISO 22475-1 and the standards set out 
in DIN EN ISO 22476. Drilling, sampling methods and probes should satisfy the stated stand 
ards regardless of the working platform or carrier technology over the entire section under 
investigation. 
Geodetic measurement of all investigation sites must be in accordance with the demands of 
IHO (2008) for Order 1 surveys and must be documented accordingly. DIN EN ISO 10012 
defines a common binding framework for correct execution. 
2.2.1 Direct explorations (Drilling) 
DIN EN ISO 22475-1 lists suitable onshore drilling methods, which can also be used offshore 
if jack-up rigs are used as a working platform. When using corresponding heave motion com 
pensation systems, these processes are generally available also for the use of floating work 
ing platforms. 
Typical drilling procedures when using drillships can be used e. g. McClelland & Reifel (1986). 
Further information is also available in DIN EN ISO 19901-8.