As stated in a previous article (“PEA’s – Not All PEA’s Are Created Equal“) different PEA’s will contain different levels of detail due to the amount of hard technical data used in each. The same statement holds within a single PEA itself whereby different chapters of the same study can be based on different quality of data.
I have seen PEA’s for which many of the chapters were fairly high level based on limited data but then some parts of the technical report may go into great depth and detail. This may not be necessary. For example, if the resource is largely inferred then the mine production plan will have a fair bit of uncertainty built into it. So there is not a lot of value in the engineers preparing a detailed tailings design concept for that mine plan. Similarly there is little value in developing a very detailed operating cost model or cashflow model for a study which has uncertainty in many areas. This is a waste of time and money, it adds to the study timeline, and may give the impression that the study is more accurate than it really is.
Differing levels of detail in the same study is a common problem when diverse teams are each working on their own aspect of the study. Some groups may think they are working with highly accurate data (e.g. production tonnage) when in reality the data is still somewhat speculative.
My bottom line is that it is important for the Study Manager and Owner to ensure the entire technical team is on the same page and understands the type of information they are working with. The final study should be consistent throughout. Experienced reviewers will recognize the data gaps in the study and hence view the entire study in that light regardless of how detailed the other sections of the report appearing to be.