Hi,
as mentioned above by other forumers. Ref. PANS OPS VOL 1
1.5.5 Gradient specification
1.5.5.1 Published gradients are specified to an altitude/height after which the minimum gradient of 3.3 per cent is considered to prevail.
1.5.5.2 The final PDG continues until obstacle clearance is ensured for the next phase of flight (i.e. en-route, holding or approach). At this point, the departure procedure ends and is marked by a significant point.