Systematic planning promotes the analysis of "reward versus risk" of each undertaking so that the outcome can be reasonably assured. The objective is to minimize hasty actions which may cause the situation to deteriorate, or limit recovery options, if the action fails. If the incident has escalated to Level 3, wait for control procedures and risk assessment to be developed by an integrated team with specialist support. Unless there is an urgent need (e.g. third party HSE risk), do not attempt a control operation that has an unknown risk and unknown probability of success just because it can be initiated right away.
Source Control is an oil spill term related to controlling or containing the source of the spill. In the case of a well blowout the Source Control organization is that group tasked with bringing the blowout back under control.