Contingent Reserve

 A PM has $100,000 as contingence resreve for known unknown risk , now the risk has occured he used $100,000- he realizes that $100,000 is not enough to handle the situation , he needs $150,000 to handle this situation.  Where does he look for the additional funding or how does he handle this ?

He will have to put a change request asking for more money (last source). He could also use management reserve kept aside in budget estimation.

I would say he would pull the extra money from management reserve..