We present extensive exact quantum calculations of the cumulative reaction probability (CRP) for the O(P-3)+HCl-->OH+Cl reaction for a large range of total angular momentum, using the most recent ab initio potential energy surface of Ramachandran This surface contains van der Waals minima in both the entrance and exit channels that are shown to be responsible for a number of prominent resonances in the CRP in the tunneling region. The evidence for this claim is based on an analysis of the quasibound states of the van der Waals minima and a simple overlap of these states with the region of the saddle point of the reaction. The shift of the CRP with total angular momentum is analyzed in detail, with a focus on the resonances. A rigorous test of the simple J-K shifting approximation is also made both for the total CRP and the thermal rate constant.