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A potential energy surface covering the interconversion between the two symmetry-equivalent geometries of the hydroperoxyl anion, $HO2$ via a symmetric T-shaped saddle point was computed at the QCISD(T)/6-311++G(2df.pd) of level of theory. An analytical molecular potential function was fit to the ab initio data. The classical barrier to the interconversion was estimated to be $6057cm-1$ Using the parameterized function the vibrational states were calculated by the discrete variable representation-distributed Gaussian basis method. Computations predict the onset of tunnelling from about 4 quanta in the bending mode-A splitting of $6cm-1$ is observed between the odd and even 0.10 state. Presence of at least one quanta in the O$-$O stretching mode enhances splitting significantly.