The Gujarat Government claimed here on Thursday that the attorney-general of India has given his legal opinion on the controversial three-metre hump to be built on Narmada dam in state's favour. However, top Narmada Nigam sources said that despite the "positive opinion" over the hump, so essential for pre-empting any damage to the dam structure in the event of overflooding during monsoon, it would take at least three more days for the state to begin implementing it.