Hundreds of tons of rock and concrete will be needed to fill a sinkhole that developed at Tom Lee Park on the Downtown Memphis riverfront in September.

MORE: Sinkhole forms at Tom Lee Park

The Memphis Public Works Department says it was caused by the park's drainage system. Crews patched the hole but they're also being forced to make repairs to the drainage system that will cost the city an estimated $300,000.

The Riverfront Development Corporation said the situation could have been much worse if the sinkhole formed in the spring when the park hosts the annual "Memphis in May" event.

It should take the city a week to repair the sinkhole.