The true extent of the damage to the crumbling Oroville Dam spillway was revealed this week as authorities shut off the water flow and exposed the gaping hole left by the erosion.
Authorities this week started the huge clean-up process, with tons of rubble needing to be removed from the bottom of the spillway in order to get the Hyatt hydro-electric power plant back in operation.
Up to a million cubic yards of debris from the crumbling, concrete chute that takes water down from the top of the dam will need to be removed by barges and excavators over the next seven days.
The damage to the water chute means that the water is not flowing fast enough to clear any of the rubble from the plunge pool at the bottom.
The debris is also blocking the water flow, meaning that it is not moving with sufficient force to generate enough electricity when it reaches the power plant, which is currently not operating.
No completion date has been offered for the clean-up, which could cost hundreds of millions of dollars.
The clear-up team are still assessing the damage as they work, so authorities are not yet sure if they will be able to clear it in the five to seven days the spillway will be shut off, running from Monday.