Colorado Gov. John Hickenlooper is expected to formally endorse a Superfund cleanup Monday for 48 old mining sites, including one that sent wastewater into rivers in three states last summer.

The Environmental Protection Agency would oversee the project but won't proceed without support from the governor and local officials. San Juan County and the town of Silverton endorsed the cleanup last week.

Hickenlooper spokeswoman Kathy Green said Sunday the governor is preparing to give his blessing to the southwestern Colorado cleanup.

The EPA inadvertently triggered the release of 3 million gallons of wastewater from the inactive Gold King Mine on Aug. 5 during preliminary cleanup work. Rivers in Colorado, New Mexico and Utah were polluted.

Water utilities briefly shut down intake valves and farmers stopped drawing from the rivers.