DENVER (AP) — The U.S. Environmental Protection Agency is installing a barrier and valve inside an inactive Colorado mine to prevent another surge of toxic wastewater like a 2015 blowout that contaminated rivers in three states. The 12-inch (30-centimeter) valve will regulate wastewater pouring from the Gold King Mine in the San Juan Mountains of southwestern Colorado, where the EPA inadvertently triggered a wastewater spill while excavating at the mine entrance in August 2015. That spill released 3 million gallons (11 million liters) of wastewater containing aluminum, iron and other heavy metals and instantly became a major embarrassment for the EPA.