Conservation groups have filed a formal notice of their intent to sue an international mining company to protect critical desert streams and washes in southern Arizona’s Santa Rita Mountains. Notice says Toronto-based Hudbay Minerals is violating the Clean Water Act by dumping dirt and rocks into a wash at the company’s proposed Rosemont Copper World Expansion, on private land on the western slope of the Santa Rita Mountains. Federal laws require a permit before discharging anything into US waterways.Rosemont, a Hudbay subsidiary, intends to ramp up grading and clearing the 3,500-acre site southeast of Sahuarita this month, but it has not applied for a Clean Water Act permit with the US Army Corps of Engineers.Aerial photos taken earlier in April show soil and rocks spilling into and filling portions of a wash, part of a network of ephemeral streams that flow across the proposed mine site and downstream to the Santa Cruz River.Rosemont’s original copper mine plans, on the east side of the Santa Rita Mountains, have been stymied by multiple losses in court. The westside expansion proposal calls for two new open pits and three tailings waste piles, where it would dump at least 64 million tons of waste. It intends to fill the washes and streams throughout the mine site and connect to its proposed Rosemont Copper mine.Washes and other ephemeral streams like those on the mine expansion site play a vital role in maintaining the chemical, physical and biological health of waters downstream. In addition to the buried wash, the Center’s aerial photos showed a vast network of roads, grading and hillside excavation.The 60-day notices are required before filing a lawsuit to compel the company to comply with the Clean Water Act. Rosemont can avoid the violations by suspending work at the site.