The area was, in the past, recorded in the US Census Bureau as a rural community; however, Idria has become a ghost town since the closing of once lucrative mining operations in the early 1970s.

[2] In 1990, the United States Environmental Protection Agency (EPA) investigated the mercury contamination level in soils, groundwater, surface water, and air of Idria, and concerned with the impact that the mining industry had had on the local environment.

Mercury, a major component in the cinnabar-rich rocks in Idria, could be economically extracted to support nearby gold mining and processing operations.

Bordering this plug of rocks is the Upper Cretaceous Panoche Formation consisting of silty-shale and concretionary sandstone up to 20,000 feet thick.

Since Idria has natural mercury reservoirs, it is important to factor in these background emissions in measuring the total impact from mining itself.

[4] The leftover ores or calcines from this process were piled along with other waste rock, totaling between 0.5 and 2 million tons and cover over 40 acres of mining ground.

The issue was compounded by the proximity of 2,500 feet of the creek's flow to the calcine tailing piles, contaminating the water with mercury and other metals including aluminum, arsenic, copper, iron, and zinc[3] Although there are few regularly occupied developments near the mine, there is a significant ecological concern associated with the uncontrolled drainage.

[5] A small concentration of mercury can harm aquatic organisms, poison water streams and surrounding ecosystems in highly contaminated areas like Idria.

[8] Waters enriched in mercury were detected as far as 20 miles downstream from the mine in Panoche Creek, at levels toxic to aquatic life.

[4] The lengths of San Carlos, Silver, and Panoche Creek run through a regionally unique wetland habitat housing several threatened and endangered species, including the California red-legged frog and the steelhead trout.