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Leona Heights Sulfur Mine

Posted February 13, 2015

E2C Remediation Project 6

E2C Remediation Clean-Up

From as early as 1900 through the 1920s, the Leona Heights Sulfur Mine operation was mining pyrite from the sites bedrock and used to manufacture sulfuric acid. Natural water flowing over and through the mining waste subsequently dissolves sulfur and other types of metals, leaving an acid drainage that flows into the nearby Leona Creek. Because the creek receives most of its water from groundwater seep, during heavy rain events, runoff from the watershed upstream reacts with the mining waste. This further increases the amount of acid mine drainage flowing into the creek, and water samples taken from this site have had pH levels as low as 3.

The solubility of metals present in the mining waste increases with the introduction of acidic water, causing the leaching of heavy metals into Leona Creek. You can see that the Leona Creek has the tell-tale orange color associated with acid mine drainage, and it does in fact, contain high levels of cadmium, copper, nickel, mercury, arsenic, and zinc.

E2C has proposed the following actions be taken to effectively remediate the site:
• Removal of mining waste from Leona Creek and surrounding areas
• Grade and compact mining wastes. Install a subsurface drainage system beneath the compacted mining waste to increase stability.
• Isolate the mining wastes from the water by covering with a geomembrane liner and a vegetated soil layer.
• Create new discharge point within the creek channel by rerouting the seep drainage from its current location.
• Reinforce steep slopes surrounding the Leona Creek to improve consolidated mining waste stability.
• Construct a stable creek channel that can accommodate a 100-year design storm and support natural sediment transport. Incorporate cascades and step-pools that mimic natural creek channels on steep slopes.

These outlined actions for consolidation, revegetation, capping, and drainage improvements are designed to substantially reduce the contact of storm water runoff and mining wastes, effectively reducing the metal and excess sediment load in Leona Creek.