National Dam Safety Program. Pea Ridge Mine Dam (MO 30473), Mississippi - Kaskaskia - St. Louis Basin, Washington County, Missouri. Phase I Inspection Report

摘要

Pea Ridge Mine Dam is an active tailings dam. Unlike most tailings dams in the area which were constructed for barite ore processing operations, this dam was constructed for an iron mining operation. Cobber reject is the primary material used to construct the dam. It is trucked from the plant to the site and dumped on the crest. The cobber reject is then spread over the crest and downstream slope. Beneath the dam are a series of drains. These drains consist of trenches, about 20 ft wide and 10 ft deep, excavated in foundation rock, filled with cobber reject and parallel to the crest. Water from these trenches is conveyed to the toe drains. There are no spillways or regulating structures at the dam. The inspection and evaluation indicate that the dam is in generally good condition. In its present configuration, the downstream slope is near incipient failure as its inclination is that of the angle of repose of the cobber reject. However, due to the 110-ft wide crest and present 38-ft elevation difference between the tailings and dam crest, this is not considered a safety hazard. Hydrologic/hydraulic studies indicate that the dam will not be overtopped by the 1 percent probability-of-occurrence flood (100 yr flood), or by the Probable Maximum Flood.