Naturally occurring acidity in the vicinity of a sulfide ore deposit: Wilson Springs mine, Hot Springs, Arkansas

Acid rock drainage (ARD) is often a regulatory concern in the vicinity of sulfide ore deposits. In many cases it is simply assumed that acid entering the environment is somehow the product of ARD. Measurement of pH in groundwater or seeps and springs that are below the national secondary drinking water standard of 6.5 is taken as evidence of ARD processes that are occurring as a result of mining of the sulfide ore deposit or as a result of natural sulfide oxidation at the site. Geologic evidence and geochemical modeling indicate that average pH readings of near 5 in several seeps and springs in the vicinity of the Wilson Springs vanadium mine site near Hot Springs, Arkansas are unrelated to sulfide oxidation. Instead, low pH is likely the result of natural rainfall in the area that has a pH near 5, and an aquifer matrix that has no buffering capacity.