EVALUATING STORMWATER IMPACTS AND THE FIRSTFLUSH PHENOMENON ON SELENIUM CONCENTRATIONS IN A SURFACE COAL MINE DISCHARGE IN WEST VIRGINIA

摘要

Selenium in surface water discharges is a concern of the Appalachian surface coal miningrnindustry. Many National Pollutant Discharge Elimination System (NPDES)-permitted outlets inrnWest Virginia must meet stringent water-quality-based effluent limits (WQBELs) for totalrnrecoverable selenium: 4.70 micrograms per liter (μg/L) monthly average and 8.20 μg/L dailyrnmaximum. This study included a site-specific sampling plan and rigorous field procedures forrndiscrete sampling to clearly show the dilution effect of stormwater on selenium concentrations inrnreclaimed surface coal mine discharge. The study also showed that the first-flush magnituderndepends on site-specific conditions; precipitation volume, intensity, and duration; and pollutantrntype. Applying the dilution effect and the first-flush phenomenon will help companies developrnstormwater management alternatives to achieve consistent compliance with selenium effluentrnlimits. Further understanding and knowledge gained from case studies of stormwater impactsrnand characterizing selenium at surface coal mine sites will continue to increase over time.