The Stockpile Runoff Project addressed environmental concerns regarding the quality of runoff water from salvaged pavement stockpiles. Three experimental stockpiles were studied, one pile consisted of coarse concrete, a second consisted of fine concrete material, and the third consisted of salvaged bituminous material (recycled asphalt product) obtained from a pavement milling project.
The leachate water from the piles flowed through a sampling and flow monitoring system with data loggers and automated sequence samplers. Composite water samples were analyzed using EPA approved methods and quality control protocols. Comparing the observed median values for the stockpile runoff with Minnesota standards for surface waters, the pH exceeded and chromium may have exceeded the standards. Although there are sediment and leachates emanating from stockpiles, the long-term concern reduces to suspended and dissolved solids, and pH. Polynuclear aromatic hydrocarbons (PAH) concentrations from the bituminous millings pile were near or below detectable limits.
Planning for stockpile storage sites should include management practices of controlling runoff similar to those that are used for construction sites. Berms, straw bales, grass or other filter channels, and locating stockpile sites some distance from surface waters may be appropriate practices. Possible impacts on the ground water system should be considered.
