Water treatment implications after the High Park Wildfire, Colorado

This study evaluated effects of the 2012 High Park Wildfire in the Cache la Poudre River Watershed in Colorado on source water quality and water treatment. The formation of disinfection by-products (DBPs) was evaluated by treating water samples with chlorine following uniform formation conditions. The efficacy of alum coagulation for reducing dissolved organic carbon (DOC) and DBP concentrations was also evaluated. Postwildfire thunderstorms and spring snowmelt increased DOC and DBP concentrations relative to base-flow conditions. Alum coagulation effectively reduced DOC concentrations (by 30–60% at a dose of 50 mg/L) and DBP formation (i.e., total trihalomethanes reduced by 60–80% at a dose of 50 mg/L). The Fort Collins water treatment facility responded to the High Park Wildfire by increasing environmental monitoring, using multiple water supplies, and constructing a presedimentation basin to effectively deliver high-quality drinking water to its customers in the year following the fire.