The impact of microbial activity on the hydraulic properties of fractured chalk was investigated on a laboratory scale model.The experiments were conducted on six fractured chalk cores (20 cm in diameter, 23-44 cm long), each containing a single natural fracture embedded in a porous matrix.Following the initial hydraulic characterization of the fractures, a nutrient solution containing 2,4,6-tribromophenol (TBP) as a synthetic model contaminant was continuously injected into the fractures.The various fractures were operated over 250-630 days, under different conditions including several flow...