100. Landfilling of mill residual materials must be done at a site where the hydrogeological conditions are such that the leachate flows on the surface or infiltrates the soil and has a migration time of more than 5 years to travel 300 m or to reach any well or spring supplying drinking water situated within 300 m, unless the leachate has already resurfaced. In the latter case, the leachate must have circulated in the soil for more than 2 years at an average speed of less than 150 m per year.