Mud Day 2011, Westland, Michigan, United States

Problems
Clay soil can pose problems for traffic when moisture is present. A road built upon such soil may become stable over time as the packing of the soil will make it more water-resistant. However, any attempt to grade it can be disastrous, since excess water can then enter the surface and will be worked in by traffic, transforming portions of the road into a mud bog that can trap vehicles. The typical solution in road building is to add layers of crushed stone. The stone particles will interlock and distribute the weight of a vehicle over a larger surface area. Proper drainage is also essential when low spots are encountered by the road, usually requiring the addition of culverts to pass water underneath the elevation of the street.
Buildings constructed upon clay soil must also be properly drained around their perimeter, particularly where a perimeter foundation (rather than a monolithic slab) is used. As clay will expand and soften when moisture is added, the resultant mud will squeeze out from underneath the foundation, however, in the next dry cycle it will contract, but the clay squeezed out will not return. Over a number of such cycles the foundation can sink in the moisture-cycled locations, possibly causing both wall and foundation cracks. Maintaining a constant moisture level in firm soil is important and can be effected by appropriate landscaping and landscaping maintenance. Where drainage is toward a building a French drain may be installed to route water around the building.