In case of a spill, secondary containment provides a barrier between storage containers, equipment, piping, or transfer areas that hold or use hazardous materials and the land surface. Secondary containment methods can include impervious dikes, berms, or retaining walls; curbing, culverts, gutters, or other drainage systems; weirs; booms; barriers; spill diversion and retention ponds; sorbent materials; drip pans; and sumps and collection systems.