Landfills and impoundments

Landfills are the final repositories for unwanted or unusable wastes. Until the middle of this century, nearly all wastes were discarded in open, unengineered dumps. Waste was often burned to conserve space. Topographical anomalies that lended themselves naturally to dumping were typically selected for dump sites. The most common waste dumps were natural depressions (creeks, low-lying areas, and flood plains) that were otherwise of little use and mined-out areas, e.g., sand or gravel quarries. The practice of open dumping changed little, until a few decades ago.