Miami, located only two degrees above the Tropic of Cancer, is a subtropical city located on flatlands that were once home to pine and palmetto trees. Its coastal area consists of sandy beaches, and even the region's interior is only thinly wooded. Lake Okeechobee, 145 kilometers (90 miles) north of the city, is linked to Miami by manmade canals.
During the wet season, Greater Miami must contend with problems caused by tropical storms and hurricanes. Among the worst is sanitary sewer overflow, exacerbated by the city's low terrain: its highest elevation is only 12 meters (40 feet) above sea level, and the groundwater table is only one to two meters (three to six feet) below the earth's surface. When it rains, water is sucked through the sandy earth and further still into the cracks of some of the sanitary sewer pipes crisscrossing beneath Metropolitan Dade County. When unexpected water makes its way into these pipes, the system becomes overloaded.
Downtown flooding in the late 1980s and early 1990s caused raw sewage to spill into the Miami River, prompting Metropolitan Dade County to sign consent decrees with the Environmental Protection Agency (EPA) that mandated comprehensive sanitary sewer system rehabilitation. The metropolitan area's water and sewer department is in the midst of a $1.1 billion sewer upgrade project scheduled for completion by 2002. Pumping station capacities will be expanded; three wastewater treatment plants will be upgraded; and studies of utility operation will be conducted.
Dade County's Department of Solid Waste Management collects waste from more than 260,000 residential addresses, disposing of approximately 2.1 million metric tons (2.3 million tons) annually. Its disposal system consists of one resources recovery facility and associated ash monofill, two landfills, and three regional transfer stations.