MUNICIPAL SOLID WASTE MANAGEMENT AND DISPOSAL - Environmentally Conscious Materials Handling - page 153

with soil. These safeguards are intended to prevent groundwater contamination.
However, it still possible that the system will fail and leachate will contaminate
the groundwater by organics and heavy metals.
Solid waste disposal in landfills is highly regulated. The federal government,
through the Resource Conservation and Recovery Act (RCRA), specified that
landfills must meet certain minimum standards. In states whose RCRA Subtitle
D programs have not been approved by the U.S. EPA, landfill must be designed
with a composite liner, a leachate collection system, and point of compliance
(POC) at the unit boundary. In states whose RCRA subtitle D programs have
been approved by the U.S. EPA, the landfill design must be approved by state
to ensure that maximum contaminant levels (MCLs) will not be exceeded in the
uppermost aquifer at the POC, and the POC must be no more than 150 meters
from unit boundary and must be on the property of the owner. There are also
siting limitation for a landfill. For example, landfills must be 5,000 to 10,000 feet
from an airport and it cannot be located in wetland, in a 100-year flood plain,
or on fault lines. Landfill operations also must be extensively monitored by the
operator through RCRA regulations. Additionally, the regulatory standards limit
the amount of material that is allowed to be released into the groundwater and
into the air.
Figure 5.4 shows the number of MSW landfills in the United States between
1988 and 2006. The number of MSW landfills decreased substantially over the
past 18 years, from nearly 8,000 in 1988 to 1,754 in 2006. The distribution of
these 1,754 landfills is 133 in the Northeast, 676 in the South, 425 in the Midwest
and 520 in the West. Although the number of U.S. landfills has steadily declined

Number of Landfills in the United States, 1988 to 2006

9,000

7,924

8,000

7,379

7,000

6,326

5,812

6,000

5,386

5,000 4,482

3,558 3,197 3,091

4,000

3,000 2,514

2,314 2,216

1,967 1,858 1,767

1,754 1,754

2,000

data not
available

1,000

0

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Figure 5.4 The number of U.S. landfills from 1988 to 2006 (U.S. EPA 2007)