Solid waste should not be placed where there is a potential for direc
contact with the groundwater table. Also, major recharge zones should be
eliminated from consideration, particularly in areas overlying
separation between the bottom of the fill and the highest known level of
groundwater should be maximized. State and local regulation may stipulat
minimum acceptable separation. A 5-foot (1.5-meter) separation is a comm
regulatory stipulation, but may vary from state to state.
Sources of data on groundwater quality and movement include the U.S.
Geological Survey (USGS), local well drillers, USDA soil surveys, state
geological surveys, state health departments, other state environmental a
regulatory agencies, and samplings from nearby wells. USGS maintains a
National Water Data Exchange (NAWDEX) which is developed from the Nationa
Water Data Storage and Retrival System (WATSTORE) and contains EPA as wel
as USGS well and groundwater data. NAWDEX reports can be obtained from U
headquarters on magnetic tape or computer printout or from any of the 79
regional USGS, NAWDEX, offices located in most states. Contact USGS
headquarters for regional office locations or NAWDEX reports.
Determining the hydraulic gradient at a site is important in
ascertaining the rate and direction of groundwater movement and whether o
not hydraulic connections to surrounding aquifers exist. The hydraulic
gradient can be determined by noting the depth to groundwater in nearby
wells or borings, calculating the elevation of the groundwater, and
drawing contour lines that connect wells of equal groundwater elevations.
Further background information on groundwater can be obtained through
onsite drilling. At least three wells (and normally more) are needed to
determine the direction of groundwater movement. Large sites, sites with
complex hydrogeology, and relatively flat sites require more borings than
small and steep sites. An experienced hydrogeologist should participate
can planning the drilling program and in interpretation of background
research and exploratory drilling.
7.2.8 Vegetation. The amount and type of existing vegetation on a
prospective site should be considered in the selection process. Natural
vegetation left at the site can serve to reduce dust, noise, odor, and
visibility problems. Where extensive clearing and grubbing of vegetation
necessary, costs may increase significantly. Also, some areas may be
habitats for endangered plant (and animal) species.
Vegetation can be planted during site operations to screen the site.
Upon site closure, the filled areas can be replanted with either native o
introduced species. The ability of soil, used as the final cover, to
support planned revegetation should therefore be considered.
7.2.9 Site Proximity and Accessibility. A landfill site should be locat
as close as practical to the waste generation centroid since hauling cost
are a significant part of total solid waste management costs.
The haul routes to the prospective sites should be over major roads to
the installation to the maximum extent possible. The proximity of the si
to these major roads is also a consideration since a well-graded onsite
access road must be constructed from the haul route to the disposal area.