Geology Reference
In-Depth Information
provide basic data and resource capability maps to the
planner. The geologist may also assist the planner in
integrating them with other data and maps to produce
resource suitability maps which will be the basis for a
long-range regional plan. Such a plan is subject to
change but does provide guidance in making wise
decisions about land use.
be considered in selecting a site for a sanitary landfill.
These include the following:
Climate.
In cold climates freezing of the soil restricts
excavation and availability of cover material. A low-
lying site may be undesirable in areas of heavy rainfall
because of flooding and muddy working conditions.
Windy sites need special consideration because of dust
problems and blowing paper.
Bedrock geology.
The type of bedrock is important;
sandstone, conglomerate, and limestone could rapidly
transmit water containing pollutants, while shale and
igneous and metamorphic rocks would not. Rock
structures (e.g., faults and joints), the dip of rock strata,
and underground mines must be considered.
Hydrology.
Possibilities of groundwater pollution from
leachate and surface-water pollution from leachate and
runoff, the seasonal fluctuation of the water table, and
the direction of groundwater movement are all impor-
tant factors. Well-head areas, recharge zones for
aquifers, and floodplains should also be considered in
siting landfills.
Topography.
Surface slopes before and after develo-
pment must be considered, since erosion of cover
materials may expose trash. Floodplain proximity and
flood level must be taken into account, as well as the
effects of topography on surface and underground
drainage.
Regolith and soil conditions. A
sufficient quantity of
easily workable compactible cover material must be
available. The type of regolith (i.e., alluvium, glacial
drift, clay soils, etc.) must be considered.
Other factors in site selection include economics,
transportation routes, engineering techniques to reduce
offsite impact, adjacent historical, cultural, and environ-
mental values, and politics.
PART A. SITING A SANITARY LANDFILL
Management of municipal solid waste presents a
growing problem for urban regions. The sanitary land-
fill is now the most common way to "dispose" of this
waste, although incineration, composting, and tradi-
tional recycling are also used. Municipal solid waste
includes food waste, beverage containers, yard and
garden waste, automobiles and parts, appliances, fur-
niture, newspapers, and disposable diapers, etc. As
this waste decomposes it produces leachate, a nasty
liquid that contains components of the soluble materi-
als in the landfill—from heavy metals to organics.
Leachate in poorly constructed landfills can travel
beyond the sanitary landfill causing pollution of soils,
groundwater, and surface water. Methane and other
landfill gases may cause problems when they migrate
underground into surrounding buildings.
The number of geologically suitable sites for
sanitary landfills is limited. As a result, landfill sites
are expensive to acquire and to engineer for environ-
mental protection. In 1970 in North America, 85 per-
cent of municipal solid waste was disposed of in a
dump, many located in old pits and quarries. In these
dumps waste was not covered regularly; open burn-
ing and leachate runoff were common. About this
time, the environmental damages and hazards from
these dumps were recognized and legislation was
enacted for sanitary landfills. A sanitary landfill is a
method of disposing of refuse on land without creat-
ing nuisances or hazards to public health or safety.
Engineering techniques are used to confine the waste
to the smallest practical volume, to cover it daily, and
to prevent leachate, gas, blowing debris, and rodent
and odor problems.
The sanitary landfill system is expensive. Dis-
posal fees and limited space in some areas make it
economical to ship solid waste many miles by truck
or train for disposal in a landfill. Waste from New
York City goes to Ohio and other states; Toronto,
Ontario, has sent some of its waste to Michigan. In
addition to the geologic factors that control the siting
of landfills, social factors that must be considered
have also increased costs for disposal sites. The terms
NIMBY (Not In My Back Yard), LULU (Locally
Unwanted Land Uses), and NIMTO (Not In My Term
of Office) exemplify the social response to proposed
landfills.
QUESTIONS 17, PART A
Trashmore is a hypothetical city of about 40,000 in the Great
Lakes region of North America. The gently rolling landscape
has been glaciated and the regolith contains silty-clay till,
outwash gravels, glacial lake deposits of clay, and modern
alluvium over bedrock at depths of 0 to 100 feet. The bedrock
consists of limestone and shale formations. Trashmore has a
sanitary landfill that will run out of space in two years. As a
member of Trashmore's City Council you have been asked to
assist the regional planners in selecting a suitable site for a
new sanitary landfill. You consult a portion of a geologic
map and cross section of the region (Figure 17.1) and recog-
nize three excavated sites. If one of these pits and quarries
could be used, you think you could save on excavation costs.
1. What geologic resource (rock or sediment) was extracted
at each of the three sites?
State Aggregate:
