This is the fifth lesson of ten that make up
the new
correspondence course from the University of Wisconsin
Because a landfill can now be designed with a geosynthetic
liner to replace or back up a soil liner someone might feel that
a landfill could be sited anywhere. While new technologies can
increase the technical acceptability of some potential landfill
sites, there are a variety of factors that must be
assessed when determining site acceptability. Sound technology
alone will be an insufficient basis on which to evaluate and
compare alI potential sites.
There are many other factors to consider, including public
opinion, health and safety, hauling distance, accessibility,
climate, drainage, zoning and hand use, and economics. No matter
how technically sound a facility design appears to be, there will
no doubt be public interest and even hostility that must be
addressed in the site evaluation process. This lesson will
provide a procedure for evaluating potential sites and seeking
public input.
Possibilities for potential sanitary landfill sites are:
A site in an area zoned for industry;
Walsh and O'Leary are solid waste
specialists with
the university of Wisconsin-Madison
An ideal l sanitary landfill will have the following
properties:
Conforms with land use planning of the area:
The federal Resource Conservation and Recovery Act of 1976
(RCRA) established general standards for landfill siting,
including siting in a floodplain, site impacts on groundwater
quality and endangered species, and control of safety and surface
water discharges.
RCRA standards provide, for example, that solid waste facilities
located on floodplains not restrict flood flows to the extent
that the landfill poses a hazard or is in danger of being washed
out. Groundwater standards relate primarily to the control or
management of leachate. Safety standards cover explosive gases,
fires, bird hazard to aircraft, and the prevention of
unauthorized access.
New landfill regulations promulgated by the U.S. Environmental
Protection Agency pursuant to Subtitle D of RCRA are expected to
expand landfill location restrictions. Pursuant to Subtitle D,
landfill development will be restricted in some areas, including
wetlands, unstable soils such as Karst terrain or
landslide-susceptible areas, fault areas, seismic impact zones,
and land in the one-hundred-year flood plain or in proximity to
an airport. Except for fault zones landfills would not be
prohibited from these areas but would be subject to special
siting restrictions and/or performance standards. The location
requirements would apply to new municipal solid waste landfills
and expansions of existing landfills.
Other federal agencies also have standards that will affect the
identification of potential sites. For example, the Federal
Aviation Administration (FAA) has regulations requiring that
landfills must be located more than 10,000 feet from the end of a
runway serving a commercial airport. This (FAA) restriction has
stopped development of some landfills and should not be ignored
in site s earch considerations.
Most state governments have laws regulating solid waste disposal
and require state approval for site construction and operation.
These laws describe the procedures for obtaining site approval
and limitations on site location.
In Wisconsin, for example, regulations prohibit sites within 300
feet of a navigable stream, within 1,000 feet of a navigable lake
or pond, within wetland areas, within floodplains, or within
1,000 feet of a state or federal highway or a park (unless berms,
fencing, or landscaping prevent visibility from the road or the
park). The regulations also describe the types of maps, reports,
geological and hydrological data, and other information needed
for site evaluation.
Local governments often have regulations affecting site
identification. Many local governments have zoning that will
restrict certain types of activity in designated areas. While
zoning for a particular site may be changed by the governing
board, disagreements between different jurisdictions and citizen
opposition may prevent the development of a landfill in certain
areas.
Besides being familiar with the laws and regulations, it is
important to get to know and work with people who administer the
regulations. These people can help interpret and apply the rules
and often will assist iii locating a landfill site.
As a landfill developer begins the process of searching for a
new landfill site, the question arises as to when to make the
search process public. Since public knowledge invites public
interest and often public opposition, many developers try to keep
decisions secret until a final choice is made, In addition to the
fear of public opposition, prices for land and soils, as well as
other economic factors, can be affected if the public knows a
site is being sought.
While it may be basic human nature to avoid controversy as long
as possible, many now feel that waiting until a final site is
chosen, known as a "decide-announce-defend" policy,
leads to maximum public opposition. The opposition is generated
because neighbors and others feel a decision affecting their
interests has been made without their input, leaving them
frustrated and angry. Hiring lawyers to fight is often the
result.
Others recommend getting the public involved early in the
process. This approach uses the search process to educate the
public about the difficult choices that must be made and about
the degree of effort and expertise that the developer is applying
to make a reasonable decision. The policy forces the involved
public to help make decisions from among available alternatives.
A description of this approach, called the issue
evolution/educational intervention model, is set forth in Figure
1.
Obviously, this approach is not trouble free. Working with the
public during the search process is time-consuming and difficult.
Some interested participants in the process may be totally
negative or may attempt to play neighbors near one site against
neighbors at another. Since some public involvement in siting is
usually mandated by state or local regulations, the developer
must devise an approach that results in increased public support
for the landfill project. This will be a formidable task.
The process for siting of a new landfill can be divided Into the following steps:
The community or private company developing a landfill should clearly identify project goals. Each entity will have specific needs to address, but goals common to many projects will include:
Clear objectives make it easier to communicate with the citizens, either supportive or oppositional, and with political officials.
Using population data and current solid waste generation
rates, the developer should project the quantity of waste the new
waste disposal facility will receive. This analysis should
include a projection of future population growth and commercial
and industrial development.
To be reliable, the analysis of waste quantity generation rates
should reflect any plans for recycling or resource recovery
projects reducing the quantity of waste ultimately being land
disposed.
When more than one landfill will serve an area, it must be
determined that the new facility can compete economies with
alternative sites. Recent indications that economies of scale
favor the development of large sites make it imperative that the
cost of hauling longer distances to competing large landfill
sites be compared to the economies of maintaining a more
expensive local site.
The product of this analysis is an estimated waste quantity
projected to be received at an assumed tip fee. If, after being
placed in operation, the planned landfill is found to require a
higher tip fee to be economically viable, the quantity of waste
received may be less than originally estimated. A site that
receives substantially less waste than originally planned my be
uneconomical to operate.
After establishing the size of a fill site required to handle
the specified service area for a certain number of years, the
search for potential sites can begin.
Methods used in locating appropriate sites can range fro m
informal surveys to very extensive mapping studies. Objectives to
potential sites can be partially rebutted by preparing a detailed
analysis of all available sites in the area with the best sites
selected for further detailed engineering study.
The potential site's suitability is rated for various factors.
These studies are most important for publicly owned facilities
where each step in the landfill development will probably be
subject to scrutiny.
Entities developing private sites may also find it beneficial to
show opponents that a large number of potential sites have been
evaluated before selecting a particular site for detailed study
and possible implementation.
Potential sites must be la areas that are suitable for
landfill. development. operation and end use of a landfill site
should also conform to long-term land use goals.
Most areas have projected land-use plans for 10 to 20 years. la
the absence of land-use maps, air photographs can be used to
assess current land-use patterns.
Industrial areas may seem suitable for a landfill site, since
heavy equipment is required and significant traffic is generated.
However, the landfill may not be compatible with industrial
operations when completed. Differential settlement within the
finished site may limit its use as support for buildings years
after completion.
If properly designed and operated, a completed landfill could be
used as an industrial site, but most often, completed landfills
are used as open space or recreational areas.
Areas with habitats of endangered plant or animal species, virgin
timber land, wildlife corridors, unique physical features, and
historical and are archaeologic sites should be avoided in
locating a landfill facility. The development of a landfill in
one of these areas may result in a detrimental impact which from
an overall viewpoint outweighs the benefits of a successfully
operated landfill.
Soil maps, prepared by the U.S. Department of Agriculture's
Soil Conservation Service, provide very useful information about
potential landfill sites. These maps identify soil profile
characteristics to a depth of five feet.
On these maps, soil-type plus other important features such as
roads, railroad tracks, buildings, and surface waters are shown.
Soil is important in landfill development for three reasons:
Cover: material used to cover the solid waste daily and
when an area of the landfill is completed. The permeability of
the final cover will greatly influence the quantity of leachate
generated.
Migration control: the material that controls the movement
of leachate and methane gas away from the landfill. An
impermeable formation will retard movement; a permeable soil will
provide less protection and may necessitate the installation of
additional controls within the landfill.
Support: the soil material below and adjacent to the
landfill must be suitable for construction. It must provide a
firm foundation for liners, roads, and other construction
activities.
The SCS has data available on the soil types of many, but not
all, areas of the United States. Land with a potential for solid
waste disposal can be located by determining the SCS limitations
of the particular soil for landfilling. The SCS has designated
whether each soil has "slight," "moderate,"
or "severe" limitations for use as a landfill site.
ldeally, sites should be located in silt and clay soils which
restrict leachate and gas movement. A landfill constructed over a
permeable formation such as gravel, sand, or fractured bedrock
can pose a significant threat to groundwater quality.
If the only areas available have less than optimum conditions for
landfill construction, then soils may need to be hauled to the
site for liner and cover construction. Alternatives to importing
soil include installation of a geomembrane cover and liner or
constructing a zone of saturation. (In the June 1991 Waste
Age, Lesson 3 described the options available for methane
migration control.)
Some site identification studies have established separate
procedures for rating the soils in the region being considered
for landfill development. For example, the SCS soil ratings
system classifies sites with depth to groundwater of less than
six feet as having a severe limitation.
In a heavy textured or clay soil, where water movement is slow
and tile groundwater table is shallow, a groundwater collection
system will allow for the successful operation of a landfill.
Normally this type of soil would be excluded from consideration,
but by establishing separate criteria, and providing specially
designed and engineered features, a landfill can be constructed.
Use of criteria developed specifically for a landfill siting
study allows incorporation of local conditions and concerns into
the evaluation process. Table 1 shows the criteria developed for
a landfill siting study conducted in Dane County, Wis. Regulatory
standards may also be incorporated into the landfill site
identification process at this stage.
While the criteria shown in Table 1 apply to more factors than
those distinguishable on soils maps, the most efficient approach
is to apply the criteria to the soils maps before evaluating
other sources of data.
During tile preliminary site identification phase, floodplain
maps can also be used as resource documents. If no floodplain
maps are available, soils maps may be employed to roughly
delineate areas subject to flooding. The use of soils maps,
however, cannot fulfill the need to conduct a floodplain analysis
during a later phase of the site selection process.
A major limitation in the use of soils maps for selecting
potential sites is that the maps describe the soil to a depth of
only five feet. Therefore, a site that initially had been judged
to be suitable during the soils map work may be deemed unsuitable
as a result of data collected at depths greater than five feet.
The hand's contour and subsurface formations are obviously
important for the development of a landfill. Surface features
will affect the layout of the landfill and drainage
characteristics.
Subsurface formations and groundwater conditions wilI influence
the landfill’s design features, such as leachate collection
and liner requirements. The formation’s geotechnical
characteristics will determine its as a construction material.
Maps that show topography surficial deposits, geologic formations
bedrock depth and type, and depth to groundwater can be employed
to further define areas that are suitable for landfill
development. These maps are available from U.S. Geological Survey
(USGS).
Contour maps show drainage patterns adjacent to and through
possible disposal sites. Areas of excessive slope can be
delineated Areas with direct overland flow from a potential site
to surface waters must be carefully evaluated. Direct discharges
must be prevented and the landfill designed and operated to
accomplish protection of the lake or stream.
The usefulness of maps describing geologic features will depend
on the scale and detail of the published maps and reports. Often
these maps cover a large area and, consequently show limited
detail.
When tabulating this type of data, certain assumptions about
potential sites may be necessary. These assumptions can be
checked out later by conducting soil borings if the potential
site is found to be a good candidate for a landfill.
Several procedures may be employed to collect and tabulate the
necessary data. The most informal approach is to identify a list
of potential sites based on personal knowledge of the area being
studied. This approach limits the land area to be considered, but
presents a major handicap: the distinct possibility of
overlooking suitable areas.
A more thorough identification process is to apply previously
described criteria to the entire study area. This is accomplished
by preparing a series of map overlays. Each overlay identifies
land areas with moderate or severe limitations in regard to a
particular criteria. A USGS quadrangle map is often employed as
the base map. The overlays shown in Figure 2 are prepared on
transparent plastic sheets and placed over the base map.
Areas with slight limitations show up as clear areas on the map
overlays. After the overlays are placed on the base map, only
those areas with slight limitations for all identification
criteria will show through from the base map.
Areas with moderate limitations are shaded lightly and areas with
severe limitations are shaded darker. When the overlay work is
completed, several areas with only slight limitations for all
criteria should be identifiable as being the best potential sites
for a new landfill.
An alternative to map overlays is the numerical rating of land
areas. The study area is divided into square 40- or 60-acre
parcels. Each parcel is assigned a numerical score for the
individual site identification criteria factors. The numerical
data generated by this procedure can easily be handled by a
computer to evaluate the overall suitability rating for each area
and generate printouts showing areas with slight, moderate, and
severe limitations.
An advantage to this approach is that the numerical data can be
manipulated to give greater importance to different factors.
Sites with the best numerical score are designated for detailed
study and consideration as a landfill site.
The fourth step in the site selection process is to conduct a
detailed investigation of the sites designated as most suitable
during site identification.
Most of the new data collected concerns hydrogeologic
characteristics of the potential site or sites. This includes
drainage patterns, geologic formations, groundwater depth, flow
directions, and natural quality and construction characteristics
of site soils.
In addition, data about existing land use, surrounding land
development, available utilities, highway access political
jurisdiction, and land cost is tabulated.
Subsurface investigations soiled be conducted at those potential
sites with the most desirable characteristics.
Subsurface investigation consists of borings below and
adjacent to the proposed site to determine subsurface conditions.
The number, location, and depth of the soil borings are
determined in part by local and state regulations, and more
importantly by the hydrogeology of the site. The number of
borings needed to accurately define conditions increases with the
size and geologic complexity of the site.
As the boring is being conducted, a soils or geologic specialist
will collect samples for testing. Normally soil samples are
tested for grain size distribution and moisture content, and
classified by soil type.
Soil that may be later employed for liners and landfill covers
wilI also be tested for permeability, Atterburg limits, moisture
content, and moisture density relationship. This data is used to
prepare a boring log as shown in Figure 3.
Borings should extend at least to a depth of 20 feet below the
expected base elevation of the landfill. A portion of the borings
should terminate below the water table if it is greater than 20
feet below the anticipated base of the site. Bore holes can
subsequently be converted to groundwater monitoring wells to
observe the long-term water table fluctuations and to facilitate
groundwater sample collection.
Measurement of water levels in the wells will show the direction
of groundwater flow. Flow will be from wells having higher
groundwater levels toward those wells with lower levels. The
water levels can be plotted and contoured on a map that also
shows adjacent land uses. Superimposing flow lines on the
contours will show where leakage from a potential landfill may
migrate. An example is shown in Figure 4.
In addition to horizontal movement of groundwater and potential
contaminants, groundwater may move vertically within the
subsurface formation under the site. Vertical movement can be
detected by installing multilevel wells as shown in Figure 5.
Vertical groundwater movement will identify whether the site is a
discharge or recharge area.
A landfill constructed in a discharge area likely will be a
zone of saturation site where groundwater flows into the landfill
and is removed by the leachate collection system or an auxiliary
groundwater level control system.
Leachate escaping from a landfill constructed in a discharge zone
will likely be retained in the vicinity of the landfill; but it
may become a source of water pollution if the leachate reaches
the ground surface and flows into a stream or lake.
Recharge areas may also be identified with multilevel monitoring
wells. In these areas the groundwater is moving down and away
from the site. These migration patterns tend to increase the rate
and extent of contaminant transport, thereby intensifying
problems associated with possible leachate migration beneath a
landfill site.
Hydrogeologic studies are relatively expensive to
conduct and should, therefore, be limited to those sites with the
most promising characteristics. A further cost concern involves
obtaining permission to do the testing without actually buying
the property beforehand.
One alternative is to purchase an option to buy, which gives the
purchaser the right to buy the land within a specified period of
time for a specified price. This allows time for testing and
evaluation of the results without commitment to purchasing the
property.
The preliminary feasibility report should contain
all of the pertinent information needed for determining which
site to select for landfill development. The report may select a
preferred site or may leave this decision to the governing board
of the unit of government or other organization which will be
operating the landfill.
Once a site has been selected, a final feasibility report can be
prepared for submittal to the appropriate agencies for approval.
Additional information regarding report preparation will be
provided in subsequent lessons.
1. What are the characteristics of ideal sites for sanitary
landfills?
2. What are the environmental and technical factors to be
considered in evaluation of potential sites for a sanitary
landfill?
3. Summarize the procedure for evaluating potential sites
for sanitary landfilling.
Hahn A Resolving Public lssues and Concerns through Pulicy
Education InformationBulletin #214 Cornell Univesity
Noble G Sanitary Landfill Design Handbook Technomic
Publishing Company. 1976.
O´Hare, M., Bacow, L., and Sanderson, D., Facility
Siting and Public Opposition. VanNostrand and Reinhold, 1983.
Robinson, William D., ed., The Solid Waste Handbook - A Practical
Guide. Wiley - Interscience, 1986.
Wilcomb, M.J. and Hickman, H L, "Sanitary Landfill Design,
Construction and Evaluation " U S. Government Printing
Office, Washington, D.C.
