CEPIS/OPS/OMS

A Evaluating a Potential Sanitary
Potential Sanitary Landfill Site

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;

By Patrick Walch & Philip O'Leary

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:

  1. Is easily accessible iii any weather to vehicles expected during the operation of the landfill:-
  2. Has safeguards against potential surface and groundwater pollution;
  3. Has safeguards against uncontrolled gas movement originating from the disposed solid waste;
  4. Has an adequate quantity of earth cover material that is easily handled and compacted:
  5. Will be located in an area where the landfill's operation will not detrimentally impact environmentally sensitive resources;
  6. Will be large enough to accommodate the community wastes for a reasonable time interval
  7. Will be the most economic site available commensurate with the ultimate requirements for solid waste disposal.

Regulations and site selection

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.


Public involvement in the process

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.


Site search

The process for siting of a new landfill can be divided Into the following steps:

  1. Establish goals and gather political support.
  2. ldentify facility design basis and need.
  3. ldentify potential sites within the region.
  4. Select and evaluate in detail the most desirable sites.
  5. Select best site for development.
  6. Obtain regulatory approval of site.

Identify goals

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.


Establish design basis

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.


Maps and potential sites

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.


Fulfilling land use goals

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.


Use of soil maps in siting

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.


Ideal soil for a 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.


Hydrologic setting important

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.


Tabulating site identification data

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.


Evaluating suitable sites

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.


Soil borings

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.


Hydroologic studies

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.


Lesson Assignments

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.


References

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.