Lesson 5: Evaluating a Potential Sanitary Landfill Site

Patrick Walsh and Philip O'Leary

This is the fifth lesson in the independent learning correspondence course on municipal solid waste (MSW) landfills. One lesson in this 12-part series will be published in Waste Age magazine each month throughout the year.

If you are interested in taking the course for two continuing education credits (CEUs), send a check (payable to the University of Wisconsin) for $149 to Phil O'Leary, Department of Engineering Professional Development, University of Wisconsin, 432 N. Lake Street, Madison, WI 53706. Phone (608) 262-0493. E-mail: [email protected]. Website: www.wasteage.com.

Course registration can occur at anytime until December 2006. Previous lessons will be sent to you.

Click here to download PDF of Course 5 with figures. (Requires Adobe Acrobat Reader)

Learning Objectives:

The current trend toward larger and larger landfills makes finding or expanding an existing landfill site important. Current designs using geosynthetic liners and other engineering improvements make it physically possible to site landfills anywhere. However, as those who try to site landfills well know, sound technology alone is not enough for proposed sites to gain public and regulatory acceptance.

Today, there's more to landfill siting than technical suitability. Current national land use issues including urban sprawl, farmland preservation and population growth affect landfill placement. Other factors include local public opinion, hauling distance, accessibility, climate and economics.

This lesson provides a procedure for evaluating potential sites and seeking public input.

An ideal sanitary landfill:

Regulatory Criteria and Public Acceptance

The two most important questions to answer when developing procedures to search for a landfill site and actually siting a landfill are whether regulatory agencies will approve the location and whether the public will accept it. Incorrectly predicting how the public and government agencies will react can result in wasted investments in feasibility reports and other technical investigations, as well as lead to potential litigation and other time-consuming and costly delays. So to smooth the process, landfill siters should have a clear understanding of regulatory criteria and public opinion.

The Federal Resource Conservation and Recovery Act of 1976 (RCRA) established general standards for landfill siting including controls for detecting site impacts on water quality, siting in flood plains and effects on endangered species. In the late 1980s, the U.S. Environmental Protection Agency (EPA), Washington, D.C., published new landfill regulations, known as Subtitle D.

According to Subtitle D, landfill development is restricted in areas including wetlands, unstable soils such as Karst terrain or landslides susceptible areas, fault areas, seismic impact zones, and land in the 100 year flood plain, or in proximity to an airport. Except for fault zones, landfills would not be prohibited from these areas, but they would be subject to special siting restrictions and/or performance standards. Location requirements would apply to new municipal solid waste landfills and existing landfill expansions.

Federal regulations also require that new and expanded landfills located within 10,000 feet within any airport runway that is used by jet aircraft, or within 5,000 feet of any airport runway that is used by piston type aircraft, demonstrate that the site does not pose a bird hazard to aircraft. This restriction has stopped some landfill development and should not be ignored.

Most states also regulate solid waste disposal and require site construction and operation approval. These laws may further limit site locations. In Wisconsin, for example, regulations prohibit sites within 300 feet of a navigable stream, 1,000 feet of a navigable lake or pond, wetland areas, flood plains, or 1,000 feet of a state or federal highway or park (unless berms, fencing or landscaping prevent visibility from the road or the park).

Local government zoning or other regulations can affect site acceptability, too. For instance, as comprehensive planning and zoning laws in- crease around the country, landfill development areas may be designated by county or town plans. Siters can attempt to change local zoning, but the effort may be useless if there is significant public opposition.

Beyond knowledge of federal, state and local regulations, landfill developers should get to know and work with officials who administer solid waste programs. These officials share the goal of finding environmentally sound landfill sites and can help interpret and apply existing rules to streamline the search.

Site Search Process

Generally, when siting a new landfill, developers should:

Public Involvement

One of the most important decisions landfill developers need to make is when to publicize the search. Notifying the public about a potential landfill site can create interest, but many developers try to keep their decisions secret until a final choice is made out of fear of stirring up controversy. Some siters also worry that if people know that a piece of land is being investigated, it will drive up the price.

Nevertheless, many now believe that waiting until a final site is chosen — known as a “decide - announce - defend” policy — leads to maximum public opposition. If a potential landfills' neighbors feel that they have no options in a facility siting, this can lead to frustration and litigation, where the public opposes the landfill simply on principle.

The EPA and many others recommend getting the public involved earlier. The search process can be used to educate the public about the difficult choices that must be made and about the degree of effort and expertise that developers apply when making landfill decisions. And this can help to induce the public to choose a site from among the available alternatives.

This approach is not trouble free; it can be time-consuming and difficult. But a well-run public involvement process should increase acceptance for a proposed landfill rather than generate opposition.

Additionally, some public involvement usually will be mandated by federal, state or local regulations. For example, the EPA's RCRA siting process requires a developer notify the public and hold a public hearing at least 30 days prior to applying for a facility construction permit [See “Public Involvement in the RCRA Permitting Process” above].

Identify Project Goals

As part of choosing a site, the community or private company developing the landfill should clearly identify project goals. Each entity will have specific needs to address, but common goals include:

Having clear objectives makes it easier for developers to communicate with citizens and political officials.

Establish Design Basis

Siters also need to gather important facility data. For example, population data and current solid waste generation rates should be used to project the waste quantities the new disposal facility will receive. The analysis should include a projection of future population growth and commercial and industrial development, plus the effect of recycling or resource recovery on available waste.

When more than one landfill will serve an area, developers need to determine whether the new facility can compete economically with alternative sites given haul distances, access to waste, etc.

Based on the analysis, the developers should be able to estimate waste quantity projected to be received at an assumed tip fee. If, after being placed in operation, the planned landfill requires a higher tip fee to remain economically viable, the waste quantity received may be less than originally estimated. A site that receives substantially less waste than originally planned may be uneconomical to operate.

Maps and Potential Sites

After establishing the fill site size required to handle the specified service area for a certain number of years, the physical search for potential sites can begin.

Developers can use informal surveys to extensive mapping studies in their search. Geographic information system (GIS) data at the local level may make the task easier.

A potential site's suitability will be rated for various factors. These studies are most important for publicly owned facilities where each landfill development step probably will be scrutinized.

Entities developing private sites also may 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.

Meeting Land Use Requirements

Potential sites must be in suitable landfill development areas. Many areas have project land-use for 10 to 20 years. In the absence of GIS maps, air photographs can be used to assess current land-use patterns.

Industrial areas may seem suitable for a landfill site because heavy equipment is required and significant traffic is generated. However, the landfill, after it is closed, may not be compatible with industrial operations. If properly designed and operated, a closed landfill could be used as an industrial site, but more often than not, differential settlement within the finished site limits the site''''''''s ability to support buildings.

Most often, completed landfills are used as open space or recreational areas. But areas with endangered plant or animal habitats, virgin timber land, wildlife corridors, unique physical features, and historical and archeological sites should be avoided in locating a landfill. Developing a landfill in one of these areas can be detrimental to the environment, which would outweigh the benefits of a successfully operated landfill.

Using Soil Maps in Siting

Soil maps, which identify soil profile characteristics to depths of 5 feet, prepared by government agencies, provide useful information about potential sites. These maps show soil type plus other key features such as roads, railroad tracks, buildings and surface waters.

Soil also is important in landfill development for three basic reasons:

Ideally, sites should be located in silt and clay soils that 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 available areas have less than optimum conditions for landfill construction, soil may need to be hauled to the site for liner and cover construction. As an alternative, a geomembrane cover and liner can be installed.

Some site identification studies have established separate procedures to rate soil. Developing criteria specifically for a landfill siting study allows local conditions and concerns to be incorporated into the evaluation. Regulatory standards also may be incorporated in the landfill site identification process at this stage. The most efficient approach is to apply the criteria to the soils maps before evaluating other sources of data.

During the preliminary site identification phase, floodplain maps also can be used as resource documents. If no floodplain maps exist, soils maps can roughly delineate areas subject to flooding. The use of soils maps, however, cannot fulfill the need to conduct floodplain analysis during a later phase of the site selection process.

Keep in mind, however, that soil maps are limited in that they only describe areas to depths of 5 feet, so a site that initially is judged to be suitable may be deemed unsuitable based on data collected at deeper levels.

Hydrologic Setting Important

The land's contour and subsurface formations obviously are important for landfill development. Surface features will affect the landfill's layout and drainage characteristics.

Subsurface formations and groundwater conditions will influence design features, such as leachate collection and liner requirements. The formation's geotechnical characteristics will determine its suitability as a construction material.

Maps that show contours, drainage, topography, surficial deposits, geologic formations, bedrock depth and type, and depth to groundwater can be used to further define suitable areas. These maps are available from U.S. Geological Survey (USGS), based in Reston, Va.

When tabulating this type of data, certain assumptions about potential sites may be necessary. They can be confirmed later by conducting soil borings if the potential site is a good candidate.

Tabulating Site Identification Data

Several procedures may be used to collect and tabulate data. The most informal approach is to identify potential sites based on personal knowledge of the area being studied. This approach helps to limit the land area to be considered, but also could mean other suitable areas may be overlooked.

A more thorough identification process is to apply previously described criteria to the entire study area using 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 can be prepared using GIS software or on transparent plastic sheets and place over the base map [See “Base Map and Overlays on page 76].

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.

An alternative to map overlays is land area numerical ratings. In this system, 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.

The numerical data can be manipulated to give greater importance to different factors. Sites with the best numerical score are designed 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 most suitable.

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.

Additionally, data about existing land use, surrounding land development, available utilities, highway access, political jurisdiction and land cost is tabulated.

Subsurface investigations should be conducted at 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 site's hydrogeology.

As the boring is being conducted, a soils or geologic specialist will collect testing samples. Normally, soil samples are tested for grain size distribution and moisture content, and are classified by soil type.

Soil that may be later used for liners and landfill covers also will be tested for permeability, Atterburg limits, moisture content and moisture density relationship. This data is used to prepare a boring log.

Borings should extend at least to a depth of 20 feet below the expected landfill's base elevation. A portion of the borings should terminate below the water table if it is greater than 20 feet below the anticipated site base. 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. 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 [See “Groundwater Contour Map” on page 77].

In addition to horizontal movement and potential contaminants, groundwater may move vertically within the subsurface formation under the site. Vertical movement can be detected by installing multilevel wells [See “Groundwater Gradients and Flow Lines” on page 80]. Vertical groundwater movement will identify whether the site is a discharge or recharge area.

Recharge and discharge areas will be identified with multilevel monitoring wells. In recharge areas, groundwater moves down and away from the site. These migration patterns tend to increase the rate and extent of contaminant transport, thereby intensifying problems from possible leachate migration beneath a landfill.

Hydrogeologic studies are relatively expensive to conduct and should be limited to sites with the most promising characteristics. A further cost concern involves obtaining permission to test prior to buying the property.

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 provides time to test and evaluate the results without a commitment to purchase the property.

The preliminary feasibility report should contain all of the pertinent information needed to determine which site to select. The report may select a preferred site or may leave this decision to the government's governing board or other group that will be operating the landfill.

Once a site has been selected, a final feasibility report can be prepared for submittal to the appropriate approval agencies. Additional information regarding report preparation will be provided in subsequent lessons.

Phil O'Leary and Patrick Walsh are solid waste specialists at the University of Wisconsin-Madison. Lesson 6 will describe bioreactor landfill design and operation. Visit www.wasteage.com for information.