A standard question nongeologists ask upon encountering a geologist in the field is, "Finding any gold?" Many people still think of geologists as "forty-niners"--eccentric" loners on a quest for the mother lode. This image of geologists is beginning to fade, however, as geoscientists emerge across the nation as primary participants in determining how and where we will dispose of or otherwise process the burgeoning volumes of waste generated by our society. We Americans constitute just 5 percent of the world population but generate 40 percent of the world's waste in our consumption of 50 percent of the world's annual production of raw materials. Although waste reduction and recycling efforts in recent years have begun to have a significant impact, Americans continue to generate large amounts of municipal solid waste--209 million tons in 1994, or 4.4 pounds per person per day.
Environmental awareness has not substantially stemmed the escalating rate of waste production, but it has certainly sensitized us to the dangers of improperly disposed waste. In this regard, environmental awareness has been so "successful" that the siting of any solid-waste facility generates tremendous organized public resistance. Such public turmoil often finds geologists inextricably caught up in the fray, as they are usually the ones who have the unenviable task of explaining to an angry group of citizens the geologic justification for the placement of a landfill in their community as opposed to a site on the opposite side of the county. It becomes obvious that the geologist is more than a quaint prospector, and now assumes the role of diplomat, negotiator, and environmental-regulations expert in addition to the role of geologist.
THE WASTE STREAM AND THE NEED FOR
COMPREHENSIVE WASTE MANAGEMENT
In Ohio, the combined effect of overdependence on landfills, escalating importation of out-of-state waste, and the lack of comprehensive solid-waste management planning led to a landfill capacity crisis in the late 1980's. By 1988, 33 of the state's 88 counties had less than five years of remaining landfill capacity; 28 counties had no solid-waste facilities. Clearly, Ohio had to develop and implement a comprehensive solid-waste-management program immediately if an environmental crisis was to be avoided. Ohio certainly would not want to be the focus of a national solid-waste embarrassment such as the one in which a barge carrying garbage from Islip, New York, sailed the length of the east coast and portions of the Caribbean in search of a facility that would receive and dispose of its cargo--only to be rejected at every port and forced to return to New York.
EFFORTS IN OHIO
In 1988, Ohio passed legislation initiating a comprehensive solid-waste planning process at the state and local level. A statewide goal to decrease Ohio's waste stream by 25 percent (on a per capita basis) through recycling and waste reduction by mid-1994 was set by the legislation. Fifty-two single-county and multicolor solid-waste-management districts were formed under the new law and are operating under state-approved plans to manage and reduce their solid-waste streams. Each plan provides disposal capacity for at least a 10-year period, and lays out how the state recycling goal will be achieved.
Local solid-waste-management districts provide recycling education and awareness programs and technical assistance to local communities and private businesses. Thanks to their efforts, the 1994 goal was surpassed: the statewide rate of recycling and waste reduction was 34 percent in 1994, although local rates varied widely. In 1995, a new statewide goal to reduce the waste stream by 50 percent (on a per capita basis) was set for the year 2000. The districts are striving to achieve this new goal, in part through the assistance of the Ohio Department of Natural Resources, Division of Recycling and Litter Prevention, which is providing technical and financial assistance to local recycling programs, and is spearheading efforts to improve markets for recycled products in Ohio.
In addition to their recycling efforts, each solid-waste district must estimate how much waste will be generated by that district during the next 10 or more years and develop a plan to manage the incoming, nonrecycled waste through demonstrated disposal capacity. It is not required that every county have a landfill, and the nationwide trend has been toward newer regional landfills that draw waste from a much larger area than a single county. District plans must include a strategy for siting any in-district solid-waste disposal facilities that may be required to manage its waste. Through this process, districts may determine which areas within their borders are the most and least suitable for locating a landfill, based upon both hydrogeological and socio-economic factors. Considerations include hauling costs and distances, proximity to sensitive natural areas and water supplies, local zoning, and noise and traffic levels. Local siting strategies commonly include a mediation process for resolving disputes and controversies that may arise.
GEOLOGIC AND HYDROLOGIC CONSIDERATIONS
IN SOLID-WASTE MANAGEMENT
Public concern relative to landfills commonly centers on legitimate questions about windblown trash, bird and vermin infestations, odor, dust, noise, aesthetics, traffic, and property devaluation. Ground-water contamination, however, is nearly always the foremost concern. Public acceptance, or at least tolerance, of a landfill is absolutely dependent on a competent demonstration that ground-water contamination will not occur or, if it does, that it will be promptly detected and completely corrected. Such a demonstration is possible only through an excellent design, construction, and operation plan that is in harmony with the geology and hydrology of the landfill site.
Generally speaking, landfills must be sited in areas where the buried waste can be effectively isolated from the ground-water system. Clay-rich materials, either on site or nearby, are required to provide daily and final cover over the waste and to prevent infiltration of rainwater into a landfill. Such materials also are required for construction of a recompacted soil or clay liner under a landfill to restrict the flow of ground water into the buried waste or the flow of leachate (a putrescent and toxic liquid formed by the dissolution of buried waste in water) away from the landfill. A synthetic liner (typically 60-mil high-density polyethylene) is placed above the recompacted soil liner to further assure isolation of the buried waste.
Effective isolation of buried waste also is dependent on the structural and functional integrity of a landfill. Ohio EPA regulations require that landfills be located in areas that are geologically stable. Areas prone to mass movement (for example, landslides), differential compaction of soils, and subsidence (for example, karstic terrain) must be stabilized in order to be approved as landfill sites. Similarly, landfills cannot be sited over underground mines unless it can be demonstrated that there is no significant probability of surface subsidence, nor can they be sited within 200 feet of a geologic fault that has been active in the last 10,000 years. Sandstone and carbonate-rock (limestone and dolomite) quarries and sand and gravel pits are not acceptable as disposal sites because of the high permeability (rate at which a fluid will flow through a porous body) of such materials.
To further assure the hydrologic isolation of a landfill, Ohio EPA regulations prohibit the burial of waste within 1,000 feet of a pre-existing water well or developed spring unless (1) the landfill operator controls such water supplies, or (2) the supplies are at least 500 feet hydrologically upgradient from the buried waste and the water is used for nondrinking purposes only. In addition, landfills cannot be located above federally designated solesource aquifers or above unconsolidated (sand and/or gravel) aquifers having the potential to provide 100 or more gallons of water per minute to existing or future wells within 1,000 feet of the buried waste. Waste disposal on regulatory floodplains and areas within 200 feet of streams, lakes, or wetlands is prohibited. Landfills cannot be sited so near to public well fields that contaminants escaping from the landfill in ground water could be expected to intersect the wellhead(s) within five years. The bottom of the recompacted soil liner underlying a landfill and the uppermost aquifer must be separated by at least 15 feet of slowly permeable geologic materials. Sociological factors also are reflected in Ohio EPA landfill regulations. For example, waste cannot be buried within 10,000 feet of an airport serving jet-turbine aircraft or 5,000 feet of an airport serving only piston-engine aircraft. Landfills cannot be sited in state or federal parks or recreation areas. Solid waste also cannot be buried within 300 feet of a property line or within 1,000 feet of a residence.
In the site-selection process of locating a landfill, regulatory criteria such as those previously described are useful in the preliminary screening or reconnaissance phase of site selection. All areas which cannot meet these criteria are eliminated automatically from further consideration. Areas not excluded during this process become candidates for detailed geologic and hydrologic assessment.
Detailed site characterizations are time consuming and costly to perform but are absolutely essential in the preparation of an application for a permit to install and operate a landfill. Site characterizations typically involve the drilling of numerous test borings from which an accurate, three-dimensional geologic framework of the site can be established. Material samples from the borings are analyzed for grainsize distribution, mineralogy, weathering, fracturing (jointing), porosity, permeability, engineering strength, and various other physical/chemical parameters. Ground-water wells are installed to identify waterbearing units, the piezometric surface (water table) for water-bearing units, and depth of saturation, as well as to evaluate the interconnectedness of water-bearing units. Such information, together with geologic information, is used to develop a hydrologic framework for the site. Geology and hydrology are key components in the successful design and operation of a landfill and must be understood and accounted for if serious environmental problems are to be avoided. Although the effort and expense required to perform a competent geologic and hydrologic assessment are great, they are small in comparison to the effort and expense required to mitigate environmental damage caused by an improperly designed and/or operated landfill.
Cross section of a landfill. Diagram courtesy of
Tony Furgiuele, Waste Management of North America, Inc.
In Ohio, the western half and northeastern quarter of the state have been glaciated. Consequently, about 70 percent of Ohio is covered by a blanket of unconsolidated glacial and/or glacially derived sediments. Glaciated uplands mantled with thick deposits of clay-rich till and/or lacustrine (lake) clays generally are candidates for consideration as potential solid-waste disposal sites, if other siting criteria can be met. A fairly common former practice of using abandoned sand and gravel pits for burial of solid waste is no longer allowed because of the extreme risk of ground-water contamination. In unglaciated southeastern Ohio, upland areas underlain by thick sequences of Pennsylvanian- and Permian-age shale commonly are selected as sites for waste disposal. Underclays (clay units directly underlying coal seams) also are potentially good materials upon which to site a landfill; thus, abandoned coal strip mines in eastern Ohio commonly are used as landfill sites. All terrain in Ohio, regardless of its geologic age or origin, can be highly variable both vertically and horizontally in regard to physical, chemical, and hydrologic properties that are important in regard to landfills. Accordingly, all sites, no matter how geologically appropriate they may seem at first glance, must be thoroughly evaluated prior to drawing any conclusions about suitability for burial of solid waste.
The files of the Division of Geological Survey contain thousands of records and maps that can provide useful, if not essential, information to solid-waste-management districts in the development and updating of waste-management plans. This information is very technical in nature, however, and may not be easily understood by persons who are not familiar with geologic principles and terminology. Division of Geological Survey geologists can assist in interpretations.
Although management of our nation's waste remains one of the most controversial and divisive of environmental and sociological issues facing American communities today, the conflict has not been entirely undesirable. Vast numbers of people, who once never thought for a moment about where their trash went after it was collected, are becoming actively involved in waste-management decisions affecting their communities. And geologists, still stereotypically viewed by many as thick-spectacled, humorless professors in herringbone-tweed jackets or lonely, grizzled prospectors, are now emerging more and more as scientists with a major and essential role to play in the preservation of the environmental integrity of the nation.
The author gratefully acknowledges Lindsay Taliaferro III of the Ohio EPA, Division of Drinking and Ground Waters, and Carolyn Watkins and Mike McCullough of the Ohio EPA, Division of Solid and Infectious Waste Management for supplying resource materials and for reviewing and contributing to the text.