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Executive Summary of Workshop Report There is a necessity for multimedia and multidisciplinary assessments of waste disposal practices. The scientific, technological, political, and economic information needed to make an optimal choice among land, sea, and air sites is today generally available or attainable. Current analytical methods are embryonic, and with more sophis- ticated developments, additional information needs will become evident. Even after an optimal choice is made, however, constraints on policy implementation remain. They include (1) the statutory framework, (2) public administration processes, (3) public attitudes, (4) economic forces, and (5) information limits. The principal objective of the decision-making process is to protect and enhance social welfare, a commitment that encompasses public health, environmental protection, and direct costs. The steps in the multimedia selection process are (1) the identification of various air, land, and sea options and the subsequent selection of feasible alternatives; (2) an assessment involving the selected alternatives; and (3) the choice of the option. Currently, each of these steps toward reaching an option is poorly defined by the waste-management community. Better statutory and regulatory definitions of the criteria for comparing options are needed. In this report, the information bases for the options were drawn from the natural and social sciences and from two examples of existing problems, viz., sewage sludge and industrial waste disposal. Disposal options for the entire range of industrial wastes were not examined, but site and waste specificities of all waste disposal prob- lems were recognized. In addition, there is throughout the report an awareness that relevant information is
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often uncertain, controversial, or even lacking to such an extent that the selection process is obfuscated. Three factors in the evaluation process are closely linked: waste properties, specific site characteristics, and design of the facility. Information required for an assessment can be costly, as, for example, in the case of hydrologic data; the cost of obtaining information must always be balanced against potential benefits of reducing uncertainties. Criteria for the land disposal option were evaluated. The prevention of~contamination of foodstuffs and of underground and surface waters was the primary focus. The most important long-term control on water movement on land is evapotranspiration, which includes evaporation from the soil surface and uptake and release of water by vegetation. Some assumptions in predicting the fate of wastes in groundwaters are questionable, especially those concerning homogeneous isotropic aquifers and average annual or seasonal flow rates for a given source. In future modeling of terrestrial systems, more consider- ation should be given to episodic and extreme events like earthquakes and to nonuniform properties of the disposal site. The structural geology and stratigraphy of intended sites for disposal on land need to be evaluated in terms of such features as synclines, anticlines, faults, bedding planes, and burial stream valleys, which may either col- lect or divert water or waste and force it along pathways that cannot be predicted by simple analysis of pressure gradients. Predictions of waste behavior in the oceans that will allow the estimation of impacts on public health, ecosystems, and aesthetic factors involve prediction of spatial and temporal concentrations of the substances and of the oceanic constituents that interact with the wastes. The modeling techniques respond to the site specificity of the wastes, of the system, and of the receiving waters. Existing capabilities for predictive modeling make pos- sible first approximations of the fluxes and concentra- tions so that potential impacts can be estimated. The predictive framework generally can be used for any combination of characteristics of waste, site, and disposal system design. The framework links predictions of concentrations of contaminants to the proposed disposal system through analyses of the physical, chemical, and biological processes that operate in the proposed disposal area.
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6 The information needed for making predictions was identified in this report through the example of the proposed disposal of sewage sludge to the Pacific Ocean off Orange County, California. The substances of concern in the wastes are heavy metals, halogenated hydrocarbons, and organic substances. Predictive models have been formulated for estimating potential impact. In the report, possible biological impacts on land, freshwater, and marine biospheres are considered simul- taneously with focuses on ecosystem integrity and public health. Overriding concerns are threats to human health, possible species extinction, and alteration of the community structure of affected species. The last two can occur through the action of a toxic substance or through the destruction of habitat. The assessment of biological impact can best be made through an understanding of how particular biotic com- munities respond to change. This understanding is already available in the case of some communities and can be developed for others. There is no simple index that identifies irremediable damage to populations, communities, or ecosystems. The threats to public health involve the return to human habitats of undesirable concentrations of toxic substances or pathogens associated with the wastes. Sites of greatest concern are estuaries, groundwaters, and streams and pastoral and agricultural lands. The epidemiological information assessment of potential health effects related to disposal of sludge on land or in the sea must consider the potential transport route for pathogens and toxicants back to society. Two examples of multimedia assessments for evaluating disposal options were developed and presented: (1) municipal sewage sludge and (2) industrial acid wastes. The industrial example involved the disposition of acid iron wastes from titanium dioxide production. After the initial screening process was completed, two possible alternatives evolved: (a) ocean disposal and acid neutralization of the wastes using limestone followed by a disposal of the iron sludge to land and (b) the effluents to the stream. The types of data needed to assess these options were drawn from previous experiences of industry, those involving the 106-Mile Ocean Waste Disposal Site and the New York Bight Acid Waste Disposal Site. Environmental consideration of potential disposal sites required information about impacts on human health, property, and ecosystems, as well as social welfare,
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which involved aesthetics, recreation, noise, and odors. Institutional considerations associated with each possible option involved community attitudes, services, economy, and safety. A matrix approach was used in evaluating the two alternatives in the titanium dioxide disposal. Environ- mental considerations decidedly favored ocean discharge, but institutional considerations were less biased toward that option. Cost analysis favored marine disposal. Sewage sludge disposal site options were evaluated. The two primary factors governing the analysis, i.e., the composition of the sludge and the geography of the area, generally reduce the alternatives to a small number. The evaluation process involved public perceptions, regulatory considerations, available technology, environmental risks, and cost factors. Existing regulations or agency actions may bias the final decision toward an environmentally or economically unsound practice. The available or obtainable information permits select- ing a sewage sludge disposal option based on technically supported data from the different media. However, current studies on disposal techniques should be reviewed periodi- cally, especially in cases involving new construction or replacement of existing facilities. System reliability is an important component of technological evaluation, and it strongly influences the economics of sludge disposal.