2.3 CAUSE AND EFFECT RELATIONSHIPS Figure 2.1 shows the cause and effect relationships for various portions of the SPS system as currently understood. There are a multitude of possible interactions, and only the major pathways have been identified. The Extraction, Processing, and Fabrication of Materials and Equipment activities result in impacts that are primarily conventional in nature; that is, the effects of air pollution generation, water pollution generation, land disturbance, and the like, are not unique to SPS deployment, but are common to all mining, construction, and manufacturing operations. The importance of considering these impacts as part of an SPS assessment comes from the need to evaluate the incremental effects caused by the SPS system requirements. This preliminary assessment will attempt to provide some very rough indications on the extent of the incremental impacts caused by the SPS deployment. The only significant exception to the conventional effects of these activities is the exposure to toxic materials that are unique to the SPS system. Some unusual materials will be involved in the manufacture of the solar arrays, and in the rocket propellants. As the assessment will show, there has been no systematic identification of the toxic materials involved, and a complete impact evaluation cannot be carried out at this time. The Transport of Materials and Equipment activities involve the logistics of moving the SPS supplies between mining sites, construction locations, manufacturing facilities, launch and recovery areas, and ground stations. Again, most of the impacts are conventional in nature, and the issue of interest is the incremental effect. Two unconventional and SPS-specific impacts are, however, significant. One is the exposure to toxic materials and the second is the potential for catastrophic accidents which results from the need to move large quantities of highly flammable and potentially explosive materials (e.g., liquid hydrogen, propellants, etc.). Although materials of this type are currently being transported, the increase in quantity for SPS use and the concentration of movement along selected transport corridors must be carefully assessed. The Ground Station Operation and Maintenance is of concern because of the high intensity, low frequency electromagnetic fields associated with the power distribution system. However low frequency field effects are common to all electrical power systems and are not unique to the SPS.
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