• impact on resources (e.g., use of renewable and nonrenewable resources, pollution of resources);

• direct impact on nature and landscape, such as through undesirable change in landscape;

• air pollution and its contribution to climate change, smog, acid deposition, odors, and deterioration of the ozone layer;

• soil pollution, such as solid wastes added to soil, through eutrophication, added toxins, and contributions to groundwater pollution;

• surface water impacts, including biological or chemical discharges with oxygen demand, toxic discharges, surface water warming, and contribution to eutrophication;

• noise;

• electromagnetic radiation or fields; and

• ionizing radiation.

In many environmental lifecycle assessment studies, environmental impact estimates are limited to only a few critical categories of impacts, such as emissions of greenhouse gases and conventional pollutants.

Assessing system interdependencies over the life cycle of underground infrastructure is also an important and challenging part of assessing risk. A variety of analytic tools exist to aid in risk assessment of individual infrastructure systems and interactions. These include Bayesian networks, Monte Carlo simulation, and decision trees (Rinaldi et al., 2001; Haimes, 2004; Weber et al., 2012). Applying such tools may inform decision making by reducing some of the high levels of uncertainty associated with different kinds of risk, especially when dealing with interactions of complex systems.

In this chapter, the committee assembles existing knowledge of the impacts of underground development, recognizing there are numerous knowledge gaps, especially because past studies generally took a narrower view of benefits and costs than is required for a lifecycle sustainability perspective. There is also considerable variation and uncertainty in the performance of underground development, especially with regard to extreme events such as earthquakes or flooding. Moreover, the general advantages and disadvantages for underground facilities described in Chapter 3 necessitate specific evaluations for each type of use and site circumstances.

LIFECYCLE ECONOMIC BENEFITS AND COSTS

Increasing population, consumption, density, globalization, communication, and other trends suggest an increasing complexity for human society (Boyle et al., 2010). Implementation of technological advancements can have both positive and negative repercussions. It is important that processes to deliver sustainable



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