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32 A Guide for Assessing Community Emergency Response Needs and Capabilities for Hazardous Materials Releases Table 15. Estimated per-acre values. Structure Environment Area Type Residential Commercial Industrial Land Use Farm Land Wetland Rural $ 150,000 $ 1.2 million $ 2.4 million Fallow $ 200 $ 50,000 Suburban $ 1.2 million $ 12 million $ 24 million Low-value crop $ 1,000 $ 100,000 Urban $ 8 million $ 50 million $ 80 million High-value crop $ 400,000 $ 400,000 For land and aquatic contamination, impacts are a concern if the released material kills plants and trees, or forms a toxic particulate that is deposited on the ground. Preventing human exposure by confiscating crops or decontaminating land or buildings would result in the greatest costs. It would be very conservative to assume that the same area used for estimating population impacts experienced some damage from the release event. The extent of land impacts is also sensitive to the type of hazard. Ammonia will do a lot of damage to a wetland because of its aquatic toxicity, but it is a beneficial fertilizer on farmland. To estimate the potentially affected area, the hazard distance from the NRHM Routing Guidelines (2007) could be used to determine the extent of the potentially affected zone and, within that zone, to estimate the fraction of the area where environmental damage could occur. Table 15 shows representative values for different types of land use. The values shown were developed initially for a security-related assessment for another project, to estimate economic losses on a per-acre basis when the structures or habitat are essentially destroyed. These are place- holders, and you could develop your own set of land-use values for your region. Where structures would not be entirely destroyed, it might be appropriate to use 10 percent of the replacement value. This would represent replacement of windows and repair of minor structural damage. Similarly, a reasonable estimate for land and wetland contamination might also be 10 percent. Depending on the incident release type and the size of the potential incident, you may wish to adjust the percentage to a value other than 10 percent. Step 13 Use the per-acre damage estimates in Table 15 or a geographic information system with environmental data layers to determine the potential environmental consequences for each scenario. If the risk assessment tool is used, scenarios judged to present minimal risk to structures or the environment can be shown as having a zero or low impact. Selecting the Consequence Value Again, the mitigating effects of emergency response coverage are not considered when determining these potential consequences. Comparing the potential population exposure and the environmental costs measured in economic terms to the values in Table 13 provides the appropriate consequence value to use. Remember to take the higher of the population and environmental values. Step 14 For each scenario: (1) determine the consequence value in Table 13 for the potential population impacts determined in Step 11, (2) determine the consequence value in Table 13 for the potential environmental impacts determined in Step 13, and (3) record the larger value as the consequences for the scenario. If the assessment tool is being used, this step is performed automatically. An example of the calculation sequence that begins with Step 10 and concludes with Step 14 is shown in Appendix C.