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OCR for page 32
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.
