The usual example of avoided cost for alternative 4 is the future cost of generating equipment replacements and upgrades at the Lower Snake River dams. The IEAB urged the Corps to consider other possible future costs that would be avoided, such as those of increased Clean Water Act compliance at the dams or the requirements for fish and wildlife programs that might be unnecessary if the dams were breached. We turn now to the benefits of dam breaching. What is most significant about the estimated benefits of the dam breaching alternatives is not their most probable level, but their extreme uncertainty. In addition to the obvious benefits associated with increased tribal, commercial and recreational salmon harvest, there are values associated with non-angling recreation, with tribal wellbeing, and with the intrinsic or existence value of improvements to threatened or endangered salmon populations.
Uncertainty is greatest in the estimates of the existence values.
The IEAB recommended to the Corps that these values be treated separately from other benefits, and that advice is generally followed in the economic appendix. We have followed our own advice here by not including them in the display of benefits in Figure 2. Nearly all of this range is due to the huge range of estimates of non-angling recreation values on a restored natural Lower Snake River. The range of benefits would be even wider if the range of dollar values for existence value had been included. Each of the categories of benefits is discussed below along with IEAB comments.