3. The Need For A Safety Factor
Chapter 3
Factor
The Need for a
There are numerous factors that introduce uncertainty and variability
BMP
cost-effectiveness estimates. It is important, therefore, to develop a margin of
safety to ensure that these estimates are reliable indicators of the real-world
reductions that can be expected from money spent on
Exactly what that
safety factor should be is a subjective judgment that we will leave to the
participants of the Phase 2 negotiations. The purpose of this section is to assist
in the development of a safety factor by explicitly defining the elements that
introduce uncertainty in to the preceding analysis.
3.1
Uncertainties in Animal Waste Management Effectiveness Estimates
There are numerous factors that influence the effectiveness of animal waste
practices in reducing nutrient loads to surface waters. One of the most difficult to
quantify is local atmospheric deposition of volatilized ammonia. One of the
primary mechanisms of nitrogen reduction from stored wastes is/volatilization of
ammonia. in anaerobic lagoon liquid, for example, ammonia constitutes 70 to 90
percent of the total nitrogen (Safely et al., 1992). The cost-effectiveness values
presented in this report are based on the assumption that volatilized ammonia
leaves the watershed. However, local deposition of ammonia is possible,
particularly via rainfall. The extent to which this occurs in the Tar-Pamlico basin
is unknown. If deposition is occurring at significant rates, the effectiveness
values presented in this report may overestimate the actual cost-effectiveness of
animal waste practices.
A second consideration is that the effectiveness values presented for land
application are based on the use of proper nutrient management procedures.
However, farmers do not always follow recommended nutrient management
guidelines. Sometimes this is due to circumstances beyond the farmefs control,
such as an unexpected rainfall following land application of wastes. Other times
or lack of knowledge causes operators
economic constraints,
to apply or handle wastes improperly.
Another consideration IS the difficulty in estimating the future effects of incentive
payments. The SCS will provide incentive payments for up to 3 years for various
types of land application methods. The purpose of the incentive payments is to
help make proper land application an intrinsic part of the farmers operation.
However, after the payments cease, there is no way to ensure that the farmer will
continue to land-apply properly. Since we do not know how long a farmer will
continue to land apply properly, our analysis counts the benefits of land
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