Using the Credit/Debit Method for Temporary Impacts
The information on this page helps to clarify how to use the Credit/Debit
Method to calculate the debits for temporary impacts. If all the functions at a
site are re-established to their previous levels, compensatory mitigation would
only be needed for the temporal loss of functions and for the potential risk the
re-establishment would fail. (Temporary impacts are discussed in Section 3.2 of
the Credit/Debit Method.)
Will temporary impacts (eventually) be restored on site? If
the answer is yes, then use the following process:
- Calculate the impacts (debits) using the Credit/Debit Method
(C/D Method) and use the temporal loss factor that matches the Cowardin Class being impacted (e.g., PEM, PSS, PFO)
- If the long-term temporary impact is between
1-2 years, then the temporal loss factor will be
a minimum of 1.5 or a maximum of 3.5 (use the
concurrent temporal loss factor for the subject
Cowardin Class from the Appendix table in
the C/D Method.). Note: For impacts to PEM
wetlands that will be restored on site within 1
year, it has been agency policy (Corps and
Ecology) that little to no compensation is
required, depending on the case specific
factors. However, if the wetland contains a
native emergent plant community, compensation
will likely be required.
- If the long-term temporary impact is over 2
years then use the delayed temporal loss factor for
the appropriate Cowardin Class (a minimum of 3
and a maximum of 7)
- Using the C/D method, calculate the credits proposed to be
generated by the on-site restoration activities, inclusive of
the risk factor (use the risk factor Appendix table in the
C/D Method). For on-site restoration this
factor would typically be 0.67 for PSS and PFO and 0.5 for PEM.
Note: The risk factor may need to be adjusted depending on the
project and the extent of the temporary impacts.
- It is possible that the proposed
re-establishment could increase the functioning
of the site if re-establishment involves
replacing an invasive-plant dominated community
with native plants.
- The number of credits the applicant needs to compensate for
the temporary long-term impacts from the project is the
difference between number 1 and 2 above.
If the long-term temporary impacts will NOT be restored on-site, then the
Use the C/D method as if this was a permanent impact. For projects buying ILF
credits, the temporal loss factor would be a minimum of 3 depending on the
Cowardin class being impacted.
Questions or Comments?
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