RES CF01-Tobacco Road Revised Draft Mit Plan Comments (2)

DEPARTMENT OF THE ARMY
WILMINGTON DISTRICT, CORPS OF ENGINEERS
69 DARLINGTON AVENUE
WILMINGTON, NORTH CAROLINA 28403-1343
CESAW-RGM/Isenhour February 3, 2023
MEMORANDUM FOR THE RECORD
SUBJECT: Action ID # SAW-2021-00489, NCIRT Review Comments on the RES Cape
Fear 02 Umbrella Mitigation Bank, Tobacco Road Mitigation Project, Revised Draft
Mitigation Plan
Erin Davis, NCDWR:
1. DWR has reviewed RES' responses to our previous comments and additional
information provided (Appendix C). Overall, DWR is satisfied will RES' responses
to our comments. However, we still have concerns about the proposed Layer
Riffle design. If the IRT determines this is a viable/creditable approach, DWR
requests that a reduced credit ratio or modified/delayed credit release schedule
be considered due to the associated risk of applying this new approach. These
project reaches will essentially be acting as a pilot study for this treatment
design.
Kim Isenhour, USACE:
1. The proposed layered riffles within enhancement reaches for the purpose of
raising the water table is concerning. We question the long-term sustainability of
these structures, particularly if this site has slate -belt stream characteristics. We
could potentially see the utility if it was a lower slope channel with finer sediment.
We discussed this proposed design feature with WRC and EPA and agree that
the science of stream restoration is still evolving and that more research is
needed. We would need to see a series of these applied to another mitigation
project with positive results and stability. It would be helpful to also include
stream power information to fully gain appreciation of how this approach works in
storm flow situations. If these layered riffles were installed, a performance
standard that addresses overbank flows/floodplain connectivity specific to these
reaches and demonstrates the projected uplift would be required, in addition to
the proposed cameras. The biggest concerns with this design are long-term
sustainability and the constraint to aquatic passage, particularly if flow pipes
through the brush layers. We are hesitant to proceed with these layered riffles
included in the engineering plans; however, we appreciate the thought put into
the Risk Summary and would offer that if you elect to install these riffles, the
reaches where they are installed will not receive a credit release until the final
close-out of the project after seven years of monitoring, or until performance
standards have been met.

-z-
2. Long -Term Endowment: I would suggest contacting UP2S to obtain an updated
Monitoring and Legal Defense Fund amount to account for inflation and federal
mileage rate increases. This site also has a lot of crossings, causing easement
fragmentation, which cause de facto subdivisions of the easement, which could
cause complications in the future with multiple ownerships if the larger parcel is
subdivided along those breaks.
3. Please make sure to capture WF, WC, WU and the creation wetlands along TR2
in random veg plots during monitoring.
4. It's not appropriate to count black willows towards vegetative success.
5. It's noted that Murdannia is on -site. This invasive has proven to be very difficult
to treat on other mitigation sites, both in -channel and in wetlands. Please
document all treatment efforts and reach out if you would like to discuss lessons
learned.
Ki m b e r l y T. Digitally signed by KimberlyT. Isenhour
Isenhour Date: 2023.02.03 18:03:08-05'00'
Kim Isenhour
Mitigation Project Manager
Wilmington District Regulatory Division