Draft Mit Plan Comment Memo_WLS Swiftie Mitigation Bank_SAW-2019-00631

DEPARTMENT OF THE ARMY
WILMINGTON DISTRICT, CORPS OF ENGINEERS
69 DARLINGTON AVENUE
WILMINGTON, NORTH CAROLINA 28403-1343

January 12, 2024

CESAW-RGM/Tugwell

MEMORANDUM FOR RECORD

SUBJECT: WLS Swiftie Mitigation Bank - NCIRT Comments during 30-day Mitigation
Plan Review, Edgecombe County, NC

PURPOSE: The comments listed below were received from the NCIRT during the 30-
day comment period in accordance with Section 332.8(d)(7) of the 2008 Mitigation Rule.

USACE AID#: SAW-2019-00631 30-Day Comment Deadline: November 08, 2023
DWR #: 20230026 v1

Maria Polizzi, NC DWR:
1. It appears that a fully landlocked piece of property will be created when this
conservation easement directly abuts the Swift Creek Mitigation Bank. Do you
foresee any issues with this in terms of access or future land use?
2. Thank you for including the Keymap on your plan sheets. This makes it much
easier to review. I also like the colors and symbology.
3. I did not receive a hardcopy of this submittal. In the future, all draft mitigation plans
must be submitted in hardcopy (to DWR and USACE) and on Laserfiche to DWR.
4. DWR likes the idea of a constructed brushy riffle but has not seen this very much.
Has WLS used these with success in the past? How do they compare to rocky
riffles on stability and longevity?
5. Please note that these comments are only regarding the Stream and Wetland
portion of this project. Katie Merritt (DWR) will be reviewing the Appendix I-Buffer
Mitigation and Nutrient Offset Plan separately. Additionally, all project components
(stream/wetland and buffer/nutrient) must be constructed simultaneously. The
approval of one plan before the other does not allow for separate construction
timelines.
6. The drainage area for S100 is quite small (32 acres) and could prove challenging
for headwater restoration.
7. Thank you for including pre-restoration groundwater gauges.
8. In general it would be helpful to have aerial imagery from before 1994, if possible.
9. Please provide additional justification as to why a 7.5:1 ratio for stream and
wetland preservation is appropriate. 10:1 is standard for preservation areas.
Although the area is large and high quality, it seems that the risk/threat to the area
is low (since 1994 the majority of the wetland area has been forested and out of
ag production, most likely due to wet conditions. No significant development
pressure). Additionally, some existing ditches will remain in the preservation area.
10. Section 3.6.7: Please provide more detail about where future trails may be located.
The plan says they will be outside of the “creditable areas”. Does that include
stream buffers associated with stream credits?
11. 100 ft. buffers are expected for stream preservation reaches and therefore buffer
mitigation credit should not be generated for more than 50 ft. of this overlapping
area.
12. Please show vegetation plots for the following categories: shared veg plots
(stream/wetland and buffer/nutrient), DWR only (buffer/nutrient), and
stream/wetland only plots. These can be for both fixed and random plots.
13. Section 6.1: The plan states that “proposed floodplains will be constructed such
that they are over-excavated to accommodate replacement of topsoil”. Please
confirm that there is enough topsoil to be removed prior to over excavating. Often
there is minimal topsoil on agricultural lands.
14. Has WLS considered creating multiple interconnected flow paths for the headwater
stream restoration sections? They are being restored as Rosgen ‘DA’ which is a
multi-thread channel type. DWR is concerned that other flow paths may not form,
if a single pilot channel is constructed, especially if it follows the valley bottom.
DWR also cautions that installing in-stream structures often has the effect of
locking a stream in place, which is opposite of the goal in the case of headwater
restoration.
15. It is unclear where the break between S200 R1, R2 and R3 are located. I do not
see this marked on any of the figures, and therefore am confused about where
headwater restoration is being proposed. Based on Section 6.3.1, S200 R1 will be
headwater, R2 will flow through an existing channel, and then R3 will return to
headwater restoration. However, in Section 8.2 it sounds like all of S200 will be
assigned headwater performance standards. Please confirm and update labeling
on maps.
16. Please note that credit is valley length for headwater systems and no wetland
credit can be generated with 100 ft of where the stream is expected to develop.
17. DWR recommends the inclusion of dimension-based performance criteria,
typically an entrenchment ratio of >2.2 and a BHR of 1.0-1.2.

Kathy Matthews, USFWS:
1. Instead of referring to the Service's letter dated January 20, 2023, the measures
should be incorporated into appropriate areas in Section 6.7 of the mitigation
plan, and more importantly, into the Design Plan Sheets (Appendix A). I also
recommend that the Corps include implementation of these measures as a
condition of the permit:
 A double row of silt fence, to ensure that erosion is captured effectively.
 Silt fence and other erosion control devices should not include outlets that
discharge closer than 50 feet to the top of bank of any stream.
 Silt fence outlets for each row of silt fence should be offset to provide
additional retention of water and sediment in the outer row.
 Conduct twice-weekly inspections of all erosion and sedimentation controls.
 In addition to twice-weekly inspections, inspect also within 24-hours of rain
events (including a 1-inch total rain event or an event where rainfall rates are
0.3 inch/hour or greater).
 Inspect all of the erosion and sedimentation controls to ensure the integrity of
the devices.
 Maintain all controls as necessary to ensure proper installation and function.
 Repair and replace sections of controls as needed to minimize the potential
for failure.
 Revegetate with native species as soon as possible.
 Any spills of motor oil, hydraulic fluid, coolant, or similar fluids into the riparian
wetlands or floodplain must be reported to the Corps and Service
immediately.
 Educate the construction crew about the presence of sensitive species by
providing information or installing signs on the silt fence.
* Please Note that we intend to include the above conditions in the Nationwide Permit
Verification for this project. Please contact us if you foresee any issues with being able
to comply with these conditions prior to submittal of the Final Plan/permit application.

Erin Davis, USACE:
1. General Comment – Please QAQC documents prior to submittal. Several
formatting and grammatical errors were found (e.g., duplicate sentences in multiple
sections).
2. Section 2, Page 7 – If stream segments connect between the PRM site and Bank,
how do they occupy distinct drainages that are not hydrologically reliant on each
other?
3. Page 10, Table 2 – Throughout the plan the reach labelling is inconsistent, which
made this review difficult. Table 2 identifies upper/lower, Tables 4 and 5 only list
tributary names, Section 3.4 text uses upper/lower, Table 8 lists the same reach
name for multiple mitigation types and ratios (which is not acceptable), Tables 11
and 14 as well as Section 6 narrative uses reach R1 – R4 labels, Sections 8 and
9 do not specify reaches, and Figures do not show any reach callouts. Clear and
consistent reach labelling needs to be provided in order for proposed stream
approaches and ratios to be properly evaluated.
4. Page 19, Section 3.5.3 – Please note that the LSS soils investigation and mapping
was limited to a portion of the project (approximately 45 acres closest to Highway
33).
5. Section 3.6.1, Page 20 – Any segment of the Bank easement boundary proposed
to be contiguous with the PRM site needs to be clearly marked. Will the boundary
signs be different for the two sites?
6. Page 21, Section 3.6.7 – The description of potential long-term management of
the property and Bank raises some questions and concerns. Does TRLC have a
prescribed fire plan? Do they have experience performing burn management near
protected resources? More detail needs to be provide, especially with regard to
proposed single-track trails, which we assume are specifically for mountain bike
access and may represent a larger potential threat to the resources provided at
the site. Proposed trails within the bank site must be shown on project figures and
design sheets. Please note that installing trails may affect credit ratios. Installation
of boardwalks or any other structures, including for blue trail access, within the
bank site are not permissible without IRT approval. If TRLC as the long-term
steward plans to actively use the site, another third-party entity may need to be
designated as the easement holder in order to provide independent monitoring and
enforcement of the easement agreement. Additional information is needed on
proposed long-term management, and a follow-up meeting may be helpful.
7. Page 22, Section 3.7.3 –
a. This section doesn’t mention the two existing road culverts within the site
along S500. During the IRT site walk and in the Final Prospectus, these
structures were proposed to be removed. However, Figure 9 identifies as
both culverts to remain. Please clarify. If these structures and associated
roads are to remain, the preservation credit ratio may need to be revisited.
Also, the Meeting Minutes note an existing culvert at the top of S300, but
this structure isn’t mapped or discussed in the plan.
b. Figure 9 does not appear to callout ditches to be plugged. On Figure 9,
please also differentiate ditches to remain open or be partially filled to allow
positive drainage.
c. As noted in the IRT Meeting Minutes, a lateral drainage effect analysis was
requested during the site walk. This request was restated in the Bank’s
Initial Evaluation Letter as a comment to be addressed in the draft mitigation
plan. This information needs the be provided for all ditches proposed to
remain open in the vicinity of wetland credit areas (within or immediately
adjacent to the project). Please run the analysis based on the proposed
wetland hydroperiod performance standard not the minimum 14-day
hydroperiod criteria.
8. Pages 22-23, Section 4 & Table 6 – This section appears to be a standard stream
project insert. There is no discussion of the functional uplift potential of headwater
valley or wetland resources, which are major components of this project. Please
provide a more project-specific discussion of proposed functional uplift potential.
9. Page 23, Section 4.1.1 – Please clarify that the physiochemical and biological
categories are not proposed be assessed as part of this project.
10. Page 28, Section 6.1 – Where is Priority II restoration proposed and for what total
length of stream? Also, please confirm that no Priority II/III is proposed for
headwater valley restoration.
11. Page 29, Section 6.2 – Excavating a broader floodplain to create a headwater
valley is typically not appropriate for this mitigation credit type. Please provide
information on the average and max dimensions of the proposed excavation. The
suitability of site conditions to provide potential stream verse wetland credit in
areas proposed for excavation may need to be revaluated. Also, this section
discusses the use of in-stream structures. Is a channel proposed within the
headwater valley?
12. Page 30, Section 6.3.1 – Please confirm that S100-R1 is proposed as headwater
valley and S100-R2 is proposed as a single stem stream restoration. Should there
be a S100-R3 referenced for the proposed preservation segment? Please clarify
whether the 200-ft riparian buffer restoration mentioned is tied to proposed stream
credit or state buffer credit.
13. Pages 31, S200-R1 – Is S200-R1 similar to S100-R2 as noted, or S100-R1? How
and where will toe-wood be used within the headwater valley?
14. Page 31, S200-R2 – This reach was proposed as Enhancement in the Final
Prospectus following the IRT site walk and review. Why did this reach approach
change? In Section 3.4.2, the S200 lower reach is described as “mostly stable with
limited bank erosion observed in a few localized areas” which appears to support
the initial enhancement approach. Additional justification for restoration is
required. Supplemental planting to more than 200 feet is noted as a restoration
activity, is state buffer credit proposed within this area?
15. Page 31, S200-R3 & S200-R4 – These reaches were not included in the Final
Prospectus. The IRT will need to visit the site to review these newly added credit
reaches.
16. Page 31, S300-R1 – Based on the descriptions of current conditions and proposed
work for S300-R1, please explain why this reach is proposed as Enhancement II
at a 3:1 ratio? Given the size of the drainage area, is flow a concern?
17. Page 32, S300-R2 – Based on the descriptions of current conditions and proposed
work for S300-R2, calling the reach Enhancement at 7.5:1 seems more
appropriate than preservation if it is not high quality.
18. Page 33, Wetland Reestablishment – Please confirm that all depressional areas
will be less than 12 inches deep.
19. Page 39, Section 6.5.1 – Is the reference data sourced from the Turtle Creek
mitigation project reaches or the reference sites used to design the Turtle Creek
project reaches? Is the composite reference data being used in the design of the
proposed headwater valley or single stem channel?
20. Page 40, Section 6.6 – Given that the site has 30 acres of wetland restoration and
enhancement credit area and that wetlands are meant to develop within headwater
valleys, it is not suitable to have a single sitewide plant list. It is helpful to have
planting areas mapped differentiating between full vs. supplemental planting areas
and within vs. outside the 200-ft buffer planting areas. Additionally, planting zones
need to be created for the site based on proposed habitat types and expected
hydrology. Similarly, please consider splitting the sitewide seed mix into
wetland/floodplain and upland buffer mixes.
21. Page 41, Section 6.6.1 – Black willow is not included in Table 17, is it the only live
stake species being proposed? Please provide a minimum of two live stake
species.
22. Page 43, Section 6.7.2 – The inclusion of floodplain improvement features is
appreciated.
23. Page 44, Section 6.7.4 – The encroachment section appears to be a standard
description. Please provide a site-specific response taking into consideration the
adjacent PRM site and the proposed long-term steward’s intent to manage the
property for public recreation. What are the risks associated with public access,
proposed burning on the property, etc.?
24. Page 46, Section 8.1 – If the IRT is concerned about flow in S300-R1 during
monitoring, installation of a flow gauge may be required.
25. Page 46, Section 8.2 – Please note that 30 consecutive days of flow annually is
the minimum performance standard.
26. Page 46, Section 8.3 – In the first sentence please clarify a minimum 12 percent
hydroperiod annually. Please specify the growing season start and end dates.
27. Page 47, Section 8.4 – Consider removing the 3-yr old, 5-yr old, and 7-yr old
references since stems planted during monitoring can count after 2 years as well
as some volunteer stems.
28. Page 48, Section 9.1 – Please specify the total number of cross-sections, pressure
transducers, and flow gauges proposed for this project.
29. Page 51, Section 9.3 – All areas planted areas within the project site must be
monitored. This includes planted areas within and outside of the 200-ft creditable
buffer, as well as areas planted within the 100-ft headwater valley. Please adjust
the number and distribution of proposed fixed and random veg plots accordingly.
30. Page 53, Table 20 – Why isn’t wetland monitoring information included in the
proposed monitoring plan summary? Also, please specify four bankfull events
under the hydraulics performance standard.
31. Page 53, Section 10 – The long-term steward engagement letter and fee
breakdown was not included in Appendix D. Will the mitigation site endowment
account be managed separately from funds to manage the property for public
recreation and education (e.g., trail maintenance, educational signage/structures,
prescribed burning, etc.)?
32. Figure 8 – Are all existing culverts shown? Please show NCSAM, NCWAM, and
DWR Stream ID data points. Do the existing stream origin points reflect the DWR
stream determination? Existing streams and ditches appear to vary from the
USACE Jurisdictional Waters Map Figure 6.
33. Figure 9 – Will the road upstream of S100 be decommissioned? Please
differentiate between existing roads proposed to remain vs. be decommissioned.
Please confirm the as-built and CE shown is the PRM site (not a bank) and add a
border to better define that project boundary. Also, please address previous
comments (i.e., reach names, ditches, culverts).
34. Figure 10
a. In order to monitor channel stability following the installation of in-stream
structures and bank treatments, please add a cross section along S300-R1.
b. Please shift the most southeast non-riparian reestablishment groundwater
gauge to the approximate location of the pre-construction GW5 gauge.
c. Please change the legend label for the purple veg plot to reflect as shared
or joint plots for the 404/401 and state buffer/nutrient projects. Please make
veg plot adjustments based on the earlier Section 9.3 comment.
35. Appendix G – The Initial Evaluation Letter discusses adjusting the project
easement boundary if a few locations. The Final Prospectus addressed some of
these adjustments, but the draft mitigation plan reverts to the original boundary.
Please explain why the requested changes could not be implemented.
36. Design Plan General Comment – The plane view background as well as many
features were not visible on the printed hardcopy. This review had to be done from
the digital version.
37. Sheet 4 – Please explain the typical sections for S100 R1 and S200 R1-R4. Are
riffles, pools and bankfull features proposed for these headwater valley reaches?
38. Sheet 5 – Is Ditch 2 remaining open or partially filled? If so, please provide
proposed ditch dimensions (including max. depth).
39. Sheet 6 – Is S100-R2 a Priority 2 restoration? Why is the left floodplain more
confined with a steeper side slope?
40. Sheet 7 – Is this sheet showing a constructed channel along S200-R1 that
transitions to no channel along S200-R2?
41. Sheet 10 – S200-R4 appears to be a single stem channel restoration with riffles
and pools and bank treatments. Are multiple flow paths expected to form in the
valley? Will the headwater valley performance criteria be achievable?
42. Sheets 11-13 – Please callout the top of bank along S300.
43. Sheet 12 – Is removal of the existing structure and bridge mentioned in the plan
narrative? What is the structure?
44. Sheets 14-15
a. The Wetland Grading Plan is busy. Please consider using a bold border or
another alternative to pattern fill for the credit areas.
b. It was difficult to follow existing contour lines, particularly because there
were no elevations labeled. It would be helpful to see spot elevations across
the site to provide a better landscape perspective.
c. The only proposed grading contour lines appear to be connected to the
headwater valley construction and ditch filling. The plan narrative mentions
minor grading within W02 and W03 reestablishment and enhancement
areas, and creation of natural depressions within the reestablishment areas.
If depressions are proposed, please show approximate locations on design
sheets. Other than spoil and road removal, will there be any excavation
within wetland credits area greater than 12 inches? If so, please clearly
denote these areas.
d. It would be helpful to have existing ditches called out as to be filled, partially
filled, or remain open. Please confirm whether any of the existing ditches
located within the wetland preservation credit area shown on Figure 8 are
proposed to be plugged/filled.
45. Sheet 15 – Is there an existing ditch immediately adjacent to the eastern easement
boundary? If so, it would be helpful to call out the ditch top of bank. And include
the ditch in the lateral drainage effect analysis.
Sincerely,
Todd Tugwell
Chief, Mitigation Branch
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