WLS N02_Scarborough MY2 Comment Memo

DEPARTMENT OF THE ARMY
WILMINGTON DISTRICT, CORPS OF ENGINEERS
69 DARLINGTON AVENUE
WILMINGTON, NORTH CAROLINA 28403-1343
CESAW-RGM/Isenhour December 21, 2022
MEMORANDUM FOR RECORD
SUBJECT: Action ID # SAW-2017-02527 NCIRT Review Comments on WLS Neuse 02
Umbrella Mitigation Bank, Scarborough Mitigation Site Year 2 Monitoring Report
Todd Bowers, USEPA:
1. I appreciated the excellent drone photos and footage of the site. It's a really
becoming a beautiful site viewed from above.
2. On the surface, stream flows and stability appear to be meeting all applicable
performance standards. I am somewhat concerned with some aggradation and
dense vegetation growing in the channel as evidenced by data, graphs and
photos for XS 9 and 11-14. A drier than normal year is likely contributing,
however a detailed explanation from WLS should follow in MY3 if this trend
continues.
3. Headwater channel formation was present for UT1-R1, UT1 B, UT2, and UT3,
however the range of indicators was 2-4 out of 9 with some channels exhibiting
fewer than MY1 and some only a single indicator aside from observed flow. I
don't recall how many of these indicators need be exhibited (from the mitigation
plan?) to be considered an established headwater steam but performance
appears very weak thus far and I hope to see some notable improvement with a
year of normal to higher than normal rainfall.
4. Unfortunately, the view from below is much more concerning. The site
experienced rainfall below the 30t" percentile for 4 of 7 months in the growing
season. This almost certainly had a detrimental effect on much of the site's
hydroperiod and the subsequent lack of wetland hydrology for much of the site.
The trend is also not especially encouraging as more wells reported less wet
conditions. Which of the 26 groundwater wells is being used for reference
wetland groundwater per Section 4: Methods? Does WLS have a suitable
reference location off -site to compare the Scarborough site to?
5. WLS appears to be responsive and taking action following beaver encroachment.
Is the sponsor willing to let the beavers stay on -site for several more months?
6. The cross section photos were great but I would like to see a similar treatment of
the culverts giving a view perpendicular to the ones included.
7. Overall, I am concerned with vegetation vigor as tree heights are mostly still
below 3 feet. No action recommended at this time but I hope to see some
substantial growth in MY3.
8. None of the random vegetation transects and only three of the 26 permanent veg
plots did not meet minimum interim performance of 320 stems per acre. Overall
average (planted) stem count is 418 and trend is toward success, with approved
species volunteers beginning to occupy the site. Noted.

-z-
9. No invasive species treatments in MY2 with some work anticipated for MY3.
Noted.
Overall, I am somewhat pleased with the report findings and the work that has been
completed at the site. Most of the results thus far are encouraging and trending towards
success. However, serious issues remain with regard to wetland hydrology performance
and the trend towards wetland reestablishment sitewide. Due to the poor performance
sitewide of wetland re-establishment, I recommend that the IRT consider delaying the
fourth credit release for riparian wetland mitigation units for this monitoring milestone
per the issues raised above. Following the next MY report that demonstrates improved
wetland hydrology performance, the IRT may consider releasing delayed or held credits
along with those for the milestone in question. I recommend full fourth credit release for
warm stream credits. I have no other substantial comments at this time nor am I
requesting a site visit.
Erin Davis, NCDWR:
1. The report narrative states that 3 of the 26 veg plots didn't meet interim success.
Please clarify that this is after the addition of counting volunteer stems. Also, I
don't believe eastern baccharis is on the approved planting list and therefore
would need to be reviewed/approved by the IRT to count towards veg success.
2. DWR requests cattail be treated within wetland credit areas.
3. Please call out the 3 beaver dam locations on the CCPV.
4. Due to herbaceous vegetation obstruction of stream channels, DWR
recommends including winter photos. We noted in -stream aquatic veg concerns
in our MY1 review. This will likely be the last year any remediation actions will be
supported by DWR to address this concern. We will want to see how these areas
naturally trend (wetland vs stream) after MY3.
5. Even with the below normal rainfall, DWR is concerned with the number of
wetland gauges that did not meet the minimum success threshold. Of the 15
gauges that didn't meet, 8 also didn't meet in MY1. Adaptive management may
need to be considered. DWR is requesting to visit the site as part of the MY3
review.
Kim Isenhour, USACE:
1. The drone photos and videos were very helpful for the review and supplemented
the lack of documentation on channel formation in the headwater channels. The
dye videos were particularly helpful. I would encourage this inclusion in
monitoring year 3.
2. Please provide an update on the beaver trapping on UT1 R1 and whether
vegetation was damaged, or backwater sedimentation was a concern.

-3-
3. Section 3.2.1: Please include flow data for all monitoring years for comparison in
next year's report.
4. UT1-R2 appears to have some aggradation and vegetation in the channel near
XS-11. It might be helpful to livestake this reach more heavily to help establish
shade and eliminate in -stream vegetation. Typically, MY2 is the last year that we
concur with taking remedial action to remove in -stream vegetation manually.
Same comment for UT1-R3.
5. Though the vegetation plots seem to be meeting overall, I noted that Table 5a
shows six plots that fail to meet success. Do you think that plots 5, 6, and 12
failed due to being too wet? It might be helpful to add some additional
FACW/OBL species there. MY3 will be important to assess whether the
vegetation is on a trajectory for success. I noted that two plots have 3 or fewer
species. Supplementally planting livestakes may also be necessary as very few
are evident in the photos.
6. In future monitoring reports, detailed soil profile descriptions should be recorded
for each boring where a wetland gauge is installed.
7. The number of wetland gauges that are not meeting success is concerning,
particularly given that 8 of these failed to meet success last year and the other
gauges that are meeting the criteria are well above the required performance
standard. Some of the photos of non -wetland areas appear to have wetland
vegetation, for example near XS-1 and veg plots 21-24; when you have George
Lankford look at the soils on -site this year, it might be helpful to have him
evaluate areas that are not currently marked as wetland areas. I wasn't sure if
these were buffer credit areas. If additional areas are proposed to be added, they
should be submitted as an adaptive management plan for IRT review and
monitored.
8. Gauges 16, 19, 20, 21, 22, and 23 are of particular concern and need to be
watched closely over the next year to see if this trend changes or if these areas
will need to be considered at risk. The other gauges that failed to meet success
this year appear to be trending towards success and may have been negatively
impacted by below average rainfall. 50% of this year's wetland credit release will
be held this year (5.485 WMUs).
Kimberly T. Digitally signed by Kimberly
T.Isenhour
Isenhour Date: 2022.12.21 12:13:35
05'00'
Kim Isenhour
Mitigation Project Manager
Regulatory Division