20201798 Ver 1_AsBuilt Site Visit Memo Six Runs_updated

3600 Glenwood Avenue, Suite 100
Raleigh NC 27612

res.us
To: IRT and NCDMS
From: Jamey McEachran - RES
Subject: Six Runs Mitigation Project As-Built Site Visit
Date: November 29, 2023
Attendees:
Erin Davis, USACE Todd Tugwell, USACE Danielle L. Mir, NCDMS Jeremiah Dow, NCDMS
Stephanie Goss, NCDWR Jennie Emmons, NCDWR Samantha Wooten, NCDWR Maria Polizzi, NCDWR
Jamey McEachran, RES Frasier Mullen, RES Matt DeAngelo, RES Jeremy Schmid, RES
Summary:
An As-Built site visit was held on November 8th, 2023, to walk the newly constructed Six Runs Mitigation Project with the North Carolina Interagency Review Team (IRT). The project is a full-delivery contract with the North Carolina Division of Mitigation Services (NCDMS) and RES. Comments and discussion points during the site visit are presented below:
General: The IRT had several questions at the beginning of the site visit.
1) Areas that the IRT would like to see include: the floodplain sill, ESP, PALS, pond siphon on DE8, and noncredit DE3. a. Once the group saw all of these areas there were no concerns with the installation or the design of these areas. 2) The IRT wanted to know the status of the comments DMS provided to RES on CE signage during the as-built report review. a. RES confirmed that these comments were all addressed this summer. 3) The IRT asked what the planting date was, as they only say it say March?
a. As stated in Section 1.4 Construction and As-Built Conditions “planting was completed on March
3rd, 2023”.
4) The IRT asked if planting zones were based on hydro? Vigor & diversity allowances for wetter cypress
swamp?
a. The planting plan zones were based on different hydrologic regime expectations; however, the
vigor and diversity performance criteria were not altered except to have an allowance to omit
designated understory and shrub species heights if deemed advantageous to meet height
requirements. Additionally, in the uncertainties section in the Mitigation Plan there was some
discussion of the risk to meeting these criteria and that we will continue to keep the IRT apprised
if issues were to persist.

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b. In order to pre-emptively prepare for issues, RES intentionally included the wettest species
appropriate for the target community, some of which have proven to grow successfully in
prolonged periods of inundation, such as buttonbush, black willow, hazel alder, green ash, bald
cypress, swamp tupelo, and water hickory. Furthermore, planting Zone 1-B also includes
containerized and live stakes that should increase survivability.
5) The IRT asked how are Floodplain sills different than ESP?
a. RES responded that they are different based on functional purpose; floodplain sills are logs laid
in the floodplain at grade, perpendicular to overland flow to facilitate the slowing of water down
the floodplain to decrease risk of floodplain scour. Whereas, ESPs are installed across and
ephemeral or concentrated flow feature (non-jurisdictional) to help trap sediment and promote
diffuse flow into the restored/protected features of the system.
6) The IRT asked about issues with d/s alligator weed? Not dominant? Not spraying? (Polygonum & Persicaria noted) a. RES stated that right now the alligator weed is not dominant, and we have not seen it this season, we do not intend to spray but are keeping an eye on all of the vegetation that is covering the stream channel onsite to evaluate the best approach to dealing with it without impacting our current beneficial vegetation. 7) The IRT brought up the point that in the mitigation plan it was committed to do a random plot at least once during monitoring in supplemental planted areas and wetlands w/o fixed plots. a. RES stated that above E. Darden Road there are two randoms that will remain in this easement section every year and below E. Darden Road at least one of the other randoms will ensure that other wetlands, including enhancement wetlands, will be monitored in this lower easement section. 8) The IRT asked if there were any hydro trespass concerns? a. RES noted that post construction there are no areas of hydro trespass concerns as the easement extends to topographic breaks.
9) The IRT asked if there were any concerns of sediment loading from offsite?
a. RES responded that there are some, especially upstream of BB-A which was the purpose of
installing the PALS along this reach. Additionally, in areas of concern for sediment loading, RES
installed ESPs to trap sediment before entering the stream.
10) The IRT reminded RES that they need to coordinate with the IRT when large design changes are made
during construction. As was noted in the as-built report, PALS (a new structure) were installed along BB-
B with no review coordination and no design detail. The IRT asked that RES include a detail about the
PALS with the Site Memo.
a. RES responded that they will provide future coordination with design changes like these and made
clear that these structures were not structural in nature but were put in place to trap sediment.
They are well below the top of bank (were installed less than three tenths above WSEL) and are
not intended to be permanent or hold grade. They do not affect the actual design but act more as a debris jam. A detail of the PALS design is included at the end of this memo. 11) The IRT mentioned that they thought the report photos were good. a. RES has also included more drone photos at Brad’s Branch confluence with Six Runs floodplain. 12) Biggest concern raised by the IRT: vegetation within the channel throughout the site. Vegetation found within the channel included cattails and a polygonum species. The IRT raised concern that if not dealt with early the cattails will spread and they are putting down matting in the channel that could cause structural damage to the stream. They also noted that it is up to RES to decide whether something needs to be done right now or if it needs to be done in a couple of years but that it is an area of concern they will be monitoring.

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a. RES said that we will keep an eye on the vegetation over the winter season and next
spring/summer during cross section monitoring and determine whether it is necessary to conduct
in channel vegetation spraying.
Above E. Darden Road:
• MT2 looks filled in and will have a hard time maintaining flow with the vegetation. It should be an area that is kept an eye on.
• The PALs were looked at and no real concerns were raised with their presence or function. They appeared to be trapping sediment as designed. Below E. Darden Road:
• The review team looked at the area of P2 cut that is usually a concern along Brads Brach and it was noted
that it has turned into an unexpected wetland and the vegetation is doing quite well. The only note was
that RES should watch the vegetation since trees that are not as wetland tolerant were planted here and
may have a hard time now that it has become a wetland. RES would like to clarify that this area and the
entire floodplain of Brad’s Branch is part of Planting Zone 1-A, which is composed of wet-tolerant species. Therefore, there should be less concern with survivability based on species composition.
• The IRT mentioned adding wells in this upstream section where obvious wetlands were forming and looking back on soil information and evaluation to determine the success of wetlands in this area and whether Wetland Credit is needed if it is re-establishment or creation. DE8
• The IRT raised some concern that this reach might be at risk and turn into a wetland if there is not the flow from the pond outlet to flush out the stream. This was an area the IRT asked for some photo documentation to show the evolution of the channel. DE4-A and DE4-B and surrounding Wetlands
• There was some concern about WM and to keep an eye on it as it appeared to be a high spot in the floodplain adjacent to the old channel that could be affecting the hydrology to this wetland.
• There were existing gauges in both WE-2 and WM that can be used to compare pre and post construction.
• As discussed in the general comments, this reach also had vegetation in the channel and since it is a
smaller channel there was some concern about this impacting the stream stability.

Bottom of Brad’s Branch:
• The biggest concern for the IRT at the bottom of the site is vegetation in the channel and at what point
in the downstream end will it actually be a stream with flow versus a wetland and that it is something to
watch for and keep an eye on as we go through monitoring.

Wetlands
• Some areas of WL in the re-establishment area, specifically at its upper limits, do not seem as wet as the
wetlands at the top of the site. Generally, this is something to keep an eye out for wetland success and
consider adding wells at the top of the site where there were wetlands that no credit was requested on
(Specifically GW4 and GW3).
• Wetland acreage reduction 13.798-13.670=0.128; where was the reduction (R, E, P areas)?
o The wetland reduction was tied to using a design curve for top of bank that is a true, curved line compared to the as-built top of bank that was based on a surveyed line which produces straight lines with vertex points. So, ultimately, the total area calculated using the as-built top of bank turned out to be slightly less.
• The group discussed why some wetlands had no credit generated on them even though they fell within the first 50 feet where both stream and wetland credit could be generated. RES responded that they were

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kept as non-credit for two main reasons; 1) we were way over original contract on wetlands for the DMS
project need, and 2) these areas could be considered riskier to meet wetland success because of the
extensive stream restoration work being performed; it did not seem worthwhile to claim credits prior to
construction.

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Photos of Brads
Branch Confluence
with Six Runs
floodplain post-
construction
December 2022

B B
A
A
FLOW
SECTION B-B
SECTION A-A
FLOW
STREAM BED
CHANNEL TOP
OF BANK
CHANNEL BOTTOM
OF BANK
SEE NOTES
1.5' - 2'
SMALL LOGS AND/OR
LARGE BRANCHES WITH A
MIN DIAMETER OF 3".
SMALL BRANCHES
AND BRUSH
NOTES:
1.DRIVE 2 ROWS OF 2" (MIN.) WOOD POSTS MINIMUM SPACING AND DEPTHS
SHALL BE: MIN. 1 FT SPACING, MIN. 1 FT DEPTH
2.POSTS SHALL BE OF HARDWOOD, LOCUST, OR CEDAR AND SHALL NOT BE
TREATED.
3.FILL THE VOID BETWEEN POST ROWS WITH AN EVEN MIX OF HARDWOOD
LOGS, LIMBS, AND BRUSH AS SHOWN.
4.BRUSH SHALL BE INSTALLED SUCH THAT THE TOP ELEVATION IN THE
CENTER OF THE STRUCTURE IS 0.1' TO 0.3' HIGHER THAN WSEL. BRUSH AT
THE STREAM BANKS SHALL BE INSTALLED UP TO 0.2' HIGHER THAN THE
CENTER.
5.REDUCE POST SPACING AS NEEDED TO IMPROVE STRUCTURE STABILITY.
6.LIVE STAKES SHALL BE INSTALLED ALONG BOTH BANKS ALONG THE
STRUCTURE. SEE PLANTING PLAN FOR SPECIES.
MI
N

1
.
0
'
SE
E

N
O
T
E
S
MODIFIED POST ASSISTED LOG STRUCTURES (PALS)
NTS
2" MIN. WOOD POST
SEE NOTES
SET POSTS 0.2' TO
0.4' ABOVE WSEL
SET POSTS 0.2' TO
0.4' ABOVE WSEL
0.2' MAX
LIVE STAKES
LIVE STAKES