HomeMy WebLinkAbout20180786 Ver 1_IRT Comment Responses_20200217
Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609
December 12, 2019
Ms. Kim Browning
Department of the Army
Wilmington District, Corps of Engineers
69 Darlington Avenue
Wilmington, NC 28403‐1343
RE: Sandy Branch Mitigation Site – NCIRT Comments during 30‐day Mitigation Plan Review
Sandy Branch Mitigation Site (USACE AID# SAW‐2018‐01167, NCDMS # 100060)
Cape Fear 03030003, Chatham County, NC
Dear Ms. Browning,
Thank you for compiling and providing comments on the Sandy Branch Mitigation Site final draft Mitigation Plan. We
have reviewed the comments dated November 4, 2019 and have revised the Mitigation Plan accordingly. This letter
includes a response to each comment; comments have been reprinted with our response in italics. The revised
Mitigation Plan is being submitted with this letter.
DWR Comments, Erin Davis and Mac Haupt
1. Page 3, Section 3.3 – Why weren’t aerials from 2006 to 2018 reviewed? Google Earth aerials from 2008 and
2009 of the Project Location show clearing of both forested buffers of UT2 upstream of the proposed
restoration reach. Additional clearing of the Project Location immediately adjacent to the proposed easement is
shown on 2017 and 2018 aerials (not shown on plan figure basemaps). Please include a description of recent
Project Location land cover changes.
Section 3.3 will be revised to include the following description of land use changes on UT2: “The
landowner conducted some tree clearing activities along UT2 upstream of the project in 2007/2008 and
again in 2017. The landowner cleared a wooded buffer around the upstream channel in 2007/2008 to
create a larger hay field. Figures A and B (See Appendix 2) show this area before and after the clearing.
Although the stream and wetland determination for this project did not extend that far upstream, we
believe this area would delineate as ephemeral stream channel. Additionally, this portion of the Cape
Fear 03 subbasin does not have riparian buffer rules. A comparison of Figures A and B does not indicate
that the stream was channelized during the clearing process.
Additional clearing was conducted downstream of the area described above in 2017. A review of historic
aerials showed this area was a farm pond in 1993 (See Figure C, Appendix 2). By 2007 the dam had been
breached but the immediate riparian corridor was maintained as cattle pasture without any apparent
channel dredging (See Figure D, Appendix 2). The available aerials between 1993 and 2007 are not clear
enough to pinpoint the date of dam removal more precisely. The immediate riparian corridor was
maintained as cattle pasture up to the point of clearing activities in 2017, so it appears very few, if any,
trees were removed within 30 feet of the stream channel.
Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609
Finally, the landowner improved a farm road in conjunction with the 2017 clearing along UT2. It is clear
in the 2007 aerial (See Figure D, Appendix2) that the landowner maintained this farm road below canopy
cover as with the current roads in the woods between the project area and the farmhouse. Overall, it is
Wildlands’ opinion that no rules were violated in the 2007/2008 clearing, the 2017 clearing, or the
concurrent farm road improvement.”
2. Page 8, Section 3.6 – Please note the NC SAM results in the existing conditions discussion.
The NC SAM results are noted in the existing conditions discussions and listed in Table 7.
3. Page 11, Section 5.3 –
a. The proposed easement break appears like it would lead to clearing of the forested area west of the
easement for access and still require livestock to cross UT1 just upstream of the easement boundary to
arrive at the east pasture. Was an easement break considered where the proposed easement narrows
along Reach 2 (area cleared in 2017‐2018) and there appears to be an existing stream crossing location?
There is an existing path through the forested area directly to the west of the proposed
easement break. The path is under tree cover and cannot be seen from aerial imagery. The path
serves an existing stream crossing at the proposed easement break location. Locating an
easement break where the proposed easement narrows along Reach 2 would result in significant
impacts to trees.
b. DWR recommends a 50‐ft setback of the proposed easement from the existing road edge to avoid
potential future transportation easement encroachment requests.
The easement was designed to align with the edge of right of way and right of way fencing.
Leaving a gap would allow cattle access at the upstream end of the project. Additionally, the
culvert under Elmer Moore Road was replaced in 2017 so is unlikely to be replaced again in the
next 30 years.
4. Page 21, Section 8.6.1 & Design Plans – The text notes that channel plugs will be constructed. Please show
proposed plug locations on the plan view sheets and include a typical detail. DWR requests plugs be a minimum
of 50 feet wide and include high clay content substrate.
The plugs discussed in this section were proposed only where the abandoned channel features tie to
Sandy Branch. We have not typically used details and specifications to describe these plugs to the
contractors, rather it has been explained in the field that we want to use high clay content soil and
compact the soil by driving over the plug with machinery. This has not been a problem on any past
projects.
5. Page 24, Section 9.2 – DWR recommends treating woody invasives annually.
Wildlands approach to invasive species management is to conduct quarterly site visits where sporadic
invasives are treated. Any larger populations are dealt with at the appropriate times of year and
followed with continued control as needed. The frequency may be annual or more or less often.
6. Page 24, Section 9.4 – As per the 2016 IRT Guidance, the soil temperature needs to be tied to tree bud burst.
DWR requests that the tree species to be used to correlate bud burst with soil temperature for growing season
start be identified in the MY0 report.
The MY0 report will identify the tree species that will be used to corroborate the start of the growing
season.
Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609
7. Figure 9 – There is a narrow linear wetland (approximately 5 feet wide) that is being requested for rehabilitation
credit but is not located within the proposed wetland planting zone. Also, was the area between this linear
feature and Reach 1 (Sta. 105+50 – 108+00) considered for wetland re‐establishment?
The planting zones are meant to show planting approaches for the site on a macro scale, at
approximately 1/10th acre levels of detail. The planting methods used by project planting crews are not
compatible with very small and intricate planting zones. However, the planting list for the buffer planting
zone, the zone in which this linear wetland is situated, includes wetland‐tolerant species.
The area between the linear wetland feature and Reach 1 (Sta. 105+50 – Sta. 108+00) was not requested
for wetland re‐establishment credit because the area is significantly higher than the surrounding ground.
8. Figure 10 – See mark‐up of DWR’s requested groundwater well gauge location shifts.
The three groundwater well gauges have been moved based on DWR’s request.
9. Appendix 3 – On the provided map, please include all gps soil check points within and outside of the delineated
hydric soil areas in substantiation of the site investigation. Three soil borings are not sufficient for a detailed
baseline report of an 18‐acre assessment area.
GPS points were not collected at all soil check points. GPS points were collected at each vertex of the
“Hydric Soils” polygon. Multiple observations were made along transects to locate the hydric soil
boundary at each vertex. The three profile descriptions and corresponding locations indicated on the
map are intended to represent typical soil profiles within the assessment area.
10. Design Plans – Please show the CE line on all plan view sheets using the assigned legend icon.
The CE boundary lines shown on plan sheets have been updated to match the legend on plan sheet 0.3.
11. Sheet 1.05 – Regarding the lunker structure, DWR is ok with trying new bank stabilization techniques. However,
we are a bit concerned about the proposed location adjacent to a wetland with the potential lateral hydrologic
migration impacting structure stability.
The proposed lunker structure adjacent to the existing wetland (Sandy Branch Reach 2, Sta. 125+53) has
been replaced by proposed brush toe.
12. Sheet 1.08 – An existing culvert crossing of UT1 is proposed to be removed near the eastern easement
boundary. Please confirm whether livestock will need to continue to cross UT1 to access pasture area. If so,
DWR would like to see a ford or culvert crossing constructed adjacent to the easement to protect UT1 as it
enters the project area.
Livestock will need to continue to cross UT1 to access pasture area. A new culvert crossing is planned for
UT1 at approximately 190 linear feet upstream of the easement boundary. This proposed crossing is
shown on plan sheet 1.08.
13. Sheets 4.0‐4.02 – DWR appreciates the inclusion of a fencing plan with approximated gate locations.
Thank you.
USACE Comments, Kim Browning
1. The correct USACE Action ID is SAW‐2018‐01167. Please correct the cover page.
When submitting the JD package to the USACE county project manager, please reference the established Action
ID (issued during the Public Notice) to prevent multiple IDs being assigned. The NWP cannot be authorized if the
impacts are not associated with the correct Action ID.
The USACE Action ID has been corrected on the mitigation plan and on the plan set.
Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609
2. Section 4.0: Regarding DWR’s comment #1, the project easement does not appear to have had any recent
clearing or channelization; however, UT2 may have impacts due to recent upstream clearing (in 2008 and 2017).
It also appears that crossings may have been installed upstream of UT2, and portions of that reach may have
been straightened. While these activities did not occur within the proposed easement, they do appear to be on
the same property parcel. Authorization of the NWP has the potential to be halted if there are potential
violations on the parcel.
See response to DWR comment #1, above.
3. Section 8.7.2: It would be beneficial to add some coarse woody debris to the depressional areas in the buffers
and throughout the adjacent wetlands for habitat, and to help store sediment, increase water
storage/infiltration, and absorb water energy during overbank events.
Thank you for the suggestion. This feature will be incorporated during construction.
4. Section 8.8: Please discuss how fescue will be treated within the buffer establishment area.
Fescue will be chemically treated and then mechanically ripped to a depth of 18 inches.
5. When submitting the PCN, please include an estimate of the number of trees, or acres, to be cleared for the
NLEB 4(d) Rule.
The PCN will include an estimate of the number of trees or acres to be cleared.
6. Section 9.2: Please add a vigor standard of seven feet in height for MY5.
The height requirement for MY5 has been added.
7. Table 17: Performance standard 9.1.3 discusses sampling channel substrate material. This section should
reference which goal this is tied to. Additionally, will the performance standard be set specific substrate size, or
simply monitor coarser materials in riffles and smaller particles in pools over the monitoring period?
“Reachwide pebble counts” was added to Table 17 as a monitoring metric for the goal “improve stream
channel stability.” The performance standard for the monitoring metric “reachwide pebble counts” will
be the presence of coarser material in riffles and finer material in pools over the monitoring period. This
performance standard has been added to Table 17.
8. Design Sheet 2.0: Please cap the planting of green ash to 5% for the Priority 1 floodplain and wetland planting
zones.
Green Ash has been removed from the planting zones.
9. During the IRT site visit in 2018, drainage tile shards were found in UT1. Please discuss existing drainage and tile
locations.
After further investigation, it is believed that the pieces of ceramic debris found in UT1 are remnants of
an old culvert. We plan to explore several additional areas during construction when equipment is
available.
10. USFWS responded that their letter from Nov. 8, 2018 would still be applicable. (attached)
Thank you.
If you have any questions please contact me at jhutton@wildlandseng.com, (919)851‐9986 x 102.
Sincerely,
John Hutton Project Manager