HomeMy WebLinkAbout20161044 Ver 1_MP IRT Comment Response_2017-12-08_20180226
MEMORANDUM
TO: Paul Wiesner, NC DMS
FROM: Emily Reinicker, PE
DATE: December 8, 2017
RE: Lone Hickory Mitigation Site
Yadkin County, NC
USACE AID#: SAW‐2017‐00100, NCDMS #: 97135
FINAL Mitigation Plan – IRT Comment Response
This memo documents NCIRT’s Mitigation Plan review comments (in italics) received from Kim
Browning’s letter dated 11/14/17, the project team’s responses, and where the revisions have been
included in the final Mitigation Plan.
Mac Haupt, NCDWR, November 13, 2017:
1. DWR questions whether there is enough hydraulic energy that supports constructing a channel
at the toe of the slope for tribs UT2B and UT2A. In addition, it would seem historically at this
landscape position there would be a toe of slope wetland that then may transition to a single
thread channel.
a. Wildlands acknowledges this concern referenced in comments #1, 14, and 25. Due to
the contributing drainage area, the defined upstream channel on UT2A, and the
observed groundwater hydrology inputs on UT2B, it is appropriate to develop the site
design treating these features as restored stream channels. We acknowledge that if
these features do not meet the prescribed success criteria for functioning stream
features at the end of the monitoring period, then we will not receive stream credits for
the affected reach(es). No revisions have been made to the Mitigation Plan.
2. DWR notes that on Figure 11.1 that there are stream gauges planned to be installed on tribs
UT2A and UT2B. DWR would like those gauges installed no further down than mid reach. DWR
recommends the placement of the gauge for UT2A just before the proposed wetland polygon on
Figure 11.1.
a. Wildlands will install the a stream gage at midreach on UT2A and UT2B. The Mitigation
Plan text on page 42, Section 8.1.5 Hydrology has been modified to state that “low flow
channels (UT1 Reach 1, UT2A, and UT2B) will each have a stream gage pressure
transducer installed midreach to document 30 consecutive days of baseflow.” Figure
11.1 has been revised to show the proposed stream gage and monitoring cross sections
located upstream of the proposed wetland polygon on UT2A.
3. In Section 4.0, the functional uplift is discussed based on the Stream Pyramid. While the
discussion was fine, given the fact that there seems to be a lot of potential for functional uplift,
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DWR recommends that the measurements are performed related to the Quantification Tool to
provide more quantifiable evidence of the actual uplift. If discussions of the Stream Pyramid are
undertaken, DWR likes to see the Quantification Tool and the tables included in the Mitigation
Plan (for future projects).
a. Wildlands used observations and terminology from the functional pyramid to
qualitatively describe stream conditions on the site, as requested in DMS’s newest
mitigation plan template as required within our DMS contract. Wildlands does not
propose to use the functional pyramid to determine the success of the mitigation site.
The following text changes have been made in Section 4.0‐ Functional Uplift Potential on
page 15 of the Mitigation Plan based on this comment: “The potential for functional
uplift is qualitatively described in this section using terminology from the Stream
Functions Pyramid (Harman, 2012). The Stream Functions Pyramid describes a hierarchy
of five stream functions, each of which supports the functions above it on the pyramid
(and sometimes reinforces those below it). The five functions in order from bottom to
top are hydrology, hydraulics, geomorphology, physicochemical, and biology. Neither
the Stream Functions Pyramid nor the Quantification Tool are proposed to determine
success of the mitigation site.” See also comment #16.
4. Section 7.2.2, Groundwater Modeling, discussed the approach for determining the wetland
hydrologic performance criteria. DWR accepts the 9.2% wetland saturation standard arrived at
from modeling, other site data and discussions with the IRT on‐site. DWR would like to caution,
however, that when grading the wetland site that no more than 12 inches of cut is taken,
anymore would result in wetland creation rather than re‐establishment.
a. As discussed during the Post‐Contract IRT Site Walk for Wetland Soils Evaluation
(January 25, 2017 notes included in Appendix 9), overburden removal will generally be
limited to 12 inches. There is obvious crowning between the two major ditches draining
the proposed wetland area. Some grading in this area is slightly deeper than 12 inches;
this grading was discussed and approved at the Post‐Contract IRT Site Walk for Wetland
Soils Evaluation based on the obvious manipulation of the site for agriculture.
Additionally, grading around stream channels to tie the proposed streams to the
proposed wetland area may result in grading depths just over 12 inches. This is a
byproduct of grading the streams into the wetland valley and is not a result of the
wetland design. As stated on page 39 of the report, “Cut depth is limited to
approximately 12 inches throughout the site.” No changes have been made to the
Mitigation Plan based on this comment.
5. Page 40 (first paragraph) references Table 22 and should reference Table 21.
a. This reference has been updated to Table 21.
6. Section 8.0, Performance Standards, references the April 2003 USACE Stream Guidelines as the
basis for the guidance of the performance criteria. This document should have referenced the
October 2016 Mitigation Update from the IRT. While DWR realizes the project was initiated
before the 2016 Guidance came out, the Mitigation was written and finalized well after that
date.
a. Section 8.0‐ Performance Standards on page 41 of the Mitigation Plan has been updated
as follows: “The stream and wetland performance standards for the project have been
developed based on guidance presented in the DMS Mitigation Plan Template (October
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2015), the Annual Monitoring Template (April 2015), and the Stream and Wetland
Mitigation Guidance issued October 2016 by the USACE. Annual monitoring and semi‐
annual site visits will be conducted to assess the condition of the finished project.
Specific performance standard components are proposed for stream morphology,
hydrology, vegetation, and wetland hydrology. Performance criteria will be evaluated
throughout the seven year post‐construction monitoring period.”
b. Several of the performance standards have been updated to reference details of the
2016 guidance:
i. A note has been added to Section 8.1.1‐ Dimension: “Please note that UT3 Reach
3 is designed to incise as it transitions to meet the invert of South Deep Creek
and this reach is expected to have a bank height ratio greater than 1.0 and an
entrenchment ratio less than 2.2.
ii. Section 8.1.5‐ Hydrology has been edited: “The occurrence of bankfull events
will be documented throughout the monitoring period. Four bankfull flow
events must be documented within the seven‐year monitoring period. The four
bankfull events must occur in separate years. In addition, low flow channels
(UT1 Reach 1, UT2A, and UT2B) will each have a stream gage pressure
transducer installed midreach to document 30 consecutive days of baseflow.
iii. Section 8.2‐ Vegetation has been edited: “The final vegetative performance
standard will be the survival of 210 planted stems per acre in the planted
riparian areas at the end of the required seven‐year monitoring period. The
interim measure of vegetative success for the Site will be the survival of at least
320 planted stems per acre at the end of monitoring year three (MY3) and at
least 260 stems per acre at the end of MY5. Trees in each plot will average 7
feet in height at MY5 and 10 feet in height at MY7.” See also comment #24.
7. In the Monitoring Components Section, Table 23, I believe there should be 15 total plots.
a. Table 23 has been revised to show 15 plots total, comprised of 10 permanent and 5
mobile plots.
8. Buffer width calculations‐DWR would like Wildlands to perform the buffer width calculations
based on the new method.
a. Wildlands has verified that the mitigation credit adjustment for non‐standard buffer
widths are based on Table 2 of the October 24, 2016, USACE guidance. No changes have
been made to the Mitigation Plan based on this comment.
9. There appears to be a significant impact on current jurisdictional wetlands for the upper reach of
UT1. DWR realizes that this is the old pond bed where the headcut is currently active. DWR
would like to know what steps will be undertaken to minimize the effect on the wetlands or will
there be other measures to offset the loss other than the proposed wetland re‐establishment.
a. Full valley restoration, which includes excavation of the former pond beds (which are
filled with sediments and cattle waste), has been the proposed approach since the
beginning of this project. Wildlands discussed this approach during the IRT post‐
contract site meeting, as included in the meeting notes in Appendix 9. The imminent
failure of the dam will not only destroy these wetlands but will be a mass
sediment/animal waste input to the downstream system. No direct offset measures are
proposed but we do expect wetlands to form on the restored floodplain and vernal
pools. The restoration of the historic valley discussed in Section 5.3‐ 401/404 on page
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21 of the Mitigation Plan, has been edited to add: “The valley floor will be restored at or
near its historic gradient. The restoration will impact the wetlands that have formed
around the impoundments; however, new riparian wetlands associated with the Priority
1 stream restoration are likely to form on the restored valley floor, and the real and
present threat posed by the advancing headcuts as they cut into the old pond beds will
be eliminated.” The IRT has expressed concern on past projects of the constructability
of stream channels in former pond beds containing unconsolidated materials. The
proposed valley restoration is the most holistic ecological uplift approach for the site.
10. On the Design sheets for UT1 DWR noted several areas of high slope with long riffles and no
grade control structures (stations 116+00, 121+00, and 125+00). One riffle starting at
approximately sta 120+25 is about 170 feet long. One concern is that there will be a lot of rock in
the channel and the other concern is of stability given the slope and length. DWR would like a
justification for this approach for these areas.
a. The structure detail for these long riffles shows log and rock steps with micropools
throughout. This will be built in the field and each step and micropool was not detailed
in the profile callouts. A sample plan & profile sheet with a photo of the newly
constructed channel is attached at the end of this letter to demonstrate how this
approach was implemented at the Candy Creek Mitigation Site last year. No changes
have been made to the plans as a result of this comment.
11. DWR would caution the design of the meander at sta 307+50 along UT3. The design ratio of
curvature seems pretty tight for this meander and DWR would ask that Wildlands look again at
this section.
a. This meander has a radius of 38 feet and a radius of curvature ratio of 2.3, which is
within the reference and design parameters. Brush toe is also provided in the bend,
which will protect against toe scour. No changes have been made to the plans as a
result of this comment.
12. DWR noted that for UT1, all of the grade control structures involve rock or log sills at the end of a
type of constructed riffle. In addition, for the typicals shown on Design sheet 6.3, neither the log
or rock sills show footers. DWR is concerned with the ultimate stability of these structures in
these high gradient environments. Is Wildlands discontinuing the use of rock cross vanes? How
have these structures performed on other projects?
a. Wildlands reserves the use of rock vanes for discrete locations such as upstream of
bridges or adjacent to infrastructure with limited working space. We have not found
rock cross vanes to be the best use of resources. We have revised the rock and log vane
structure details on Sheets 6.1‐6.4 to include footers.
13. DWR was not able to attend the July 19, 2016 site visit to see the entire site. DWR would
appreciate if you could send some photos of reach UT1, particularly reach 2A and 2B. Given the
amount of bedrock on this reach, it would be nice to see some evidence of the incision, stream
banks or bedform to justify moving the channel.
a. Photos of these reaches have been added to Appendix 4.
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Kim Browning, USACE, November 13, 2017:
14. UT2A and UT2B—The field notes from July 19, 2016 indicate the concern for lack of flow and
creating a possible wetland complex. Flow monitoring/gauges needed.
a. Wildlands will install a stream gage at midreach on UT2A and UT2B. The Mitigation Plan
text on page 42, Section 8.1.5 Hydrology has been modified to state that “low flow
channels (UT1 Reach 1, UT2A, and UT2B) will each have a stream gage pressure
transducer installed midreach to document 30 consecutive days of baseflow.”
15. Figure 2 Site Map and Figure 6 Concept Map show a channel labeled as UT2C. While Figure 8.1
Concept Map and Figure 11.1 Monitoring Plan shows the same channel labeled UT2B.
a. Labels have been verified on the figures.
16. Section 4 Functional Uplift Potential, page 15: The functional pyramid is cited to show existing
conditions for each category, and was used to describe the functional uplift potential of the
project, which is appreciated. Please note that the functional pyramid and QT tool have not been
approved for use in determining success for mitigation projects. No standards for collection
protocol are addressed in the plan, nor are score sheets, sampling location and number of
samples discussed.
a. Wildlands used observations and terminology from the functional pyramid to
qualitatively describe stream conditions on the site, as requested in DMS’s newest
mitigation plan template as required within our DMS contract. Wildlands does not
propose to use the functional pyramid to determine the success of the mitigation site.
The following text changes have been made in Section 4.0‐ Functional Uplift Potential on
page 15 of the Mitigation Plan based on this comment: “The potential for functional
uplift is qualitatively described in this section using terminology from the Stream
Functions Pyramid (Harman, 2012). The Stream Functions Pyramid describes a hierarchy
of five stream functions, each of which supports the functions above it on the pyramid
(and sometimes reinforces those below it). The five functions in order from bottom to
top are hydrology, hydraulics, geomorphology, physicochemical, and biology. Neither
the Stream Functions Pyramid nor the Quantification Tool are proposed to determine
success of the mitigation site.” See also comment #3.
17. Section 7.7.1, page 37: NRCS stands for Natural Resources Conservation Service. Please correct
the text in the last paragraph on the page.
a. Text has been corrected.
18. Section 8.0 Performance Standards, page 41: The plan states, “Wildlands may propose to
terminate stream and/or vegetation monitoring after five years.” The monitoring program
should be implemented for 7 years.
a. The early termination reference has been deleted. The text in Section 8.0‐ Performance
Standards on page 41 now simply states: “Performance criteria will be evaluated
throughout the seven‐year post‐construction monitoring period.”
19. Page 40: The text references Table 22, but the table is labeled Table 21.
a. The text has been revised.
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20. Section 8.2 Vegetation, page 42: Please include a discussion on vigor (vegetation height).
a. The following statement has been added to Section 8.2‐ Vegetation on page 42: “Trees
in each plot will average 7 feet in height at MY5 and 10 feet in height at MY7.”
21. Section 8.3 Wetlands, page 42: The text reads, “If a gage does not meet the performance
standard for a given monitoring year, rainfall patterns will be analyzed and the hydrograph will
be compared to that of the reference wetlands." Please keep in mind that performance
standards for wetland hydrology must be met.
a. Wildlands acknowledges this comment and the fact that success criteria must be met
for the mitigation site to qualify for wetland credits. No changes have been made to the
Mitigation Plan based on this comment.
22. Section 7.6, pages 35‐36: The removal of existing dams is discussed. Please expand on your
description on how the existing pond bed will be handled, and where the sediment will be
spread.
a. The existing dams and pond bed sediments will be excavated to restore the historic
valley topography. Wildlands is under option to purchase the entirety of the parcels
comprising the mitigation site. We are still working on grading plans, but in general we
expect this material will be placed in the agricultural field to the east of UT1 Reach 1.
Fill will not be placed in jurisdictional stream or wetland features.
23. Section 12.0, page 48: the first paragraph references Table 27. I believe this was meant to be
Table 26.
a. The text has been revised.
24. Section 8.0, Performance Standards, references the April 2003 USACE Stream Guidelines;
however, Section 12.0, Determination of Credits, references the October 2016 USACE guidance
for Additional Credits for buffers. While the USACE encourages establishing buffers that exceed
minimum standard widths, it would be preferable if only one guidance document was referred to
for consistency.
a. Section 8.0‐ Performance Standards on page 41 of the Mitigation Plan has been updated
as follows: “The stream and wetland performance standards for the project have been
developed based on guidance presented in the DMS Mitigation Plan Template (October
2015), the Annual Monitoring Template (April 2015), and the Stream and Wetland
Mitigation Guidance issued October 2016 by the USACE. Annual monitoring and semi‐
annual site visits will be conducted to assess the condition of the finished project.
Specific performance standard components are proposed for stream morphology,
hydrology, vegetation, and wetland hydrology. Performance criteria will be evaluated
throughout the seven‐year post‐construction monitoring period.”
b. Several of the performance standards have been updated to reference details of the
2016 guidance:
i. A note has been added to Section 8.1.1‐ Dimension: “Please note that UT3 Reach
3 is designed to incise as it transitions to meet the invert of South Deep Creek
and this reach is expected to have a bank height ratio greater than 1.0 and an
entrenchment ratio less than 2.2.
ii. Section 8.1.5‐ Hydrology has been edited: “The occurrence of bankfull events
will be documented throughout the monitoring period. Four bankfull flow
events must be documented within the seven‐year monitoring period. The four
7
bankfull events must occur in separate years. In addition, low flow channels
(UT1 Reach 1, UT2A, and UT2B) will each have a stream gage pressure
transducer installed midreach to document 30 consecutive days of baseflow.
iii. Section 8.2‐ Vegetation has been edited: “The final vegetative performance
standard will be the survival of 210 planted stems per acre in the planted
riparian areas at the end of the required seven‐year monitoring period. The
interim measure of vegetative success for the Site will be the survival of at least
320 planted stems per acre at the end of monitoring year three (MY3) and at
least 260 stems per acre at the end of MY5. Trees in each plot will average 7
feet in height at MY5 and 10 feet in height at MY7.” See also comment #6.
Steven Kichesfski, USACE, November 15, 2017 email to Kimberley Browning
25. I wanted to put on the record somewhere with this site my concerns for some of the features like
the upper portion of UT2a (and probably UT2b) based on my jd site visit (I haven't seen the
proposed mit plan). This channel seemed to barely meet jurisdiction as a WoUS and seems risky
if lifted onto the floodplain that it will maintain enough flow to stay a stream in this broad
floodplain, especially if flow is dispersed to create adjacent wetland areas. I'm not suggesting
that this is an inappropriate design, simply that it may be a future monitoring/credit issue to
demonstrate that it is functioning as stream. I mentioned this to Wildlands in the field and
thought it should be in the file (if not already) so it's not a surprise during monitoring/credit
release discussions.
a. Wildlands acknowledges this concern referenced in comments #1, 14, and 25. Due to
the contributing drainage area, the defined upstream channel on UT2A, and the
observed groundwater hydrology inputs on UT2B, it is appropriate to develop the site
design treating these features as restored stream channels. We acknowledge that if
these features do not meet the prescribed success criteria for functioning stream
features at the end of the monitoring period, then we will not receive stream credits for
the affected reach(es). No revisions have been made to the Mitigation Plan.