20140334 Ver 1_Candy Creek Response to IRT comments 2016 01 06_20160329

WILDLANDS
E N G I NEE R NG
January 7, 2016
Mr. Jeff Schaffer
NCDEQ Division of Mitigation Services
1652 Mail Service Center
Raleigh, NC 27699-1652
RE: Response to Draft Mitigation Plan IRT Comments
Candy Creek Mitigation Site
DEQ Contract No. 005794
DMS ID No. 96315
Guilford County, NC
Dear Mr. Schaffer,
We have reviewed the IRT comments on the Draft Mitigation Plan for the above referenced project dated
November 25, 2015. The revised pages from the Draft Mitigation Plan are submitted with this letter as an
electronic deliverable for IRT review. Below are responses to each of your comments. For your
convenience, the comments and responses are organized sequentially by the original comment letter.
Mitigation Plan Comments and Responses
Mac Haupt, Ginny Baker, Sue Homewood, NCDWR, 29 October, 2015:
1. DWR likes the fact that this project represents a true watershed/catchment project, "...the
site will treat almost all of the headwaters of Candy Creek and 47% of the entire 3.1 square
mile watershed before it flows into the Haw River..."
RESPONSE: Wildlands agrees that this is a fairly unique opportunity to implement a
watershed -wide restoration project.
2. While DWR appreciates the watershed approach of the Candy Creek project a considerable
amount of work (grading, channel construction) will occur in the upper reaches where a mature
riparian buffer exists. While on a site visit, October 20th, Wildlands sited their experience of
building stream restoration projects through a mature riparian buffer, Little Troublesome and
Agony Acres. DWR cannot stress enough the importance of minimizing the impact to the existing
vegetation during the construction of the project.
RESPONSE: Wildlands will make a concentrated effort to protect and retain existing vegetation
during construction. We have a solid working relationship with the contractor and will
communicate the need to minimize impact.
3. The discussion of existing vegetation specifics is fairly sparse in the Mitigation Plan. DWR
suggests going into more specifics in describing what trees are present. DWR recommends
going into specifics regarding the mature trees in Reaches 1A, 1B and 1C since a lot of those
species will be subject to the channel and floodplain construction. These reaches can be
Wildlands Engineering, Inc. • phone [phone] • fax [phone] • 1430 S. Mint Street, # 104 • Charlotte, NC 28203

the examples for all the reaches that predominantly contain a mature wooded buffer.
Moreover, the existing mature canopy and shaded conditions would provide a good
opportunity to incorporate planting some shade tolerant shrubs in addition to the
proposed species list with the understanding of the IRT that height requirements would not
be applicable for these shrubs. DWR also wondering whether any planting was planned of
herbaceous species in the vernal pools created from filled channels.
RESPONSE: Specific species of hardwoods in Reach 1 were added to section 4.6.1 while
construction impacts relating to these species are detailed in section 9.5.2.
Shade tolerant shrub species were added to the Buffer Planting Zone on plan sheet 3.0 and in
mitigation plan section 9.5.2.
An herbaceous species list was added to the planting plan schedule for vernal pool areas, per the
attached plan sheet 3.0. Vernal pool limits will be finalized during the final design process and
shown in the planting plan sheets.
4. The areas of floodplain cut that the Mitigation Plan mentions along two specific reaches (portions
of Reach 1 and 2) were initially a concern, however, after another walk through of the site on
October 20th, DWR representatives believe that these transition areas are justified and care will
be taken to tie these cut areas into existing lower areas of the floodplain.
RESPONSE: While this cut is necessary for stream elevation tie-in, we will make every effort to
preserve adjacent wooded buffers.
5. DWR noted in the Mitigation Plan and in the field visits the many wetland pockets that the
Candy Creek project contains. While many of the wetlands on site are degraded, care should be
taken to minimize the impact of jurisdictional wetlands. DWR does recognize that much of the
stream work should enhance most of the wetland hydrology although a few wetlands will be
permanently impacted from the stream channel work.
RESPONSE: The design process did minimize wetland impact but some minor impacts were
unavoidable. We plan to flag and protect wetlands with safety fence to remain during
construction.
6. DWR recommends the removal of noted (in the Mitigation Plan and site visits) exotic
vegetation where practicable.
RESPONSE: The final construction documents will include a detailed exotic treatment plan.
7. Reach UT1C: The Mitigation Plan states Wildlands will be draining the pond but no details
were offered. For example,
a) What is the proposed construction sequence?
RESPONSE: The general sequence will be drawn down the pond as early as possible,
potentially requiring a temporary diversion channel which will need to be added to the
plans. Upon commencing restoration grading, the sequence will be to remove trees, clear
and grub, implement any final pumping down of the pond and the 300 linear foot portion of
stream below the dam, and then proceed to remove the dam and push the material into the
old pond bed. Fill material will be compacted to create the new valley grading depicted. The
final approach will be adjusted as necessary to work with sediment conditions present upon
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drawing down the pond. Once the valley grading is complete, the new channel will be cut
through the valley and over -excavation will be necessary to install grade control structures
proposed and riffles. The contractor will be required to target a forecasted dry weather
period during construction to complete this work, or to implement temporary grade control
and stabilization to protect completed work in the case of a rain event. This will be done
completely in the dry (i.e., the flow will be pumped around the pond).
b) What is the existing sediment level in the pond bottom?
RESPONSE: As shown on sheet 2.2.1 in the plan and profile views, the pond bottom elevation
is in the 753.5 to 755 foot contour range, with the pond embankment at approximately
759'. The exact depth of deposited sediment is unknown as survey grades are typically shot
to the refusal depth in the pond bottom. The saturated sediment in the pond bottom will
either be mixed with the dry fill from the dam or removed to an upland disposal site depicted
in our Erosion and Sediment Control Plan.
c) Will they will excavate sediment or will the stream be constructed within the sediment?
RESPONSE: As shown on sheet 2.2.1, the stream will be constructed by cutting existing
material from the pond bottom leaving the existing pond bottom grade fairly close to the
proposed top of bank. The approach will be adjusted as necessary to work with sediment
conditions present upon drawing down the pond. The saturated sediment in the pond
bottom will either be mixed with the dry fill from the dam or removed to an upland disposal
site depicted in our Erosion and Sediment Control Plan. This process has worked well at
several other like situations that have been completed on other projects.
While this was brought up as a question/concern in the 2014 IRT site visit for the pond on UT2,
and the Mitigation Plan addresses these questions for the UT2 pond, the Mitigation Plan does
not address any of these questions for this pond.
RESPONSE: The approach on UT1C pond will be similar to the approach described for UT2 pond as
detailed above.
8. The Mitigation Plan states that material from the excavated pond will be used to build up
stream UT1C. DWR has reservations about using sediment from the bottom of a pond to create
stable channel fill.
RESPONSE: The vast majority of available fill will be from the dam embankment, rather than from
the pond itself. Pond sediment will not be used as channel fill unless it is suitable and adequately
dewatered. Section 9.3 (page 43) in the revised mitigation plan clarifies the use of pond sediments
in fill situations.
9. The Mitigation Plan calls the design of UT1C to be a step -pool system but there appears to be a
lot of meander for a step -pool system. In addition, the grade appears to be held by constructed
riffles and if the area adjacent to the channel is unconsolidated sediments (if they aren't
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proposing to remove all sediment) then DWR believes the constructed riffles may not be
sufficient to keep the channel in place.
RESPONSE: UT1C has a sinuosity of 1.14, and the stream alignment is defined by the existing valley
shape and proposed valley grading, where applicable. Most of the proposed riffles are also
protected at their downstream terminus with a grade control structure which typically extends
two feet below the bed and has a footer which is protected by the next downstream header, as a
measure of grade control factor of safety. We agree that a primary risk is erosion of bank fill
material and cutting around grade control elements. To address this, as part of developing the
final plans, we are also adding the requirement that some of the grade control structures be
extended to the existing channel bottom and valley wall to prevent short-circuiting of grade
control elements. In addition, some of the log structures will be changed to rock to add robustness,
and some additional toe protection will be specified in meandering fill sections. Note that the
drainage is area is 15 acres and therefore high peak discharges will not occur through this reach.
10. Regarding UT2 Reach 1A, during the site visit on October 20th, discussions were held concerning
the best approach. Specifically, the planned approach was to cut a bench on this small incised
reach versus utilizing a modified in -stream structure approach to promote stability and to partially
fill the incised channel to raise the stream bed. DWR recommends that Wildlands consider an
alternative approach on this reach. If Wildlands pursues this change, the final mitigation plan
should provide an explanation as to how the structure will be monitored to ensure the restored
channel maintains at least intermittent flow. In the event that intermittent flow is discontinued
(e.g. conversion to an ephemeral, non -jurisdictional channel), the length of channel in which no
flow is occurring shall be considered a permanent stream impact and mitigation may be required
to compensate for the lost aquatic function.
RESPONSE: Wildlands considered partially raising the stream bed and the feasibility of a BMP such
as a step pool conveyance system. We think that both of these options will potentially discontinue
intermittent flow given that the base flow in the existing channel is fed by groundwater seep as
opposed to surface flow. Furthermore, the impact to the adjacent wooded area would not be
significantly different than the currently proposed approach. We still think that the current design
of keeping the bed at its existing elevation while stabilizing the banks is the optimum option.
11. Regarding UT2, UT2A, and UT213, DWR noted the extensive use of log sills in the preliminary plans
for these reaches. While DWR likes the purpose of log sills, we have noticed failure to hold grade
in other projects, especially when utilized in areas of higher slope. DWR recommends careful
supervision when these structures are installed.
RESPONSE: Wildlands will work with the contractor to ensure proper installation of the log sills. In
higher slope situations, footer logs are essential. This is reflected in the construction plan detail.
12. Regarding Reach 1A, DWR suggests that another cross-section be added along Reach 1A between
the two vegetation plots. DWR recalls this section as highly incised and clearly very erodible.
RESPONSE: The attached revised mitigation plan pages (section 12.1) and Figure 11b have been
revised to include an additional cross-section.
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13. Regarding Reach 413, Table 14b, Design Morphological Parameters, lists the range for the Meander
Width Ratio (MWR) of Reach 4B to have a range of 1.5 to 5. Typically most stream restoration
projects, particularly in streams with a 3 mi' drainage area, have a MWR of 3. Please explain the
reasoning for the lower end of range being 1.5.
RESPONSE: In Reach 48, between stations 199+00 and 201+50, there is a segment of the
restoration reach which follows the existing pattern of the stream to avoid disturbance of mature
floodplain vegetation and wetlands. The existing pattern through this segment is nearly straight
and has this lower Meander Width Ratio. The low end of the Meander Width Ratio range was
driven by this atypical situation, while the rest of Reach 4b falls more in line with an MWR of at
least 3.
Andrea Hughes, USACE, 23 November, 2015:
1. Please include the proposed plant list chart(s) in the text document.
RESPONSE: The revised plant lists are included in section 9.5.2 in the attached mitigation plan pages.
2. All intermittent stream channels proposed for restoration should document a minimum 30 days of
continuous flow on an annual basis.
RESPONSE: Section 11.1.5 was updated to include this criteria as shown in the attached mitigation
report pages.
3. Under Vegetation Performance Standards on page 54, the draft plan indicates that if planted stems
are at least 260 per acre, monitoring of the vegetation on the site may be terminated. Please note
that requirements for early termination of monitoring also include vigor, and Years 1-5 monitoring
should demonstrate no invasive species issues.
RESPONSE: Sections 11.0 and 11.2 were updated to include this criteria as shown in the attached
mitigation report pages.
4. Regarding the conservation easement (CE) in Appendix 1, please address the issues below:
a. Should the CE template be revised to show that DENR is now DEQ?
RESPONSE: DMS indicated in an email on November 30, 2015, that there was no need to
revise easement language since we have already closed on the property. Revising the CE
template for future projects is a programmatic issue and should be resolved directly with
DMS.
b. Page 5, Section L, Water Quality and Drainage Patterns, indicates water may be
temporarily withdrawn for good cause shown as needed for the survival of livestock on the
Property. This should require approval by the conservation easement holder and pumps
should be placed outside the easement boundary with temporary placement of pipes for
withdrawal.
RESPONSE: DMS indicated in an email on November 30, 2015, that there was no need to
revise easement language since we have already closed on the property.
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c. Page 5, Section O, Disturbance of Natural Features, indicates the Grantor may request
permission to vary from the CE restrictions for good cause shown. The intent of this
paragraph is to allow for activities that will benefit the ecological functions on the mitigation
site and supports the objectives of the mitigation plan. Please revise this section to clarify the
intent of this paragraph.
RESPONSE: DMS indicated in an email on November 30, 2015, that there was no need to
revise easement language since we have already closed on the property.
d. The survey plat indicates a 20 ft utility line crossing Candy Creek in two locations; a 10 ft utility
crossing in the buffer; and a drainage maintenance and utility easement that extends 50 feet
from top of bank (on both sides). The mitigation plan did not include any information
regarding these easements. Please provide additional information for these areas including
the intent for placement of an easement for each area (future utility line, etc.), the holder for
each easement area (utility company, county, municipality, etc.) and how these easements
will be addressed to ensure project success and sustainability.
RESPONSE: While multiple utility easements exist within the conservation easement and
across Candy Creek, no actual utility lines have been installed. All of the easements have been
subordinated to the conservation easement per the documents Shawn Wilkerson emailed to
Andrea Hughes and Todd Tugwell on November 23, 2015.
e. The survey plat indicates a reserved crossing of Reach 3 above its confluence with UT
1C. This crossing should be shown on Figure 10 a (concept design map) and details
provided in the text document.
RESPONSE: The attached figure 10a has been revised to show this crossing. Text has been
added to discuss the crossing types in Section 4.9.
f. The survey plat indicates a reserved crossing of UT 2 just below Reach 1 and before the
confluence with UT 2B. This crossing should be shown on Figure 10 a (concept design map)
and details provided in the text document.
RESPONSE: The attached figure 10b has been revised to show this crossing. Text has been
added to discuss the crossing types in Section 4.9.
g. The survey plat indicates a reserved crossing of UT 5 just before the confluence with
Candy Creek. This crossing should be shown on Figure 10 a (concept design map) and
details provided in the text document.
RESPONSE: The attached figure 10b has been revised to show this crossing. Text has been
added to discuss the crossing types in Section 4.9.
Please let me know if you have any additional questions.
Sincerely,
Aaron S. Earley, PE, CFM
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