20110251 Ver 1_More Info Received_20110509

?MCKIN4& CREED
TO: NCDENR
585 Waughtown St.
Winston-Salem, NC 27107-2241
ATTENTION: Sue Homewood
WE ARE SENDING: ? Originals ® Prints
? Specifications ? Calculations
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LETTER OF TRANSMITTAL
DATE: May 6, 2011
PROJECT NO: 5466,0003 TASK NO:
RE: Erosion Control Permit
TRANSMITTAL NO: PAGE 1 OF 1
? Shop Drawings ? Samples
? Other -
Quantity Drawing No. Rev. Description Status
2 Plan Sets G
1 Comment Letter i REC
N.C. Dent. of E'YP

G
MAY 0 9 V
itc

Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1. No Exceptions Taken 2. Make Corrections Noted 3. Other
4. Amend & Resubmit 5. Rejected - See Remarks
REMARKS: Please feel free to contact me if you have any questions.
8020 Tower Point Drive, Charlotte NC 28227 Tel: [phone] Fax: [phone]
cc:
McKIM & CREED, PA
Signed
Sherri L. Altizer
v MCKIM&CREED
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May 6, 2011
Ms. Sue Homewood
NCDENR
585 Waughtown Street
Winston-Salem, NC 27107
T - - RECEIVE[)
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MAY 0 9 2011
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ENGINEERS
S U R V E Y O R S
P L A N N E R S
RE: Section 401 Water Quality Certification Application for Distribution & Collection
Improvement & Stream Restoration
NCDENR DWQ# 11-0251
Dear Ms. Homewood,
This letter is in response to DWQ's comment letter dated April 14, 2011. Attached
you will find revisions and explanations listed for each comment. We've also
included two sets of plans for approval. Please inform us if you have any questions.
Sincerely,
McKim & Creed
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J. Michael Osborne, PE
8020 Tower Point Drive
Charlotte, NC 28227
704.841.2588
Fax [phone]
www.mckimcreed.com
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Response to DWQ's April 14, 2011 comments
1. Notes have been added to the plans to clarify planting within the utility right-of-
way. The typical note reads "STABILIZE AREAS DISTURBED WITHIN ROW WITH
SEEDING AND STRAW, SEE SHEET C16 FOR ACCEPTABLE SEED MIXES".
2. The step pool design was revised to clearly show the use of a large, flat, natural-
looking 'apex' stones which provide grade control between each step pool. The pools
need to be constructed of stone per the sizing shown on the plan set so that stones do
not move during events up to the 10-year storm. The pools are chinked with smaller
stone material at construction so that surface flow is kept above the stone for the
most part (rather than flowing beneath the stone, potentially washing the pools out)
and this gives a more visually appealing look immediately upon installation. The
cross sections at the control points (apexes) and maximum pool depth locations have
been sized to accommodate the channel-forming storms and be stable for events in
excess of the 10 year event. It has been our experience that these pools, when
properly constructed and chinked, are stable and accumulate sand, silt and clay
which supports plant growth. Please see plans, detail sheet C19 located in Phase 2, for
revised detail.
3. We agree with DWQ's opinion that the stream for project sites 11 and 12 are
unstable. The project is based on utility repair and protection and falls short of a
complete priority I design that would include several hundred feet of streamwork.
City/County Utilities (CCU) is working to eliminate the current problem, but due to
limited funding and jurisdiction CCU can not take responsibility for issues related to
storm water. Full restoration would fall under the City of Kernersville storm water
responsibilities.
Site 11
Conditions at this location are further exacerbated by nearly complete takeover by
invasive kudzu which provides very poor bank stabilization. Eradication of the
kudzu is cost prohibitive and may not be allowed on adjacent private land. Without
complete eradication and subsequent post-eradication treatments of the entire stream
valley, the kudzu will move back onto the project site. Given that no bioengineered
(vegetated) solution will endure due to the predatory nature of the kudzu, no
vegetation-dependent revetment was considered. Similarly, natural channel design
involving re-alignment (changes to plan, dimension and profile) was not considered
because installed vegetation (e.g., live stakes, seeding, installed bushes and trees)
would not survive. This left us with more structure-dependent methods. It is our best
engineering judgment that if the entire stream valley cannot by adequately restored
then the smallest armored solution (imbricated riprap in this case) should be
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pursued. This will not result in a long-term (several decade) solution but the utility
line at this location will be protected.
Grade control at Site 11 was not pursued due to the nature of the footer stones for the
imbricated riprap. Their purpose is to provide deep scour protection and to form a
pool at this outside meander. Although knick points may travel along this stream, it
is much more laterally unstable than vertically unstable and the installation of a
grade control(s) was not thought necessary. Should the pool depth or length shift
after construction, it will still bear against the stone.
Site 12
We believe that this site is much more vegetatively stable than site 11 and has a good
riparian plant community with no kudzu. The stream is unstable at this site but not to
the extent of site 11 and the erosion repair need is localized to the work as shown on
the plan set. Therefore a bioengineered bank stabilization (vegetated geolifts) is
appropriate at this location.
v McIGM&CREED