SW4070701_Responce to Comments_20200227

Chris Brown
To: Farkas, Jim J
Cc: J Meliski
Subject: RE: Echota IV SW4070701
Good Afternoon Jim,
I have revised our calculations and related drawings per your comments below. See my written responses in red below.
I have uploaded the required items to the Laserfiche site, attached them in this e-mail and the original signed sealed
documents will go out in overnight Fed Ex today.
Thank you for directing your comments directly to McGill so that we were able to turn these responses around in a
timely manner.
Chris
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Christine Brown, CPSWQ, CPESC
Engineering Technician III
McGill Associates, P.A.
1240 1911, Street Lane NW, Hickory, NC 28601
T 828.328-2024
C 828.234-2044
Chris. Brown na mcaillassociates.com
rncgillassociates.com
We launched a refreshed brand. Please note email / web address changes above.
From: Farkas, Jim J <[e-mail]>
Sent: Wednesday, February 26, 2020 9:16 AM
To: Chris Brown <Chris.Brown@ mcgillassociates.com>
Cc: J Meliski<[e-mail]>
Subject: Echota IV SW4070701
Chris,
I was looking over the additional information you provided on 2/17/2020. Everything looks good except for a few small
issues:
Please correct the following:
Clearly indicate on the plans which typical section applies to each Swale. For example, swale 3, is shown to use
the typical section for the v-ditch and also the drainage swale w/ 6" riprap while others, such as swale 12, do not
have a listed typical section associated with them. All the swales are now listed at each corresponding detail. I
have also added a note on the Grading Plan.
2) Please show or clarify in the calculations why certain swales use a Manning's roughness coefficient of 0.035 and
others use 0.104. Please provide a reference of some sort if using the 0.104 roughness coefficient. The rip-

rapped swales used a different manning's n than the vegetative swales. Clarification has been shown on the
calculation sheet and also on a provided reference.
3) Since the proposed side slopes of the vegetated conveyances are 2:1, please provide calculations showing
stability of the channels during a 10-year storm. Please also indicate the method used to calculate the actual
shear stress and provide a reference for the maximum allowable shear stress used. Several of the swale
configurations have been changed to 3:1 side slopes, some remain at 2:1. 1 have attached the shear stress
calculation sheet and used the 10-year storm for all the swales. I referenced the calculation used to calculate
the shear stress at the bottom of the sheet. I have also attached a reference for the maximum allowable
shear stress.
4) Please sign & seal the calculations. The calculations now have a revised signed sealed cover sheet.
5) Please review the calculations for accuracy. For example, swale 9 appears to receive flow from swales 6, 7, & 8
(flow rates of 1.4 cfs, 0.7 cfs, & 0.8 cfs respectively). The flow reported for swale 9 (1.1 cfs) is less than the sum
of the flow of the contributing swales. Please clearly indicate in the calculations which swales flow into each
other and ensure that the calculations are correct. Additional information has been added in the first column
of the swale calculation sheet. The swales have been reviewed for accuracy and some needed revisions have
been made.
While not required, it is recommended that, where possible, riprap lined swales be avoided as they are not considered
vegetated conveyances. Swale 6 has now been calculated as Swale 6a and Swale 6b, since the beginning portion was
able to be a vegetative swale with some adjustments.
Please provide the following:
- 2x hard copies and 1 x electronic copy uploaded to Laserfiche of the applicable updated plan sheets.
- 2x hard copies and 1 x electronic copy uploaded to Laserfiche of the title sheet indicating the revisions to the
plan set.
- 1x hard copy of the corrected swale calculations or 1x response to comments explanation for using the different
Manning's n values.
- 1x hard copy of the swale shear calculations for the 10-year storm.
- 1x original, signed hard copy of the calculation coversheet.
- 1x electronic copy uploaded to Laserfiche of the full, corrected calculations.
Since these are really minor things, once I get the hard copies, anything else that may have changed from addressing
these issues, and the documents are uploaded to Laserfiche (Provided everything is still in order), we can issue the
permit without doing a formal 30-45 day review.
Let me know if you have any questions.
Jim Farkas
Environmental Engineer
North Carolina Department of Environmental Quality
Division of Energy, Mineral, & Land Resources — Storrnwater Program
512 N. Salisbury Street
1612 Mail Service Center
Raleigh, NC 27699-1612
[phone]
Jiin. Farkas gncdenr. oovv