SW1190901_Emails_20200225

Farkas, Jim J
From:Farkas, Jim J
Sent:Tuesday, February 25, 2020 9:24 AM
To:Dave Skurky
Subject:RE: \[External\] RE: Asheville Regional Airport Parking Lot A - SW1190901
Attachments:Ashville Airport Drainage.PNG
Dave,

What you have looks good. I have one question though, where does the area outlined in green (See attached) drain to?
Based on the contours, it appears to drain to A3.4. Please update the drainage areas on the plan sheet and calculations if
needed.

Aside from that, everything else looks good, just don’t forget to sign & seal the calculations and get the O&M form
signed and notarized (Since the swale table sheet of the Supplement-EZ Form is such a minor change, you don’t need to
re-sign and seal the Supplement-EZ Form, just provide the corrected sheet).

-Jim

From: Dave Skurky <[e-mail]>
Sent: Monday, February 24, 2020 11:01 AM
To: Farkas, Jim J <[e-mail]>
Subject: RE: \[External\] RE: Asheville Regional Airport Parking Lot A - SW1190901

CAUTION: External email. Do not click links or open attachments unless you verify. Send all suspicious email as an attachment to
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Jim,
If you have a few moments, can you flip through to ensure these are all good with you (its pretty much just Appendix F,
the Supplemental EZ and then the SW-01 sheet)? If so, we’ll get signed notarized and the complete submittal back into
you. Thanks!

From: Farkas, Jim J <[e-mail]>
Sent: Tuesday, February 18, 2020 2:48 PM
To: Dave Skurky <[e-mail]>
Subject: RE: \[External\] RE: Asheville Regional Airport Parking Lot A - SW1190901

Dave,

Correct, unless you cannot (or choose not to) meet all of the design requirements in 15A NCAC 2H .1003(2)(d)(i-v).

15A NCAC 2H .1003(2)(d)(vi) allows for the use of the design criteria listed in 15A NCAC 2H .1061 to be used instead of
(not in addition to) 15A NCAC 2H .1003(2)(d)(i-v).

You may use either design standard, but you do not need to meet both.

-Jim
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From: Dave Skurky <[e-mail]>
Sent: Tuesday, February 18, 2020 2:42 PM
To: Farkas, Jim J <[e-mail]>
Subject: \[External\] RE: Asheville Regional Airport Parking Lot A - SW1190901

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Jim,
Thank you.

On this comment:
o NOTE: The 6 inch max depth of flow and minimum 4 minute detention time during the 0.75 in/hr storm
are only required if 15A NCAC 2H .1061 is being used in lieu of 15A NCAC 2H .1003(2)(d) for the swale
design. If you are doing this, please let me know ASAP.

I’m a little confused. Should we just not show the 6 inch max depth of flow and 4 minute detention time?

From: Farkas, Jim J <[e-mail]>
Sent: Tuesday, February 18, 2020 1:16 PM
To: Dave Skurky <[e-mail]>
Subject: Asheville Regional Airport Parking Lot A - SW1190901

Dave,

I was looking over the additional information you provided on 1/28/2020. Everything looks good except for a few small
issues:

Please correct the following:
- Please provide swale calculations showing that the 10-year storm event is passed non-erosively. Since this is a
compound swale, the swale must be broken down into individual segments for the calculations (You may keep
the swale as a single swale for the O&M Agreement and Supplement-EZ Form since it is just 1 swale, but must
be broken up for calculations). I have attached a very crude representation of what I am looking for calculation-
wise (The numbers are loosely based on the submittal although I made up some values for illustrative purposes).
The calculations should include:
o A diagram, similar to the one provided for the pipe network, showing the individual segments of the
swale and where the curb cuts feed into the swale (Just so there is no confusion about which
calculations go with which swale segments).
o A table showing all of the pertinent design criteria of the swale segments (You could also provide
longhand calculations showing all of this information if you rather):
 Length
 Flow (10-year storm)
 Bottom width
 Depth of flow (10-year storm)
 Cross-sectional area, wetted perimeter, & hydraulic radius (10-year storm)
 Manning$B!G(Js n value (if this value is the same for all of the swales, you can put a note under
the table or in the calculations stating the n vale used)
 Side & longitudinal slopes (if either value is the same for all of the swales, you can put a note
under the table or in the calculations stating the slope used)
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 Velocity (10-year storm)
 Maximum allowable velocity (if this value is the same for all of the swales, you can put a note
under the table stating the maximum allowable velocity)
o Calculations. Show the equations used to get the values in the table (cross-sectional area, wetted
perimeter, hydraulic radius, velocity, duration, etc$B!D(J).
o A table showing the length of flow from curb cut to outlet.
NOTE: In order to meet the design standard set forth in 15A NCAC 2H .1003(2)(d):
o Each segment of the swale must be able to carry the 10-year storm at a non-erosive velocity.
o Each segment of the swale has a slope of 5% or less*.
o Each segment of the swale has a minimum bottom width of 2 feet.
o Each segment of the swale has a side slope of 3:1 or flatter.
o Each flow length from curb cut to outlet must be greater than 100 feet.
o NOTE: The 6 inch max depth of flow and minimum 4 minute detention time during the 0.75 in/hr storm
are only required if 15A NCAC 2H .1061 is being used in lieu of 15A NCAC 2H .1003(2)(d) for the swale
design. If you are doing this, please let me know ASAP.
- The provided lengths of vegetated conveyance provided in Table 3 of the stormwater management report do
not appear to match the plans (Please refer to the attached photo showing the approximate length of flow
through the vegetated swale from A3.2 to the rock dam as approximately 80 feet). The riprap energy dissipators
used to convey stormwater from the curb cuts to the vegetated swale does not count toward the requisite 100
ft flow length. Please revise.
- The drainage areas to the curb cuts, as shown in Table 3 of the stormwater management report do not add up
to the total drainage area as shown on the Supplement-EZ Form (0.51 + 0.50 + 0.44 + 0.10 = 1.55 $B!b(J 1.52.
Please revise for consistency.
- In the swale information of the Supplement-EZ Form, both the pervious area and impervious area draining to
the swale are shown as 1.52 acres. These two values should add up to the total drainage area. Please revise.
- Please show the drainage areas to the swale and level spreader on the plans (Section VI, 8o).

It is also recommended that the O&M form be updated to include the level spreader since if it is not maintained, the
project may become in violation of the permit (since dispersed flow may not be maintained).

Please provide the following:
- Swale calculations: 1x original signed & sealed hard copy and 1x electronic copy uploaded to Laserfishce.
- Supplement-EZ Form: 1x original signed & sealed hard copy of the cover page, 1x hard copy of the cover page,
2x copies of the corrected sheet(s), and 1x full electronic copy uploaded to Laserfishce.
- Stormwater management report: 1x hard copy and 1x electronic copy uploaded to Laserfishce (If applicable).
- Plan sheets: 2x hard copies of corrected sheets and 1x full electronic copy of the plan set uploaded to
Laserfishce.
- Title sheet: 2x hard copies (indicating the 1/28/2020 and any subsequent revisions) and 1x full electronic copy of
the plan set uploaded to Laserfishce.
- Boundary survey (as noted in response to comment letter on 1/28/2020): 1x hard copy and 1x electronic copy
uploaded to Laserfishce.

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 another formal 30-45 day review.

Let me know if you have any questions.

Jim Farkas
Environmental Engineer
North Carolina Department of Environmental Quality
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Division of Energy, Mineral, & Land Resources – Stormwater Program

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