20171523 Ver 1_SW Outfall Anaylsis Summary_20180227

Strickland, Bev
From:
Keith Rains <[e-mail]>
Sent:
Tuesday, February 27, 2018 2:42 PM
To:
Mcdaniel, Chonticha
Subject:
Re: [External] Uwharrie
Attachments:
Outfall Analysis Updated Summary.pdf
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Per our discussion, I have updated the Summary.
Keith Rains, PE
President
The Rains Group
803-493-5393
On Tue, Feb 27, 2018 at 12:17 PM, Mcdaniel, Chonticha <[e-mail]> wrote:
Keith,
I see your point, maybe I didn't ask the right question. I was looking for the information on the current size (flow) of the
stream but again maybe we don't need it. Let me talk to Sue and we will get back with you. Thanks!
Chonticha McDaniel
401 Stormwater Engineer
401 & Buffer Permitting Branch
Division of Water Resources
Department of Environmental Quality
919-807-6379 office
chonticha.mcdaniel(a-)ncdenr.gov
Mailing Address - 1617 Mail Service Center, Raleigh, North Carolina, 27699-1617
1

Street Address - 512 N. Salisbury St, Raleigh, North Carolina, 27604
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From: Keith Rains [mailto:[e-mail]]
Sent: Tuesday, February 27, 2018 11:52 AM
To: Mcdaniel, Chonticha <[e-mail]>
Cc: Homewood, Sue <[e-mail]>
Subject: Re: [External] Uwharrie
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The cross-sections used for the calculations are representative of a typical section within that stream.
D. KEITH RAINS, PE
THE RAINS GROUP. LLC
803-493-5393
On Feb 27, 2018, at 11:44 AM, Mcdaniel, Chonticha <[e-mail]> wrote:
Keith,
Thank you for the additional calculations. However, I still don't see a discussion and comparison
between the current size/condition of the receiving stream and the proposed discharge
volume/velocity from each discharging point (that go directly into the stream). The receiving stream
appears to be small, so, we need to ensure that it won't get blown out by these stormwater outfalls.

Chonticha McDaniel
401 Stormwater Engineer
401 & Buffer Permitting Branch
Division of Water Resources
Department of Environmental Quality
919-807-6379 office
chonticha.mcdaniel(cDncdenr.aov
Mailing Address - 1617 Mail Service Center, Raleigh, North Carolina, 27699-1617
Street Address - 512 N. Salisbury St. Raleiah. North Carolina. 27604
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Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.
From: Keith Rains [mailto:[e-mail]]
Sent: Tuesday, February 27, 2018 11:07 AM
To: Mcdaniel, Chonticha <[e-mail]>
Subject: [External] Uwharrie
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t to Report Spam.
Ms. McDaniel:
3

Hope you are doing well. The enclosed are the outfall calculations with resulting velocities to the
downstream receiving streams and natural low areas. Please let me know if there is anything else
needed. We are anxious to get this project wrapped up.
Keith Rains, PE
President
The Rains Group
803-493-5393

F--]
IHS
)Ur Outfall Analysis Summary
for
Uwharrie Charter Middle School
(The Rains Group: #2017-100)
OUTFALL SUMMARY
The following is a summary of the outfall analysis for velocities as requested.
Outfall FES #35 — Q 10 = 24.68 cfs
• Level spreader provided at outfall
• Outfall discharges into a vegetated filter strip that travels nearly 150' in the natural low
area until it reaches the JD wetlands. The stormwater travels another 600+ feet through
the vegetated wetlands before it leaves our property.
• Modeled as a V -channel with a roughness coefficient of n= 0.70 (See included chart)
• Resulting velocity is 1.48 ft/s
• Picture #4 & #5 Show existing temporary outfall into sediment trap as well as the
vegetated strip that the final flow will travel through.
Outfall FES #55 — 010 = 20.54 cfs
• Rip -Rap Apron provided at outfall for dispersion of flow
• Outfall discharges into stream (See Pictures 4144 for typical section)
• Modeled as a trapezoidal channel with a roughness coefficient of n=0.040
• Resulting velocity is 3.23 ft/s
Outfall FES #63 — 010 = 37.49 cfs
• Rip -Rap Apron provided at outfall for dispersion of flow
• Outfall discharges into stream (See Pictures #144 for typical section)
• Modeled as a trapezoidal channel with a roughness coefficient of n=0.040
• Resulting velocity is 3.80 ft/s
Outfall FES #67 — Q 10 = 1.27 cfs
• Rip -Rap Apron provided at outfall for dispersion of flow
• Outfall discharges into stream (See Pictures #1-#4 for typical section)
• Modeled as a trapezoidal channel with a roughness coefficient of n=0.040
• Resulting velocity is 1.31 ft/s
Cross -culvert FES #70 — Q10 = 52.41 cfs

• Existing channel/stream flow. No new flow is being added to this crossing from the site
improvements
• Rip -Rap Apron provided at outfall for dispersion of flow
• Outfall discharges into stream (See Pictures #144 for typical section)
• Modeled as a trapezoidal channel with a roughness coefficient of 11=0.040
• Resulting velocity is 4.15 ft/s
The creek cross-sections used for the analysis was an average cross-section based on field
measurements by the site contractor. Some areas of the creek are smaller/shallower than other
areas, however, since the velocities were relatively low, based on my professional opinion, there
will be no erosive conditions or overtopping of the existing creeks due to this site development.
In addition, this creek continues to the adjacent southern site that is owned by the same entity as
this site and continues almost 1500 LF before it crosses into the public R/W at US HWY
220/Interstate 73/74. Based on this analysis, this site should be considered a Low Impact
Development.
If you should have any questions please feel fi•ee to call me @ 803-493-5393.
Sincerely,
The Rains Group, LLC
026153
D. Keith Rains, PE �•;;,n�ZG. I
Summa