WQ0012948_More Information (Received)_20240919

Some people who received this message don't often get email from [e-mail]. Learn why this isimportant
From:Tim Sheehan
To:Anthony, Cord P
Subject:[External] RE: [UNOFFICIAL ADDITIONAL INFORMATION REQUEST] WQ0012948 - Pisgah Center for Wildlife
Education WWTF
Date:Thursday, September 19, 2024 2:51:01 PM
Attachments:image006.png
Sewer line capacity check calc.pdf
You don't often get email from [e-mail]. Learn why this is important
CAUTION: External email. Do not click links or open attachments unless verified. Report suspicious emails with the
Report Message button located on your Outlook menu bar on the Home tab.
Attached is the calculation to check the hydraulic capacity of the collection system for each
septic tank as requested per our phone call of last week. We are sorting out the O&M
manual as the subcontracted maintenance contractor is having difficulty producing the
existing manual. It would remain unchanged as there are no components or configurations
that have changed in the system other than the location of the two septic tanks.

Timothy Sheehan
Senior Project Engineer
McGill Associates, PA
712 Village Road SW, Suite 103, Shallotte, NC 28470T 910.755.5872D 910.363.2522C 704.443.1391
[e-mail]

From: Anthony, Cord P <[e-mail]>
Sent: Tuesday, September 10, 2024 11:52 AM
To: Ben Cathey <[e-mail]>; fmr.brad.kleinmaier
<[e-mail]>
Cc: Thornburg, Nathaniel <[e-mail]>; Natalie Croom
<[e-mail]>; Kemp, Melanie <[e-mail]>
Subject: [UNOFFICIAL ADDITIONAL INFORMATION REQUEST] WQ0012948 - Pisgah Center for
Wildlife Education WWTF

All,
After reviewing the submitted application, the Division requires the following item(s) to move
forward with the permitting process:
1. I was wondering if you could give insight into the overall treatment units/piping proposed for
the site. The previous permit issuance included three septic tanks (a 4,000 gal, a 2,000 gal,
and a 5,000 gal). Only two septic tanks, however, are shown in the current proposal (a 2,000
gal and 5,000 gal). Please explain why the 4,000 gal septic tank has been removed from the
design.

Additionally, the previous permit issuance did not depict a sewer line directly connected to
the previously permitted 4,000 gal septic tank. The proposed location for the 2,000 gal
septic tank replacement is in approximately the same location as the previously permitted
4,000 gal septic tank and is now shown to be directly connected to a sewer line. Please give
insight in whether this line existed prior to the current minor modification request and, if so,
evidence as to how a 2,000 gal septic tank will adequately handle the loading previously
allocated to a 4,000 gallon tank.

If the 4,000 gallon tank was mistakenly omitted from the plans, please submit an updated
plan set. Please also note that any change in location/geometry of treatment units and/or
sewer lines will require an up to date set of calculations for the system, signed and sealed by
the engineer ensuring that this modification will not adversely affect the capacity of the
system. An updated set of plans depicting where the 4,000 gallon septic is located would
also be required.

If the intent is to remove the 4,000 gallon septic tank completely, this would greatly impact
the treatment and flow regime of the system and constitute a major modification to the
system. At a minimum, the application submission would need to be updated to adequately
reflect the major modification and the major modification fee would need to be paid. If a
significant change to the facility is planned, our recommendation would be to rescind the
minor modification request and resubmit the project as a major modification once all
documentation is completed per Form: WWIS 06-16. Per our telecon, this tank was shown in
error. Brooks previous permit does not have this tank as part of collection system.

2. The response to the additional information requested on July 21, 2024 noted that an updated
O&M plan would be sent at earliest convenience. No O&M plan has been submitted yet.
Please provide this document. We are working with the O&M contractor to obtain this
document for the existing system. There will be no changes to the existing system equipment
or function.

3. My understanding is that the new EZ-Treat media filters were to take the place of the
previously permitted sand filters. I just wanted to double check that the sand filter dosing
pumps and two 1,500 sqft recirculating sand filters have been decommissioned and
abandoned prior to removing them from the permit. That is correct per my reading of Brooks’
previous permit submittal.

4. I also wanted to double check and see if a staff gauge has been installed in the surface
wetland cell?
Please keep in mind that this is currently an informal request for additional information, however,
the Division cannot issue the Final Permit without addressing the item(s) listed above. I will send a
formal Additional Information Request if the Division does not receive a response by September 23,
2024.
All revised and/or additional documentation shall be signed, sealed, and dated (where needed), with
an electronic response submitted in a single PDF as an email attachment (document size permitting)
or via the Non-Discharge online portal as “Additional Information”. Please do not resubmit
documentation that has no outstanding comments or revisions (i.e., manufacturer’s information,
product cut sheets, flow reduction request, etc.)
If you have any questions regarding this email, please contact me at your convenience.
Sincerely,
Cord Anthony
Engineer II
Division of Water Resources – Non-Discharge Branch
North Carolina Department of Environmental Quality
Office: [phone]
[e-mail]

Email correspondence to and from this address may be subject to the North Carolina Public Records Law and may be disclosed to third
parties by an authorized state official.
Bobby Setzer Fish Hatchery
Pisgah National Forest
Sewer Capacity check flowrate vs slope
Method:
Check if slope is sufficient at shallowest segment of collection headers to each septic tank to keep line
less than half full at peak hourly flow using peaking factor of 10X Average Daily Flow using Manning's
equation.
Septic Tank 1
Average Daily flow 1655 Gallons per day or 1.149 GPM
Peak hourly flow 11.5 GPM
Flow delivered in half full 4" Pipe using Mannings' equation
Q=(k/n)*((Rh)"2/3)*(s^1/2)*A
Where Q= flow rate in CFS
K=1.4859 for English units
N=.014 for ferrous pipe
Rh= Hydraulic diameter= Area/wetted permiter
S= minimum pipe slope for branch run
A= cross sectional area of wetted pipe= (3.14*r^2)/2 = 3.14*(2/12)^2 /2=.043 sq ft
Wetted perimeter=3.14*r= 3.14 *(2/12)=.52 ft
Rh=.043/.52=.082 ft
Minimum Slope is from manhole at station 13+80 to manhole at 14+70. Horizontal run is 90 feet and
vertical drop is 1.5 ft. S=1.5/90=.011
Q=(1.4859/.014)*((.082)^2/3)*((.011)n.5)*(.043) = .09 CFS or *40.3 GPM which is far in excess of 11.5
GPM. Line will not be % full. Collection system flow regime has adequate slope.
1
*10%srlo5@16,8040
irk A
mow• :. ' S S160.
4
LI°
~s r00
°O�t'7ii�Ee' v�a��

Septic Tank 2
Average Daily flow 1950 Gallons per day or 1.354 GPM
Peak hourly flow *13.54 GPM
Flow delivered in half full 8" Pipe using Mannings' equation/
Q=(k/n)*((Rh)^2/3)*(s^1/2)*A
Where Q= flow rate in CFS
K=1.4859 for English units
N=.014 for ferrous pipe
Rh= Hydraulic diameter= Area/wetted permiter
S= minimum pipe slope for branch run
A= cross sectional area of wetted pipe= (3.14*rA2)/2 = 3.14*(4/12)^2 /2=.174 sq ft
Wetted perimeter=3.14*r= 3.14 *(4/12)=.1.05 ft
Rh=.174/1.05=.165 ft
Minimum Slope is from Septic tank 2 at station 15+50 to manhole at 15+22. Horizontal run is 28 feet and
vertical drop is .5 ft. S=.5/28=.017 ft
Q=(1.4859/.014)*((.165)^2/3)*((.017)^.5)*(.174) = .55 CFS or 248 GPM which is far in excess of 13.54
GPM. Line will not be % full. Collection system flow regime has adequate slope.