WQ0019755_More Information Received_20220420

Initial Review
Reviewer
Thornburg, Nathaniel D
Is this submittal an application? (Excluding additional information.) *
Yes No
If not an application what is the submittal type?* Annual Report
Residual Annual Report
Additional Information
Other
Permit Number (IR) * WQ0019755
Applicant/Permittee JPC Utilities LLC
Email Notifications
...............................................................................
Does this need review by the hydrogeologist? * Yes No
Regional Office
CO Reviewer
Admin Reviewer

Submittal Form
Project Contact Information
Please provide information on the person to be contacted by NDB Staff regarding electronic submittal, confirmation of receipt, and other correspondence.
............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Name* John F. Phillips
Email Address*
[e-mail]
Project Information
Application/Document Type*
New (Fee Required)
Modification - Major (Fee Required)
Renewal with Major Modification (Fee
Required)
Annual Report
Additional Information
Other
Phone Number*
919-467-9972
Modification - Minor
Renewal
GW-59, NDMR, NDMLR, NDAR-1,
N DAR-2
Residual Annual Report
Change of Ownership
We no longer accept these monitoring reports through this portal. Please click on the link below and it will take you to the correct form.
hftps://edocs.deq.nc.gov/Forms/NonDischarge_Monitoring_Report
Perm it Type:*
Wastewater Irrigation
High -Rate Infiltration
Other Wastewater
Reclaimed Water
Closed -Loop Recycle
Residuals
Single -Family Residence Wastewater
Other
Irrigation
Permit Number: *
WQ0019755
Has Current Existing permit number
Applicant/Permittee Address*
PO Box 345, Oak Ridge, NC 27310
Facility Name*
Oak Ridge Commons WWTP
Please provide comments/notes on your current submittal below.
This submittal is in response to Poorva Mokashi's March 18, 2022 Additional Information
Request for the proposed permit modification.
At this time, paper copies are no longer required. If you have any questions about what is required, please contact Nathaniel Thornburg
at [e-mail].
Please attach all information required or requested for this submittal to be reviewed here.
(Application Form, Engineering Plans, Specifications, Calculations, Etc.)
Response to Additional Information Request
334.94KB
WQ0019755.pdf
Upload only 1 PDF document (less than 250 MB). Multiple documents must be combined into one PDF file unless file is larger
than upload limit.
* By checking this box, I acknowledge that I understand the application will not be
accepted for pre -review until the fee (if required) has been received by the Non -
Discharge Branch. Application fees must be submitted by check or money order and
made payable to the North Carolina Department of Environmental Quality (NCDEQ).
I also confirm that the uploaded document is a single PDF with all parts of the
application in correct order (as specified by the application).
Mail payment to:
NCDEQ — Division of Water Resources
Attn: Non -Discharge Branch
1617 Mail Service Center
Raleigh, NC 27699-1617
Signature

Submission Date 4/20/2022

DIEHL & PHILLIPS, P.A.
CONSULTING ENGINEERS
1500 Piney Plains Rd., Suite 200
Cary, North Carolina 27518
Telephone [phone] — Fax [phone]
April 19, 2022
Poorva Mokashi, Engineer I
Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699
Re: Additional Information Request for
Permit No. WQOO19755 Modification Request
Oak Ridge Commons WWTP
Ms. Mokashi:
WILLIAM C. DIEHL, P.E.
JOHN F. PHILLIPS, P.E.
ALAN R. KEITH, P.E.
On behalf of JPC Utilities, LLC, we offer the following responses to your request for
additional information. The responses are provided in the order of your comments.
A. Cover Letter: Every tertiary filter, whether a granular media or a cloth media filter,
is subject to a solids overloading if there is an upstream process upset that causes the
clarifiers to discharge a high solids effluent. When this does happen, the filters respond
by backwashing more frequently, which returns backwash water to the head of the
plant more frequently, which increases the effective flow rate through the plant, which
exacerbates the clarifier upset. This situation can progress to the point where the filters
can't backwash because they can't filter enough water into the clearwell for the controls
to allow a backwash to be initiated. At that point the blinded filters will fill to the point
of overflowing the backwash troughs, and the mudwell pumps will be returning 100%
of the plant flow to the head of the plant. There would be essentially no flow through
the blinded filters, and the result would be an overflow of the plant and/or filters and a
sewer spill.
For this reason it is relatively standard for granular media filters and cloth media disc
filters to have a controlled overflow/bypass if the filters become blinded. It is my
opinion that the cited rule is intended to prohibit bypasses or overflows that would
result in permit violations. The filter bypass pipe at Oak Ridge only passes flows if the
water level in the filter cells has reached an abnormally high level due to blinding. The
bypassed flow is still chlorinated, and still passes through the chlorine contact chamber.
If the bypassed flow has a solids content that would inhibit the effectiveness of the
chlorine, the turbidimeter would detect a turbidity > 10 NTU and the effluent would

Poorva Mokashi
April 19, 2022
Page 2 of 6
automatically be directed away from the reclaimed water storage pond and instead
directed to the wastewater irrigation system storage pond.
When the Regional Office observed this pipe addition, their direction to the Permittee
was to request a permit modification to reflect this addition, not to remove it. On behalf
of the Permitted, we request the Division allow this operational aid to remain in place.
B. and C.: — No comments
D. Engineering Plans:
1. The sludge holding tanks in the 30,000 gpd reclaim water treatment plant were
designed and permitted to accept the waste solids from the treatment processes, which
includes the solids in the filter backwash water. The added connection from the
mudwell pumps to the sludge holding tank was made by the operator to provide the
option of discharging the backwash water directly into the sludge holding tank, rather
than adding the backwash water back into the treatment process via the equalization
basin. The operator only diverts backwash flows to the sludge holding tank if the flow
equalization tank is at a high level, to prevent the backwash flow from causing a surge
in the influent flow rate into the treatment plant. The solids in the backwash water do
not represent an increase in the solids that are wasted to the sludge holding tank.
The 14,000 gallon septic tank is part of the permitted 6,000 gpd wastewater treatment
system that was designed for an influent wastewater with a BOD5 concentration of 600
mg/I and a total suspended solids concentration of 300 mg/I. The only flow that is going
to this system now is the periodic discharge of the filter backwash water from the
30,000 gpd reclaim treatment system. If the filters receive clarifier effluent with a TSS
concentration of 20 mg/I, and if the 30,000 gpd treatment plant is operating at full
capacity, there would be a total of 5 pounds of solids applied to the filters. The typical
filter removal efficiency is 75%, which equates to a total of 3.75 pounds of solids per
day in the backwash water. The two filters typically backwash an average of once a
day, with a volume of approximately 800 gallons for each filter backwash. If all the
backwash water was directed to the 6,000 gpd treatment system, the loading would be
3.75 pounds of solids in 1,600 gallons of water. The 6,000 gpd treatment system was
designed for a flow of up to 6,000 gpd with a TSS concentration of 300 mg/I, or 15
pounds per day. The 6,000 gpd treatment system therefore is sufficiently sized to
accept as many as 7 to 8 filter backwashes a day, although there are normally two or
less backwashes in a 24 hour period. In addition to the septic tank, the 6,000 gpd
treatment system includes a recirculating sand filter, which provides additional solids
removal capabilities.
The plans for the sludge holding tank and the 14,000 gallon septic tank were included
in the submittal for this permit modification request. The demonstration of their
adequacy is presented in the narrative above.

Poorva Mokashi
April 19, 2022
Page 3 of 6
2. Please see the response under A. Cover Letter.
E. Engineering Calculations:
1. See the attached calculations.
2. The 6,000 GPD wastewater treatment system is designed for a wastewater with
influent characteristics that are more than double the organic loading of domestic
wastewater. The only flow received by the 6,000 gpd wastewater treatment system is
the filter backwash water, when the operator elects to direct the backwash water to
that treatment system. The operator will normally direct the filter backwash to the flow
equalization basin, unless that basin is at a relatively high level due to influent flows.
Please remember that the 30,000 gpd reclaim treatment plant was designed and
permitted with duplex submersible pumps in the flow equalization basin that have the
sole function of transferring wastewater from the flow equalization basin to the 6,000
gpd treatment system. There is a force main from these pumps to the influent of the
6,000 gpd treatment system; this force main was also included in the original design of
the reclaim treatment system. The operator has always had the option of transferring
up to 6,000 gpd of wastewater from the 30,000 gpd reclaim plant to the 6,000 gpd
treatment system.
By adding a second force main from the filter backwash pumps to the 6,000 gpd
treatment system, the operator is accomplishing the same objective as intended by the
original design, i.e., diverting up to 6,000 gpd of wastewater from the reclaim plant to
the 6,000 gpd wastewater treatment plant. The difference is that the diverted water is
only filter backwash water that has undergone BOD5 reduction in the reclaim plant and
may have a solids concentration of 250-400 mg/I. The permitted 6,000 gpd treatment
system was designed for a wastewater with a BOD5 concentration of 600 mg/I and a
TSS concentration of 300 mg/I. The filter backwash being diverted to this system has a
similar solids concentration, a lower BOD5 concentration, and a lesser flow volume;
therefore, the system is adequate to provide treatment of the filter backwash.
The quarterly sampling for the 6,000 gpd wastewater treatment system for 2021
indicated the following average effluent characteristics:
BOD5 31.8 mg/I
TSS 45/100 ml (geometric mean)
NH3-N 0.98 mg/I
TN 14.5 mg/I
TP 1.8 mg/I

Poorva Mokashi
April 19, 2022
Page 4 of 6
The effluent sample testing results were uneven. Some of this may be attributed to the
recirculating sand filter; as an open filter it will pass all the rainwater that falls into it
into the wastewater treatment system. Even with the variation in the quarterly testing
results, the annual average results generally indicate a secondary level of treatment
was achieved. Given there are no concentration limits for the effluent from the 6,000
gpd treatment system in the permit, given that an average secondary level of treatment
is being achieved, and given that the flows through this system are less than the
permitted 6,000 gpd, this treatment system is adequate, in my professional opinion, to
continue treating the filter backwash waters that the operator may elect to direct to the
6,000 gpd system.
3. As noted previously, the solids in the filter backwash water will ultimately end up in
the sludge holding tank if the backwash waters are returned to the flow equalization
basin. If the operator elects to direct the backwash water into the sludge holding tank
rather that the equalization basin, this does not represent additional flow or additional
solids loading to the sludge holding tank. If the operator elects to divert some of the
filter backwash waters to the 6,000 gpd treatment system, the solids loading of the
sludge holding tank would be decreased from what it would be if the backwash waters
were returned to the reclaim treatment plant.
F. Operation and Maintenance Plan: The plans submitted with this application
included a drawing that provided a key for the added valves and a description of the
required valve operations to direct the backwash wastewaters to the equalization basin,
the sludge holding tank, or the 6,000 gpd treatment system.
G. Specifications:
The adequacy of the referenced tanks has been demonstrated in the narratives above.
The original submittals for the permitting of these systems included the specifications
for these tank, which were obviously installed a number of years ago.
H. Additional Documentation:
1. This is one beneficial aspect that has resulted from this review. The flow meter that
was added measures the water that is automatically diverted away from the reclaim
storage pond due to the effluent turbidity exceeding 10 NTU. When the turbidity falls
back to 8 NTU, the effluent is automatically diverted back to the reclaim storage pond.
A review of the daily turbidity readings for 2021 indicate an average turbidity of 0.82
NTU, with no daily maximums exceeding 5 NTU. While there may possibly have been
some high turbidity readings occur between the recording of the daily turbidity values,
the flow through the installed flow meter should have been minimal. Your comment
prompted the operator to check the flow meter (Palmer Bowlus flume with an ultrasonic
transducer). He discovered the flowmeter was recording approximately 3 to 4 gallons

Poorva Mokashi
April 19, 2022
Page 5 of 6
per minute of flow with no actual flow passing through the flume. He has contacted the
authorized technician to diagnose the problem and to re -calibrate the meter. We will
report the results of that investigation when we have that information. At this point we
can only state that the reported flows for PPI 002 have been substantially and
incorrectly inflated due to this meter error.
A related problem is Condition 1.1 of the current permit creates some flow reporting
inaccuracies. The Condition directs the flow from the new flow meter to be added
(`included"� with the flow recorded on the flowmeter for the 6,000 gpd wastewater
treatment system. This method gives a false indication of the actual flow treated by the
6,000 gpd system. The flow measured by the new flow meter goes directly to the
wastewater irrigation pond, and does not pass through the 6,000 gpd treatment
system. The combining of the flow measurements from these two flow meters, in
conjunction with the new flow meter giving erroneously high totals, gives an incorrect
and inflated calculation of the actual flow through the 6,000 gpd wastewater system.
A second problem with Condition 1.1 is that it would lead to double -counting some of
the flow. If the reclaim plant has a high turbidity event and flow is diverted to the
wastewater irrigation pond, that flow will first be measured and recorded at the reclaim
plant flow meter. The same flow would then be measured and reported again as it
passes through the new flow meter. The permit language should be modified, in my
opinion, to have a PPI 003 added, to report the volume of the high turbidity diversions
to the wastewater storage pond, and to direct the operator to deduct that volume from
the flow measured by the reclaim treatment plant flow meter.
In summary, and in response to your comment, there were not high volumes of water
diverted to the wastewater storage pond or to the 6,000 gpd treatment system in 2021.
The incorrect flow data from the new flow meter created an inaccurate picture of what
actually took place in 2021.
2. There are no specific volumes that can be given for the diversions. As stated
previously, the operator can divert up to 6,000 gpd from the reclaim system to the
6,000 gpd treatment system. Under the current permit this diversion can be made with
raw wastewater plus backwash waters from the equalization basin of the reclaim plant;
the proposed permit modification would allow the operator to divert backwash waters
directly, rather than mixing them with raw wastewaters in the equalization basin.
The possible diversion of backwash waters into the sludge holding tank is not an
additional loading of the sludge holding tank, as previously explained.
3. The first sentence of this comment is unclear to me — ""Although permitted under the
same permit, the 30,000 gpd reclaimed water generation system and the 6,000 gpd
wastewater irrigation system have been permitted separately." However, I can confirm

Poorva Mokashi
April 19, 2022
Page 6 of 6
the pipe from the mudwell is connected into the influent pipe to the 14,000 gallon
septic tank. The solids are not overloading the treatment system. The operator elected
to raise the pumps to minimize the possibility of the pumps intaking any solids that
might migrate from the septic tank into the dosing tank, or that might be in the filtrate
returned from the recirculating sand filters. It is a relatively common practice to elevate
submersible pumps in pump tanks/dosing tanks.
As demonstrated by the 2021 data the performance of this treatment system, it is not
being adversely affected by the filter backwash water or the raised pumps.
The modifications that were made to the system were made under an incorrect
assumption that the changes were minor operational improvements that did not require
a modification of the permit. However, I don't want this oversight by the Permittee or
me to obscure the fact that the modifications made to the filters and the backwash
discharge piping were made with the intention of improving the plant performance. The
NDMRs for 2021 confirm this is a well operated system that is consistently producing a
quality reclaim effluent.
Please let me know if you require any further information to approve this permit
modification.
�0.�FESSIpy. /� s
SEAL 9` =
10130 =
,goy`LNG! �vE�
Attachment
Cc: Mr. Philip Cooke
Mr. Doug Smith
Mr. Nathaniel Thornburg
Mr. Lon Snider, WSRO
Ms. Caitlin Caudle, WSRO
Yours very truly,
Diehl & Phillips, P.A.
r� - T rjd4- W
John F. Phillips, P.E.

Filter Calculations - Oak Ridge Commons WWTP
Headloss through clean filter
hf/L = J(v/9)((1-E)Z-E3)(V)(6=(LPdp)Z
hf/L = head loss in depth of bed L
J = dimensionless Kozeny constant with a typical
value of 5 for sand
v=
g=
E=
dp =
L_
1TM
kinematic viscosity
1.41E-05 SF/sec at 50 deg F
8.64E-06 SF/sec at 86 deg F
32.2 ft/sec-sec (acceleration of gravity)
� � r
S b
+r i :7 AI 7T • r
0.4 porosity
Effective size of sand = 1.91 mm = 0.00627 feet
sphericity = use 0.80 for sharp angular sand
(note - Shape factor = 6/LP )
superficial approach velocity, in feet/second
Filter cell area = 4' x2.67'= 10.68 square feet
30000 gpd/10.68 SF/2 cells/1440 min/day =
0.98 gpm/sf = 0.0022 feet/second
hf/L = J(v/g)((1-E)^2/EA3)xVx(6/(LPdp)^2
hf/L = 5(1.41E-05/32.2)((1-0.4)2_0.43)(0.0022)(5/(0.8*0.0063))2
hf/L = 0.0384 with clean filter at 500 (10°C)
For 3 foot media depth, hf = 3*0.0384 = 0.115 feet headloss with clean
filter at 500 (10°C)
Similarly, hf/L = 0.0235 with clean filter at 860 (30°C)
hf = 0.071 feet headloss with clean filter at 860 (30°C)
The WEF Manual of Practice No. 8 presents a graph, based on operating data from various
wastewater treatment plants, that shows the solids storage capabilities of filter medias of
varying effective sizes at increasing headlosses. For the Oak Ridge filters, with a media
effective size of 1.91 mm and at a headloss of 1.5 feet, the solids storage capability is
estimated to be greater than 0.275 pounds per square foot. Each filter cell has dimen-
sions of 2.67' x 4', for a surface area of 10.7 square feet. 10.7 SF x 0.275 pounds/SF =
2.94 pounds per filter cell, or 5.87 pounds for both cells.
If the clarifier effluent has a solids concentration of 20 mg/I, the daily solids total would
be 5.0 pounds at the design flow of 30,000 gpd. Ignoring any solids pass through that
might occur, the average filter run at design flow would be 5.87/5.0*24 = 28 hours. If
the clarifier effluent has a solids concentration of 30 mg/I, the estimated filter run time
at design flow would be reduced to 18.8 hours, which is still acceptable.
The backwash pumps have a pump rate of approximately 340 gallons per minute if the
throttling valves are fully opened, as determined by drawdown measurements. This
equates to a backwash rate of 31.8 gallons per minute. Due to the larger media size,
this flow rate is required to fluidize the bed and produce a bed expansion of approxi-
mately 10%. This backwash flow rate, plus the vigorous air scour that precedes the
filter backwash, combine to provide satisfactory cleaning of the media.

10
8
' 6
u�
0
J
� 4
a�
2
0
I Figure 1 6.9
6w.
Solids Hooding Capacity, 4blsq ftlft of Head Loss
Solids storage capabilities of filter media (ft x 0.304 8 = m; lb/sq ft/ft
x 16.02 = kg/m2•m).