WQ0042579_Additional Information Request #3_20220223

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
February 23, 2022
JOHN NICHOLS, PE, CPESC — PUBLIC UTILITY DIRECTOR
BRUNSWICK COUNTY
POST OFFICE BOX 249
BOLIVIA, NORTH CAROLINA 28422
Subject: Application No. WQ0042579
Additional Information Request 93
Mulberry Branch WRF
High -Rate Infiltration System
SRF Project No.: CS370714-03
Brunswick County
Dear Mr. Nichols:
Division of Water Resources' Central and Regional staff has reviewed the application package
received June 4, 2021, the subsequent resubmittal received July 26, 2021, and the additional information
submittal received November 29, 2021. However, additional information is required before the review may
be completed. Please address the items on the attached pages no later than the close of business on March
25, 2022.
Please be aware that you are responsible for meeting all requirements set forth in North Carolina
rules and regulations. Any oversights that occurred in the review of the subject application package are
still the Applicant's responsibility. In addition, any omissions made in responding to the outstanding items
in Sections A through P, or failure to provide the additional information on or before the above requested
date may result in your application being returned as incomplete.
Please reference the subject application number when providing the requested information. All
revised and/or additional documentation shall be signed, sealed and dated (where needed), with an
electronic copy submitted to my attention at the address below or the our upload site (URL:
https ://e doc s. deq.nc .gov/Form s/NonDi scharge-Branch-Submittal-Form-Ver2).
If you have any questions regarding this request, please do not hesitate to contact me at (919) 707-
3660 or Lauren.Plummer(a�ncdenr.gov. Thank you for your cooperation.
Sincerely,
DocuSigned b
y:
a�U.IA.�.
neer III
Division of Water Resources
cc: Wilmington Regional Office, Water Quality Regional Operations Section (Electronic Copy)
All Ajami, PhD — Division of Water Infrastructure (Electronic Copy)
T. Carter Hubbard, PE — WK Dickson & Co., Inc. (Electronic Copy)
Permit Application File WQ0042579
D EQ �� North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
NORTH CAROHNA -
oePemmencoie,.ironmemsiquar� /� 919.707.9000

Mr. John Nichols, PE, CPESC
February 23, 2022
Page 2 of 4
A. Cover Letter/Response Letter:
1. No comment.
B. Application Fee:
1. No comment.
C. Application:
1. Within Section V. Item 1, the current table lists the designed effluent concentration for Total
Nitrogen as 7 mg/L which is in disagreement with the provided designed effluent concentrations
for Nitrate Nitrogen and Ammonia Nitrogen (4 mg/L each). See Section K — Engineering
Calculations, for further discussion regarding nitrogen removal calculations. Please update Section
V table of the application as needed to address any changes made to the Engineering Calculations.
D. Property Ownership Documentation:
1. No comment.
E. Soil Evaluation:
1. No comment.
F. Agronomist Evaluation:
1. No comment.
G. Hydroeeolo2ic Report:
During the Teams Meeting on February 3, 2022, our staff requested that a single paragraph
summarizing the activities performed to assess the hydrogeology of the site be provided. The
summary does not need to include specific results, but it does need to provide an explanation of
how the assessment activities advanced through each stage of the investigation, evaluation, and
analysis. An additional, separate statements are also requested to provide the reasoning for utilizing
various conductivity measurements at each of the four depths within the MODFLOW simulations.
2. Please provide the corrected site map for the hydrogeological assessment activities that includes
the locations of all pump tests and sampling sites.
H. Water Balance:
1. No comment.

Mr. John Nichols, PE, CPESC
February 23, 2022
Page 3 of 4
I. EngineerinE Plans:
The response to Comment L15 of Additional Information Request 92 did not include a discussion
of the anaerobic selector hydraulics, and further clarification is requested. Following the least
resistant path depicted on Sheet G4, it appears that all of the raw influent flow will pass through
the selector tank on its way to the distributor/splitter box. Meanwhile, RAS is pumped to the pre-
denitrification tank on its way into the distributor/splitter box passing through the selector tank. A
possible outcome in this configuration is that the Bio-P tank may become stagnant. We understand
that the proposed configuration was done to set up Bio-P side stream; however, the hydraulics of
this strategy are uncontrolled and difficult to measure. Please explain the design intent in terms of
flow through each tank and describe how each flow will be changed/managed to adjust nitrogen
and phosphorus removal performance since there are only slide gates and no pumping set-up. If
no plans are in place to allow nitrogen and phosphorus removal performance to be adjusted during
operation, then it is recommended that a different hydraulic configuration of these tanks be
considered such that Bio-P side stream processes could accurately be controlled and monitored.
2. With regards to the design for the anaerobic selector tanks, both the Bio-P and denitrification tanks
need a carbon source, either as external or raw wastewater, to promote PAO growth, VFA
production, and denitrification. The necessary flow control and operational flexibility to achieve
these tasks do not appear to be available in the current design. The Division of Water Infrastructure
recommends considering a different hydraulic configuration to accommodate this need.
The M-sheets and D-sheets were not included in either the uploaded submittal or emailed copy of
the Plans. Please provide a copy of the M-sheets and D-sheets so that we can confirm that
Comments I.13, I.14, and I.16 through I.19 of Additional Information Request 92 were fully
addressed.
J. Specifications:
1. Several sections were revised to remove the references to ultrasonic level meters to address
Comment J.6 in Additional Information Request 92. These sections were not provided, and the
Division does not have a complete, final set of the Specifications for approval. Please provide a
copy of the final signed and sealed Specifications for use in permit issuance.
2. Please update the Davis -Bacon wage determination pay schedule to 2022 within the Specifications.
K. Engineering Calculations:
The presented calculations use permit limits for the designed effluent parameters rather than
supplying values representative of the proposed plant's nutrient removal capability. Please provide
removal calculations that demonstrate what this treatment facility should be capable of achieving
for the effluent constituents (BOD, TSS, NH3-N, TN, TKN, OrgN, TP, and fecal coliform). For
example, we would expect that the predicted calculations should be achieving a BOD much lower
than 10 mg/L. Please review and revise accordingly.
The response to Comment KA, regarding nitrogen removal calculations, mentioned TKN and
ammonia concentrations of 42.6 mg/L and 36.3 mg/L, respectively. However, the updated
calculations continue to use an influent ammonia concentration of 42.6 mg/L. The assumption that
all TKN converts to ammonia is not fully explained or supported within the provided
documentation. For example, has effluent organic nitrogen (recalcitrant, nonbiodegradable) been
evaluated within the Brunswick County Regional system in support of this assumption?

Mr. John Nichols, PE, CPESC
February 23, 2022
Page 4 of 4
3. Following the provided calculations in Section 1—Basis of Design for Ammonia Removal in Ditch,
an effluent ammonia concentration of 4 mg/L is provided on Page 14, but an effluent ammonia
concentration of 7 mg/L is provided near the top of page 15. It is unclear why these values are
different. Please note, that an ammonia effluent limit of 7 mg/L will lead to a total nitrogen limit
in excess of the permit limit of 7 mg/L.
4. The 0.24-million gallon design denitrifying volume listed on Section 1 — Basis of Design, Page 16
is not clearly defined. What volumetric contributions are being associated to each of the explained
locations (e.g. anoxic zones within the oxidation ditch, the bottom of the secondary clarifiers)?
L. Site Map:
1. No comment.
M. Power Reliability Plan:
1. No comment.
N. Operation & Maintenance Plan:
1. No comment.
O. Residuals Management Plan:
1. No comment.
P. Additional Documentation:
➢ Final Environmental Document:
1. No comment.
➢ Floodway Regulation Compliance:
1. Please provide a copy of the communication/documentation provided by the Brunswick County
Floodplain Administrator that corresponds to the 100-year flood plain, Zone A line and
associated call -outs located in the vicinity of Infiltration Basin A.
➢ Threatened or Endangered Aquatic Species Documentation:
1. No comment.