WQ0042579_Additional Information Request_20211019

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
October 19, 2021
JOHN NICHOLS, PE, CPESC — PUBLIC UTILITY DIRECTOR
BRUNSWICK COUNTY
POST OFFICE BOX 249
BOLIVIA, NORTH CAROLINA 28422
Subject
Dear Mr. Nichols:
Application No. WQ0042579
Additional Information Request 92
Mulberry Branch WRF
High -Rate Infiltration System
SRF Project No.: CS370714-03
Brunswick County
Division of Water Resources' Central and Regional staff, and the Division of Water Infrastructure
staff, have reviewed the application package received June 4, 2021 and the resubmittal received July 26,
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 November 18, 2021.
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 Q, 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 email address below or to our upload site (URL:
https:Hedocs.deg .nc. gov/Forms/NonDischarge-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.
Singer 9A�a by:
�uune�n, �uu�-�Q�u.,w�.►M.en,
a1M`fiINIPlummer, Engineer III
Division of Water Resources
cc: Wilmington Regional Office, Water Quality Regional Operations Section (Electronic Copy)
All Ajami, Division of Water Infrastructure (Electronic Copy)
T. Carter Hubbard, PE — WK Dickson & Co., Inc. (Electronic Copy)
Permit Application File WQ0042579
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
NORM CAROLINA
oePemmentatE.Wra,memsiouari /� 919.707.9000

Mr. John Nichols, PE, CPESC
October 19, 2021
Page 2of11
A. Cover Letter and Executive Summary:
The submitted documents were overall organized to a more navigable format; however, Central
and Regional Office staff noticed numerous duplicates of documents within the submittal file. For
example, there were multiple residuals management plans and multiple copies of the existing
Brunswick County RLAP permit included. This added to the cumbersome nature of the project
submittal and created confusion when trying to identify the most recent version of certain
documents presented for our consideration. When revising the documents to address the following
comments, please also take care to make sure that duplicate information is not being presented.
There are numerous instances throughout the engineering documents where the nomenclature
utilized is inconsistent. For example, pump stations are referred to in some instances by function
(influent pump station) but in others by numeric notation (PS No. 3). Other issues were observed
with manhole labels not matching between plan sheets (see below within Section I - Engineering
Plans). Please review and revise the engineering documents to clarify nomenclature therein to
better facilitate our review.
B. Application Fee:
1. No comment.
C. Application:
L Within Item IV.3, the applicant indicated that an Environmental Assessment (EA) was required
under 15A NCAC O1C; however, the EA was still under review at the time of the submittal. Has a
Finding of No Significant Impact or Record of Decision been issued to the applicant since the last
submission? Please provide an update on the status of the EA.
2. Within Item IVA General Requirements, it appears that several permits are listed as pending. Were
these permit applications still being drafted at the time of the application or had they already been
submitted to their respective permitting authorities? Please provide additional information and an
update of the status of the permits/certifications listed within the table.
General Requirements Item IV.8 indicates multiple values for the 100-year flood elevation to the
facility (26.5 ft within the first portion and 25.6 ft within the follow question). The 100-year flood
line depicted in the vicinity of Infiltration Basin A appears to be closer to the elevation of 64 ft
AMSL. Please provide the flood elevation value that is associated with the Infiltration Basin areas
as it is unclear whether the 2.0 feet of freeboard is met at that location. Additionally, within Item
V.6, the response regarding whether the treatment system is located within the 100-year flood plain
is indicated as N/A. Please revise the response to address whether the listed requirements are met.
Additionally, please review and revise the associated engineering documents, if necessary.
4. In Section V, the table indicates that the designed effluent concentration for TKN is 2 mg/L;
however, the provided engineering calculations indicate that the designed concentration is 7 mg/L.
Please review and revise as needed.
5. Item VILb.i. indicates that the basins include a discharge point. Is this response referring to the
subsurface groundwater lowering system or another discharge point (pipe, spillway, etc.)?

Mr. John Nichols, PE, CPESC
October 19, 2021
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6. Within Section VIII. It is indicated that there is a 57-foot setback available between surface waters
and treatment/storage units. However, within the provided plan sheets, it appears that wetlands are
located within the 50-foot setback distance. Please see comment I.3. Engineering Plans with
regards to the subsurface groundwater lowering drainage system setback. Please provide additional
information and review and revise the engineering documents, if necessary.
D. Property Ownership Documentation:
1. No comment.
E. Soil Evaluation:
1. The provided documentation was extensive, and it appeared that data was included from previous
project work unrelated to this project which created some confusion. Additionally, some of the
prior project reports appeared to present conflicting information. Please provide the following, or
provide a written response to each item and clearly point us to where this information is located in
the existing application:
a. A written response that clearly indicates how many hydraulic conductivity measurements were
taken for each soil series present,
b. A map that clearly shows where all Ksat measurements were conducted within the proposed
infiltration area and their relation to the soils mapped in this area,
c. A compete soil profile description for each hydraulic conductivity measurement point,
d. A copy of the field measurements indicating that steady state was reached for each test
conducted within the restrictive horizon for each soil series, and
e. A summary table of the measurements for each soil series present in the proposed infiltration
area that includes the elevations of the hydraulic conductivity measurements relative to the
proposed basin interface elevations.
F. Agronomist Evaluation:
1. No comment.
G. Hydrogeologic Report:
Within the hydrogeologic analysis, it is stated that "the drain or drains leading toward Mulberry
Creek be able to accommodate 1,213,512 gallons per day of groundwater". Pursuant to 15A NCAC
02T .0704(1), facilities utilizing subsurface groundwater lowering drainage systems shall
demonstrate that groundwater and surface water standards will be protected. Information could not
be located that discusses the chemistry of the water that will be discharged from the drain system
into the nearby wetlands, or the potential impacts of the water chemistry on receiving water bodies.
Please provide additional information that includes estimated effluent concentrations for
parameters that describe the quality of the groundwater discharge water, and provide a discussion
of the effects of these parameters on receiving water bodies. The discussed parameters shall include
at a minimum:
a. Nutrients, including a discussion or model on how nutrients will affect the downstream surface
water quality of Mulberry Branch,

Mr. John Nichols, PE, CPESC
October 19, 2021
Page 4 of 11
b. Iron, which is common to shallow groundwater and may cause an issue with iron bacteria
blooms in receiving waters,
c. pH,
d. BOD, and
e. Turbidity
Whereas the hydrogeologic groundwater model (Modflow) models the spray irrigation and
infiltration basins with the surrounding sub -surface drains, but our understanding is that Modflow
does not model the re-entry of the drain -captured water into the soil/wetland areas down -gradient
of Basins A, B, and C. There appears to be no analysis of the projected 1.2 MGD of drain -captured
water re -directed to the soil/shall soils/wetland areas. Was an analysis performed? We recommend
some type of near -surface hydraulic evaluation be performed to evaluate the impact of this
potentially constant flow of drain water which has been daylighted into these down -gradient
wetland soils.
H. Water Balance:
Within the water balance, it appears that the PAN evaporation data used is for Lumberton, NC. It
is unclear whether these values reflect the coastal evaporation behavior anticipated for the proposed
site.
I. Eneineerine Plans:
1. Plan Sheet G4 depicts Sheet G4:
a. Two 16-inch influent lines are shown without any depiction of these lines being reduced prior to the
influent flow meters. As illustrated in Plan Sheet M2, the line from US Hwy 17 will be reduced from
16 inches to 12 inches prior to the flow meter. In addition, Plan Sheets, C14, C16 and C26 indicate
that the other influent line will be 12 inches. Please revise Plant Sheet G4 to reflect the proper pipe
sizes or explain.
b. The three smaller tanks that comprise the anaerobic selector and the plant's flow path through
them are not depicted. Please show and label the three tanks and show the proposed operational
flow paths.
c. The effluent connection to the diversion pump station is missing.
The setbacks for the proposed wastewater treatment plant depicted on Sheet C5 show areas of
wetlands within the 50-foot setback boundary depicted. Pursuant to 15A NCAC 02T .0506(b), the
setbacks for treatment and storage units shall be 50 feet for surface water such as intermittent and
perennial streams, perennial waterbodies, and wetlands. Please review and clarify or revise as
needed.
Per Sheet C6, the compliance boundary is depicted at what appears to be a distance of
approximately 100 feet from the waste boundary with the review boundary located at a distance of
approximately 250 feet from the waste boundary. Pursuant to 15A NCAC 02L .0107, the
compliance boundary for disposal systems permitted after December 30, 1983 shall be established
250 feet from the waste boundary, or 50 feet within the property boundary, whichever point is
closer to the source. Pursuant to 15A NCAC 02L .0108, the review boundary is established around
any disposal system midway between the compliance boundary and the waste boundary.
Additionally, it is noted that the current design depicts the subsurface groundwater lowering system

Mr. John Nichols, PE, CPESC
October 19, 2021
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within the compliance boundary. Pursuant to 15A NCAC 02T .0705(y) subsurface groundwater
lowering drainage systems shall be prohibited within the compliance boundary. The applicant may
request the compliance boundary be established closer to the waste disposal area under 15A NCAC
02T .0105(h). Please provide additional information with regards to the compliance and review
boundaries, and please review and revise the plan sheets as necessary to meet these requirements.
4. Within the Plan Set, the "Sewer Line - Shared Trench" detail indicates an 18-inch horizontal
separation between parallel pipes for the reclaimed water (Mulberry Branch) infiltration basin force
main and the wastewater effluent (Shallotte) spray field force main. Pursuant to 15A NCAC 02T
.0305, the separation between reclaimed water lines and sewer lines must be 18 inches in the
vertical with reclaimed over sewer, or 24 inches in the horizontal. Please review and revise the
detail and force main alignments as necessary.
5. Per Sheet C28 (Headworks Force Main Sta. 9+00 to 10+00), a tie in to the existing 8-inch force
main is depicted near Sta. 11+50. Is the existing 8-inch force main raw influent being diverted
from the headworks or treated effluent from the existing lagoon facility? Please provide additional
information regarding the force main function within the call -outs for clarity.
6. Per Sheet C29, based on the provided profile view it is unclear how 18 inches of vertical separation
and 3 feet of minimum cover will be maintained at the storm drain crossing near Sta. 27+50. It is
also unclear whether the storm drain is crossing above or below the force main. Please review and
provide clarification via a call -out or revised profile view to indicate that the requirements of 15A
NCAC 02T .0305 are met.
7. Per Sheet C30, based on the provided profile view it is unclear how 18 inches of vertical separation
and 3 feet of minimum cover will be maintained at the storm drain crossing near Sta. 3+80. It is
also unclear whether the storm drain is crossing above or below the force main. Please review and
provide clarification via a call -out or revised profile view to indicate that the requirements of 15A
NCAC 02T .0305 are met.
8. Per Sheet C37, the force main crosses the groundwater lowering system underdrain near Sta.
43+25; however, this feature is not depicted on the profile view. Please add this crossing to the
profile view and indicate the vertical separation at this and all other crossings between the proposed
force main and the groundwater lowering system underdrains.
9. Per Sheet C38, the call -out near Sta. 52+00 identifies the Effluent Force main to Infiltration Basin
B, and the same call -out is listed near Sta. 59+00. Is the call -out near Sta. 52+00 referring to
Infiltration Basin C? Please review and revise.
10. Per Sheet C48, it appears that the groundwater lowering system discharges at two outfalls. One is
a combined outfall located between Basins A and B, and the other is an outfall designed to serve
Basin C. With the provided views, it is unclear the proximity between the outfall's level spreaders
to the existing wetlands and Mulberry Branch. Please provide an additional plan sheet that depicts
the outfalls, proposed flows, proposed flow rates, and topographic features related to the
groundwater lowering system and its hydraulics.
11. Plug valves are depicted around the manhole prior to discharge to the outfall and level spreader for
the combined Basin AB piping. The manhole prior to discharge to the outfall for Basin C does not
have the same configuration. It was unclear why these discharges were designed with different
configurations, should both discharges have plug valves? Please review and revise if needed.
12. The soil profiles within Sheet C54 depict clay encountered at final bottom elevation (54.0 ft AMSL)
overlain by clean sand at several locations. Within the Soils and Hydrologic Report, it indicates

Mr. John Nichols, PE, CPESC
October 19, 2021
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that clay lenses are to be removed; however, the Specifications do not appear to include provisions
for the over -excavation of clays within the infiltration basins. Please provide additional
information regarding the extent of the proposed clay lens removal.
13. Per Sheet M6, to the left of ITP-1 an 8-inch PVC pipe is called out, it appears to be related to the
wet well drain line; however, the call -out at the top of the plan sheet refers to this as a 6-inch line.
An 8" x 6" reducer is not depicted between these two call -outs. Please review the pipe diameter of
the wet well drain line and revise if needed.
14. Per Sheet M10, the manhole located to the northwest of the oxidation ditch (receiving the proposed
8-inch drain line) is listed as MH#9 and includes a call -out stating to see Sheet C15. The manhole
that appears to be depicted on Sheet C15 in the same location is labeled ME-5. A similar issue is
observed for the plan south oxidation drain line which has a call -out on sheet M10 labelling the
manhole as MH#7, but the manhole depicted on Sheet C15 in the same location is labelled ME-3.
Please review and revise as needed.
15. Per Sheet M10, the configuration of the anaerobic selector is unclear and the hydraulics of the
anaerobic selector are unknown. Please provide additional information regarding the anaerobic
selector including the proposed functions of each tank, the anticipated flow path for the RAS and
influent lines. Please clarify and revise as necessary.
16. Per Sheet M11, multiple bypass lines for the anaerobic selector are depicted in the profile view.
These are not clearly labelled on the plan view on M10 and the piping plan view on Sheet C15 does
not go to this level of detail. Please clarify and revise the piping for the anaerobic selector and
oxidation ditch treatment units.
17. Per Sheet M14, the inlet piping from the oxidation ditch combination well to the clarifiers is not
labeled. The adjacent slide gate appears to be a 24" x 24" slide gate, but it is unclear what pipe
diameter and material is proposed. Please review and revise as needed.
18. Within Sheet M21 an outline of a future bank is indicated; however, this future UV bank was not
identified on the other plan sheets, is it intended to be provided as a parallel channel at a future
date? Please provide additional information.
19. Sheet D2 depicts the proposed level spreader. Please explain how the recovered groundwater will
be disposed after draining to the two 30 ft sections of 24-inch diameter, 16-gauge, corrugated metal
pipe. Is the calculated flowrate of 2.02/2.21 cfs found in the engineering calculations associated
with the upwards flow -rate through the aluminum grates associated with these features?
J. Specifications:
1. Per 09 90 00 — 9 the color -coding requirements include finished water, but it was noted that the
colors called out for treated wastewater effluent to the sprayfields and treated reclaimed water to
the infiltration basins identified in the Plan Set were not included in this table. Please review and
revise.
2. Section 22 13 30 Self -Priming Pumps and Accessories, Part 2.6 Pump Controls indicates that Pump
Station 1 and Pump Station 2 (which per our understanding share a wet well) are both to initiate all
three pumps in the event of a high-level alarm. Based on the provided Plan Sheets it appears only
one high-level alarm is present within the influent pump station which would result in six pumps
(ITP-1 through ITP-3; EQTP-1 through EQTP-3) activating simultaneously. Is that the intent of

Mr. John Nichols, PE, CPESC
October 19, 2021
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the design? Please provide additional information and review and revise the engineering
documents as necessary.
3. Section 3123 16 — 3, Part 2.3 regarding Fill for High -Rate Infiltration Basins it is unclear whether
off -site fill material is to be analyzed to confirm that it is free of contamination prior to being
brought on site. Is the proposed fill material from an on -site borrow? Please provide additional
information.
4. Within the definitions of Section 33 11 00, the utility company is listed as Lincoln County. Please
review and revise as needed.
5. The leakage formula provided in 33 34 00 Sanitary Utility Sewerage Force mains is not the most
recent per AWWA C600 standards. The value in the denominator in the most recent standard is
148,000 and not 133,200. Please review and revise as needed.
6. Numerous sections of the Specifications reference Section 40 72 13 Ultrasonic Level Meters;
however, this section was not provided in the submitted Specifications set. Please review and
revise.
K. En2ineerin2 Calculations:
1. Engineering design calculations must be signed, sealed, and dated by a North Carolina licensed
Professional Engineer in good standing. Please review and revise.
2. Within Section 2 — Hydraulic Profile of WWTP it lists that two treatment units are in service for
the average daily flow (ADF) — with the exception of the disc filter. However, for the Peak flow it
lists only one of each of the unit processes. It appears that the columns have been reversed, and it
is unclear whether this error is continued throughout the summary. Please review and revise as
needed.
3. Throughout the calculations different nomenclatures are used when referring to different pumps.
Is the Aerobic Digester: Transfer Pump referring to the pumps transferring RAS/WAS to West
Brunswick? Within the pump data sheets for the Drain Pump Station it refers to both the Drain
Pump Station and the Diversion Pump Station. Please clarify the nomenclature and choose a
consistent naming convention throughout the provided engineering documents.
4. Within the nitrogen removal calculations, the following items were noted:
a. The provided design volume of the denitrifying tank (0.8 MG) is equal to the combined
oxidation ditch volume. Since nitrification happens in oxidation ditch as well, the whole
volume cannot be used for denitrification. Please review and revise as needed.
b. The provided influent TKN of 36.3 mg/L does not agree with the provided influent
ammonia of 42.6 mg/L. Furthermore, the effluent TKN value of 7.0 mg/L does not translate
to a TN of 7.0 mg/L. To qualify for the reduced setbacks outlined in 15A NCAC 02T
.0706(b), the designed total nitrogen effluent limit of 7 mg/L must be met. Nitrate and
Nitrite concentrations also need to be considered to calculate denitrification efficiency.
Please breakout the ammonia, organic-N, and nitrate contributions to total nitrogen. Please
review and revise as needed.
5. It appears that BioWin was used for calculations. Please provide the BioWin input and output table
along with a visual plant model representation for our consideration. From the hydraulic
configuration provided on Sheet M10, it appears that only the RAS flow is being sent to the major

Mr. John Nichols, PE, CPESC
October 19, 2021
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anaerobic tank with the influent bypassing the main anaerobic tank prior to entering the oxidation
ditch influent weir structure. Should the main influent line be routed into the large anaerobic tank
for Bio-P growth? The current operational configuration is unclear, please review and revise the
associated engineering documents and identify how these configurations are represented in
BioWin.
L. Site May:
The submittal identified Plan Sheets C3, C4, C5, C6, and C9 as the documents to be considered as
the site maps. The referenced maps do not include a labelled facility map calling out the unit
processes to be listed within the permit's facility description. Please note that the site maps are
used during permit, and many applicants choose to create site maps separate from the plan set that
utilize both topographic contour base maps and aerial base maps to assist in pointing out key
features. Please review and revise your site maps and include a map that clearly identifies the
proposed unit processes.
M. Power Reliability Plan:
1. No comment.
N. Operation & Maintenance Plan:
Within the O&M Plan, the section on Operation and Control of Unit Processes (Section 3) consists
of just a introductory paragraph. Within Section 22 13 30 Self -Priming Pumps and Accessories in
the Specifications, there are numerous references to a high -alarm level strategy that involves
initializing all of the available pumps (including the standby/backup pumps) to mitigate increased
flow volumes in the wet wells. However, it is unclear how the discharge -side unit processes will
perform under these increased flow conditions. If the pump station upstream of the oxidation ditch
has a high -alarm level what protocols will be enacted to prevent a washout?
2. Within the plant piping, it appears that low slope gravity lines are being proposed. Is there a
flushing protocol planned for the facility to manage solids deposition? Please provide additional
information.
O. Residuals ManaLlement Plan:
1. A copy of the Brunswick County RLAP permit (WQ0034513) was provided within the Residuals
Management Plan. Please note that prior to operation of the Mulberry Branch facility, a
modification to the RLAP permit adding Mulberry Branch to the approved residuals sources
(Attachment A) will need to be submitted and approved by the Non -Discharge Branch.
P. Additional Documentation:
➢ Certificate of Public Convenience and Necessity:
1. Not applicable.
➢ Existing Permit:

Mr. John Nichols, PE, CPESC
October 19, 2021
Page 9 of 11
1. Not applicable.
➢ Final Environmental Document:
1. The submittal indicated that an Engineering Report/Environmental Information Document was
submitted on December 17, 2020; however, a final ruling/response was not provided. Please
provide the Finding of No Significant Impact (FONSI) or the Record of Decision (ROD) for
our review.
➢ Floodway Regulation Compliance:
A portion of proposed Infiltration Basin A is located within the 100-year floodplain. In addition to
the basin structure, a subsurface groundwater lowering system is proposed that will traverse a portion
of the 100-year floodplain. The documentation of No Impact provided in the submittal appears to
reference the proposed culvert construction at Mulberry Branch and does not reference the potential
impacts of the proposed infiltration basin and groundwater lowering system. Within Chapter 143
Article 21 Part 6 of the General Statutes, it is stated that a local government may adopt ordinances to
regulate uses in flood hazard areas and grant permits for the use of flood hazard areas that are
consistent with the requirements of this Part. Please provide written documentation from all local
governing entities that the proposed facility modifications are in compliance with all local ordinances
regarding construction or operation of wastewater treatment and/or disposal facilities within the
floodplain.
2. Is the proposed design, including the infiltration basins and groundwater lowering system, in
compliance with the Cape Fear River Buffer Rules? Please confirm and/or provide additional
information.
The provided no -rise certification of the Mulberry Branch culvert was neither approved nor
disapproved. Has an approval for the no -rise certification been granted?
➢ Operational Agreements:
1. Not applicable.
➢ Threatened or Endangered Aquatic Species Documentation:
1. A map was provided labelled the "Federally Protected Species" document and it was indicated
that this project will not impact any endangered species. However, throughout the plan sheets
there are several call -outs indicating the location of endangered species along the force main
alignments. Please provide additional information regarding the referenced endangered plant
species and any pertinent documentation of these impacts.
➢ Wastewater Chemical Analysis:
1. Not applicable.
Q. Comments from Division of Water Infrastructure Staff
1. Plans:
a. Please incorporate DWI Project number (CS370714-03) into the plans cover sheet.
b. Please provide a schematic layout of all existing force mains connecting to the diversion pump
station. Please label every force main with arrows showing the direction and information as to

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October 19, 2021
Page 10 of 11
where they come and go. Also, in the calculations please provide the pumping characteristics
of this diversion pump station.
c. A considerable amount of energy will be put into the Mulberry Branch WRF to separate the
WAS so that it can be mixed again with other raw sewers to send to the West Brunswick
Regional WRF through the diversion pump station. Has the County considered continually
operating the digester and sending digested TWAS to West Brunswick by truck to utilize the
existing Class A sludge process? Mixing WAS with other sewer to send to WBWRF seems to
be redundant and also cost the County more treatment energy.
2. Specifications:
a. Please incorporate DWI Project number (CS370714-03) into the specification cover sheet.
b. Please update Davis -Bacon wage determination pay schedule needs to 2021.
c. Are there any easements or encroachments required for this work to be done? If yes, have they
been acquired? If yes, please provide in the specifications.
3. Engineering Calculations:
a. A Peaking Factor of 2.5 was selected since flow is adjustable using motorized valves out on
the 24-inch force main interconnecting other WWTPs. Please provided combined WWTP
capacity and history of accepting flow in the network connected to future Mulberry Branch
WRF. Also, please describe how Brunswick County would manage a wet weather scenario
where sewer flow exceeds combined WWTP capacity.
b. Please provide the past 5 years of daily historical data of influent flow, BOD, TSS, TN, and
TP. Please also provide any COD data, if available.
4. Additional Documents:
a. Please submit the DWI bid and design submittal checklist
(https:Hfiles.nc.gov/ncdeq/WI/Design/PS_SubmittalChecklist_180710.docx ) with associated
documentation.
b. Please provide the tentative future 5 MG expansion layout. Please also provide a generalized
disposal plan, will this proposed expansion involve additional land acquisition?
c. Please provide an updated cost estimate.
R. Recommendations: (Response not required)
The Piping Plan for the proposed WWTP (Sheet C15) includes multiple 8-inch diameter gravity
sewers depicted with a slope at 0.04%. The minimum design criteria for 8-inch diameter gravity
sewers is 0.4% (0.4 ft per 100 ft) as outlined within the NCDEQ "Minimum Design Criteria for the
permitting of Gravity Sewers". The Ten States Standards for Wastewater Facilities recommends
increased slopes for gravity discharge piping for sludges (Chapter 80, Section 87.2). Please
consider increased slopes in accordance with these guidelines.
2. The proposed groundwater lowering system outfalls at two points with the level spreader/outfall at
combined Basins A and B discharging roughly twice the flow as the level spreader at Basin C. We
recommend that the groundwater lowering system outfalls at a minimum of three points, one for
each Basin, with separation distances suitable to mitigate impacts to the surrounding wetlands.
3. A copy of the Brunswick County RLAP permit (WQ0034513) was provided within the Residuals
Management Plan. Please note that prior to operation of the Mulberry Branch facility, a

Mr. John Nichols, PE, CPESC
October 19, 2021
Page 11 of 11
modification to the RLAP permit adding Mulberry Branch to the approved residuals sources
(Attachment A) will need to be submitted and approved by the Non -Discharge Branch.
4. During the site visit, it was noted that in areas adjacent to the proposed infiltration basins vegetative
screens will need to be maintained to prevent dust generated by nearby farming and logging
activities from clogging the infiltration basins. Please consider adding a general note within the
plans or additional language within the specifications addressing this concern.