NC0022900_factsheet_20230711

NCDEQ / DWR / NPDES
EXPEDITED FACT SHEET - NPDES PERMIT RENEWAL
NPDES Permit NCO022900
Catherine Shadwell, Compliance & Expedited Permitting Unit / 919-707-3613 June 2023
FACILITY INFORMATION
Facility Name
Sugar Mountain WWTP
Applicant Name
Carolina Water Service of North Carolina (Tony Konsul, Director)
Applicant Address
P.O. Box 240908 Charlotte, NC 28224
Facility Physical
Address/Mailing Address
Physical — 291 Norwood Hollow Road Sugar Mountain, NC 28604
Mailing — same as applicant address
Permitted Flow (MGD)
0.500 MGD
Type of Waste
100% Domestic, < 1 MGD
Facility Class
WW-3
County
Avery
Permit Status
Renewal
Regional Office
ARO
STREAM CHARACTERISTICS
Receiving Stream
Flattop Creek
Stream
Classification
C
Stream Segment
8-22-2
Outfall Lat.
360 07' 56" N
7Q 10 - Summer (cfs)
0.3
Outfall Long.
810 51' 07" W
7Q 10 - Winter (cfs)
0.4
Drainage basin
Watauga
30Q2 (cfs)
0.6
Subbasin
04-02-01
Average Flow (cfs)
2
HUC
060101030201
IWC (%)
72.09% (summer) /
65.96% (winter)
303(d) List
Not listed.
BASIC INFO FOR EXPEDITED PERMIT RENEWAL
Does permit need Daily Max NH3 limits?
Already present in permit
Does permit need TRC limits/footnote?
Already present in permit
Does permit have toxicity testing?
Yes
Does permit have any Special Conditions?
No
oes permit have instream monitoring?
Yes, U&D for Dissolved Oxygen and Temp
ew expiration date:
Sep 30, 2027
Facility Summary
Carolina Water Service Inc of North Carolina operates Sugar Mountain WWTP which provides 100%
domestic wastewater services to the Sugar Mountain area subdivisions which equates to a population of
about 2757. Sugar Mountain WWTP is a minor facility (flow < 1 MGD) with a design capacity and
permitted wastewater discharge of 0.5 MGD. The WWTP was originally permitted in 1982, and this site has
permission to expand to increase the plant capacity to 1.0 MGD but that has not yet happened. This facility
utilizes the following treatment components:
• One common equalization basin
• Three separate plants operating in parallel
0 1 — 0.3 MGD plant
0 2 — 0.1 MGD plants
• Each plant has
o Aeration Basin
Fact Sheet for Permit Renewal
June 2023- NPDES Permit NCO022900 - Page 1

o Clarifier
o Sludge holding tank
o Liquid sodium hypochlorite disinfection
o Liquid sodium bisulfate Dechlorination, and
o Post aeration
• One common, combined flow meter
Renewal Summary
This renewal contains the following changes:
• Added the facility grade to Section A. (1.). and A. (2.)
• Updated the effluent table in Section A. (1.) and A. (2.) with eDMR parameter codes.
• Updated Section A. (3) to reflect current federal requirements for Electronic Reporting of
Discharge Monitoring Reports.
• Added regulatory citations.
• Removed tox testing per 2016 EPA guidance and set new ammonia limits based on IWC
calculations that will go into effect Jan 1, 2028, in section A. (1.)
• Updated Outfall map
Compliance History
4 enforcement cases in the past 5 years — 2 in 2019 and 2 in 2021.
6 NOVS since 2019, most related to ammonia.
3 sanitary sewer overflows in 2022, one of which a manhole overflowed, and 800 gal of
discharge was released in neighboring stream. Repairs, updates, and improvements
performed from 2022 through March of 2023.
Comments on Draft Permit
Fact Sheet for Permit Renewal
June 2023- NPDES Permit NCO022900 - Page 2

PAT MCCRORY
Governor
DONALD R. VAN DER VAART
secremry
Water Resources
ENVIRONMENTAL QUALITY S. JAY ZIMMEi RMAN
Director
Memorandum
To: NPDES Complex Unit
From: Tom Belnick
Date: July 20, 2016
Subject: NPDES Permitting Guidance
NPDES Implementation of Ammonia Criteria- Update
NC has still not adopted an ammonia standard, though it is on our WQS Triennial List for next
round. NC did establish ammonia chronic criteria for use in NPDES permitting back in 1989/90,
which was based on EPA's 1986 criteria development document that factored in pH/Temp across
three regions of the State (see attached). This evaluation resulted in ammonia chronic criteria of
1.0 mg/l NH3-N (summer) and 1.8 mg/l NH3-N (winter) for use in permitting purposes. NC
implements these chronic criteria as Monthly Averages limits utilizing instream dilution. In
2002, NC developed procedures for complimentary acute permit limits (discussed below).
The current ammonia permitting procedures should be as follows:
• The NH3/TRC Wasteload Allocation (WLA) spreadsheet automatically calculates
appropriate ammonia Monthly Average limits for summer and winter. The spreadsheet
assumes a background ammonia concentration of 0.22 mg/1.
• For any permit (new/renewal), always run the NH3/TRC WLA spreadsheet to verify
appropriate Monthly Average Ammonia Limits for protection of aquatic life.
• If the allowable ammonia concentration is greater than 35 mg/l, no limit should be
imposed.
• If the allowable concentration is less than 35 mg/l, then the allowable limit is needed and
the spreadsheet will automatically calculate it.
• For Municipal facilities, the acute limit will be expressed as a Weekly Average, and is
based on multiplying the Monthly Average limit by a factor of 3.
• For non -Municipal facilities, the acute limit will be expressed as a Daily Maximum, and
is based on multiplying the Monthly Average limit by a factor of 5.
• If a new more stringent ammonia limit is required, discuss the need for a Compliance
Schedule with senior staff and then with the Permitee.
• There is no RPA procedure used for ammonia; it is implemented strictly based on WLA
spreadsheet results (similar to TRC).
State of North Carolina I Environmental Quality I Water Resources
1617 Mail Service Center I Raleigh, North Carolina 27699-1617
919 707 9000

Page 12
• A sample NH3/TRC WLA is attached. In this example, the spreadsheet indicates that
Monthly Average ammonia limits of 3.2 mg/1 and 12.7 mg/1 should be imposed for
summer and winter, respectively, in order to protect for NC's chronic ammonia criteria.
Some additional considerations:
This guidance will need to be revisited after NC formally adopts an ammonia standard for
both chronic and acute aquatic life protection.
In the past, some ammonia limits were based strictly on protection of our DO standard
rather than ammonia toxicity, and that is why the permit writer should always verify the
correct ammonia limit with any permit renewal using the WLA spreadsheet.
In the past, some practices allowed for maintaining a less stringent ammonia limit if the
facility was consistently passing the WET test (i.e., biology trumps chemistry). This is
no longer a valid approach and EPA would object. In April 2016 EPA expressly stated
that NC cannot use biology to override chemical results. EPA also disallowed the use of
Action Levels in permitting, in which toxicity test results (if passing) were used to
override the need for permit limits for copper/zinc/silver/iron/chloride.

AMMONIA CRTTERTA TABLES (NH3 as N)
Based on EPA recommended 4-day maximum average concent.ration criteria
(Mou'ntain'sand Trout Waters
TEMPERATURE
H 120C 230C .
6.8 1.8084 1.0028 Total Ammonia
7.5 1,.8084 1.0111 (mg/l NH3 as N)
Pie•dmon:t Freshwaters
r
TEMPERATURE
H 140C 2 60C
6.8 1.8084 1.1344 Total Ammonia
7.5 1.8084 1.1541 (mg/1 NH3 as N)
Coastal Plain and Sandhills Freshwaters
TEMPERATURE
H 160C 280C
6.8 1.7920 0.9700 Total Ammonia
7.5 1.7920 0.9864 (mg/1•NH3 as N)
S
Ex

NH3/TRC WLA Calculations
Facility: Anywhere USA
NC00
Prepared By: Tom Belnick
Enter Design Flow (MGD): 0.03
Enter s7Q10 (cfs): 0.13
Enter w7Q10 (cfs): 0.32
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.13
s7Q10 (CFS)
0.13
DESIGN FLOW (MGD)
0.03
DESIGN FLOW (MGD)
0.03
DESIGN FLOW (CFS)
0.0465
DESIGN FLOW (CFS)
0.0465
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
26.35
IWC (%)
26.35
Allowable Cone. (ug/1)
65
Allowable Cone. (mg/1)
3.2
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
0.32
Monthly Average Limit:
200/100mi
DESIGN FLOW (MGD)
0.03
(If DF >331; Monitor)
DESIGN FLOW (CFS)
0.0465
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
3.80
Upstream Bkgd (mg/1)
0.22
IWC (%)
12.69
Allowable Cone. (mg/1)
12.7
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/I, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals); capped at 35 mg/I
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis); capped at 35 mg/I
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

IWC Calculations
Facility: Sugar Mountain WWTP
Permit No.: NC0022900
Prepared By: Catherine Shadwell
Enter Design Flow (MGD): 0.5 0.2 <= Permitted Flow if Different from Design
Enter s7Q10 (cfs): 0.3
Enter w7Q10 (cfs): 0.4
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
Design
Permitted
Design
Permitted
s7Q10 (CFS)
0.3
0.3
s7Q10 (CFS)
0.3
0.3
DESIGN FLOW (MGD)
0.5
0.2
DESIGN FLOW (MGD)
0.5 €
0.2
DESIGN FLOW (CFS)
0.775
0.31
DESIGN FLOW (CFS)
0.775
0.31
STREAM STD (UG/L)
17.0
17
STREAM STD (MG/L)
1.0
1
Upstream Bkgd (ug/1)
0
0
Upstream Bkgd (mg/1)
0.22
0.22
IWC (%)
72.09
50.82
IWC (%)
72.09
50.819672
Allowable Conc. (ug/1)
24
33
Allowable Conc. (mg/1)
1.3
1.8
< 1 MGD Policy Applies
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Design
Permitted
Design
Permitted
Fecal Coliform
w7Q10 (CFS)
0.4
0.4
Monthly Average Limit:
200/100m1 €
200/100m1
DESIGN FLOW (MGD)
0.5
0.2
(If DF >331; Monitor)
DESIGN FLOW (CFS)
0.775
0.31
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
1.8
Dilution Factor (DF)
1.39
1.97
Upstream Bkgd (mg/1)
0.22
0.22
IWC (%)
65.96
43.66
Allowable Conc. (mg/1)
2.6
3.8
*2B .0404 (c) Applies
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/l, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
By Policy dischargers < 1 MGD get limits no lower than 2 & 4 due to BAT
* From 2B .0404(c) - Winter Limits can be no less stringent than 2 times the summer limits
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

IWC Calculations
Facility: Sugar Mountain WWTP
Permit No.: NC0022900
Prepared By: Catherine Shadwell
Enter Design Flow (MGD): 1 0.2 <=
Permitted Flow if Different from Design
Enter s7Q10 (cfs): 0.3
Enter w7Q10 (cfs): 0.4
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
Design Permitted
Design
Permitted
s7Q10 (CFS) 0.3 0.3
s7Q10 (CFS)
0.3
0.3
DESIGN FLOW (MGD) 1 0.2
DESIGN FLOW (MGD)
1
0.2
DESIGN FLOW (CFS) 1.55 0.31
DESIGN FLOW (CFS)
1.55
0.31
STREAM STD (UG/L) 17.0 17
STREAM STD (MG/L)
1.0
1
Upstream Bkgd (ug/1) 0 0
Upstream Bkgd (mg/1)
0.22
0.22
IWC (%) 83.78 50.82
IWC (%)
83.78
50.819672
Allowable Conc. (ug/1) 20 33
Allowable Conc. (mg/1)
1.2
1.8
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Design Permitted
Design
Permitted
Fecal Coliform
w7Q10 (CFS)
0.4
0.4
Monthly Average Limit: 200/100m1 € 200/100m1
DESIGN FLOW (MGD)
1
0.2
(If DF >331; Monitor)
DESIGN FLOW (CFS)
1.55
0.31
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
1.8
Dilution Factor (DF) 1.19 1.97
Upstream Bkgd (mg/1)
0.22
0.22
IWC (%)
79.49
43.66
Allowable Conc. (mg/1)
2.2
3.8
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/l, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall
be imposed
By Policy dischargers < 1 MGD get limits no lower than 2 & 4 due
to BAT
* From 2B .0404(c) - Winter Limits can be no less stringent than 2
times the summer limits
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)