NC0082694_More Information (Requested)_20210607

ROY COOPER
Governor
DIONNE DELLI-GATTI
Secretary
S. DANIEL SMITH
Director
Zackery L. Foreman, WTP Supt.
Town of Dallas
210 N Holland St
Dallas, NC 28034
Dear Mr. Foreman:
NORTH CAROLINA
Environmental Quality
June 7, 2021
Subject: Request for Additional Information
Renewal NPDES Permit NC0082694
Dallas WTP
Gaston County
The Division has reviewed your application, received on February 21, 2020, for renewal of NPDES permit
NC0082694. To enable us complete our review in accordance with N.C.G.S. 143-215.1 and 15A NCAC 2H.0105,
please provide additional or revised information to address the following comments:
1. Please provide five (5) days of Total Hardness (CaCO3 or (Ca + Mg)) data for the following:
a. effluent
b. upstream of Outfall 001.
2. Please confirm that the units of measure for all total copper data from October 2016 to present were
reported correctly. The values for copper appear to have been reported in mg/L (milligrams per liter) instead
of the unit of measurement indicated as µg/L (micrograms per liter). This is a very common reporting error.
It should also be noted that a method detection level reported of <0.005 jig/L (5 ng/L, nanograms per liter)
for copper would not be possible with conventual water quality laboratory methods that we are aware of.
You need to also review reported units of measurement for other metals data such as iron, manganese, and
aluminum. Please provide a list of any corrected values in response to this additional information request.
Please amend DMRS as necessary.
The NC 2007-2014 Water Quality Standard (WQS) Triennial Review was approved by the NC Environmental
Management Committee (EMC) on November 13, 2014. The US EPA subsequently approved the WQS revisions
on April6, 2016 with some exceptions. The NC Division of Water Resources is required to implement the new
dissolved metal standards in all permits public noticed after April 6, 2016.
The new standards for most metals include acute standards. Furthermore, the freshwater standards for several
metals are expressed as the dissolved form of the metals, and seven metals have hardness -dependent equations.
As a result, the Division will need site -specific effluent hardness data in order to calculate permit limitations. The
metal of concern for this permit renewal is copper.
To evaluate dissolved Copper, a Reasonable Potential Analysis (RPA) was conducted using copper DMR data
from October 2016 to March 2021. Assuming that the values reported for copper were in mg/L instead of jig/L,
results indicated a reasonable potential to exceed the new dissolved metals standard for copper. Consequently, the
following daily maximum limits (acute standard) and monthly average limit (chronic standard) for total copper
may be applied for this permit renewal:
�D_E
NORTH CAROLINA
Department of Environmental Quality
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617
919.707.9000

Parameter Outfall Monthly Average Limit
Total Copper 001 763.31 µg/L
Daily Maximum Limit
830.57 µg/L
To calculate the limits above a default hardness of 25 mg/L was entered for both the effluent and upstream values.
Additionally, a 7Q10 flow of 89 cfs was provided by the USGS on June 4, 2021. Additionally, the maximum
monthly average of 0.599 MGD for Outfall 001 was used as the effluent flow. The maximum monthly average
was based on flow data from April 2018 to March 2021. Calculation of final copper limits will be dependent on
the effluent and upstream hardness data that we have requested. For a summary of this information, please see the
attached RPA, "Dissolved to Total Metal Calculator", and Low Flow information provided by the USGS.
If no response is received within 60 calendar days [per 15A NCAC 2H.0107(b)], the permit will be renewed
without the benefit of the requested additional information. Therefore, a default effluent hardness of 25 mg/L will
be used to calculate effluent limits for copper as indicated above. Please submit the additional information
requested by one of the following:
Electronically: [e-mail]
Address For USPS:
Attention: Derek Denard
Division of Water Resources
WQ Permitting Section — NPDES
1617 Mail Service Center
Raleigh, NC 27699-1617
Physical Address for parcel packages:
Attention: Wren Tredford
Division of Water Resources
WQ Permitting Section — NPDES
512 N. Salisbury Street
(9th Floor -Archdale Bldg)
Raleigh, NC 27604
If you have questions concerning the draft, please contact me at 919-707-3618, or via e-mail at
[e-mail].
ec:
Sincerely,
Derek Denard, Environmental Specialist
NPDES Compliance and Expedited Permitting
Division of Water Resources, NCDEQ
NPDES File [Laserfiche]
Jack Foreman [zforman@dallasnc net]
RRO / Ori Tuvia [[e-mail]]; Andrew Pitner [[e-mail]]

Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators
MAXIMUM DATA POINTS = 58
REQUIRED DATA ENTRY
Table 1. Project Information
Facility Name
WWTP/WTP Class
NPDES Permit
Outfall
Flow, Qw (MGD)
Receiving Stream
HUC Number
Stream Class
❑ CHECK IF HQW OR ORW WQS
Dallas WTP
PC-1
NC0082694
001
0.599
South Fork Catawba River
WS-IV; CA
❑ Apply WS Hardness WQC
7Q10s (cfs)
7Q1Ow (cfs)
30Q2 (cfs)
QA (cfs)
1Q10s (cfs)
89.00
178.00
239.00
723.00
72.71
Effluent Hardness
Upstream Hardness
Combined Hardness Chronic
Combined Hardness Acute
25 mg/L (Avg)
25 mg/L (Avg)
25 mg/L
25 mg/L
Data Source(s)
❑ CHECK TO APPLY MODEL
Follow directions for data entry. In some cases a
comment menu list the available choices or a
dropdown menu will provide a list you may select
from. Error message occur if data entry does not
meet input criteria.
Table 2. Parameters of Concern
Par01
Par02
Par03
Par04
Par05
ParO�
Par07
Par08
Par09
Par10
Par11
Par12
Par13
Par14
Par15
Par16
Par17
Par18
Par19
Par20
Par21
Par22
Par23
Par24
Par25
Name
WQS
Type Chronic Modifier
Acute
PQL Units
Arsenic
Aquactic Life
C
150
FW
340
ug/L
Arsenic
Human Health
Water Supply
C
10
HH/WS
N/A
ug/L
Beryllium
Aquatic Life
NC
6.5
FW
65
ug/L
Cadmium
Aquatic Life
NC
0.5899
FW
3.2396
ug/L
Chlorides
Aquatic Life
NC
230
FW
mgi.
1 Chlorinated Phenolic Compounds
water supply
NC
1
A
ug/L
Total Phenolic Compounds
Aquatic Life
NC
300
A
ug/L
Chromium III
Aquatic Life
NC
117.7325
FW
905.0818
ug/L
Chromium VI
Aquatic Life
NC
11
FW
16
Ng/L
Chromium, Total
Aquatic Life
NC
N/A
FW
N/A
Ng/L
Copper
Aquatic Life
NC
7.8806
FW
10.4720
ug/L
Cyanide
Aquatic Life
NC
5
FW
22
10
ug/L
Fluoride
Aquatic Life
NC
1,800
FW
ug/L
Lead
Aquatic Life
NC
2.9416
FW
75.4871
ug/L
Mercury
Aquatic Life
NC
12
FW
0.5
ng/L
Molybdenum
Human Health
NC
2000
HH
ug/L
Nickel
Aquatic Life
NC
37.2313
FW
335.2087
Ng/L
Nickel
Water Supply
NC
25.0000
WS
N/A
Ng/L
Selenium
Aquatic Life
NC
5
FW
56
ug/L
Silver
Aquatic Life
NC
0.06
FW
0.2964
ug/L
Zinc
Aquatic Life
NC
126.7335
FW
125.7052
ug/L
NC0082694 RPA 2021, input
6/7/2021

REASONABLE POTENTIAL ANALYSIS
H1
Effluent Hardness
Use "PASTE SPECIAL•
Values" then "COPY" .
Maximum data points
= 58
Date Data BDL=1/2DL Results
1 25 25 Std Dev. N/A
2 Mean 25.0000
3 C.V. 0.0000
4 n 1
5 10th Per value 25.00 mg/L
6 Average Value 25.00 mg/L
7 Max. Value 25.00 mg/L
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
H2
Upstream Hardness
Use "PASTE SPECIAL•
Values" then "COPY" .
Maximum data points
= 58
Date Data BDL=1/2DL Results
1 25 25 Std Dev. N/A
2 Mean 25.0000
3 C.V. 0.0000
4 n 1
5 10th Per value 25.00 mg/L
6 Average Value 25.00 mg/L
7 Max. Value 25.00 mg/L
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
-2-
NC0082694 RPA 2021, data
6/7/2021

REASONABLE POTENTIAL ANALYSIS
Pall
Copper
Date Data BDL=1/2DL Results
1 10/11/2016 < 5 2.5 Std Dev.
2 1/10/2017 < 5 2.5 Mean
3 4/18/2017 173 173 C.V.
4 7/25/2017 5 5 n
5 10/26/2017 < 5 2.5
6 1/9/2018 5 5 MultFactor= 2.52
7 4/17/2018 30 30 Max. Value 657.00 ug/L
8 7/11/2018 657 657 Max. Pred Cw 1655.64 ug/L
9 10/23/2018 < 5 2.5
10 1/8/2019 < 5 2.5
11 4/9/2019 16 16
12 7/23/2019 12 12
13 10/15/2019 17 17
14 1/21/2020 < 5 2.5
15 4/14/2020 28 28
16 7/7/2020 14 14
17 10/13/2020 8 8
18 1/19/2021 6 6
Use"PASTE
SPECIAL -Values
then "COPY" .
Maximum data
points = 58
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
155.3599
54.7778
2.8362
18
Par13
Fluoride
Date Data
10/11/2016 < 100
1/10/2017 < 100
4/18/2017 260
7/25/2017 120
10/26/2017 100
1/9/2018 < 100
4/17/2018 180
7/11/2018 200
10/23/2018 140
1/8/2019 < 100
4/9/2019 < 100
7/23/2019 < 100
1/21/2020 < 100
4/14/2020 100
7/7/2020 110
10/13/2020 < 100
1/19/2021 160
BDL=1/2DL Results
50 Std Dev.
50 Mean
260 C.V.
120 n
100
50 Mult Factor = 1.46
180 Max. Value 260.0 ug/L
200 Max. Pred Cw 379.6 ug/L
140
50
50
50
50
100
110
50
160
Use"PASTE
SPECIAL -Values"
then "COPY" .
Maximum data
points = 58
64.9094
104.1176
0.6234
17
-3-
NC0082694 RPA 2021, data
6/7/2021

Dallas WTP
NC0082694
Freshwater RPA -
Qw (MGD) = 0.60
1Q10S (cfs) = 72.71
7Q1OS (cfs) = 89.00
7Q1OW (cfs) = 178.00
30Q2 (cfs) = 239.00
Avg. Stream Flow, QA (cfs) = 723.00
Receiving Stream: NO HUC NUMBER
95% Probability/95% Confidence Using Metal Translators
MAXIMUM DATA POINTS = 58
WWTP/WTP Class: PC-1
IWC% @ 1Q10S = 1.260822301
IWC% @ 7Q1OS = 1.032431894
IWC% @ 7Q1OW = 0.518894564
IWC% @ 30Q2 = 0.386969532
IW%C @ QA = 0.128251625
Stream Class: WS-IV; CA
Outfal 1001
Qw = 0.599 MGD
COMBINED HARDNESS (mg/L)
Acute = 25 mg/L
Chronic = 25 mg/L
YOU HAVE DESIGNATED THIS RECEIVING
STREAM AS WATER SUPPLY
Effluent Hard: 0 value > 100 mg/L
Effluent Hard Avg = 25 mg/L
PARAMETER
TYPE
111
NC STANDARDS OR EPA CRITERIA
Ci
a
0
i_
n
REASONABLE POTENTIAL RESULTS
RECOMMENDED ACTION
Chronic
Standard Applied
Acute
Il
# Det. Max Pred Cw Allowable Cw
Copper
NC
7.8806
FW(7Q10s)
10.4720
ug/L
18
12
1,655.64
Acute: 830.57
_ _ _ _ _ --
• Chronic---- --
No value > Allowable Cw
RP shown - apply Monthly Monitoring with Limit
----------------------------
RP shown - apply Monthly Monitoring with Limit
Fluoride
NC
1800
FW(7Q10s)
ug/L
17
9
379.E
Acute: NO WQS
_ _ _ _____ _ _ _
Chronic 174,345.6
No value > Allowable Cw
_ _ _ _ _ _ _ _ _ _ ___ _
No RP, Predicted Max < 50 % of Allowable Cw No
Monitoring required unless Fluoride in use
Page 4 of 5
NC0082694 RPA 2021, rpa
6/7/2021

Date: 6/7/2021
FACILITY: Dallas WTP
NPDES PERMIT: NC0082694
Dissolved to Total Metal Calculator
In accordance with Federal Regulations, permit limitations must be written as Total Metals per 40 CFR 122.45(c)
Receiving
Stream
summer
7Q10 (CFS)
Receiving
Stream
summer 7Q10
(MGD)
Rec. Stream
1Q10
[MGD]
NPDES
Flow Limit
[MGD]
Total Suspended
Solids
-Fixed Value-
(mg/L)
Combined
Hardness
chronic
(mg/L)
Combined
Hardness
Acute
(mg/L)
Instream
Wastewater
Concentration
(Chronic)
Instream
Wastewater
Concentration
(Acute)
Upstream
Hardness
Average (mg/L)
Effluent
Hardness
Average
(mg/L)
89.0000
57.4194
46.9097
0.5990
10
25.000
25.000
1.0324
1.2608
25
25
PARAMETER
Dissolved Metals
Chronic
Acute
[ug/I]
[ug/I]
US EPA
Translators- using
Default Partition
Coefficients
(streams)
Maximum Allowable Effluent Concentration
(MAEC) as a Total Metal
=Dissolved Metal -Translator
Chronic
Acute
Upstream Hard Avg (mg/L) _
25
EFF Hard Avg (mg/L) = 25
[ug/I]
[ug/I]
Cadmium (d)
0.15
0.82
0.252
0.59
3.24
Cd -Trout streams
0.15
0.51
0.252
0.59
2.01
Chromium III (d)(h)
24
183
0.202
117.73
905.08
Chromium VI (d)
11
16
1.000
11.00
16.00
Chromium, Total (t)
N/A
N/A
Copper (d)(h)
2.7
3.6
0.348
7.88
10.47
Lead (d)(h)
0.54
14
0.184
2.94
75.49
Nickel (d)(h)
16
145
0.432
37.23
335.21
Ni - WS streams (t)
Silver (d)(h,acute)
0.06
0.30
1.000
25
0.06
0.30
Zinc (d)(h)
36
36
0.288
126.73
125.71
COMMENTS (identify parameters to PERCS Branch to maintain in facility's LTMP/STMP):
(d) = dissolved metal standard. See 15A NCAC 026 .0211 for more information.
(h) = hardness -dependent dissolved metal standard. See 15A NCAC 026.0211 for more information.
(t) = based upon measurement of total recoveable metal. See 15A NCAC 026 .0211 for more information.
The Human Health standard for Nickel in Water Supply Streams is 25 mg/L which is Total Recoverable metal standard.
The Human Health standard for Arsenic is 10 µg/L which is Total Recoverable metal standard.

6/7/2021 Mail - Denard, Derek- Outlook
USGS response to DWR USGS Low Flows request# 2021-124 (dated 2021/05/27) for SF
Catawba River Gaston County... RE: [EXTERNAL] Low -flow request approval
Weaver, John C <[e-mail]>
Fri 6/4/2021 5:47 PM
To: Denard, Derek <[e-mail]>
Cc: Hill, David A <[e-mail]>; Kebede, Adugna <[e-mail]>; Montebello, Michael J
<[e-mail]>; Albertin, Klaus P <[e-mail]>; Weaver, John C <[e-mail]>
CAUTION: External email. Do not click links or open attachments unless you verify. Send all suspicious email as an attachment
to Rei::lort Si::1am.
Derek,
h response to your inquiry about the low -flow characteristics for a location on the South Fork Catawba River at
NC Highway 275 at Dallas in Gaston County, the following information is provided:
A check of the low -flow files here at the USGS South Atlantic Water Science Center (SAWSC, Raleigh office)
indicates a previous low -flow determination for the point of interest, identified by the lat/long coordinates
{35.3300, -81.1328) provided via email dated 05/27/2021 from the DWR USGS Low Flow portal following your
request submission. Completed in December 1988, the low -flow characteristics for the point of interest (station
id 0214390800, drainage area 557 sqmi) were estimated based on transfer of flow characteristics (by drainage -
area proration) from a downstream continuous -record streamgage on the South Fork Catawba River at Lowell
(station id 02145000, drainage area 628 sqmi).
No USGS discharge records are known to exist for the point of interest on the South Fork Catawba River at NC
Highway 275.
h the absence of site -specific discharge records sufficient for a low -flow analysis, estimates of low -flow
characteristics at ungaged locations are determined by assessing a range h the low -flow yields (expressed as flow
per square mile drainage area, or cfsm) at nearby sites where estimates have been determined.
A basin delineation completed using the on line USGS StreamStats application for North Carolina
(httP-s://streamstats.usg gov/ss/) indicates the drainage area for the point of interest (StreamStats adjusted
coordinates 35.33038, -81.13253 NAD83) is 556 sqmi, which confirms the drainage area submitted as part of the
request information.
For streams in Gaston County, low -flow characteristics published by the USGS are provided in the following
reports:
(1) The first is a statewide report completed in the early 1990's. It is USGS Water -Supply Paper 2403, "Low -flow
characteristics of streams in North Carolina" {Giese and Mason, 1993). An on line version of the report is available
at htt P-ubs.usg gov/wsp/2403/reP-ort.P-df. The report provides the low -flow characteristics (based on data
through 1988) via regional relations and at -site values for sites with drainage basins between 1 and 400 sqmi and
not considered or known to be affected by regulation and/or diversions.
(2) The second is a statewide report published in March 2015. It is USGS Scientific Investigations Report 2015-
5001, "Low -flow characteristics and flow -duration statistics for selected USGS continuous -record streamgaging
stations in North Carolina through 2012" (Weaver, 2015). The report is available online at
htt P-ubs.usg gov/sir/2015/5001/. The report provides updated low -flow characteristics and flow -duration
statistics for 266 active (as of 2012 water year) and discontinued streamgages across the state where a minimum
of 10 climatic years discharge records were available for flow analyses.
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6/7/2021 Mail - Denard, Derek- Outlook
Low -flow characteristics estimated for point of interest:
Inspection of the reports indicates the presence of fourteen (14) nearby selected USGS partial -record sites (9) and
continuous -record streamgages (5) within the South Fork Catawba River basin where low -flow characteristics
were published. Included among these 14 index sites is the downstream continuous -record streamgage on the
South Fork Catawba River at Lowell (station id 02145000, drainage area 328 sqmi, active site with period of daily
mean discharge records since 1942 water year). Comparison of the low -flow yields at the Lowell streamgage with
the average and median low -flow yields from among the remaining 13 index sites indicated a very favorable
comparison. It is therefore judged reasonable and appropriate to apply the ranges of low -flow yields from among
these 14 sites to the point of interest.
Among these 14 index sites, the low -flow discharge yields for the indicated flow statistics are as follows:
Annual 7010 low -flow yields==> from 0.029 to 0.24 cfsm (average about 0.16 cfsm, median about 0.17 cfsm)
Annual 30Q2 low -flow yields ==> from 0.2 to 0.58 cfsm (average about 0.43 cfsm, median about 0.44 cfsm)
Winter 7Q10 low -flow yields ==> from 0.14 to 0.43 cfsm (average about 0.32 cfsm, median about 0.36 cfsm)
Annual 7Q2 low -flow yields==> from 0.14 to 0.51 cfsm (both average and median about 0.34 cfsm)
Average annual discharge yields ==> from 1 to 1.8 cfsm (average about 1.3 cfsm, median about 1.2 cfsm)
Application of the above range in yields to the drainage area (556 sqmi) for the point of interest results in the
following estimated low -flow discharges:
Annual 7010 low -flow discharges==> from 16.1 to 133 cfs (average about 89 cfs, median about 94.5 cfs)
Annual 30Q2 low -flow discharges ==> from 111 to 322 cfs (average about 239 cfs, median about 245 cfs)
Winter 7Q10 low -flow discharges==> from 77.8 to 239 cfs (average about 178 cfs, median about 200 cfs)
Annual 7Q2 low -flow discharges==> from 77.8 to 284 cfs (both average and median about 189 cfs)
Average annual discharge discharges==> from 556 to 1001 cfs (average about 723 cfs, median about 667 cfs)
Please note:
(1) The estimated flows are provided n units of cubic feet per second (cfs).
(2) The low -flow yields provided above are rounded to 2 significant figures. Estimated low -flow discharges less
than 1 cfs are rounded to 2 significant figures. If between 1 and 100 cfs, then rounded to 1 decimal place; if
greater than 100, then rounded to the nearest whole number (zero decimal places).
(3) The information provided in this message is based on a preliminary assessment and considered
provisional, subject to revision gending collection of future data and further analv.ses.
These provisional streamflow statistics are provided via the DWR USGS Low Flows cooperative agreement
between the USGS and the N.C. Department of Environmental Quality, Division of Water Resources.
Hope this information is helpful.
Thank you.
Curtis Weaver
J. Curtis Weaver, Hydrologist, PE Email: jcweaver@usg s.g ov
USGS South Atlantic Water Science Center Online: htt/I s;//www.usgs.g ov/centers/sa-water
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6/7/2021 Mail - Denard, Derek- Outlook
North Carolina - South Carolina - Georgia
3916 Sunset Ridge Road
Raleigh, NC 27607
Phone: [phone] II Fax: [phone]
From: Albertin, Klaus P <[e-mail]>
Sent: Thursday, May 27, 2021 4:31 PM
To: Denard, Derek <[e-mail]>
Cc: Albertin, Klaus P <[e-mail]>; Hill, David A <[e-mail]>;
[e-mail]; Weaver, John C <[e-mail]>; Montebello, Michael J
<[e-mail]>
Subject: [EXTERNAL] Low -flow request approval
This email has been received from outside of DOI - Use caution before clicking on links, opening attachments, or
responding.
Your request has been approved and will be forwarded to USGS. A response from USGS usually takes
7 - 10 business days.
Request Flow Statistic Approval
Request ID: 124
Requestor: Derek Denard
Requestor e-mail: [e-mail]
Requestor Phone: [phone]
Local Government:
Public Water Supply:
Consultant:
Contact:
Reason: Permit
River/Stream: South Fork Catawba River
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6/7/2021 Mail - Denard, Derek- Outlook
Drainage Area (sq. mi.): 556
Latitude: 35.3300
Longitude: -81.1328
Other Information: 1342 Dallas Stanley Highway, Dallas, NC
Statististics: ["7Q1OI
Approved by: Albertin, Klaus P
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