HomeMy WebLinkAboutNC0020664_Final Compliance Report for Cu and Ag Limits_20230612Town of Spindale – Final NPDES Monitoring Report on copper and silver 1 | Page
1.0 Introduction and Summary of Actions Taken
The NC Department of Environmental Quality (DEQ) issued NPDES permit number NC0020664 for the
Town of Spindale (Town) WWTP on June 10, 2020, with an effective date of July 1, 2020, and expiry date
of July 31, 2024. PART I contains the following parameters for flow, copper, and silver.
The flow value in the permit is an average monthly design flow value. The total copper and total silver
(copper and silver) values in the permit are in the form of monthly and daily maximum concentrations.
The corresponding loading for copper and silver is provided in the above table for reference only, as
loading values were not stipulated in the NPDES permit. The concentration values for copper and silver
were footnoted in the permit. The footnote requires a compliance schedule in accordance with Section
A. (4.) of the permit. In accordance with this Section, the Town has been monitoring copper and silver of
the WWTP effluent and the wastewater discharged from three significant industry users (SIU). These
SIUs had been identified by the Town staff as likely contributors of copper and silver based on known
characteristics of the processes they employ. A total of 382 samples were collected. The test results were
tracked and analyzed to evaluate NPDES compliance.
This letter is the last required by Section A. (4.). This Section originally required a Corrective Action Plan
(CAP) at this stage in the compliance schedule. However, in ongoing communications with DEQ engineer
Gary Perlmutter, a CAP is no longer required due to the low values that have been previously reported.
As seen in this final compliance letter, the effluent values for copper at the Spindale WWTP are typically
much lower for copper than the Monthly Maximum Concentration limit contained in the permit and
Non-Detect (ND) for silver.
Thus, this last Section A. (4.) letter completes the NPDES requirement concerning copper and silver. We
respectfully wish to communicate to DEQ the Town’s opinion that after considering the results of this
compliance program, numerical limits for copper and silver in the NPDES permit are unwarranted.
2.0 WWTP Monitoring Results
The copper and silver results for the WWTP are presented in Table 1. The staff at the WWTP attempted
to collect copper and silver samples for the WWTP monthly from July 2020 through May 2023; some
monthly samples are missing for 2021. A total of twenty-eight samples were taken and tested. The
minimum reporting level from the available test for copper is 2.0 ug/L; therefore, a value of <2.0 ug/L
represents a non-detectible level of copper. The available test for silver is 0.50 µg; therefore, a value of
<0.50 µg represents a non-detectable level of silver.
Average Monthly Design Flow 3.0 MGD
µg/L lbs./day µg/L lbs./day
Total Copper 45.7 1.1434 53.4 1.3361
Total Silver 0.3 0.0075 1.7 0.0425
Description Monthly Daily
Town of Spindale – Final NPDES Monitoring Report on copper and silver 2 | Page
During the monitoring period, an analytical result for copper, September 15, 2022, of 109.0 ug/L, was
determined to be anomalous because it was uncharacteristically high from all the other values in the
data set. It is possible this test result was inaccurate. This was pointed out in previous compliance letters
to DEQ. Sampling, testing, human, and equipment errors are possible with such a large number of
analytical tests; therefore, the possibility of one or more analytical results being inaccurate is not out of
the question. Split or triplicate sampling was not employed; therefore, it cannot be verified as inaccurate.
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Town of Spindale – Final NPDES Monitoring Report on copper and silver 3 | Page
Table 1 - Spindale WWTP Effluent
FLOW
MGD µg/L lbs./day µg/L2 lbs./day
7/14/2020 0.43 17.1 0.06132 <0.50 ND
8/3/2020 0.66 22.0 0.12110 <0.50 ND
9/15/2020 0.64 109.0 0.58180 <0.50 ND
10/16/2020 0.54 12.4 0.05584 <0.50 ND
11/2/2020 0.63 20.8 0.10929 <0.50 ND
12/3/2020 0.64 23.4 0.12490 <0.50 ND
1/4/2021 0.48 18.3 0.07326 <0.50 ND
2/1/2021 0.65 23.4 0.12685 <0.50 ND
7/6/2021 0.46 39.4 0.15115 <0.50 ND
11/1/2021 0.52 24.1 0.10452 <0.50 ND
12/6/2021 0.51 47.5 0.20204 <0.50 ND
1/3/2022 2.48 21.3 0.44055 <0.50 ND
2/1/2022 0.50 25.0 0.10425 <0.50 ND
3/1/2022 0.50 38.2 0.15929 <0.50 ND
4/5/2022 0.70 30.6 0.17864 <0.50 ND
5/3/2022 0.59 21.1 0.10382 <0.50 ND
6/7/2022 0.49 23.4 0.09563 <0.50 ND
7/5/2022 0.49 24.5 0.10012 <0.50 ND
8/1/2022 0.45 23.6 0.08857 <0.50 ND
9/6/2022 0.44 27.6 0.10128 <0.50 ND
10/3/2022 0.44 24.6 0.09027 <0.50 ND
11/1/2022 0.63 29.8 0.15658 <0.50 ND
12/6/2022 0.58 22.6 0.10932 <0.50 ND
1/3/2023 0.62 10.6 0.05481 <0.50 ND
2/1/2023 0.58 21.7 0.10497 <0.50 ND
3/7/2023 0.54 25.0 0.11259 <0.50 ND
4/3/2023 0.46 14.7 0.05640 <0.50 ND
5/1/2023 0.64 12.2 0.06512 <0.50 ND
Average 0.62 26.9 0.13694 <0.50 ND
2Minimum detection limit for silver is 0.50 µg/L
1The test result in red is suspect. It has been flagged as an anomalous test
result and possibly inaccurate. Split or triplicate sampling were not utilized,
therefore, this cannot be verified.
DATE EFFLUENT COPPER1 EFFLUENT SILVER
Town of Spindale – Final NPDES Monitoring Report on copper and silver 4 | Page
A comparison of the Mean (Average), Median, and Standard Deviation of the WWTP Effluent copper
between the entire data set and the data set without the anomalous test result is provided below. The
difference in Standard Deviation between the two is 9.6.
Charts A and B on the following pages show the effluent copper concentration and mass balance over
time. Chart A reflects the entire data set, while Chart B reflects the data set without the anomalous
result. This visually demonstrates the significant difference between a test result of 109.0 ug/L and the
rest of the data. Chart B shows that of twenty-eight test results from July 2020 through May 2023, only
one sample was higher than the monthly average concentration of 45.7 ug/L. That sample was taken on
December 6, 2021, and the value was 47.5 ug/L, 1.8 ug/L over the limit. The rest of the samples were
well under 45.7 ug/L.
It should be pointed out these Charts showed a large loading on January 3, 2022. This results from a
significant rain event which resulted in an unusually high influent flow of 2.48 MGD. The average flow
without this rain-induced event was 0.55 MGD, a factor of 4.5. Charts A and B show the spike in copper
loading on this day.
The silver concentration in the WWTP effluent was below the detection level of 0.50 µg/L for the entire
sampling period.
WWTP Effluent
Copper
Entire Data Set
with no
Modifications
The Data Set
without the
Anomalous Test
Result
Difference
Δ
Mean (average)26.9 23.9 3.0
Median 23.4 23.4 0.0
Standard Deviation 17.7 8.0 9.6
Town of Spindale – Final NPDES Monitoring Report on copper and silver 5 | Page
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
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Chart A -WWTP Effluent Copper --Entire Data Set
Mo. Conc. 45.7
ug/L
Effluent Copper
Concentration
Effluent Copper
Mass Balance
Town of Spindale – Final NPDES Monitoring Report on copper and silver 6 | Page
3.0 SIU Monitoring Results
The copper and silver results for the SIUs are presented in Tables 2, 3, and 4.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
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Chart B -WWTP Effluent Copper --Without the Anomalous Test
Result
Mo. Conc. 45.7
ug/L
Effluent Copper
Concentration
Effluent Copper
Mass Balance
Town of Spindale – Final NPDES Monitoring Report on copper and silver 7 | Page
Table 2 - Ultimate Textiles (SIU1)
FLOW
MGD µg/L lbs./day µg/L1 lbs./day
4/22/2020 0.029000 24.30 0.005877 3.100 0.00075
5/22/2020 0.060000 24.20 0.01211 <0.50 ND
6/22/2020 0.075000 108.00 0.067554 <0.50 ND
8/12/2020 0.051000 952.00 0.404924 <0.50 ND
9/16/2020 0.054000 589.00 0.265262 2.50 0.00113
10/23/2020 0.058000 2150.00 1.039998 <0.50 ND
11/13/2020 0.069000 80.70 0.04644 <0.50 ND
12/10/2020 0.064000 396.00 0.211369 <0.50 ND
1/22/2021 0.067000 46.00 0.025704 <0.50 ND
2/19/2021 0.052000 105.00 0.045536 <0.50 ND
3/29/2021 0.830000 167.00 1.156007 <0.50 ND
4/22/2021 0.890000 93.70 0.695498 <0.50 ND
5/28/2021 0.076451 170.00 0.108392 <0.50 ND
6/14/2021 0.076000 25.80 0.016353 <0.50 ND
7/16/2021 0.068500 88.30 0.050445 2.90 0.00166
8/23/2021 0.068700 106.00 0.060734 <0.50 ND
9/23/2021 0.031800 3650.00 0.968024 <0.50 ND
10/11/2021 0.056000 1240.00 0.57913 <0.50 ND
11/18/2021 0.053000 128.00 0.056579 <0.50 ND
12/20/2021 0.043000 44.00 0.015779 <0.50 ND
1/26/2022 0.033000 46.3 0.0127 <0.50 ND
2/25/2022 0.038000 2450.0 0.7765 <0.50 ND
3/11/2022 0.049000 111.0 0.0454 <0.50 ND
4/14/2022 0.051000 123.0 0.0523 0.52 0.00022
5/6/2022 0.048000 495.0 0.1982 <0.50 ND
6/16/2022 0.042000 269.0 0.0942 <0.50 ND
7/13/2022 0.058000 28.4 0.0137 <0.50 ND
8/10/2022 0.078000 26.8 0.0174 0.28 0.00018
9/21/2022 0.049000 22.4 0.0092 0.19 0.00008
10/13/2022 0.065000 6.0 0.0033 <0.50 ND
11/2/2022 0.062000 34.3 0.0177 <0.50 ND
12/7/2022 0.063000 188.0 0.0988 0.44 0.00023
1/13/2023 0.047000 471.0 0.1846 <0.50 ND
2/9/2023 0.066000 228.0 0.1255 <0.50 ND
3/16/2023 0.044000 127.0 0.0466 0.60 0.00022
4/13/2023 0.059000 456.0 0.2244 2.60 0.00128
5/18/2023 0.072000 447.0 0.2684 2.30 0.00138
Average 0.099904 424.8 0.2168 0.782 0.00065
1Minimum detection limit for silver is 0.50 µg/L
DATE COPPER SILVER
Town of Spindale – Final NPDES Monitoring Report on copper and silver 8 | Page
Table 3 - Timken (SIU2)
FLOW
MGD µg/L1 lbs./day µg/L2 lbs./day
6/3/2020 0.0170 78.50 0.01113 <0.50 ND
7/8/2020 0.0140 52.00 0.00607 <0.50 ND
8/26/2020 0.0160 36.00 0.00480 <0.50 ND
9/16/2020 0.0120 28.60 0.00286 <0.50 ND
10/28/2020 0.0140 40.20 0.00469 <0.50 ND
12/2/2020 0.0010 26.20 0.00022 <0.50 ND
1/22/2021 0.0010 7.60 0.00006 <0.50 ND
2/23/2021 48.30 <0.50 ND
3/17/2021 0.0090 106.00 0.00796 <0.50 ND
7/30/2021 0.0140 20.20 0.00236 <0.50 ND
8/20/2021 0.0170 24.00 0.00340 <0.50 ND
9/22/2021 0.0110 71.00 0.00651 <0.50 ND
12/8/2021 0.0100 <2.0 ND <0.50 ND
2/16/2022 0.0064 <2.0 ND <0.50 ND
3/23/2022 0.0060 21.90 0.00110 <0.50 ND
4/27/2022 0.0078 <0.50 ND
5/18/2022 0.0240 <0.50 ND
6/13/2022 0.0270 140.00 0.03153 <0.50 ND
7/20/2022 0.0200 25.90 0.00432 <0.50 ND
8/23/2022 0.0150 9.40 0.00118 <0.50 ND
9/29/2022 0.0170 23.00 0.00326 <0.50 ND
10/7/2022 0.0150 20.00 0.00250 <0.50 ND
11/17/2022 0.0140 6.00 0.00070 <0.50 ND
12/12/2022 0.0120 26.00 0.00260 <0.50 ND
1/11/2023 0.0090 19.00 0.00143 <0.50 ND
2/28/2023 0.0100 33.00 0.00275 <0.50 ND
3/20/2023 0.0100 37.00 0.00309 <0.50 ND
4/26/2023 0.0130 35.00 0.00379 <0.50 ND
5/10/2023 0.0100 26.00 0.00217 <0.50 ND
Average 0.0126 38.43 0.00460 <0.50 ND
1Minimum detection limit for copper is 2.0 µg/L
2Minimum detection limit for silver is 0.50 µg/L
DATE COPPER SILVER
Note: The gray cells indicate missing data.
Town of Spindale – Final NPDES Monitoring Report on copper and silver 9 | Page
Table 4 - Spindale Mills (SIU3)
FLOW
MGD µg/L1 lbs./day µg/L2 lbs./day
4/3/2020 0.0350 14.000 0.00409 <0.50 ND
5/22/2020 0.0500 23.000 0.00959 <0.50 ND
7/30/2020 0.0640 12.000 0.00641 <0.50 ND
8/11/2020 0.0880 84.300 0.06187 <0.50 ND
9/16/2020 0.0640 12.400 0.00662 <0.50 ND
11/10/2020 0.0610 0.130 0.00007 <0.50 ND
12/11/2020 0.1540 30.900 0.03969 <0.50 ND
2/16/2021 0.1440 13.000 0.01561 <0.50 ND
3/29/2021 0.1100 430.000 0.39448 <0.50 ND
4/14/2021 0.1420 63.500 0.07520 <0.50 ND
5/13/2021 0.0626 199.000 0.10389 <0.50 ND
6/10/2021 0.0900 123.000 0.09232 <0.50 ND
7/20/2021 0.0649 19.900 0.01077 <0.50 ND
8/18/2021 0.1020 38.600 0.03284 <0.50 ND
9/2/2021 0.0520 14.700 0.00638 <0.50 ND
10/21/2021 0.0080 172.000 0.01148 <0.50 ND
11/16/2021 0.0200 68.800 0.01148 <0.50 ND
12/14/2021 0.1140 0.012 0.00001 <0.50 ND
1/21/2022 0.0950 161.000 0.12756 <0.50 ND
2/10/2022 0.1010 196.000 0.16510 <0.50 ND
4/13/2022 0.0810 16.500 0.01115 <0.50 ND
5/11/2022 0.0500 31.900 0.01330 <0.50 ND
6/24/2022 0.0880 2.500 0.00183 <0.50 ND
7/15/2022 0.0830 16.800 0.01163 <0.50 ND
8/18/2022 0.0480 161.000 0.06445 <0.50 ND
9/20/2022 0.0490 222.000 0.09072 <0.50 ND
10/12/2022 0.0900 76.000 0.05705 <0.50 ND
11/15/2022 0.1600 <2.0 ND <0.50 ND
12/13/2022 0.140 65.30 0.0762 <0.50 ND
1/31/2023 0.160 16.80 0.0224 <0.50 ND
2/14/2023 0.088 21.20 0.0156 <0.50 ND
3/14/2023 0.150 19.20 0.0240 <0.50 ND
4/25/2023 0.008 118.00 0.0079 <0.50 ND
Average 0.085 76.36 0.0491 <0.50 ND
1Minimum detection limit for copper is 2.0 µg/L
2Minimum detection limit for silver is 0.50 µg/L
DATE COPPER SILVER
Town of Spindale – Final NPDES Monitoring Report on copper and silver 10 | Page
Chart 3 shows the mass balance for copper loading for the WWTP and the three SIUs.
The SIU silver and copper contributions were combined in Table 5 in a headworks analysis.
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
1.4000
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Chart 3 -Copper Mass Balance
Headworks Mass Balance
WWTP Mass Balance
Ultimate Textiles
Timken
Spindale Mills
Table 5 - Combined SIUs
Flow
MGD µg/L lbs./day µg/L lbs./day
Table 2 - Ultimate Textiles (SIU1)0.0999 424.79 0.2168 0.782 0.00065
Table 3 - Timken (SIU2)0.0126 38.43 0.0046 <0.50 ND
Table 4 - Spindale Mills (SIU3)0.0853 76.36 0.0491 <0.50 ND
Subtotal 0.1978 0.2705 0.00065
% of NPDES Limits 6.6%23.7%8.7%
Avg. Influent SilverAvg. Influent CopperSignificant Industry User (SIU)
Town of Spindale – Final NPDES Monitoring Report on copper and silver 11 | Page
The results of Table 5 are summarized below.
• The SIUs combined represent 6.6% of the WWTP’s permitted average monthly design flow of
3.0 MGD.
• The SIUs combined represent 23.7% of the WWTP’s loading for copper of 1.1434 lbs./day.
• The SIUs combined represent 8.7% of the WWTP’s loading for silver of 0.00751 lbs./day.
It can be seen that the SIUs combined represent a small percentage of the WWTP’s permitted flow and
copper and silver loading.
4.0 Conclusions
An analysis of the sampling and testing for copper and silver in accordance with Section A. (4.) of the
NPDES permit yields the following conclusions:
• The copper sample taken on September 15, 2020, was 109.0 ug/L and is considered an anomaly.
The accuracy of this test result is suspect.
• The copper sample taken on December 6, 2021, was 47.5 ug/L, just 1.8 ug/L over the NPDES
permit limit of 45.7 ug/L. All the other copper samples (minus the anomalous sample) were well
under 45.7 ug/L.
• The WWTP predominantly complies with the copper limit of 45.7 ug/L. As such, the Town
argues that a numerical value for copper in its NPDES is unnecessary.
• The WWTP is compliant with silver as all the silver samples were ND. As such, there is no need
for the NPDES permit to contain a numerical value for silver in its permit.
• The three SIUs identified by the Town as the primary contributors of silver and copper represent
a small percentage of the WWTP’s permitted flow and copper and silver loading.
• A Corrective Action Plan (CAP) for copper and silver is unnecessary.
It is the Town’s opinion that monthly concentration limits for copper and silver are unwarranted.
This letter fulfills all the requirements in the Schedule of Compliance specified in Section A. (4.) of the
NPDES permit.