#5207_2019_1105_TS_FINAL

Laboratory Cert. #:
5207
Laboratory Name:
Town of St. Pauls WWTP
Inspection Type:
Field Municipal Maintenance
Inspector Name(s):
Tonja Springer
Inspection Date:
11/5/2019
Date Forwarded for Initial
12/4/2019
Review:
Initial Review by:
JMS
Date Initial Review
12/4/2019
Completed:
❑ Insp. Initial
❑ Insp. Reg
Cover Letter to use:
❑Insp. No Finding
❑Corrected
❑Insp. CP
®Insp. Reg. Delay
(to use: rt click, properties, chock)
Unit Supervisor/Chemist III:
Todd Crawford
Date Received:
12/10/2019
Date Forwarded to Admin.:
12/16/2019
Date Mailed:
12/17/2019
Special Mailing Instructions:
Include a copy of the most recent AP for DO and TRC by SM4500 CI G.

P,OY COOPER
MIC14ALL S, REGAi
dri rc Ket`+ On c.,"tof
5207
Mr. Timothy Lyde
Town of St. Pauls WWTP
P.O. Box 364
St. Pauls, NC 28384
NORt[A CA OLIridA
Environmental Quart}
December 17, 2019
Subject: North Carolina Wastewater/Groundwater Laboratory Certification (NC WW/GW LC)
Maintenance Inspection
Dear Mr. Lyde:
Enclosed is a report for the inspection performed on November 5, 2019 by Tonja Springer. I apologize for
the delay in getting this report to you. Where Finding(s) are cited in this report, a response is required.
Within thirty days of receipt, please supply this office with a written item for item description of how these
Finding(s) were corrected. Please describe the steps taken to prevent recurrence and include an
implementation date for each corrective action. If the Finding(s) cited in the enclosed report are not
corrected, enforcement actions may be recommended. For Certification maintenance, your laboratory
must continue to carry out the requirements set forth in 15A NCAC 2H .0800.
A copy of the laboratory's Certified Parameter List at the time of the audit is attached. This list will reflect
any changes made during the audit. Copies of the checklists completed during the inspection may be
requested from this office. Thank you for your cooperation during the inspection. If you wish to obtain an
electronic copy of this report by email or if you have questions or need additional information, please
contact me at [phone].
Sincerely,
Todd Crawford
Technical Assistance & Compliance Specialist
NC WW/GW Laboratory Certification Branch
Attachment
cc: Dana Satterwhite, Tonja Springer, Master File #5207
Noah Carolina Department of Environmental Quality j Division of Water Resources
1623 Mail Service Center i Raleigh. North Carolina 27699-1623
Phone [phone]/Fax 919.733,6241

LABORATORY NAME: Town of St. Pauls WWTP
NPDES PERMIT : NC0020095
ADDRESS: 601 South Elizabeth Street
St. Pauls, NC 28384
CERTIFICATE #: 5207
DATE OF INSPECTION: November 5, 2019
TYPE OF INSPECTION: Field Municipal Maintenance
AUDITOR(S): Tonja Springer
LOCAL PERSON(S) CONTACTED: Timothy Lyde
INTRODUCTION:
This laboratory was inspected by a representative of the North Carolina Wastewater/Groundwater
Laboratory Certification (NC WW/GW LC) program to verify its compliance with the requirements
of 15A NCAC 2H .0800 for the analysis of compliance monitoring samples.
II. GENERAL COMMENTS:
The laboratory was neat and has all the equipment necessary to perform the analyses. Staff was
forthcoming and responded well to suggestions from the auditor.
All required Proficiency Testing (PT) Samples have been analyzed for the 2019 PT Calendar Year
and the graded results were 100% acceptable.
Contracted analyses are performed by TBL (Certification # 37) and Pace Analytical Services, LLC
- Asheville NC (Certification #40).
Approved Procedure documents for the analysis of the facility's currently certified Field
Parameters were provided at the time of the inspection.
I11. FINDINGS, REQUIREMENTS, COMMENTS AND RECOMMENDATIONS:
Documentation
Comment: The statement on the pH and Temperature benchsheets, "Sample measured directly
in the stream only time analyzed is recorded", does not apply and must be removed since
samples are collected and brought back to the lab for analysis.

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#5207 Town of St. Pauls WWTP
Comment: The statement on the Dissolved Oxygen (DO) benchsheet, "Analysis time and
sampling time the same", does not apply and must be removed since samples are collected and
brought back to the lab for analysis.
Recommendation: While 15A NCAC 2H .0805 (e) (5) requires that reported data associated
with quality control failures, improper sample collection, holding time exceedances, or improper
preservation shall be qualified as such, it is recommended that any informational qualifiers also
be reported so that the end user can fully assess the reported data. An example of this would
be the 1631 E qualifier from the client report Project #92412822 for January 7, 2019 explaining
that the sample was diluted due to the presence of high levels of target analytes. This
information would be documented in the comments section on the DMR.
A. Finding: Error corrections are not properly performed.
Requirement: All documentation errors shall be corrected by drawing a single line through
the error so that the original entry remains legible. Entries shall not be obliterated by
erasures or markings. Wite-Out®, correction tape, or similar products designed to
obliterate documentation are not to be used; instead the correction shall be written
adjacent to the error. The correction shall be initialed by the responsible individual and the
date of change documented. Ref: 15A NCAC 2H .0805 (g) (1).
Comment: Error corrections are not dated.
B. Finding: The laboratory needs to increase the traceability documentation of purchased
materials and reagents. This is considered pertinent data.
Requirement: Chemical containers shall be dated when received and when opened.
Reagent containers shall be dated, identified, and initialed when prepared. Chemicals and
reagents exceeding the expiration date shall not be used. Chemicals and reagents shall
be assigned expiration dates by the laboratory if not given by the manufacturer. If the
laboratory is unable to determine an expiration date for a chemical or reagent, a one-year
time period from the date of receipt shall be the expiration date unless degradation is
observed prior to this date. The laboratory shall have a documented system of traceability
for all chemicals, reagents, standards, and consumables. Ref: 15A NCAC 2H .0805 (g)
(7)•
Comment: This finding applies to Total Residual Chlorine (TRC).
Requirement: All chemicals, reagents, standards and consumables used by the
laboratory must have the following information documented: Date Received, Date Opened
(in use), Vendor, Lot Number, and Expiration Date (where specified). A system (e.g.,
traceable identifiers) must be in place that links standard/reagent preparation information
to analytical batches in which the solutions are used. Documentation of solution
preparation must include the analyst's initials, date of preparation, the volume or weight of
standard(s) used, the solvent and final volume of the solution. This information as well as
the vendor and/or manufacturer, lot number, and expiration date must be retained for
primary standards, chemicals, reagents, and materials used for a period of five years.
Consumable materials such as pH buffers and lots of pre -made standards and/or media
solids and bacteria filters, etc. are included in this requirement. Ref: NC WW/GW LC
Policy.
Comment: Dates received and opened were written on the TRC DPD reagent packages
but not on the benchsheet. While this can provide a traceability link to analyses by looking

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#5207 Town of St. Pauls WWTP
at the dates that the chemicals were in use, that link is lost once the bottles are discarded.
A reagent receipt log was provided to the laboratory at the time of inspection.
C. Finding: Documentation of the calibration variables for the DO meter does not include all
pertinent data.
Requirement: All analytical records, including original observations and information
necessary to facilitate historical reconstruction of the calculated results, shall be
maintained for five years. All analytical equipment, data and records pertinent to each
certified analysis shall be available for inspection upon request. Ref: 15A NCAC 2H
.0805 (g) (1).
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: Calibration variables (temperature, elevation or barometric pressure
fin mmHg] and salinity). Ref: NC WW/GW LC Approved Procedure for the Analysis of
Dissolved Oxygen.
Comment: Only temperature is documented.
D. Finding: The laboratory benchsheets are lacking pertinent data: instrument identification.
Requirement: All laboratories shall use printable benchsheets. Certified Data shall be
traced to the associated sample analyses and shall consist of: the instrument
identification. Each item shall be recorded each time samples are analyzed. Ref: 15A
NCAC 2H .0805 (g) (2) (C).
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: Instrument identification (serial number preferred). Ref: NC
WW/GW LC Approved Procedure for the Analysis of Total Residual Chlorine (DPD
Colorimetric), NC WW/GW LC Approved Procedure for the Analysis of Dissolved Oxygen,
NC WW/GW LC Approved Procedure for the Analysis of pH and NC WW/GW LC
Approved Procedure for the Analysis of Temperature.
Comment: This Finding applies to DO, pH, Temperature and TRC.
Comment: A digital Thermometer is being used for the analysis of the Stream Samples
which are documented on the Operator's daily log. The instrument ID for the thermometer
will need to be documented on the daily log.
E. Finding: The laboratory benchsheet for TRC is lacking pertinent data: true value of the
Daily Check Standard, percent recovery of the Daily Check Standard and date of most
recent calibration curve verification.
Requirement: All laboratories shall use printable benchsheets. Certified Data shall be
traced to the associated sample analyses and shall consist of: the quality control
assessments. Each item shall be recorded each time samples are analyzed. Ref: 15A
NCAC 2H .0805 (g) (2) (0).
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: true value of the Daily Check Standard, percent recovery of the
Daily Check Standard, date of most recent calibration curve verification. Ref: NC
WW/GW LC Approved Procedure for the Analysis of Total Residual Chlorine (DPD
Colorimetric).

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#5207 Town of St. Pauls WWTP
Comment: The benchsheet provides a space for the date of the most recent curve and
the true value of the Daily Check Standard to be documented but they are not being
utilized.
Comment: The laboratory is not documenting the percent recovery of the Daily Check
Standard to demonstrate the analytical process is in control and the established
acceptance criterion is being met.
F. Finding: The laboratory benchsheet for Temperature is lacking required documentation:
parameter analyzed and method reference.
Requirement: All laboratories shall use printable benchsheets. Certified Data shall be
traced to the associated sample analyses and shall consist of: the method. Each item
shall be recorded each time samples are analyzed. Ref: 15A NCAC 2H .0805 (g) (2) (A).
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: parameter analyzed, method reference. NC WW/GW LC Approved
Procedure for the Analysis of Temperature.
Comment: Temperature is being analyzed on the pH meter. The pH method reference is
documented but not the Temperature method.
Comment: Temperature results are being documented in the comments section of the
benchsheet.
Quality Control
G. Finding: The laboratory is not calibrating the mechanical volumetric liquid -dispensing
devices used for critical measurements at least once every 12 months.
Requirement: Mechanical volumetric liquid -dispensing devices (e.g., fixed and adjustable
auto-pipettors and bottle -top dispensers) shall be calibrated at least once every twelve
months. Ref: 15A NCAC 2H .0805 (g) (10).
Comment: The pipette is used in the TRC PT Sample preparation.
Proficiency Testing
H. Finding: The laboratory is not documenting PT Sample analyses in the same manner as
routine Compliance Samples.
Requirement: All PT Sample analyses must be recorded in the daily analysis records as
for any Compliance Sample. This serves as the permanent laboratory record. Ref:
Proficiency Testing Requirements, October 29, 2018, Revision 3.
Requirement: The laboratory shall retain all records necessary to facilitate historical
reconstruction of the analysis and reporting of analytical results for PT Samples. This
means the laboratory must have available and retain for five years [pursuant to 15A NCAC
2H .0805 (a) (7) (G)] all of the raw data, including benchsheets, instrument printouts and
calibration data, for all PT Sample analyses and the associated QC analyses conducted
by all parameter methods. Ref: Proficiency Testing Requirements, October 29, 2018,
Revision 3.

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#5207 Town of St. Pauls WWTP
Comment: PT Samples are only documented on the PT vendor reporting form.
Finding: The laboratory is not documenting the preparation of PT Samples.
Requirement: PT Samples received as ampules are diluted according to the Accredited
PT Sample Provider's instructions. It is important to remember to document the
preparation of PT Samples in a traceable log or other traceable format. The diluted PT
Sample then becomes a routine Compliance Sample and is added to a routine sample
batch for analysis. No documentation is needed for whole volume PT Samples which
require no preparation (e.g., pH), but it is recommended that the instructions be
maintained. Ref: Proficiency Testing Requirements, October 29, 2018, Revision 3.
Comment: The preparation of TRC PT Samples is not fully documented. The laboratory
was retaining the instruction sheets for PT Sample preparations, however, they were not
dating and initialing them.
Comment: Dating and initialing the instruction sheet for the preparation of the Total
Residual Chlorine PT Sample would satisfy the documentation requirement.
Chlorine, Total Residual — Standard Methods, 4500 Cl G-2011 (Aqueous)
J. Finding: The laboratory is not analyzing a Water Blank, when applicable.
Requirement: If preparing standards, analyzing a PT Sample or analyzing diluted
samples, a Reagent Blank is required. Ref: NC WW/GW LC Approved Procedure for the
Analysis of Total Residual Chlorine (DPD Colorimetric).
Requirement: The concentration of the reagent blank must not exceed 50% of the
reporting limit (i.e., the lowest calibration or calibration verification standard concentration),
unless otherwise specified by the reference method, or corrective action must be taken.
Ref: NC WW/GW LC Approved Procedure for the Analysis of Total Residual Chlorine
(DPD Colorimetric).
Comment: A Water Blank is not analyzed with the PT Sample.
Comment: Since the inspection, the Approved Procedure for the Analysis of Total
Residual Chlorine (DPD) Colorimetric has been updated. A copy is attached.
Dissolved Oxygen — Standard Methods, 4500 O G-2011 (Aqueous)
Comment: The DO meter is being calibrated using the Air -Saturated Water technique. The
manufacturer states this has been proven an uncertain method, as it is difficult to secure a stable
saturation.
Recommendation: It is recommended that the laboratory switch to the Air Calibration technique.
This is the quickest and simplest calibration technique and is recommended by the YSI
manufacturer. To calibrate the YSI 58, the function switch is set to the percent saturation mode
with the probe in moist air; then the 02 CALIB control is adjusted to obtain a meter reading
corresponding to the calibration value for the local altitude. Charts for quickly determining the

Page 6
#5207 Town of St. Pauls WWTP
calibration values can be found in Appendix F, Calibration Values Table. This simple procedure
accurately calibrates the meter for readings in both the mg/L and the percent saturation modes.
The instrument may be switched from one mode to the other without losing its calibration. Ref:
YSI 58 Operator's Manual.
Comment: Since the inspection the Approved Procedure for the Analysis of Total Residual
Chlorine (DPD) Colorimetric has been updated. A copy is attached.
pH - Standard Methods, 4500 H+ B-2011 (Aqueous)
K. Finding: Values are reported that exceed the method specified accuracy of 0.1 units.
Requirement: By careful use of a laboratory pH meter with good electrodes, a precision
of ±0.02 unit and an accuracy of ±0.05 unit can be achieved. However, ± 0.1 pH unit
represents the limit of accuracy under normal conditions, especially for measurement of
water and poorly buffered solutions. For this reason, report pH values to the nearest 0.1
pH unit. Ref: Standard Methods, 4500 H+ 8-2011. (6).
Requirement: Values must be reported in tenths (0.1). Ref: NC WW/GW LC Approved
Procedure for the Analysis of pH.
Recommendation: The laboratory currently reports pH sample results to two decimal
places. It is recommended that the laboratory continue to measure and document sample
results on the benchsheet to two decimal places, and to round to the nearest 0.1 S.U.
when reporting results on the Discharge Monitoring Report (DMR).
Comment: Per PT Vendor instructions, the PT Sample results should continue to be
reported to two decimal places.
Temperature - Standard Methods, 2550 B-2010 (Aqueous)
Recommendation: It is recommended that Temperature results be reported on the DMR in whole
numbers, as stated in the "Precision in Discharge Monitoring Reports" document issues by the
Division of Water Resources.
U a F-, I: j A a i 14 1 z n *-I-iI . iiC] A
The paper trail consisted of comparing original records (e.g., laboratory benchsheets, logbooks,
etc.) and contract lab reports to Discharge Monitoring Reports (DMRs) submitted to the North
Carolina Division of Water Resources. Data were reviewed for Town of St. Pauls WWTP
(NPDES permit # NC0020095) for January, June and September 2019. The following errors
were noted:
Date
Parameter
Location
Value on Benchsheet
Value on DMR
1/18/2019
TRC
Effluent
< 20 pg/L
20 pg/L
1/23/2019
Temperature
Effluent
13 °C
23 °C
1/25/2019
TRC
Effluent
< 20 pg/L
20 pg/L
1/29/2019
TRC
Effluent
< 20 pg/L
20 pg/L

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#5207 Town of St. Pauls WWTP
6/7/2019
TRC
Effluent
< 20 pg/L
20 pg/L
6/13/2019
TRC
Effluent
< 20 pg/L
20 pg/L
6/14/2019
TRC
Effluent
< 20 pg/L
20 pg/L
6/18/2019
TRC
Effluent
< 20 pg/L
20 pg/L
6/21/2019
TRC
Effluent
< 20 pg/L
20 pg/L
6/24/2019
Temperature
Effluent
27 °C
26 °C
6/26/2019
TRC
Effluent
< 20 pg/L
20 pg/L
9/6/2019
TRC
Effluent
< 20 pg/L
20 pg/L
9/16/2019
TRC
Effluent
< 20 pg/L
20 pg/L
9/20/2019
TRC
Effluent
< 20 pg/L
20 pg/L
To avoid questions of legality, it is recommended that you contact the appropriate Regional
Office for guidance as to whether an amended DMR(s) will be required. A copy of this report
will be made available to the Regional Office.
V. CONCLUSIONS:
Correcting the above -cited Findings and implementing the Recommendations will help this
laboratory to produce quality data and meet Certification requirements. The inspector would like
to thank the staff for their assistance during the inspection and data review process. Please
respond to all Findings and include supporting documentation, implementation dates
and steps taken to prevent recurrence for each corrective action.
Report prepared by:
2019
Report reviewed by:
2019
Tonja Springer
Jason Smith
Date: December 4,
Date: December 4,

This document provides an approved procedure for the analysis of DO for compliance monitoring per 15A
NCAC 2H .0805 (a) (7) and (g) (4).
1 0 Eel 1111l[��li�il
• Samples must be analyzed within 15 minutes of collection (40 CFR Part 136 Table II); however, in situ or
immediate analysis is recommended due to the unstable nature of dissolved oxygen in samples.
GENERAL INFORMATION:
• Types of probes:
a. Dissolved Oxygen Membrane Electrode
b. Luminescence Dissolved Oxygen (LDO) Sensor
• Instrument Warm-up Times: Galvanic sensors require no warm-up time. Polarographic sensors require a
15-minute warm-up time. Optical sensors require no warm-up time.
• Movement of water across the membrane (for membrane electrode technologies) is important for
accurate readings. Some probes come with stirrers for this purpose. Measurements should be taken
while the stirrer is in use or by swirling the DO probe in the sample flow. Preferably, insert the probe into
flowing conditions. If analyzed in a container, stir gently with the probe or add a stir bar. Do not put the
probe on the sides or the bottom of the container.
• Movement across the sensor is not required for LDO probes.
• Follow the manufacturer's instructions for probe storage.
• Sample duplicates are not a required quality control element for Field parameters.
METER CALIBRATION:
• Instruments are to be calibrated according to the manufacturer's calibration procedure prior to analysis of
samples each day compliance monitoring is performed.
• The laboratory must use moist air for the air calibration. This is accomplished by calibrating the electrode
in an environment with a high relative humidity. Using dry air for the calibration can result in errant
readings.
• The laboratory must document each time that a calibration is performed. Calibration documentation must
include the instrument identification as well as the temperature, the elevation or barometric pressure (in
mmHg), and the salinity of the sample to be analyzed. After calibration, record the final DO reading in
mg/L or % saturation.
NOTE: Meters that also measure Conductivity may convert the Conductivity reading to Salinity to
use in the DO calibration. If the meter operates in that manner, it must be calibrated for Conductivity
before being calibrated for DO. If salinity is manually entered by the user during calibration and more
than one sample is analyzed, the meter must be recalibrated using the salinity of each new sample.
• For LDO sensors that cannot be calibrated by the user, the internal calibration must be verified each day
of use. This can be performed by back calculating the theoretical DO for the current air calibration
conditions (e.g., temperature, elevation, barometric pressure, etc.). The calculated DO value must verify
the meter reading within ±0.5 mg/L. Refer to the Dissolved Oxygen Meter Calibration Verification handout
Rev. 12/06/2019

at the end of this document. If the meter verification does not read within ±0.5 mg/L of the theoretical DO,
corrective action must be taken.
® When performing analyses at multiple sample sites, the meter must be calibrated at each sample site
prior to analysis or a post -analysis calibration verification must be performed at the end of the run,
regardless of meter type. The calculated theoretical DO value must verify the meter reading within ±0.5
mg/L. If the meter verification does not read within ±0.5 mg/L of the theoretical DO, corrective action must
be taken. If the meter is not calibrated at each sample site, it is recommended that a mid -day calibration
be performed when samples are extended over an extended period of time.
DOCUMENTATION:
The following must be documented in indelible ink whenever sample analysis is performed.
1. Date and time of sample collection
2. Date and time of sample analysis to verify the 15-minute holding time is met. Alternatively, one time
may be documented for collection and analysis with the notation that samples are measured in situ
or immediately at the sample site
3. Facility name, sample site (ID or location), and permit number
4. Collector's/analyst's name or initials
5. Conductivity calibration standard and check standard values and check standard evaluation, if
applicable.
6. Calibration variables (temperature, elevation or barometric pressure [in mmHg], and salinity)
7. Meter calibration and/or verification date and time(s)
8. Final calibration information (final DO reading in mg/L or % saturation)
9. Theoretical value and DO meter reading for the calibration verification(s), where applicable
10. Units of measure
11. Instrument identification (serial number preferred)
12. Parameter analyzed
13. Method reference
14. Data qualifier(s), when applicable
15. Equipment maintenance (recommended)
Ref: Standard Methods 4500-0 G - 2011
Hach Method 10360, Rev. 1.2, October 2011
In Situ Method 1002-8-2009
ASTM Method D888-09 (B)
ASTM Method D888-09 (C)
Rev. 12/06/2019

Dissolved Oxygen Meter Calibration Verification When Salinity is Zero
DO meters/probes must be calibrated each day of use prior to sample analysis. If the meter cannot be calibrated, the calibration must be verified each day of use.
Additionally, when performing DO analyses at multiple sample sites, a post analysis calibration verification must be analyzed at the end of the run for all types of DO
probes, unless the meter is recalibrated at each sample site. Below is a procedure for verifying the calibration of a DO probe.
1) Follow the manufacturer's instructions for meter operation.
2) Place probe in a plastic bag, the probe storage cup, the storage well of the meter (each containing a wet sponge), or a BOD bottle partially filled with water. Allow
appropriate instrument warm up time.
3) Read DO and temperature.
4) Check the temperature vs. DO mg/L table below and apply appropriate atmospheric (barometric) pressure or altitude correction factor.
5) Calculated (theoretical) DO value must verify meter reading within ± 0.5 mg/L.
Temp. °C
DO m /L
Temp. °C
DO m /L
4,0
13.11
19.5
9.18
4.5
12.94
20.0
9.09
5.0
12.77
20.5
9.00
5.5
12.61
21.0
8.92
6.0
12.45
21.5
8.83
6.5
12.30
22.0
8.74
7.0
12.14
22.5
8,66
7.5
11.99
23.0
8.58
8.0
11.84
23.5
8.50
8.5
11.70
24.0
8.42
9.0
11.56
24.5
8.34
9.5
11.42
25.0
8.26
10.0 <'
11.29
25.5
8.18
10.5
11.16
26.0
8.11
11.0 '
11,03
26.5
8.04
11.5
10.90
27.0
7.97
12.0
10.78
27.5
7,90
12.5
10.66
28.0
7.83
13.0
10,64
28.5
7.76
13.5
10.42
29.0
7.69
14.0 :
10.31
29.5
7.62
14.5
10.20
30.0
7.56
15.0
10.08
30.5
750
15.5
9.98
31.0
7.43
16.0 `
9.87
31.5
7,37
16.5
9.77
32.0
7.31
17.0
9.67
32.5
7.24
17.5
9.57
33.0
7.18
18.0 :
9.47
33.5
7.12
18.5
9.38
34.0
7.07
1910 '
9.28
34.5
7.01
Atmospheric Pressure mm Hg
Equivalent Altitude Ft.
Correction Factor
760
0
1.00
752
278
.99
745
558
.98
737
841
.97
730
1126
.96
722
1413
.95
714
1703
.94
707
1995
.93
699
2290
.92
692
2587
.91
684
2887
.90
676
3190
.89
669
3496
.88
661
3804
.87
654
4115
.86
646
4430
.85
638
4747
.84
631
5067
.83
623
5391
.82
616
5717
.81
608
6047
.80
600
6381
.79
593
6717
.78
Ref: YSI Model 5000/5100 DO Meter Manual. Slight variations In DO, pressure, and/or altitude maybe found in other manuals.
Example: If ambient temperature is 21 °C and elevation is approximately 1126 ft, the
theoretical DO would be:
8.92 X 0.96 = 8.56 mg/L
or, if ambient temperature is 21 °C and the atmospheric (barometric) pressure is 745 mm Hg, the
theoretical DO would be:
8.92 X 0.98 = 8.74 mg/L

Dissolved Oxygen Meter Calibration Verification When Salinity is Greater Than Zero
If calibrated at a salinity greater than zero, use the following table and column with applicable salinity:
Tablet - OXYGEN
SOLU, BI LITY TABLE
Sdubility of Oxygen in ntg/L in e:oter expo,ed to wotersakroled air at
760 mrrRgg p-ensure-.
Temp
01G. Wty: 0
5.aliniry: 0
5.0 ppi
9.0 ppt
10.0 pp-,
18.1 pW
150 ppi
27.1 p,,A
20.0 ppt
36A ppt
25.0 ppi
45.2 ppi
00
14.621
11726
12.888
12.097
11.355
T0:657
1.0
14.216
13,356
12.545
11.783
11.066
10.392
2.0
T 3.929
13.000
12.218
11.483
10.790
I 0.139
3.0
13.460
12.660
11.906
11.195
10.526
9.897
4.0
13.107
12.335
11.607
10.920
10.273
9.664
5.0
12770
12.024
11.320
10.656
10.031
9.441
6.0
12.447
11127
11.046
10,404
9,799
9.228
7.0
12.139
11.442
10.783
10.162
9.576
9.023
8.0
11.843
11.169
10.531
9.930
9.362
8.826
9.0
11.559
10.907
10.290
9,707
9.156
8.636
10.0
11288
10.656
10.058
9.493
8.959
8.454
11.0
10.027
10.415
9.835
9287
6.769
8.279
12.0
10.777
10.183
9.621
9.089
8.586
8.111
13.0
10.537
9.961
9.416
8.899
8.411
7.949
14.0
T0.306
9.747
9,210
8.716
8.242
7.792
15.0
10.084
9.541
9.027
8.540
8.079
7.642
16.0
9.870
9.344
8.844
8.370
7.922
7.496
17.0
9.665
9.153
8.667
6.207
7.770
7.356
Wo
9.467
8.969
9.497
8.049
7.624
7.221
19.0
9.276
8.792
8.333
17.896
7.483
7..090
20.0
9.092
8.62I
8.174
7.749
7.346
6.964
21.0
8.915
8.456
8.021
7.607
7.214
6.842
22.0
8.743
0.297
7.873
7.470
7.087
16.723
23.0
8.578
8.143
7.730
7.337
6,963
6.609
24.0
8.418
7.994
7.591
7.208
6.844
16.498
Rev.12/06/2019
Temp
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19.1 ppt
15.0 ppt
27.1 ppt
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45.2 ppi
25.0
8.263
7,950
7.457
7.093
6.728
6.390
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8.113
7.711
7.327
6.962
6.615
6.285
27 0
7.968
7.575
7.201
6.845
6.506
6.184
28.0
7.827
7.444
7.079
6.731
6.400
6.005
29,0
7.691
7.317
6961
6.621
6.297
5.990
MG
7.559
7.194
6.845
6.513
6. 197
5.896
31.0
7,430
7.073
6.733
6.409
6.100
5.806
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7.305
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6.624
6.307
6.005
5.717
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6.843
6.518
6.208
5.912
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5.822
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6.314
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5.734
5.464
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6.519
6215
5.925
5.648
5.384
37.0
6.727
6.416
6,119
5.835
5.564
5.305
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6.316
6.025
5.747
5.481
5.228
39.0
6.515
b.217
5.932
5.660
5.400
5.152
40.0
6.412
6,121
5,842
5.576
5.321
5.078
41.0
6.312
6.026
5.753
5.493
5.243
5.005
42.0
6.213
5.934
5 667
5.411
5.167
4.993
43.0
6.116
5.943
5.581
5.331
5,091
4.861
44.0
6,021
5.753
5.497
5.252
5.017
4.793
45.0
5,927
5,665
5414
5,174
4.944
4.724
46,0
5.835
5,578
5,333
5.097
4.872
4.656
47.0
5.744
5.493
5,252
5.021
4.801
48.0
5.654
5,408
5.172
4.947
4.730
49.0
5.565
5.324
5.094
4.872
4.660
44�457
50.0
5.477
5.242
5.016
4.799
4.591
Reference: The Dissolved Oxygen Handbook. YSI, Incorporated, September 2009.

PROCEDURE FOR THE ANALYSIS OF TOTAL RESIDUAL CHLORINE
This document provides an approved procedure for the colorimetric analysis of Total Residual Chlorine (TRC) for compliance
monitoring per 15A NCAC 2H .0805 (a) (7) and (g) (4).
Holding Time:
Samples must be analyzed within 15 minutes of collection (40 CFR Part 136 Table II). Sample analysis begins
when the reagents are added to the sample.
General Information:
If there is a Daily Maximum Limit required by the facility permit, you must have an instrument capable of detecting
concentrations below that level, such as a spectrophotometer or filter photometer. Per 15A NCAC 02B .0505 (e) (4),
facilities must produce detection and reporting levels that are below the Daily Maximum Limit.
NOTE: Even though permits for stormwater monitoring do not have Daily Maximum Limits, stormwater
permittees must use an instrument and analytical method capable of detecting concentrations below the
specified stormwater benchmark concentration of 28 pg/L to properly assess pollutants and the
effectiveness of Best Management Practices (BMPs).
If a facility has no Daily Maximum Limit for TRC (just a monitoring requirement), then use of a hand-held meter,
sometimes described as a pocket colorimeter, is acceptable (see the note above regarding stormwater monitoring
requirements). For facilities using these hand-held meters, the North Carolina Division of Water Resources [formerly
the Division of Water Quality] has established the minimum reporting level at 100 pg/L. Any values obtained less
than that concentration must be reported as "<100 pg/L". Ref: Division of Water Quality, Point Source
Compliance/Enforcement Unit letter dated August 14, 2001.
When using a Hach Pocket Colorimeter, follow these instructions to prepare samples for analysis:
10 mL Powder Pillows are to be used with the 10-mL glass vial under the Low -Range (LR) setting on the
Pocket Colorimeter. LR range is 0.02 to 2.00 mg/L C12.
25 mL Powder Pillows are to be used with the 10-mL glass vial under the Mid -Range (MR) setting on the
Pocket Colorimeter. MR range is 0.05 to 4.00 mg/L C12.
25 mL Powder Pillows are to be used with the 5-mL plastic vial under the High -Range (HR) setting on the
Pocket Colorimeter. HR range is 0.1 to 10.0 mg/L C12.
When citing Standard Methods 4500-CI G-2011, the laboratory may opt to use liquid reagents and the Pour-Thru
Cell, but this is not required. Filtering samples is an allowable modification under Code of Federal Regulations, Title
40, Part 136; Federal Register Vol. 82, No. 165, August 28, 2017; 136.6. (b).
All standard materials used must be ACS grade or higher purity.
Sample duplicates are not a required quality control element for Field parameters.
Definitions
Laboratory -generated Calibration Curve: A linear regression equation generated from the analysis of a series of
laboratory -prepared liquid standards. Sample results are obtained by plugging sample absorbance values into the
linear regression formula. This is usually performed automatically by direct read-out meters.
Factory -set Calibration Curve: An internal calibration curve, generated and stored as meter programs by the
instrument manufacturer.
Calibration Blank: Deionized or Distilled water, without chlorine and without DPD/buffer, that is used to zero the meter.
A sealed standard (e.g., gel) blank may also be used for this purpose.
Rev 11 /26/2019

® Method Blank: Deionized or Distilled water, from the same source used to make calibration and calibration verification
standards, that is analyzed like a sample (i.e., with DPD/buffer added). The concentration of the Method Blank must
not exceed 50% of the reporting limit (i.e., the lowest calibration or calibration verification standard concentration),
unless otherwise specified by the reference method, or corrective action must be taken. Method Blanks would be
required when using laboratory -prepared standards [including Proficiency Testing (PT) Samples] and anytime sample
dilutions are performed.
® Second -source Standard: A standard prepared from a source independent (e.g., different vendor, different lot #, etc.)
from that used to prepare the calibration standards.
NOTE: When using a Factory -set Calibration Curve, all other standards are considered to be Second -source
standards.
® Daily Check Standard: A sealed standard (e.g., gel) or a laboratory -prepared standard of known concentration of the
analyte of interest. A Daily Check Standard is used to evaluate laboratory performance and analyte recovery in a
blank matrix.
® Post -Analysis Calibration Verification Standard: A Daily Check Standard that is analyzed after all sample analyses.
Instrument Calibration or Calibration Curve Verification:
Depending upon the meter, you may either construct a Laboratory -generated Calibration Curve or verify the Factory -set
Calibration Curve initially, at least every 12 months and any time the instrument optics are serviced. Most field photometric
instruments have factory -set calibration programs, which when selected in combination with the optimum wavelength for a
particular analysis, give a direct readout in concentration. These factory -set calibration programs are acceptable for
quantitation, but due to possible analyst error, variation in sample or standard preparation, variation in reagents or
malfunction of the instrument, the Factory -set Calibration Curve must be verified as described below.
Calibration curve verification checks must be performed with the calibration curve and/or program used for sample analysis.
All compliance monitoring and PT Samples must be analyzed on the prepared or verified calibration curve and/or program.
For all calibration options, the range of standard concentrations must bracket the permitted discharge limit concentration, the
range of sample concentrations to be analyzed and anticipated PT Sample concentrations. One of the standards must have
a concentration less than the permitted Daily Maximum Limit. The lower reporting limit concentration is equal to the lowest
standard concentration. Sample concentrations that are less than the lower reporting limit must be reported as a less -than
value.
Example:
If a facility has a Total Residual Chlorine Daily Maximum Limit of 28 pg/L, they must demonstrate they can
accurately quantify TRC below the Daily Maximum Limit. To do this, a standard concentration less than 28 tag/L
must be analyzed. Most laboratories choose a standard concentration below their Daily Maximum Limit that is easy
to prepare, such as 20 tag/L in this example. This will be their lower reporting limit. Anytime a compliance sample
measures less than this value (e.g., 18 tag/L), it is reported on the eDMR as <20 tag/L.
If the laboratory chooses 400 tag/L as the highest concentration in the calibration curve or calibration curve
verification, all samples above this concentration must be diluted and reanalyzed to fall within the range of the chosen
lower reporting limit and 400 tag/L.
Calibration and Calibration Curve Verification Options: Option 1 is the most widely used calibration curve verification
option. Another certified laboratory may be able to provide assistance with the meter calibration curve and calibration curve
verification options listed below. All documentation must be maintained by the meter user.
If the factory -set readings (Options 1 and 2 below) vary by more than the stated acceptance criteria, the stored calibration
program must not be used for compliance monitoring until troubleshooting is carried out to determine and correct the source of
error.
NOTE: Possible corrective actions include: re -zeroing the meter, ensuring glassware is clean and not scratched; preparing
fresh calibration standards; having the meter serviced, etc.
Rev 11 /26/2019

NOTE: General Absorbance Standards (i.e., standards with specific absorbance values plus a tolerance range that are used
to check absorbances at specific wavelengths) sometimes referred to as a "HACH DR/Check Absorbance Standard Kir,
cannot be used for the Daily Check Standard or as a calibration standard.
Option 1 — Annual Factory -set Calibration Curve Verification: This type of calibration curve verification must be
performed initially, at least every 12 months and any time the instrument optics are serviced. Zero the
instrument with a Calibration Blank and then analyze a Method Blank and a series of five standards (do not use gel or
sealed liquid standards for this purpose). The calibration standard values obtained must not vary by more than ±10%
from the known value for standard concentrations greater than or equal to 50 fag/L and must not vary by more than
±25% from the known value for standard concentrations less than 50 fag/L.
Each day compliance samples are analyzed, perform the following:
® When an annual five -standard Factory -set Calibration Curve verification is used, the laboratory must check
the calibration curve each analysis day. To do this, the laboratory must zero the instrument with a Calibration
Blank and analyze a Daily Check Standard (gel -type standards are most widely used for these purposes).
The value obtained for the Daily Check Standard must read within ±10% of the true value of the Daily Check
Standard for standards >_50 fag/L and within ±25% of its true value for standards <50 fag/L. If the obtained
value is outside of the acceptance limits, corrective action must be taken.
® If preparing standards, analyzing a PT Sample or analyzing diluted samples, a Method Blank is required.
® When performing analyses at multiple sample sites in a single day, a Post -analysis Calibration Verification
Standard must be analyzed after the last sample. It is recommended that a mid -day calibration verification
be performed when samples are analyzed over an extended period of time. The value obtained for the Post -
analysis Calibration Verification Standard must read within ±10% of the true value of the Post -analysis
Calibration Verification Standard for standards >_50 fag/L and within ±25% of its true value for standards <50
fag/L. If the obtained value is outside of the acceptance limits, corrective action must be taken.
Option 2 — Daily Factory -set Calibration Curve Verification: This type of calibration curve verification must be
performed each day compliance samples are analyzed. Zero the instrument with the Calibration Blank and then
analyze a Method Blank and a series of three standards (do not use gel or sealed liquid standards for this purpose).
The values obtained must not vary by more than ±10% of the known value for standard concentrations greater than or
equal to 50 fag/L and must not vary by more than ±25% of the known value for standard concentrations less than 50
pg/L.
® When performing analyses at multiple sample sites in a single day, a Post -analysis Calibration Verification
Standard must be analyzed after the last sample. It is recommended that a mid -day calibration verification
be performed when samples are analyzed over an extended period of time. The value obtained for the Post -
analysis Calibration Verification Standard must read within ±10% of the true value of the Post -analysis
Calibration Verification Standard for standards >_50 fag/L and within ±25% of its true value for standards <50
fag/L. If the obtained value is outside of the acceptance limits, corrective action must be taken.
Option 3 — Annual Laboratory -generated Calibration Curve: This type of calibration curve must be generated
initially, at least every 12 months and any time the instrument optics are serviced. Zero the instrument with
the Calibration Blank and then analyze a Method Blank and a series of five standards (do not use gel or sealed
liquid standards for this purpose). The obtained values are programmed into the instrument, computer spreadsheet,
scientific calculator, or plotted manually. The correlation coefficient of the calibration curve must be >_0.995. Back
calculate the concentration of each calibration point. For standards <50 fag/L, the back -calculated value and
standard true value must agree within ±25%. For standards >_50 fag/L, the back -calculated value and standard true
value must agree within ±10%. The calibration curve must then be verified by analyzing a Second -source Standard
(gel -type standards may not be used). The Second -source Standard must read within ±10% of its true value for
standards z50 fag/L and within ±25% of its true value for standards <50 fag/L. Sample results are obtained from the
linear regression equation of the calibration curve.
Each day compliance samples are analyzed, perform the following:
® When an annual five -standard Laboratory -generated Calibration Curve is used, the laboratory must check the
calibration curve each analysis day. To do this, zero the instrument with a Calibration Blank and analyze a
Daily Check Standard (gel -type standards are most widely used for this purpose). The value obtained for the
Daily Check Standard must read within ±10% of the true value of the Daily Check Standard for standards
Z50 fag/L and within ±25% of its true value for standards <50 fag/L. If the obtained value is outside of the
acceptance limits, corrective action must be taken.
Rev 11 /26/2019

® If preparing standards, analyzing a PT Sample or analyzing diluted samples, a Method Blank is required.
® When performing analyses at multiple sample sites in a single day, a Post -analysis Calibration Verification
Standard must be analyzed after the last sample. It is recommended that a mid -day calibration verification
be performed when samples are analyzed over an extended period of time. The value obtained for the Post -
analysis Calibration Verification Standard must read within ±10% of the true value of the Post -analysis
Calibration Verification Standard for standards >_50 pg/L and within ±25% of its true value for standards <50
pg/L. If the obtained value is outside of the acceptance limits, corrective action must be taken.
Option 4 — Daily Laboratory -generated Calibration Curve: This type of calibration curve must be generated each
day compliance samples are analyzed. Zero the instrument with the Calibration Blank and then analyze a Method
Blank and a series of three standards (do not use gel or sealed liquid standards for this purpose). The obtained
values are programmed into the instrument, computer spreadsheet, scientific calculator, or plotted manually. The
correlation coefficient of the calibration curve must be z0.995. Back calculate the concentration of each calibration
point. For standards <50 pg/L, the back -calculated value and standard true value must agree within ±25%. For
standards >_50 pg/L, the back -calculated value and standard true value must agree within t10%. Sample results are
obtained from the linear regression equation of the calibration curve.
Each day compliance samples are analyzed, perform the following:
® When a daily three -standard Laboratory -generated Calibration Curve is used, the laboratory must verify the
calibration curve each analysis day with a Daily Check Standard prepared from a second source. The
calibration check is performed immediately after calibration. The value obtained for the Daily Check Standard
must read within ±10% of the true value of the Daily Check Standard for standards >_50 pg/L and within
±25% of its true value for standards <50 pg/L. If the obtained value is outside of the acceptance limits,
corrective action must be taken.
® When performing analyses at multiple sites, a Post -analysis Calibration Verification Standard must be
analyzed at the end of the run. It is recommended that a mid -day calibration verification be performed when
samples are analyzed over an extended period of time. The value obtained for the Post -analysis Calibration
Verification Standard must read within ±10% of the true value of the Post -analysis Calibration Verification
Standard for standards z50 pg/L and within ±25% of its true value for standards <50 pg/L. If the obtained
value is outside of the acceptance limits, corrective action must be taken.
Standard Solutions:
All standards and PT Samples must be prepared using Class -A volumetric flasks and either a calibrated mechanical pipette or
a Class -A volumetric pipette.
Potassium Permanganate Stock Solution: Prepare a stock solution containing 891 mg KMn04/1000 mL. Dilute 10.00 mL stock
solution to 100 mL with chlorine -free water in a volumetric flask. When 1 mL of this solution is diluted to 100 mL with chlorine -
free water, a chlorine equivalent of 1.00 mg/L will be in the DPD reaction. Store in an amber glass bottle and refrigerate. Use
within the laboratory -assigned expiration date.
Working standards for calibrating the meter or verifying the Factory -set Calibration Curve can be made by serial dilutions of
the stock solution.
If commercially prepared liquid chlorine standard solutions with a stated range and average value are used, the average value
must be used for the true value of the standard. These standards may only be used for the Daily Check Standard and
verification of a Factory -set Calibration Curve. They may not be used for preparing a Laboratory -generated Calibration Curve.
Purchased "gel -type" or sealed liquid standards may be used only for daily calibration curve verifications. These standards
must have a true value assigned initially and with each subsequent calibration curve generation/verification thereafter. When
this is done, these standards may be used after the manufacturer's expiration date. It is only necessary to assign a true value
to the gel -type or sealed liquid standard which falls within the concentration range of the calibration curve used to measure
sample concentrations. For example, if you are measuring samples against a low -range calibration curve, a 200 pg/L standard
would be verified, and not the 800 pg/L standard since the 800 pg/L standard would be measured using a high -range
calibration curve.
Rev 11/26/2019

To assign a true value to the gel -type or sealed liquid standard:
1. Zero the instrument with the calibration blank.
2. Read and record gel standard values.
3. Repeat steps 1 and 2 at least two more times.
4. Assign the average value as the true value.
The assigned true value will be used until a new calibration curve verification is performed and the true value is reassigned.
The gel/sealed liquid standard true value assignment must be performed for each instrument on which they are to be used. If
multiple instruments and/or standard sets are used, each must have assigned true values specific for the instrument and
standard set. Documentation must link the gel/sealed liquid standard identification to the meter with which the assigned value
was determined.
Equipment Maintenance:
As cited in the Laboratory Certification rules, "Each facility must have glassware, chemicals, supplies, equipment, and a
source of distilled or deionized water that will meet the minimum criteria of the approved methodologies." Ref: 15A NCAC 2H
.0805 (g) (4). Meeting the minimum criteria means the equipment must also be properly maintained. Clean and maintain
equipment as indicated by the manufacturer's instructions.
Daily Sample Analysis Procedure:
® Zero meter
® Analyze Daily Check Standard
® Collect sample (sample may be collected before or after calibration or calibration check)
® Add DPD/buffer within 15 minutes of collection
® Wait 3 - 6 minutes
® Read sample result
® Document required information
Documentation:
The following must be documented in indelible ink whenever sample analysis is performed:
1. Date and time of sample collection
2. Date and time of sample analysis to verify the 15-minute holding time is met [Alternatively, one time may be
documented for collection and analysis with the notation that samples are measured immediately at the sample site.]
3. Facility name, sample site (ID or location), and permit number
4. Collector's/analyst's name or initials
5. Daily Check Standard analysis date and time(s)
6. Preparation procedure and true values of laboratory -prepared standards, when applicable
7. True value of the Daily Check Standard(s)
8. Value obtained for the Daily Check Standard(s) and percent recovery
9. Time analyzed, true value and value obtained for the Post -analysis Calibration Verification Standard(s), where
applicable
10. All data must be documented and reported in units of measure as specified in the permit (e.g., mg/L for regular level
or pg/L for low level)
11. Traceability for chemicals, reagents, standards and consumables
12. Instrument identification (serial number preferred)
13. Date of most recent calibration curve generation or calibration curve verification
14. Statement that samples were filtered, when applicable
15. Final value to be reported
16. Parameter analyzed
17. Method reference
18. Data qualifier(s), when applicable
19. Equipment maintenance (recommended)
This document was prepared using Standard Methods 4500-CI G — 2011 and Hach Methods 8021, 10070 and 10250
as references.
Rev 11/26/2019

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