#43_2018_0815_MC_FINAL

Laboratory Cert. :
43
Laboratory Name:
Lexington Regional WWTP Laboratory
Inspection Type:
Municipal Maintenance
Inspector Name(s):
Michael Cumbus, Beth Swanson, Anna Ostendorff, Jason Smith, Thomas
Halvosa, Todd Crawford
Inspection Date:
August 15-16, 2018
Date Forwarded for Initial
Review:
September 11, 2018
Initial Review by:
Anna Ostendorff
Date Initial Review
Completed:
September 14, 2018
Cover Letter to use:
❑ Insp. Initial ❑ Insp. Reg
❑Insp. No Finding ❑Insp. CP
❑Corrected ®Insp. Reg. Delay
Unit Supervisor/Chemist III:
Beth Swanson
Date Received:
October 6, 2018
Date Forwarded to Admin.:
October 25, 2018
Date Mailed:
October 26, 2018
Special Mailing Instructions:
Michael emails a copy to Sherri Knight at WSRO

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October 26, 2018
43
Ms. Eglantina Minerali
Lexington Regional WWTP Laboratory
28 West Center Street
Lexington, NC 27292
Subject: North Carolina Wastewater/Groundwater Laboratory Certification (NC WW/GW LC)
Maintenance Inspection
Dear Ms. Minerali:
Enclosed is a report for the inspection performed on August 15 and 16, 2018 by Michael
Cumbus. 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 21-1 .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] ext. 259.
Sincerely,
---?J
Beth Swanson
Technical Assistance & Compliance Specialist
Division of Water Resources
Attachment
cc: Michael Cumbus, Dana Satterwhite, Todd Crawford
North Carolina Department of Environmental Quality I Division of Water Resources
1623 Mail Service Center I Raleigh, North Carolina 27699-1623
Phone 919.733,3908/Fax [phone]

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LABORATORY NAME: Lexington Regional WWTP
NPDES PERMIT : NC0055786
ADDRESS: 500 Glendale Rd
Lexington, NC 27292
CERTIFICATE #: 43
DATE OF INSPECTION: August 15-16, 2018
TYPE OF INSPECTION: Municipal Maintenance
AUDITOR(S): Michael Cumbus, Beth Swanson, Anna Ostendorff, Jason Smith,
Thomas Halvosa and Todd Crawford
LOCAL PERSON(S) CONTACTED: Eglantina Minerali and Sarah West
I. INTRODUCTION:
This laboratory was inspected by representatives 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 facility is neat and well organized and has all the equipment necessary to perform the
analyses. Laboratory personnel communicate well with sample collectors and coordinate sample
analyses effectively to manage workload and holding times. Laboratory personnel changed since
the last inspection. With Ms. Minerali taking over as supervisor, the laboratory has been proactive
in its in-house data audits, reaching out to the Certification Branch concerning quality control issues
and initiating corrections to their procedures prior to the inspection once receiving the parameter
checklists. Examples include initiating the sterility check of the bacteria sample bottles in June
2018 and the analysis of a second source standard for Phosphorus analysis. The laboratory was
forthcoming about quality control issues that it found and was very receptive to the feedback from
the auditors. The laboratory seemed eager to adopt changes that would allow it to continue to
produce quality data.
All required Proficiency Testing (PT) Samples have been analyzed for the 2018 PT Calendar Year
and the graded results were 100% acceptable.
The laboratory submitted their Quality Assurance (QA) and/or Standard Operating Procedures
(SOP) document(s) in advance of the inspection. These documents were reviewed and editorial
and substantive revision requirements and recommendations were made by this program
outside of this formal report process. Although subsequent revisions were not requested to be
submitted, they must be completed by September 30, 2019.

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#43 Lexington Regional WWTP Laboratory
The laboratory is reminded that any time changes are made to laboratory procedures, the
laboratory must update the QA/SOP document(s) and inform relevant staff. Any changes made
in response to the pre -audit review or to Findings, Recommendations or Comments listed in this
report must be incorporated to insure the method is being performed as stated, references to
methods are accurate, and the QA and/or SOP document(s) is in agreement with each
approved practice, test, analysis, measurement, monitoring procedure or regulatory requirement
being used in the laboratory. In some instances, the laboratory may need to create an SOP to
document how new functions or policies will be implemented.
The laboratory is also reminded that SOPs are intended to describe procedures exactly as they
are to be performed. Use of the word "should" is not appropriate when describing requirements
(e.g., Quality Control (QC) frequency, acceptance criteria, etc.). Evaluate all SOPs for the proper
use of the word "should".
Laboratory Fortified Matrix (LFM) and Laboratory Fortified Matrix Duplicate (LFMD) are also
known as Matrix Spike (MS) and Matrix Spike Duplicate (MSD) and may be used
interchangeably in this report.
Requirements that reference 15A NCAC 2H .0805 (a) (7) (A), stating "All analytical data pertinent
to each certified analysis must be filed in an orderly manner so as to be readily available for
inspection upon request", are intended to be a requirement to document information pertinent to
reconstructing final results and demonstrating method compliance. Use of this requirement is not
intended to imply that existing records are not adequately maintained unless the Finding speaks
directly to that.
Contract analyses are performed by Environment 1, Inc. (Certification #10).
Approved Procedure documents for the analysis of the facility's currently certified Field
Parameters were provided at the time of the inspection.
III. FINDINGS, REQUIREMENTS, COMMENTS AND RECOMMENDATIONS:
General Laboratory
A. Finding: The analytical balance weights have not been verified against ASTM standard
weights in the past 5 years.
Requirement: ASTM Class 1 and 2 weights must be verified at least every 5 years. ASTM
Class 1 weights (20 g to 25 kg) and ASTM Class 2 weights (10 g to 1 mg) are equivalent to
the NBS Class S weights specified in 15A NCAC 2H .0805 (a) (7) (K). Ref: NC WW/GW LC
Policy. See attachment "Weight Verification (NC WW/GW LC Policy 05/23/2008)" for
additional guidance.
B. Finding: For chemicals/reagents/consumables that do not have an expiration date, the
laboratory has not established a policy for assigning expiration dates.
Requirement: Adherence to manufacturer expiration dates is required. Chemicals/
reagents/ consumables exceeding the expiration date can no longer be considered reliable.
If the expiration is only listed as a month and year (with no specific day of the month), the
last day of the month will be considered the actual date of expiration. Monitor materials for
changes in appearance or consistency. Any changes may indicate potential contamination
and the item should be discarded, even if the expiration date is not exceeded. If no
expiration date is given the laboratory must have a policy for assigning an expiration date.

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#43 Lexington Regional WWTP Laboratory
If no date received or expiration date can be determined, the item should be discarded. Ref:
NC WW/GW LC Policy.
Comment: The policy for assigning expiration dates must be added to the laboratory's QA
document.
Quality Control
C. Finding: The laboratory does not have an SOP for all parameters.
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 2H .0805 (a) (7).
Comment: An SOP describes the method in such detail that an experienced analyst
unfamiliar with the method can obtain acceptable results and meet documentation
requirements. SOPs must be developed which describe in detail how a method is
performed in that particular laboratory.
Comment: The following methods were lacking an SOP at the time of the inspection:
Temperature — Standard Methods, 2550 B-2010 (Aqueous)
Dissolved Oxygen — Standard Methods, 4500 O C-2011 (Aqueous)
Dissolved Oxygen — Standard Methods, 4500 O G-2011 (Aqueous)
The laboratory must have an updated QC/SOP document for the parameters included on
their Certified Parameters List (CPL) by December 14, 2018. This must be submitted for
review upon completion. A written response is required.
D. Finding: The laboratory is not evaluating reagent blank concentrations against the
acceptance criterion for Ammonia Nitrogen.
Requirement: For analyses requiring a calibration curve, the concentration of reagent,
method and calibration blanks must not exceed 50% of the reporting limit or as otherwise
specified by the reference method. Ref: NC WW/GW LC Policy.
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 2H .0805 (a) (7).
Comment: The laboratory is documenting <0.1 mg/L on the benchsheet for blanks, rather
than the actual reading from the instrument. The reporting limit is 0.1 mg/L, so this does not
demonstrate adherence to the acceptance criterion.
E. Finding: The laboratory is not analyzing an LFMD.
Requirement: When appropriate for the analyte (Table 4020:1), include at least one
LFM/LFMD daily or with each batch of 20 or fewer samples. To prepare an LFM, add a
known concentration of analytes (ideally from a second source) to a randomly selected
routine sample without increasing its volume by more than 5%. Ref: SM 4020 B-2011,
Table 4020:1 and (2) (g).

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#43 Lexington Regional WWTP Laboratory
Requirement: Include a minimum of one LFM/LFMD for every 20 samples in an analytical
batch, or include more LFM/LFMDs if appropriate. Ref: Standard Methods, 3020 B-2005,
Rev. 2011. (2) (h).
Comment: The laboratory has been analyzing a sample duplicate as part of its routine
analysis for Total Phosphorus, Metals, Nitrate, Nitrite and Total Kjeldahl Nitrogen (TKN) but
has not been analyzing an LFMD.
Comment: Spiked or fortified samples must be treated the same way as the source
sample. This includes, but is not limited to, acidification, digestion, filtration and dilution.
F. Finding: The laboratory is not analyzing a Method Blank.
Requirement: Method blank (MB): Include at least one MB daily or with each batch of 20
or fewer samples, whichever is more frequent. Ref: Standard Methods, 4020 B-2010. (2)
(d) and Table 4020:1.
Requirement: A reagent blank (method blank) consists of reagent water (see Section
1080) and all reagents (including preservatives) that are normally in contact with a sample
during the entire analytical procedure. Ref: Standard Methods, 1020 B-2011. (5).
Comment: The laboratory is not analyzing a MB for Ammonia and Total Phosphorus.
G. Finding: Preservative is not being added to laboratory fortified blanks (LFB) for Ammonia
samples.
Requirement: Include at least one LFB daily or per each batch of 20 or fewer samples.
Ref: Standard Methods, 4020 B-2010 (2) (e).
Requirement: A laboratory -fortified blank [laboratory control standard (LCS)] is a reagent
water sample (with associated preservatives) to which a known concentration of the
analyte(s) of interest has been added. Process the LFB through all sample preparation
and analysis steps. Ref: Standard Methods, 1020 B-2011. (6).
Comment: The laboratory is running a standard with each Ammonia run; however, the
standard is not a true LFB since it does not have the chemical preservation and (if
necessary) dechlorinating agent added to it.
H. Finding: A second source standard is not analyzed.
Requirement: When a standard curve is manually prepared (as opposed to a factory -set
calibration), it is required to analyze one known standard in addition to calibration
standards each day samples are analyzed to document accuracy. This standard must be
prepared from materials obtained from a source independent from the one used for
preparing the calibration standards (often referred to as a second source standard or
external reference standard). A second source standard may be:
® a quality control standard obtained from a vendor,
® a standard prepared from primary standards obtained from a second vendor, or
® a standard made from primary standards from the same vendor but from a different
lot number (i.e., an independent lot) as those used to make the calibration
standards.

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#43 Lexington Regional WWTP Laboratory
Laboratory control standards are evaluated to assess whether the lab is in control of the
processes involved in the preparation and analysis of specific tests. Laboratory control
standards must be similar in composition to the environmental samples. They must contain
known concentrations of all analytes of interest and undergo the same preparatory and
determinative procedures as the environmental samples.
Second source standards must be evaluated using one of the following: vendor supplied
criteria, method -defined acceptance criteria, in-house calculated acceptance limits that are
statistically -derived from historical data based on three standard deviations from the mean
in the detectable range or other statistically viable evaluation criterion. If the results fall
outside of acceptance limits, the analysis is out of control. The analysis must be
terminated and the problem corrected prior to sample analysis. Ref: NC WW/GW LC
Policy.
Comment: The laboratory was not analyzing a second source standard for Nitrate and
Nitrite analyses.
Documentation
Recommendation: It is recommended that the laboratory document the acceptance criteria for
TKN QC standard and spike recoveries and RPD of the LFM/LFMD on the benchsheet so that
acceptability can be easily ascertained.
I. Finding: The laboratory needs to increase the traceability documentation of purchased
materials and reagents, as well as documentation of standards and reagents prepared in
the laboratory.
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, lots of pre -made standards and/or media, solids and bacteria filters,
etc. are included in this requirement. Ref: NC WW/GW LC Policy.
Requirement: Supporting records shall be maintained as evidence that these practices are
being effectively carried out. All analytical records must be available for a period of five
years. Ref: 15A NCAC 2H .0805 (a) (7) and (a) (7) (G).
Comment: This finding applies to pH probes and fecal membrane filters as well as
purchased and laboratory prepared standards/reagents.
Comment: The laboratory benchsheet for Total Suspended Residue has a place for lot
number of the filters, but it has not been utilized. The laboratory has begun recording all
information except lot number in a logbook specifically for Total Suspended Residue filters.
Therefore, a link cannot be made between the lot number and analysis.
Comment: This finding also applies when portions of pH buffers are placed into separate
containers for daily and/or weekly use.

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J. Finding: Some benchsheets and/or report summaries reference unapproved methods
and/or do not fully reference the approved methods.
Requirement: Laboratory procedures, analytical methods, sample preservation, sample
containers and sample holding times shall conform to those requirements found in 40 CFR-
136.3. Ref: 15A NCAC 21-1.0805 (a) (1).
Comment: The laboratory documentation must reference the method versions as found on
the CPL.
Comment: The metals digestion log incorrectly cited Standard Methods 18'" edition 3030F,
and needs to be updated to Standard Methods, 3030 F-2004.
Recommendation: It is recommended that the laboratory review the benchsheets for all
parameters to ensure that the correct method reference is cited.
K. Finding: Chemical containers are not consistently dated when received and when opened.
Requirement: Chemicals must be dated when received and when opened. Ref: 15A
NCAC 21-1.0805 (a) (7) (Q.
L. Finding: The Total Phosphorus and Settleable Residue benchsheets are lacking pertinent
data: volume of sample analyzed.
Requirement: All laboratories must use printed laboratory bench worksheets that include a
space to enter the signature or initials of the analyst, date of analyses, sample identification,
volume of sample analyzed, value from the measurement system, factor and final value to
be reported and each item must be recorded each time samples are analyzed. Ref: 15A
NCAC 21-1.0805 (a) (7) (H).
M. Finding: The laboratory benchsheet is lacking pertinent data: units of measure.
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: units of measure. Ref: NC WW/GW LC Approved Procedure for the
Analysis of Dissolved Oxygen, NC WW/GW LC Approved Procedure for the Analysis of
Specific Conductance (Conductivity).
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
Requirement: All laboratories must use printed laboratory bench worksheets that include a
space to enter the signature or initials of the analyst, date of analyses, sample identification,
volume of sample analyzed, value from the measurement system, factor and final value to
be reported and each item must be recorded each time samples are analyzed. Ref: 15A
NCAC 21-1.0805 (a) (7) (H).
Comment: The laboratory benchsheets for DO lack units of measure. The laboratory
benchsheet for Conductivity incorrectly labels the units of measure for "average results" as
"pohms/cm" instead of "pmhos/cm". The "Laboratory Worksheet For Plant Analyses" is
missing units for initial weight, final weight and net weight for Total Suspended Residue and
Total Residue samples.

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#43 Lexington Regional WWTP Laboratory
N. Finding: The laboratory benchsheets for Conductivity, Dissolved Oxygen and Temperature
are lacking pertinent data: method reference.
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: method reference. Ref: NC WW/GW LC Approved Procedure for the
Analysis of Specific Conductance (Conductivity), NC WW/GW LC Approved Procedure for
the Analysis of Dissolved Oxygen, NC UWV/GW LC Approved Procedure for the Analysis of
Temperature
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
®. Finding: The laboratory benchsheet is lacking pertinent data: instrument identification.
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
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 Temperature, NC WW/GW LC
Approved Procedure for the Analysis of Dissolved Oxygen, NC WW/GW LC Approved
Procedure for the Analysis of pH.
Comment: Documentation of the instrument ID is inconsistent across all benchsheets and
operator logs.
P. Finding: Process control samples are not documented as such.
Requirement: All laboratories must use printed laboratory bench worksheets that include
a space to enter the signature or initials of the analyst, date of analyses, sample
identification, volume of sample analyzed, value from the measurement system, factor and
final value to be reported and each item must be recorded each time samples are
analyzed. The date and time BOD and coliform samples are removed from the incubator
must be included on the laboratory worksheet. Ref: 15A NCAC 2H .0805 (a) (7) (H).
Comment: The Field parameter notebook calls the aeration basin DO "effluent" and
operator logs do not specify location.
Comment: The laboratory is recording pH values in operator logs for process control
without identifying the values as such.
Q. Finding: The laboratory benchsheet is lacking pertinent data: meter calibration time (daily
check standard) and date of most recent curve verification.
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: meter calibration time (daily check standard), date of most recent
curve verification. Ref: NC WW/GW LC Approved Procedure for the Analysis of Total
Residual Chlorine.

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#43 Lexington Regional WWTP Laboratory
R. Finding: The volume of 10N NaOH added to standards and samples is not documented.
This is considered pertinent data.
Requirement: Add a sufficient volume of 10N NaOH solution (1 mL usually is sufficient) to
raise pH above 11. If the presence of silver or mercury is possible, use NaOH/EDTA
solution in place of NaOH solution. If it is necessary to add more than 1 mL of either
NaOH or NaOH/EDTA solution, note volume used, because it is required for subsequent
calculations. Ref: Standard Methods, 4500 NH3 D-2011. (4) (b).
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15 NCAC
2H .0805 (a) (7) (A).
S. Finding: The date and time that. samples for metals analysis are digested is not
consistently documented.
Requirement: All laboratories must use printed laboratory bench worksheets that include
a space to enter the signature or initials of the analyst, date and time of analyses, sample
identification, volume of sample analyzed, value from the measurement system, factor and
final value to be reported and each item must be recorded each time samples are
analyzed. Ref: 15A NCAC 2H .0805 (a) (7) (H).
Comment: Sample digestion is considered part of the analysis.
T. Finding: The laboratory is not documenting the pH of the phosphate buffer solution used in
BOD analyses to be 7.2 S.U. after preparation. This is considered pertinent data.
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
Requirement: Phosphate buffer solution: Adjust pH to 7.2 with 30% NaOH and dilute to
1 L. Ref: Standard Methods, 5210 B-2011. (3) (a).
U. Finding: The laboratory benchsheet for Total Phosphorus is lacking pertinent data: volume
of sample digested and post -digestion sample volume.
Requirement: All laboratories must use printed laboratory bench worksheets that include
a space to enter the signature or initials of the analyst, date of analyses, sample
identification, volume of sample analyzed, value from the measurement system, factor and
final value to be reported and each item must be recorded each time samples are
analyzed. Ref: 15A NCAC 2H .0805 (a) (7) (H)
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
Comment: Documentation of the initial and final volumes will help the laboratory to verify
the appropriate use of, or lack of, a dilution factor.
V. Finding: The laboratory is not clearly documenting sample identification for all pH values.

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#43 Lexington Regional WWTP Laboratory
Requirement: All laboratories must use printed laboratory bench worksheets that include a
space to enter the signature or initials of the analyst, date of analyses, sample identification,
volume of sample analyzed, value from the measurement system, factor and final value to
be reported and each item must be recorded each time samples are analyzed. The date
and time BOD and coliform samples are removed from the incubator must be included on
the laboratory worksheet. Ref: 15A NCAC 21-1.0805 (a) (7) (H).
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 21-1.0805 (a) (7).
Comment: The laboratory calibration log does not clearly identify buffers used for
calibration versus those used to check calibration. The laboratory must clearly identify
which buffers/ values are used to calibrate, and which buffers/values are used to verify
calibration.
Comment: pH values used to determine the necessity of pH adjustment on BOD samples
are documented on the Laboratory Worksheet for Plant Analysis, but not identified as such.
They appear to be a pH value for compliance data reporting.
Proficiency Testing
W. Finding: The laboratory does not have a documented plan for PT procedures.
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 2H .0805 (a) (7).
Requirement: Laboratories must have a documented plan (this is usually detailed in the
laboratory's Quality Assurance Manual or may be a separate Standard Operating
Procedure (SOP)) of how they intend to cover the applicable program requirements for
Proficiency Testing per their scope of accreditation. This plan shall cover any commercially
available PT Samples and any inter -laboratory organized studies, as applicable. The
laboratory must also be able to explain when PT Sample analysis is not possible for certain
methods and provide a description of what the laboratory is doing in lieu of Proficiency
Testing. This shall be detailed in the plan. The plan must also address the laboratory's
process for submission of PT results and related Corrective Action Reports (CARs). Ref:
Proficiency Testing Requirements, May 31, 2017, Revision 2.0.
X. 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, May 31, 2017, Revision 2.0.
Comment: Dating and initialing the instruction sheet for each prepared PT Sample would
satisfy the documentation requirement.

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#43 Lexington Regional WWTP Laboratory
Y. Finding: Additional QC beyond what is routine for Compliance Samples is being analyzed
with PT Samples.
Requirement: Laboratories are required to analyze an appropriate PT Sample by each
parameter method on the laboratory's Certified Parameters Listing (CPL). The same PT
Sample may be analyzed by one or more methods. Laboratories shall conduct the
analyses in accordance with their routine testing, calibration and reporting procedures,
unless otherwise specified in the instructions supplied by the Accredited PT Sample
Provider. This means that they are to be logged in and analyzed using the same staff,
sample tracking systems, standard operating procedures including the same equipment,
reagents, calibration techniques, analytical methods, preparatory techniques (e.g.,
digestions, distillations and extractions) and the same quality control acceptance criteria.
PT Samples shall not be analyzed with additional quality control. They are not to be
replicated beyond what is routine for Compliance Sample analysis. Although, it may be
routine to spike Compliance Samples, it is neither required, nor recommended, for PT
Samples. PT Sample results from multiple analyses (when this is the routine procedure)
must be calculated in the same manner as routine Compliance Samples. Ref: Proficiency
Testing Requirements, May 31, 2017, Revision 2.0.
Comment: The laboratory's common practice is to analyze a purchased reference
standard along with the PT Sample as additional QC. Since this is not performed with all
Compliance Samples, it is considered additional QC. However, additional QC is
recommended as part of the troubleshooting and corrective action process, prior to
analyzing remedial PT Samples.
Z. Finding: PT Samples for Field Parameters have not been distributed among all operators
from year to year.
Requirement: Laboratories shall also ensure that, from year to year, PT Samples are
equally distributed among personnel trained and qualified for the relevant tests and
instrumentation (when more than one instrument is used for routine Compliance
Sample analyses), that represents the routine operation of the work group at the time
the PT Sample analysis is conducted. Ref: Proficiency Testing Requirements, May 31,
2017, Revision 2.0.
Conductivity — Standard Methods, 2510 B-2011 (Aqueous)
Recommendation: It was noted during the inspection that some conductivity standards exhibited
algae growth in the container. It is recommended that the standards be checked periodically for
growth and discarded when algae or turbidity is evident.
Recommendation: It is recommended that the laboratory pour an aliquot of standards into a
beaker or other vessel prior to taking measurements, rather than taking measurements directly
from the storage container, in order to minimize contamination of the standards.
AA. Finding: The Automatic Temperature Compensator (ATC) has not been verified initially
and every 12 months.
Requirement: The Automatic Temperature Compensator (ATC) must be verified prior to
initial use and annually (i.e., 12 months) thereafter at two temperatures by analyzing a
standard or sample at 25°C (i.e., the temperature to which conductivity values are
reported) and a temperature(s) that brackets the temperature ranges of the environmental
samples routinely analyzed. This may require the analysis of a third temperature reading
that is > 25°C. As the temperature increases or decreases, the value of the conductivity

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#43 Lexington Regional WWTP Laboratory
standard or sample must be within ±10% of the true value of the standard or ±10% of the
value of the sample at 25°C. If not, corrective action must be taken. Ref: NC WW/GW LC
Approved Procedure for the Analysis of Specific Conductance (Conductivity).
BB. Finding: The calibration verification standards are prepared incorrectly.
Requirement: Potassium Chloride (KCI) Conductivity standards may be purchased in the
ranges desired, or they may be prepared according to Table 2510:1 of Standard Methods
2510 A-2011. Ref: NC WW/GW LC Approved Procedure for the Analysis of Specific
Conductance (Conductivity).
Comment: The preparation of the standards in Table 2510:1 indicates that the relationship
between mass of KCI used and standard concentration is not linear.
CC. Finding: Accuracy (e.g. percent recovery) of QC results are not evaluated to demonstrate
the analytical process is in control and the established acceptance criteria are met.
Requirement: The value obtained for the post -analysis calibration verification check -
standard must read within 10% of the standard's true value. If the obtained value is outside
of the ±10% range, corrective action must be taken. If recalibration is necessary, all
samples analyzed since the last acceptable calibration verification must be reanalyzed, if
possible. If samples cannot be reanalyzed, the data must be qualified. Ref: NC WW/GW
LC Approved Procedure for the analysis of Specific Conductance (Conductivity).
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 2H .0805 (a) (7).
Comment: Many instances were noted where the 88.2 pmhos/cm standard was not within
the 10% acceptance criteria. Corrective action must be taken any time there are QC
exceedances.
Temperature — Standard Methods, 2550 B-2010 (Aqueous)
DD. Finding: The laboratory is not performing the annual temperature -measuring device check
procedure properly.
Requirement: To check a compliance temperature -measuring device, compare readings
at two temperatures that bracket the range of compliance samples routinely analyzed
against a National Institute of Standards and Technology (NIST) traceable temperature -
measuring device and record all four readings. The readings from both devices must
agree within 0.5 °C. Ref: NC WW/GW LC Approved Procedure for the Analysis of
Temperature.
Comment: The laboratory is checking the temperature -measuring device at a single
temperature.
EE. Finding: The temperature sensor on the Hach H2606 meter (s/n: 010012068) used to
obtain reported temperature values was not checked against an NIST traceable
temperature -measuring device initially.
Requirement: All compliance temperature -measuring devices without a valid NIST
certificate must be checked initially and every 12 months against an NIST traceable

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temperature -measuring device and the process documented. Documentation must include
the serial number of the device being checked. The serial number, stated accuracy and
expiration date of the NIST traceable temperature -measuring device used in the
comparison must also be documented. Verification data must be kept on file and be
available for inspection for 5 years. (NOTE: Vendors or other Certified laboratories may
provide assistance in meeting this requirement. When a vendor or other Certified
laboratory provides this assistance, they must provide a copy of their NIST Certificate or
the serial number, accuracy and calibration expiration date.) Ref: NC WW/GW LC
Approved Procedure for the Analysis of Temperature.
FF. Finding: The laboratory is not standardizing the sodium thiosulfate titrant initially.
Requirement: Standard sodium thiosulfate titrant: Dissolve 6.205 g NA2S2O3 • 51­12O in
distilled water. Add 1.5 mL 6N NaOH or 0.4 g solid NaOH and dilute to 1000 mL.
Standardize with bi-iodate solution. Ref: Standard Methods, 4500 O C-2011. (2) (e).
Chlorine. Total Residual — Standard Methods, 4500 Cl G-2011 (Aqueous)
Recommendation: The laboratory is currently verifying the factory -set calibration curve with
standard concentrations (i.e. 20, 200, 500, 1000 and 2000 pg/L) that do not place enough
emphasis on the range between permit and compliance limits. It is recommended that the
laboratory change the concentrations to 20, 40, 50, 200 and 400 pg/L.
GG. Finding: The annual Factory -set Calibration curve verification did not pass the individual
standard recovery criteria.
Requirement: 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 pg/L and
must not vary by more than 25% from the known value for standard concentrations less
than 50 pg/L. Ref: NC WW/GW LC Approved Procedure for the Analysis of Total
Residual Chlorine. Please submit a passing calibration curve verification with the
report reply.
Requirement: If the factory -set readings 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. Ref: NC
WW/GW LC Approved Procedure for the Analysis of Total Residual Chlorine.
Comment: The 200 pg/L standard had a recovery of 65%, while the 20 pg/L standard had
a recovery of 50%.
HH. Finding: The laboratory is not analyzing a Reagent Blank.
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.
Comment: A Reagent Blank is made from the same laboratory water source used to
make liquid standards. The concentration of Reagent Blanks must not exceed 50% of the
reporting limit (i.e., the lowest calibration or calibration verification standard concentration)
or corrective action must be taken.

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Finding: Values less than the established reporting limit are being reported on the
Discharge Monitoring Report (DMR).
Requirement: For analytical procedures requiring analysis of a series of standards,
the concentrations of those standards must bracket the concentration of the samples
analyzed. One of the standards must have a concentration equal to the laboratory's lower
reporting concentration for the parameter involved. Ref: 15A NCAC 02H .0805 (a) (7) (1).
Requirement: 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 equal to or less than the permitted discharge 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. Ref: NC WW/GW LC Approved Procedure for the Analysis of Total Residual
Chlorine.
RHH — Standard Methods, 4500 H+R-2011 (Aqueous)
JJ. Finding: Instances were observed where the pH calibration check standard did not read
within ± 0.1 S.U. of the true value and the meter was not recalibrated.
Requirement: If the meter response shows a difference greater than 0.1 pH unit from
expected value, look for trouble with the electrodes or potentiometer (see 4500-H+ B.5A
and b). Ref: Standard Methods, 4500 H+ B-2011. (4) (a).
Requirement: All check standard buffers must read within ±0.1 S.U. to be acceptable. If
the meter verification does not read within ±0.1 S.U., corrective actions must be taken
before any samples are analyzed. Ref: NC WW/GW LC Approved Procedure for the
Analysis of pH.
Comment: If the check buffer does not read within ±0.1 S.U., the lab should first try pouring
a new aliquot of the check buffer and reading it again. If it still does not read within ± 0.1
S.U., the meter must be recalibrated. If, after recalibration, the check buffer does not read
within ± 0.1 S.U., the meter and/or probe operation may be suspect and may require
servicing. If the laboratory does not have a back-up meter/electrode, or another
meter/electrode cannot be procured, it is recommended that the lab report the measured
pH results with a qualifier that indicates the value is estimated.
Comment: Possible corrective actions include: check the meter calibration procedure,
refer to the trouble shooting section in the instrument manual, and check the buffers. Even
though the buffers were within their expiration dates, the method and vendors point out
that the expiration date is for unopened buffers. Once buffers are opened the methods
and manufacturers state that buffers degrade and should be replaced in four weeks.
Nitrogen, Ammonia — Standard Methods, 4500 NH3 D-2011 (Aqueous)
Recommendation: It is recommended that each individual sample and standard is documented to
have a pH > 11 S.U. rather than a single Yes/No option on the benchsheet.
KK. Finding: Samples containing residual chlorine are not neutralized immediately upon
collection.

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#43 Lexington Regional WWTP Laboratory
Requirement: Residual Chlorine reacts with ammonia; remove by sample pretreatment. If
a sample is likely to contain residual chlorine, immediately upon collection, treat with
dechlorinating agent as in 4500-NH3. B.3d. Ref: Standard Methods, 4500 NH3 A-2011. (2).
ILL. Finding: The laboratory is not chemically preserving the samples to a pH <2 S.U. within 15
minutes of collection.
Requirement: Cool, :56 °C, H2SO4 to pH <2. Ref: Code of Federal Regulations, Title 40,
Part 136; Federal Register Vol. 82, No. 165, August 28, 2017; Table II.
Requirement: Except where noted in this Table II and the method for the parameter,
preserve each grab sample within 15 minutes of collection. For a composite sample
collected with an automated sample (e.g., using a 24-hour composite sample; see 40 CFR
122.21 (g)(7)(i) or 40 CFR Part 403, Appendix E), refrigerate the sample at <_6°C during
collection unless specified otherwise in this Table II or in the method(s). For a composite
sample to be split into separate aliquots for preservation and/or analysis, maintain the
sample at <_6°C, unless specified otherwise in this Table II or in the method(s), until
collection, splitting, and preservation is completed. Add the preservative to the sample
container prior to sample collection when the preservative will not compromise the integrity
of a grab sample, a composite sample, or aliquot split from a composite sample within 15
minutes of collection. If a composite measurement is required but a composite sample
would compromise sample integrity, individual grab samples must be collected at
prescribed time intervals (e.g., 4 samples over the course of a day, at 6-hour intervals). Ref:
Code of Federal Regulations, Title 40, Part 136; Federal Register Vol. 88, No. 165, August
28, 2017; Table II, Footnote 2.
MM. Finding: The laboratory did not verify quantitation at the minimum reporting level initially,
nor is it verified quarterly.
Requirement: The minimum reporting level (MRL) is set to a concentration at or above the
lowest standard used in the analysis. Verify quantitation at the MRL initially and at least
quarterly (preferably daily) by analyzing a QC Sample (subjected to all sample preparation
steps) spiked at 1 to 2 times the MRL. Laboratories must define acceptance criteria for the
operational range — including the MRL — in their QA documentation. Ref: Standard
Methods, 4020 B-2011. (1) (c).
Bacteria, Coliform Fecal — Standard Methods, 9222 D-1997 (Aqueous)
Comment: The water level in the water bath was not above the plates on August 15, 2018.
Standard Methods, 9222 D-1997. (2) (d) states: Place prepared dishes in waterproof plastic bags
and seal, invert, and submerge petri dishes in water bath; incubate for 24 ± 2 h at 44.5 ± 0.2°C.
Anchor dishes below water surface to maintain critical temperature requirements. Acceptable
corrective action (i.e., the water level was corrected and a mark indicating the acceptable water
level was added to the water bath interior) was performed by the laboratory and approved by the
auditor during the inspection. No further response is necessary for this corrected Finding.
Comment: The laboratory was not using the required magnification to count fecal coliform
colonies. Standard Methods, 9222 D-1997. (2) (e) states: Count colonies with a low -power (10 to
15 magnifications) binocular wide -field dissecting microscope or other optical device. Acceptable
corrective action (i.e., the analyst began using a 10X microscope to count colonies) was performed
by the laboratory and approved by the auditor during the inspection. No further response is
necessary for this corrected Finding.

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Comment: It was noted that the laboratory was obtaining the pH of the agar when it was still warm
enough to not have solidified. This was considered acceptable.
Comment: It was observed during the inspection that the fecal water bath thermometer was
resting of the bottom of the incubator. This is not ideal, as the heating elements for water baths are
often housed at the bottom. The laboratory placed a stopper on the thermometer during the
inspection to keep it from resting on the bottom.
Recommendation: It is recommended that the laboratory document counts of zero as "0" rather
than "<1". The laboratory would still report a count of 0 colonies as "<1" on the DMR.
NN. Finding: Sample results are not always calculated and reported correctly.
Requirement: Countable Membranes with 20-60 Blue Colonies: Calculate the fecal
coliform results from membrane filters within the ideal counting range of 20-60 blue
colonies using the general formula:
Number of colonies counted x 100 = Fecal coliform colonies per 100 ml
volume of sample filtered in ml
Ref: NC WW/GW LC Policy
Comment: On May 24, 2018 the 100 ml, 10 mL, and 1 mL plates had counts of 3, 2, and 0
colonies respectively. The laboratory reported 8 col/100 mL, but the calculated value should
have been 5 col/100 mL.
Bacteria. Coliform Fecal — Standard Methods, 9222 D-1997 (Aqueous)
Bacteria, Coliform Fecal — Standard Methods 9221 C E-2006 (MPN) 24hr 503 (Non -Aqueous)
00. Finding: The laboratory is not verifying the temperature of the autoclave with a maximum
registering thermometer (MRT).
Requirement: For routine use, verify the autoclave temperature weekly by using a
maximum registering thermometer (MRT) to confirm that 121 °C has been reached. Ref:
Standard Methods, 9020 B-2005. (4) (h).
Requirement: Each laboratory requesting certification must contain or be equipped
with the glassware, chemicals, supplies and equipment required to perform all
analytical procedures included in their certification. Ref: 15A NCAC 02H .0805 (a) (6)
(H).
PP. Finding: The laboratory is not documenting the actual time period at sterilization
temperature and the total run time.
Requirement: Record items sterilized and sterilization temperature, along with total run-
time (exposure to heat) actual time period at sterilization temperature, set and actual
pressure readings, and initials of responsible person for each run cycle. Ref: Standard
Methods, 9020 B-2005. (4) (h).
Nitrogen, Total Kieldahl — Standard Methods, 4500 Narg B-2011 (Standard Methods, 4500
NH3 C-2011) (Aqueous)

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Recommendation: It is recommended that the laboratory switch from Mercuric Sulfate to Cupric
Sulfate as the catalyst for safety and disposal reasons.
QQ. Finding: The laboratory is not standardizing the sulfuric acid titrant monthly.
Requirement: All of the reagents listed for the determination of Nitrogen (Ammonia),
Section 4500-NH3 C.3 are required. Ref: Standard Methods, 4500 No,9 B-2011. (3).
Requirement: Restandardize once a month or when improper storage occurs. Ref:
Standard Methods, 2020 B-2011. (2) (b).
Nitrogen, Nitrate — Standard Methods, 4500 NO3" ®-2011 (Aqueous)
Comment: The laboratory was previously performing analyses using the method of known
addition, although the instrument is capable of reading concentration directly. No explanation of
why this was being performed could be found. The laboratory has recently been contracting this
analysis to a commercial laboratory. The laboratory will be looking into direct calibration and
reading of sample concentration. If the laboratory switches to the method of directly reading
sample concentration, they will need to verify quantitation at the reporting limit upon first use and
on a quarterly basis thereafter.
RR. Finding: The volume of spike solution exceeds 5% of the total MS volume.
Requirement: The volume of spike solution used in MS preparation must in all cases be
5 5% of the total MS volume. It is preferable that the spike solution constitutes <_ 1% of the
total MS volume so that the MS can be considered a whole volume sample with no
adjustment (i.e. volume correction) by calculation necessary. If the spike solution
constitutes >1 % of the total sample volume, the sample concentration must be adjusted by
calculation. Ref: NC WW/GW LC Policy.
Nitrogen, Nitrite — Standard Methods, 4500 NO2- B-2011 (Aqueous)
SS. Finding: The laboratory did not verify quantitation at the reporting level initially, nor is it
verified quarterly.
Requirement: The minimum reporting level (MRL) is set to a concentration at or above the
lowest standard used in the analysis. Verify quantitation at the MRL initially and at least
quarterly (preferably daily) by analyzing a QC Sample (subjected to all sample preparation
steps) spiked at 1 to 2 times the MRL. Laboratories must define acceptance criteria for the
operational range — including the MRL — in their QA documentation. Ref: Standard
Methods, 4020 B-2011. (1) (c).
TT. Finding: The laboratory is not evaluating the recoveries of the back -calculated standards.
Requirement: Each laboratory shall develop and maintain a document outlining the
analytical quality control practices used for the parameters included in their certification.
Supporting records shall be maintained as evidence that these practices are being
effectively carried out. Ref: 15A NCAC 2H .0805 (a) (7).
Requirement: The back -calculated and true concentrations should agree within ± 10%,
unless different criteria are specified in an individual method. At the lower limit of the
operational range, acceptance criteria are usually wider. Such criteria must be defined in
the laboratory's QA plan. Ref: Standard Methods, 4020 B-2011. (2) (a).

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#43 Lexington Regional WWTP Laboratory
UIJ. Finding: A calibration blank and calibration verification standard are not analyzed initially
and at the end of the sample group.
Requirement: The calibration blank and calibration verification standard (mid -range) must
be analyzed initially (i.e., prior to sample analysis), after every tenth sample and at the end
of each sample group to check for carry over and calibration drift. If either fall outside
established quality control acceptance criteria, corrective action must be taken (e.g.,
repeating sample determinations since the last acceptable calibration verification, repeating
the initial calibration, etc.). Ref: NC WW/GW LC Policy.
Comment: The laboratory was occasionally filtering industrial samples that are turbid, but not
filtering compliance samples. The laboratory was told to follow the method for addressing turbidity
as described in Standard Methods, 4500 P E-2011. (4) (b).
W. Finding: The laboratory is not analyzing samples at the correct wavelength.
Requirement: After at least 10 min but no more than 30 min, measure absorbance of each
sample at 880 nm, using reagent blank as the reference solution. Ref: SM 4500 P E-2011
(4) (a).
Comment: The laboratory is analyzing samples at a wavelength of 650 nm.
WW. Finding: The laboratory is zeroing the spectrophotometer improperly.
Requirement: Use a distilled water blank with the combined reagent to make photometric
readings for the calibration curve. Ref: Standard Methods, 4500 P E-2011. (4) (c).
Comment: The laboratory is zeroing the instrument with the digested blank, which does
not give a true indication of whether reagents and the preparatory steps contribute to
measurement uncertainty.
Bacteria, Coliform Fecal — Standard Methods 9221C E-2006 (MPN) 24hr 503 (Non -Aqueous)
Comment: The laboratory is currently analyzing reconstituted dry -weight residue for pH. This is not
required.
XX. Finding: The laboratory is not analyzing 30 grams of sample for analysis.
Requirement: In a sterile dish, weigh out 30.0 grams of well mixed sample. Ref: Control
of Pathogens and Vector Attraction in Sewage Sludge, EPA/625/R-92/013, (July 2003)
Appendix F. (1.1), solid samples (1).
Comment: The laboratory is analyzing 10 g of sample. Decreasing the sample amount
could bias the results since bacteria may not be evenly distributed throughout the compost
pile being sampled.
YY. Finding: The laboratory is not collecting 7 grab samples for analysis.
Requirement: To demonstrate that a given domestic sludge sample meets Class B
Pathogen requirements under alternative 1, the density of fecal coliform from at least seven
samples of treated sewage sludge must be determined and the geometric mean of the
fecal coliform density must not exceed 2 million Colony Forming Units (CFU) or Most

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#43 Lexington Regional WWTP Laboratory
Probable Number (MPN) per gram of total solids (dry weight basis). Ref: Control of
Pathogens and Vector Attraction in Sewage Sludge, EPA/625/R-92/013, (July 2003)
Appendix F. (1) (1.1).
Finding: The pH of the A-1 media is not adjusted and documented to be 6.9 ± 0.1 S.U.
Requirement: Check and record the pH of a portion of each medium after sterilization. If
the pH difference is larger than 0.5 units, discard the batch and check preparation
instructions and pH of reagent water to resolve the problem. Ref: Standard Methods 9020
B-2005 (5) 0) (1).
Requirement: Adjust to pH 6.9 ± 0.1 S.U. Ref: Standard Methods 9221 E-2006 (2)
(a)
Comment: The pH of the media was consistently around 8.0 S.U.
AAA. Finding: The laboratory is not documenting the time required for the autoclave to reach
sterilization temperature.
Requirement: All analytical data pertinent to each certified analysis must be filed in an
orderly manner so as to be readily available for inspection upon request. Ref: 15A NCAC
2H .0805 (a) (7) (A).
Requirement: Use autoclaves of sufficient size to prevent internal crowding; constructed to
provide uniform temperatures within the chamber (up to and including the sterilizing
temperature of 121 °C); and capable of reaching the desired temperature within 15
minutes. Ref: Standard Methods 9030 B-2006 (3)
BBB. Finding: The laboratory is not monitoring the quality of the reagent water.
Requirement: At a minimum, reagent water used to make dilutions, prepare buffered
dilution/rinse water or prepare media must be analyzed at least every twelve months for the
following parameters: Specific Conductance, Total Organic Carbon, Cadmium, Chromium,
Copper, Nickel, Lead, and Zinc.
Maximum Acceptable Limits are:
Total Organic Carbon < 1.0 mg/L
Specific Conductance < 2 pmhos/cm
Heavy Metals, single element < 0.05 mg/L
Heavy Metals, Total of specified elements < 0.10 mg/L
If the facility is using vendor purchased reagent water or dilution/rinse water, this testing is
not required as long as the Certificate of Analysis from the manufacturer meets these
requirements and is kept on file. Ref: NC WW/GW LC Policy.
CCC. Finding: The drying cycle is not repeated for an additional 1 hour on the second day.
Requirement: Place in an oven at 103 to 105°C overnight. Cool to balance temperature in
a desiccator and weigh. Repeat drying (1 h), cooling, weighing, and desiccating steps until
weight change is less than 4% or 50 mg, whichever is less. Ref: Standard Methods, 2540
G-2011 (3) (a) (2) (b).

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#43 Lexington Regional WWTP Laboratory
Comment: The laboratory is drying samples overnight but is not repeating the 1 hour
drying cycle to verify that the samples are at constant weight.
DDD. Finding: The "largest volume" value used in the MPN calculation is not properly
determined.
Requirement: Compute the MPN/g according to the following equation:
Ref: Control of Pathogens and Vector Attraction in Sewage Sludge, EPA/625/R-92/013,
(July 2003) Appendix F. (1.1), liquid samples (6).
Comment: The "largest volume" in the calculation above is the volume of the original
solution (30 g in 270 ml) that is in 1 mL of the mixture that is incubated. The laboratory
combines 10 mL of the original solution with 10 mL of media. This new 20 mL solution has
10 mL of the original solution. Therefore, you have 0.50 ml of original sample in 1 ml of the
new solution that gets incubated. In this case, the "largest volume" value that is used in the
calculation is 0.50 mL. The laboratory was using a volume of 10 mL in the calculation.
BOD — Standard Methods, 5210 B-2011 (Aqueous)
Recommendation: It is recommended that the laboratory analyze a seeded blank to check the
calculated seed correction factor (SCF).
Recommendation: It is recommended that the sample pH values be documented on the BOD
worksheet, rather than the Laboratory Worksheet for Plant Analysis.
EEE. Finding: Extra nutrient, mineral, and buffer solutions are not added to the Biochemical
Oxygen Demand (BOD) bottles containing more than 67% (i.e., > 201 mL) sample.
Requirement: When a bottle contains more than 67% of the sample after dilution,
nutrients may be limited in the diluted sample and subsequently reduce biological activity.
In such samples, add the nutrient, mineral, and buffer solutions (3a through e) directly to
diluted sample at a rate of 1 mUL (0.30 mU300-mL bottle) or use commercially -prepared
solutions designed to dose the appropriate bottle size. Ref: Standard Methods, 5210 B-
2011. (5) (c) (2).
FFF. Finding: The laboratory is not evaluating the drift check of the Dissolved Oxygen (DO)
meter to demonstrate the analytical process is in control and the established criteria are
met.
Requirement: If the membrane electrode method is used, take care to eliminate drift in
calibration between initial and final DO readings. Ref: Standard Methods, 5210 B-2011. (5)
(g)•
Requirement: Immediately after calibration, measure the DO of a BOD bottle of dilution
water. Stopper the bottle. Document the concentration on the benchsheet (day one initial
drift check). At the end of the sample set reanalyze the drift check bottle and document the
concentration (day one final drift check). The laboratory should verify the DO Meter
calibration throughout the sample set if needed. Repeat process on Day 5. If the meter

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#43 Lexington Regional WWTP Laboratory
drifts more than 0.20 mg/L, recalibrate meter and reanalyze all samples since the last drift
check. Ref: NC WW/GW LC Policy.
Comment: The laboratory was checking the drift at the beginning and end of the run with
the probe and documenting the results, but not evaluating the results of the drift check.
Examination of past benchsheets showed that the final drift check value was always within
± 0.2 mg/L of the initial drift check.
Residue, Total — Standard Methods, 2540 B-2011 (Aqueous)
Residue, Suspended — Standard Methods, 2540 D-2011 (Aqueous)
Recommendation: It is recommended that the laboratory use a tiered acceptance criterion for
duplicates that better evaluates the results at each sample location. In this case, 20% relative
percent difference (RPD) would be appropriate for the smaller values of routine effluent samples,
while 10% RPD would be better suited for the larger values characteristic of influent samples.
Recommendation: It is recommended that the laboratory relabel "mLs" to "sample volume (mL)"
and "mg/L" to "results (mg/L)" on the laboratory benchsheet.
GGG. Finding: The samples are not weighed to constant weight, nor is an annual drying study to
verify the adequacy of the drying time, performed.
Requirement: Constant weights must be documented. The approved methods require the
following: "Repeat the cycle of drying, cooling, desiccating, and weighing until a constant
weight is obtained or until the weight change is less than 4% of the previous weight or 0.5
mg, whichever is less." In lieu of this, an annual study documenting the time required to
dry representative samples to a constant weight may be performed. Verify minimum daily
drying time is greater than or equal to the time used for the initial verification study drying
cycle. Drying cycles must be a minimum 1 hour for verification. Ref: NC WW/GW LC
Policy.
Residue, Total — Standard Methods, 2540 B-2011 (Aqueous)
Recommendation: It is recommended that the laboratory purchase and use a 50 mL wide bore
pipet to measure 50 mL of sample, rather than using a 25 mL wide bore pipet multiple times.
HHH. Finding: The laboratory does not report results of all tests on the characteristics of the
effluent.
Requirement: The results of all tests on the characteristics of the effluent, including but
not limited to NPDES permit monitoring requirements, shall be reported on the monthly
report forms. Ref: 15A NCAC 2B .0506 (b) (3) (J).
Comment: The laboratory is analyzing influent and effluent samples for Total Residue, but
this parameter is not on the permit and is not being reported on the DMR.
Residue, Suspended — Standard Methods, 2540 D-2011 (Aqueous)
Comment: The laboratory was not analyzing a volume of sample to yield a minimum of 2.5 mg
dried residue. Standard Methods, 2540 D-2011 (3) (b) states: Choose sample volume to yield
between 2.5 and 200 mg dried residue. Acceptable corrective action (i.e., the laboratory began
analyzing larger volumes in order to achieve the necessary minimum residue weight after receiving
the parameter checklist prior to the inspection) was performed by the laboratory and approved by
the auditor during the inspection. No further response is necessary for this corrected Finding.

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III. Finding: The laboratory is not weighing filters to constant weight or analyzing a dry filter
blank daily.
Requirement: If pre -prepared filters are not used, the method requires that filters must be
weighed to a constant weight after washing. Repeat cycle of drying, cooling, desiccating,
and weighing until a constant weight is obtained or until weight change is less than 4% of
the previous weighing or 0.5 mg, whichever is less. In lieu of this process, it is acceptable to
analyze a single daily dry filter blank to fulfill the method requirement of drying all filters to a
constant weight prior to analysis. Ref: NC WW/GW LC Policy.
JJJ. Finding: The laboratory is not basing the reporting limit on the minimum weight gain
required by the method.
Requirement: Choose sample volume to yield between 2.5 and 200 mg dried residue. To
obtain the required residue yield, successive aliquots of samples may be added to the
same dish after evaporation or adjust reporting level based upon the weight gain and
sample volume used. The minimum reporting value is established at 2.5 mg/L based upon
a sample volume used of 1000 mL. Ref: NC WW/GW LC Policy.
Comment: For example, for an effluent sample collected January 5, 2018, 500 mL of
sample was filtered, and a value of 2.47 mg/L was reported on the DMR, instead of <5
mg/L.
Metals — Standard Methods, 3120 B-2011 (Aqueous)
Comment: The laboratory's acceptance criterion for the LFB is 85-115%, which is required by
Standard Methods, 3020 B-2011 (3) (b). However, Standard Methods 3120 B-2011 (4) (f) says that
"results should agree to within 5% of the certified values". While QC criteria written in the method
supersede that found in 3020, 85-115% recovery may be used in this case because the method
states that it "should" be within 5%, which is considered a, recommendation.
KKK. Finding: The laboratory is not analyzing a Calibration Blank immediately after calibration
and after each sample.
Requirement: Begin each sample run with an analysis of the calibration blank, then
analyze the method blank. Analyze samples, alternating them with analyses of calibration
blank. Subtract result of an adjacent calibration blank from each sample result to make a
baseline drift correction. Ref: Standard Methods, 3120 B-2011 (4) (d) and (5) (a).
Comment: The laboratory was analyzing a calibration blank at the end of the sample set.
LLL. Finding: The laboratory is not analyzing a method blank prior to sample analysis.
Requirement: Begin each sample run with an analysis of the calibration blank, then
analyze the method blank. Ref: Standard Methods, 3120 B-2011. (4) (d).
Comment: The laboratory was analyzing a method blank at the end of the sample set.
MMM. Finding: The laboratory is not analyzing an Instrument Check Standard (ICS) prior to
sample analysis and after every ten samples.
Requirement: Before analyzing samples, analyze instrument check standard.
Concentration values obtained should not deviate from the actual values by more than ±

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#43 Lexington Regional WWTP Laboratory
5% (or the established control limits, whichever is lower). Ref: Standard Methods, 3120 B-
2011 (4) (c).
Requirement: Analyze instrument check standard once per ten samples to determine if
significant instrument drift has occurred. If agreement is not within ± 5% of the expected
values (or within control limits, whichever is lower), terminate analysis of samples, correct
problem, and recalibrate instrument. Ref: Standard Methods, 3120 B-2011 (4) (e).
Comment: The laboratory was analyzing the ICS at the end of the sample set, which is
also required.
Comment: The ICS is equivalent to the Calibration Verification Standard (CVS). It is an
undigested standard from the same source as the calibration curve.
NNN. Finding: The laboratory's acceptance criterion for the ICS does not meet the method
requirements.
Requirement: Before analyzing samples, analyze instrument check standard.
Concentration values obtained should not deviate from the actual values by more than ±
5% (or the established control limits, whichever is lower). Ref: Standard Methods, 3120 B-
2011. (4) (c).
Requirement: Analyze ICS once per 10 samples to determine if significant instrument drift
has occurred. If agreement is not within ± 5% of the expected values (or the established
control limits, whichever is lower), terminate analysis of samples, correct problem and
recalibrate instrument. Ref: Standard Methods, 3120 B-2011. (4) (e).
Comment: The laboratory's acceptance criterion of the ICS is 90-110%.
000. Finding: The laboratory is not performing a Reporting Limit Verification (RLV) by analyzing
a reporting limit check solution before sample analysis.
Requirement: Reporting limit verification (RLV): Verify with each calibration that the
instrument is capable of accurately quantifying at the reporting limit. Prepare reporting limit
check solution (RLCS) at the reporting limit concentration, or lower, and analyze it after
calibration but before any samples are analyzed. Ref: Standard Methods, 3020 B-2005. (2)
(e).
Comment: The laboratory performs the RLV at the end of the sample set.
PPP. Finding: The calibration standards are not being prepared properly.
Requirement: Combine appropriate volumes of the stock solutions in 100-mL volumetric
flasks. Add 2 mL 1+1 HNO3 and 10 mL 1+1 HCL and dilute to 100 mL with water. Ref:
Standard Methods, 3120 B-2011. (3) (e).
Comment: The laboratory was adding 2 mL of concentrated HNOsto standard solutions.
QQQ. Finding: The laboratory is not adjusting the sample concentration in the percent recovery
calculation when the spike volume is >1 % of the total sample volume.
Requirement: The volume of spike solution used in MS preparation must in all cases be <_
5% of the total MS volume. It is preferable that the spike solution constitutes <_ 1 % of the
total MS volume so that the MS can be considered a whole volume sample with no

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#43 Lexington Regional WWTP Laboratory
adjustment (i.e., volume correction) by calculation necessary. If the spike solution volume
constitutes >1 % of the total sample volume, the sample concentration must be adjusted by
calculation. Ref: NC WW/GW LC Policy.
Comment: The laboratory is using 5% spike solution per total volume to prepare the
LFM/LFMD.
RRR. Finding: The laboratory is not reanalyzing one or more samples near the end of the
analytical run.
Requirement: Reanalyze one or more samples analyzed just before termination of the
analytical run. Results should agree to within ± 5%, otherwise all samples analyzed after
the last acceptable instrument check standard analysis must be reanalyzed. Ref:
Standard Methods, 3120 B-2011. (4) (e).
Comment: The laboratory performed a duplicate analysis on the first sample in the sample
set, but this is a true duplicate, not simply a reanalysis as required above.
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 Lexington Regional WWTP
Laboratory NPDES permit # NC0055786 for October 2017, January 2018 and May 2018. The
following errors were noted:
Value on Benchsheet
Date
Parameter
Location
Value on DMR
*Contract Lab Data
5/1/2018
Cyanide
Effluent
< 5 pg/L*
5 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 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: Michael Cumbus Date: August 29, 2018
Report reviewed by: Anna Ostendorff Date: September 14, 2018

Weight Verification (NC WW/GW LC Policy 05/23/2008)
ASTM Class 1 and 2 weights must be verified at leastevery5 years. ASTMClass1 weights (20 g to 25 -
kg) and ASTM Class 2 weights (10 g to 1 mg) are equivalent to the NBS Class S weights specified in
15A NCAC 2H .0805 (a) (7) (K). Verification may be accomplished by:
1. Sending laboratory weights back to the manufacturer for recertification - reference weights shall
be calibrated by a body that can provide traceability to ASTM specifications, or
2. Checking laboratory weights against certified reference weights (i.e., weights that have been
recertified as above) and found to be within ASTM Class 1 or Class 2 tolerances (see table
below) - often the balance service technician may provide this service.
Note: Although some manufacturers will assign a one-year calibration due date, 5 years is considered
an acceptable calibration interval due to the limited use of the reference weight set.
Documentation of weight verifications or recertification must be maintained for 5 years. If the condition
of a weight(s) is in question at any time due to damage (e.g., corrosion, nicks, scratching, etc.), the
laboratory must have that weight(s) re -verified as described above.
Maximum tolerances (Ref. ASTM E 617-97, 2003)
Denomination
Maximum tolerance for
ASTM Class 1 and 2
weights, (± mg)
500 g
1.2
300 g
0.75
200 g
0.50
100 g
0.25
50 g
0.12
30 g
0.074
20 g
0.074
log
0.074
5 g
0.054
3 g
0.054
2 g
0.054
1 g
0.054
500 mg
0.025
300 mg
0.025
200 mg
0.025
100 mg
0.025
50 mg
0.014
30 mg
0.014
20 mg
0.014
10 mg
0.014
5 mg
0.014
3 mg
0.014
2 mg
0.014
1 mg
0.014

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