#5190_2017_1121_TLH_FINAL

INSPECTION REPORT ROUTING SHEET
To be attached to all inspection reports in-house only.
Laboratory Cert. #:
5190
Laboratory Name:
G.C. Environmental, Inc.
Inspection Type:
Field Commercial Maintenance
Inspector Name(s):
Tom Halvosa and Todd Crawford
Inspection Date:
November 21, 2017
Date Forwarded for Initial
Review:
December 1, 2017
Initial Review by:
Beth Swanson
Date Initial Review
Completed:
December 4, 2017
Cover Letter to use:
❑ Insp. Initial
❑Insp. No Finding
❑Corrected
® Insp. Reg
❑Insp. CP
❑Insp. Reg. Delay
Unit Supervisor/Chemist III:
Todd Crawford
Date Received:
December 8, 2017
Date Forwarded to Admin.:
December 12, 2017
Date Mailed:
December 12, 2017
Special Mailing Instructions:

Water Resources
ENVIRONMENTAL. QUALITY
December 12, 2017
5190
Mr. Guido J. Carrara
G.C. Environmental Inc.
5312 Pinewood Ct.
Wendell, NC 27591
ROY COOPER
MICHEAL S. REGAN
S. JAY ZIMMERMAN
Subject: North Carolina Wastewater/Groundwater Laboratory Certification (NC WW/GW LC)
Maintenance Inspection
Dear Mr. Carrara:
Enclosed is a report for the inspection performed on November 21, 2017 by Tom Halvosa. 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] ext. 251.
Sincerely,
Todd Crawford
Technical Assistance & Compliance Specialist
NC WW/GW Laboratory Certification Branch
Attachment
cc: Dana Satterwhite, Tom Halvosa, Master File # 5190
Water Sciences Section
NC GVastewater/Groundwater Laboratory Certification Branch
1623 ttilail Service Center, Raleigh, North Carolina 27699-1623
Location: 4405 Reed; Creek Road, Raleigh, North Carolina 27607
Rhone: 919-733-3906', FAX; 919-733-6241
nternet: http:lldeg.nc.gov/abouVd!visions/water•resources(water-resources-data/water-sciences-home-pagellaborato ry-certification-branch

LABORATORY NAME: G.C. Environmental, Inc.
WATER QUALITY PERMIT #: WQ0000233, WQ0007102 and WQ0001203
ADDRESS: 5312 Pinewood Ct.
Wendell, NC 27591
CERTIFICATE #: 5190
DATE OF INSPECTION: November 21, 2017
TYPE OF INSPECTION: Field Commercial Maintenance
AUDITORS: Tom Halvosa and Todd Crawford
LOCAL PERSON CONTACTED: Guido Carrara
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 environmental samples.
II. GENERAL COMMENTS:
The facility has all the equipment necessary to perform the analyses. Staff were forthcoming and
seemed eager to adopt necessary changes.
All required Proficiency Testing (PT) Samples have been analyzed for the 2017 PT Calendar Year
and the graded results were 100% acceptable.
Contracted analyses are performed by Pace Analytical Services, LLC — Raleigh NC (Certification
# 67).
Quality Assurance Policies for Field Laboratories and 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:
Documentation
A. Finding: The laboratory benchsheet was lacking pertinent data: instrument identification.
Requirement: The following must be documented in indelible ink whenever sample
analysis is performed: Instrument Identification and Thermometer/Instrument Identification.
Ref: NC WW/GW LC Approved Procedure for the Analysis of Total Residual Chlorine, NC
WW/GW LC Approved Procedure for the Analysis of Dissolved Oxygen, NC WW/GW LC

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#5190 G.C. Environmental, Inc.
Approved Procedure for the Analysis of Temperature and NC WW/GW LC Approved
Procedure for the Analysis of pH.
B. Finding: Error corrections are not always properly performed.
Requirement: All documentation errors must 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. Write the correction adjacent
to the error. The correction must be initialed by the responsible individual and the date
of change documented. Ref: Quality Assurance Polices for Field Laboratories.
C. Finding: The laboratory needs to increase the traceability documentation of purchased
materials and reagents.
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. 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
chemicals, reagents, standards and consumables used for a period of five years.
Consumable materials such as pH buffers and lots of pre -made standards are included
in this requirement. Ref: Quality Assurance Policies for Field Laboratories.
Comment: Traceability documentation did not include vendor name. An example receipt
log was given to the laboratory for use in the future to help record all pertinent
traceability information.
Proficiency Testing
D. 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 the preparation of the Total
Residual Chlorine PT Sample would satisfy the documentation requirement.
E. Finding: The laboratory is not documenting RT Sample analyses in the same manner as
routine Compliance Samples.
Requirement: As specified in 15 NCAC 2H .0800, in order to meet the minimum
standards for Certification, laboratories must use acceptable analytical methods. The
acceptable methods are those defined or referenced in the current State and federal

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#5190 G.C. Environmental, Inc.
regulations for the environmental matrix being tested. All samples, (including PT
Samples) that are, or that may, be used for Certification purposes, must be analyzed
using approved methods only. All PT Samples are to be analyzed and the results
reported in a manner consistent with the routine analysis and reporting requirements of
Compliance Samples. Laboratories must document any exceptions. 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,
May 31, 2017, Revision 2.0.
Comment: The analysis of PT Samples is designed to evaluate the entire process used
to routinely report Compliance Sample results; therefore, PT Samples must be analyzed
and the process documented in the same manner as Compliance Samples.
Chlorine, Total Residual — Standard Methods, 4500 Cl G-2000 (Aqueous)
F. Finding: The laboratory is not verifying the instrument's factory -set curve every 12
months.
Requirement: Zero the instrument with chlorine -free water and then analyze a reagent
blank (i.e., reagent water plus buffer and DPD) and a series of five standards. The curve
verification must bracket the range of the samples to be analyzed. This type of curve
verification must be performed at least every 12 months. The values obtained must not
vary by more than 10% of the known value for standard concentrations greater than or
equal to 50 pg/L and must not vary by more than 25% of the known value for standard
concentrations less than 50 pg/L. The reagent blank concentration must not exceed half
the concentration of the lowest standard. The overall correlation coefficient of the curve
must be >_0.995. Ref: NC WW/GW LC Approved Procedure for the Analysis of Total
Residual Chlorine.
Comment: The regular -level curve has never been verified on the current meter. The
analyst assumed no 5-standard calibration verification curve was necessary for regular -
level Total Residual Chlorine (TRC) analysis using the Hach Pocket Colorimeter due to
a miscommunication during a previous Inspection.
Comment: The laboratory is not currently analyzing Compliance Samples for TRC. If a
gel -type standard is used for the daily calibration check, a true value needs to be
assigned before Compliance Samples are analyzed.
Temperature — Standard Methods, 2550 B-2000 (Aqueous)
G. Finding: Temperature sensor check readings for devices used for compliance monitoring
varied more than 0.5°C from the National Institute of Standards and Technology (NIST)
traceable thermometer reading.
Requirement: All thermometers and temperature measuring devices used for compliance
monitoring must be checked every 12 months against a NIST traceable temperature
measuring device and the process documented. To check a thermometer or temperature
sensor of a meter, read the temperature of the thermometer/meter against a NIST
traceable temperature measuring device and record the two temperatures. The verification
must be performed in the approximate range of the sample temperatures measured. The
thermometer/meter readings must be less than or equal to 0.5°C from the NIST
traceable temperature measuring device reading. If it is, no correction factor would be

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#5190 G.C. Environmental, Inc.
IV.
applied. If it is not, the thermometer/meter may not be used for compliance monitoring.
The calibration verification documentation must include the serial number of the
thermometer/meter being checked and the NIST traceable temperature measuring device
that was used in the comparison. Document the verification data and keep on file. (NOTE:
Other Certified laboratories may provide assistance in meeting this requirement.) Ref:
NC WW/GW LC Approved Procedure for the Analysis of Temperature.
Comment: On August 10, 2017, the analyst performed multiple checks at different
temperatures. One check showed a 0.7°C difference between the NIST thermometer and
pH meter temperature sensor while other checks were within the 0.5°C acceptance
criterion.
PAPER TRAIL INVESTIGATION:
The paper trail consisted of comparing original records (e.g., laboratory benchsheets, logbooks,
etc.) and contract lab reports to eDMRs submitted to the North Carolina Division of Water
Resources. Data were reviewed for G.C. Environmental, Inc. (Water Quality permits #
W00001203, WQ0007102 and WQ0000233). The following errors were noted for WQ0000233:
Value on
Date
Parameter
Location
Benchsheet
Value on DMR
*Contract Lab Data
2/22/2016
Fecal Coliform
MW #1
*4.0 #/100mL
< 4.0 #/100mL
2/22/2016
Fecal Coliform
MW #2
*4.0 #/100mL
< 4.0 #/100mL
Please refer to attached document, Precision in Discharge Monitoring Reports, for further
guidance on handling less -than values on eDMRs.
To avoid questions of legality, it is recommended that you contact the appropriate Regional
Office for guidance as to whether an amended eDMR(s) will be required. A copy of this report
will be made available to the Regional Office.
V. CONCLUSIONS:
Correcting the above -cited Findings will help this laboratory to produce quality data and meet
Certification requirements. The inspector would like to thank the staff for its assistance during the
inspection and data review process. Please respond to all Findings and include supporting
documentation and implementation dates for each corrective action.
Report prepared by: Tom Halvosa
Report reviewed by: Beth Swanson
Date: December 1, 2017
Date: December 8, 2017

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Borth Carolina Department of Environment and Natural Resources
® Division of Water Resources "'aAMINNENNEMWater Permitting Section
NCDENRWastewater Branch
Precision in Discharge Monitoring Reports
August 3, 2015
1. INTRODUCTION
The results of monitoring required in wastewater permits must be reported as precisely as
reasonably possible in order to enable the accurate determination of compliance with permit
limits. Significant figures are an established means of expressing the precision of monitoring
results.
This document provides guidance to promote the consistent use of significant figures in
preparing Discharge Monitoring Reports (DMRs).
• Section 2 describes the use of significant figures, decimal places, and rounding to indicate
precision in numbers. It also notes certain exceptions to the usual conventions for their use.
• Section 3 describes the proper use of significant figures in entering data on DMR forms.
• Section 4 describes special considerations for reporting mass loads, both for individual
discharges and for groups of discharges subject to collective limits.
• The Appendices contain additional supporting information and sample calculations.
2. COMMON CONVENTIONS
2.1 Types of Numeric Values
Numeric values can be broadly classified as approximate or exact.
• All measurements are approximate values. The true precision of a measurement
depends on several factors, including the method and equipment used, operator
performance, and environmental conditions.
• Exact values are counted numbers or other values known with certainty or accepted as
given.
Both types of values are used in wastewater permitting, and each affects the precision of
monitoring results differently.
2.2 Significant Figures
There is uncertainty in any measurement. Results must be recorded as precisely as reasonably
possible; or, as Standard Methods states it, "All digits in a reported result are expected to be
known definitely, except for the last digit, which may be in doubt. Such a number is said to
contain only significant figures."' Thus, the precision of a measurement is indicated by the
number of significant figures (SFs) in the recorded result. Table 1 summarizes the standard
conventions for counting significant figures:
1 APHA/AWWA/WEF, Standard Methods for the Examination of Water and Wastmater, 22nd Edition, 2012, Part 1050 B.
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Precision in Discharge Monitoring Reports
August 3, 2015
Table 1: Conventions for Determining Significant Figures
Conventions
Example
Significant
Values !
Figures
23
2
1. Non -zero digits (1-9) are significant.
231
3
4308
4
2. Zeros between non -zero digits are significant.
40.05
4
3. Zeros to the left of the first non -zero digit are not significant.
0.00253
3
4. Trailing zeros (the right -most zeros) are significant in numbers that
0.360
3
4.00
3
have a decimal point.
5. Trailing zeros are ambiguous in numbers with no decimal point and
require explanation to establish the number's precision.
470,000
2 to 6
Values with ambiguous zeroes can be expressed in different ways to eliminate the ambiguity.
For example, if the value '470,000' is known to have 3 SFs, it could be recorded as'4.70 x 105',
'470,000 ± 500', or '470,000, accurate to the nearest thousand'.
Proper use of significant figures ensures that results are recorded to their full and true precision.
Recording less precise results (for example, using one reporting value when a lower value could
be justified) censors potentially useful information. On the other hand, recording results with
non -significant figures implies a greater precision than is justified and can be misleading.
Note: In the examples given in this document, the underlined digit in a number (such as the
in 3.831) is the last significant figure in the number, and any digits to its right are non -significant.
2.3 Decimal Places
The number of decimal places (DPs) is another indication of a value's precision and is used
instead of significant figures in some situations. Decimal places are typically counted to the
right of the decimal place (tenths, hundredths, thousandths, etc.) but can also be counted to the
left (10s, 100s, 1000s, etc.).
Appendix A lists typical levels of precision (as SFs and as DPs) for common wastewater
parameters.
2.4 Rounding
Rounding is the process of removing non -significant digits from a number. The two steps in
rounding are to:
• Step 1: Drop all non -significant figures but the left -most one, then
• Step 2: Drop the last remaining non -significant figure and modify the final significant
figure (or not) according to the standard conventions summarized in Table 2.
Column 2 of Table 2 shows the rounding conventions established in Standard Methods for the
recording of analytical results. Column 3 shows the conventions for rounding the results of
calculations. The two are similar except when the final digit to be dropped is a'S'. Standard
Methods rounds up or down to the nearest even number (Convention 3.a.), while calculated
values are simply rounded up (3.b.), consistent with the rounding conventions used in most
handheld calculators and computer software applications.
2

Precision in Discharge Monitoring Reports
August 3, 2015
Table 2: Conventions for Rounding of Measured and Calculated Values
Examples (Rounded to 2 SFs)
Conventions for Rounding
Measured Values
Calculated' Values
1.10 1.1
1. If the digit being dropped is 0, 1, 2, 3 or 4, leave the
1.11 1.1
preceding number as is.
1.12 1.1
Same
1.13 1.1
1.14 1.1
1.16 1.2
2. If the digit being dropped is 6, 7, 8 or 9, increase the
1.17 1.2
preceding digit by one.
1.18 1.2
Same
1.19 1.2
3. If the digit being dropped is 5,
a. For measurements: Round the preceding digit to
1.15 4 1.2
the nearest even number (0 is considered as even).
b. For calculations: Round the preceding digit up.
1.25 -> 1.3
Example: A result of 5.124315 is known to be precise to 3 SFs,
Last SF + 1 Non-SFs
non -SF
To round this value, truncate the reading to 5.124 (keeping one non -SF),
then round to 5.12 per Convention 1 in Table 2.
2.5 Exact Values
Exact values are known (or accepted) with certainty. Thus, the concept of precision and the
conventions for significant figures and decimal places do not apply to exact numbers.
Exact values in wastewater permitting include:
• Counted vahtes, such as:
i. Bacteria measurements (cfu)
ii. Numbers of samples
iii. Values denoting time (days, months, etc.)
• Conversion factors are, in many cases, commonly accepted as exact numbers and are not
considered in rounding.
• Design flow of a treatment facility. The design flow represents the actual treatment capacity
for which a facility was designed, not more, not less. For permitting purposes, it is
usually the same as the flow limit in the facility's discharge permit.
• Values below the Practical Quantitatim Limit. Where non -detect results (<PQL) are treated
as zero when calculating an average (or one, for geometric means), those zeroes (or
ones) do not affect the number of significant figures in the result.
• Mass Allocations/Limits f oin a TMDL. For permitting purposes, the Wasteload Allocation
(WLA) established in a TMDL or similar study is considered an exact value.
3

Precision in Discharge Monitoring Reports
August 3, 2015
2.6 Precision in Calculations
Just as there is uncertainty in any measurement, there is uncertainty in any calculation that
involves measured values. The precision of each value must be taken into account in order to
determine the precision of the calculated results. The following conventions describe how
precision is determined in different types of calculations.
Significant figures, decimal places, and rounding are again used to indicate the precision of
measured values. Exact values are treated differently in calculations, as described later. It is
necessary to distinguish between measured (that is, approximate) and exact values, as they
affect the precision of the calculated results differently.
Approximate Values in Calculations. The following conventions (or rules) are used to
determine significant figures and decimal places when approximate values are used in
calculations.
Calculation Rule #1 - Multiplication, Division, or Roots: The number of significant figures in
the result is equal to the least number of significant figures in the measured values used in
the calculation.
Example:
2.5 x 3.47 = 8.675 --> 8.7
In this case, two measurements are multiplied. 2.5 has fewer significant figures (2 SFs)
than does 3.47 (3 SFs), so the final result is rounded to two significant figures: 8.7.
Calculation Rule #2 - Addition or Subtraction: The number of decimal places (DPs) in the
result is equal to that of the least precise value used in the calculation. h1 contrast to Rule 1,
the measure of precision is the number of decimal places, not significant figures.
Example:
13.691-0.5=13.191—>13.2
In this case, 0.5 has one decimal place and is less precise than 13.691 (3 DP), so the final
answer is rounded to one decimal place: 13.2.
Calculation Rule #3 - Multiple Operations: The number of significant figures in the result of
multiple calculations is determined by applying both Rules 1 and 2. All Rule 1 operations
are conducted, then followed by Rule 2 operations.
Note: Rounding of intermediate results can result in rounding errors and loss of precision;
therefore, only the final result of multiple calculations is rounded.
Example: (2.5 x 3.47) + 13.691 - 0.5
Step 1: Multiplication- use Rule 1: 2.5 x 3.47 = 8.675 (2 SFs)
Step 2: Addition - use Rule 2: 8.675 + 13.691= 22.366 (1 DP)
Step 3: Subtraction - use Rule 2: 22.366 - 0.5 = 21.866 (1 DP)
Step 4: Round final result: 21.866 - > 21.86 --> 21.9 (1 DP)
Example: 4-\/ 89 x 229 x 164 x 73 = 124.982... = 120
To calculate this geometric mean, the least precise number has two significant figures, so
the result is rounded to 2 SFs: 120.
4

Precision in Discharge Monitoring Reports
August 3, 2015
Tip: Preserving intermediate results in their entirety could quickly become burdensome. In
practice, this can be made manageable:
Spreadsheets. By default, spreadsheets and calculators retain all figures in intermediate
results, limited only by the capabilities of the software or device. It is only necessary to
note the final result and round as necessary.
Carry an extra digit. If calculations are performed step -wise and the intermediate results
are recorded at each step, it is acceptable to carry forward the significant figures plus
two or three non -significant digit (rather than all digits) through the calculations.
With either approach, it is still necessary to track the right -most significant digit in each
intermediate step (as in the examples just given) to ensure that the final result is rounded to
the correct precision.
Exact Values in Calculations. Exact values are, by definition, known with certainty and so do
not affect the number of significant figures (or decimal places) in calculated results.
Example: 3.27 mg/L TP x 5 MGD x 8.34 = 5.4544 = 5.45 lb/day TP
In this case, the Average Design Flow (5 MGD) and the conversion factor (8.34) are both
exact values, so the number of significant figures in the TP concentration determines the
precision of the final result.
Exception - Averages. Averages are an exception to the rounding rules. Consider the arithmetic
average of three values:
9.24 + 8.31 + 8.86 = 26.41 (2 DPs (Calculation Rule #2))
26.41 / 3 = 8.803333 — 8.803 (4 SF (Calculation Rule #1))
By Rule 1, the sum of the values is precise to two decimal places and, in this case, four
significant figures. The divisor ('3') is an exact value, so the average would also have four
significant figures, or one more decimal place than the original values. The increase in precision
is not justified. Regardless of the rounding rules, averages should be no more precise than the
least precise value in the data set. In this case, the result would be rounded to 8.80 (3 SFs).
Appendix B provides additional sample calculations illustrating the use of these conventions.
3. PRECISION IN DISCHARGE MONITORING REPORTS
3.1 Data Entry in DMRs
Permittees record three types of values on the DMR form: daily measurements, statistical data
(average, maximum, minimum), and permit limits. The location and expected precision of each
type of data are as follows and as illustrated in Figure 1:
• Daily results (Days 1-31) are entered in the main section of the DMR table.
o Daily analyses must be performed using EPA -approved methods that are capable of
producing results less or equal to than the corresponding permit limits, where such
5

Precision in Discharge Monitoring Reports
August 3, 2015
methods exist.2 In the case of 'non -detect' values, permittees (or their laboratories) are
expected to report daily values to the Practical Quantitation Level (PQL) for each
parameter (or "<[PQL]" for values less than the PQL).
• Daily values are reported to the same precision as the field or laboratory result.
• Daily results calculated from other daily values (for example, Total Nitrogen as the
sum of TKN and NO3-N + NO2-N) are rounded according to the conventions for
calculated numbers given in Column 3 of Table 2.
D Some calculated values, such as mass loads, require special attention and are
addressed further in Section 4. Monthly, annual, and other loads are reported as
'daily' values and entered under the proper parameter code to indicate the time
period.
Figure 1. Discharge Monitoring Report Form MR-1
EFFLUENT
INDES FERMTTNO, DISCHARGE NO.
MONTH YEAR
FACILITY IIAME
CLASS ODNIFIY
CERTIFIED LAEORATORY (l)_
CERTIFICATION NO.______
_
(Hst additiwl IA-tmi. onNeludaidapage z d this f—)
OPERATOR IN RESPONSIBLE CHARGE(ORQ_
GRADE_ CERTIFICATION 110.___
PERSON(S) COLLECTUMAMPLES
ORCPHONE______
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NO ILOW lDIS[HAIGL IEON SRL• O
MmlUMNAL and UNEW D:
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W7D 00010 W00 WOW on 0% W530 31616 1 00300 I mm Om
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3`3 F G ROW
Measured results from field tests or
laboratory: include all significant
figures as reported.
Statistical/ calculated results —
averages, max/min: report no fewer
significant figures than in permit limit.
Effluent limitations — record as stated
in the wastewater permit.
EA QFam FR.1(11"
• Statistical vnhces calculated for compliance purposes (Monthly and Weekly Averages,
Daily Maximum, Daily Minimum) are entered in the lower section of the DMR table.
D Statistical values are rounded according to the conventions described in Section 2.
2 When such methods do exist and results are not sufficiently sensitive, the permittee must provide an explanation in
the comments section of the DMR form.
31

Precision in Discharge Monitoring Reports
August 3, 2015
Statistical values are reported with no fewer significant figures than found in the
permit limit (with the exception of annual mass loads or similar limits; see Section 4).
® Pennit limits are also entered on the lower section of the DMR table, above or below the
statistical data (location depends on the form used).
o Limits are entered as expressed in the permit.
3.2 Compliance Determinations
Compliance with permit limits is determined by comparing the statistical values for each
parameter with the corresponding effluent limits. Strictly speaking, the statistical values for
each parameter should be rounded to the same precision as its limit(s) before the comparison is
made. However, this is only necessary if the statistical value is very close to the limit. If the
monthly average limit for NH3-N is 4.0 mg/L and the actual average for the month is 2.68
mg/L, we do not have to round the average to 2.7 mg/L (2 SFs,1 DP) to accurately conclude
that the discharge met the limit. But if the actual average is 4.03 mg/L instead, proper rounding
is essential; without it, one would incorrectly conclude that the discharge exceeded its limit.
Example - Compliance: Without rounding: 4.03 mg/L actual > 4.0 mg/L limit
Fielding: Violates limit
With rounding: 4.03 — 4.0 mg/L = 4.0 mg/L limit
Result: Meets limit
3.3 BIMS and eDMRs
Data submitted on Discharge Monitoring Report (DMR) forms are entered into the Divisions
BIMS database either by Division staff (paper DMRs) or by the permittee (electronic DMRs, or
'eDMRs').
Paper DMRs. Division staff enter daily monitoring results and statistical values as reported on
the form, up to 6 decimal places. Digits beyond 6 DPs are not entered. BIMS then recalculates all
statistical data from the daily values to 6 DPs and compares its own statistical data with permit
limits (if any) to determine compliance. BIMS identifies potential violations, and Division
compliance staff review these to identify which findings merit further attention.
eDMRs. Permittees submit daily data through the eDMR system. The system calculates and
displays statistical values in real time for the permittee's inspection. Daily values are currently
limited to 4 DPs, and statistical values extend to BIMS's standard 6 DPs. Once the data are
uploaded as an eDMR into BIMS, data storage and compliance determinations are handled the
same as with paper DMRs.
The Division is working on changes to the eDMR system and BIMS to ensure they handle
precision and rounding according to this guidance.
4. PRECISION IN ANNUAL MASS LOADS
Some dischargers in watersheds impacted by nutrients have seasonal or annual mass load limits
for Total Nitrogen or Total Phosphorus or both. This section describes modified conventions for
the calculation and reporting of annual mass loadings. The approach can also be adapted for
use with seasonal loadings and for loadings of other parameters.
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4.1 Setting Permit Limits (Mass)
The nutrient management strategies for the Neuse River estuary, Jordan Lake, and Falls Lake
each set annual mass limits for nitrogen and/or phosphorus for the existing, nutrient -bearing
dischargers. Limits can apply to groups of dischargers as well as to individual dischargers.
For permitting purposes, the Wasteload Allocations from nutrient TMDLs are treated as exact
values. WLAs are divided among the dischargers in proportion to their permitted flows, which
are based on Average Design Flow, also exact values. Thus, the individual nutrient allocations
and resulting limits for the affected dischargers are themselves exact values and not subject to
rounding.
In practice, the convention has evolved to calculate individual allocations without rounding and
to display the allocations and corresponding limits to the nearest 1 lb/yr for brevity's sake.
4.2 Reporting Monitoring Results (Mass)
Current permits prescribe how nutrient loads are to be calculated; see Appendix C for more
detail. Permittees must calculate and report monthly mass loads with each DMR and then
report the sum of those monthly loads at the end of the calendar year.
Monitoring results for flow and nutrients are approximate values, so the mass loads calculated
from them should be rounded to reflect the proper precision.
However, monthly loads are intermediate results in the calculation of annual loads and,
according to the conventions in Section 2, should not be rounded: only the annual loads need
be rounded for compliance purposes. In the case of compliance groups or 'bubble' permit limits,
only the collective annual loads of the multiple facilities need be rounded.
Reporting the unrounded monthly loads would also be cumbersome (12,345.6789...) and of
little real value. Also, additional rounding at each step in the calculations could cause errors in
the annual loads, especially significant for dischargers with smaller loads. To avoid these
pitfalls, permittees can report all significant digits plus one non -significant digit in their
monthly loads, then round the annual load for compliance purposes.
An alternate approach would be to report monthly loads to the nearest 1 lb/mo (or greater
increments for larger facilities) and, again, round only the final loads. The monthly values
would include extra non -significant digits, but this approach is easier to implement where
spreadsheets (or similar software) are used. The key would then be for the permittee to properly
round its annual load for entry on its DMR.
Depending on the facility, annual loads will commonly be rounded to as low as the nearest 1
pound or as high as the nearest 10,000 pounds or more. Thus, loads reported by most facilities
will have fewer significant figures than the corresponding limit. (They will appear less precise
than the limit but, because the limit is an exact value, measures of precision do not apply to it.)
4.3 Determining Compliance (Mass)
Compliance is determined by comparing the calculated annual load (rounded annual value)
with the corresponding annual limit (exact value). This is a direct comparison of the two values,
with no further rounding of either value beforehand. An actual load that is less than or equal to
the permit limit indicates compliance with that limit.
Appendix C provides examples of annual nutrient load calculations for individual dischargers
and for groups of dischargers that report their collective loads.

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U1aaIlillU1ff»
COMMON SIGNIFICANT FIGURES AND REPORTING CONVENTIONS
FOR CONVENTIONAL AND TOXIC PARAMETERS
Typical Range of
Commonly Used
Significant
Precision Typically
Parameters
Permit Limits `
Approved Methods
Figures
Reported on DMRs:
Assorted flow
Achievable accuracy of the
Flow
Vary widely
measurement devices
2 3
measurement device used
BOD
5.0 to 50 mg/L
DO Probe
2 SF
If <10: 0.1 mg/L
If >10: whole numbers
CBOD
2.0 to 45 mg/L
DO Probe
2 SF
If <10: 0.1 mg/L
If >10: whole numbers
NH3-N
0.5 to 30.0 mg/L
Distill w/ ISE or
If <10: 2 SF
0.1 mg/L
Colorimetric
If > 10: 3 SF
TSS
5.0 to 80.0 mg/L
Filtration/Gravimetric
<10: 2
0.1 mg/L
>10: 3
Temperature
90-102 °F (steam electric)
Various
Various
Whole numbers*
200/400 fecal in domestic
<10: 1
Bacteria
effluent, 5/14 fecal in reuse
Various
>10 to <100: 2
Whole numbers*
(Fecal, E. Coli, etc.)
waters, 35/276 for Enterococci
>100: 3
Dissolved Oxygen
5.0 to 10.0 mg/L
DO Probe
10: 2
<<10:
0.1 mg/L
3
Total Chlorine
Residual (method
17-28 µg/Lfreshwater,
Amperometric Titration,
>13 to <100: 1
10 µg/L
13 µg/L saltwater
DPD Colorimetric
>100: 2
dependent)
—
pH
6.0 to 9.0 standard units
pH Probe
<10: 2>10:
0.1 S.U.
3
Metals
Vary widely
2-3
Varies
Nutrients
Total Nitrogen (TN)
Vary widely
Sum of TKN
Depends on
Depends on results from
and NO3-N + NO2-N
other analyses
other analyses
TKN
<2.0 - 20 mg/L to meet
Digest w/ ISE or
<10: 2
0.1 mg/L
typical TN mass limits
Colorimetric
>10: 3
Nitrate and Nitrite
<1.0 - 20 mg/L to meet
Colorimetric or IC
<10: 2
0.1 mg/L
typical TN mass limits
>10: 3
<0.1: 1
If <O.1: 0.01 mg/L
Total Phosphorus
O.S to 2.0 mg/L
Colorimetric
20.1 to <10: 2
I f> 0.1: 0.1 mg/L
>10: 3
* Integer values (0 DPs): 23 mg/L, 687, 34 CFM, etc.
3 The Division does not require reporting of specific numbers of significant figures at this time. The values in this
appendix are intended merely to illustrate commonly reported results.

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APPENDIX B:
SAMPLE CALCULATIONS
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APPENDIX C:
SAMPLE CALCULATIONS — NUTRIENTS
Some nutrient TMDLs and strategies establish annual mass limits for nitrogen or phosphorus or
both. Establishing nutrient limits for the affected dischargers (individually or in groups),
reporting effluent nutrient loads, and determining compliance with the limits requires special
attention and some minor exceptions to the standard conventions described in this document.
Examples —Annual Mass Nutrient Limits
Examples — Reporting of Nutrient Mass Loads
Permits for affected facilities typically prescribe the following methodology for calculating
nutrient loads:
CALCULATION OF TOTAL NITROGEN AND TOTAL PHOSPHORUS LOADS
(a.) The Permittee shall calculate monthly and amlual TN Loads as follows:
(i.) Monthly TN (or TP) Load (lb/mo) = TN (or TP) x TMF x 8.34
where:
TN or TP = the average Total Nitrogen or Total Phosphorus concentration
(mg/L) of the composite samples collected during the month
TMF = the Total Monthly Flow of wastewater discharged during the
month (MG/mo)
8.34 = conversion factor, from (mg/L x MG) to pounds
(ii.) Annual TN (or TP) Load (lb/yr) = Sum of the 12 Monthly TN (or TP) Loads for the
calendar year
(b.) The Permittee shall report monthly Total Nitrogen and Total Phosphorus results (mg/L and
lb/mo) in the appropriate discharge monitoring report for each month and shall report each
calendar year's results (lb/yr) with the December report for that year.
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In short, permittees calculate monthly loads for each nutrient from daily flows and nutrient
concentration values. They then sum the monthly loads at the end of each calendar year to
calculate the annual loads.
The following examples illustrate how annual TN loads are calculated and reported to satisfy
this condition. The same approach is used to calculate TP loads and can be adapted to calculate
seasonal or other mass loads.
The discharger begins by determining its average TN and total flow for the month.
These Total Monthly Flow and Monthly Average TN concentrations values are used to calculate
the monthly mass load.
Monthly Mass Load —Total Nitrogen
Calculate the monthly TN Load for January for the same facility.
TN Load (lb/mo) = TN Conc. (mg/L) * TMF (MG/mo) * 8.34
8.54 *, 63.514 * 8.34 = 4,523.69573 ­4 4,520 Ib/mo TN (retaining 1 non -SF)
OR 4,523 Ib/mo TN (truncate to nearest pound)
The precisions of the concentration values and the flow values are two significant figures and three decimal places,`;
respectively. The precision of the TN measurements is more limiting in this case. There is no monthly limit, so the facility
can record the monthly load with extra digits: either with one extra (non -significant) digit (4,520 lb/mo) or truncated to
the nearest pound,(4,523 Ib/mo).
The precision of this monthly load is precise to the nearest 100 Ib/mo. Assuming that other monthly values are similar,
the annual load (as the sum of these values)will also be precise to the nearest 100 Ib/mo and will be rounded
accordingly.
Note: If all TN samples were precise to 2 DPs, this monthly load would have been precise to the nearest 10 Ib/mo.
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Monthly loads are calculated and reported in the facility's DMRs as the year progresses. At the
end of the year, the permittee calculates its total load for the calendar year and reports the result
on its December DMR.
In the case of a group compliance association, the combined annual nutrient loads of all the
individual members is calculated and reported to the Division on an annual basis.
13