NC0004308_Email_20210429

6/25/2021 Mail - Denard, Derek - Outlook
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RE: [External] FOIA Request
Chandra Taylor <[e-mail]>
Thu 4/29/2021 5:21 PM
To: Denard, Derek <[e-mail]>; Cody, Karen <[e-mail]>; Hannah Petersen
<[e-mail]>
Cc: Gurney, Anna <[e-mail]>; Hennessy, John <[e-mail]>
CAUTION: External email. Do not click links or open aachments unless you verify. Send all suspicious email as an aachment
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Thank you very much Derek.

From: Denard, Derek <[e-mail]>
Sent: Thursday, April 29, 2021 11:17 AM
To: Cody, Karen <[e-mail]>; Hannah Petersen <[e-mail]>; Chandra Taylor
<[e-mail]>
Cc: Gurney, Anna <[e-mail]>; Hennessy, John <[e-mail]>
Subject: Re: [External] FOIA Request

Aached is everything we could find on discussion of cyanide between EPA and NCDEQ. This includes
emails and memos.

If you have any quesons, please contact our PIO, Anna Gurney.

Sincerely,

Derek Denard
Environmental Specialist
N.C. Division of Water Resources
N.C. Department of Environmental Quality

919 707 3618 office
919 707 9000 main DWR
[e-mail]

1617 Mail Service Center
Raleigh, NC 27699-1617

Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.

From: Cody, Karen <[e-mail]>
Sent: Monday, March 29, 2021 10:17 AM
6/25/2021 Mail - Denard, Derek - Outlook
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To: Denard, Derek <[e-mail]>; Hill, David A <[e-mail]>
Subject: [External] FOIA Request

CAUTION: External email. Do not click links or open aachments unless you verify. Send all suspicious email as an
aachment to Report Spam.

All:
This email is regarding the aached FOIA request EPA Region 4 received from SELC/Hannah Petersen. The request
is pertaining to an agreement between EPA and NCDEQ relang to the enforcement limit for cyanide. Ms.
Petersen informed me that you both were contacts pertaining to this request. Please review the FOIA request and
inform of any agreement. Thank you for your assistance.

Karen Cody
Government Information Specialist
EPA Region 4
404-562-9167
[e-mail]

Analytical Issues Surrounding Trace Elements:
Cyanide, Mercury, & Cadmium
B. Bolt
09/15/98
1
Growing concerns about unexplained cadmium, mercury, and cyanide violations at municipal
wastewater treatment plants have been directing attention to the possible causes. Not only have
the precision and accuracy of EPA methods used to measure these substances come under
scrutiny, but quality control in sampling and laboratory procedures have also been investigated.
Cyanide in particular has come to the forefront as a national issue. Research has suggested that
not only might cyanide violations result from lack of quality control in analytical procedures, but
also from the analytical methods themselves and/or possibly even from particular treatment steps.
Combining information from the 1997 Pretreatment Workshop and a seminar given by Dr.
Howard Weinberg of UNC-Ch on 12/1/97, the following information summarizes some of the
issues and on-going research surrounding these substances.
Cyanide Issues
The three main issues surrounding cyanide (CN) level determination are:
•inconsistencies in laboratory results
•influent measurements less than effluent measurements (i.e. an apparent "production" when
there should be none), and
•poor recoveries of CN in spiked influent and effluent samples.
The current EPA standard method (SM) is somewhat archaic; it is basically an acid distillation
into a basic solution, converting collected HCN into CNCl-, followed by complexation with
pyridine-barbituric acid and analysis. This method can only process one sample at a time, at a
rate of about 3 hours per sample!
At the Pretreatment Workshop, William Kreutzberger (CH2M Hill) discussed a study that
used the Method of Standard Additions to investigate presence of CN in both the influent and
effluent of POTWs, evaluate the efficacy of the method, evaluate variability, and determine a
"quantitation" level for compliance purposes.
Highlights from Kreutzberger's presentation:
•Water Quality Standard is 5.0 µg/l (based on chronic criterion) and 22 µg/l, a daily max.
based on acute criterion.
• Spikes < 15 µg/l were not measurable in influent; apparent interference from 5 to 50 µg/l.
•Highly variable effluent results in 5 to 15 µg/l range
• Apparent quantitation level is 15 to 25 µg/l. Study indicates inability to trace sources with
this method and shows significant masking of CN in 5 to 50 µg/l range.
Dr. Weinberg's seminar ("Assessment of Trace Element Concentrations in Municipal
Wastewater Treatment Plant Discharges in North Carolina") discussed a study which
investigated a group of municipalities experiencing periodic violations of CN, Mercury (Hg), and
Cadmium (Cd). (The cities of High Point, Winston-Salem, Burlington, Durham, and Charlotte
were among the participants.)
The concentrations of these pollutants appeared to increase inside the plant, which was unusual,
given that it seemed unlikely the substances would be formed during treatment. (As a side note,
though, Weinberg admitted the researchers are no longer "as arrogant about that.") Major peaks
happened once or twice a year and did not seem to be correlated with anything.
These erratic analytical results led investigators to:
•Review each facility's history of compliance
Analytical Issues Surrounding Trace Elements:
Cyanide, Mercury, & Cadmium
B. Bolt
09/15/98
2
•Ascertain current procedures used for sample collection, handling, and analysis of Cd, CN,
and Hg.
•Develop workable protocol
•Test protocol on participating utilities
•Liase with EMSL and DEM for approval of protocol
Sources of CN include: water treatment sludge, cyanogenic bacteria, and metal plating industries.
Simple cyanides are generated in the following types of reactions:
H2O
A(CN)x Ax+ + xCN-

CN- + H3O+ HCN + H2O
Complex cyanides take the form:
AyM(CN)x e.g. K3Fe(CN)6
[Zn(CN)4]2-
where A represents an element with a positive valence number, and x and y are
stoichiometric factors.
Analytical errors:
•Sample not always dechlorinated.
• Uncertainty about preservation of samples
•Not all interference accounted for
• QA inadequate
•Extreme variability at < 10 µg/l
•Calibration curve does not take into account added preservatives or the complex make-up of
the wastestream (the calibration is based on deionized water.)
• Known inadequacies of the distillation technique (EPA SM)
The investigators tested out a technique called Flow Injection Analysis (FIA), which can measure
down to 3 µg/l. Ultimately, this technique uses a UV light to detect CN. A flow diagram below
shows the design of the FIA:
an acid, base, and carrier gas are fed into a "black box," where the diffused gas goes through the
process of UV digestion, and a detector senses the presence of CN. The drawback to this
Analytical Issues Surrounding Trace Elements:
Cyanide, Mercury, & Cadmium
B. Bolt
09/15/98
3
technique is that the FIA also measures sulfides, and sodium sulfite, sodium thiosulfite, and
sodium metabisulfite are among compounds normally used to dechlorinate a waste stream. Since
the detector only senses gases, however, the only sulfide compound would have to be hydrogen
sulfide, which can be precipitated out at low pHs.
Role of Chlorine:
What about this mysterious "production" of CN at these plants—is it only due to the analytical
methods or is there something else involved? When pre- and post-chlorination samples were
compared, post-chlorination levels of CN were higher when measured with several different
methods. Researchers also noticed that CN problems at facilities that changed from chlorination
to UV disinfection disappeared "overnight." This observation led to a more careful look at
chlorine chemistry:
NaCN + Cl2 CNCl + NaCl
NaOH
CNCl CNO
Cl2 H+
CNO CO2 + N2 or CNO NH4
Hypothetical reactions that may be responsible for CN production are many. Ascorbic acid
(commonly known as vitamin C), for instance, can react with NO2 to form CN. Waters that have
not been sufficiently denitrified could allow this reaction to take place.
During chlorination:
Chlorine + nitrogenous organics NO2 + NO3
NO2 + ascorbic acid
sugars
starch CN
cellulose
alcohols
Chlorine + amino acids
polypeptides N-chloroamines HCN
During Digestion:
NO2 + H+ + ketones oximes cyanohydrin
Possible Interferences:
Thiocyanates:
2NO3- + SCN-CN- + SO42- + 2NO
Cyanohydrins [e.g. R2C(OH)CN]: can decompose during distillation.
Cyanide removal:
Analytical Issues Surrounding Trace Elements:
Cyanide, Mercury, & Cadmium
B. Bolt
09/15/98
4
SO2 + CN- + H2O CNO- + H2SO4
CNO- + H+ (NH4)2CO3
Conclusions so far from the team's research are:
• EPA SM and FIA methods comparable
•Recoveries can range between 0-500%
• Chlorination produces the highest apparent levels. Not present in pre-chlorinated water.
•Interferences: Both FIA and SM respond to CNCl and sulfide.
Mercury Issues
Highlights from Jeff Poupart's (Division of Pollution Prevention and Environmental Assistance) presentation at the Pretreatment Workshop:
• Most contamination comes from air pollution, not water discharges
•Dental/Medical office discharges suspected as major mercury (Hg) source
•Water Quality Standard is 0.012 µg/l, which is 17 times lower than detection
•Toxic characteristic level 0.2 mg/l (It is actually the methyl mercury which is bioaccumulated
and is extremely toxic to organisms)
• Safe drinking water level 2 µg/l
• North Carolina is forming a workgroup of DENR Divisions to coordinate efforts and
determine action options
•A recent study from Massachusetts, which concentrated on medical facilities, showed that
mercury can be absorbed in biomass inside of pipes and bioaccumulate and then sloughs off,
causing Hg spikes. Numerous cities in NC have intermittent Hg slugs.
Figures 1 & 2
•Strategies for reduction included: Pressure Washing; Trap Cleaning/Replacement (Costly if
collected waste is hazardous); Finding out which Industrial Users (IU) discharge Hg (though
treatment difficult on IU level); Test Slime.
Dr. Weinberg did not spend a whole lot of time on mercury when presenting the results of the
study in which he was involved. He did mention that the lower the amount spiked into samples
by the researchers (which were split and sent off to commercial, on-site, and the state's
laboratories), the worse the reported % recoveries of Hg.
Analytical Issues Surrounding Trace Elements:
Cyanide, Mercury, & Cadmium
B. Bolt
09/15/98
5
Cadmium Issues
Info. presented by Dr. Weinberg was brief:
Methods (in order of decreasing sensitivity):
• Graphite furnace AA (atomic absorption) with Zeeman background
• " " with Deuterium background
•Flame AA with aqueous concentration
Sources of Error:
• Poor acid purity
•Variable lab grade water
• Shipped samples not preserved
• Inadequate calibration curves
• Recoveries not determined in matrix (i.e. distilled water vs. wastewater)
• Recoveries in lab grade water at ppm levels.
QA Failures:
The lower the spikes done by researchers, the worse the recoveries (same as CN).
Overall Conclusions from Weinberg's Presentation:
• QA/QC procedures now in place at Durham, Raleigh, Charlotte
• Cd, Hg: 90-110% recovery in above labs. State and other utility labs 0-200%...on same
sample!
•Commercial labs: few responses to questionnaires, some incomplete
NCDENR/DIVISION OF WATER QUALITY
Water Quality Section/Point Source Branch
December 21, 1998
MEMORANDUM
To: NPDES Unit
Through: Dave Goodrich
From: Bethany Bolt
Subject: Cyanide Limits and Metals Monitoring
Various approaches to toxicant monitoring and limits have prevailed in NPDES permits in the past, resulting in inconsistencies
statewide. In addition, controversies surrounding analytical methods for parameters like cyanide (CN) and mercury have
complicated implementation of limits for some facilities. This memo describes our current approach to implementing toxicant
monitoring and limits, including specifically CN.
Upon renewal, a permit writer determines whether or not a limit is necessary based on reasonable potential analysis. Monitoring
should then be given in accordance with the table below 1:
Toxicant Limits? Class I & II Class III & IV
No—Monitoring only Monthly 2/Month
Yes—Limit 2/Month Weekly
Monitoring should also be specified to occur in conjunction with any Whole Effluent Toxicity (WET) monitoring at the facility, so that data may be compared
with future WET test results.
In light of information available regarding cyanide measurement techniques, the Division feels it is reasonable to specify the total
cyanide quantitation limit as 10 µg/l (10 ppb). This information should be footnoted on the effluent page(s).
A daily maximum limit for CN, based on the water quality standard of 5.0 µg/l, should be given if reasonable potential exists to
exceed this level. Because North Carolina has adopted standards based on chronic criteria, DWQ imposes a daily maximum limit to
protect against both chronic and acute effects (a daily maximum reflects acute criteria, and a weekly average reflects chronic). Some
municipalities experience periodic violations of the daily maximum limit, however, and request that their limit be moved to a weekly
average—a value more reflective of the chronic basis. DWQ has agreed to modify CN limits for these facilities upon request by
including a new daily maximum limit of 22 µg/l with the appropriate weekly average (the “old” daily maximum, based on the
standard). 22 µg/l is one half the final acute value (½ FAV) established by EPA 2.
The process is the same (upon request) with other metals limits—except for mercury (Hg). Because this element readily converts to
the extremely bioaccumulative methyl-mercury form, the ½ FAV for Hg of 2.4 µg/l has not been deemed an acceptable daily
maximum limit by DWQ at this time.
1 Some exceptions are made (e.g., if a municipality is monitoring for a toxicant at the discharge as part of its Long Term Monitoring Plan
(LTMP) just as frequently)
2 From December 5, 1993 Memo to Instream Assessment Unit from Dave Goodrich
Some older permits may not be consistent with this practice. Previously, the ½ FAV was compared to four times the weekly average,
and the more stringent of the two was chosen as the daily maximum. This method was developed to prevent a facility from violating
both limits with one measurement, but DWQ is no longer utilizing this method (the rationale being that a violation of both limits is no
more reprehensible than a violation of one limit with just one data point.) The ½ FAV is given directly, without taking into account
dilution, because the undiluted material (appropriately) must meet acute criteria.
NCDENR/DIVISION OF WATER QUALITY
Water Quality Section/Point Source Branch
April 28, 1999
MEMORANDUM
To: NPDES Unit, Pretreatment Unit, Point Source Compliance and Enforcement Unit, Regional
Offices
Through: Dave Goodrich
From: Bethany Bolt
Subject: Limits and Monitoring for Cyanide and Metals
Various approaches to toxicant monitoring and limits have prevailed in NPDES permits in the past, resulting in inconsistencies
statewide. In addition, controversies surrounding analytical methods for parameters like cyanide (CN) and mercury (Hg) have
complicated compliance determinations for some facilities. This memo describes and clarifies our current approach to
implementing chemical specific toxicant monitoring and limits, including CN.
Determining Need for Limits and Monitoring Frequencies
Upon renewal, a permit writer determines whether or not a limit is necessary based on reasonable potential analysis (see
Attachment A). The 7Q10 (summer) flow is used for calculating allowable concentrations of toxicants with aquatic life standards
and human health standards that are non-carcinogenic (e.g., CN); the average flow (Q) is used for carcinogens (e.g., benzene); and
30Q2 flow is used when applying aesthetic standards (e.g., phenolic compounds). Monitoring should then be given in accordance
with the table below:
Does Reasonable Potential Exist? WWTP Classes I & II WWTP Classes III & IV
No—Monitoring only Monthly 2/Month
Yes—Limit 2/Month Weekly
Monitoring should also be specified to occur in conjunction with any Whole Effluent Toxicity (WET) monitoring at the
facility, so that future data may be compared with WET test results.
Exceptions to Monitoring Frequencies:
•Unless a limit applies, a municipality that already monitors for a particular toxicant as part of its Long Term Monitoring Plan
(LTMP) does not need to monitor the parameter as part of the permit.
•If the past twelve (12) months of data indicate levels are below quantitation or detection limits (especially for industries),
monitoring may be reduced to quarterly.
Quantitation Levels
The lowest quantifiable level of a chemical in a sample is the “quantitation level.” Depending upon the sensitivity of the analytical
instrument and techniques used, various quantitation levels apply for different parameters. In light of information available regarding
cyanide measurement techniques, the Division feels it is reasonable to specify the total CN quantitation level (QL) as 10 µg/l (10
4/28/99 Memorandum, p. 2 of 3
Limits and Monitoring for CN and Metals

ppb). This information should be footnoted on the effluent page(s). Cyanide values reported as <10 µg/l should be considered
compliant with the permit limit.

Exceptions to Quantitation Levels:
Towns such as Winston-Salem have conducted studies to demonstrate to the Division that a quantitation level other than 10 µg/l
should apply. Winston-Salem invested significant effort into conducting a thorough, site-specific study in order to determine a QL
suitable for its own wastewater.

The Division is also now specifying the total mercury QL as 0.2 µg/l (also footnoted on the effluent page). It is worthy to note that
EPA has proposed a new method for analyzing mercury (Method 1631), which has a quantitation level (referred to by EPA as
Minimum Level, or ML) of 0.0005 µg/l (0.5 ng/l). However, the Division’s laboratory feels this method poses quantitation problems
in complex wastewaters and has not yet accepted Method 1631 as appropriate for effluent monitoring in North Carolina (only
accepted for drinking water analysis).

For reference, the following ranges of quantitation levels (referred to by our lab as “Practical Quantitation Levels,” or PQLs) are
achievable for these commonly monitored metals: Cadmium (Cd)—1-10 µg/l, Chromium (Cr)—5-100 µg/l, Copper (Cu)—2-20 µg/l,
Nickel (Ni)—5-100 µg/l, Lead (Pb)—5-100 µg/l, and Zinc (Zn)—10-2000 µg/l. The NPDES permit only requires that the test
procedure produce data below the permitted limit, if possible; therefore, laboratory QLs may vary with the facility’s calculated limit.

Compliance Periods: Daily Maximum and Weekly Average Limits
In the past, a daily maximum limit for a toxicant was the only limit placed in the permit. This limit was based on the water quality
standard. Because North Carolina adopted standards based on chronic criteria, the Division imposed a daily maximum limit to protect
against both chronic and acute effects (a daily maximum reflects acute criteria, and a weekly average reflects chronic). Some treatment
plants experience periodic violations of this daily maximum limit, however, and have requested that their limit be moved to a weekly
average—a value more reflective of the chronic basis. The Division has agreed to modify toxicant limits for these facilities by
including a new daily maximum limit equal to one half of the Final Acute Value (½ FAV) established by EPA 1. The ½ FAV is given
directly, without taking into account dilution, because the undiluted pollutant must meet acute criteria (i.e., the daily maximum limit
must protect for an acute exposure of aquatic life to the effluent as it initially enters surface waters).

The process is different for mercury, however. Because this element readily converts to the extremely bioaccumulative methyl-
mercury form, the Division has not deemed the ½ FAV for Hg (2.4 µg/l) an acceptable daily maximum limit at this time. To solidify
its policy on applying limits for metals, the Division will now consistently apply daily maximum and weekly average limits for
CN and metals (except Hg) for all facilities with reasonable potential to exceed allowable concentrations. Daily maximum
limits shall be the ½ FAV, and weekly average limits shall be based on the water quality standard and dilution at the appropriate flow
conditions (see mass balance in Attachment A).

1 From December 5, 1993 Memo to Instream Assessment Unit from Dave Goodrich (Attachment C).
4/28/99 Memorandum, p. 3 of 3
Limits and Monitoring for CN and Metals

Some older permits may not be consistent with this practice. Previously, the diluted ½ FAV was compared to four times the weekly
average, and the permit writer chose the more stringent of the two as the daily maximum. The method was developed to prevent a
facility from violating both limits with one measurement, but the Division no longer applies this policy (the rationale being that a
violation of both limits is no more reprehensible than a violation of one limit with just one data point.)

Exceptions to Limits:
If the ½ FAV is more stringent than the weekly average limit, then only the daily maximum limit is needed. For example, the ½ FAV
for lead is 33.8 µg/l. If the weekly average limit based on the water quality standard (25 µg/l) were 40 µg/l, only the daily maximum
limit would be necessary for lead.

Also, when dilution modeling is performed (such as with FORTRON or Takeda), the daily maximum and/or weekly average limit may
be replaced by a value determined by the model.

Hopefully this clarifies the Division’s current policy for applying metals and CN limits, as well as explains most circumstances in which
exceptions are made. It is our aim to more accurately represent the criteria of the standards and to specify reasonable quantitation
levels for some parameters.

Cc: Coleen Sullins, DWQ
Caroline Ejimifor, U.S. EPA

NCDENR/DIVISION OF WATER QUALITY
Water Quality Section/Point Source Branch
December 21, 1998
MEMORANDUM
To: NPDES Unit
Through: Dave Goodrich
From: Bethany Bolt
Subject: Cyanide Limits and Metals Monitoring
Various approaches to toxicant monitoring and limits have prevailed in NPDES permits in the past, resulting in inconsistencies
statewide. In addition, controversies surrounding analytical methods for parameters like cyanide (CN) and mercury have
complicated implementation of limits for some facilities. This memo describes our current approach to implementing toxicant
monitoring and limits, including specifically CN.
Upon renewal, a permit writer determines whether or not a limit is necessary based on reasonable potential analysis. Monitoring
should then be given in accordance with the table below 1:
Toxicant Limits? Class I & II Class III & IV
No—Monitoring only Monthly 2/Month
Yes—Limit 2/Month Weekly
Monitoring should also be specified to occur in conjunction with any Whole Effluent Toxicity (WET) monitoring at the facility, so that data may be compared
with future WET test results.
In light of information available regarding cyanide measurement techniques, the Division feels it is reasonable to specify the total
cyanide quantitation limit as 10 µg/l (10 ppb). This information should be footnoted on the effluent page(s).
A daily maximum limit for CN, based on the water quality standard of 5.0 µg/l, should be given if reasonable potential exists to
exceed this level. Because North Carolina has adopted standards based on chronic criteria, DWQ imposes a daily maximum limit to
protect against both chronic and acute effects (a daily maximum reflects acute criteria, and a weekly average reflects chronic). Some
municipalities experience periodic violations of the daily maximum limit, however, and request that their limit be moved to a weekly
average—a value more reflective of the chronic basis. DWQ has agreed to modify CN limits for these facilities upon request by
including a new daily maximum limit of 22 µg/l with the appropriate weekly average (the “old” daily maximum, based on the
standard). 22 µg/l is one half the final acute value (½ FAV) established by EPA 2.
The process is the same (upon request) with other metals limits—except for mercury (Hg). Because this element readily converts to
the extremely bioaccumulative methyl-mercury form, the ½ FAV for Hg of 2.4 µg/l has not been deemed an acceptable daily
maximum limit by DWQ at this time.
1 Some exceptions are made (e.g., if a municipality is monitoring for a toxicant at the discharge as part of its Long Term Monitoring Plan
(LTMP) just as frequently)
2 From December 5, 1993 Memo to Instream Assessment Unit from Dave Goodrich
Some older permits may not be consistent with this practice. Previously, the ½ FAV was compared to four times the weekly average,
and the more stringent of the two was chosen as the daily maximum. This method was developed to prevent a facility from violating
both limits with one measurement, but DWQ is no longer utilizing this method (the rationale being that a violation of both limits is no
more reprehensible than a violation of one limit with just one data point.) The ½ FAV is given directly, without taking into account
dilution, because the undiluted material (appropriately) must meet acute criteria.
NCDENR/DIVISION OF WATER QUALITY
Water Quality Section/Point Source Branch

April 28, 1999

MEMORANDUM

To: NPDES Unit, Pretreatment Unit, Point Source Compliance and Enforcement Unit, Regional
Offices
Through: Dave Goodrich
From: Bethany Bolt

Subject: Limits and Monitoring for Cyanide and Metals

Various approaches to toxicant monitoring and limits have prevailed in NPDES permits in the past, resulting in inconsistencies
statewide. In addition, controversies surrounding analytical methods for parameters like cyanide (CN) and mercury (Hg) have
complicated compliance determinations for some facilities. This memo describes and clarifies our current approach to
implementing chemical specific toxicant monitoring and limits, including CN.

Determining Need for Limits and Monitoring Frequencies
Upon renewal, a permit writer determines whether or not a limit is necessary based on reasonable potential analysis (see Attachment
A). The 7Q10 (summer) flow is used for calculating allowable concentrations of toxicants with aquatic life standards and human
health standards that are non-carcinogenic (e.g., CN); the average flow (Q) is used for carcinogens (e.g., benzene); and 30Q2 flow
is used when applying aesthetic standards (e.g., phenolic compounds). Monitoring should then be given in accordance with the
table below:

Does Reasonable Potential Exist? WWTP Classes I & II WWTP Classes III & IV
No—Monitoring only Monthly 2/Month
Yes—Limit 2/Month Weekly

Monitoring should also be specified to occur in conjunction with any Whole Effluent Toxicity (WET) monitoring at the
facility, so that future data may be compared with WET test results.

Exceptions to Monitoring Frequencies:
• Unless a limit applies, a municipality that already monitors for a particular toxicant as part of its Long Term Monitoring Plan (LTMP)
does not need to monitor the parameter as part of the permit.
• If the past twelve (12) months of data indicate levels are below quantitation or detection limits (especially for industries), monitoring
may be reduced to quarterly.

Quantitation Levels
The lowest quantifiable level of a chemical in a sample is the “quantitation level.” Depending upon the sensitivity of the analytical
instrument and techniques used, various quantitation levels apply for different parameters. In light of information available regarding
cyanide measurement techniques, the Division feels it is reasonable to specify the total CN quantitation level (QL) as 10 µg/l (10
4/28/99 Memorandum, p. 2 of 3
Limits and Monitoring for CN and Metals

ppb). This information should be footnoted on the effluent page(s). Cyanide values reported as <10 µg/l should be considered
compliant with the permit limit.

Exceptions to Quantitation Levels:
Towns such as Winston-Salem have conducted studies to demonstrate to the Division that a quantitation level other than 10 µg/l should
apply. Winston-Salem invested significant effort into conducting a thorough, site-specific study in order to determine a QL suitable
for its own wastewater.

The Division is also now specifying the total mercury QL as 0.2 µg/l (also footnoted on the effluent page). It is worthy to note that
EPA has proposed a new method for analyzing mercury (Method 1631), which has a quantitation level (referred to by EPA as Minimum
Level, or ML) of 0.0005 µg/l (0.5 ng/l). However, the Division’s laboratory feels this method poses quantitation problems in complex
wastewaters and has not yet accepted Method 1631 as appropriate for effluent monitoring in North Carolina (only accepted for drinking
water analysis).

For reference, the following ranges of quantitation levels (referred to by our lab as “Practical Quantitation Levels,” or PQLs) are
achievable for these commonly monitored metals: Cadmium (Cd)—1-10 µg/l, Chromium (Cr)—5-100 µg/l, Copper (Cu)—2-20 µg/l,
Nickel (Ni)—5-100 µg/l, Lead (Pb)—5-100 µg/l, and Zinc (Zn)—10-2000 µg/l. The NPDES permit only requires that the test procedure
produce data below the permitted limit, if possible; therefore, laboratory QLs may vary with the facility’s calculated limit.

Compliance Periods: Daily Maximum and Weekly Average Limits
In the past, a daily maximum limit for a toxicant was the only limit placed in the permit. This limit was based on the water quality
standard. Because North Carolina adopted standards based on chronic criteria, the Division imposed a daily maximum limit to protect
against both chronic and acute effects (a daily maximum reflects acute criteria, and a weekly average reflects chronic). Some treatment plants
experience periodic violations of this daily maximum limit, however, and have requested that their limit be moved to a weekly average—
a value more reflective of the chronic basis. The Division has agreed to modify toxicant limits for these facilities by including a new
daily maximum limit equal to one half of the Final Acute Value (½ FAV) established by EPA 1. The ½ FAV is given directly, without
taking into account dilution, because the undiluted pollutant must meet acute criteria (i.e., the daily maximum limit must protect for an
acute exposure of aquatic life to the effluent as it initially enters surface waters).

The process is different for mercury, however. Because this element readily converts to the extremely bioaccumulative methyl-mercury
form, the Division has not deemed the ½ FAV for Hg (2.4 µg/l) an acceptable daily maximum limit at this time. To solidify its policy
on applying limits for metals, the Division will now consistently apply daily maximum and weekly average limits for CN and
metals (except Hg) for all facilities with reasonable potential to exceed allowable concentrations. Daily maximum limits shall
be the ½ FAV, and weekly average limits shall be based on the water quality standard and dilution at the appropriate flow conditions
(see mass balance in Attachment A).

1 From December 5, 1993 Memo to Instream Assessment Unit from Dave Goodrich (Attachment C).
4/28/99 Memorandum, p. 3 of 3
Limits and Monitoring for CN and Metals

Some older permits may not be consistent with this practice. Previously, the diluted ½ FAV was compared to four times the weekly
average, and the permit writer chose the more stringent of the two as the daily maximum. The method was developed to prevent a
facility from violating both limits with one measurement, but the Division no longer applies this policy (the rationale being that a violation
of both limits is no more reprehensible than a violation of one limit with just one data point.)

Exceptions to Limits:
If the ½ FAV is more stringent than the weekly average limit, then only the daily maximum limit is needed. For example, the ½ FAV
for lead is 33.8 µg/l. If the weekly average limit based on the water quality standard (25 µg/l) were 40 µg/l, only the daily maximum
limit would be necessary for lead.

Also, when dilution modeling is performed (such as with FORTRON or Takeda), the daily maximum and/or weekly average limit may
be replaced by a value determined by the model.

Hopefully this clarifies the Division’s current policy for applying metals and CN limits, as well as explains most circumstances in which
exceptions are made. It is our aim to more accurately represent the criteria of the standards and to specify reasonable quantitation levels
for some parameters.

Cc: Coleen Sullins, DWQ
Caroline Ejimifor, U.S. EPA

4/29/2021 Mail - Denard, Derek - Outlook
Re: Laboratory limits vs. Permit limits
Joe Corporon <[e-mail]>
Thu 5/23/2002 7:58 AM
To: Tom Belnick <[e-mail]>
Cc: DENR.NPDES.DWQ <[e-mail]>
j 1 attachments (24 KB)
A. (6) -- MOD FINAL.doc;
In our recent Settlement Agreement with Cabarrus County, Dave and I drafted language to define the
relationship between laboratory detection limits and permit limits using the EPA definitions (not PQL,
but ML and MDL). See attached file. Note the need to define compliance "at or below" the lab limit.
This is couched as a Special Condition, but I have also used a footnote version.
FYI. This is currently a draft candidate for the Guidence Manual.
Tom Belnick wrote:
fyi.. another one to sort out down the road. The DWQ lab used to report
a PQL of 5 ug/I for cyanide, and we interpreted anything <10 ug/I in
NPDES permits as zero for compliance purposes. During the last quarter
the DWQ lab changed their PQL to 20 ug/I. Might have to re-evaluate PQL
footnote, RPA, etc.
Mailto:[e-mail]
N.0 DENR-DWQ/NPDES Unit
1617 Mail Service Center, Raleigh NC 27699-1617
Work: [phone] ext. 543
Fax: [phone]
Subject: Re: PQLs for cyanide and fecal coliform
Date: Tue, 21 May 2002 11:04:30 -0400
From: Dana Satterwhite <[e-mail]>
Organization: NC DENR DWQ Chemistry Laboratory
To: Tom Belnick <[e-mail]>
References: <[e-mail]>
Yikes! Obviously a typo mistake when the tables were last updated. I'm glad
you said something. Our current PQL for Cyanide is 0.02 mg/L. The change was
made after reviewing and amending our Standard Operating Procedure and
conducting new MDL studies. 1 colony/100 ml is correct for fecal coliform
and both apply to wastewater as well as ambient water samples. Keep in mind
we report a "total cyanide" value. When the total cyanide value exceeds the
MCL, analysis of "free cyanide" should be performed to determine if there
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4/29/2021 Mail - Denard, Derek - Outlook
has been an MCL exceedence or to determine compliance with a water quality
standard.
Hope this helps. Thanks again for pointing out a very important mistake. I
will have our webmaster correct it immediately.
Dana
Tom Belnick wrote:
> Hi Dana- Here's an NPDES question. We just noticed that the 1st Quarter
> 2002 PQLs for cyanide and fecal coliform are 0.002 mg/I and 1
> colony/100m1, respectively. Are these values applicable for wastewater
> samples as well as ambient water samples? The PQL for cyanide was 0.005
> mg/I back on 7/24/01; is it only recently that the PQL has decreased.
> Thanks.
>
>
> Mailto:[e-mail]
> N.0 DENR-DWQ/NPDES Unit
> 1617 Mail Service Center, Raleigh NC 27699-1617
> Work: [phone] ext. 543
> Fax: [phone]
Dana Satterwhite <[e-mail]>
QA/QC Coordinator
NC DWQ CHEMISTRY LABORATORY
Department of Environment and Natural Resources
Dana Satterwhite
QA/QC Coordinator <[e-mail]>
NC DWQ CHEMISTRY LABORATORY
Department of Environment and Natural Resources
1623 Mail Service Center Fax: [phone]
Raleigh Work: [phone] ext. 243
NC
27699-1623
USA
Additional Information:
Last Name Satterwhite
First Name Dana
Version 2.1
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NPDES Permit No. NC0036269
SUPPLEMENT TO
EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS
SPECIAL CONDITIONS
A. (6.) CLARIFICATION OF COMPLIANCE WITH PERMIT LIMITS SET AT OR BELOW
MINIMUM LABORATORY PROCEDURE LEVELS
1. The following definitions apply to this permit [REF: EPA National Guidance for the Permitting, Monitoring and
Enforcement of Water Quality -Based Effluent Limitations Set below Analytical Detection/ Quantitation Levels
(DRAFT), March 22, 1994].
• The Method Detection Limit (MDL), as defined by a specific laboratory method, is the minimum
concentration that can be measured and reported with 99 percent confidence that the parameter is
greater than zero (i.e., the analyte is detectable or identifiable at this level, but not quantifiable).
• The Minimum Level (ML) is higher than the MDL, and is defined as the sample concentration
equivalent to the lowest detectable level ofthe calibration standard not requiring extrapolation,
i.e. the lowest quantifiable level, as defined by a specific analytical procedure.
2. In cases where the Division sets a parameter limit at the ML (as required to protect the receiving -stream
environment), the Division shall consider any report of that parameter at or below the ML to be in compliance.
• Example 1: If the ML is 10.0 µg/L and the permit limit is 10.0 µg/L, any report o f 10.0 µ g/L or
<10.0 µg/L shall be considered compliant with the permit.
3. In cases where the Division sets a parameter limit below the ML (as required to protect the receiving -stream
environment), the Division shall consider any report of that parameter below the ML to be in compliance.
• Example 2: If the ML is 10.0 µg/L and the permit limit is 2.0 µg/L, a report of 10µg/L sh a 11 no t
be compliant, but a report of <10.0 shall be considered compliant.
A. (7.) CLARIFICATION OF SAMPLE COLLECTING UNDER HAZARDOUS CONDITIONS
In accordance with North Carolina State Regulations 15A NCAC 2B.0505(c)(4), the permittee may discontinue
receiving -stream monitoring and sample collecting when flow conditions or extreme weather conditions could re sult
in injury or death ofthe person(s) collecting the samples. In such cases on the day of sampling, the permittee shall
record and justify the discontinuance, and furthermore, shall include this justification in th at month 's monitoring
report. This provision shall also apply to influent and effluent sampling.

4/29/2021 Mail - Denard, Derek - Outlook
comments on NC23256 - Carolina Beach
Hyatt.Marshall <[e-mail]>
Mon 6/3/2002 7:55 AM
To: teresa.rodriguez <[e-mail]>
Cc: Ejimofor.Caroline <[e-mail]>; mike.templeton <[e-mail]>
Caroline conducted an initial review and I completed it. Pls respond
when you can.
thanks Marshall
1) The fact sheet makes reference to a reasonable potential analysis,
however this was not included with this draft permit. Please transmit if
available.
2) The permit application reports values for the following pollutants as
"N/A": TKN, nitrate plus nitrite nitrogen, TDS, thallium, total
phenolic compounds, oil and grease, 1,3 dichloro-propylene, methyl
bromide, methylene chloride, p-chloro-m-cresol, 4,6 dinitro-o-cresol,
and fluoranthene. The permit application should not have been
considered complete. The draft permit does require that annual samples
that reflect seasonality be collected to rectify this deficiency.
However, it does not contain a reopener to include limits based on that
data, if needed. Will you add a specific reopener?
3)The NC Water Quality Standards list a cyanide criterion of 1.0 ug/I
and the application indicates the presence of cyanide in the effluent
above the NC WQS. The fact sheet does not justify the exclusion on a
cyanide limit in the draft permit. Pls explain why monitoring, rather
than limits, is required. Was an adequate mixing zone or credit for
dilution factored into this decision to exclude a cyanide limit?
Without a sufficient explanation, this would appear to not meet the
requirements of 40 CFR 122.44(d)(1)(iii) and would be a basis for an
objection to this permit.
4) Typically, metals are monitored as composites. Why are zinc and
copper listed as grabs?
5) Because the applicant did not complete Part E.2. on pages 15, 16 and
17 of Form 2A for multiple species, shouldn't the draft permit also
require that acute WET tests using fish species also be conducted to
meet the data requirements of Form 2A? W/o such a requirement, 40 CFR
Part 122.21(j) will not be met and this could be a basis for EPA
objection. I know we had discussions with Dave and Mike T. at the midyr
about this general topic, but don't think we've resolved a standard
course of action.
6) The permit application reports a bromoform avg conc of 83 ug/I. The
EPA human health criterion for consumption of water and organisms is 4.3
ug/I. We are not sure what, if any, dilution is available. Is there a
need for a bromoform limit in this permit? If not, why not?
7) The permit application reports chlorodibromomethane and
dichlorobromomethane avg concs of 24.0 and 4.13 ug/I, respectively. The
EPA human health criterion for consumption of water and organisms is
0.41 ug/I for both parameters. We are not sure what, if any, dilution
is available. Is there a need for limits for these in this permit? If
not, why not?
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4/29/2021 Mail - Denard, Derek - Outlook
[Fwd: cyanide discussion w/ NC - tentative agreement]
Tom Belnick <[e-mail]>
Tue 7/30/2002 10:55 AM
To: DENR.NPDES.DWQ <[e-mail]>
0 1 attachments (8 KB)
[Fwd: cyanide discussion w/ NC - tentative agreement];
fyi.... marshal) suggested we agree upon a future CN approach, then
modify our RPA for cyanide. Per Wayne Turnbull (EPA lab), a PQL of 10
ug/I should be no problem for a contract lab using automated equipment.
Mailto:[e-mail]
N.0 DENR-DWQ/NPDES Unit
1617 Mail Service Center, Raleigh NC 27699-1617
Work: [phone] ext. 543
Fax: [phone]
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4/29/2021 Mail - Denard, Derek - Outlook
cyanide discussion w/ NC - tentative agreement
Hyatt.Marshall <[e-mail]>
Tue 7/30/2002 10:02 AM
To: Stewart.Dee <[e-mail]>
Cc: Ejimofor.Caroline <[e-mail]>; Turnbull.Wayne <[e-mail]>;
teresa.rodriguez <[e-mail]>; tom.belnick <[e-mail]>; larry.ausley
<[e-mail]>
After today's discussion w/ EPA and NC permits and lab staff, it was
tentatively agreed (pending Dave Goodrich's approval) that:
- NC can continue to use 10 ug/I as the quantitation level for cyanide
for most discharge situations.
- for freshwater situations where NC has a 5 ug/I (chronic) WQ
criterion, NC will require more sensitive analytical methods to be used
when the discharge:7Q10 flow ratio is 1:1 or less. Use of these more
sensitive methods should measure down to 5 ug/I or so.
- for saltwater situations (where NC uses a 1 ug/I (acute) WQ
criterion), NC will require more sensitive analytical methods to be used
when the discharge:lowflow ratio is 4:1 or less. Use of these more
sensitive methods should measure down to 5 ug/I or so.
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4/29/2021 Mail - Denard, Derek - Outlook
Cyanide RPA Procedures
Tom Belnick <[e-mail]>
Thu 10/3/2002 10:22 AM
To: DENR.NPDES.DWQ <[e-mail]>
Here's something to print and retain in your Guidance Manual. Based on
recent negotiations with EPA, NPDES is considering a cyanide PQL of 10
ug/I to be appropriate due to the analytical variability near this
concentration range. While many labs are currently reporting values
below this PQL, we will not treat those values as valid numbers for RPA
purposes. Below are some RPA examples:
Example 1). All data reported are below 10 ug/I (e.g., <5, <10, 7, 9,
<5). In this instance, we consider all values to be non -detects, since
there are no positive detections above 10 ug/I. There is no need to do
RPA, and there should be no limit. If this is a municipal with
pretreatment program, cyanide monitoring could be delegated to the
pretreatment program (LTMP/STMP).
Example 2). There are some detections above 10 ug/I (e.g., <2, <5, <10,
14, <5, 7, 3). Lets assume the allowable effluent concentration is 20
ug/I. In this instance, we would need to conduct RPA since there is a
positive detection above 10 ug/I. For all reported values below 10 ug/I
(<2, <5, <10, 7, 3), substitute a modified value of 5 ug/I in the RPA
(based on 1/2 of the accepted PQL). Then include the positive values
above 10 ug/I and run the RPA.
Mailto:[e-mail]
N.0 DENR-DWQ/NPDES Unit
1617 Mail Service Center, Raleigh NC 27699-1617
Work: [phone] ext. 543
Fax: [phone]
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4/29/2021 Mail - Denard, Derek - Outlook
[Fwd: RE - Cyanide]
Tom Belnick <[e-mail]>
Wed 8/8/2007 10:20 AM
To: Mike Templeton <[e-mail]>
0 1 attachments (186 KB)
[Fwd: RE - Cyanide];
you probably also missed this one
Tom Belnick, Environmental Specialist
N.C. Division of Water Quality
Point Source Branch
919-733-5083, ext. 543
919-733-0719 (fax)
[e-mail]
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4/29/2021 Mail - Denard, Derek - Outlook
RE - Cyanide
Joe Corporon <[e-mail]>
Wed 8/8/2007 10:14 AM
To: Tom Belnick <[e-mail]>
1 attachments (183 KB)
RE - Cyanide;
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4/29/2021 Mail - Denard, Derek - Outlook
Cyanide - BIMS, Calculations, Compliance and Footnotes
Joe Corporon <[e-mail]>
Mon 4/16/2007 12:46 PM
To: Matt Matthews <[e-mail]>; DENR.EASTNPDES.DWQ<[e-mail]>;
DENR.WESTNPDES.DWQ <[e-mail]>
Cc: Jeanne Phillips <[e-mail]>
0 3 attachments (177 KB)
MEMORANDUM --Final.doc; Cyanide Footnote 5.doc; Message Text;
* *ROCs* - Please forward this email with attached files to your
assigned contact at the Regional Office and copy the Regional
Supervisor. Call your contact to discuss the attached
instructions. Problems? Questions? >call Joe.
* *Permit Writers* - alter/add footnotes to permits requiring
cyanide, but only during renewal or as part of some other required
permit modification. We will NOT reopen an active permit just for
cyanide.
* *Regional personnel* need to evaluate cyanide compliance in BIMS
guided by the attached instructions. If BIMS generates a
"violation," for cyanide, you must decide if it's "real" (see
attached documents). If in error, add your notes in BIMS under
"Comments" as "/No action-BIMS calculation error/" or otherwise
proceed with the NOV.
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Michael F. Easley, Governor
State of North Carolina William G. Ross, Jr., Secretary
Department of Environment and Natural Resources Alan W. Klimek, P.E., Director
Division of Water Quality

North Carolina Division of Water Quality 1617 Mail Service Center Raleigh, NC 27699-1617 [phone] Customer Service
1 800 623-7748

MEMORANDUM

To: Matt Matthews, Point Source Branch Supervisor

Through: Susan Wilson (NPDES West) and Gil Vinzani (NPDES East)

From: Committee to Evaluate Cyanide Compliance
Vanessa Manuel
Agyeman Adu-Poku
Joe Corporon, Chr.

Date: April 13, 2007

Subject: Revised Permit Footnote and Instructions
for Calculating Averages and Evaluating Cyanide Compliance
_________________________________________________________________________________

SCOPE: Cyanide limits/monitoring requirements affect approximately 99 NPDES permits.

DWQ formally recognizes uncertainties in quantifying cyanide minimum
levels in a wastewater matrix. While many North Carolina-certified
laboratories offer a Minimum Level (ML) or Practical Quantitation Level
(PQL) of 5 µg/L for cyanide, DWQ questions all values reported below 10
µg/L and formally considers these “zero” for compliance purposes.

PROBLEM 1: BIMS data-entry personnel may not “interpret” DMR parameter values.
Regardless of DWQ's stated “<10 µg/L = zero,” a value below 10 µg/L may
generate a limit violation for cyanide when entered into BIMS. These false
positive “violations” in turn automatically upload to EPA 's PCS System,
thus instigating a Watch List status for the Permittee.

PROBLEM 2: Permittees often calculate weekly averages inappropriately, and cyanide
footnotes in existing permits (effluent page) are missing or inconsistent.

The Committee offers the following solutions:

1) Permit Writers will include new footnote (see attached) in all new permits/renewals containing cyanide.
2) Instructions – Evaluating Cyanide Compliance (see attached) will be sent to each Regional Supervisor.
The Committee will also instruct central office ROCs in the correct procedures to calculate averages, and
ROCs will in turn instruct their Regional counterparts.
3) BIMS oversight/data entry (Jeanne Phillips) has volunteered to conduct quarterly checks of PCS
cyanide violations to prevent error upload to the EPA Watch List.

Cyanide Footnote – April 2007

Table Footnote – [to Effluents and Limits and Monitoring Conditions page].

6) Cyanide – The Division shall consider all cyanide values reported below 10 µg/L to
be “zero” for compliance purposes. However, Discharge Monitoring Reports (DMRs)
shall record all values reported by a North Carolina-certified laboratory (even if
these values fall below 10 µg/L).

Instructions – Evaluating Cyanide Compliance

Justification: Because of uncertainties in quantifying low-level cyanide in a wastewater
matrix, DWQ’s Laboratory Certification questions values reported at Quantitation Levels
(QLs) below 10 µg/L. However, the Permittee is instructed to record all values on Discharge
Monitoring Reports (DMRs), as reported by a North Carolina-certified laboratory, even if
these values fall below 10 µg/L (see footnote to effluent page, March 2007).

To calculate cyanide averages for permit limit compliance, include all reported DMR values,
but consider numbers below 10 ug/L to be “zero.” Then compare the resultant average to the
permit limits.

EXAMPLE CALCULATIONS:

Given Weekly Average permit limit = 5.0 ug/L
Given Daily Maximum permit limit = 15.0 ug/L

DATA -- Consider the following sets of four sample events, each with analytical values, sums,
and averages where: * = a DMR value < 10 ug/L = zero.

a. 9 * b. 14 c. 9 *
13 9 * 18
7 * 13 7 *
+ 8 * + 7 * + 6 *
sum 13 sum 27 sum 18

13 ÷ 4 = 3.25 [<5.0] 27 ÷ 4 = 6.75 [>5.0, all <15] 18 ÷ 4 = 4.5 [<5.0, but 1 hit >15]
Weekly Avg.: Compliant Weekly Avg.: Noncompliant Weekly Avg.: Compliant
Daily Max.: Compliant Daily Max.: Compliant Daily Max.: Noncompliant

d. 9 * e. 9 *
10 ** 8 *
18 7 *
+ 8 * + 6 *
sum 28 sum 0

28 ÷ 4 = 7.0 [>5.0, hit >15] 0 ÷ 4 = 0 [< 5.0, all < 15.0]
Weekly Avg.: Noncompliant Weekly Avg.: Compliant
Daily Max.: Noncompliant Daily Max.: Compliant

** note: 10 = real number because only <10 = 0.