NC0088099_Fact Sheet_20171201

DEQ / DWR / NPDES
EXPEDITED FACT SHEET - NPDES PERMIT DEVELOPMENT
NPDES Permit NCO088099
Derek Denard. Compliance & Exuedited Permittinn ITnit / 919_R07_61M 17Nnv')n17
FACILITY SUMMARY: This facility is a conventional technology water treatment plant [coagulation,
flocculation, sedimentation, and filtration] with discharge of wastewaters from media filter backwash and
sedimentation basins with a design potable flowrate of 1 MGD and a maximum, monthly average
wastewater discharge of 0.052 MGD, with water and wastewater treatment consisting of,
• dual (2) each 750 -GPM pumps (raw water)
• dual (2) sedimentation basins with tube settlers (40 -minute retention)
• dual (2) filters (high -rate multimedia)
• clearwell for finished water (300,000 gallons)
• dual (2) each 750 -GPM pumps
• liquid chemical feed system
• gas chlorination
• ammonia feed systems.
Chemical usage consists of
o Polymer Delpac © 20/20 [precipitator / anti -coagulant]
o chlorine dioxide [disinfection]
o CWS Ortho -Blend © [zinc orthophosphate corrosion inhibitor]
o sodium carbonate [softener]
Fact Sheet
Renewal 2017 -- NPDES Permit NCO088099
Page 1
Facility Information
Applicant/Facility Name
Town of Beech Mountain
Buckeye Lake WTP
Applicant Address
403 Beech Mountain Parkway, Beech Mountain,
NC 28604-8012
Facility Address
1400 Pine Ridge Road, Beech Mountain, NC 28604
Permitted Flow (MGD)
Not limited
Type of Waste
Water Plants and Water Conditioning Discharge
Conventional WTP System
— filter -backwash —
Facility Class
PC -1
County
Watauga
Permit Status
Renewal
Regional Office
WSRO
Stream Characteristics
Receiving Stream
Buckeye Creek
Stream Classification
C;Tr
Stream Segment
8-20-3-(2.5)
Drainage basin
Watauga
Summer 7Q 10 (cfs)
1.9
Subbasin
[HUCI
04-02-01
[060101030305]
Winter 7Q10 (cfs)
1.1
Use Support
No Data
30Q2 (cfs)
2.5
303(d) Listed
Average Flow (cfs)
7.0
State Grid
C11NW
IWC (%)
4.1
USGS Topo Quad j
Elk Park, NC
FACILITY SUMMARY: This facility is a conventional technology water treatment plant [coagulation,
flocculation, sedimentation, and filtration] with discharge of wastewaters from media filter backwash and
sedimentation basins with a design potable flowrate of 1 MGD and a maximum, monthly average
wastewater discharge of 0.052 MGD, with water and wastewater treatment consisting of,
• dual (2) each 750 -GPM pumps (raw water)
• dual (2) sedimentation basins with tube settlers (40 -minute retention)
• dual (2) filters (high -rate multimedia)
• clearwell for finished water (300,000 gallons)
• dual (2) each 750 -GPM pumps
• liquid chemical feed system
• gas chlorination
• ammonia feed systems.
Chemical usage consists of
o Polymer Delpac © 20/20 [precipitator / anti -coagulant]
o chlorine dioxide [disinfection]
o CWS Ortho -Blend © [zinc orthophosphate corrosion inhibitor]
o sodium carbonate [softener]
Fact Sheet
Renewal 2017 -- NPDES Permit NCO088099
Page 1

ELIGIBILITY FOR COVERAGE UNDER THE GENERAL PERMIT NCG590000: The Buckeye
Lake WTP is not eligible for the general permit because there is not enough data to make this
determination. The facility needs a greater than 75% passing rate for twelve (12) quarters of active
discharges and passing results for the most recent four (4) consecutive quarters.
RENEWAL SUMMARY: This permit reflects discharge at Outfall 001. DWR updated the following:
1. The facility map has been updated.
2. Regulatory citations have been added.
3. Electronic reporting of discharge monitoring reports (eDMR) has been added in Section A. (3.).
4. In accordance with water treatment permitting strategy for conventional technology, the following
changes have been made to this permit:
a. The monitoring frequency for Total Suspended solids (TSS), pH, Total Residual Chlorine
(TRC) and Turbidity has been decreased from weekly to 2/month. For flow less than 0.5
MGD, conventional parameters require 2/month sampling. The maximum monthly average
flow for this facility is 0.052 MGD.
b. The maximum monthly average flow for this facility is 0.052 MGD.
c. Quarterly ammonia nitrogen monitoring has been added because this facility utilizes
ammonia nitrogen/chloramines.
d. Since this facility is a conventional WTP with a discharge greater than 0.050 MGD,
quarterly Total Nitrogen (TN) and Total Phosphorus (TP) monitoring has been added.
5. Total Manganese and Iron monitoring has been removed because the EPA approved removal of NC
aquatic life standard as part of 2007-2016 Triennial review. Therefore, there are no limits to compare
monitoring data for these parameters.
6. Total Copper has been removed because data does not indicate reasonable potential to the exceed
water quality standard.
7. Effluent and upstream quarterly monitoring for Total Hardness has been added. Effluent hardness
sampling should be performed in conjunction with sampling for hardness dependent metals (Zinc).
The Permittee shall sample instream hardness, upstream of the facility's'discharge. The sample shall
be representative of the hardness in the receiving stream. Please see discussion below for more
information.
8. The daily maximum limit for Total Residual Chlorine (TRC) has been changed to 28 µg/1.
9. Toxicity monitoring has been updated to include Chronic Whole Effluent Toxicity (WET) testing
using Ceriodaphnia dubia to be performed as a 7 -day pass/fail test at 4.1% effluent
concentration, quarterly in January, April, July and October [See condition A. (2.)]. The
parameter code is TGP3B.
In response to comments from the Town of Beach Mountain, the following chances have been made for the
final permit:
10. Since Buckeye Creek is not currently impaired for Turbidity as indicated on the 303(d) list, the
effluent limits and the footnote have been removed in accordance with current WTP permitting
strategy. For the final permit, Turbidity monitoring has been changed to monitoring only with no
instream monitoring required to verify compliance.
DISCUSSION OF CHANGES FOR RENEWAL: For the WTP Permitting Strategy, please refer to the
Division of Water Quality October, 14 2009 memorandum by Julie Grzyb.
Flow (mgd) [50050] — Flow is greater than 0.050 MGD. According to the WTP stagey, conventional
technology WTPs with flows greater than 0.050 MGD must monitor flow by usage of a continuous
(frequency) recording (sample type) device.
Total Suspended Solids (TSS) (mg/1) [CO530] — The monitoring frequency for Total Suspended solids
(TSS), pH, Total Residual Chlorine (TRC) and Turbidity has been decreased from weekly to 2/month. For
Fact Sheet
Renewal 2017 — NPDES Permit NCO088099
Page 2

flows less than 0.5 MGD, these conventional parameters require 2/month sampling. The maximum monthly
average flow for this facility is 0.052 MGD.
pH (su) [00400] — The monitoring frequency for Total Suspended solids (TSS), pH, Total Residual
Chlorine (TRC) and Turbidity has been decreased from weekly to 2/month. For flows less than 0.5 MGD,
these conventional parameters require 2/month sampling. The maximum monthly average flow for this
facility is 0.052 MGD.
Total Residual Chlorine (TRC) [50060] - The daily maximum limit for Total Residual Chlorine (TRC) has
been changed to 28 gg/1. Please see attached IWC calculation spreadsheet indicating an allowable TRC
concentration of 419 µg/1. The daily maximum limit for TRC is capped at 28 gg/1 to protect aquatic acute
toxicity. The following footnote also applies to TRC:
➢ The Division shall consider all effluent total residual chlorine values reported below 50 gg/L to be in
compliance with the permit. However, the permittee shall continue to record and submit all values
reported by a North Carolina certified laboratory (including field certified), even if these values fall
below 50 g/L.
The monitoring frequency for Total Suspended solids (TSS), pH, Total Residual Chlorine (TRC) and Turbidity
has been decreased from weekly to 2/month. For flows less than 0.5 MGD, these conventional parameters
require 2/month sampling. The maximum monthly average flow for this facility is 0.052 MGD.
Turbidity (ntu) [00070] — Since Buckeye Creek is not currently impaired for Turbidity as indicated on the
303(d) list, the effluent limits and the footnote have been removed in accordance with current WTP
permitting strategy. For the final permit, Turbidity monitoring has been changed to monitoring only with no
instream monitoring required to verify compliance. The monitoring frequency for Total Suspended solids
(TSS), pH, Total Residual Chlorine (TRC) and Turbidity has been decreased from weekly to 2/month. For
flows less than 0.5 MGD, these conventional parameters require 2/month sampling. The maximum monthly
average flow for this facility is 0.052 MGD.
Total Aluminum (µg/1) [010042] — The permittee completed an older Form C-WTP (03/05), which does
include the questionnaire about specific chemical usage. There is no certainty that Aluminum is not in use. The
maximum reported was 2070 gg/l. Therefore, monitoring only is maintained for this permit renewal.
Total Iron (µg/1) [01045] & Total Manganese (µg/1) [01055] — Iron and manganese no longer have water
quality standards. Therefore, there are no limits to compare monitoring data for these parameters. The NC
2007-2015 Water Quality Standard (WQS) Triennial Review was approved by the NC Environmental
Management Commission (EMC) on November 13, 2014. The US EPA subsequently approved the WQS
revisions on April 6, 2016, with some exceptions. Iron and Manganese standards were removed.
Additionally, Iron sulfate/ferrous sulfate is not in use at this facility. Therefore, monitoring for Iron and
Manganese are removed for the permit renewal.
Total Copper (µg/1) [01042] — See RPA discussion below.
Total Zinc (µg/1) [010042] — See RPA discussion below. Zinc orthophosphate is in use.
Total Fluoride (mg/1) [00951] —The permittee completed an older Form C-WTP (03/05), which does
include the questionnaire about specific chemical usage. Since Fluoride was not monitoring for in the
previous permit it can be assumed that it is not in use at this facility.
Ammonia Nitrogen (mg/1) [CO610] — Quarterly ammonia nitrogen monitoring has been added because this
facility utilizes ammonia nitrogen/chloramines.
Total Nitrogen (TN) [CO600] & Total Phosphorus (TP) [CO665] — Since this facility is a conventional
WTP with a discharge greater than 0.050 MGD, quarterly Total Nitrogen (TN) and Total Phosphorus (TP)
monitoring has been added.
Total Hardness (mg/1) [00900] — Effluent hardness sampling and instream hardness sampling, upstream of the
discharge, are inserted into all permits with facilities monitoring for hardness -dependent metals to ensure the
Fact Sheet
Renewal 2017 -- NPDES Permit NC0088099
Page 3

accuracy of the permit limits and to build a more robust hardness dataset. Please see the section titled NPDES
Implementation for lnstream Metals Standards in this factsheet for more detailed information.
WHOLE EFFLUENT TOXICITY (WET) TESTING: With an IWC > 0.25%, this permit requires
Chronic Whole Effluent Toxicity (WET) testing using Ceriodaphnia dubia to be performed as a 7 -day
pass/fail test at 4.1% effluent concentration., quarterly in January, April, July and October [See condition A.
(2.)]_ The parameter code is TGP3B. Review of Whole Effluent Toxicity (WET) testing data from July
2013 to Oct 2015 found an overall pass rate of 100% (9 out of 9 tests). The data only represents nine (9)
quarters of WET testing. Data after October 2415 was not reported on eDMRIDMR. The Aquatic Toxicity
Branch provided the following data indicating that they reported fathead minnow 24 PF or the last four
quarters as passed. The previous permit required Chronic Whole Effluent Toxicity (WET) testing using
C'eriodaphnia dubia to be performed as a 7 -day pass/fail test at 90% effluent concentration with the wrong
parameter code THP3B. This code is for reporting the chronic value.
Test Results
Max
Min
I estmg months: �M Apr jui Uct
NPDES
Test Date
.1 Ttype
Resutt w LabNum . Compliance Nt
NCO088099/001
7111/2017
Fthd24PF
Pass 14
N1CO088099/001
4/11/2017
Fthd24PF
Pass 14
NICO088099/001
1/10/2017
Fthd24PF
Pass 14
NC0088099/001
10/25/2716
Fthd24PF
Pass 14
COMPLUNCE HISTORY: No violations occurred for the last 5 years (Aug2012-Ju12017). See
attachment BIMS monitoring report violations indicating no action for monitoring frequencies.
DATA SUMMARY:
Avera! -,e Flow for Oct2015-MaN2017
Parameter Max Min Count UoM
50050 - Flow, in conduit or thru treatment plant 1 0.052 0.002 3611 mgd
DMR Daily Parameter Values for Dec2012toMay2017
Parameter -T
Max
Min
Average
Count
PQL UoM
00070 - Turbidity
80
0.1
4.2
386
ntu
01042 - Copper, Total (as Cu)
5
1
4.7
13
5 ug/1
01045 - Iron, Total (as Fe)
3150
46
464.1
26
ug/l
01055 - Manganese, Total (as Mn)
213
17
67.0
13
ug/I
01092 - Zinc, Total (as Zn)
100
8
29.7
14
10,100 ug/I
01105 - Aluminum, Total (as Al)
2070
120
605.5
26
ug/l
50050 - Flow, in conduit or thru treatment plant
0.65
0.001
0.026
1235
mgd
50060 - Chlorine, Total Residual
17
1
13.3
212
17 ug/1
C0530 - Solids, Total Suspended - Concentration
31
2.5
7.8
235 2.5,5,10 mg/I
Parameter Tj Location - Max Min Average Count UoM
-:00070 - Turbidity Downstream 35 0.6 3.5 82 ntu
Effluent 34 0.1 4.2 222 ntu
Upstream 80 0.55 5.0 82 ntu
Fact Sheet
Renewal 2017 -- NPDES Permit NCO088099
Page 4

RPA: The need for toxicant limits is based upon a demonstration of reasonable potential to exceed water
quality standards, a statistical evaluation that is conducted during every permit renewal utilizing the most
recent effluent data for each outfall. The RPA is conducted in accordance with 40 CFR 122.44 (d) (i). The
NC RPA procedure utilizes the following: 1) 95% Confidence Level/95% Probability; 2) assumption of
zero background; 3) use of/z detection limit for "less than" values; and 4) streamflows used for dilution
consideration based on 15A NCAC 2B.0206. Effective April 6, 2016, NC began implementation of
dissolved metals criteria in the RPA process in accordance with guidance titled NPDES Implementation of
Instream Dissolved Metals Standards, dated June 10, 2016.
A reasonable potential analysis was conducted on effluent toxicant data collected between Oct2015-
May2017. Pollutants of concern included toxicants with positive detections and associated water quality
standards/criteria. Based on this analysis, the following permitting actions are proposed for this permit:
• No Limit or Monitoring: The following parameter will not receive a limit or monitoring, since they
did not demonstrate reasonable potential to exceed applicable water quality standards/criteria and
the maximum predicted concentration was <50% of the allowable concentration: Copper.
• MonitoriLag Only: Zinc demonstrate reasonable potential to exceed applicable water quality
standards/criteria and the maximum predicted concentration was <50% of the allowable
concentration. However, since Zinc orthophosphate is in use at this facility, monitoring only will be
maintained for the permit renewal.
NPDES Implementation of Instream Dissolved Metals Standards — Freshwater Standards
The NC 2007-2015 Water Quality Standard (WQS) Triennial Review was approved by the NC
Environmental Management Commission (EMC) on November 13, 2014. The US EPA subsequently
approved the WQS revisions on April 6, 2016, with some exceptions. Therefore, metal limits in draft
permits out to public notice after April 6, 2016 must be calculated to protect the new standards - as
approved.
Table 1. NC Dissolved Metals Water Ouality Standards/Aquatic Life Protection
Parameter
Acute FW, µg/1
(Dissolved)
Chronic FW, µg/1
(Dissolved)
Acute SW, µg/1
(Dissolved)
Chronic SW, µg/1
(Dissolved)
Arsenic
340
150
69
36
Beryllium
65
6.5
---
---
Cadmium
Calculation
Calculation
40
8.8
Chromium III
Calculation
Calculation
---
---
Chromium VI
16
11
1100
50
C2p2er
Calculation
Calculation
4.8
3.1
Lead
Calculation
Calculation
210
8.1
Nickel
Calculation
Calculation
74
8.2
Silver
Calculation
0.06
1.9
0.1
Zinc
Calculation
Calculation
90
81
Table 1 Notes:
1. _FW= Freshwater, SW= Saltwater
2. Calculation = Hardness dependent standard
3. Only the aquatic life standards listed above are expressed in dissolved form. Aquatic life standards
for Mercury and selenium are still expressed as Total Recoverable Metals due to bioaccumulative
concerns (as are all human health standards for all metals). It is still necessary to evaluate total
recoverable aquatic life and human health standards listed in 15A NCAC 2B.0200 (e.g., arsenic at
Fact Sheet
Renewal 2017 -- NPDES Permit NC0088099
Page 5

10 µg/1 for human health protection; cyanide at 5 µg2 and fluoride at 1.8 mg/L for aquatic life
protection).
Table 2. Dissolved Freshwater Standards for Hardness -Dependent Metals
The Water Effects Ratio (WER) is equal to one unless determined otherwise under 15A
NCAC 02B .0211 Subparagraph (11)(d)
Metal
NC Dissolved Standard, 1
Cadmium, Acute
WER*{1.136672-[1n hardness](0.041838)} e^{0.9151 [In hardness] -3.1485}
Cadmium, Acute Trout waters
WER* {1. 136672 -[In hardness](0.041838)} e^{0.915I[In hardness] -3.6236}
Cadmium, Chronic
WER*{1.101672-[ln hardness](0.041838)} e^{0.7998[ln hardness] -4.4451}
Chromium III, Acute
WER*0.316 e^{0.8190[ln hardness]+3.7256}
Chromium III, Chronic
WER*0.860 a^{0.8190[ln hardness]+0.6848}
Copper, Acute
WER*0.960 e^{0.9422[ln hardness] -1.700}
Copper, Chronic
WER*0.960 e^{0.8545[ln hardness] -1.702}
Lead, Acute
WER*{1.46203-[In hardness](0.145712)} e^{1.273[ln hardness] -1.460}
Lead, Chronic
WER*{1.46203-[In hardness](0.145712)} e^{1.273[ln hardness] -4.705}
Nickel, Acute
WER*0.998 e^{0.8460[ln hardness]+2.255}
Nickel, Chronic
WER*0.997 e^{0.8460[ln hardness]+0.0584}
Silver, Acute
WER*0.85 • e^{1.72[ln hardness] -6.59}
Silver, Chronic
Not applicable
Zinc, Acute
WER*0.978 a^{0.8473[ln hardness]+0.884}
Zinc, Chronic
WER*0.986 e^{0.8473[ln hardness]+0.884}
General Information on the Reasonable Potential Analysis RPA
The RPA process itself did not change as the result of the new metals standards. However, application of
the dissolved and hardness -dependent standards requires additional consideration in order to establish the
numeric standard for each metal of concern of each individual discharge.
The hardness -based standards require some knowledge of the effluent and instream (upstream) hardness and
so must be calculated case-by-case for each discharge.
Metals limits must be expressed as `total recoverable' metals in accordance with 40 CFR 122.45(c). The
discharge -specific standards must be converted to the equivalent total values for use in the RPA
calculations. We will generally rely on default translator values developed for each metal (more on that
below), but it is also possible to consider case -specific translators developed in accordance with established
methodology.
RPA Permitting Guidance/W BELS for Hardness -Dependent Metals - Freshwater
The RPA is designed to predict the maximum likely effluent concentrations for each metal of concern,
based on recent effluent data, and calculate the allowable effluent concentrations, based on applicable
standards and the critical low -flow values for the receiving stream. If the maximum predicted value is
greater than the maximum allowed value (chronic or acute), the discharge has reasonable potential to
exceed the standard, which warrants a permit limit in most cases. If monitoring for a particular pollutant
indicates that the pollutant is not present (i.e. consistently below detection level), then the Division may
remove the monitoring requirement in the reissued permit.
Fact Sheet
Renewal 2017 -- NPDES Permit NCO088099
Page 6

To perform a RPA on the Freshwater hardness -dependent metals the Permit Writer compiles the
following information:
• Critical low flow of the receiving stream, 7Q10 (the spreadsheet automatically calculates
the 1 Q 10 using the formula 1 Q 10 = 0.843 (s7Q 10, cfs) 0.993
• Effluent hardness and upstream hardness, site-specific data is preferred
• Permitted flow
• Receiving stream classification
2. In order to establish the numeric standard for each hardness -dependent metal of concern and for
each individual discharge, the Permit Writer must first determine what effluent and instream
(upstream) hardness values to use in the equations.
The permit writer reviews DMR's, Effluent Pollutant Scans, and Toxicity Test results for any
hardness data and contacts the Permittee to see if any additional data is available for instream
hardness values, upstream of the discharge.
If no hardness data is available, the permit writer may choose to do an initial evaluation using a
default hardness of 25 mg/L (CaCO3 or (Ca + Mg)). Minimum and maximum limits on the
hardness value used for water quality calculations are 25 mg/L and 400 mg/L, respectively.
If the use of a default hardness value results in a hardness -dependent metal showing reasonable
potential, the permit writer contacts the Permittee and requests 5 site-specific effluent and upstream
hardness samples over a period of one week. The RPA is rerun using the new data.
The overall hardness value used in the water quality calculations is calculated as follows:
Combined Hardness (chronic)
(Permitted Flow, cfs *Av. Effluent Hardness m /L + (s7Q 10. cfs *Av . U stream Hardness m /L
(Permitted Flow, cfs + s7Q10, cfs)
The Combined Hardness for acute is the same but the calculation uses the 1Q10 flow.
3. The permit writer converts the numeric standard for each metal of concern to a total recoverable
metal, using the EPA Default Partition Coefficients (DPCs) or site-specific translators, if any have
been developed using federally approved methodology.
EPA default partition coefficients or the "Fraction Dissolved" converts the value for
dissolved metal at laboratory conditions to total recoverable metal at in -stream ambient
conditions. This factor is calculated using the linear partition coefficients found in The
Metals Translator. Guidance for Calculating a Total Recoverable Permit Limit from a
Dissolved Criterion (EPA 823-B-96-007, June 1996) and the equation:
_Cdiss = 1
Ctotal 1 + { [Kp.] [sstl+a>] [j0-6] }
Where:
ss = in -stream suspended solids concentration [mg/1], minimum of 10 mg/L used, and
Kpo and a = constants that express the equilibrium relationship between dissolved and
adsorbed forms of metals. A list of constants used for each hardness -dependent metal can
also be found in the RPA program under a sheet labeled DPCs.
Fact Sheet
Renewal 2017 -- NPDGS Permit NC0088099
Page 7

4. The numeric standard for each metal of concern is divided by the default partition coefficient (or
site-specific translator) to obtain a Total Recoverable Metal at ambient conditions.
In some cases, where an EPA default partition coefficient translator does not exist (ie. silver), the
dissolved numeric standard for each metal of concern is divided by the EPA conversion factor to
obtain a Total Recoverable Metal at ambient conditions. This method presumes that the metal is
dissolved to the same extent as it was during EPA's criteria development for metals. For more
information on conversion factors see the June, 1996 EPA Translator Guidance Document.
5. The RPA spreadsheet uses a mass balance equation to determine the total allowable concentration
(permit limits) for each pollutant using the following equation:
Ca = (s7010 + Qw) (Cwgs) — (s7Q 10) (Cb)
Qw
Where: Ca = allowable effluent concentration (µg/L or mg/L)
Cwqs = NC Water Quality Standard or federal criteria (gg/L or mg/L)
Cb = background concentration: assume zero for all toxicants except NH3* (µg/L or mg/L)
Qw = permitted effluent flow (cfs, match s7Q 10)
s7Q 10 = summer low flow used to protect aquatic life from chronic toxicity and human health through
the consumption of water, fish, and shellfish from noncarcinogens (cfs)
* Discussions are on-going with EPA on how best to address background concentrations
Flows other than s7Q 10 may be incorporated as applicable:
IQ 10 = used in the equation to protect aquatic life from acute toxicity
QA = used in the equation to protect human health through the consumption of water, fish, and
shellfish from carcinogens
30Q2 = used in the equation to protect aesthetic quality
6. The permit writer enters the most recent 2-3 years of effluent data for each pollutant of concern.
Data entered must have been taken within four and one-half years prior to the date of the permit
application (40 CFR 122.21). The RPA spreadsheet estimates the 95th percentile upper
concentration of each pollutant. The Predicted Max concentrations are compared to the Total
allowable concentrations to determine if a permit limit is necessary. If the predicted max exceeds
the acute or chronic Total allowable concentrations, the discharge is considered to show reasonable
potential to violate the water quality standard, and a permit limit (Total allowable concentration) is
included in the permit in accordance with the U.S. EPA Technical Support Document for Water
Quality -Based Toxics Control published in 1991.
7. When appropriate, permit writers develop facility specific compliance schedules in accordance with
the EPA Headquarters Memo dated May 10, 2007 from James Hanlon to Alexis Strauss on 40 CFR
122.47 Compliance Schedule Requirements.
8. The Total Chromium NC WQS was removed and replaced with trivalent chromium and hexavalent
chromium Water Quality Standards. As a cost savings measure, total chromium data results may be
used as a conservative surrogate in cases where there are no analytical results based on chromium
III or VI. In these cases, the projected maximum concentration (95th %) for total chromium will be
compared against water quality standards for chromium III and chromium V1.
9. Effluent hardness sampling and instream hardness sampling, upstream of the discharge, are inserted
into all permits with facilities monitoring for hardness -dependent metals to ensure the accuracy of
the permit limits and to build a more robust hardness dataset.
Fact Sheet
Renewal 2017 -- NPDES Permit NCO088099
Page 8

10. Hardness and flow values used in the Reasonable Potential Analvsis for this nermit included:
Parameter
Value
Comments (Data Source)
Average Effluent Hardness (mg/L)
25
default hardness
[Total as, CaCO3 or (Ca+Mg)]
Average Upstream Hardness (mg/L)
25
default hardness
[Total as, CaCO3 or (Ca+Mg)]
7Q10 summer (cfs)
1.9
NPDES Permit File/WLA/BIMS
1Q10 (cfs)
1.59
RPA Calculation
Maximum Monthly Average (MGD)
0.529
BIMS DMR data
Dec20l2toMay2Ol7; flow
Jun2014toMa 2017
Date: September 7, 2017
Permit Writer: Derek Denard
Fact Sheet
Renewal 2017 NPDES Permit NC0088099
Page 9

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IWC Calculations
Facility: Town of Beech Mountain - Buckeye Lake WTP
NCO088099
Prepared By: Derek Denard
Enter Design Flow (MGD): 0.051806
Enter s7Q10 (cfs): 1.9
Enter w7Q10 (cfs): 1.1
Total Residual Chlorine (TRC)
Daily Maximum Limit (ug/1)
Ammonia (Summer)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
1.9
s7Q10 (CFS)
1.9
DESIGN FLOW (MGD)
0.051806
DESIGN FLOW (MGD)
0.05181
DESIGN FLOW (CFS)
0.0803
DESIGN FLOW (CFS)
0.0803
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
4.05
IWC (%)
4.05
Allowable Conc. (ug/1)
419
Allowable Conc. (mg/1)
19.5
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
1.1
Monthly Average Limit:
200/100ml DESIGN FLOW (MGD)
0.05181
(If DF >331; Monitor)
DESIGN FLOW (CFS)
0.0803
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
24.66 Upstream Bkgd (mg/1)
0.22
IWC (%)
6.80
Allowable Conc. (mg/1)
23.4
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia fas NH3-N]
1. If Allowable Conc > 35 mg/l, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals); capped at 35 mg/I
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis); capped at 35 mg/I
4. BAT for Minor Domestics: 2 mg/I (summer) and 4 mg/I (winter)
5. BAT for Major Municipals: 1 mg/I (year-round)
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)
NPDES Server/Current VersionS/WLA; TB 1/16/2009

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REASONABLE POTENTIAL ANALYSIS
H1
H2
Use -PASTE 5PECtAL
Lha "PACTS SKCuU
Effluent Hardness
vaiUer':'h0" -Cc pv-
Upstream Hardness
Ymuac then 'COPY
- Ma imam data
. Maximum data
points = 56
paint! - 58
Date Data BDL=112DL Results
Date
Data BDL=112DL Results
1
25 25 Std Dev.
N/A
1
25 25 Std Dev.
N,,,
2
Mean
25.0000
2
Mean
25.0000
3
C.V.
0.0000
3
C.V.
0.0000
4
n
1
4
n
1
5
10th Per value
25.00 mg/L
5
10th Per value
25.00 mg/L
6
Average Value
25.00 mg/L
6
Average Value
25.00 mg/L
7
Max. Value
25.00 mg/L
7
Max. Value
25.00 mg/L
8
8
9
9
10
10
11
11
12
12
13
13
14
14
15
15
16
16
17
17
18
18
19
19
20
20
21
21
22
22
23
23
24
24
25
25
26
26
27
27
28
28
29
29
30
30
31
31
32
32
33
33
34
34
35
35
36
36
37
37
38
38
39
39
40
40
41
41
42
42
43
43
44
44
45
45
46
46
47
47
48
48
49
49
50
50
51
51
52
52
53
53
54
54
55
55
56
56
57
57
58
58
NCO088099 RPA, data
1 - 9/8/2017

r�::

Pall
Date Data
1 7/23/2013
2 1/21/2014 <
3 4/3/2014 <
4 7/1/2014 <
5 10/7/2014 <
6 1/13/2015 <
7 4/7/2015 <
8 7/14/2015 <
9 10/13/2015 <
10 7/12/2016 <
11 10/11/2016 <
12 1/10/2017 <
13 4/11/2017 <
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
REASONABLE POTENTIAL ANALYSIS
_
uaa "PASTE SPECL
Copper
Valvas` sewn "COP
Date
Data
. Maximum dao
Results
1
points = 58
BDL=1/2DL
Results
Std Dev.
1 1
Std Dev.
4 i;
5 2.5
Mean
2.3846
5 2.5
C.V.
0.1745
5 2.5
n
13
5 2.5
14
n
5 2.5
Mult Factor =
1.15
5 2.5
Max. Value
2.50 ug/I
5 2.5
Max. Pred Cw
2.88 ug/l
5 2.5
7
1/13/2015
5 2.5
11.3
Max. Value
5 2.5
4/7/2015
< 100
5 2.5
Max. Pred Cw
9
5 2.5
29
29
-2-
U" 'PASTE SPECI
Vafuan" Shen "COF
Maximum d0I.1
pwritu = 58
22.1643
0.6717
14
1.61
50.0 ug/L
80.5 ug/L
NCO088099 RPA, data
9/8/2017
Zinc
Date
Data
BDL=112DL
Results
1
4/2/2013
11
11
Std Dev.
2
4/30/2013
8
8
Mean
3
1/21/2014
16
16
C.V.
4
4/3/2014
14
14
n
5
7/1/2014
38
38
6
10/7/2014
10
10
Mult Factor =
7
1/13/2015
11.3
11.3
Max. Value
8
4/7/2015
< 100
50
Max. Pred Cw
9
7/14/2015
29
29
10
10/13/2015
20
20
11
7/12/2016
28
28
12
10/11/2016
20
20
13
1/10/2017
< 100
50
14
4/11/2017
< 10
5
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
U" 'PASTE SPECI
Vafuan" Shen "COF
Maximum d0I.1
pwritu = 58
22.1643
0.6717
14
1.61
50.0 ug/L
80.5 ug/L
NCO088099 RPA, data
9/8/2017

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