NC0084425_More Information (Requested)_20170714

Water Resources
Environmental Quality
July 14, 2017
CERTIFIED MAIL 7002 0860 0006 58361080
RETURN RECEIPT REQUESTED
Mr. Ron Sink, CEO / General Manager
Davidson Water, Inc.
P.O. Box 969
Welcome, North Carolina 27374
Dear Mr. Sink:
ROY COOPER
Governor
MICHAEL S. REGAN
Secy etary
S. JAY ZIMMERMAN
Director
Subject: Request for Additional Information
Renewal Application
Davidson WTP
NPDES permit NCO084425
Davidson County
The Division has reviewed your application, received on December 1, 2016, for renewal of NPDES
permit NC0084425. To enable us complete our review in accordance with N.C.G.S. 143-215.1 and 15A
NCAC 2H.0105, please provide additional or revised information to address the following comments.
1. Please provide five (5) days of Total Hardness (CaCO3 or (Ca + Mg)) data for the effluent at
Outfall 001.
2. Review of our records indicates that there is no stream flow data documented for the receiving
stream. Please provide a 7Q10 and 30Q2 at the location of Outfall 001 [35.8535198°,
-80.3850868°], for the Yadkin River from the following contact with the US Geological Survey:
J. Curtis Weaver, Hydrologist, PE
USGS North Carolina Water Science Center
3916 Sunset Ridge Road
Raleigh, NC 27607
Phone: [phone] // Fax: [phone]
E-mail address -- jcweaver(a),usgs.gov
Internet address -- http://nc.water.usgs.gov/
The NC 2007-2014 Water Quality Standard (WQS) Triennial Review was approved by the NC
Environmental Management Committee (EMC) on November 13, 2014. The US EPA subsequently
approved the WQS revisions on April 6, 2016 with some exceptions. The NC Division of Water
Resources is required to implement the new dissolved metal standards in all permits public noticed after
April 6, 2016.
The new standards for most metals include acute standards. Furthermore, the freshwater standards for
several metals are expressed as the dissolved form of the metals, and seven metals have hardness -
dependent equations. As a result, the Division will need site-specific effluent hardness data and instream
hardness data, upstream of the discharge, for each facility monitoring these metals in order to calculate
permit limitations. The metal of concern for this perms renewal is Zinc.
State of North Carolina I Environmental Quality
1617 Mail Service Center I Raleigh, North Carolina 27699-1617
919-707-9000

Mr. Sink
July 14, 2017
Page 2 of 2
To evaluate dissolved Zinc, a Reasonable Potential Analysis (RPA) was conducted using data from
DMRs (May2013—May2017). Results indicated a reasonable potential to exceed the new dissolved metal
standard for Zinc. Consequently, the following daily maximum limits (acute standard) and monthly
average limits (chronic standard) for Total Zinc could be applied for this permit renewal:
Parameter Outfall Monthly Average Lunit Daily Maximum Limit
Zinc 001 125.7 gg/L 125.7 gg/L
Please note a default effluent hardness of 25 mg/L and a 7Q 10 of zero was used for the calculation of the
limits above. For upstream hardness, data was obtained from ambient stream monitoring station
Q2810000 located at the US Hwy 64 bridge over the Yadkin River. The average upstream hardness for
ten (10) samples collected from 2012 to 2014 was 22 29 mg/L. For a summary of this information, please
see the attached "Dissolved to Total Metal Calculator" Incidentally, the additional information requested
will be used in a recalculation for the draft permit.
If no response is received within 60 calendar days [per 15A NCAC 2H.0107(b)], the permit will be
renewed without the benefit of the requester additional information. Therefore, a default effluent
hardness of 25 mg/L (CaCO3 or (Ca + Mg)) and a 7Q 10 of zero will be used to calculate effluent limits
for Zinc as indicated above.
If you have any questions, please contact Derek Denard at 919-807-6307 or email at
derek [e-mail].
Sincerely,
Derek Denard, Environmental Specialist
Compliance & Expedited Permitting Unit
Division of Water Resources, NCDEQ
he Central Files
NPDES Program Files
WSRO Files
ec• George Smith [george smith@ncdenr gov]
Ron Sink [rsmk@davidsonwater com]

Date 7/14/2017
FACILITY Davidson Water, Inc -Davidson WTP
NPDES PERMIT NC008"25 Dissolved to Total Metal Calculator
In accordance with Fed'erad Regulations, permit limitations i ii-ist he vfritten as Total Metals pea 40 CFR 122.45(c)
Receiving Receiving Rec Stream
Stream Stream
1010
summer summer 7010
7010 (CFS) (MGD) MGD
-70-0 00 0 0000 0 0000
NPDES Total Suspended Combined Combined InsVeam InsVeam
Upstream
Solids Hardness Hardness Wastewater Wastewater
Flow Limit Hardness
-Fixed Value- chronic Acute Concentration Concentration
MGD (mg/L) (mg/L) (mg/L) (Chronic) (Acute) Average (mg/L)
0 8798-
Upstream Hard Avg (mg/L) =
EFF Hard Avg (mg/L) =
Effluent
Hardness
Average
(mg/L)
2229
25
US EPA
Dissolved Metals Translators- using
PARAMETER Default Partition
Chronic Acute Coefficients
u /I fug/11 streams
Maximum Allowable Effluent Concentration
(MAEC) as ail&al Odd
=Dissolved Metal, Translator
COMMENTS (identify parameters to PERCS Branch to maintain in facility's LTMP/STMP)
Chronic Acute
[ug/11 u A
Cadmium (d) 015 082 0 252
059 324
Cd -Trout stream 015 051 0 252
059 201
Chromium III (d)(h) 24 183 0202
11773 90508
Chromium VI (d) 11 16 1 000
11 00 1600
Chromium, Total (t)
N/A N/A
Copper (d)(h) 27 36 0 348
788 1047
Lead (d)(h) 0541 14 0 184
294 7549
Nickel (d)(h) 16 145 0 432
37 23 33521
N1- WS streams t)
25 N/A
Silver (d)(h,acute) 006 030 1 000
0061 030
Zinc (d)(h 36 36 0 288
12673 12571
Beryllium 651 6511 000 6 66
Arsenic (d) 150 340 1 000 150 340
(d) = dissolved metal standard See 15A NCAC 02B 0211 for more information
(h) = hardness -dependent dissolved metal standard See 15A NCAC 02B 0211 for more information
(t) = based upon measurement of total recoveable metal See 15A NCAC 02B 0211 for more information
The Human Health standard for Nickel in Water Supply Streams is 25 mg/L which is Total Recoverable metal standard
The Human Health standard for Arsenic is 10 pg/L which is Total Recoverable metal standard
10
25 000
25 000
100 0000
100 0000
22 29 25