NC0082694_More Information (Requested)_20210811

August 11, 2021

CERTIFIED MAIL 9590 9402 3950 8060 7368 96
RETURN RECEIPT REQUESTED

Zackery L. Foreman, WTP Supt.
Town of Dallas
210 N Holland St
Dallas, NC 28034

Subject: Request for Additional Information
Draft NPDES Permit NC0082694
Dallas WTP
Gaston County

Dear Mr. Foreman:
The Division has reviewed your application, received on February 21, 2020, for renewal of NPDES permit
NC0082694. 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. EPA Form 1 for water treatment plants, and EPA Form 2E for new and existing facilities, and EPA Form
2C tables A and C, and Table B (if believed present). These forms can be downloaded at the following
webpage: https://deq.nc.gov/about/divisions/water-resources/water-quality-permitting/npdes-
wastewater/npdes-permitting-process
2. Please provide five (5) days of Total Hardness (CaCO3 or (Ca + Mg)) data for the following:
a. effluent
b. upstream of Outfall 001.
3. Please confirm that the units of measure for all total copper data from October 2016 to present were
reported correctly. The values for copper appear to have been reported in mg/L (milligrams per liter) instead
of the unit of measurement indicated as µg/L (micrograms per liter). This is a very common reporting error.
It should also be noted that a method detection level reported of <0.005 µg/L (5 ng/L, nanograms per liter)
for copper would not be possible with conventual water quality laboratory methods that we are aware of.
You need to also review reported units of measurement for other metals data such as iron, manganese, and
aluminum. Please provide a list of any corrected values in response to this additional information request.
Please amend DMRs as necessary.
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 in order to calculate permit limitations. The
metal of concern for this permit renewal is copper.
To evaluate dissolved Copper, a Reasonable Potential Analysis (RPA) was conducted using copper DMR data
from October 2016 to March 2021. Assuming that the values reported for copper were in mg/L instead of µg/L,
results indicated a reasonable potential to exceed the new dissolved metals standard for copper. Consequently, the
following daily maximum limits (acute standard) and monthly average limit (chronic standard) for total copper
may be applied for this permit renewal:
Parameter Outfall Monthly Average Limit Daily Maximum Limit
Total Copper 001 763.31 µg/L 830.57 µg/L
To calculate the limits above a default hardness of 25 mg/L was entered for both the effluent and upstream values.
Additionally, a 7Q10 flow of 89 cfs was provided by the USGS on June 4, 2021. Additionally, the maximum
monthly average of 0.599 MGD for Outfall 001 was used as the effluent flow. The maximum monthly average
was based on flow data from April 2018 to March 2021. Calculation of final copper limits will be dependent on
the effluent and upstream hardness data that we have requested. For a summary of this information, please see the
attached RPA, “Dissolved to Total Metal Calculator”, and Low Flow information provided by the USGS.
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 requested additional information. Therefore, a default effluent hardness of 25 mg/L will
be used to calculate effluent limits for copper as indicated above. Please submit the additional information
requested by one of the following:

Electronically: [e-mail]

Address For USPS: Physical Address for parcel packages:
Attention: Derek Denard Attention: Wren Tredford
Division of Water Resources Division of Water Resources
WQ Permitting Section – NPDES WQ Permitting Section – NPDES
1617 Mail Service Center 512 N. Salisbury Street
Raleigh, NC 27699-1617 (9th Floor-Archdale Bldg)
Raleigh, NC 27604

If you have questions concerning the draft, please contact me at 919-707-3618, or via e-mail at
[e-mail].

Sincerely,
Derek Denard, Environmental Specialist
NPDES Compliance and Expedited Permitting
Division of Water Resources, NCDEQ

ec: NPDES File [Laserfiche]
Jack Foreman [[e-mail]]
RRO / Ori Tuvia [[e-mail]]; Andrew Pitner [[e-mail]]