NC0085359_Response to Notice_20190627

Department of public Works
500 North Main Street
Suite #600
Monroe, NC 28112
T. 704.296.4217
www.unioncountync.gov JUL �- j� 9
51 U �,3
June 27, 2019
Ms. Julie Grzyb
Water Quality Permitting Section — NPDES
Division of Water Resources
North Carolina Department of Environmental Quality
1617 Mail Service Center
Raleigh, NC, 27699-1617
RE: Union County Public Works
Twelve Mile Creek Water Reclamation Facility
NPDES Permit Renewal, Permit No. NCO085359
Dear Ms. Grzyb:
The Union County Public Works Division is permitted to discharge 6.0 million gallons per day (mgd) of
treated effluent from the Twelve Mile Creek Water Reclamation Facility (WRF) to Twelve Mile Creek
under North Carolina National Pollutant Discharge Elimination System (NPDES) Pen -nit NC0085359.
The NPDES permit contains additional tiered flow limits for 7.5 mgd, 9 mgd, and 12 mgd. The WRF is
currently scheduled to complete construction for an expansion to 7.5 mgd in the fall of 2019. This
NPDES permit is scheduled to expire at midnight on December 31, 2019.
The enclosed application is for the renewal of the Twelve Mile Creek WRF NPDES permit. In
accordance with the requirements of federal (40 CFR 122) and state (15A NCAC 2H .0105(3))
regulations, we are submitting three signed copies of the completed application package and associated
attachments and figures. The application package includes the following information:
• NPDES Permit Application — EPA Form 2A
• EPA Form 2A Additional Information (Topographic Map, Site Map, Process Flow
Diagram and Process Narrative)
• Twelve Mile Creek WRF Sludge Management Plan
• Summary of First Species Effluent Toxicity Testing, 2015-2019
• Annual Priority Pollutant Analysis Results, 2016-2019
• Second Species Toxicity Testing Results, 2015-2018
• Technical Memorandum in support of the Reduction of Monitoring Frequency for
Exceptionally Performing Facilities

We have several comments and requests for changes on our current permit, as follows:
Reduction of Monitoring Frequency
In accordance with 15A NCAC 2B .0508(b)(1) and the October 2012 DWR Guidance Document for the
Reduction of Monitoring Frequency for Exceptionally Performing Facilities, Union County Public Works
respectfully requests a reduction in frequency monitoring for biochemical oxygen demand (BOD5), total
suspended solids (TSS), and ammonia. Effluent sampling results from the past three years demonstrate
that all state regulatory and guidance requirements have been met in support of this request. A complete
summary of the sampling data and analysis for the reduction of monitoring frequency is attached in Tab G
of this application.
Reasonable Potential Anal
Hazen and Sawyer conducted a reasonable potential analysis (RPA) for metals based on the available
effluent data. A receiving stream hardness was used from the County's 2005 Water Effects Ratio (WER)
Study for copper and zinc. The County will begin effluent sampling for hardness in the receiving stream
upstream of the discharge location. The stream hardness data will be forwarded to the Division.
Reasonable potential was not demonstrated for any of the metals except for silver. The reasonable
potential for silver is attributed to the low chronic silver water quality standard versus the method
detection level (MDL). All of the effluent sampling points indicated less than detection for silver. Our
understanding is that quarterly monitoring for silver may be required for one year using a MDL of less
than 1.0 ug/L. It should also be noted that the County is in the process of developing a Long Term
Monitoring Plan (LMTP) and updated headworks analysis for the Twelve Mile Creek WRF.
Instream Monitoring
We request that the instream monitoring requirement for dissolved oxygen be removed from the permit
(Sections A.(1), A.(2), A.(3), and A.(4)). 15A NCAC 2B requires instream monitoring for parameters that
are "water quality limited." A water quality limited segment is defined in NCAC as a segment "where it is
known that water quality does not meet applicable water quality standards or is not expected to meet there
even after the application of minimum treatment requirements." Per the Fact Sheet and the 2018
Integrated Report, Twelve Mile Creek is not impaired for dissolved oxygen due to naturally occurring
conditions. The Twelve Mile Creek receiving stream does not meet the definition of "water quality
limited." The Fact Sheet also states that low dissolved oxygen conditions have been attributed to natural
upstream conditions. Therefore, the instream monitoring for dissolved oxygen should be removed from
the permit.
We also request that the instream monitoring requirement for temperature be removed from Sections
A.(I), A.(2), A.(3), and A.(4) of the permit. Twelve Mile Creek is not listed as impaired for temperature
in the 2018 Integrated Report. Therefore, the instream monitoring requirement should be removed. The
Fact Sheet points out that the upstream and downstream temperatures do not vary by more than 2.8°C the
majority of the time based on hundreds of data points between 2012 and 2014.

UCPW's current CIP projects are also ongoing with projects including:
➢ Waxhaw Sewer Improvements - $295,000.00
➢ Blythe Creek Sewer Improvements - $3,083,200.00
➢ Forest Park PS Replacement & Interceptor Improvements - $2,540,000.00
➢ Crooked Creek I&I Study & Remediation - $2,538,300.00
➢ Suburban Estates PS replacemeit-$933,000.00
Union County Public Works continues to invest funds into SSES work, capital improvements,
maintenance and operations to improve the wastewater collection system. If further information
or details regarding the CCWRF Improvements, as well as, the CIP projects listed above are
required, please feel free to contact Greg Morgan, Superintendent/ORC, at 704-289-3288 or
myself at 704-296-4215.
Thank you for your consideration.
Sincerely,
4
Andrew Neff, PE
Water/Wastewater Division Director
cc: Hyong Yi, Public Works Administrator
Josh Brooks, Assistant Director, Water/Wastewater Operations
Greg Morgan, Utility Field Services Superintendent/ORC