NC0021873_Comments_20180627

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ROY COOPER
Govei nom
MICHAEL S.REGAN
Secretory
w LINDA CULPEPPER
Water Resources Interim Director
ENVIRONMENTAL QUALITY
June 27, 2018
Certified Mail#7016 2140 0000 4371 0844
Return Receipt Request
Ms. Olivia Munzer
Western Piedmont Coordinator
Habitat Conservation Division
NC Wildlife Resources Commission
1721 Mail Service Center
Raleigh,NC 27699
Subject: Review Comments
NPDES Permit NC0021873
Mayodan WWTP
Rockingham County
Dear Ms. Munzer:
Thank you for your review of the draft renewal of NPDES Permit NC0021873 for the Mayodan
Wastewater Treatment Plant in Rockingham County. In the review, you made two requests for
changes,based on the presence of rare, threatened and endangered aquatic life species:
1. To encourage the Permittee to switch to an alternate disinfection media from chlorine, and,
2. To develop site specific ammonia limits in order to better protect sensitive rare,threatened
and protected mussels and other aquatic life.
The Division offers the following responses to your comments:
(1.)We have no mechanism for requiring disinfection with alternatives to chlorination as long
as the permittee is in compliance with permit limits and is not expanding the plant capacity
or changing the treatment. A review of Discharge Monitoring Reports from January 2014
through February 2018 shows all reported results were< 50 ug/L. The Division considers
all effluent Total Residual Chlorine values reported below 50 ug/L to be in compliance
with the permit. The facility conducts regular quarterly Whole Effluent Toxicity Tests in
accordance with EPA and NC requirements at the IWC concentration. The facility passed
all quarterly chronic toxicity tests as well as all four rd species chronic toxicity tests for
the past five years. I will add Language to the Cover Letter to the final permit to inform
the permittee of this concern, and strongly recommend that permittee investigate
converting to UV disinfection from chlorination/dichlorination
State of North Carolina I Environmental Quality I Water Resources
1617 Mail Service Center I Raleigh,North Carolina 27699-1617
919 807 6300

Page 12
(2.)The plant is currently meeting all ammonia nitrogen water quality limits. I have calculated
the in-stream ammonia concentration using DMR data for effluent flow and ammonia—N
concentration and conservative 7Q10 flows for the Mayo river at the discharge site. The
Division uses 0.22 mg/L as the normal background ammonia concentration for evaluations.
The resulting calculated in-stream concentrations were generally the same or slightly
higher than the background ammonia—N concentrations(0.22 to 0.25 mg/L), allowing for
7Q10 dilution. The highest in-stream concentration was 0.34 mg/L in July 2016. See
attached Ammonia-N predicted Instream Concentrations, Mayo WWTP January 2015 —
February 2018. Again, language will be added to the permit cover letter addressing the
concerns about ammonia and sensitive aquatic life, encouraging the facility to continue
addressing ammonia discharges.
Thank you again for your review.
Sincerely,
Qais Banihani, Environmental Engineer
NPDES Complex Permitting Unit

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Dec-17 0.790 1.22 2.503 131 0.24 1.8
Jan-18 1.050 1.63 1.136' 131 0.23 1.8
Feb-18 1.300 2.02 1.078 131 0.23 1.8
Calculated Ammonia-N
In-Stream
Concentration
Avg. 0.25
Max. 0.34
Min. 0.22

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North Carolina Wildlife Resources Commission
Gordon Myers,Executive Director
MEMORANDUM
TO: Qais Banihani,Engineer
NPDES Complex Permitting Unit
FROM: Olivia Munzer,Western Piedmont Coordinator
Habitat Conservation Division
DATE: 31 May 2018
SUBJECT: NPDES Permit Renewal for Town of Mayodan,Mayodan Wastewater Treatment Plant,
Rockingham County,NPDES Permit No.NC0021873
Biologists with the North Carolina Wildlife Resources Commission have reviewed the subject document. Our
comments are provided in accordance with provisions of the Clean Water Act of 1977(as amended),Fish and
Wildlife Coordination Act(48 Stat.401,as amended; 16 U.S.C. 661-667e),and North Carolina General Statutes
(G.S. 113-131 et seq.).
The Town of Mayodan has applied for a renewal of their NPDES permit to continue to operate an existing 4.5
MGD wastewater treatment facility. The facility has effluent limitations and monitoring requirements for 2.5,
3.0,and 4.5 MGD. Chlorine is used for disinfection,and effluent limitations for ammonia(NH3 as N)vary
depending on the discharge amount and season. The monthly average ammonia limits range from 9.0 mg/L to
31.5 mg/L. The weekly average ammonia limits range from 27.0 mg/L to 35.0 mg/L. The daily maximum for
total residual chlorine is 28 lag/L.
The wastewater treatment facility discharges to the Mayo River,a tributary to the Dan River in the Roanoke
River basin. The NCWRC have records for federal and state rare,threatened,and endangered species in the
Mayo River within the vicinity of the Mayodan WTP(see Table 1). The Mayo River State Park occurs
downstream of the Mayodan WWTP Outfall 001.
Table 1. Records of Federal and State-Listed Rare,Threatened,and Endangered Species in the Mayo River.
Common Name Scientific Name Federal Status State Status
' James Spionymussel Pleurobema collina Endangered Endangered
Roanoke Logperch Percina rex Endangered Endangered
Bigeye Jumprock Moxostoma ariommum — Threatened
Green Floater Lasmigona subviridis Species of Concern Endangered
Riverweed Darter Etheostoma podostemone — Special Concern
Roanoke Bass Ambloplites cavifrons Species of Concern Significantly Rare
Notched Rainbow Villosa constricta Species of Concern Special Concern
Mountain River Cruiser Macromia margarita Species of Concern Significantly Rare
Mailing Address: Habitat Conservation • 1721 Mail Service Center • Raleigh,NC 27699-1721
Telephone: [phone] • Fax: [phone]

Page 2
31 May 2018
Mayodan WWTP
NPDES Permit No.NC0021873
Chlorine is acutely toxic and can form secondary compounds that are detrimental to aquatic life. Valenti(2006)
concluded the impact of long term exposure to low doses of chlorine may impact juvenile mussels and reduce
the chance of them being recruited to the reproducing population. Also,fish and mussel species are very
sensitive to ammonia. Dwyer et al.(2005)found that Cape Fear shiners,a federal endangered fish species,had
an IC25 of 8.8 mg/L for ammonia. An IC25 is the level at which an organism exhibited a 25 percent reduction in
a biological measurement such as reproduction or growth after a 7-day exposure. Augspurger et al. (2003)
found that ammonia concentrations which may be protective of freshwater mussels range from 0.3 to 1.0 mg/L
total ammonia as N at pH 8.
We reviewed EPA's Enforcement and Compliance History Online(ECHO) for this facility and it showed two
effluent violations in 2015. In May and June of 2015,the total residual chlorine exceeded the daily maximum
limit by 79%.
We recognize the discharge is relatively small,and is located near the confluence of Dan River. However,the
Mayo River supports several federal and state listed species,and several listed species including the Roanoke
logperch have been documented in Dan River. Therefore, it is imperative the facility operates effectively to
prevent excessive discharge of pollutants,particularly chlorine and ammonia. Should the permit be renewed,we
offer the following recommendations to minimize impacts to aquatic resources.
1. While it appears the facility is not discharging chlorine,we encourage the applicant to consider
replacing chlorine disinfection systems with ultraviolet light or ozone systems to eliminate the potential
for chlorine to be discharged.
2. Develop site-specific acute(short-term)and chronic(long-term)water quality standards for ammonia to
protect rare and sensitive mussel species,particularly James spinymussel in the Mayo River. The site-
specific standard should be developed using the process described in Appendix A of the Technical
Support Document for Consideration of Federally-listed Threatened or Endangered Aquatic Species in
Water Quality Management Planning for the Goose Creek Watershed. Please contact Sarah McRae
with the U.S.Fish and Wildlife Service at(919) 856-4520 for additional information on developing a
site-specific standard.
Thank you for the opportunity to comment on this permit renewal. If we can be of further assistance,please
contact our office at(919)707-0364 or olivia.munzerAncwildlife.org.
Literature cited
Augspurger,T.,A.E. Keller,M. C.Black,W. G. Cope,and F.J.Dwyer. 2003. Derivation of water quality
guidance for protection of freshwater mussels(Unionidae)from ammonia exposure. Environmental
Toxicology and Chemistry 22(11):2569-2575.
Dwyer,F.J.,D.K. Hardesty,C.E. Henke,C.G. Ingersoll,D.W.Whites,T.Augspurger,T.J. Canfield,D.R.
Mount,and F.L.Mayer. 2005. Assessing Contaminant Sensitivity of Endangered and Threatened
Aquatic Species: Part III.Effluent Toxicity Tests. Archives of Environmental Contamination and
Toxicology 48:174-183.
Valenti,T.W.,D.S. Cherry,R.J. Currie,R.J.Neves,J.W.Jones,R.Mair,and C.M. Kane. 2006. Chlorine
toxicity to early life stages of freshwater mussels(Bivalvia: Unionidae). Environmental Toxicology and
Chemistry,25(9):2512-2518.
ec: TR Russ,NCWRC
Sarah McRae,U.S.Fish and Wildlife Service