NC0021644_Approval_20180522

ROY COOPER
IIIC
Governor
MICHAEL S. REGAN
Secretary
Water Resources ' LINDA CULPEPPER
Environmental Quality Interim Director
May 22,2018
CERTIFIED MAIL 7016 2140 0000 4371 1261
RETURN RECEIPT REQUESTED
Mr.John Craft,Town Manager
Town of La Grange
PO Box 368
La Grange,NC 28551
Subject: Request for Additional Information
Renewal Application '
La Grange WWTP
NPDES permit NC0021644
Lenoir County
Dear Mr. Craft:
The Division has reviewed your application,received on August 9, 2017, for renewal of NPDES permit
NC0026411.To enable us complete our review in accordance with N.C.G.S. 143-215.1 and 15A NCAC
21.0105,please provide additional or revised information to address the following comments:
• Please provide five(5) days of Total Hardness(CaCO3 or(Ca+Mg))data for the effluent and
upstream of Outfall 001.
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 permit renewal is Zinc.
To evaluate dissolved Zinc,a Reasonable Potential Analysis(RPA)was conducted using data reported on
DMRs from November 2015 to March 2018.Results indicated a reasonable potential to exceed both the
Acute and Chronic allowable concentrations for Zinc, 125.7 µg/L and 126.7 µg/L,repectively.The Acute
value is typically used as the daily maximum limit and Chronic value is typically used as the monthly
average limit.However,the Chronic value for Zinc is less stringent.The monthly average limit must be
more stringent or equal to the daily maxium limit. Therefore,the daily maximum limit and monthly
average limit for Zinc will be the Acute value as follows: ,
State of North Carolina I Environmental Quality
1617 Mail Service Center I Raleigh,North Carolina 27699-1617
919-707-9000

Mr. Craft
May 22, 2018
Page 2 of 2
Parameter Outfall Monthly Average Limit Daily Maximum Limit
Zinc 001 125.7 µg/L 125.7 µg/L
To calculate these limits a default hardness of 25 mg/L was entered for both the effluent and upstream
values.The additional information requested for Total Hardness will be used in a recalculation of Zinc
limits 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 requested information. Therefore, a default hardness of 25 mg/L 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.denardAncdenr.gov.
Sincere y,
Linda Culpepper,Interim Dir cto'
Division of Water Resources,NCDEQ
hc: Central Files
NPDES Program Files
WaRO Files