NC0004464_Draft Permit_180808

A/cooae/96 9
NPDES Permitting for Mercury
Implementation of 2012 Statewide Mercury TMDL
Facility Type Annual Average Monitoring Frequency MMP Required(see B)
Limit Required(see A) (with 1631E analysis)
Major Muni (>1 MGD) Yes Quarterly Yes(if>2 MGD)
No 3 PPA only Yes-if multiple detects
above 1 ng/1 and>2
( MGD
ivlinor Muni(<1 MGD Y Quart No
l
1
Once/5 years No
Industrial Yes Quarterly Yes
No None in permit.Might No
be required for EPA
application form.
A.Procedure to Determine if Annual Average Limit Required:
Step 1-WQBEL Evaluation
• Evaluate need for Water Quality Based Effluent Limit(WQBEL)
• Calculate Allowable mercury concentration using dilution(12 ng/1 x 7Q10 dilution factor)
• Compare Annual effluent concentrations to Allowable Conc.for each of last 5 years
• If any Annual Avg>Allowable Conc.,then add Annual Avg WQBEL.
Step 2-TBEL Evaluation
• Evaluate need for Technology Based Effluent Limit(TBEL)
• Compare all individual values to TBEL of 47 ng/1
• If any single value>47 ng/l,then add Annual Avg TBEL of 47 ng/1.
Step 3-Compare WQBEL to TBEL
• If data triggers need for WQBEL and TBEL,select most stringent of the two limits.
• If data triggers need for only TBEL,add 47 ng/1 annual average limit unless WQBEL<47 ng/1,in which
case annual avg limit should be set at WQBEL.
• Conclusion:the Annual Avg limit will range from 12 ng/1 to upper cap of 47 ng/l.
Step 4-If NEW limit,delay effective date
• Addition of new limit will become effective in 5th year of permit,with mercury minimization plan
development/implementation required for first 4 years(see MMP below).
B.Mercury Minimization Plan(MMP). If an MMP is required,add the following Special Condition to the
permit:
A(x). P. ercury Mirliamazation Plan(MMP). The perp ittec shall develop and ilimpleme ft a mere:f,, uminivxaizetion
plan during this permit team. The MMP shall be developed within I El m.ys of the NPDES Permit Effective Date,
and shall be available for inspectio4.on-site. A sample I 1 .r["was developed t`frxough a stakeholder review process
and has been placed on the Divisioffi website for r' idauce(latt�J/n.vr l.ncdea ,or�/web/w /s slatks,under
Model Mercury Mim,indzation Pa I). The MhW should place emphasis on identification of mercury cont.=,luattors and
goals for reduction. Results shall be summarized and submitted with the next permit renewal. Performance of the
^,'ercury Minimizatiox Plan will meet the requirements of the TMDL(Total Maximum Daily Load)for mercury
approved by USEP.=, in October 12,2012,unless and maxi; a'.4 este p..+uo Allocati•a specific to..tis facility is
developed and Isis '"DES permit is amended to require further actiias to address the Waste Load Ili cation.
C.New/Expanding Dischargers-will be allowed as long as the overall aggregate point source load allocation is not
exceeded.
D.Special Situations-Additional site-specific information,such as fish tissue and water column data when
available,will be considered in assigning limits and MMP requirements. Also,limits>TBEL may be considered on
case-by-case basis due to extenuating circumstances
Version 01/12/2015 Prepared by:Tom Belnick Approved by Jeff Poupart