NC0024937_speculative limits_20060621

Michael F. Easley, Governor
State of North Carolina
William G. Ross, Jr., Secretary
Department of Environment and Natural Resources
Alan W. Klimek, P.E., Director
Division of Water Quality
June 21, 2006
Mrs. Jacqueline Jarrell, P.E.
Engineering Division
Charlotte Mecklenburg Utilities
5100 Brookshire Boulevard
Charlotte, North Carolina 28269
Subject: Speculative Effluent Limits
Sugar Creek WWMF - NC0024937
Irwin Creek WWMF - NC 0024945
McAlpine Creek WWMF - NC0024970
Mecklenburg County
Dear Mrs. Jarrell:
This letter is in response to your request for speculative effluent limits for a proposed combined
expansion to 144 MGD at three CMUD wastewater treatment plants. Since a decision has not yet
been made regarding the specific expansions at each WWMF, speculative limits are hereby provided
for the "worst case scenario" as defined in the QUAL2E model. Those flows are for 25 MGD at the
Irwin Creek WWMF, 35 MGD at the Sugar Creek WWMF, and 90 MGD at the McAlpine Creek
WWMF for a total of 150 MGD.
Receiving Stream. Sugar Creek, Irwin Creek, and McAlpine Creek are all tributaries of the Catawba
River. Downstream waterbodies in the South Carolina portion of the Catawba River Basin are listed
as impaired for total phosphorus (TP). Currently a model is being developed to support a nutrient
TMDL for the lower Catawba River Basin.
Speculative Limits. These speculative limits were developed based on our review of the Sugar
Creek Watershed QUAL2E model prepared by CH2M Hill (updated November 4, 2005). This model
evaluated the assimilative capacity of oxygen consuming wastes for the watershed under a "worst
case scenario" expansion to 150 MGD from all three CMUD facilities. The model varied from a
previous rendition in that it was extended to the confluence of Sugar Creek and the Catawba River
in order allow for any potential D.O. sags in the system. It also evaluated an option using current
rate coefficients typical of highly treated discharges.
Based on available information, speculative effluent limits for the proposed combined discharge of
150 MGD to Sugar Creek, Irwin Creek, and McAlpine Creek are presented in Table 1. A complete
evaluation of these limits and monitoring frequencies in addition to monitoring requirements for
metals and other toxicants will be addressed upon receipt of a formal NPDES permit modification
request. In addition, a TP limit is contingent upon the results of the nutrient TMDL for the Lower
Catawba River Watershed.
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone [phone] FAX [phone]
512 N. Salisbury Street, Raleigh, North Carolina 27604 On the Internet at http://h2o.enr.state.nc.us/
An Equal Opportunity/Affirmative Action Employer
Nye Carolina
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CMUD Speculative Effluent Limits
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TABLE 1. Speculative Limits for CMUD Facilities
Effluent
Characteristics
Ire Creek
Sugar Creek
1VIcAlpine Creek
Mtn + Avg.
Weekly Avg.
Monthly Avg.
Weekly Avg.
Monthly Avg.
Weekly Avg.
Flow (MGD)
25 MGD
35 MGD
90 MGD
CBODs
(Apr 1- Oct 31)
5.0 mg/L
7.5 mg/L
5.0 mg/L
7.5 mg/L
4.0 mg/L
6.0 mg/L
CBODs
(Nov 1- Mar 31)
10.0 mg/L
15.0 mg/L
10.0 mg/L
15.0 mg/L
8.0 mg/L
12.0 mg/L
TSS
30.0 mg/L
45.0 mg/L
30.0 mg/L
45.0 mg/L
15.0 mg/L
22.5 mg/L
NH3 as N
(Apr 1- Oct 31)
1.2 mg/L
3.6 mg/L
1.0 mg/L
3.0 mg/L
1.0 mg/L
3.0 mg/L
as N
(Apr 1- Oct 31)
2.3 mg/L
6.9 mg/L
2.0 mg/L
6.0 mg/L
1.9 mg/L
5.7 mg/L
Dissolved Oxygen
Fecal Coliform s
(geometric mean)
200/100 mL
400/100 mL
200/100 mL
400/100 mL
200/100 mL
400/100 mL
pH
Between 6.0 and 9.0 s.u.
Between 6.0 and 9.0 s.u.
Between 6.0 and 9.0 s.u.
TRC1
19 pg/L
18 .ig/L
17 pg/L
Chronic Toxicity
(effluent concentration)
89%
90 /0
°
90 /o
Notes:
1. The daily average limit for total residual chlorine shall be 28 ig/L.
2. The daily average dissolved oxygen effluent concentrations shall not be less than 6.0 mg/L.
3. The daily maximum limit for fecal coliform shall be 1000/100mL.
Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that
NPDES permit modifications for expansion will be issued with these speculative limits. Final
decisions can only be made after the Division receives and evaluates formal permit applications for.
the proposed discharges. In accordance with the North Carolina General Statutes, the practicable
wastewater treatment and disposal alternative with the least adverse impact on the environment is
required to be implemented. Therefore, as a component of all NPDES permit applications for new
or expanding flow, a detailed engineering alternatives analysis (EAA) must be prepared. The EAA
must justify requested flows and provide an analysis of potential wastewater treatment alternatives.
Alternatives to a surface water . discharge, such as spray/drip irrigation, wastewater reuse, or
inflow/infiltration reduction, are considered to be environmentally preferable. A copy of the EAA
requirements is attached to this letter. Permit applications for new or expanding flow will be
returned as incomplete if all EAA requirements are not adequately addressed. If you have any
questions regarding these requirements, please contact the DWQ NPDES Unit at 919-733-5083.
State Environmental Policy Act (SEPA) EA/EIS Requirements. A SEPA EA/EIS document must be
prepared for all projects that 1) need a permit; 2) use public money or affect public lands; and 3)
might have a potential to significantly impact the environment. For new wastewater discharges,
significant impact is defined as a proposed discharge of >500,000 gpd and producing an instream
waste concentration of > 33% based on summer 7Q10 flow conditions. For existing discharges,
significant impact is defined as an expansion of > 500,000 gpd additional flow. Since your existing
facility is proposing an expansion of >500,000 gpd additional flow, you must prepare a SEPA
document that evaluates the potential for impacting the quality of the environment. The NPDES
Unit will not accept an NPDES permit application for the proposed expansion until the Division
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CMUD Speculative Effluent Limits
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has approved the SEPA document and sent a Finding of No Significant Impact (FONSI) to the
State Clearinghouse for review and comment. A SEPA Environmental Assessment (EA) should
contain a clear justification for the proposed project. If the SEPA EA demonstrates that the project
may result in a significant adverse effect on the quality of the environment, you must then prepare a
SEPA EIS (Environmental Impact Statement). Since your proposed expansion is subject to SEPA,
the EAA requirements discussed above will need to be folded into the SEPA document. The
SEPA process will be delayed if all EAA requirements are not adequately addressed. If you have
any questions regarding SEPA EA/EIS requirements, please contact Alex Marks with the DWQ
Planning Branch at [phone], ext. 555.
Should you have any questions about these speculative limits or NPDES permitting requirements,
please feel free to contact Toya Fields at [phone], extension 551.
Sincerely,
Susan A. Wilson, P.E.
Supervisor, NPDES Unit
Attachment: EAA Guidance Document
Cc: (with attachment)
Bill Kreutzberger, CH2M Hill, 4824 Parkway Plaza Blvd, Suite 200, Charlotte, NC 28217
cc: (without Attachment)
Sara Myers, US Fish & Wildlife Service, Ecological Services, PO Box 33726, Raleigh, NC 27636
Fred Harris , NC WRC, Inland Fisheries, 1721 Mail Service Center, Raleigh, NC, 27699
Mooresville Regional Office, Surface Water Protection
Central Files
NPDES Permit Files (NC0024937q NC0024945, NC0024970)
Marshall Hyatt, EPA Region IV
Jeff deBessonet, South Carolina DHEC, 2600 Bull Street Columbia, S.C. 29201
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