NC0025721_Speculative Limits_20060310

NPDES DOCUMENT SCANNING COVER SHEET
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NPDES Permit:
NC0025721
Weldon WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Report
c
Speculative
Limits
Instream Assessment (67b)
Environmental Assessment (EA)
Permit
History
Document Date:
March 10, 2006
/114
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content on the reirerse side

Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
March 10, 2006
Mr. Kurt D. Wright, P.E.
Green Engineering, PLLC
303 N. Goldsboro Street
P.O. Box 609
Wilson, North Carolina 27893
Subject: Speculative Effluent Limits
Weldon WWTP
NPDES Permit #NC0025721
Halifax County
Dear Mr. Wright:
Alan W. Klimek, P.E. Director
Division of Water Quality
This letter is in response to your request for speculative effluent limits for a proposed expansion to 1.5 and 3.0 MGD at the
Weldon WWTP. Currently, this facility has a limit of 1.2 MGD.
Receiving Stream. This facility discharges to the Roanoke River, east of Weldon. The Roanoke River in this segment is classified
C waters. The river is listed on the draft 2006-303(d) list due to a fish consumption advisory for potential presence of mercury in
fish tissue. There are no other known water -quality concerns for this portion of the river.
Speculative Limits. The speculative limits were developed based on the Roanoke QUAL2E Model for the river from Roanoke
Rapids Dam to Hamilton. These limits are based upon current river conditions and discharge flows in this segment of the river.
Any changes in instream conditions or permitted dischargers could result in more stringent limits.
Based on available information, speculative effluent limits for the proposed discharge of 1.5 MGD to the Roanoke River are
presented in Table 1. Speculative effluent limits for the proposed discharge of 3.0 MGD to the Roanoke River are presented in
Table 2. 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. The model results do not show
any significant impact on predicted instream dissolved oxygen levels from this proposed discharge, assuming the speculative
limitations for BOD5 presented in Tables 1 and 2.
TABLE 1. Speculative Limits for Weldon WWTP, NC0025721
Effluent Characteristic
Effluent Limitations
Monthly Average
Weekly Average
Daily Maximum
Flow
1.5 MGD
BOD5
15.0 mg/1 •
22.5 mg/1
TSS
30.0 mg/1
45.0 mg/1
TRC
28 ug/1
Fecal coliform (geometric mean)
200/100 ml
400/100 ml
TABLE 2. Speculative Limits for Weldon WWTP, NC0025721
Effluent Characteristic
Effluent Limitations
Monthly; Average
Weekly Average
Daily Maximum
Flow
3.0 MGD
BOD5
15.0 mg/1
22.5 mg/1
TSS
30.0 mg/1
45.0 mg/1
TRC
28 ug/1
Fecal coliform (geometric mean)
200/100 ml
400/100 ml
Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an NPDES permit modification
for expansion to 1.5 or 3.0 MGD will be issued with these speculative limits. Final decisions can only be made after the Division
North Carolina Division of Water Quality 1617 Mail Service Center Raleigh, NC 27699-1617 Phone [phone] Customer Service
Internet: www.ncwaterqualitv.org Location: 512 N. Salisbury St. Raleigh, NC 27604 Fax [phone]
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receives and evaluates a formal permit application for the City's proposed discharge. 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 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 ate 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
Dawn Jeffries at [phone], extension 595.
Sincerely,
Gil Vinzani, P.E.
Supervisor, Eastern NPDES Program
Attachment EAA Guidance Document
cc: (without Attachment)
US Fish and Wildlife Service, Ecological Services, PO Box 33726, Raleigh, NC 27636-3726 Attn: Sara Myers
NC WRC, Inland Fisheries, 1721 Mail Service Center, Raleigh, NC, 27699-1721 Attn: Fred Harris
Raleigh Regional Office, Surface Water Protection Section
Central Files
NPDES Permit File, NC0025721

Re: Weon Spec limits
Subject: Re: Weldon Spec limits
Date: Tue, 07 Mar 2006 15:57:14 -0500
From: adugna kebede <[e-mail]>
To: Dawn Jeffries <dawn [e-mail]>
Dawn,
Yes, I run the model for 15 mg/1 BOD and the minimum flow of 1500cfs
(This flow was the minimum flow released from the Roanoke Rapids Reservoir).
The model was calibrated using the 1993-1994 Intensive Survey data. The
Headwater inputs mainly include DO and Temperature. In addition, other
parameters are needed to represent the headwater conditions. So many
input parameters are needed to run the model. If you are interested in
the model input parameters I can give you the users manual for the
model. You can come down to may office any time and I can discuss the
input parameters with you.
Thanks,
Adugna
Dawn Jeffries wrote:
>Adugna,
>Thanks again for getting back to me so quickly. Just to confirm, you
>ran the model at 15 mg/1 for BOD and no ammonia limit for both flows,
>correct? And the results reflect summer 7Q10 conditions?
>
>Also, when you wrote that some data was from 1993-1994 and headwater
>inputs were from 2005, what data is included in each group?
>Thanks much!
>Dawn
>--
>Dawn Jeffries
>Environmental Engineer
>Eastern NPDES Program
>919-733-5083, ext. 595
>919-733-0719 (FAX)
1 of 1 3/7/2006 3:58 PM

17
NC giivision of Water Quality
Planning Section
Modeling and TMDL Unit
Memorandum
March 06, 2006
To: Dawn Jeffries, Eastern NPDES Program
From: Adugna Kebede, Modeling and TMDL Unit befkitii
Subject: Weldon Speculative Limits — QUAL2E Model Simulation
NPDES Permit Number: 0025721
This is in response to your request of speculative limits for 1.5 and 3.0 MGD for a proposed
expansion of Weldon Wastewater Treatment Plant. The Roanoke QUAL2E model, which is a
low -flow, steady-state, and one-dimensional BOD model for the reach from Roanoke Rapids
Dam to Hamilton, was used to evaluate the effect of the requested expansion of Weldon WWTP
on dissolved oxygen level in the Roanoke River. The model was run for 1.5 MGD and 3.0 MGD
discharges from Weldon WWTP. Figure one shows the simulated dissolved oxygen levels for the
different scenarios. The model results indicate that a 1.5 MGD or a 3.0 MGD discharge will
impact the DO levels in the river, but will not lower the levels below 5 mg/1. Although the
model indicates that dissolved oxygen in the river would most likely meet water quality
standards, the predicted dissolved oxygen levels should be interpreted with caution. These levels
would depend on flows from other WWTPs discharging to the Roanoke River and the current
river conditions. The BOD limit may need to be lowered from the current limit of 15 mg/1 for the
proposed flow of 3.0 MGD.
The model results should be interpreted in light of the following limitations:
1. The model assumes a steady-state and one-dimensional conditions and does not simulate
flow variability. The model is calibrated to represent low flow condition (1500 cfs).
2. The model represents the portion of the river from Roanoke Rapids to Hamilton. Therefore,
the model cannot be used to determine how the proposed WWTP will impact DO
concentrations in the river below Hamilton. At this point, the river becomes tidally
1

influenced, and the steady state and one-dimensional assumptions of the QUAL2E
modeling framework no longer apply.
3. Input data from 1993-1994 intensive survey were used in the model. Only the headwater•
inputs were updated (using 2005 data). For future applications, model input parameters
may need to be updated to represent current conditions in the river.
If you have any questions please contact me at 919-733-5083 ext. 515.
cc: Michelle Woolfolk, DWQ, Modeling and TMDL Unit
2

Figure 1. Roanoke QUAL2E Model Predictions for Proposed Expansion of Weldon WWTP (1.5 MGD and 3.0 MGD )
(Roanoke River from Roanoke Rapids to Hamilton)
Figure 1. Model Predicted Dissolved Oxygen from Roanoke Rapids to Hamilton (Weldon Speculative limit request)
-Weldon at 1.5 MGD •WQ Standard -Weldon at 3.0 MGD -No Load -Current Permitted Load
Dissolved Oxygen (mg/I)
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Weldon Spec Limits
Subject: Weldon Spec Limits
Date: Mon, 17 Oct 2005 14:37:53 -0400
From: "Kurt Wright" <[e-mail]>
To: <[e-mail]>
CC: <dawn [e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>
Dawn called to inform me that the request for the Weldon Spec limits submitted to Gil Vinzani Setp. 23rd was forwarded to your
department. We requested spec limits for 4 flows in that correspondence, Dawn asked us to narrow it down to 2. Therefore, please
provide spec. limits for 1.5 and 3.0 MGD. If you should have any questions or need additional information please contact me.
Thanks,
Kurt Wright, PE
Green Engineering
P. O. Box 609
Wilson, NC 27893
252.237.5365
fax [phone]
Pjltr.gvinzani.9-23-05.pdf
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1 of 1
3/8/2006 7:55 AM

GREEN
ENGINE•E
'AIN
Mr. Gil Vinzani, P.E.
Supervisor, Eastern NPDES Program
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Ref: Speculative Effluent Limits
Proposed WWTP Expansion
Town of Weldon, North Carolina
PN 05-039
Dear Gil:
September 23, 2005
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On behalf of the Town of Weldon we respectfully request the speculative effluent
limits for a proposed expansion of the Weldon Wastewater Treatment Plant, NPDES
Permit Number 0025721. Please provide speculative effluent limits for flows of 1.5, 2.0,
2.5 and 3.0 MGD. Z l
If you should have any questions regarding the above please do not hesitate to
contact me.
Very Truly Yours,
l/t/AA-/i7f-
Kurt D. Wright, P.E.
KDW/pbg
cc: Mr. Donald Crowder — Town of Weldon
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GREEN ENGINEERING, PLLC
WATER. VJASTEWATER SURVEYING, PLANNING. PROJECT MANAGEMENT
303 N. GOLOSBORO ST. PO 00X 609 WILSON N.C. 27893 TEL [phone] FAX [phone] WWW.GRE ENENGIN E ERING.COM

NC0025721
Facility: Weldon WWTP
Discharge to: Roanoke River
Stream class and index #: C
Residual Chlorine
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (UG/L)
UPS BACKGROUND LEVEL (UG/L)
IWC (%)
Allowable Conc.
Fecal Limit
Ratio of 236.6 :1
maximum=28 ug/I
1100
3
4.65
17.0
0
0.42
038.51
Ammonia as NH3
(summer)
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL (MG/L)
IWC (%)
Allowable Concentration (mg/I)
Ammonia as NH3
(winter)
7Q10 (CFS)
2001100m1 DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL (MG/L)
IWC (%)
Allowable Concentration (mg/I)
1100
3
4.65
1.0
0.22
0.42
185.52
minimum =
Kt 0 e
etaded
1100
1.8
2.79
1.8
0.22
624.74
minimum = 4
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