NC0046728_Speculative Limits_20060628

NPDES DOCUMENT SCANNIN` COVER SNEET
NC0046728
Mooresville / Rocky River WWTP
NPDES Permit:
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Plan of Action
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Permit
History
Document Date:
June 28, 2006
This document is printed on reuse paper - ignore nay
content on the reYerse side

Mr. Wike Martin
Utilities Director, Town of Mooresville
P.O. Box 878
Mooresville, North Carolina 28115
Michael F. Easley, Govemor
State of North Carolina
William G. Ross, 3r., Secretary
Department of Environment and Natural Resources
Alan W. Klimek, P.E., Director
Division of Water Quality
June 28, 2006
Subject: Speculative Effluent Limits
Rocky River WWTP
NPDES Permit #NC0046728
Iredell County
Dear Mr. Martin:
This letter is in response to your request for information regarding additional data, modeling analysis,
and/or other information that would be required for the issuance of speculative limits. The exact
discharge scenario is undetermined at this time, however there may be a potential discharge of 14-17
MGD to Lake Norman with a discharge of up to 9.54 MGD to Dye Branch. The Rocky River WWTP is
currently permitted to discharge 5.2 MGD to Dye Branch.
Lake Norman Discharge
There are two proposed discharge locations for Lake Norman. Option A would discharge treated
effluent at the NC HWY 150 Bridge, while Option B would discharge treated effluent into a cove near the
Pier 33 Road. To evaluate a speculative limits request to discharge into Lake Norman at either location,
DWQ would require a highly detailed, calibrated nutrient response model for the lake to demonstrate
assimilative capacity, as mentioned in the Catawba Basinwide Plan. The model would need to be able to
show any associated localized impacts and behavior of the lake during critical conditions.
Duke Power has developed a modified CE-QUAL-W2 model for the lake. DWQ recommends that CH2M
HILL request to use the input files and code from this model. In the event that Duke allows the code to
be made public, the model would need to be calibrated for nutrients. The model will also need to
incorporate all existing NPDES discharges in the Lake Norman watershed to fully evaluate assimilative
capacity. If CH2M HILL is not able to acquire this model from Duke Power, a model of similar spatial
scope (i.e. the entire lake from Lookout Shoals Dam down to Cowans Ford Dam) and complexity should
be developed. Again, the model should predict dissolved oxygen impacts as well as the nutrient
response of the Lake.
For discharge Option A, the Duke Power Marshall Steam Station is located in the general vicinity of the
proposed discharge and has an impact on water temperature. This effect also needs to be included in the
nutrient response model. For discharge Option B, there is an existing minor WWTP in this general
location. Diamond Head WWTP is currently permitted to discharge 0.1 MGD. A map of the nearby
dischargers is attached.
Dye Branch Discharge
For an increased discharge to Dye Branch, which is currently listed as having a biological impairment,
DWQ would require a hydraulics and sediment transport model to evaluate whether the increased flow
would have a detrimental impact on Dye Branch.
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 OpportunitylAffirmative Action Employer
No`" Caturro na
n

Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an NPDES
permit modification for expansion will be issued. Final decisions can only be made after the Division
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 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.
t�
Attachment: EAA Guidance Document
Sincerely,
Susan A. Wilson, P.E.
Supervisor, Western NPDES Program
cc: (with attachment)
William A. Kreutzberger Water Resources Manager, CH2M Hill
4824 Parkway Plaza Boulevard
Suite 200
Charlotte, North Carolina 28217
cc: (without Attachment)
Sara Myers, US Fish and Wildlife Service, Ecological Services, PO Box 33726, Raleigh, NC 27636
Fred Harris, NC WRC, Inland Fisheries, 1721 Mail Service Center, Raleigh, NC, 27699-1721
Mooresville Regional Office
Central Files
NPDES Permit File
2

'if
Lake Norman
Mooresville WWTP Discharge Options
Ams20041027.shp
Updesminor092403.shp
Usgs_nc.shp
A t1pdesmajor092403_cam.shp
'Dotprimrds.shp
Streams.shp
N1ajor_hydrography polys.shp
4&
' `V31 t
Discharge option A
@ HWY 150 Bridge
Permit NC0004987
Marshall Steam Sta.
Duke Energy Corp
�l
•
t " +L w.,, , ram, N41,
40.
x
Permit NC0074772
"14-
Diamond Head WWTP
Discharge Option B
@ Pier 33 Road
1
3
t
1

Re: Mooresville model
IBC oc'1(o `?)-F
Subject: Re: Mooresville model
From: Pamela Behm <[e-mail]>
Date: Fri, 16 Jun 2006 11:29:29 -0400
To: Toya Fields <[e-mail]>, Susan Wilson <[e-mail]>, michelle
woolfolk <[e-mail]>
Attached is the memo in response to the Mooresville request. Thanks.
Pam
Toya Fields wrote:
Hey Pam,
I just wanted to send an email to check on the status of the Mooresville model. I
think you gave me a call a few weeks ago to say you'd finished and just needed to
draft the memo.
Thanks,
Toya
Pam Behm <[e-mail]>
NC DENR Division of Water Quality
Modeling and TMDL Unit
Mooresville spec limit request.doc
Content -Encoding: base64
Content -Type: application/msword
1 of 1 6/19/2006 9:04 AM

NC Division of Water Quality
Planning Section — Modeling & TMDL Unit
Technical Memorandum
May 22, 2006
TO: Michelle Woolfolk, Modeling & TMDL Unit
CC: Susan Wilson, NPDES Unit
FROM: Pam Behm, Modeling & TMDL Unit
RE: CH2M HILL Information request for potential expansion of Mooresville WWTP
This memorandum is in response to "Additional Speculative Limits Request for Expansion of
Mooresville WWTP NPDES No. NC0046728," received by the Modeling & TMDL Unit on
February 27, 2006 from CH2M HILL. The request is for information from DWQ regarding
additional data, modeling analysis or other information that will be required for the issuance of
speculative limits.
Mooresville WWTP is currently permitted to discharge 5.2 MGD to Dye Branch. The request is
to discharge 14 MGD —17 MGD to Lake Norman and up to a maximum of 9.54 MGD to Dye
Branch.
Lake Norman Discharge
There are two proposed discharge locations for Lake Norman (see attached figure). Discharge
Option A would discharge treated effluent at the NC HWY 150 Bridge, while Discharge Option
B at Pier 33 Road would discharge treated effluent into a cove. Both of these options require the
analysis of nutrient related impacts using a DWQ-approved nutrient response model for the
receiving reservoir as per the Catawba Basinwide Plan
(http://h2o.enr.state.nc.us/basinwide/Draft2004CatawbaRiverBasinWaterQualityPlan.htm).
To evaluate a speculative limits request to discharge into Lake Norman at either location, DWQ
would require a highly detailed, calibrated nutrient response model for the lake to demonstrate
assimilative capacity. The model would need to be able to show any associated localized
impacts and behavior of the lake during critical conditions.
Duke Power has developed a modified CE-QUAL-W2 model for the lake. DWQ recommends
that CH2M HILL request to use the input files and code from this model. The model would need
to be calibrated for nutrients because the objective of the model for Duke Power was not to
model nutrients. The model will also need to incorporate all existing NPDES discharges in the
Lake Norman watershed to fully evaluate assimilative capacity.
1

Duke Power made some modifications to the model code for CE-QUAL-W2. In order for
CH2M HILL to use this model, Duke Power would need to make the code modifications
publicly available. If CH2M HILL is not able to acquire this model from Duke Power, a model
of similar spatial scope (i.e. the entire lake from Lookout Shoals Dam down to Cowans Ford
Dam) and complexity should be developed.
For Discharge Option A, the Duke Power Marshall Steam Station is located in the general
vicinity of the proposed discharge and does impact water temperature. This effect needs to be
included in the nutrient response model.
It should be noted that for Discharge Option B, there is an existing minor WWTP in this general
location. Diamond Head WWTP is currently permitted to discharge 0.1 MGD.
Dye Branch Discharge
Dye Branch is impaired (biological). For the potential request for increased discharge to Dye
Branch (from 5.2 MGD to a maximum of 9.54 MGD), DWQ would require a hydraulics and
sediment transport model to evaluate if the increased flow would have a detrimental impact on
Dye Branch.
2

Lake Norman
Mooresville WWTP Discharge Options
0 Ams20041027.shp
Npdesminor092403.shp
0 Usgs_nc.shp
Updesmajor092403_cam.shp
Dotprimrds.shp
Streams.shp
Major_hydrography_polys.shp
tL
Discharge Option A
@ HWY 150 Bridge
Permit NC0004987
Marshall Steam Sta.
Duke Energy Corp
1
4 f'T'C•
A
A
JJL
Permit NC0074772
Diamond Head WWTP
Discharge Option B
@ Pier 33 Road**
** Apparently, Pier 33 Road is near Williamson Road, I was not able to find Pier 33 Road on DWQ's GIS
secondary road coverage, although according to Google Earth, there is a Pier 33 Drive nearby. This needs to be
clarified.
3

CH2MHILL.
February 22, 2006
Ms. Susan Wilson
Supervisor, Western NPDES Program
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
_
F E B 2 7 2006
CH2M HILL
4824 Parkway Plaza Boulevard
Suite 200
Charlotte, NC 28217
Tel [phone]
Fax [phone]
Subject: Additional Speculative Limits Request for Expansion of Mooresville WWTP
NPDES No. NC0046728
Dear Ms. Wilson:
Based on our meeting on February 7, 2006, I am writing to request additional speculative limits
for a discharge from an expansion of the capacity of the Mooresville WWTP from 5.2 mgd to 19
mgd by 2025. We previously requested that all of this expansion be permitted for discharge at
the current discharge point to Dye Branch in correspondence dated November 11, 2005. Based
on potential interbasin transfer issues, we also need speculative limits for discharge to Lake
Norman, in the Catawba River Basin. While the capacity of the expansion of the wastewater
treatment facility will still be 19 mgd, the required discharge amount to the Lake Norman will
be 17 mgd if there is no increase in permitted discharge to Dye Branch or up to 14 mgd if
increased discharge is allowed to Dye branch but no increase in the grandfathered IBT of 9.54
mgd is permitted by the Environmental Management Commission. The discharge amounts do
not add up to the treatment capacity because of the nuances of the IBT requirements such as
maximum day transfer amounts and that wastewater capacities are influenced by wet weather
flows, as discussed at our meeting.
We have identified two potential discharge locations for a discharge to Lake Norman as shown
in the attached figure. Discharge option B is is the closest route to the lake and would
discharge treated effluent into a cove. Discharge Option A would discharge treated effluent at
the NC HWY 150 Bridge which would allow for discharge into a deeper portion of the lake
near the old Catawba River channel.
We recognize that DWQ may not have the time or resources to develop tools and conduct
necessary analyses to support the development of speculative limits for a Lake Norman
discharge. For that reason, we are requesting information back from DWQ regarding
additional data, modeling analysis or other information that will be required for the issuance of
speculative limits.
As we discussed at our meeting, the recent master planning effort for Mooresville has shown
that the need for expansion of their treatment capacity is quite urgent. Therefore, we need to
proceed with efforts to evaluate speculative limits as soon as possible. If you have any

Ms. Susan Wilson
Page 2
February 22, 2006
questions, or would like to discuss this request further, please contact Ruth Swanek at 875-
4311, extension 16 or me at [phone], ext. 217. Thank you for your help in this matter.
Sincerely,
CH2M HILL
/rzer,
William A. Kreutzberger
Water Resources Manager
CC: Jamie Justice, Town of Mooresville
Michelle Woolfolk, DWQ Modeling and TMDL Unit
Toya Fields/DWQ NPDES West
Tom Fransen/DWR
Mike Osborne, PE, CH2M HILL
Ruth Swanek, CH2M HILL

Discharge Option A
@ HWY 150 Bridge
Discharge Option B @
Pier 33 Road
Lake Norman
Legend
Watershed Boundary
Transmission Line
Major Road
Interstate Highway
I Major Hydrography
® Rocky River WWTP
Rocky River WWTP
N
v. CH2IVIHILL 1.25 0.625 0 1.25 Miles
A
Lake Norman Discharge
Town of Mooresville
Iredell County, NC