NC0024945_Speculative Limits_20060621

NPDES DOCUHENT !MCANNIN`: COVER SHEET
NC0024945
Irwin Creek WWTP
NPDES Permit:
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Draft Permit
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
June 21, 2006
This document is printed on reuse paper - ixnore any
content on the imam erse aside

Michael F. Easley, Govemor
):.. .i"1 .. 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
*Log ina

CMUD Speculative Effluent Limits
Page 2
TABLE 1. Speculative Limits for CMUD Facilities
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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
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
NH3N
(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.
TRC'
19 pg/L
18 pg/L
17 pg/L
Chronic Toxicity
(effluent concentration)
89%
90%
90%
Notes:
1. The daily average limit for total residual chlorine shall be 28 pg/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
2

CMUD Speculative Effluent Limits
Page 3
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 (NC0024937, NC0024945, NC0024970)
Marshall Hyatt, EPA Region IV
Jeff deBessonet, South Carolina DHEC, 2600 Bull Street Columbia, S.C. 29201
3

CMU and DWQ Discussion of Assimilative
Capacity Issues in the Sugar Creek Watershed
September 6, 2005 -1 to 2 PM
Agenda
Call -in Number-866-836-0844
Participant Code - 855089
Host Code (Bill) -124603
1. Introductions and purpose of the call
2. Background on request for speculative limits
- Previous flow projections and 2003 request for speculative limits
— On -going planning study — flow projections and alternatives analysis
3. Review of TM 1 on Assimilative Capacity Issues
- Watershed and WWMF overview
— Current water quality assessment information
- Review of 1993 QUAL2E Model for the Sugar Creek watershed
- Review of available DO data
- Need for additional assimilative capacity models
4. Discussion and Next Steps
5. Action items
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960
AUG 2 9 2005
Dawn K. Padgett
Technical Services
Environmental Management Division
Charlotte Mecklenburg Utilities
4000 Westmont Drive
Charlotte, NC 28217
Subject: Water -Effect Ratio Review
Charlotte -Mecklenburg Utility/Irwin Creek Permit No. NC0024945
Charlotte -Mecklenburg Utility/Sugar Creek Permit No. NC0024937
Charlotte -Mecklenburg Utility/McAlpine Permit No. NC0024970
Dear Ms. Padgett:
On July 26, 2005, the enclosed email was forwarded to the U.S. Environmental
Protection Agency (EPA) requesting a review of proposed procedures for developing a
water effect ratio (WER) for copper at the Charlotte Mecklenburg Utilities (CMU) listed
above.
The WER procedure was reviewed using the Interim Guidance on Determination
and Use of Water -Effect Ratios for Metals (EPA-823-B-94-00, February 1994) and the
Streamlined Water -Effect Ratio Procedure for Discharges of Copper (EPA-822-R-01-
005, March 2001) as a reference. In addition, the data reported on the facilities Discharge
Monitoring Reports (DMRs) under its National Pollutant Discharge Elimination System
(NPDES) permit was also reviewed through EPA's Permit Compliance System tracking
database.
As verified with you by phone on August 24, 2005, with Lisa Perras Gordon of
my staff, each of the above facilities has remained at or well below the permitted limits
for copper for over four years. Please be aware that the Interim Guidance indicates that
the "smallest desired WER" should be determined when making the decision to proceed
with a WER (pg. 44). The "smallest desired WER" would be that value which would not
require a reduction in the amount of metal being discharged. In this case, that value may
be at or below the existing permit limits.
If CMU makes the determination to proceed with the WER, EPA recommends the
following revisions to the submitted procedure:
• Paragraph 2, page 1: Plant performance at the time of sampling should
also include the provision that carbonaceous biochemical oxygen demand
Internet Address (URL) • http://www.epa.gov
Recycled/Recyclable • Printed with Vegetable OO Based Inks on Recycled Paper (Minimum 30% Postconsumer)

(CBOD) and suspended solids be within permit limits since the WER is
sensitive to the concentration of organic matter discharged.
• Final paragraph, page 2: Clarify the calculation of the sample WER. To
follow the calculation as set out in the Guidance, it should include the
following:
Sample WER is the lesser of:
1. Site Water EC50 divided by the lab water EC50, or
2. Site Water EC50 divided by the Species Mean Acute Value
(SMAV) (Appendix B of the Guidance document).
The Final Site WER is the geometric mean of the two sample
WERs.
As discussed with Ms. Gordon, CMU has indicated it will follow all of the
procedures outlined in the Streamlined Guidance and the Interim Guidance in conducting
the WER. Section H of Appendix A of the Streamlined Guidance outlines in detail the
information required to be submitted to the regulatory agencies once the WER is
complete. Following these guidelines should ensure an efficient review of the WER once
it is submitted. If you should have any additional questions, please do not hesitate to
contact Ms. Gordon of my staff at [phone].
Sincerely,
Annie Godfrey, Acting Chief
East Standards, Monitoring and TMDL Section
Enclosure
cc: Connie Brower, NC DWQ
kie Nowell, NC DWQ
Marshall Hyatt, US EPA

Lisa -Perms
Gordon/R4/USEPA/US
08/24/2005 12:08 PM
To
cc
bcc
Subject Fw: Water Effects Ratio Procedure
Forwarded by Marshall Hyatt/R4/USEPA/US on 07/26/2005 02:18 PM ----
"Padgett, Dawn"
<[e-mail] To Marshall Hyatt/R4/USEPA/US@EPA
cc "Jarrell, Jackie" <[e-mail]>, Frank Pasztor
07/26/2005 01:58 PM <[e-mail]>
Subject Water Effects Ratio Procedure
Mr. Hyatt, The NC DENR-DWQ section has asked me to send you a copy of the procedure we have
developed to determine the specific values for a Water Effects Ratio. Attached is our proposed
procedure. This procedure has been approved by the NC Aquatic Toxicology Section of DWQ and will be
completed by a NC Certified Lab - Meritech, Inc. I understand that you wished to review this procedure to
make sure we are completing the procedure as required. Please let me know if there are any problems or
if you have any questions.
If you need to contact the lab we will be using the complete this procedure, my contact at Meritech, Inc. is
Frank Pasztor and his e-mail address is [e-mail] «Water Effects Ratio
Procedure-Final.doc» . If you need to call him the lab phone number is 336/342-4748.
Please let me know about any issues you may find. Thank you for taking the time to review this proceudre
for us.
Sincerely,
Dawn K. Padgett
Technical Services
Environmental Management Division
Charlotte Mecklenburg Utilities
4000 Westmont Dr.
Charlotte, NC 28217
Phone - 704/357-1344, ext. 235
Fax - 704/423-9151
E-mail address - [e-mail] Water Effects Ratio Procedure•Final.doc

Water Effects Ratio (WER)
The procedure is used to determine site specific values for a Water Effect Ratio for
Copper from continuous point source effluents, being discharged in elevated
concentrations.
Sampling
Stream flow data and rainfall data for preceding two week period is obtained at the time
of sampling. The study will involve two sampling events spaced at least one month apart.
At the time of sampling stream flow should be stable with no significant affect of rainfall
or runoff. Effluent samples are collected during the same time and under normal plant
operational conditions.
A 24 hr. composite effluent sample and an upstream receiving water grab sample are
collected for each of the sampling events. Samples will be shipped and stored at 0-4°C.
Parameters are to be measured consistent with standard NPDES requirements as well as
those associated with whole effluent toxicity (WET) testing. (Prior to combining the
samples, the upstream water will be filtered through a 37-60 µm sieve or screen to
remove any predators that may be present.) The effluent and upstream sample are
combined at the design flow condition used in the permit limit calculations, to create a
simulated downstream sample, called the site -water sample. Site -water samples have the
following instream waste concentration (IWC):
Summary of Design Instream Waste Concentrations
Facility
Design Flow
7Q10 Flow
IWC
Irwin Creek
15 MGD
4.9 cfs
82.6 %
Sugar Creek
20 MGD
3.4 cfs
90.1 %
McAlpine
64 MGD
2.0 cfs
98.0 %
The site -water sample will be used in the toxicity testing spiked with a minimum of five
sequential nominal concentrations of total copper within the range set forth in the chart as
well as an un-spiked control. Testing will be initiated within 96 hr of sampling. Side by
side tests with laboratory water will also be initiated. A 48 hr static renewal acute WET
test will be conducted using Ceriodaphnia Dubia as the test organism. Each test, site -
water and laboratory control water, is setup unspiked and at a minimum of five sequential
concentrations spiked with copper nitrate. A dilution factor of 0.6 will be used to setup
the test. The adjusted hardness for our laboratory water varies from 44-48 mg CaCO3, as
such the following nominal copper concentrations will be used. These concentrations will
be modified if the site water has a hardness outside the range of the lab water.

Sample WER = Sample Water EC50/Laboratory Water EC50.
*ECM values will be normalized to the same hardness using the following formula:
EC5Oat Std Hdns = EC5Oat Sample Hdns * (Std Hdns/Sample Hdns)°9422.

metals limits proposed irw-sug2.xls
Subject: metals limits proposed irw-sug2.xls
From: Jackie Nowell <[e-mail]>
Date: Wed, 24 Aug 2005 17:43:30 -0400
To: "[e-mail]" <[e-mail]>
Hello Marshall,
Here is the excel file of CMUs calculations for the Irwin and Sugar Creek plants in
addition to the explanation of how they were derived. I am not familiar with the
"Texas Method" so I can't say whether that is what they used. From what I recall
they were water quality based effluent limits calculations that factored in TSS
partitioning coefficients. Letters with additional info can be faxed to you if
needed.
Items #2 and #3 - Matt Matthews of Aquatic Tox is going to call you about your WET
test questions.
Item #4 -We think that CMU is looking for some relief from the Cu and Zn limits that
they have. They may be thinking that the WER may result in limits that could be
higher. We did explain to them that if study shows limits should be more stringent,
they would have to accept them.
Please contact me if more questions.
metals limits proposed irw-sug2.xls
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1 of 1 8/24/2005 5:48 PM

re WERs for Irwin, Sugar, McAlpine WWTPs
Subject: re WERs for Irwin, Sugar, McAlpine WWTPs
From: [e-mail]
Date: Tue, 23 Aug 2005 10:47:33 -0400
To: [e-mail]
CC: [e-mail], [e-mail]
Lisa Gordon and I are still evaluating CMUD's proposed WER study. We
have several questions that we need your help for. If you answer for
Irwin Creek, that will be good enough for the other facilities. if it's
easier to get on the phone and discuss these, let us know. thanks in
advance for your assistance.
1. Can you send us (electronically) how the dissolved Cu permit limits
were derived? Was the Texas method used in this derivation?
2. This facility seems to be consistently violating its chronic WET
limits in its current permit. What has been/is being done to followup
these violations?
3. How can the facility be pursuing a WER if it has ongoing chronic
toxicity?
4. It seems that the facility is already meeting the proposed permit
limits, so it's strange that they are pursuing a WER. Can you explain?
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8/23/2005 11:06 AM

August 2, 2005
Mr. David Goodrich
Point Source Branch
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
CHARLOTTE
Ms. Michelle Woolfolk
Modeling and TMDL Unit
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Need For Assimilative Capacity Modeling for the Sugar Creek Watershed
Dear Mr. Goodrich and Ms. Woolfolk:
We are following up in response to a letter dated August 8, 2003 regarding water quality
modeling needs for our speculative limits request for expansion of our wastewater facilities
in the Sugar Creek watershed. Your letter discussed the need for additional long-term BOD
data and the potential use of the QUAL2E model to assess assimilative capacity in the
watershed.
We have hired CH2M HILL to assist us with planning for our future wastewater capacity
needs and for evaluating assimilative capacity in the Sugar Creek watershed. As one of the
first steps in this analysis, they have developed a Technical Memorandum (TM)
summarizing water quality assessment information and the prior water quality modeling
for the watershed (see attached TM No. 1 - Evaluation of the Need for Assimilative Capacity
Modeling in the Sugar Creek Watershed). From this analysis, we have concluded that there
is little value in expending the resources necessary to update a water quality model for the
watershed. Our existing effluent limits are sufficient to protect dissolved oxygen in the
watershed. This analysis does not address toxicity or downstream nutrient issues.
Our suggestion is that we have a conference call either the last week of August or right after
Labor Day to discuss this TM and our conclusions. Bill Kreutzberger/CH2M HILL will be
contacting you to set up this call. In the meantime, please contact me at [phone] or by
email at [e-mail] if you have any questions.
Sincerely,
7ncquline Jarrell, P
vironmental Management Division Superintendent
Si)
c: Barry Gullet, PE/CMU
Ron Weathers, PE/CMU
Julie McLelland, PE/CMU
Bill Kreutzberger/CH2M HILL
CHARLOTTE-MECKLENBURG UTILITIES
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5100 Brookshire Boulevard
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TECHNICAL MEMORANDUM 1 CH2MHILL
Evaluation of the Need for Assimilative Capacity
Modeling in the Sugar Creek Watershed
PREPARED FOR: Charlotte -Mecklenburg Utilities
PREPARED BY: CH2M HILL
COPIES: Julie McLelland/CMU
Barry Gullett/CMU
Jackie Jarrell/CMU
Dawn Padgett/CMU
DATE: August 1, 2005
2
Nti
AUG 8 2005
DENR - WATER DUALITY
POINT SOURCE BRA„CH
•
Executive Summary
Charlotte -Mecklenburg Utilities (CMU) is planning for an increase in wastewater treatment
capacity for areas served by the Irwin Creek, Sugar Creek and McAlpine Creek Wastewater
Management Facilities (WWMFs). A key issue for the planned expansion(s) is the treatment
requirements for oxygen consuming wastes. In August 2003, the NC Division of Water
Quality (DWQ) indicated a need for development of a model to evaluate assimilative capacity
issues for oxygen consuming wastes in the receiving streams for the WWMFs. This Technical
Memorandum (TM) examines water quality assessment information, prior water quality
modeling, and available instream dissolved oxygen (DO) data to assess the need for
additional modeling to evaluate assimilative capacity.
Available assessment information for the Sugar Creek watershed in North and South Carolina
indicate problems characteristic of urban and urbanizing watersheds - with aquatic life
impairment based on degraded biological conditions, turbidity, and occasional elevated
metals. Dissolved oxygen levels are relatively robust throughout the watershed and are not
cited as a cause of impairment. Previous QUAL2E-UNCAS modeling for the Sugar Creek,
watershed indicate that treatment levels currently in place adequately protect DO levels in the
watershed. If this existing model were used to evaluate increases in flow, predicted DO levels
would increase because of the increased instream flow, the reduced effect of SOD (with
increasing flow depth and stream velocity), and methodology for modeling reaeration.
Similar results would be expected with an updated model. Instream DO data were
summarized for stations in the Sugar Creek watershed for the period 2000 through 2004,
which included nearly three years of a severe drought. Despite the drought conditions, only a
few data points approached the average day DO water quality standard of 5.0 mg/L and the
lowest data point was 5.1 mg/L. Data confirm water quality assessment and modeling results
that low DO levels are not an issue in the watershed.
Based on these results, additional assimilative capacity modeling of the Sugar Creek
watershed does not seem necessary to address expanded discharges from the wastewater
management facilities. Existing limits are sufficient to protect DO in the watershed.
FINAL TM 1-07262005.DOC 1

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
Introduction
Charlotte -Mecklenburg Utilities (CMU) is planning for an increase in wastewater treatment
capacity for areas served by the Irwin Creek, Sugar Creek and McAlpine Creek Wastewater
Management Facilities (WWMFs). These facilities, all located within the Sugar Creek
watershed, are currently permitted for a total maximum capacity of 99 mgd. An analysis
completed by McKim and Creed (2001) indicated that an additional 26 mgd of treatment
capacity was required by 2020. These flow projections are being re-evaluated as part of an
ongoing wastewater treatment alternatives study.
The key issues for this evaluation are future effluent quality requirements to meet water
quality standards in both North and South Carolina. The primary issues affecting effluent
requirements are related to oxygen consuming wastes, nutrients (nitrogen and phosphorus),
and toxic substances. CMU currently has total phosphorus limits for each of the three facilities
(with a bubble compliance approach) and future nutrient limits will be largely driven by an
ongoing total maximum daily load (TMDL) evaluation in South Carolina. The WWMF permits
for the Irwin and Sugar WWMFs have been re -issued with requirements to address South
Carolina's water quality standards for metals. CMU staff have been planning for similar
requirements for the McAlpine WWMF. These requirements should not substantially change
with an increase in treatment capacity at the WWMFs because the streams are effluent
dominated. This technical memorandum (TM) will review issues related to the Sugar Creek
watershed's ability to assimilate additional loading of oxygen consuming wastes and the need
for a detailed instream modeling analysis.
WWMF Background
The Irwin Creek, Sugar Creek and McAlpine Creek WWMFs discharge (Figure 1) to small
streams in Mecklenburg County that are effluent dominated. The facilities have instream
waste concentrations (IWC) at low flow of 83 percent or more. Because of the small receiving
streams, the WWMFs have effluent limits for oxygen -consuming wastes, 5-day biochemical
oxygen demand (BOD5) and ammonia -nitrogen (NH3-N) that are as stringent as any limits in
the state. Limits for BOD5 and NH3-N are shown in Table 1.
Assimilative Capacity Evaluation Needs
Routinely, utilities planning for increased treatment capacity request the Division of Water
Quality (DWQ) for "Speculative Permit Limitations" early in the planning process. DWQ
typically performs a modeling analysis to determine these limits. CMU requested speculative
limits during a meeting with DWQ in July 2003. In August 2003, DWQ responded regarding
the major water quality issues in North and South Carolina and the necessary steps to obtain
speculative limits from DWQ. They indicated a need for development of a receiving water
model to evaluate assimilative capacity issues. DWQ suggested QUAL2E but allowed that
other models could be utilized. The previous QUAL2E model was developed in the early
1990s by the Division of Environmental Management (DEM), predecessor to DWQ (DEM,
1993).
FINAL TM 1 - 07262005.DOC 2

3 1.5 0 3 Miles
State Boundary
County Boundary
c2 Interstate
Highway
Waterbodies
Greater Sugar Creek Watershed
A Wastewater Facilities
Figure 1
CMU Wastewater Treatment Facilities
CH2MHILL in Sugar Creek Watershed

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
TABLE 1. EXISTING WWMF NPDES PERMIT LIMITATIONS
Facility
Flow
cBOD5
NH3-N
Monthly
Ave.
(mgd)
Monthly
Ave. (mg/L)
Weekly Ave.
(mg/L)
Monthly
Ave. (mg/L)
Weekly Ave.
(mg/L)
Irwin Creek
(summer)
15.0
5.0
7.5
1.2
3.6
Irwin Creek
(winter)
15.0
10.0
15.0
2.3
6.9
Sugar Creek
(summer)
20.0
5.0
7.5
1.0
3.0
Sugar Creek
(winter)
20.0
10.0
15.0
2.0
6.0
McAlpine
Creek
(summer)
64.0
4.0
6.0
1.0
NL
McAlpine
Creek (winter)
64.0
8.0
12.0
1.9
NL
Note: cBODs = carbonaceous BOD5; Summer = April through October; Winter = November
through March; NL = No Limit.
Water Quality Assessment Information
Water quality assessment information is available for the Sugar Creek watershed in North and
South Carolina from a number of sources including basin plans prepared by DWQ and SC
Department of Health and Environmental Control (DHEC). These watershed assessments are
conducted approximately every 5 years and are also used for developing the 303(d) list of
impaired water bodies in both states. Mecklenburg County has extensive monitoring and
publishes a State -of -the -Environment Report every two years. CMU also conducts instream
monitoring as part of their NPDES compliance requirements as well as the various monitoring
programs.
State Assessment Information
The NC Catawba River Basinwide report (DWQ, 2004) summarized biological and water
quality monitoring information for the Sugar Creek watershed. DWQ used data from eight
biological sampling locations which did not include the Mecklenburg County data. All sites
were found to have degraded habitat, a sand/silt substrate, severe bank erosion, and
disturbed or nonexistent riparian vegetation. In addition, elevated levels of fecal coliform and
turbidity were identified as problem water quality parameters. Portions of Irwin (11.8 mi.),
Sugar (11.2 mi), Little Sugar (5.5 mi.) and McAlpine (4.6 mi.) Creeks were considered as
impaired. Water quality conditions have remained "low" but stable over the planning cycle.
FINAL TM 1-07262005.DOC 4

TM 1- EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
The report cites increasing levels of nitrite plus nitrate -nitrogen (NOx-N) and dissolved
oxygen at several locations within the watershed.
The SC watershed report (SCDHEC, 2001) for the Catawba River Basin includes a specific
section for the Sugar Creek watershed. They have a total of 11 sampling sites in the Sugar
Creek watershed including three in NC. DHEC indicates that aquatic life uses are not fully
supported in parts of Sugar Creek based on cadmium excursions and macroinvertebrate data.
They also cite impairment of recreational uses due to fecal coliform excursions. For Little
Sugar Creek; DHEC indicates aquatic life uses are fully supported but recreational uses are
not supported (due to fecal coliform levels). For McAlpine Creek, the report indicates that
aquatic life uses are supported at old US 521 but notes significant increasing trends in BOD5
and total phosphorus (but does not cite time frame or provide data). A significant decreasing
trend in pH and high sediment chromium concentrations are also noted. Further downstream
on McAlpine Creek, aquatic life uses are not supported based on macroinvertebrate data.
The Catawba River assessment information is also important relative to the potential impacts
from the WWMFs. At US 21 near Rock Hill upstream of the confluence of Sugar Creek, aquatic,
life uses are fully supported but periodic elevated copper and zinc levels were observed.
Downstream of Sugar Creek at SC HWY 5 but upstream of Bowater, aquatic life uses were
fully supported with significant decreasing trends in BOD5 and total nitrogen suggesting
improving conditions. Recreational uses were also fully supported with a significant
decreasing trend in fecal coliform levels. Further downstream at SC HWY 9 at Fort Lawn,
aquatic life uses were still supporting with a significant increasing trend in total phosphorus.
Recreational uses were also fully supporting at SC HWY 9.
A good summary of this assessment information can be obtained through examination of the
303(d) lists and maps of the impaired streams. Attachment 1 includes the applicable portions
of the NC and SC 303(d) lists for the Sugar Creek and Catawba Watersheds. While both the
NC 303(d) list and the NC Catawba Basinwide Plan were developed in 2004, the basinwide
plan information was not used for the 2004 303(d) list. Figure 2 shows the impaired water
bodies from the basinwide plans. The 303(d) list will be updated in 2006 to reflect this updated
assessment. It is important to note that no water quality problems are attributed to low DO.
There are few water quality issues directly attributed to the WWMF discharges and none that
would be addressed through additional assimilative capacity modeling.
Mecklenburg County State -of -the -Environment Report
The Mecklenburg County Water Quality Program has a comprehensive monitoring program
within the County including over 50 ambient stations, approximately an equal number of
biological/habitat assessment stations, and five stormwater stations. In addition, they conduct
numerous investigations related to spills, complaints, or other suspected contamination of
surface and groundwater in the County.
The 2004 State -of -the -Environment Report (Mecklenburg County, 2004) summarized water
quality conditions for the Sugar Creek watershed for Sugar Creek (including Irwin Creek,
Stewart Creek, Taggart Creek, Coffey Creek, Kings Branch, and Steele Creek), Little Sugar
Creek (including Edwards Branch, Briar Creek, Dairy Branch, and Little Hope Creek), and
McAlpine Creek (including McMullen Creek, Six Mile Creek, Irvins Creek, Campbell Creek,
and Four Mile Creek). For all of the watersheds, major sources of pollution listed included
urban runoff, sanitary sewer overflows, failing septic systems, illicit connections to storm
FINAL TM 1- 07262005.DOC 5

ourmile Creek
cAlpine Cree
WtNTF
State Boundary
County Boundary
Interstate
Highway
Greater Sugar Creek Watershed
Waterbodies
Impaired Water From NC 303d List
Impaired Water Based on SC 303d List
A Wastewater Facilities
3 1.5 0 3 Miles
N
CH2MHILL
Figure 2
Impaired Waters in Sugar Creek
Watershed Within North Carolina

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
sewers, and straight pipe connections. Recreational impairment was the focus in all of the
portions of the Sugar Creek watershed. There was no mention of aquatic life impairment as a
result of low DO levels.
Sugar Creek QUAL2E Modeling
Special studies and development of a QUAL2E-UNCAS model were undertaken by DEM in
the early 1990s in response to a request to expand the McAlpine Creek WWMF and to support
the development of the first Catawba River Basinwide Water Quality Management Planning
effort in the mid-1990s (DEM, 1993). Details of the studies and the modeling effort are
addressed with excerpts from the modeling report included as Attachment 2. The study was
reportedly undertaken because of numerous occurrences of DO levels below the stream
standard under low flow conditions. Figure 4 in Attachment 2 shows historical NH3-N, BOD5,
and DO from 1983 until 1992. DO levels below the standard occurred most frequently prior to
1987.
The monitoring studies to support the modeling were comprehensive in nature and included
two time -of -travel (TOT) studies on Little Sugar and Sugar Creeks (1989 and 1990) and two
earlier TOT studies on McAlpine Creek (1986 and 1987). Sediment oxygen demand
measurements were also conducted in 1990. Table 1 and Figure 3 in Attachment 2 show the
scope of the TOT studies and the locations for sampling. Model set-up and calibration
followed standard procedures. Figure 2 in Attachment 2 is a schematic of the basic model set-
up. Final calibration was deemed adequate but predictions on Little Sugar Creek were
variable. There appeared to be a slight over prediction of DO for McAlpine Creek but the
steep DO sag was well represented.
The model was applied to existing (1992), permitted (in 1992), and future permitted discharge
conditions for the three WWMFs. Table 3 in Attachment 2 shows a summary of these
conditions. The wasteload allocation modeling showed that DO levels would be protected
with the future limits but were not adequately protected with the current limits or the then
current discharge conditions. A first order error analysis was used to determine relative
sensitivity of the model parameters. The first order error analysis indicated that the model
predictions were most sensitive to the following input parameters:
• Temperature
• Hydraulics
• Point load DO (in McAlpine Creek)
• BOD decay rate
• SOD rate
• Point load flow
• Point load BOD
A Monte Carlo analysis was also performed to generate confidence limits for the model
predictions. The projected confidence limits around model predictions at key locations in the
system are shown in Table 2 (DEM, 1993).
FINAL TM 1- 07262005.DOC 7

TM 1- EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
TABLE 2. WASTELOAD ALLOCATION MODELING RESULTS FOR DO
Station Location
DO estimate, with 95% confidence
interval (mg/L)
S4, 1 mile below Irwin Creek WWTP
S8, DO sag below Irwin Creek WWTP
L7, mouth of Little Sugar Creek
M6, mouth of McAlpine Creek
S18, bottom of the study area
6.1 +/- .4
5.7 +l- .7
6.0 +/- .7
5.1 +/- .7
6.2 +/- .6
(5.7 - 6.5)
(5.0 - 6.4)
(5.3 - 6.7)
(4.4 - 5.8)
(5.6 - 6.8)
Since this modeling was conducted over 12 years ago, there are a number of observations that
are applicable to a decision to update the modeling as follows:
• BOD and ammonia oxidation rates - the rates used are more reflective of secondary
effluent that was more common in the 1980s than highly treated effluent currently
produced by the facilities. More recent QUAL2E models use lower oxidation rates
appropriate for high quality effluents.
• cBODu/ BOD5 ratios used for the modeling do not reflect current effluent quality
conditions and additional effluent long-term (LT) BOD values are necessary to update
these ratios.
• Extensive development has continued in the NC and SC portions of watershed that have
probably led to significant channel changes. HSPF models developed by Mecklenburg
County focused more on high flow channel characteristics. Updated wasteload modeling,
if conducted, should re-examine channel cross -sections and update model hydraulics.
• Key instream water quality information, particularly SOD and LT BOD are no longer valid
and would need to be updated.
The existing model could be run for future flow scenarios. However, it can be determined
through examination of the 1993 modeling report that DO excursions would not be predicted
with increased wastewater flows. The first order error analysis indicated that predicted DO is
positively correlated with point source flow. The streams are already effluent dominated;
therefore the increased flows will serve only to increase water depth and increase stream
velocity with the water quality characteristics staying the same. The increased flows will
increase reaeration and decrease the influence of SOD and thus spread any DO sag over a
longer stretch of the stream while reducing the magnitude of the decline. Similarly, the BOD
and ammonia decay rates used 12 years ago are high considering CMU's current level of
treatment. As these rates are decreased, the modeling sag will move further downstream.
An updated model would require extensive data development as noted above and would still
result in similar predictions regarding DO levels.
FINAL TM 1- 07262005.DOC 8

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
Dissolved Oxygen Data
As part of instream monitoring, CMU collects instream DO and temperature data at key
locations in North and South Carolina. During the period from 2000 through most of 2002,
drought conditions were prevalent throughout central North Carolina, with 2002 having the
most severe conditions from late spring through early fall. To evaluate this, DO and
temperature data were summarized for several sites from 2000 through 2004. USGS flow data
were summarized for sites in close proximity to these locations for comparison. Sites that were
selected include:
• LSC1 - This site is located on Little Sugar Creek upstream of the Sugar Creek WWMF
effluent just below the confluence of Little Sugar Creek and Briar Creek.
• SC2 - This site is located on Sugar Creek at Arrowood Road near I-77 approximately
3.5 miles downstream of the Irwin Creek WWMF discharge.
• MC2 - This site is located on McAlpine Creek approximately 2.5 miles downstream
of the effluent from McAlpine Creek WWMF discharge. The site is off of Dorman Rd (in
NC).
• SC5 - This site is located on Sugar Creek at Hwy 160 in SC at the county line
between York and Lancaster Counties. It includes Sugar Creek, Little Sugar Creek,
McAlpine Creek and the Steele Creek Basins.
Figures 3 through 6 illustrate DO and temperature data for this three year period for these
sites. USGS flow data are also shown near three of the four sampling sites. The DO data
during this period are consistent with the previously summarized assessment reports. Even
during the extended drought period in the summer of 2002, only a few DO data points were
less than 6.0 mg/L. The lowest DO in the data set of 5.1 mg/L occurred in July 2000 at MC2 on
McAlpine Creek. The second lowest value was 5.3 mg/L in October 2002, near the end of the
drought, at LSC1 above the Sugar Creek WWMF.
Conclusions
Available assessment information for the Sugar Creek watershed in North and South Carolina
indicate problems characteristic of urban and urbanizing watersheds - with aquatic life
impairment based on degraded biological conditions, turbidity, and occasional elevated
metals. Sources of this impairment were attributed to degraded habitat, urban stormwater and
poor riparian corridor management. Recreational activities are impaired based on elevated
fecal coliform levels with sources being stormwater, sewer leaks/overflows, septic systems,
avian populations, and wastewater discharges. Dissolved oxygen levels are relatively robust
throughout the watershed and are not cited as a cause of impairment.
Previous QUAL2E-UNCAS modeling for the Sugar Creek watershed indicate that treatment
levels currently in place adequately protect DO levels in the watershed. If this existing model
were used to evaluate increases in flow, predicted DO levels would increase because of the
increased instream flow, the reduced effect of SOD (with increasing flow depth and stream
velocity), and methodology for modeling reaeration.
Updating the QUAL2E-UNCAS model would require extensive data collection since the TOT
and SOD data sets are at least 15 years old. The physical depiction of the stream and
hydraulics would need to be updated as well. Since EPA no longer supports QUAL2E and it
FINAL TM 1- 07262005.DOC 9

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
M USGS
USGS 02146409 LTL SUGAR CR AT MEDICAL CENTER DR AT CHARLOTTE, NC
808.8
188.0
10.0
DAILY MEAN STRERMFLON, IN CUBIC FT PER SEC
1.0
il
i
it
1
5
J
1
8.5
2880 2000 2001 2881 2002 2002 2003 2003 2004 2804 2805
EXPLANATION
—DAILY MEAN STREAMFLOM —ESTIMATED STREAMFLOM
Figure 3a. Little Sugar Creek Daily Flow at Medical Center
15.0
5.0
0.0
1/24/00
1/24/01
DO &Temp @LSC-1
1/24/02 1/24/03
DATE
1/24/04
30.0
125.0
20.0
a
- 15.0 m
1-
10.0
i 5.0
0.0
—s— DO
-.—Temp
Figure 3b. Little Sugar Creek DO and Temperature below confluence with Briar Creek and
above Sugar Creek WWMF
FINAL TM 1 - 07262005. DOC
10

TM 1 • EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
USGS
DRILY MERU STRERMFLON, IN CUBIC FT PER SEC
4800
3880
2000
1000
100
USGS 02146381 SUGAR CREEK AT NC 51 NEAR PINEVILLE, NC
J
2880 2000 2001 2001 2002 2802 2003 2803 2804 2804 2005
EXPLANATION
— DRILY MEAN STREAMFLOM ESTIMATED STREAMFLON
Figure 4a. Sugar Creek Daily Flow near Hwy 51
O
DO &Temp @SC-2
15.0
10.0
5.0
0.0
1/24/00 1/24/01 1/24/02 1/24/03 1/24/04
DATE
30.0
25.0
20.0
15.0
10.0
0.0
—.— DO
+Temp
Figure 4b. Sugar Creek DO and Temperature at Arrowood Road (about 3.5 Miles downstream
of Irwin Creek WWMF)
FINAL TM 1- 07262005.DOC
11

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODEUNG IN THE SUGAR CREEK WATERSHED
USGS
M • 3000
w 2080
H 1000
H
O
J
lJ
=
W
OC
r
Lei
• 108
I 60
USGS 02146820 SUGAR CR. NR FT. MILL, S.C.
ti
N
Jul Sep Nov Jan Mar May Jul Sep
2001 2001 2001 2002 2002 2002 2802 2882
EXPLAHATIOH
— DAILY MEAN STREAMFLON — ESTIMATED STREAMFLON
Figure 5a. Sugar Creek Daily Flow near Fort Mill, SC (Limited flow record)
DO &Temp @SC-5
15.0 -35.0
- 30.0
i 25.0
10.0
5.0 - _ —
-10.0
20.0 o.
- 15.0
0.0
1/6/00 1/6/01 1/6/02 1/6/03 1/6/04
DATE
—s— DO
--4— Tem p
Figure 5b. Sugar Creek DO and Temperature near Fort Mill, SC
FINAL TM 1-07262005.DOC 12

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
DO &Temp @MC-5
- 30.0
- 25.0
20.0
- 15.0
f-
10.0
- 5.0
0.0
1/25/00 1/25/01 1/25/02 1/25/03 1/25/04
Figure 6. McAlpine Creek DO and Temperature at old US 521
T DO
--o— Temp
does not run on Windows XP or 2000 operating systems, a new modeling platform, such as
QUAL2K would be required for the updated modeling analysis.
Available DO data for the watershed confirms the lack of DO standards excursions below
wastewater facilities including downstream in SC where the collective impact of all the
watershed effects and wastewater facilities should be exhibited.
There is no evidence to support the need for this additional modeling of assimilative capacity.
Existing limitations for cBOD5 and NH3-N adequately protect DO levels in the watershed.
References
Division of Environmental Management, 1993. An Application of the QUAL2E River Model to
Sugar Creek, Little Sugar Creek, and McAlpine Creek, Mecklenburg County, NC and York County,
SC. NC Department of Environment, Health and Natural Resources, Raleigh, NC.
Division of Water Quality, 2004. Catawba River Basinwide Water Quality Management Plan. NC
Department of Environment and Natural Resources, Raleigh, NC.
Division of Water Quality, 2004. Draft 303(d) List of Impaired Waters. NC Department of
Environment and Natural Resources, Raleigh, NC.
McKim and Creed, 2001. Technical memorandum: Wastewater System Management Study -
Charlotte -Mecklenburg Utilities.
Mecklenburg County, 2004. State of the Environment Report.
FINAL TM 1-07262005.DOC 13

Attachment 1
Excerpts from the North Carolina and South Carolina Draft 2004
303(d) Lists for the Sugar Creek Watershed
FINAL TM 1- 07262005.000 t 14

Catawba River Basin
Subbasin: 30834
Waters `or which TMDLs are required.
Assessment
Waterbody and Description Unit (AU)
Year
Class Subbasin lrnpairedUse Listed Category and Reason for Listing potential Source(s/ Miles Acres
Irwin Creek 11-137-1
C 3234 1998 5
11.8
From source to Sugar Creek Overall 2000 5 Standard violation: Turbidity
1998 6 Impaired biological integrity:
stressors not identified
2000 4e Standard violation: Fecal
Coliform
1 Industrial Point Sources
Municipal Point Sources
Urban RunofflStorm Sewers
Mccullough Branch 11-137-7
C 32234 1998 6
2.6
From source to Sugar Creek
Overall 1998 6 Impaired biological ,ntegnty Surface mining
stressors not identified
Little Sugar Creek
11-137-8a C 30834 2000 6
1I.8
From source to Archdale Rd Overall 2000 6 impaired biological integrity:
stressors not identified
2000 4a Standard violation: Feat:
Coliform
Municipal Point Sources
Urban Runoff/Storm Sewers
Little Sugar Creek
11-137-8b C 30834 1998 6
c �
From Arcda e 'Rd to FC 5.
Overall
1998 6 Impaired biological integrity:
stressors not identified
1998 4a Standard violation: Fecal
Coliform
I Municipal Point Sources
:: Urban Runoff/Storm Sewers
Little Sugar Creek 11-137.8c C 30834 2000 5 3.6
From NC 51 to state line Overall 2000 5 Standard violation: Turbidity
2000 6 Impaired biological integrity:
stressors not identified
2000 4a Standard violation: Fecal
Coliform
I Municipal Point Sources
Urban Runoff/Storm Sewers
McAlpine Creek 11-137-9a C 3 234 1998 5 8.3
From source to SR 3356, (Sardis Rd) Overall 1998 5 Standard violation: Turbidity I Urban Ruoff/Storm Sewers
1998 6 Impaired biological integrity:
stressor study complete
3 1998 4a Standard violation: Fecal
Coliform
FINAL TM 1 - 07262005.DOC 15

TM 1 - EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
Catawba River Basin
Subbasin: 30834
•;v'aters `or which Th1CLs are required.
Waterbody and Description
Assessment Year
Unit (AU) Class Subbasm ImpairedUse Listed Category and Reason for Listing Potential Source(s)
Miles Acres
McAlpine Creek 11-137-9b
C 3:234 1998 5 6-3
From SR 3356 to NC 51 Overall 1 1998 5 Standard violation: Turbidity 1 Urban Runoff/Storm Sewers
2 1998 6 Impaired biological integrity:
stressor study complete
3 2000 4a Standard violation: Fecal
Coliform
McAJpine Creek 11-137-9c . _
C 30834 2000 5
From NC51toNC521
4.7
Overall ' 2000 5 Standard violation: Turbidity
2000 6 Impaired biological integrity:
stressor study complete
2000 4a Standard violation: Fecal
Coliform
t Urban Runoff/Stonn Severs
McAlpine Creek 11-137-9d C 30834 1552 5 1.1
From NC Hwy 521 to NC/SC stateline Overall 1298 5 Standard violation: Turbidity
I598 6 Impaired biological Integrity:
stressor study complete
5 1998 4a Standard violation: Fecal
Coliform
Urban Runoff/Storm Sewers
Sugar Creek 11-137a C 30834 1998 6 0.2
From source to belcw W WTP, SR 1156, Mecklenburg
Overall • 1998 6 Impaired biological integrity:
stressors not identified Urban Runoff/Storm Sewers
Municioa! Pont Sources
Sugar Creek 11-137b C 30834 1998 5 11.9
From SR 1156 Mecklenburg, to HWY 51 Overall 1998 5 Standard violation: Turbidity
1998 6 Impaired biological integrity:
stressors not identified
1998 4a Standard violation: Feder
Coll fun n
Urban Runoff/Storm Sewers
Sugar Creek 11-137c C 30834 2000 5 1.2
From Hwy 51 to NC/SC border Overall 2000 5 Standard violation: Turbidity ' Urban Runof /S:cmm Sev:e-s
2. 2000 6 Impaired biological integrity:
stressors not identified
3 2000 4a Standard violation: Fecal
Colifonn
FINAL TM 1 - 07262005. DOC 16

TM 1- EVALUATION OF THE NEED FOR ASSIMILATIVE CAPACITY MODELING IN THE SUGAR CREEK WATERSHED
2004 SC List of Impaired Waters by 11-Digit HUC
BASIN
11 DIGIT HUC
LOCATION
STATION
COUNTY
USE
CAUSE
NOTES
BROAD
03050108340
DUNCAN CK AT US 175 1.5 h11 SE OF WHITMIRE
B-072
NEWBERRY
REC
FC
BROAD
030:e71C8040
BEARDS FORK CK AT US 270 41.385) 3.7 MI NNE OF CUNTON
B-231
LAURENS
AL
DO
3ROAD
0305010804C
BEARDS FORK CK AT US 278 II-385) 3.7141 NNE OF CUNTON
B-231
LAURENS
REC
FC
'
BROAD
D3050108040
DUNCAN CREEK AT COUNTY RD 25. 4.5 M NE CF CU?TON
RS-01057
LAURENS
R=-C
41011.1118tkItlX010
tNUetttHVRA110-_'tl=h3.5MIABJC; WI1MBROADRVR
E-Oo4
\E':d=RRY
R`-C
0
•
CATAWBA
030501011E0
CROYhDERS CK AT S-45-554 NE CLOVER
CW-102
YORK
REC
FC
CATA.: BA
030501011E0
CROWDERS CREEK AT S-45.1104
CW024
YORK
AL
810
CA.TA':: _.A
030501011E0
CR04yt8R5 CREEK AT S-05-I104
CW-D24
YORK
REC
FC
AT ='.: E. =
D30501011E0
LK WYUE, CROWDERS CK ARM AT SC 49 ANO SC 274
CW-027
YORK
R:-C
FC
=T- : _ '
Q3050101120
BROWN GREEK AT S-15-225 4GUINN ST). 0.31MM WEST OK OLD NORTH MAN STREET
IN CLOVER. SC
CW-105
YORK
AL
T JP.BID'Y
CATAWBA
030E01011E0
= 0 JTH FORK CR0'N EPS CY. A- 5-=0-7945 I: r.:Y OF C_: vE?
CW-1£2
YORK
C
FC
CATAWBA
03050101180
LAKE. WYLIE AB MILL CK ARM AT END OF S45.5=7
CW-187
YORK
Al.
CU
CATAWBA
630.501011W
ALLSON CK AT SJ:5-114
CW _4ti+
YORK
•FtaC
FC
CATAWBA
03050010301C
CATAWBA RVR AT US 21
001-014
YOP.K
REC
FC
CATAWBA
03050103010
FISHING CK RES 2 M: BL CANE CREEK
CW-015F
:-1ESTE.R
AL
TP. TUR8ID' T Y
CATAWBA
03050103010
CEDAR CK RESERVOR 100 M N OF DAM
CW-033
ANCAS-ER
AL
TP
CATAWBA
03050103010
CATAWBA RVR AT SC 5 AB BOWATER
OW-441
LANCASTER
AL
CU
CATAWBA
03050103010
FISHING CK RES 75 FT AB DAM NR GREAT FALLS
CW-,W7
CHESTER
AL
TP
CATAWBA
D3050103010
CEDAR CK RESERVO R AT UNIMP RD AB JCT WTH ROCKY CK
CW-174
CHESTER
AL
DO. TN, TP
CATAWBA
0305 0103010
CEDAR CK RES 2.15 M SE OF GREAT FALLS
RL-01007
LANCASTER
AL
CHLA CO
CATAWBA
03050103010
E N0 CK t RES 3.8 M S OF FOR • LAWN OF W SHORE OF HEl '.:T. VF LAKE
RL-0t012
CHESTE.R
AL
CHLA
CATAWBA
03050103010
CEDAR CK RES FROM W OF BIG 'SL 7 MI BELOW ROCKY CK CONFL
RL-02319
CHESTER
AL
TP
CATAWEA
03050103010
CEDAR CK RES 0.15 MI SE OF S TIP PICKETT ISLAND
RL-M3452
LANCASTER
AL
'hP
CATA::==
C30:_'1C311.
5ibELEOKATS-40-22NOFt-ORTMILL
CW-`D?
'YORK
REC
FC
CATAY.8,
C305:1E3:_,:
ST'FF1s=CKATS-46-270
CW-011
YORK
REC
FC
CA.TA.:BA
6365: ic5-_'.
SUGAR CREEK AT 0-:5-3.e
CW-035
LANCASTER
AL
C!
CATAV-EC305"
C3:-
-=LPLE V" - -
0 lJ. -,
LANCASTER
AL
-
=.AT-'::...2C305:1
C31.,:
STEE.8 C. A- 3-1;-92
CW-2:3
YORK
REC
CAT=:.=-
C3050103020
SUGAR CKUSOFCONFLUENCE 'A"MC:ALPINEOK
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FINAL TM 1-07262005.DOC
17

Attachment 2
Excerpts from the QUAL2E Modeling Report for the Sugar
Cheek Watershed
FINAL TM 1- 07262005.DOC 18

An Application of a QUAL2E River Model to
Sugar Creek, Little Sugar Creek, and McAlpine Creek,
Mecklenburg County North Carolina
and York County South Carolina.
NORTH CAROLINA DEPARTMENT OF ENVIRONMENT, HEALTH
AND NATURAL RESOURCES
This report has been approved for release
Steve W. Tedder, Chef
Water Quality Section
N.C. Division of Environmental Management
Date f c L3//ff3

Table of Contents
List of Figures i
List of Tables i
Executive Summary ii
Introduction 1
Description of Receiving Stream 1
Model Development 9
Model Application 19
Results 21
Sensitivity Analysis 24
Summary and Recommendations 30
References 31
Appendix 1 32
Appendix 2 39

List of Figures
Figure 1 Sugar Creek Study Area 2
Figure 2 Schematic Showing USGS Flow Estimates 5
Figure 3 Water Quality Sampling Stations 6
Figure 4a Ammonia at Ambient Station 02146800 (S18) 8
Figure 4b BOD at Ambient Station 02146800 (S18) .... 8
Figure 4c DO at Ambient Station 02146800 (S18) 8
Figure 5a,b Predicted and Observed Conductivity 13
Figure 6a,b Predicted and Observed Organic Nitrogen 14
Figure 7a,b Predicted and Observed Ammonia 15
Figure 8a,b Predicted and Observed NO2 and NO3 16
Figure 9a,b Predicted and Observed Total Nitrogen 17
Figure l0a,b Predicted and Observed CBOD 18
Figure 1 la,b Predicted and Observed DO 20
Figure 12a Predicted Sugar Creek DO profile, existing permit limits 22
Figure 12b Predicted Sugar Creek DO profile, current discharges 22
Figure 12c Predicted Sugar Creek DO profile, future permit limits 22
Figure 13a Predicted Study Area DO profile, existing permit limits 23
Figure 13b Predicted Study Area DO profile, current discharges 23
Figure 13c Predicted Study Area DO profile, future permit limits 23
Figure 14a Predicted Ammonia profile, current discharge conditions 25
Figure 14b Predicted Ammonia profile, future permit limits 25
List of Tables
Table 1 Time of Travel and Water Quality Sampling Stations 4
Table 2 BMAN Bioclassifications 7
Table 3a Permit Limits for Major Facilities 21
Table 3b Actual Discharge Conditions for Major Facilities 21
Table 4a First Order Error Analysis, DO 26
Table 4b First Order Error Analysis, BOD 27
Table 4c First Order Error Analysis, NH3 28

EXECUTIVE SUMMARY
A water quality study of 32.3 stream miles in the Sugar Creek, Little Sugar Creek,
and McAlpine Creek watersheds in Mecklenburg County, North Carolina, and York
County South Carolina was performed to calibrate a QUAL2E water quality model. This
model was used to predict dissolved oxygen, ammonia, and biochemical oxygen demand
at low flow conditions.
The goal of the field study and water quality modeling was to provide a tool to
assist with management of wastewater discharge issues in the Sugar Creek watershed.
This model will also provide a modeling framework for basinwide management planning in
the Sugar Creek watershed. The Catawba River basinwide plan is due to be completed in
April 1995. The Sugar Creek watershed receives a significant amount of wastewater from
three major municipal discharges operated by the Charlotte -Mecklenburg Utilities
Department; Irwin Creek WWTP, Sugar Creek WWTP, and McAlpine Creek WWTP. In
addition, the Sugar Creek watershed receives pollutant loading from eight minor
discharges and a highly urbanized landscape.
Instream DO concentrations below the stream standard have been documented on
numerous occasions during low flow periods. Both point and nonpoint sources contribute
to these instream violations. This model of the Sugar Creek watershed provides a decision
making tool that can be used to address wasteload allocation issues as well as provide
support for management decisions in the Catawba River basinwide planning project.
The results of this study support the current management plan in place for the major
facilities in the Sugar Creek watershed. Current permit limits do not protect water quality
in the study area. However, each major facility has new permit limits that will apply to
any future modification. These new limits will dramatically lower BOD loading to the
system and are predicted to prevent DO from dropping below the instream standard
during 7Q10 conditions.
Results of the study suggest that the current management plan and new permit
limits for the Irwin Creek, Sugar Creek, and McAlpine Creek WWTPs are consistent with
the goal of improving water quality in the Sugar Creek watershed. Once the new permit
limits are met at the three major WWTPs, the model predicts that the discharge of oxygen
consuming wastes will not result in water quality problems in the Sugar Creek watershed.
This effort will be a significant step towards the goal of removing Irwin, Sugar, Little
Sugar, and McAlpine Creeks from the State's 303d list of impaired waters. Until the new
permit limits are in effect, all three major CMUD facilities should be encouraged to
continue their efforts to reduce BOD loading to the Sugar Creek Watershed.
ri

I. INTRODUCTION
A water quality study of 32.3 stream miles in the Sugar Creek, Little Sugar Creek,
and McAlpine Creek watersheds in Mecklenburg County, North Carolina, and York
County South Carolina was performed in order to calibrate a QUAL2E water quality
model. This model was used to predict dissolved oxygen (DO), ammonia (NH3), and
biochemical oxygen demand (BOD) at low flow conditions.
The goal of the field study and water quality modeling was to provide a tool to
assist with management of wastewater discharge issues in the Sugar Creek watershed.
This model will also provide a modeling framework for basinwide management planning in
the Sugar Creek watershed. The Catawba River basinwide plan is due to be completed in
April 1995. The Sugar Creek watershed receives a significant amount of wastewater from
three major municipal discharges operated by the Charlotte -Mecklenburg Utilities
Department (CMUD): Irwin Creek WWTP, Sugar Creek WWTP, and McAlpine Creek
WWTP. In addition, the Sugar Creek watershed receives pollutant loading from eight
minor discharges and a highly urbanized landscape.
Instream DO concentrations below the stream standard have been documented on
numerous occasions during low flow periods. Both point and nonpoint sources contribute
to these instream violations (NC DEM 1990). This model of the Sugar Creek watershed
provides a decision making tool that can be used to address wasteload allocation issues as
well as provide support for management decisions in the Catawba River basinwide
planning project.
1:I. DESCRIPTION OF RECEIVING STREAM
A. Location
Sugar Creek, Little Sugar Creek, and McAlpine Creek drain approximately 260
square miles of the greater Charlotte area in sub -basin 03-08-34 of the Catawba River
basin. Sugar Creek runs from its headwaters 5 miles north of downtown Charlotte south
to South Carolina where it joins the Catawba River. This study focused on 32.3 total
stream miles of Sugar Creek, Little Sugar Creek, and McAlpine Creek. The study area
included stream sections immediately upstream of each of the three major CMUD water
treatment facilities and downstream sections to 7 miles below the point where all three
streams have converged (Figure 1).
B. Channel Characteristics
The study area can be generally characterized by streams with moderate slopes of
4 to 6 feet per mile. Sugar and McAlpine creeks have relatively consistent slopes
throughout the study area. Sugar Creek has an average slope of 5.8 ft/mile and McAlpine
Creek a slope of 4.1 ft/mile. Little Sugar Creek has a wide range of slopes throughout the
1

Figure 1. Sugar Creek Study Area.
Taggart Creek
Coffey Creek
Rivermile 2.1
•
•
•
Rivermile 12.9
Steele Creek
rwin (Sugar) Creek
Irwin Creek WWTP
Rivermile 0.0
0
CHARLOTTE
/1111\
Little Sugar Creek WWTP
9.1 miles above Sugar Creek
Little Sugar Creek
•
Rivermile 15.5
Sugar Creek
Rivermile 19.1
2
McAlpine Creek
McAlpine Creek WWTP
4 miles above Sugar Creek

study area, ranging from 2.8 to 16.9 ft/mile. Overall it is the steepest of the three streams
with an average slope of 6.5 f /mile.
Sections of Sugar, Little Sugar, and McAlpine creeks have been channelized and
dredged. Portions of the streams are dredged and maintained by the Mecklenburg County
Drainage Commission. The watershed is highly urbanized, with approximately 15%
impervious surface (Barker et. al. 1991).
C. Flow/Hydraulics
Each of the three streams included in this study are heavily dominated by
wastewater flow. Streamflow statistics for key locations within the study area were
provided by the USGS (Figure 2). The estimated 7Q10 flows indicate that during low
flow periods the hydraulics of each stream are controlled by effluent flow. Sugar Creek
rises from an estimated 7Q10 of 4.9 cfs above the Irwin Creek WWTP to 15 cfs 19 miles
downstream. Little Sugar Creek has an estimated 7Q10 of 3.4 cfs above the Sugar Creek
WWTP and 4.2 cfs above its confluence with Sugar Creek. McAlpine Creek has an
estimated 7Q10 of 1.3 cfs above the McAlpine Creek WWTP and 1.3 cfs at its mouth
(Figure 2). Each of these streams receives an average wastewater flow greater than 20
cfs. Clearly, the entire study area is heavily utilized for the assimilation of wastewater.
D. Water Quality Data
Two time of travel (TOT) studies were performed on Sugar and Little Sugar
Creek. The first TOT study, conducted at mid flow conditions, was begun April 18, 1989.
The second TOT study, conducted during low flow conditions, was begun July 24, 1990.
The second study included physical and chemical sampling at stations along Sugar and
Little Sugar creeks, as well as at the mouth of McAlpine Creek (Figure 3).
Two TOT studies had previously been conducted on McAlpine Creek. A mid flow
study was begun March 18, 1987 and a low flow TOT study with physical and chemical
sampling was begun June 26, 1986. Water quality samples were taken at six sampling
locations along McAlpine Creek (Figure 3).
SOD measurements and long term BOD samples were collected at selected sites
throughout the study area during 1990. Table 1 presents the water quality parameters
collected at each sampling station in the study area.
3

Table I. Time of Travel and Water Quality Sampling Stations.
Sugar Creek Sample Parameters Collected**
Station*Location Rivermile TOT Flow WQ LtBOD SOD
S 1 USGS gage 0.0 x x x
S2 Irwin WWTP effluent 0.1 x x x
S3 Taggart Creek x x
S4 Yorkmont Rd. 0.8 x x x x
S5 NC49 3.0 x x x
S6 Arrowood Rd. 4.8 x x x
S7 Coffey Creek x x
S8 Nations Ford Rd. 7.5 x x x
S9 Kings Branch x x
S9A Culp Rd. 9.2 x x x
S10 NC51 10.7 x x x x x
S 11 McCullough Branch x x
S12 Southern RR 11.9 x x x
S 13A Above Little Sugar 12.9 x x x
LO Upstream of effluent x x x
LI WWTP effluent x x
L1A Tributary x x
L2 Archdale Rd. x x x
L3 Starbrook Rd. x x x
L4 Sharon Rd. x x x x
L5 NC 51 x x x
L6 US 521 x x x
L7 At mouth x x x
S14 Above McAlpine 15.6 x x x x
M1 Upstream of WWTP x x x
M2 WWTP effluent x x x
M3 US Hwy 521 x x x x
M4 NC/SC State Line x x x x
M5 SR 2964 x x x x x
M6 At mouth x x x x
S15 Duplicate of M6 x x
S16 SC 674 16.8 x x x
S17 Steel Creek x x
S18 SC160 19.1 x x x x
* Stations beginning with S are on Sugar Creek or its tributaries, L - Little Sugar Creek,
M - McAlpine Creek.
**TOT - Time of Dye Travel, WQ - Water quality field parameters: DO, Temp.,
Conductivity, and pH. LtBOD - Long term BOD, SOD - Sediment oxygen demand.
4

Figure 2. Schematic of Sugar Creek Study Area including Stream Flow Estimates
and Major Wastewater Flow.
Taggart Creek
DA: 6.6 sq. mi.
QA: 7.3 cfs
7Q10: 0.3 cfs
Coffey Creek
DA: 10.5 sq. mi.
QA: 11 cfs
7Q10: 0.2 cfs
Steele Creek
DA: 32.8 sq. mi.
QA: 34 cfs
7Q10: 0.1 cfs
Irwin Creek WWTP
Design Flow: 23.2 cfs
Avg. Wastefiow: 20.0 cfs
DA: 30.7 sq. mi,
QA: 43 cfs
7Q10: 4.9 cfs
ct
Sugar Creek WWTP
Design Flow: 31 cfs
Avg. Wastefiow:.21 cfs
. DA: 40.8 sq, mi.
. QA: 47.4 cfs
7Q10: 3.4 cfs
McAlpine Creek WWTP
' Design Flow: 74.4 cfs
Avg. Wasteflow: 48.6 cfs
DA: 92.4 sq. mi.
QA: 139 cfs
7Q10: 1.3 cfs
Study Area Total:
DA: 262 sq. mi.
QA: 270 cfs
SQ10 15 cfs

Figure 3. Water Quality Sampling Stations.
Circled Stations indicate coincident Ambient Monitoring Stations.
Taggart Creek
S3
S4
Coffey Creek
S7
S1
c
co
S5
C)
m
m-
Irwin (Sugar) Creek
S2 Irwin Creek WWTP
Unnamed Trib
L1A
2\
L1 Sugar Creek WWTP
Kings Br.
S8
MuCullough Br.
Steele Creek
S11
S17
S12
S1 3A
S14
516
9
9A Little Sugar Creek
L5
5
McAlpine Creek
M2 McAlpine Creek WWTP
Ambient Station #02146800
6

Four ambient water quality monitoring stations exist in the study area (Figure 3).
These stations provide monthly water quality data on DO, temperature, and oxygen
consuming waste concentrations. Three of these stations are located below at least one of
the three major wastewater discharges. Review of the ambient data collected since 1984
indicates a general trend toward lower instream concentrations of oxygen consuming
wastes in the Sugar Creek watershed. Figure 4a-c presents NH3-N, BOD5, and dissolved
oxygen concentrations since 1984 at the bottom of the study area (Sugar Creek station 18,
ambient station # 02146800). Instream BOD5 and especially NH3 concentrations appear
to have dropped significantly since 1984 and 1986. Correspondingly, DO violations which
were frequent during the period 1984 -1987, have not been documented at ambient
station 02146800 since the summer of 1989. These trends are mirrored at the two other
ambient stations below the major WWTPs (see S10 and L6 on Figure 3), suggesting that
all three WWTPs have recently reduced loading of oxygen consuming wastes to the Sugar
Creek watershed.
Water quality data are also available from the Mecklenburg County Department of
Environmental Protection stream monitoring program. The County maintains stream
stations throughout the study area where it collects physical and chemical data
Data from monthly sampling at 12 stations throughout the study area were reviewed for
instream DO violations and oxygen consuming waste concentrations. Twice over the past
three years DO concentrations below 5.0 mg/1 were observed in the study area.
Nine benthic macroinvertebrate ambient monitoring (BMAN) stations exist in the
study area that have been sampled in the past four years. BMAN data are summarized
with a bioclassification rating ranging from poor to excellent, according to standard
methods (NC DEM 1990). Bioclassification rating for stations in the study area over the
past ten years are presented in Table 2. No station, above or below the major WWTPs,
received any rating higher than good/fair and many ratings of poor were recorded. In
general, the BMAN results suggest poor to fair water quality in the study area, possibly
with minor improvement in recent years.
Table 2. BMAN BioClassifications in the Study Area, 1983 - 1992.
Station Location BioClassification
1984 1985 1986 1987 1988 1989 1990 1991 1992
Irwin (Sugar) Ck near S2, above WWTP Poor Fair
Irwin (Sugar) Ck near S2, below WWTP Poor Fair
Irwin (Sugar) Creek at SR-2528 Fair
Sugar Creek at S18 Fair Poor Fair Poor Fair/Good
Little Sugar Creek at SR 3657 Poor Poor
McAlpine Creek above WWTP Poor Fair
McAlpine Creek at M3, below WWTP • Poor Fair
McCullough Br, (Try. to McAlpine) Poor
7

Figure 4a. Ammonia at Ambient Station 02146800 (S18) 1984 -
Present.
. _ _ Instream Target
0
Aug-83 Aug-84 Aug-85 Aug-86 Aug-87 Aug-88 Aug-89 Aug-90 Aug-91 Aug-92
Figure 4b. BOD at Ambient Station 02146800 (S18) 1984 -
Present.
20-
18-
16 -
14 -
12 -
10 -
8 - •:
6-
4-
149Cd
2-
0
Aug-83 Aug-84 Aug-85
ATiagrov.,
Aug-86 Aug-87
Aug-88 Aug-89 Aug-90 Aug-91 Aug-92
Figure 4c. Dissioved Oxygen at Ambient Station 02146800 (S18)
1984 - Present.
12 -
10-
gel\\
.•
8
6- - - - 41j- t ..`
4
2
0
Aug-83 Aug-84 Aug-85 Aug-86 Aug-87 Aug-88 Aug-89 Aug-90 Aug-91 Aug-92
-Instream Standard
8

M. MODEL DEVELOPMENT
A. Model Description
The relationship between oxygen consuming waste and dissolved oxygen
concentrations in the Sugar Creek watershed was evaluated through the development and
application of a QUAL2E-UNCAS water quality model. QUAL2E-UNCAS is a one-
dimensional, steady-state model, and assumes complete mixing in each water column
element. QUAL2E-UNCAS is supported by the EPA and offers the capability of
uncertainty analysis.
The streams were modeled using 30 reaches that describe stream segments
between each sampling station where TOT information was available. Each reach is
divided into computational elements 0.2 miles long. Because hydraulic and kinetic
parameters were often consistent over several reaches, the model actually describes 15
stream regions with unique hydraulic and kinetic properties, (See Appendix 1, data type
2).
B. Model Calibration
1. Background Input
Background water quality conditions upstream of the study area and at significant
tributaries throughout the study area were observed during the July 1990 intensive survey
on Sugar and Little Sugar creeks and the October 1986 intensive survey on McAlpine
Creek. The observed values for DO, Temperature, Conductivity, BODu, NH3-N, organic
nitrogen, and NOx were used as calibration model input for background surface water
conditions. These input data are listed in Appendix 1, data type 8 and 8k
Background water quality conditions for unmonitored tributaries and incremental
flow was assumed to be at 90% of DO saturation and to. have the following chemical
concentrations; 2.8 mg/1 CBODu, conductivity of 100 umhos/cm2, 0.40 mg/1 organic
nitrogen, 0.25 mg/1 NH3-N, and 0.2 mg/I NOx. These estimates are based upon
assumptions used in DEM's desktop modeling procedures. These background estimates
are described in DEM's standard operating procedures for desktop modeling and are
designed to reflect typical background surface water quality in North Carolina during low
flow conditions (DEM 1990).
2. Wastewater input
Wastewater flow and water quality parameters at each of the three major WWTPs
were collected during the July 1990 intensive survey. NH3 data for each facility were
collected from the facilities' self monitoring data. These data are presented in Appendix 1,
data type 10 and 10A and below.
9

Parameter Irwin Ck WWTP Sugar Ck WWTP McAlpine Ck WWTP
Flow (cfs):
CBOD (mg/1):
NH3-N (mg/1):
NOx (mg/1):
Org. N (mg/1):
DO (mg/1):
14.6 24.5
45.9 21.2
1.6 0.6
0.7 0.7
13.7 12.7
7.1 7.5
42.2
27.9
1.6
10.8
0.6
7.3
Eight minor permitted discharges exist in the Sugar Creek watershed, most of
them discharging to minor tributaries of the system. Of these, only four release oxygen
consuming wastes. At permit conditions, the three major facilities would make up over
99.5% of the wasteflow to the watershed. For these reasons, the minor facilities were not
considered during model calibration.
3. Hydraulics
Power functions were developed using flow data from the low and mid flow TOT
studies. For each reach, the average velocity was estimated as the length of the reach
divided by the time of travel. Average width was estimated as the mean widths at the
upstream and downstream river stations and any cross-section widths along the reach.
Average depth for each reach was estimated as the mean of the upstream and downstream
river station depths. Power functions were developed to model velocity, width, and depth
as dependent upon flow. The form of these power functions is presented below:
Velocity = Constant (Flow)(exponent) or V=aQb
Width = Constant (Flow)(exponent) W=eQf
Depth = Constant (Flow)(exponent) D Qd
Since velocity times width tunes average depth equals flow, it follows that the
exponents from the three power function sum to 1 and the product of the three constants
is 1. This provides a way to balance the equations so that the model can predict changes
in velocity, width, and depth by changes in flow without violating the assumption that flow
is equal to the cross -sectional area times velocity.
The power functions for velocity were developed first because of high confidence
in the estimates of reach length and time of travel. Also, time of travel measurements are
produced by dye traveling the length of each reach, producing an estimate that is
representative of the entire reach. This is not true of width and depth measurements
which were taken only at discrete points within each reach. The velocity power functions
developed are listed in Appendix 1, data type 5.
Because the power functions were developed from a regression of only two points
(mid and low flow studies) the predicted velocities are identical to observed velocities.
However, width and depth predicted values vary from observed values due the power
functions being forced to balance. Predicted widths and depths for the low flow TOT
study are listed below along with the observed range for each reach.
10

Width (ft) Depth (ft)
,StLeAM &girl Predicted Observed Range predicted Observed Range
Sugar 1 26.9 25 - 28 1.0 1.0 -1.1
Sugar 2 30.6 28 - 32 0.9 0.7 - 1.1
Sugar 3 32.2 30 - 34 0.8 0.7 - 1.0
Sugar 4 39.9 34 - 45 1.0 0.7 - 1.0
Sugar 5 42.9 40 - 45 1.0* 0.6 - 0.7
Sugar 6 33.65 27 - 40 1.25 0.7 - 2.0
Sugar 11 38.9 27 - 51 1.9 0.9 - 2.0
Sugar 15 60.2 51 - 69 1.6 0.9 - 2.0
Little 7 35.5 27 - 44
Little 8 32.4 27 - 43
Little 9 38.4* 43 - 63
Little 10 54.5 33 - 63
McAlpine 2 48.0 47 - 48
McAlpine 3 47.9* 34 - 47
McAlpine 4 31.6 29 - 34
* Indicates predicted value outside of observed range.
0.80
1.13
1.10*
1.10*
1.08
1.63*
1.65*
0.7 -1.6
0.7 - 1.3
0.6 - 0.7
0.6 - 0.7
In most cases, predicted values fall within the observed range. Depth appears to
be overestimated at the bottom of McAlpine Creek and especially Little Sugar Creek.
However, in each case the range of observed values is small (0.2 ft or less) and represents
a sample size of only 2. Because of the constraints placed on predicted depth by the
assumption that the power function balance, depth cannot be manipulated without
effecting predicted width or velocity. Given the limited depth data available and the
deeper upstream flow on Little Sugar Creek, it was felt:that the predicted depths are not
out of the range of possible depths.
It should be noted that the observed width and depth measurements were taken
during flow measurements. Because these sites were selected to allow for a satisfactory
flow measurement to be taken, they may not represent typical widths and depths of the
river reach.
Stream Flow Balance
Stream flow was modeled using the measured headwater and wastewater flows
and an incremental flow of 0.39 cfs/mile. This model -wide estimate of incremental flow
was estimated by equally distributing the excess flow measured at the bottom of the study
area, i.e. flow that was not accounted for by wastewater discharge or measured flows.
This estimate is expected to be biased; incremental flows should increase with drainage
area. However, because of the relatively small size of the watershed and limited flow data
collected under consistent flow conditions, one estimate of incremental flow for the entire
study area was considered to be the best estimate available. The resulting flow balance
was checked by comparing predicted versus observed conductivity values. Conductivity
11

was assumed to be a conservative substance, with no decay or Loss. Therefore,
conductivity estimates represent the results of flow, point source input, and transport.
The model did display the general trend of conductivity observed through the study area
(Figures 5a and 5b).
4. Rates/Kinetics
Nitrogen Series Calibration
Grab samples were used to determine nitrogen species concentrations upstream of
the study area on Sugar, Little Sugar, and McAlpine creeks, in the waste stream of each of
the three major wastewater treatment facilities, and at four sites throughout the study area
(S10, S 13A, M6, S18, (Figure 3)). Total nitrogen, Total Kjeldahl Nitrogen (TICN),
Ammonia, and NOx were reported. The upstream and wastewater concentrations were
input into the model and the nitrogen reaction coefficients were adjusted to reflect
instream nitrogen chemistry and the observed concentrations at the four downstream
stations.
Organic nitrogen was the first to be calibrated, followed by NH3 and then NOx.
This calibration resulted in the following rates for all stream reaches:
Organic Nitrogen Hydrolysis
Organic Nitrogen Settling
NH3 Oxidation
Benthos Source NH3
NO2 Oxidation
0.3 /day
0.0 /day
0.5 /day
0.0 /day
1.0 /day
These rates are consistent with EPA estimates of typical ranges for QUAL2E reaction
coefficients (Brown and Barnwell, 1987), and resulted in fairly good curve fits (Figures 6
to 9). The model does over predict NH3 along Sugar Creek (Figures 7a and 7b).
However, the predicted values are consistent with typical instream values observed in
Sugar Creek by the Mecklenburg County EPD. Benthic denitrification may be taking
place, resulting in low instream NH3 concentrations.
CBOD Calibration
CBOD was calibrated using long term BOD samples collected at the same sites as
for the nitrogen series data. Total long term BOD measurements were converted into
estimates of CBOD using Barnwell's model BODCURVE(Bamwell 1980). Calibration
resulted in an estimate of BOD decay of 0.4 /day for the upper section of Sugar Creek,
reaches 1 to 15, and 0.3 /day for the lower reaches of the model. This reach specific
BOD decay estimate was felt to be appropriate due to changes in the reactivity of BOD
residuals far downstream of the Irwin WWTP. No removal of BOD by settling was
incorporated in the model. These estimates produced a predicted BOD curve that
followed the general observed pattern (Figure 10a and lOb).
12

Figure 5a. Predicted and Observed Conductivity In Sugar
Creek, July 24, 1990.
800
700
8500 x xx
� x
`' 400 x x x x
x
200
0
U 100
5 10 1 20 25
Irwin Ck WWTP Little Sugar Ck 41McAlpine Ck
Distance (miles)
Predicted
x Observed
Figure 5b. Predicted and Observed Conductivity in Little Sugar
and McAlpine Creeks.
800 -
2700- 0
00
v
`6_
500
• as .. q� _ ■ ■ 1
2.
i300
f
200 — •
0
0 100
0 t r c c t
0 t 5 10 T 15 20 25
Sugar Ck WWTP McAlpine Ck WWTP
Distance (miles)
13
L Sugar Predicted
■ L Sugar Observed
—� McAlpine Predicted
o McAlpine Observed

Figure 6a. Predicted and Observed Organic Nitrogen
Concentrations in Sugar Creek, July 24, 1990.
1.6
1.4
'1'
0.2
0
0
•
♦
5 10
Distance (miles)
15
20
25
Figure 6b. Predicted and Observed Organic Nitrogen in little
Sugar and McAlpine Creeks.
1.6 -
1.4 -
1.2 -
F 1
E 0.8
O 0.6-
04-
0.2
0
0
5 10 15
Distance (miles)
14
20
25
Predicted
• Observed
■
0
L Sugar Predicted
L Sugar Observed
McAlpine Predicted
McAlpine Observed

Figure 7a. Predicted and Observed Ammonia Concentrations in
Sugar Creek, July 24, 1990.
1.6
1.4
1.2
1
0.8
=• 0.6�
0.4
0.2 •
0 • •
0 5 10 15 20 25
Distance (miles)
Predicted
• Observed
Figure 7b. Predicted and Observed Ammonia in Little Sugar and
McAlpine Creeks.
1.6
1.4
1.2
S 1
0.8
I 0.6
0.4
0.2
0
0
5
10
15
Distance (miles)
15
20
25
L Sugar Predicted
■ L Sugar Observed
- McAlpine Predicted
o McAlpine Observed

Figure 8a. Predicted and Observed Nitrate and Nitrite
Concentratlons in Sugar Creek, July 24, 1990.
12
e 10
•
8 •
�, •
O 6+
O 4t
Z 2
0
0 5 10 15 20 25
Distance (miles)
Figure 8b. Predicted and Observed Nitrate and Nitrite in Little
Sugar and McAlpine Creeks.
5
10
15
Distance (miles)
16
20
.
25
Predicted
• Observed
L Sugar Predicted
• L Sugar Observed
McAlpine Predicted
• McAlpine Observed

Figure 9a. Predicted and Observed Total Nitrogen
Concentrations in Sugar Creek, July 24, 1990.
• • •
0 5 10 15 20 25
Distance (rntles)
Predicted
• Observed
Figure 9b. Predicted and Observed Total Nitrogen In Little Sugar
and McAlpine Creeks.
12
10
E 8
I 6
4
2
0
0 5 10 15 20 25
Distance (miles)
17
L Sugar Predicted
■ L Sugar Observed
McAlpine Predicted
• McAlpine Observed

Figure 10a. Predicted and Observed CBOD Concentrations in
Sugar Creek, July 24, 1990.
35
30
20
g.
u 10 X
s
x
0 AL
5 10 1 20 25
kwln Ck WWTP little Sugar Ck I Ck
Distance (miles)
Predicted
x Observed
Figure 10b. Predicted and Observed CBOD Concentrations in
Little Sugar and McAlpine Creeks.
35
30
2025
15
s10
5
0
0 +5
Sugar Ck WWTP
10+ 15 20 25
McAlpine Ck WWII)
Distance (mites)
18
L Sugar Predicted
O L Sugar Observed
McAlpine Predicted
o McAlpine Observed
•

DO Calibration
Stream Reaeration
Stream reaeration was estimated by the method developed by Langbien and
Durum (1967). This method estimates the reaeration rate (K2) with the following
equation:
K2 = 3.3u/d1.33 * 2.31
where u = mean velocity, ft/sec.
d = mean depth, ft.
This method was developed from a large data base including data from a wide
range of stream sizes and so is expected to perform well over a wide range of river flows.
Sediment Oxygen Demand
SOD rates were measured in situ at four locations throughout the study area.
Two measurements were taken on Sugar Creek, at stations S4 and S 10, 0.5 and 12 miles
below the Irwin Creek WWTP (Figure 3). One SOD measurement was taken on Little
Sugar Creek at station L4 and one on McAlpine Creek at Station M5 (Figure 3). Station
S4 on Sugar Creek had the highest measured average SOD rate of 0.13 g/ft2/day. Each
of the other three SOD sites had average SOD rates of 0.1 g/ft2/day. The higher SOD
rate was applied to Sugar Creek reaches 1 to 11 (From station S 1 to 9A, see Figure 3).
Final Calibration Results for DO
Predicted and observed DO concentrations are presented in Figures l la and 11b.
The model over predicts DO in McAlpine Creek by 0.9 mg/1, and therefore downstream
in McAlpine Creek as well. However, the model does reproduce the steep DO sag
observed in McAlpine Creek, and without more data points it was assumed that the
existing velocity and reaeration estimates were the best information available.
Observed DO concentrations on Little Sugar Creek were highly variable, making
calibration difficult. The predicted DO curve through the scatter was selected as the best
fit (Figure 11b).
C. Model Application
1. Background Conditions
Design conditions for allocation model runs were defined as 7Q10 flows (see
Figure 2), 75th percentile temperature for the Sub -basin (26 degrees C.), 90% DO
saturation, and the following chemical concentrations; 2.8 mg/1 CBODu, conductivity of
100 umhos/cm2, 0.40 mg/1 organic nitrogen, 0.25 mg/I NH3-N, and 0.2 mg/1 NOx. These
background estimates are described in DEM's standard operating procedures for desktop
modeling and are designed to reflect typical background surface water quality in North
Carolina during low flow conditions (DEM 1990).
19

Figure 11a. Predicted and Observed DO Concentrations In
Sugar Creek, July 24, 1990.
8
7
6
Q5
E4
0 3
2
1
0
•
•
• •
5 10 1 20 25
tIrwin C'k WWTP McAlpine Ck
Distance (miles)
Figure 11 b. Predicted and Observed DO in little Sugar and
McAlpine Creeks.
8
7
6
c5
E4
0 3
0
2-
1
0. 4 $ 1 i $
0 5 10 15 20 25
Distance (miles)
20
Predicted
• Observed
L Sugar Predicted
• L Sugar Observed
McAlpine Predicted
o McAlpine Observed

2. Wastewater Conditions
Effluent characteristics of facilities discharging to the study area were modeled
using current permit limits and permit limits due to apply in the future. Permit limits for
DO, BOD, and NH3 for the three major facilities are presented in Table 3a .
Table 3a. Permit Limits for Major Facilities Discharging to the Sugar Creek Watershed.
Facility. Condition Flow MGD1 $0D5 (mgJ1) NH3-N (mg01 1a0 (mg/ll
Irwin Creek, before 1995 15 16 8 5
Irwin Creek, after 1995 15 5 1 6
Sugar Creek, before expansion 14.7 21 8 5
Sugar Creek, after expansion 20.0 5 1 6
McAlpine Creek, before expansion 40 8 2 6
McAlpine Creek, after expansion 48 4 1 6
Table 3b. Actual Discharge Conditions for Major Facilities Discharging to the Sugar Creek Watershed.
1991 April -October average wasteflow, BOD, and NH3, and minimum monthly DO.
E�11ity Flow MGDI DODS (mg/11 NH3 N (pig/11 DODO
Irwin Creek WWTP
Sugar Creek WWTP
McAlpine Creek WWTP
12.84
13.60
31.83
8.89
7.83
2.96
0.80
1.56
0.26
6.0
6.8
7.9
For model input, BOD5 values were converted to CBODu estimates using
CBODu to GODS ratios. CBODu/BOD5 ratios were calculated from LtBOD samples
taken from the effluent of each major WWTP. The CBODu/BOD5 ratios calculated were
3.5 for the Irwin Creek WWTP, 2.0 for the Sugar Creek WWTP, and 4.1 for the
McAlpine Creek WWTP.
3. Results
Predicted DO profiles of Sugar Creek for existing permit conditions, actual
discharge conditions, and future permit conditions are presented in Figures 12a-c. Figures
13a-c show the DO profiles on Little Sugar and McAlpine creeks as well. Clearly, present
permit conditions do not protect the stream standard. A severe DO sag, predicted to
cause DO violations at 7Q10 conditions, exists below each of the three major facilities in
the study area. However, if each facility was modified to meet the permit limits specified
in part B of each permit, no DO violations in the watershed are predicted by the model
(Figure 12c and 13c).
Actual discharge conditions, represented by the average summer 1991 discharge
monitoring data, are not predicted to cause severe DO sags, although the sag below Irwin
Creek WWTP is predicted to result in a DO violation during 7Q10 conditions (Figure 12a
and 12b). All three major facilities are presently discharging BOD and NH3
concentrations below their permit limits (Tables 3a and 3b). However, water quality
21

7
Figure 12a. Predicted DO Profile in Sugar Creek for Existing Permit Umits
5
10 15
Distance (miles)
20
DO Standard
Figure 12b. Predicted DO Profile in Sugar Creek for Current Discharge
Conditions
25
8 -
7 1
6 _`
A
S 5 • DO Standard
0 3-
2-
1-
0•
0 5 10 15 20 25
Distance (miles)
8
7
6-
t, 5
E 4-
0 3-
2-
1-
0.
0
Figure 12c. Predicted DO Profile in Sugar Creek for Future Permit Umits
DO Standard
5
10 15 20 ' 25
Distance (miles)
22

Figure 13a. Predicted DO Prpfile in Sugar, Little Sugar, and McAlpine Creeks
for Existing Permit Limits
8
7
6
5
0 3
2
1
0
DO Standard
0 5 10 15 20 25
Distance (miles)
Sugar Creek
Little Sugar
McAlpine
Figure 13b. Predicted DO Profile in Sugar, Uttle Sugar, and McAlpine Creeks
for Current Discharge Conditions
8-
7
6
Z, 5 - DO Standard
E 4 -
0 3•
2-
1-
0, � 1
0 5 10 15 20 25
Distance (miles)
Sugar Creek
Little Sugar
McAlpine
Figure 13c. Predicted DO Profile in Sugar, Uttle Sugar, and McAlpine Creeks
for Future Permit Umits
E
8
6
4
0
0 2
0
-DO Standard
0 5 10 15 20 25
Distance (miles)
23
Sugar Creek
Uttle Sugar
McAlpine

standards must be protected during all discharge conditions, not just the summer average.
Therefore, it can not be concluded that current conditions, even with current WWTP
operation methods, protect water quality in the Study Area.
Ammonia concentrations also are a potential threat to water quality in the study
area. Since the three major WWTPs dominate flow during low flow conditions, NH3
toxicity is a serious concern at the existing permit limits of 8 mg/1 for hwin Creek and
Sugar Creek WWTPs and 2 mg/1 at McAlpine WWTP. Under actual discharge
conditions, as modeled by the average of summer 1991 discharge monitoring data, NH3 is
predicted to exceed the instream target on Little Sugar Creek (Figure 14a). If all three
major facilities were to meet NH3 limits of 1 mg/1, as specified in part B of their current
NPDES permits, no instream NH3 toxicity is predicted (Figure 14b).
D. Sensitivity Analysis
A first order error analysis was used to determine the relative sensitivity of the
model to parameter estimates. QUAL2E-UNCAS was run to determine which inputs
most influenced model estimates of DO, BOD, and NH3. Every model parameter was
independently varied by 5 percent and the response in terms of DO, BOD, and NH3 was
recorded at five locations throughout the study area. The five locations chosen to
represent model sensitivity are: 1) Sugar Creek 1 mile below the Irwin Creek WWTP
(S4), 2) the DO sag on Sugar Creek 8 miles below the Irwin Creek WWTP (S8), 3) At the
bottom of Little Sugar Creek (L7), 4) at the mouth of McAlpine Creek (M6), and 5) at the
bottom of the study area (S18), (see Figure 3).
The sensitivity of predicted DO concentrations to model perturbation is presented
in Table 4a. Predicted DO was most sensitive to the initial temperature of the stream.
This sensitivity is expected due to the relationship between temperature and DO saturation
and is not a limitation to the predictive ability of the model. Predicted DO was also
sensitive to the equations used to describe the hydraulics. This is also not surprising since
the reaeration rate is determined by the hydraulics. DO at the mouth of McAlpine Creek
showed sensitivity to point load DO, suggesting that the entire 4 miles of McAlpine Creek
below McAlpine Creek WWTP is sensitive to that facilities effluent DO concentration.
The model also showed moderate sensitivity to BOD decay and SOD rates, and point load
flow and point load BOD.
The sensitivity of predicted BOD concentrations is presented in Table 4b. Because
the system is dominated by wastewater flow, the model is most sensitive to point load
BOD concentrations. As with DO, BOD is sensitive to the initial temperature and the
equations that describe velocity. Point load flow and BOD decay rate also have some
influence on predicted BOD concentrations. In general, predicted BOD appears to be
robust since much of its sensitivity is due to parameters for which confidence in estimates
is high.
The sensitivity of predicted NH3 concentrations is presented in Table 4c. As with
DO, NH3 is most sensitive to initial temperature. Point load flow and concentrations and
the velocity equations are also important to NH3 estimates. One parameter for which the
confidence in its estimate is low, NH3 decay, plays a significant role in NH3 sensitivity.
24

Figure 14a. Predicted Ammonia Profile in Sugar, Little Sugar,
McAlpine Creeks for Current Discharge Conditions
1"`"
i
Instream Target
5 10 15 20 25
Distance (miles
Sugar Creek
Little Sugar
McAlpine
Figure 14b. Predicted Ammonia Profile in Sugar, Little Sugar,
McAlpine Creeks for Future Permit Conditions
0.2
0
0
Instream Target
5 10 15 20 25
Distance (miles
25
Sugar Creek
Little Sugar
McAlpine

TABLE 4a. FIRST ORDER ERROR ANALYSIS: RESPONSE NO. 1
A. TITLE OF DATA SET.
CMUD - SUGAR CREEK BASIN
Calibration 8/5/92
B. RESPONSE VARIABLE: DO
C. NORMALIZED SENSITIVITY COEFFICIENT MATRIX: DO
LOCATION
INPUT VAR
REACH 3 REACH 11 REACH 22 REACH 27 REACH 30
ELEMENT 1 ELEMENT 2 ELEMENT 17 ELEMENT 3 ELEMENT 20
INITTEMP -0.535 -1.572 -1.435 -1.559 -1.188
EXPOQV-B 0.099 0.638 0.603 0.624 0.436
EXPOQH-D -0.042 -0.087 -0.214 -0.495 -0.835
COEFQH-C -0.083 -0.376 -0.278 -0.306 -0.343
COEFQV-A 0.102 0.347 0.28 0.385 0.221
PTLDDO 0.565 0.025 0.017 0.424 0.038
PTLDBOD -0.044 -0.116 -0.099 -0.236 -0.131
SOD RATE -0.053 -0.18 -0.163 -0.118 -0.097
BOD DECA -0.049 -0.149 -0.081 -0.219 -d.095
PTLDFLOW -0.011 0.105 0.094 0.032 -0.067
HWTRDO 0.124 0.005 0.002 0.005 0.0
OTHER INPUTS WITH NORMALIZED SENSITIVITY COEFFICIENTS LESS THAN 0.10 EACH.
NH3OXYUP NO2OXYUP AGYOXYPR AGYOXYUP AGYNCON
AGYGROMX AGYRESPR NHALFSAT AGYEXTLN AGYEXTNL
LSATCOEF LAVGFACT NUMBDLH TDYSOLAR NHIBFACT
TC/BODDC TC/BODST TC/REAER TC/SOD TC/NH2DC
TC/NH2ST TC/NH3DC TC/NH3SC TC/NO2DC TC/PRGDC
TC/PRGST TC/PO4SC TC/ALGRO TC/ALRES TC/ALSET
MANNINGS NH2 DECA NH3 DECA NO2 DECA CHLA/ART
LTEXTNCO INCRFLOW INCRTEMP INCRDO INCRBOD
INCRNH2N INCRNH3N INCRNO2N INCRNO3N HWTRFLOW
HWTRTEMP HWTRBOD HWTRNH2N HWTRNH3N HWTRNO2N
HWTRNO3N PTLDTEMP PTLDNH2N PTLDNH3N PTLDNO2N
PTLDNO3N

TABLE 9 b . FIRST ORDER ERROR ANALYSIS: RESPONSE NO. 2
A. TITLE OF DATA SET.
CMUD - SUGAR CREEK BASIN
Calibration 8/5/92
B. RESPONSE VARIABLE: BOD
C. NORMALIZED SENSITIVITY COEFFICIENT MATRIX: BOD
LOCAT ION
INPUT VAR
REACH 3 REACH 11 REACH 22 REACH 27 REACH 30
ELEMENT 1 ELEMENT 2 ELEMENT 17 ELEMENT 3 ELEMENT 20
PTLDBOD 0.906 0.898 0.927 0.995 0.967
INITTEMP -0.057 -0.638 -0.641 -0.257 -0.747
EXPOQV-B 0.027 0.485 0.542 0.176 0.608
BOD DECA -0.026 -0.295 -0.296 -0.117 -0.348
COEFQV-A 0.024 0.276 0.277 0.108 0.33
PTLDFLOW 0.094 0.229 0.194 0.059 0.197
OTHER INPUTS WITH NORMALIZED SENSITIVITY COEFFICIENTS LESS THAN 0.10 EACH.
TC/BODDC TC/BODST COEFQH-C EXPOQH-D MANNINGS
INCRFLOW INCRTEMP INCRBOD HWTRFLOW HWTRTEMP
HWTRBOD PTLDTEMP

TABLE 4c. FIRST ORDER ERROR ANALYSIS: RESPONSE NO. 3
A. TITLE OF DATA SET.
CMUD - SUGAR CREEK BASIN
Calibration 8/5/92
B. RESPONSE VARIABLE: NH3N
C. NORMALIZED SENSITIVITY COEFFICIENT MATRIX: NH3N
LOCATION
INPUT VAR
REACH 3 REACH 11 REACH 22 REACH 27 REACH 30
ELEMENT 1 ELEMENT 2 ELEMENT 17 ELEMENT 3 ELEMENT 20
INITTEMP -0.119 -1.128 -1.457 -0.791 -1.767
PTLDNH3N 0.977 0.826 0.783 - 0.974 0.819
EXPOQV-B 0.025 0.394 0.586 0.295 0.763
NH3 DECA -0.036 -0.39 -0.505 -0.221 -0.579
COEFQV-A 0.021 0.222 0.296 0.179 0.405
PTLDFLOW 0.17 0.277 0.256 0.088 0.246
TC/NH3DC -0.016 -0.171 -0.222 -0.096 -0.257
PTLDNH2N 0.012 0.149 0.203 0.023 0.168
NH2 DECA 0.013 0.148 0.193 0.023 0.155
HWTRFLOW -0.168 -0.142 -0.074 -0.014 -0.049
OTHER INPUTS WITH NORMALIZED SENSITIVITY COEFFICIENTS LESS THAN 0.10 EACH.
NH3OXYUP NO2OXYUP AGYOXYPR AGYOXYUP AGYNCON
AGYGROMX AGYRESPR NHALFSAT AGYEXTLN AGYEXTNL
LSATCOEF LAVGFACT NUMBDLH TDYSOLAR NHIBFACT
TC/BODDC TC/BODST TC/REAER TC/SOD TC/NH2DC
TC/NH2ST TC/NH3SC TC/NO2DC TC/PRGDC TC/PRGST
TC/PO4SC TC/ALGRO TC/ALRES TC/ALSET COEFQH-C
EXPOQH-D MANNINGS BOD DECA SOD RATE NO2 DECA
CHLA/ART LTEXTNCO INCRFLOW INCRTEMP INCRDO
INCRBOD INCRNH2N INCRNH3N INCRNO2N INCRNO3N
HWTRTEMP HWTRDO HWTRBOD HWTRNH2N HWTRNH3N
HWTRNO2N HWTRNO3N PTLDTEMP PTLDDO PTLDBOD
PTLDNO2N PTLDNO3N
28

To quantify the sensitivity of the model to parameter perturbation, a Monte Carlo
analysis was run. This analysis involved independently varying each model parameter over
a normal distribution defined by the coefficient of variance for each variable. The
coefficient of variance for most parameters was assumed to be equal to typical values as
reported by the EPA(Brown and Barnwell 1987). However, for parameters that were
identified in the First Order Analysis as having a relatively important part in BOD, NH3,
or DO, sensitivity was considered separately. The following coefficients of variance were
used for sensitive parameters:
Parameter
Velocity Coefficient
Velocity Exponent
Width Coefficient
Width Exponent
Ammonia Decay
BOD Decay
Point Load Flow
Point Load BOD
SOD rate
QUAL2E abbreviation Coefficient of Variance (°h)
COEFQV-A
EXPOQV-B
COEFQH-C
EXPOQH-D
NH3 DECA
BOD DECA
PTLDFLOW
PTLDBOD
SOD RATE
5
5
5
5
20
20
5
10
5
Ammonia and BOD decay were given large coefficients of variance because they
were not measured directly in the field. The default estimates of coefficients of variance
are listed in Appendix 2.
500 Monte Carlo simulations were run with the future permit wastewater
conditions, and statistics describing the effect on predicted DO concentrations were
calculated. DO estimates were estimated at the five locations in the First Order Analysis.
The results give the following estimates of model error:
Station, location DO estimate_ with 95% confidence interval (mg/1)
S4, 1 mile below Irwin Creek WWTP
S8, DO sag below Irwin Ck. WWTP
L7, mouth of Little Sugar Creek
M6, mouth of McAlpine Creek
S18, bottom of the study area
6.1 ±.4
5.7 ± .7
6.0 ± .7
5.1. ± .7
6.2 ± .6
(5.7 - 6.5)
(5.0 - 6.4)
(5.3 - 6.7)
(4.4 - 5.8)
(5.6 - 6.8)
The 95% confidence interval for DO at the sag below Sugar Creek WWTP
includes concentrations below the stream standard. The confidence intervals of DO
estimates toward the bottom of the study area (S8, L7, M6, and S18) appear to be
relatively constant, ± about 0.7 mg/1. This suggests that each region of the model is
equally sensitive to parameter error. Given the assumptions about the likely range of error
in parameter estimates, this analysis suggests that the predicted DO profile is a sound tool
for evaluating possible DO violations throughout the study area with the exception of the
lower end of Little Sugar Creek. If parameter error is as high as estimated by the
29

coefficients of variation listed in Appendix 2, the models prediction that future limits at
Sugar Creek WWTP will protect water quality in Little Sugar Creek should be considered
with caution.
IV. SUMMARY AND RECOMMENDATIONS
The results of this study support the current management plan now in place for the
major facilities in the Sugar Creek watershed. Current permit limits do not protect water
quality in the study area. However, each major facility has new permit limits that will
apply to any future modification. These new limits will dramatically lower BOD loading
to the system and so are predicted to prevent DO from dropping below the instream
standard during 7Q10 conditions.
Results of the study suggest that the current management plan and new permit
limits for the Irwin Creek, Sugar Creek, and McAlpine Creek WWTPs are consistent with
the goal of improving water quality in the Sugar Creek watershed. Once the new permit
limits are met at the three major WWTPs, the model predicts that the discharge of oxygen
consuming wastes will not result in water quality problems in the Sugar Creek watershed.
This effort will be a significant step towards the goal of removing Irwin, Sugar, Little
Sugar, and McAlpine Creeks from the State's 303d list of impaired waters. Until the new
permit limits are in effect, all three major CMUD facilities should be encouraged to
continue their efforts to reduce BOD loading to the Sugar Creek Watershed.
This calibrated water quality model of the Sugar Creek watershed can be used for
management decisions in sub -basin 03-08-34 as part of basinwide planning and can be
incorporated into the April 1995 Catawba River basinwide management plan.
30

REFERENCES
Barker, R.G., B.C. Ragland, J.F. Rhinehardt, and W.H. Eddins, 1991. Water Resources
Data, North Carolina Water Year 1991. U.S. Geological Survey water -data report
NC-91-1, Raleigh, NC.
Barnwell, T.O. Jr., 1980. Least Squares Estimates of BOD Parameters. American
Society of Civil Engineers, EE6.
Brown, L.C., and T.O. Barnwell Jr., 1987. The Enhanced Stream Models QUAL2E and
QUAL2E-UNCAS: Documentation and User Model. U.S. EPA, Athens, Georgia.
DEM, 1990. Instream Assessment Standard Operating Procedures.
Langbien, W.B. and W.H. Durum, 1967. The Aeration Capacity of Streams, U.S.
Geological Survey, Washington, DC, Circ. 542.
North Carolina Department of Environment, Health, and Natural Resources, DEM WQ,
1990. Water Quality Progress in North Carolina, 1988-1989, 305(b) Report.
North Carolina Department of Environment, Health, and Natural Resources, DEM WQ,
1991. Biological Assessment of Water Quality in North Carolina Streams: Benthic
Macroinvertebrate Data Base and Long Term Changes in water Quality, 1983-
1990.
31