NC0021253_Speculative Limits_20090408

NPDES DOCUMENT SCANNING COVER SHEET
NC0021253
Havelock 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
Renewal Application
Instream Assessment (67b)
Speculative LimitsM
Environmental Assessment (EA)
Document Date:
April 8, 2009
This document is printed on reuse paper - ignore any
content on the reverse elide

AIM
NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
April 8, 2009
Mr. James W. Freeman
City Manager
City of Havelock
Post Office Box 368
Havelock, North Carolina 28532
Subject: Speculative Limits for Havelock WWTP
Expansion and discharge relocated to
the Neuse River estuary
Craven County
Dear Mr. Freeman:
This letter is in response to your request for speculative effluent limits for a proposed expansion of
Havelock's WWTP (NC0021253) from 1.9 mgd currently permitted to 3.5 mgd, with increments of
2.25 and 2.8 mgd. The discharge will be through a diffuser to the Neuse River estuary between
Slocum Creek and Hancock Creek through a new outfall 001. The discharge location will be
approximately 0.5 miles east of the existing US Marine Corps Air Station at Cherry Point WWTP
discharge. The expanded facility would be located at the Havelock Wastewater Treatment Plant off
North Jackson Drive in Havelock, Craven County, in the Neuse River Basin. North Carolina
Regulation 15A NCAC 2B .0203 states "...effluent limitations ...for direct discharges of waste ...will
be developed ...such that the water quality standards and the best usage of receiving waters and all
downstream waters will not be impaired."
The Neuse River at the proposed discharge site is classified SB, Sw, NSW. Class SB waters are
protected for primary recreation and any other usage specified by SC classification. The secondary
classification as swamp waters (Sw) indicates that the water has swamp characteristics, such as
low dissolved oxygen, and a very low flow rate. The Nutrient Sensitive Water (NSW) designation is
for waters that are experiencing or are subject to excessive growths of microscopic or macroscopic
vegetation that impair the use of the water for its best usage. The term "nutrient" includes total
phosphorus and total nitrogen.
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604
Phone: [phone] FAX: [phone] \ Customer Service:1-877-623-6748
Internet: www.ncwaterquality.org
An Equal Opportunity \ Affirmative Action Employer
Nose Carolina
�tura!!y

Based on available information, speculative effluent limits for the proposed discharge of up to 5.5
mgd to the Neuse River are presented in Table 1. These speculative limits were developed in
accordance with the Neuse River Nutrient Sensitive Waters rules found in 15A NCAC 02B.0232
through .0240 for Total Nitrogen and Total Phosphorus.
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 application.
Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an
NPDES permit will be issued with these speculative limits. Final decisions can only be made after
the Division receives and evaluates a formal permit application for the City's proposed discharge. In
accordance with the North Carolina General Statutes, the practicable wastewater treatment and
disposal alternative with the least adverse impact on the environment is required to be
implemented. Therefore, as a component of all NPDES permit applications for new or expanding
flow, a detailed engineering alternatives analysis (EAA) must be prepared. The EAA must justify
requested flows, and provide an analysis of potential wastewater treatment alternatives.
Alternatives to a surface water discharge, such as spray/ drip irrigation, wastewater reuse, or
inflow/ infiltration reduction, are considered to be environmentally preferable. A copy of the EAA
requirements is attached to this letter. Permit applications for new or expanding flow will be
returned as incomplete if all EAA requirements are not adequately addressed. If you have any
questions regarding these requirements, please contact the DWQ NPDES unit at 919-807-6404.
State Environmental Policy Act jSEPA) 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 7Q 10 flow conditions. For existing discharges,
significant impact is defined as an expansion of > 500,000 gpd additional flow. Since your
proposed facility is for > 500,000 gpd 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 POTW until the Division has
approved the SEPA document and sent a Finding of No Significant Impact (FONSI) to the
State Clearinghouse for review and comment. A SEPA Environmental Assessment (EA) should
contain a clear justification for the proposed project. If the SEPA EA demonstrates that the project
may result in a significant adverse effect on the quality of the environment, you must then prepare
a SEPA EIS (Environmental Impact Statement). Since your proposed facility is subject to SEPA,
the EAA requirements discussed above will need to be folded into the SEPA document. The
SEPA process will be delayedif all EAA requirements are not adequately addressed. If you
have any questions regarding SEPA EA/ EIS requirements, please contact Hannah Stallings with
the DWQ Planning Branch at [phone].

Should you have any questions about these speculative limits or NPDES permitting requirements,
lease feel free to contact Jim McKay at [phone].
Sincerely,
Gil Vinzani, P.E.
Supervisor, Eastern NPDES Program
Attachment: EAA Guidance Document
cc: (without attachment)
• Washington Regional Office/Surface Water Protection Section
• Central Files
• NPDES Permit Files
• Hannah Stallings
• Tetra Tech/ P.O. Box 14409/ Research Triangle Park, NC 27709/ Attention: H. Thomas
Tant, P.E. (With Attachment)

Table 1. Speculative Effluent Limitations for Havelock WW1? Discharging to the
Neuse River at outfall 001 at 3.5 mgd
Effluent Characteristics
SPECULATIVE EFFLUENT LIMITS
Monthly Average
Weekly Average
Daily Maximum
Flow
3.5 MGD
`>
BOD, 5-day, 200 C (April 1- October
31)
5.0 mg/L
7.5 mg/L
BOD, 5-day, 200 C (November 1-
March 31)
10.0 mg/L
'15 mg/L
Total Suspended Solids
30.0 mg/L
45.0 mg/L
Enterococci (geometric mean)
35/ 100 ml
276/ 100 ml
pH
Between 6.8 and 8.5 S.U.
Total Residual Chlorine
13 ug/L
Dissolved Oxygen
Minimum 5.0 mg/ L
NH3 as N (April 1- October 31)
1.0 mg/L
3.0 mg/L
NH3 as N (November 1- March 31)
2.0 mg/L
6.0 mg/L
Total Nitrogen 1
(NO3-N + NO2-N + TKN)
21,400 pounds per year
Total Phosphorus
1.0 mg/L
Whole Effluent Toxicity 2
Notes:
1. TN mass load of 21,400 lb/year would remain in effect for the facility.
2. Chronic Toxicity (Ceriodaphnia) P/ F at 90%, months to be determined.
3. The same limits also apply at flow rates of 2.25 and 2.8 mgd.

Total Nitrogen — The nitrogen limit represents the City's annual allocation for total nitrogen,
pursuant to the Neuse River Basin Nutrient Management Strategy (T15A NCAC 02B.0234). The
Strategy also gives dischargers in the basin the option of forming a group compliance association
and working collectively to meet the overall nitrogen reduction target. The rule waives the individual
nitrogen permit limits for any discharger that joins an approved association. The association then
becomes responsible for meeting the collective allocation of its members.
The proposed total nitrogen limit of 21,400 lb/yr reflects the existing limit for the Havelock facility.
The limit represents a nitrogen "cap" and does not increase with increasing flows. The 21,400 lbs/yr
allocation is equivalent to 2.0 mg/L for the flow of 3.5 MGD. The Division of Water Quality
considers 3.0 mg/L to be the Best Available Technology for TN. The City must evaluate other
options such as pursuing water reuse or other non -discharge options in order to reduce the amount
of nitrogen discharged to the receiving stream. Alternately, the City can purchase an allocation
from existing dischargers or can purchase allocation from the Ecosystem Enhancement Program,
which uses the payment to fund offsetting non -point nutrient reductions. The City must acquire
sufficient nutrient allocation for a 30-year period prior to application for an NPDES permit
modification.
Total Phosphorus - The total phosphorus limit of 1.0 mg/L represents the limit for expanding
facilities pursuant to the Neuse River Basin Nutrient Management Strategy (T15A NCAC
02B.0234(8) (g)).

CITY OF HAVELOCK
Post Office Box 368
Havelock, N.C. 28532
January 12, 2009
Mr. Gil Vinzani, Supervisor
Eastern NPDES Permits Program
Division of Water Quality
N.C. Department of Environment and
Natural Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: Speculative Limits
Havelock WWTP
Havelock, North Carolina
NPDES Permit No. 0021253
Dear Mr. Vinzani:
JAN 1 3 2009
The City of Havelock is planning for the expansion of its wastewater treatment plant
and is considering relocation of its existing discharge within the Neuse River basin to
improve surface water quality. The wastewater treatment plant is currently permitted for
1.9 mgd. The City's wastewater discharge is currently to the East Prong of Slocum Creek,
and the City is considering relocation of this expanded discharge to the main body of the
Neuse River. The possible expansion of the wastewater treatment plant to a capacity of
3.5 mgd is contemplated for the planning period with two separate intermediate
expansions from the current 1.9 mgd to 2.25 mgd and 2.8 mgd.
We are hereby requesting speculative NPDES discharge limits for expanded flows
of 2.25 mgd, 2.8 mgd, and 3.5 mgd to the Neuse River. The location of the proposed
discharge is described in the attached Proposed Relocation of the Havelock Wastewater
Treatment Plant Discharge report prepared for Havelock by Tetra Tech, and dated
December 23, 2008. Three (3) copies of the attached report has been provided for your
reference.
This report includes modeling results of the relocated discharge to the Neuse River
at the location proposed and at the range of discharge flows considered. This modeling
work also included the assumption that there would be no increase in mass nutrient load
with the expanded discharge above that currently permitted. This work was completed by
the City of Havelock following coordination with you and other Division of Water Quality
Phone [phone] www.havelocknc.com Fax [phone]

(DWQ) staff at the kick-off meeting on August 14, 2007. Subsequent to this meeting, there
has been other communication with DWQ modeling staff to ensure certain approaches
used during modeling were consistent with DWQ's preferences.
We are appreciative of the assistance and time you and other Division staff have
provided to date, as well as your review of this request for speculative limits. Given that
the City has completed the significant modeling effort to facilitate your review of this
request and provide a basis for developing these limits, we extend the offer to you or other
Division staff to meet to review the results of this modeling effort. Please feel free to
contact me at [phone] or Tom Tant with Hazen and Sawyer, our lead engineering
consultant, at [phone].
Enclosure
cc: Pete Deaver, Public Utilities Director
H. Thomas Tant, P.E., Hazen and Sawyer

Proposed Relocation of the
T Havelock Wastewater Treatment
Plant Discharge
1 3 2009
Prepared for:
City of Havelock, North Carolina
Prepared by:
TETRA TECH
3200 Chapel Hill -Nelson Hwy, Suite 105 • PO Box 14409
Research Triangle Park, NC 27709
Tel [phone] • Fax [phone]
December 23, 2008

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table of Contents
List of Tables iv
List of Figures vii
1 Introduction 1-1
2 Neuse River Estuary Model 2-1
2.1 EFDC Model Development 2-1
2.1.1 Model Grid 2-1
2.1.2 Weather 2-1
2.1.3 Freshwater Flow 2-5
2.1.4 Point Sources 2-9
2.1.5 Water Surface Elevation 2-10
2.1.6 Salinity 2-10
2.1.7 Water Temperature 2-10
2.2 EFDC Model Calibration 2-11
2.2.1 Salinity 2-11
2.2.2 Water Temperature 2-19
2.3 WASP72 Model Development 2-24
2.3.1 Hydrodynamic Linkage File 2-24
2.3.2 Simulation Time and Print Interval 2-24
2.3.3 State Variables 2-24
2.3.4 Parameter Data 2-24
2.3.5 Constants 2-25
2.3.6 Loads 2-25
2.3.7 Time Functions 2-25
2.3.8 Boundary Concentrations 2-26
2.4 WASP72 Model Calibration 2-27
2.4.1 Nitrate 2-27
2.4.2 Ammonia 2-31
2.4.3 Orthophosphate 2-36
2.4.4 Dissolved Oxygen 2-39
2.4.5 Chlorophyll -a 2-43
2.5 Discussion 2-47
i

/i'
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
3 Nested Model 3-1
3.1 Approach 3-1
3.2 Nested Grid 3-1
3.3 Critical Periods 3-1
3.3.1 Flow 3-1
3.3.2 Water Temperature 3-3
3.3.3 Salinity 3-6
3.3.4 Wind 3-8
3.3.5 Discussion 3-9
3.4 Larger to Nested Assignments 3-9
3.4.1 EFDC 3-10
3.4.2 WASP72 3-18
3.5 Havelock WWTP 3-21
3.6 Existing MCAS CP Permit Conditions 3-22
3.7 Nested Model Application 3-24
4 Dilution Analysis 4-1
4.1 JPEFDC Subroutine 4-1
4.2 Configuration 4-1
4.3 Length Scales 4-2
4.4 Model Interpretation 4-2
4.5 Phase 3 Dilution Results 4-3
4.5.1 Summer 4-3
4.5.2 Winter 4-5
4.6 Phase 1 and 2 Dilution Results 4-6
4.6.1 Summer 4-7
4.6.2 Winter 4-7
4.7 Phase 3 Effluent Plume Interaction 4-8
5 Water Quality Analysis 5-1
5.1 Model lnterpretation 5-1
5.2 Summer Phase 3 Dissolved Oxygen Results 5-1
5.3 Winter Phase 3 Dissolved Oxygen Results 5-3
5.4 Summer Phase 3 Chlorophyll -a Results 5-5
5.5 Winter Phase 3 Chlorophyll -a Results 5-7
5.6 Summer Phase 1 and 2 Dissolved Oxygen Results 5-8
5.7 Winter Phase 1 and 2 Dissolved Oxygen Results 5-9
5.8 Summer Phase 1 and 2 Chlorophyll -a Results 5-9
Trnimucii
ii
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
5.9 Winter Phase 1 and 2 Chlorophyll -a Results 5-10
6 Water Quality Sensitivity Analysis 6-1
6.1 Sensitivity Analysis Scenarios 6-1
6.2 Sensitivity Analysis Results 6-2
7 Conclusion 7-1
8 References 8-1
® writ►
iii

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
List of Tables
Table 2-1. Weather Station Summary Information 2-2
Table 2-2. Rainfall Station Information 2-3
Table 2-3. Wind Station Information 2-4
Table 2-4. Model Wind Forcing Averages by Month 2-4
Table 2-5. USGS Flow and Water Quality Station Summary Information 2-5
Table 2-6. Area Weighting Factors for Flow Estimation of Tributary Areas 2-9
Table 2-7. Point Source Summary Information 2-9
Table 2-8. EFDC Simulation Salinity (PSU) Statistics, ModMon 100 2-19
Table 2-9. EFDC Simulation Salinity (PSU) Statistics, ModMon 180 2-19
Table 2-10. EFDC Simulation Water Temperature (deg C) Statistics, ModMon 100 2-23
Table 2-11. EFDC Simulation Water Temperature (deg C) Statistics, ModMon 180 2-23 r�
Table 2-12. State Variables (Systems) Used in WASP for Neuse River Estuary
Application 2-24
Table 2-13. WASP72 Simulation Nitrate (mgN/L) Statistics, ModMon 100 2-30
Table 2-14. WASP72 Simulation Nitrate (mgN/L) Statistics, ModMon 180 2-31
Table 2-15. WASP72 Simulation Ammonia (mgN/L) Statistics, ModMon 100 2-35 r"N
Table 2-16. WASP72 Simulation Ammonia (mgN/L) Statistics, ModMon 180 2-35
Table 2-17. WASP72 Simulation Dissolved Oxygen (mg/L) Statistics, ModMon 100 2-42
Table 2-18. WASP72 Simulation Dissolved Oxygen (mg/L) Statistics, ModMon 180 2-43 r�
Table 2-19. WASP72 Simulation Chlorophyll -a (µg/L) Statistics, ModMon 100 2-47 (1°'
Table 2-20. WASP72 Simulation Chlorophyll -a (µg/L) Statistics, ModMon 180 2-47
Table 3-1. Monthly Average MCAS Cherry Point and City of Havelock Permit and
Performance Information 3-2 ,ibs
Table 3-2. Wind Forcing Summary 3-8 eRN
Table 3-3. Current Permit for the City of Havelock WWTP r�
(NPDES Number NC0021253) 3-21
Table 3-4. Proposed Phases of the Havelock WWTP Discharge 3-22
Table 3-5. Current Permit for MCAS CP WWTP (NPDES Number NC0003816) 3-23
Table 3-6. MCAS CP WWTP Model Input 3-24
Table 4-1. Representative Length Scales for WWTP Effluent and Ambient
Characteristics (Jirka, 1996) 4-2
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 4-2. Summer Effluent Plume Concentration Statistics and Related Dilution,
Phase 3 4-4
Table 4-3. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 3 4-5
Table 4-4. Summer Effluent Plume Concentration Statistics and Related Dilution, Phase 14-7
Table 4-5. Summer Effluent Plume Concentration Statistics and Related Dilution, Phase 24-7
Table 4-6. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 1 4-8
Table 4-7. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 2 4-8
Table 4-8. Difference in Chronic Effluent Plume Concentration for Havelock
WWTP Only versus Combined, Summer 4-9
Table 4-9. Difference in Chronic Effluent Plume Concentration for Havelock
WWTP Only versus Combined, Winter 4-9
Table 5-1. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 3 Permit Scenarios 5-3
Table 5-2. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 3 Permit Scenarios 5-5
Table 5-3. Statistics of the Difference of Chlorophyll -a (µg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 3 Permit Scenarios 5-7
Table 5-4. Winter Statistics of the Difference of Chlorophyll -a (µg/L) Simulations for
Surface and Bottom, No Havelock Versus Phase 3 Permit Scenarios 5-8
Table 5-5. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 1 Permit Scenarios 5-8
Table 5-6. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 2 Permit Scenarios 5-9
Table 5-7. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 1 Permit Scenarios 5-9
Table 5-8. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 2 Permit Scenarios 5-9
Table 5-9. Summer Statistics of the Difference of Chlorophyll -a (µg/L) Simulations
for Surface and Bottom, No Havelock Versus Phase 1 Permit Scenarios 5-10
Table 5-10. Summer Statistics of the Difference of Chlorophyll -a (µg/L) Simulations
for Surface and Bottom, No Havelock Versus Phase 2 Permit Scenarios 5-10
Table 5-11. Winter Statistics of the Difference of Chlorophyll -a (µg/L) Simulations for
Surface and Bottom, No Havelock Versus Phase 1 Permit Scenarios 5-10
Table 5-12. Winter Statistics of the Difference of Chlorophyll -a (µg/L) Simulations for
Surface and Bottom, No Havelock Versus Phase 2 Permit Scenarios 5-10
Table 6-1. Sensitivity Analysis Scenarios 6-2
TWMATICH

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 6-2. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface,
No Havelock Versus the Noted Scenario 6-3
Table 6-3. Summer Statistics of the Difference of Chlorophyll -a (µg/L) Simulations for
Surface, No Havelock Versus the Noted Scenario 6-3
TWMA1101
vi

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
List of Figures
Figure 1-1. Location of Neuse River Estuary 1-2
Figure 1-2. Study Area Location within the Neuse River Estuary 1-2
Figure 1-3. Study Area General Information 1-3
Figure 2-1. Weather Stations for Model Development 2-2
Figure 2-2. Patched Annual Rain at New Bern Craven County Regional AP
(Coops ID 316108)
Figure 2-3. USGS Flow and Water Quality Station Locations
Figure 2-4.
Figure 2-5.
Figure 2-6.
Figure 2-7.
Figure 2-8.
Figure 2-9.
Figure 2-10.
Figure 2-11.
Figure 2-12.
Figure 2-13.
Figure 2-14.
Figure 2-15.
Figure 2-16.
Figure 2-17.
Figure 2-18.
Figure 2-19.
Figure 2-20.
Figure 2-21.
Figure 2-22.
Figure 2-23.
Figure 2-24.
Figure 2-25.
Figure 2-26.
®""‘1"'C'
30-Day Moving Average of Flow from Stations 02091814 and 02092500
Annual Average Flow at Trent River near Trenton, NC (02092500)
Annual Average Flow at Neuse River near Fort Barnwell, NC (02091814)
UNC-IMS and NCSU-CAAE Station Locations
Salinity Calibration Comparison for 1998 — 2000 at USGS Light 9
Salinity Validation Comparison for 2001— 2006 at USGS Light 9
Salinity Calibration Comparison for 1998 — 2000 at USGS Light 11
Salinity Validation Comparison for 2001— 2006 at USGS Light 11
Salinity Calibration Comparison for 1998 — 2000 at NCSU Cherry Point 34
Salinity Validation Comparison for 2001— 2006 at NCSU Cherry Point 34
Salinity Calibration Comparison for 1998 — 2000 at NCSU Minnesott 35
Salinity Validation Comparison for 2001— 2006 at NCSU Minnesott 35
Salinity Calibration Comparison for 1998 — 2000 at ModMon 100
Salinity Validation Comparison for 2001— 2006 at ModMon 100
Salinity Calibration Comparison for 1998 — 2000 at ModMon 180
Salinity Validation Comparison for 2001— 2006 at ModMon 180
Water Temperature Calibration Comparison for 1998 — 2000 at
USGS Light 11 2-20
Water Temperature Validation Comparison for 2001 — 2006 at
USGS Light 11 2-20
Water Temperature Calibration Comparison for 1998 — 2000 at ModMon 100 2-21
Water Temperature Validation Comparison for 2001 — 2006 at ModMon 100 2-21
Water Temperature Calibration Comparison for 1998 — 2000 at ModMon 180 2-22
Water Temperature Validation Comparison for 2001 — 2006 at ModMon 180 2-22
Parameter Settings for WASP Application of Neuse River Estuary 2-25
2-3
2-6
2-7
2-7
2-8
2-11
2-12
2-13
2-13
2-14
2-14
2-15
2-15
2-16
2-16
2-17
2-17
2-18
vii

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Figure 2-27. NO3 Calibration Comparison for 1998 - 2000 at ModMon 100
Figure 2-28. NO3 Validation Comparison for 2001 - 2006 at ModMon 100
Figure 2-29. NO3 Calibration Comparison for 1998 - 2000 at ModMon 180
Figure 2-30. NO3 Validation Comparison for 2001 - 2006 at ModMon 180
Figure 2-31. NO3 Validation Comparison for 1998 - 2006 at Cherry Point 34
Figure 2-32. NO3 Validation Comparison for 1998 - 2006 at Minnesott 35
Figure 2-33. NH3 Calibration Comparison for 1998 - 2000 at ModMon 100
Figure 2-34. NH3 Validation Comparison for 2001 - 2006 at ModMon 100
Figure 2-35. NH3 Calibration Comparison for 1998 - 2000 at ModMon 180
Figure 2-36. NH3 Validation Comparison for 2001 -2006 at ModMon 180
Figure 2-37. NH3 Validation Comparison for 1998 - 2006 at Cherry Point 34
Figure 2-38. NH3 Validation Comparison for 1998 - 2006 at Minnesott 35
Figure 2-39. PO4 Calibration Comparison for 1998 - 2000 at ModMon 100
Figure 2-40. PO4 Validation Comparison for 2001- 2006 at ModMon 100
Figure 2-41. PO4 Calibration Comparison for 1998 - 2000 at ModMon 180
Figure 2-42. PO4 Validation Comparison for 2001 - 2006 at ModMon 180
Figure 2-43.
Figure 2-44.
Figure 2-45.
Figure 2-46.
Figure 2-47.
Figure 2-48.
Figure 2-49.
Figure 2-50.
Figure 2-51.
Figure 2-52.
Figure 2-53.
Figure 2-54.
Figure 2-55.
Figure 2-56.
Figure 3-1.
Figure 3-2.
111MW\11104
,
PO4 Validation Comparison for 1998 - 2006 at Cherry Point 34
PO4 Validation Comparison for 1998 - 2006 at Minnesott 35
DO Calibration Comparison for 1998 - 2000 at ModMon 100
DO Validation Comparison for 2001- 2006 at ModMon 100
DO Calibration Comparison for 1998 - 2000 at ModMon 180
DO Validation Comparison for 2001- 2006 at ModMon 180
DO Validation Comparison for 1998 - 2006 at Cherry Point 34
DO Validation Comparison for 1998 - 2006 at Minnesott 35
Chl-a Calibration Comparison for 1998 - 2000 at ModMon 100
Chl-a Validation Comparison for 2001 - 2006 at ModMon 100
Chl-a Calibration Comparison for 1998 - 2000 at ModMon 180
Chl-a Validation Comparison for 2001- 2006 at ModMon 180
Chl-a Validation Comparison for 1998 - 2006 at Cherry Point 34
Chl-a Validation Comparison for 1998 - 2006 at Minnesott 35
30-Day Moving Average Flow for Stations 02091814 and 02092500
30-Day Moving Average Flow for Stations 02091814 and
02092500, 2001 - 2002 3-3
2-27
2-28
2-28
2-29
2-29
2-30
2-32
2-32
2-33
2-33
2-34
2-34
2-36
2-37
2-37
2-38
2-38
2-39
2-39
2-40
2-40
2-41
2-41
2-42
2-44
2-44
2-45
2-45
2-46
2-46
3-2

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Figure 3-3. Water Temperature at Bullseye-33, 1998 - 2006 3-4
Figure 3-4. Water Temperature at ModMon 100, 1998 - 2006 3-4
Figure 3-5. Water Temperature at Bullseye-33, September 2001— August 2002 3-5
Figure 3-6. Water Temperature at ModMon 100, September 2001 — August 2002 3-5
Figure 3-7. Salinity at Bullseye-33, 1998 - 2006 3-6
Figure 3-8. Salinity at Bullseye-33, 2001 - 2002 3-7
Figure 3-9. Salinity at ModMon 100, 1998 - 2006 3-7
Figure 3-10. Salinity at ModMon 100, 2001 - 2002 3-8
Figure 3-11. Larger and Nested Grids 3-9
Figure 3-12. Ghost Cells for Input to Nested Model from Larger Model 3-10
Figure 3-13. Summer Critical Period, Depth Simulation Comparison of Larger (52,13)
to Nested (24, 31) 3-11
Figure 3-14. Summer Critical Period, Surface Salinity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-12
Figure 3-15. Summer Critical Period, Bottom Salinity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-12
Figure 3-16. Summer Critical Period, Surface Water Temperature Simulation
Comparison of Larger (52,13) to Nested (24, 31) 3-13
Figure 3-17. Summer Critical Period, Bottom Water Temperature Simulation
Comparison of Larger (52,13) to Nested (24, 31) 3-13
Figure 3-18. Summer Critical Period, Surface U Velocity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-14
Figure 3-19. Summer Critical Period, Bottom U Velocity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-14
Figure 3-20. Winter Critical Period, Depth Simulation Comparison of Larger (52,13) to
Nested (24, 31) 3-15
Figure 3-21. Winter Critical Period, Surface Salinity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-15
Figure 3-22. Winter Critical Period, Bottom Salinity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-16
Figure 3-23. Winter Critical Period, Surface Water Temperature Simulation Comparison
of Larger (52,13) to Nested (24, 31) 3-16
Figure 3-24. Winter Critical Period, Bottom Water Temperature Simulation Comparison
of Larger (52,13) to Nested (24, 31) 3-17
Figure 3-25. Winter Critical Period, Surface U Velocity Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-17
® TRRATiW
ix

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Figure 3-26.
Figure 3-27.
Figure 3-28.
Figure 3-29.
Figure 3-30.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 5-7.
Figure 5-8.
Figure 5-9.
Figure 5-10.
nmanai
ems
Winter Critical Period, Bottom U Velocity Simulation Comparison of fa,
Larger (52,13) to Nested (24, 31) 3-18
Summer Critical Period, Surface Dissolved Oxygen Simulation Comparison
of Larger (52,13) to Nested (24, 31) 3-19
Winter Critical Period, Surface Dissolved Oxygen Simulation Comparison
of Larger (52,13) to Nested (24, 31) 3-19
Summer Critical Period, Surface Chlorophyll -a Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-20
Winter Critical Period, Surface Chlorophyll -a Simulation Comparison of
Larger (52,13) to Nested (24, 31) 3-20
Summer Effluent Plume Concentration, Phase 3 4-4
Summer Dilution, Phase 3 4-5
Winter Effluent Plume Concentration, Phase 3 4-6
Winter Dilution, Phase 3 4-6
Summer Simulated Dissolved Oxygen Values, No Havelock Versus
Phase 3 Permit Scenarios 5-1
Summer Daily Wind Speed and 7-Day Moving Average of Headwater Flow 5-2
Summer Simulated Dissolved Oxygen Difference, No Havelock
Versus Phase 3 Permit Scenarios 5-3
Winter Simulated Dissolved Oxygen Values, No Havelock Versus
Phase 3 Permit Scenarios 5-4
Winter Daily Wind Speed and 7-Day Moving Average of Headwater Flow 5-4
Winter Simulated Dissolved Oxygen Difference, No Havelock
Versus Phase 3 Permit Scenarios 5-5 i"" N
Summer Simulated Chlorophyll -a, No Havelock Versus Phase 3 P'.'`
Permit Scenarios 5-6
Summer Simulated Chlorophyll -a Difference, No Havelock Versus
Phase 3 Permit Scenarios 5-6
Winter Simulated Chlorophyll -a, No Havelock Versus Phase 3
Permit Scenarios 5-7
Winter Simulated Chlorophyll -a Difference, No Havelock Versus
Phase 3 Permit Scenarios 5-8 r'"'
rd
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
1 Introduction
The City of Havelock (Havelock) is investigating the proposed relocation of their wastewater treatment
plant outfall from Slocum Creek to the Neuse River Estuary (NRE). Havelock is located in Craven
County on the North Carolina coast, approximately 18 miles (30 km) southeast of the City of New Bern.
Havelock is on the south side of the NRE and just west of an area referred to as "the bend." The bend is
the part of the NRE where the longitudinal orientation changes from generally a southeast seaward flow
direction to a northeast seaward flow direction. Figure 1-1 through Figure 1-3 display location
information.
The United States Marine Corps Air Station at Cherry Point (MCAS CP) currently has a wastewater
treatment plant outfall in the NRE. The proposed Havelock outfall location is in an area approximately
0.4 to 0.6 miles east (700 —1000 m) of the existing MCAS CP outfall.
The objectives of this study were the following.
• Simulate the chronic dilution for the proposed Havelock outfall under critical conditions.
• Evaluate the interaction (chronic) of the existing MCAS CP effluent with the proposed Havelock
effluent under critical conditions.
• In the vicinity of the proposed Havelock outfall, simulate the impacts to dissolved oxygen and
chlorophyll -a concentrations under critical conditions.
• Investigate three phases of Havelock wastewater treatment plant expansion; 2.25 mgd, 2.8 mgd,
and 3.5 mgd (0.099 cms, 0.123 cms, and 0.153 cms).
Tetra Tech used a coupled model application for the NRE from approximately New Bern to Pamlico
Sound originally developed for the NRE TMDL. The model application couples the Environmental Fluid
Dynamics Code (EFDC) with the Water Quality Analysis Simulation Program (WASP72). The model
was modified to provide simulations at a finer scale (nested) model grid appropriate for the current
application.
The modeling platform affords numerous advantages for studying the potential impacts of the Havelock
discharge. Among these are:
• A nearfield jet -plume simulation coupled to a farfield simulation.
• Investigation with observed or estimated time varying forcings (e.g., application of continuous
meteorological and inflow measurements).
• Dynamic hydraulic simulation.
• Dynamic eutrophication simulation.
1-1

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
City 70 0 70 140 Miles
0 HUC8
State of North Carolina
County
l
Contentnea
03020203
Middle Neuse
03020202
Lower Neuse
03020204
Figure 1-1. Location of Neuse River Estuary
Figure 1-2. Study Area Location within the Neuse River Estuary
®rrnu►na,
1-2

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
A MCAS CP Outfall
Road
A/ RF3 Streams
Slocum Creek
A
600 0 600 1200 1800 Meters
Proposed Havelock
Outfall Area
of Investigation
v
Figure 1-3. Study Area General Information
®TsrnAna+
1-3

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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
caN
coN
2 Neuse River Estuary Model
The NRE has been the subject of numerous data collection and modeling studies (Bales and Robbins,
1999). The USGS, NCDWQ, UNC-IMS, and NCSU-CAAE have all been involved in varying levels of
rse) data collection in the NRE. EPA Region 4 performed a TMDL study on the NRE for simulation years
1998 — 2000 (EPA, 2001, Wool et al., 2003). The modeling work coupled the Environmental Fluid
Dynamics Code (EFDC) (Hamrick, 1996) with Water Quality Analysis Simulation Program (WASP)
(Ambrose et al., 1993, EPA, 2006b). Since that work was performed both EFDC and WASP have been
released in updated versions. The models have been updated to the most recent versions of the software
and the simulation time period extended under work conducted for the US Army Corp of Engineers by
Tetra Tech.
In the context of this study, the NRE model will be referred to as the larger model or larger grid.
2.1 EFDC MODEL DEVELOPMENT
The Environmental Fluid Dynamics Code (EFDC) is a robust 3-dimensional hydrodynamic model. It is
capable of simulating salinity, temperature, atmospheric interactions, circulation and more. It will be
used to represent the complex hydrodynamics of the NRE and pass those to the WASP water quality
application. The Watershed Characterization System (EPA, 2007) was used as the GIS platform to help
develop model input.
2.1.1 Model Grid
The model grid from the EPA TMDL work was adopted for this study. There will be no modification to
the horizontal or vertical cell definitions of the grid or the number of cells.
2.1.2 Weather
Weather forcing information for an EFDC application is contained in the ASER.INP and WSER.INP
eat\ input files. The ASER.INP file contains atmospheric pressure, air temperature, relative humidity, rainfall,
solar radiation, and cloud cover. Evapotranspiration is internally calculated in this EFDC application.
The WSER.INP file contains the wind speed and direction information. The weather data were processed
using the MetADAPT tool from the USEPA Region 4 TMDL Tool Box (EPA, 2006a). Five weather
stations were reviewed to develop the weather forcing for the model applications (Figure 2-1 and
Table 2-1). These stations were maintained by the National Climate Data Center (NCDC), U.S.
Geological Survey (USGS), and North Carolina State University — Center for Applied Aquatic Ecology
(NCSU-CAAE).
rot

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
Figure 2-1. Weather Stations for Model Development
Table 2-1. Weather Station Summary Information
Name
ID 1
ID 2
Latitude
Longitude
Agency
New Bern Craven Co. Reg. AP
93719
316108
35.06666700
-77.05000000
NCDC
Neuse River at Channel Light 11
USGS-LT11
0209262905
34.99916700
-76.94305600
USGS
NCSU Cherry Point
NCSU-CP
-
34.94742533
-76.81589317
NCSU CAAE
Morehead City 2WNW
315830
-
34.73333300
-76.73333300
NCDC
MCAS Cherry Point
13754
-
34.90000000
-76.88333300
NCDC
2.1.2.1 Rainfall
Rainfall information was gathered from NCDC 2007 and Earthlnfo 2007 for New Bern Craven County
Regional Airport (Coops ID 316108). The rainfall from the Summary of the Day (SOD) record was first
patched for missing data by using the SOD record for Morehead City 2WNW (Coops ID 315830). Next,
it was disaggregated to hourly by using the hourly rainfall record at New Bern Craven County Regional
Airport (WBAN 93719). If a disaggregation template was not found in the index station, the SCS Type II
distribution was used. The SOD record was used as a starting point instead of the WBAN record because
historically those rainfall records are of more integrity than the hourly record since approximately 1996.
nTITRATICH
2-2

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-2. Rainfall Station Information
Raw Station for Rainfall
Index Station for Patching
Missing Periods
Index Station for Disaggregation
to Hourly
New Bern Craven County Regional AP
(Coops ID 316108)
Morehead City 2WNW (Coops
ID 315830)
New Bern Craven County Regional AP
(WBAN 93179)
Ink Figure 2-2 shows the annual totals of rainfall after the patching process at New Bern Craven County
Regional AP (Coops ID 316108). The long-term average is also plotted for reference in assessing above
and below average rainfall years. The long-term average was developed from the annual totals from
years that were 100 percent complete, that is, no impaired flagging. Thirty-nine years were averaged,
1959 — 1964, 1966 - 1993, and 2002 — 2006. The long-term annual average rainfall for New Bern Craven
County Regional AP (Coops ID 316108) is 54.73 inches. 2001 and 2002 were approximately 13 and 5
inches below average, respectively, while 2003 had approximately 18 inches of above average rainfall.
75
I
,
I
1
1
1
I
I
1 1
I
I
1
I 1
70
— r
T
1 -I
r- r
I
I 1
1
I
I 1
1
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1 I
1
65—
- - -
-
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r
I 1
I
I
1 1
1
I I
1
60---_
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y
r
1
1
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1
1 I
1
1
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a
a
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Iit-
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30
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1
f
1999
2000
2001 2002 2003
2004 2005
2006
1998
1-316108 Avg (Lang -Term) —a-316108-PalchedI
Figure 2-2. Patched Annual Rain at New Bern Craven County Regional AP (Coops ID 316108)
,., 2.1.2.2 Wind
The NRE is a relatively shallow system with poor connectivity to the open ocean. As such, the wind
forcing becomes a primary factor affecting circulation and water level. When the original EPA TMDL
/MA work was performed, there were no wind observation stations over the estuary, thus the wind recorded at
the MCAS Cherry Point (WBAN 13754) station was the primary source for the wind forcing.
eft,Since approximately year 2000, hourly wind recording devices were placed in the field over the estuary.
Table 2-3 lists the stations used to form the wind forcing for the model. The order presented in the table
is similar to the priority given during the construction of the continuous wind forcing for the model.
Oak
nTETRATSCH
2-3

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-3. Wind Station Information
Station Name
ID
Agency
Begin
Date ,
- End Date
Comment
NCSU Cherry Point
NCSU-CP
NCSU —
CAAE
3/16/2000
9/18/2003
Neuse River at Channel Light 11
near Flanner Beach, NC
USGS-
LT11
USGS
2/14/2001
12/31/2006
Provisional
MCAS Cherry Point
WBAN
13754
NCDC
1/1/1997
12/31/2006
Significant periods of no
observations
New Bern Craven County
Regional AP
WBAN
93719
NCDC
3/1/1999
12/31/2006
WSPD adjusted +2.9
mph
The magnitudes of the wind records were developed into monthly averages. The NCSU Cherry Point,
NCDC MCAS Cherry Point, and USGS Light 11 values were similar, but New Bern Craven County
Regional AP showed a consistent lower magnitude. Thus, a constant adjustment of 2.9 miles per hour
(1.3 m/s) was added to the reported magnitudes of wind speed. Table 2-4 summarizes the monthly
averages for the wind forcing record developed for this model.
Table 2-4. Model Wind Forcing Averages by Month
Month
Wind Speed (mph)
Wind Direction. (degrees from North)
January
10.1
290
February
10.2
325
March
10.7
294
April
11.5
252
May
9.9
242
June
8.6
218
July
7.9
218
August
7.8
157
September
9.4
46
October
8.1
6
November
8.4
322
December
9.1
311
Generally, the wind blows out of the northwest from approximately November to March; out of the
southwest from April to July; out of the southeast in August; and out of the northeast from September to
October.
®1TThATi0i
2-4
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.1.2.3 Remaining Weather Constituents
The remaining weather constituents were developed from the New Bern Craven County Regional AP
(93719) station (Martin and McCutcheon, 1999). These included pressure, air temperature, humidity,
ow) cloud cover estimate, and solar radiation estimate (Hamon method).
2.1.3 Freshwater Flow
The freshwater flows for the EFDC application are defined in the QSER.INP input file. All freshwater
flow inputs were distributed equally across the four layers at the given horizontal location. Freshwater
flows are dominated by the Neuse River entering the estuary at approximately New Bern. There is a flow
gage station on the Neuse River near Fort Barnwell (02091814). The other daily average observation
eAN
record was on Trent River near Trenton (02092500). The location of these stations and summary
information are presented in Table 2-5 and Figure 2-3 (USGS, 2007). The USGS water quality stations
are also presented since the common agency for these five is the USGS.
__ Table 2-5. USGS Flow and Water Quality Station Summary Information
toN
elaN
MIN
esIN
egts
flitN
Name
ID 1
•
ID 2
Type
Drainage Area
(sti:mi)
Neuse River near Fort Barnwell, NC
02091814
-
Flow
3,900
Trent River near Trenton, NC
02092500
-
Flow
168
Neuse River at New Bern, NC
02092162
USGS-
NewBem
Water
Quality
4,470
Neuse River at Channel Light 11 near
Flanner Beach, NC
0209262905
USGS-LT11
Water
Quality
-
Neuse River at Channel Light 9 at Cherry
Point, NC
0209265810
USGS-LT9
Water
Quality
-
2-5

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
USGS
Larger Grid
RF3 Streams
'02091814
Figure 2-3. USGS Flow and Water Quality Station Locations
These records were developed into time series of 30-day moving averages to view more significant
durations of high and low flow periods. These are presented in Figure 2-4. Generally, there is a
distinctive difference in the 30-day moving average before and after approximately January 2003. Before
January 2003, the period is marked by frequent and substantive low flow. Two particular notes are made
for 1) the hurricane in September 1999 which followed closely to a relatively sustained period of low
flows and 2) the lowest 30-day moving average noted at each station in 2002. After January 2003 the
range of the 30-day moving average is mostly smaller and more consistent.
2-6

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
30-Day Moving Average Flow (erns)
1/1998
1/1999
1/2000
1/2001
1/2002
1/2003
1/2004
—Neuse R (02091814) —Trent R (02092500)1
1/2005
1/2006
Figure 2-4. 30-Day Moving Average of Flow from Stations 02091814 and 02092500
The Trent River near Trenton station, due only to its long-term record (1951 — 2006) and acknowledging
that it has a drainage area of only 168 square miles (435 sq. km), was reviewed to infer whether a given
year may be above average, average, or below average with respect to flow volume. Figure 2-5 indicates
that 1998, 2000, 2004, and 2005 were near average annual flow years while 2001 and 2002 represented
consecutive below average years.
Annual Average Flow
12
6-
0
1998 1999
2000 2001
2002 2003 2004 2005 2006
I(Trent R(02092500)(cros)—Long-Term Annual Average I
Figure 2-5. Annual Average Flow at Trent River near Trenton, NC (02092500)
nTOTRATICH
2-7

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The Neuse River near Fort Barnwell, NC station began flow observations in 1996. As such, the long-
term annual average may not be reflective of the actual long-term average. Given generally drier
hydrologic regime in the area since 1996, the long-term annual average from the record may be an under-
estimate. However, Figure 2-6 indicates consecutive below average years for 2001 and 2002, with 2005
also being relatively low. 2000, 2004, and 2006 appear to be near average years.
225
200 -
175 -
150
E
0
a 125
E
a' 100
.
< 75
25
0
1
1
l
1
1998
1999 2000
2001 2002 2003 2004 2005 2006
-II-Nouso R(020918145cros) —Long-Tartu Annual Average I
Figure 2-6. Annual Average Flow at Neuse River near Fort Barnwell, NC (02091814)
The areas immediately adjacent to the Neuse River estuary are referred to as tributaries. The flow
representation for these areas is area weighted from the Trent River near Trenton NC (02092500) flow
gaging station. The tributary areas and factors are presented in Table 2-6. This approach was used for the
complete simulation period of 1998 — 2006.
nTT
2-8

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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-6. Area Weighting Factors for Flow Estimation of Tributary Areas
emeN
raN
eA1
eas
Tributary
Area (sq mi) .
Area -Weighting Factor
Broad Creek
17.8
0.11
Greens Creek
19.4
0.12
Dawson Creek
26.0
0.15
Beard Creek
19.6
0.12
Goose Creek
43.6
0.26
Upper Broad Creek
82.4
0.49
South River
49.6
0.30
Adams Creek
43.6
0.26
Clubfoot Creek
24.9
0.15
Hancock Creek
26.1
0.16
Slocum Creek
49.1
0.29
Trent River (d/s)
111.3
0.66
Trent River (mid)
267.1
1.59
Bachelor Creek
56.1
0.33
Swift Creek
321.6
1.91
2.1.4 Point Sources
earh Four point sources were input into the QSER.INP file. The point sources were assigned to the bottom-
most cell of a horizontal location. They are presented in Table 2-7. They consist of one pulp discharge
and three wastewater treatment discharges. The Weyerhaeuser and New Bern WWTP discharges are near
the headwaters of the model grid, near New Bern. The MCAS Cherry Point WWTP and Havelock
WWTP discharges are near Slocum Creek.
rah
test
eAN
Table 2-7. Point Source Summary Information
Name
NPDES ID
Average Discharge (cros)
Average Discharge (mgd)
Weyerhaeuser Pulp
NC0003191
0.710
16.2
New Bern WWTP
NC0025348
0.176
4.0
MCAS Cherry Point WWTP
NC0003816
0.101
2.3
Havelock WWTP
NC0021253
0.066
1.5
eALN The approximate long-term annual average of the sum of the Neuse River near Fort Barnwell (02091814)
and Trent River near Trenton (02092500) is 2,853 mgd (125 cms), which does not consider the tributary
flow. The relative contribution of the flow from these point sources at approximately 24 mgd (1 cms) is
small. However, the constituent loadings may have an impact, this will be considered in the WASP
application.
2-9
each

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.1.5 Water Surface Elevation
The open boundary for the model grid is approximately where the mouth of the NRE confluences with
Pamlico Sound, just seaward of Maw Point and Point of Marsh. There is a paucity of observed water
surface elevation in the NRE/Pamlico Sound. This has been a concern for the scientific community for
many years. In fact, Bob Christian of East Carolina University has sponsored a workshop to address this
issue and the USACE — Wilmington District has explored the potential of benchmarking one, or more
than one, station in the NRE/Pamlico Sound. Furthermore, the NRE/Pamlico Sound is very complex in
addition to being shallow in nature and poorly connected to the open ocean. As such, past modeling
efforts including the EPA TMDL work as well as the current body of work have been challenged in the
ability to represent the open boundary, which is important. Typically depth data via pressure transducers
are the only observations available, which means the atmospheric component must be subtracted out.
There still remained the conundrum of linking to a vertical datum. The approach was to determine the
average of the observed record and consider it the mean tidal depth.
Robert Reed, PhD of NCSU-CAAE has developed a statistical approach to hindcasting daily water
surface elevation based on a limited observed water surface elevation series on the area of interest, a
regional long-term water surface elevation gage, and a wind forcing (Reed et al., 2007). For this
application, the discontinuous depth observations at ModMon 180 were developed into water surface
elevations. The long-term regional water surface elevations were used from Oregon Inlet Marina
(8652587) and Beaufort (8656483). The wind record, which was worked into u-v vector format with a
40-degree clockwise shift was developed as described in Section 2.1.2.2.
Thus, the water surface elevation forcing series, which is entered in the input file called PSER.INP, was
composed of the EPA TMDL 1998 — 2000 sub -daily record, along with the 2001 — 2006 hindcasted daily
record. This decision was made with respect to no credible continuous observed time series available.
The daily hindcasting technique shows a reasonable ability to capture wind effects, storm surge and
astronomical components of the open boundary. Since the output of interest in this work is on the scale
of a day or days, it was deemed acceptable to force the open boundary with a daily record.
2.1.6 Salinity
The salinity forcing information is placed in the SSER.INP input file. The initial condition for all model
grid cells is defined in the SALT.INP input file. The Adams Creek tributary is an intracoastal waterway
and was assigned a constant value of 12 g/L (12 PSU) for salinity. The open boundary assignment from
the EPA TMDL 1998 — 2000 simulation was used to begin the file for this work. This was done to
capitalize on the processing that was already performed to represent the salinity of the open boundary.
After 2000, the frequency of observations at ModMon 180 increased to twice per month. Thus the record
was considered sufficient to process and append to the previous work. The processing involved reducing
the observed profile to four average values by depth that would then be used to force each of the four
layers at that specific time. The observations were generally made twice a month and the profiles
typically had six or more observations.
2.1.7 Water Temperature
The water temperature forcing information is placed in the TSER.INP input file. The initial condition is
defined in the TEMP.INP input file. At the open boundary the longitudinal water temperature gradient is
much less, typically, than the longitudinal salinity gradient. Thus ModMon 160 and ModMon 180 were
used to create a forcing that goes from 1998 through 2006. ModMon 160 was used particularly because
the frequency of observation to ModMon 180 is less for the period of 1998 — 2000, therefore a
supplement was desired.
SITTRA:11101
2-10

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The headwater forcing was determined from the ModMon 0 station. Its frequency of observation was
approximately twice per month for the simulation period of 1998 — 2006. It was processed into forcings
for four layers and assigned to the headwaters. Furthermore, it was assigned to the tributary flow
definitions.
The DMR data for the four point sources were used to develop unique water temperature forcings for
each of the point sources, however, they are basically similar.
2.2 EFDC MODEL CALIBRATION
The models were run for a simulation period of 1998 — 2006. The comparisons were prioritized to first
match the performance of the EPA TMDL simulation period of 1998 —2000 and then compare to the
extended period of 2001 — 2006. The stations used for calibration can be found in Figure 2-3 and
Figure 2-7.
▪ UNC-IMS
• NCSU-CAAE
Larger Grid
RF3 Streams
Figure 2-7. UNC-IMS and NCSU-CAAE Station Locations
2.2.1 Salinity
The salinity simulation was compared to observed data at multiple locations. These were USGS stations
Light 9 and Light 11 (Figure 2-8 through Figure 2-11); NCSU-CAAE stations Cherry Point 34 and
Minnesott 35 (Figure 2-12 through Figure 2-15); and UNC-CH IMS stations ModMon 100 and ModMon
180 (Figure 2-16 through Figure 2-19). The salinity simulation captures the trends observed in the
® TTTIMT104
2-11

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
estuary reasonably well. The model captures the fresh water pulses and the rebuilding of salinity in the
estuary across a 9-year simulation. The most dynamic salt flushing is observed during the hurricane
season of 1999 which the simulation captured. It can be seen that generally near the area of the bend the
salinity was completely flushed out. By station ModMon 180, there was little salinity remaining from
this pulse. The salinity concentrations build back across 2000 through 2002, and then 2003 is a wet year
(Section 2.1.3) and the salinity reflects that through decreased concentrations.
28
20
24
22
20
18
1G
14
12
10
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1998
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1999
1998-2000
2000
Bottom Salt IPSUI
Swface SaIt(PSUI
• USGS•LT9
Figure 2-8. Salinity Calibration Comparison for 1998 — 2000 at USGS Light 9
111T*18.111cti
2-12

ANN
.t,
•
AMIN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
26
24
22
20
18
16
11
12
10
8
2
0
2001
1111
•
Me 1!1�w��■
iii,
1114
'allU
MIL,A01
,rtr" 31
C
-Intl
Ir. 71'
• N. Jai
MEE'
2002
2003
2004
2001-2006
2005
2006
Bonom Sah 1PSU,
Surface SaIt(PSUI
• USGS.Li9
Figure 2-9. Salinity Validation Comparison for 2001 — 2006 at USGS Light 9
28
26
24
22
20
18
16
11
12
10
8
6
4
■
•
L'
•
!
t -
•
+1
L
T
i•
lilt
•
;
•i•
i
, .
i S
i
I
+
r
r,!
•
r
Witt
mirk Alit
1 1
'
tWI
1998
1999
1998-2000
2000
Bottom Salt IPSUI
Surface S. ItiPSUI
• USGS1T11
Figure 2-10. Salinity Calibration Comparison for 1998 — 2000 at USGS Light 11
® T*TIRATDCH
2-13

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
26
24
22
20
18
16
14
12
10
8
6
2
0
2001
Is
11111111111
1-
MIIIMBI-11P-
Wfill
X . +r" f
::.? ...-40F.:,,,,a.
1 � '� , 1t
la's, t '
...mg a, 4
• :.,*--_,.,
:143Z. .41;
. P ' 1
2002
2003
2004
2001-2006
2005
2006
Bottom Salt IPSUI
Surface Salt1PSUI
■ USGS-1111
Figure 2-11. Salinity Validation Comparison for 2001 — 2006 at USGS Light 11
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
1998
■ •
■
•
1 ,
ibst
■
■
■
'
i.-1,';'i
it
Gii� Lt
• •
•
•
,
....! 'J ,
■
�`
1
4
t rR
I hi
_ •
■
I
`
■
1999
7998-2000
2000
Bottom Salt IPSUI
Surface Salt{PSUI
■ CHERRYPT34
Figure 2-12. Salinity Calibration Comparison for 1998 — 2000 at NCSU Cherry Point 34
TITRAT■a-I
2-14
AWN
te%
rOlk
PIN

ANA
AINIk
4116,
Adak
ANN
AS,
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
26
24
22
20
18
16
14
12
10
8
6
1
2
0
•
■
■
•
■
•
•
•
■
II
LtiU
•' •
, ■
I •
I
•1,
1•
.
•! 1 •■
_ii
•
I
%me
' .
■
,il
•
;
;
IL
'
.?1711
I
1
2001
2002
2003
2004
2001-2006
2005
2006
Bottom Sah IPSUI
- - - Surface SaItIPSUI
• CHERRYPT34
Figure 2-13. Salinity Validation Comparison for 2001 — 2006 at NCSU Cherry Point 34
28
26
24
22
20
18
16
11
12
10
8
6
4
2
0
I
1
■
t•
.
II
•
■
i
.
4.1111i1".
,
•
-lii r,,, ;�
;;M
:Te
'
■
. •kI1
ii
'•
-'
r
•
1998
1999
1998-2000
2000
Bottom Salt iPSUI
Surface SaIr PSU1
• MINNESOTT-35
Figure 2-14. Salinity Calibration Comparison for 1998 — 2000 at NCSU Minnesott 35
TIT AT■Q1
2-15

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
26
24
22
20
18
16
14
12
10
8
1
•
1
0 'i
.
a ' , I. i
yy 1 i , I
Pk'
,•
L
t I !.
'1� ivr'1'
r' 'kill'
�q '
!1k
6r1 t{!�lA
. ■ ro I�{ i
i.!ry
,ell i' ; .\I'
M SI '�
•
', . I ,:,�
1
M
I
2002
2003
2004
2001 - 2006
2005
2006
Bottom Salt IPSIq
Sulfate SaltIPS111)
• MINNESOTT-35
Figure 2-15. Salinity Validation Comparison for 2001 — 2006 at NCSU Minnesott 35
28
2G
24
22
20
18
16
14
12
10
8
6
-1
2
0
1998
•
VI
t
1
.
•'I
`!
P. ■
.
■
Ili
1 ■ •
. i�■
gig•
II w
a
11
'
•
ill
1!il
:
:It. .168
. •
I,
1
I. ,i-,
■
PPPpi
It)
1999
1998 - 2000
2000
Bottom Sah IPSUI
Surface Sah4PSth
• MODMON-L0NG100
Figure 2-16. Salinity Calibration Comparison for 1998 — 2000 at ModMon 100
r-n:.Qr1-; rl
2-16

AIIlk
AMA
.1116
Ink
.4218
821114
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
2G
24
22
20
18
16
1.1
12
10
8
6
2
0
■
■
■
■
•
■ I
- '
.
■
■■
.�
1
t r S i{
1
■
• ,
', '■fit
,f ,ij3
F
r
`
■,• ill
•.?
-
■
§ •
. •M i :
•
• t1.II
i 1 1+�
.
i III •■�
.
`,lig ti■
ji
V_
1,IMME
1�
IIIIY�II:i�1ti
�Y.1
1 , .:
'Allij
'^
:
P
r
"
!, 'I,
2001
2002
2003
2004
2001-2006
2005
2006
Bonin Salt (PSUI
- Surface S. It PSIQ
• MUUMUU-LOMG100
Figure 2-17. Salinity Validation Comparison for 2001 — 2006 at ModMon 100
30
20
10
0
."
�"�
.
. 4'I
`
I
1`
,^
' !
N.
• +
•
1.
L
,
•
1998
1999
1998-2000
2000
Bonom Salt (PSUI
Surface SaItlPSUI
• MODMO11-LONG180
Figure 2-18. Salinity Calibration Comparison for 1998 — 2000 at ModMon 180
l `zJ MTh`" 2-17

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
30
20
10
•
■
■'
1
1
■
•
•
■
■
■
■■
■
',.,
fr ;;'(�,N
'r+tit
,
•
N!
i
,
I
•
.
;
`
•
■
,
■
+,
{
I
•
}fir}11
sYi 1 ■ i'•
'�
-
Y1
� r1
1
t! ,
1S,
lrr
2001
2002
2003
2004
2001-2006
2005
Betters Sah 1PSU1
Surface Salt4PSU)
• MOOMDN-LOHG180
Figure 2-19. Salinity Validation Comparison for 2001 — 2006 at ModMon 180
Statistics were developed for ModMon 100 and ModMon 180 in Table 2-8 and Table 2-9. These were
selected as ModMon 100 is located near the bend and ModMon 180 is located near Pamlico Sound. The
observed data were manipulated to make one representative value per each model layer. The statistics
indicate good agreement with the observed data. The EPA TMDL statistics are repeated in Table 2-8 to
allow comparison.
T•T•AThQt
2-18

/sk1
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etrais
ems
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-8. EFDC Simulation Salinity (PSU) Statistics, ModMon 100
ofit
raks
eik"
tvik
esik‘
eSI)
esig
orztN
eseN
114,
ModMon 100 Bottom
ModMon 100 .Surface
ModMon 100
Surface
Statistic
Calibration
1998 - 2000 :
Validation
.2001 - 2006 '
Calibration .
1998.- 2000
Validation .
2001- 2006
EPA TMDL
1998 - 2000
Count
154
152
154
152
277
Mean Predicted
6.4
9.4
4.2
5.5
3.9
Mean Observed
8.4
12.1
5.2
7.6
5.1
Standard Deviation Predicted
5.4
5.2
4.0
4.4
3.7
Standard Deviation Observed
5.1
4.8
4.0
4.7
3.9
Mean Error (ME)
2.0
2.7
1.0
2.1
-1.2
ME Percent of Mean Obs.
23.8%
22.3%
19.6%
28.0%
Root Mean Square Error
(RMSE)
3.3
3.6
1.9
2.8
0.3
RMSE Percent of Mean Obs.
39.7%
29.4%
37.6%
36.5%
RA2 Correlation
0.76
0.80
0.83
0.86
0.85
Table 2-9. EFDC Simulation Salinity (PSU) Statistics, ModMon 180
ModMon 180 Bottom
ModMon -180 Surface
Statistic .
Calibration
1998 - 2000
Validation
2001 - 2006.
Calibration
1998r 2000
Validation
2001 - 2006 ;
Count
75
134
75
134
Mean Predicted
14.7
16.1
10.5
11.8
Mean Observed
14.1
17.0
11.2
14.8
Standard Deviation Predicted
4.9
4.6
4.9
4.8
Standard Deviation Observed
4.0
4.4
4.6
4.8
Mean Error (ME)
-0.6
0.9
0.7
2.9
ME Percent of Mean Obs.
-4.3%
5.3%
6.4%
19.9%
Root Mean Square Error (RMSE)
2.3
1.5
1.9
3.4
RMSE Percent of Mean Obs.
16.4%
8.8%
17.0%
22.8%
RA2 Correlation
0.80
0.93
0.87
0.88
2.2.2 Water Temperature
The water temperature observed data shows less vertical stratification than salinity. This may in part be
due to the generally shallow nature of the estuary. Furthermore, while the long-term trend of water
414" temperature in the estuary is anticipated to be generally consistent, the model does represent the subtle
rirnwrow
2-19

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
variations that occur from time to time, for example the summer of 2002. That period is coincident to low
flow, thus perhaps shallower depths and higher water temperature.
Figure 2-20 through Figure 2-25 present time series comparisons of the water temperature simulations
against data collected by the USGS and UNC-CH IMS.
IV
�'IlrillrAill
t0
fialfilliTal
* imii
1998
1999
1998-2000
2000
Bottom Temp ICI
Sudace Temp ICI
• USGS.LT11
Figure 2-20. Water Temperature Calibration Comparison for 1998 — 2000 at USGS Light 11
-10
30
20
10
0
2001
2002
2003
2001
2001-2006
2005
2006
Bottom Temp ICI
Sudace Temp ICI
USGS-LT11
Figure 2-21. Water Temperature Validation Comparison for 2001 — 2006 at USGS Light 11
TiTTIATIIICH
2-20

alb
Alb
ask
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
10
30
20
10
0
tau■'
r;
■G
�
1
■
1998
1999
1998-2000
2000
Bottom Temp ICI
Surface Temp ICI
MODMON10NG100
Figure 2-22. Water Temperature Calibration Comparison for 1998 — 2000 at ModMon 100
10
30
20
10
0
2001
t
10
111
2002
2003
2004
2001-2006
2005
2006
B nom Temp IC1
Surface Temp ICI
• MO0MON10N6100
aftFigure 2-23. Water Temperature Validation Comparison for 2001 — 2006 at ModMon 100
TTTRA.TK31
2-21

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
40
30
20
10
0
al
I
I
i
.
/
jl
1998
1999
1998-2000
2000
Bonnm Temp 1=1
Surface Temp ICI
■ MODMON-L01113180
Figure 2-24. Water Temperature Calibration Comparison for 1998 — 2000 at ModMon 180
-10
30
20
10
0
�
1
■
i
2001
2002
2003
2004
2001 - 2006
2005
2006
Bottom Temp ICf
- - Surface Temp IQ
■ MODMON-LONG180
Figure 2-25. Water Temperature Validation Comparison for 2001 — 2006 at ModMon 180
T.TRAT.G1
2-22
ebs
eft
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Oft

rots
rtaaN
ranN
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Two ModMon stations were selected for the development of model performance statistics. The stations
were ModMon 100 and ModMon 180. The statistics are presented in Table 2-10 and Table 2-11. The
statistics from the EPA TMDL work for ModMon 100 surface layer are also included in Table 2-10.
Table 2-10. EFDC Simulation Water Temperature (deg C) Statistics, ModMon 100
-ModMon. 100-Bottom
ModMon 100 Surface •
- ModMon 100
Surface.
Statistic
Calibration
1998 - 2000
Validation
2001 - 2006
Calibration
1998,, 2000:
Validation
. 2001- 2006 :.
EPA TMDL
499,8 - 2000
Count
154
152
154
152
273
Mean Predicted
18.1
17.8
18.9
19.0
19.2
Mean Observed
17.9
18.5
18.6
19.0
18.7
Standard Deviation Predicted
7.1
7.4
7.7
8.1
7.4
Standard Deviation Observed
7.0
7.2
7.3
7.6
7.2
Mean Error (ME)
-0.2
0.7
-0.4
0.0
0.6
ME Percent of Mean Obs.
-1.1%
3.8%
-2.0%
0.0%
Root Mean Square Error
(RMSE)
1.1
1.3
1.3
1.0
0.0
RMSE Percent of Mean Obs.
6.4%
7.2%
6.9%
5.2%
RA2 Correlation
0.97
0.98
0.98
0.99
0.98
eisk
Table 2-11. EFDC Simulation Water Temperature (deg C) Statistics, ModMon 180
tikN
eats
eAre
eStN
.ModMon 180•Bottom
ModMon.180 Surface
•
Statistic
Calibration.
1998 -.2000
Validation
2001.- 2006,
Calibration
1998 - 2000
Validation
2001 -.2006
Count
75
134
75
134
Mean Predicted
17.9
18.1
19.0
19.1
Mean Observed
17.9
18.4
18.4
18.7
Standard Deviation Predicted
6.7
7.2
7.2
7.9
Standard Deviation Observed
6.9
7.3
6.9
7.4
Mean Error (ME)
0.0
0.3
-0.6
-0.4
ME Percent of Mean Obs.
-0.2%
1.5%
-3.2%
-2.1 %
Root Mean Square Error (RMSE)
0.9
1.0
1.0
1.0
RMSE Percent of Mean Obs.
5.0%
5.2%
5.2%
5.2%
RA2 Correlation
0.98
0.98
0.99
0.99
2-23

f^
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.3 WASP72 MODEL DEVELOPMENT
The WASP6 program was used for the EPA TMDL work. The current version, WASP72, was used to
update the model. The past work will be used to inform the assignments of constants, input parameters,
and other input information. In the past, separate models had to be built one year at a time. However,
since time has passed and the models have improved, this limitation is not present anymore for the NRE
application. This represents a significant advancement in management of input files and time savings.
2.3.1 Hydrodynamic Linkage File
WASP can use a hydrodynamic linkage file which is produced by EFDC. The hydrodynamic linkage file
is referred to as the HYD file. The HYD file contains information such as cell geometry, velocity, water
temperature, salinity, depth and more which is passed to the WASP application and coupled to the water
quality simulation. The HYD file tends to be large, for the NRE application it is over 4 gigabytes.
2.3.2 Simulation Time and Print Interval
The simulation time and print interval are initially read into WASP when the HYD file is loaded. The
time step is also set during this process.
2.3.3 State Variables
The state variables selected for the NRE application are presented in Table 2-12. This selection reflects
the past EPA TMDL work and basic eutrophication. Salinity is not selected as it is already passed to
WASP by the HYD file.
Table 2-12. State Variables (Systems) Used in WASP for Neuse River Estuary Application
System Number
Name
Symbol
Units:
1
Ammonia
NH3
mgN/L
2
Nitrate
NO3
mgN/L
3
Organic Nitrogen
OrgN
mgN/L
4
Orthophosphate
PO4
mgP/L
5
Organic Phosphorus
OrgP
mgP/L
6
Chlorophyll a
Chia
pg/L
7
Dissolved Oxygen
DO
mg/L
8
Ultimate Carbonaceous Biochemical Oxygen Demand
CBODu1
mg/L
2.3.4 Parameter Data
The parameter settings in the NRE applications are seen in Figure 2-26. They represent the wind, light
extinction, benthic ammonia flux, sediment oxygen demand, and solar radiation; all inherited from the
EPA TMDL work.
2-24
("
tEkN
Pam'

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Paramet
Used Scale Factor
1 Segment Scale Factor for Wind Ix
2 Wind Speed Time Function to use for Se F 1.0000
3 Water Velocity Furetion (1.4) for Segmen E 1 0000
4 Temperature of Segment (Degrees C or Iv E 1.0000
5 Temperature Time Function for Segment f— 1.0000
6 Light Extinction for Segment (Per Day or I. (X - 1.0000
7 Light Extinction Time Function to use for I ( 1.0000
8 BOD(1] Decay Rate Scale Factor f 1.0000
9 BOD(2] Decay Rate Scale Factor f - 1 0000
10 B0D(3) Decay Rate Scale Factor • 1.0000
11 Benthic Ammonia Flux (mg/m2/day) fix 1.0000
12 Benthic Phosphate Fker (mg/m2/day) fX - 1.0000
13 Sedment Oxygen Demand (g/m2/day) ( • 0.8000
14 Sediment Oxygen Demand Temperature ( (x 1.0477
15 Incoming Solar Radiation (Langleys/day) (x 1.0000
16 Measured Segment Reaeration Rate (pc( I— 1.0000
17 Zooplankton Population r 1.0000
18 Fraction Light Intercept by Canopy f— 1 0000
19 Tsvigolo Escape Coefficient - 1.0000
20 Dam Elevation (meters) f— 1.0000
21 Dam Pool WQ Coefficent • 1.0000
22 Dam Type Coefficient E 1.0000
9'9 copy j 13 Paste I Q Fill/Calc,
// OK
Figure 2-26. Parameter Settings for WASP Application of Neuse River Estuary
2.3.5 Constants
The assignment of constants was performed by first using the values from the EPA TMDL work. The
values were revised if required through the iterative process of checking calibration/validation.
2.3.6 Loads
The four point sources were assigned constituent contributions through the Loads step of the Pre -
Processor. The data was developed in units of kg/d and an f-ratio of 2 (Chapra, 1997) was assumed to
convert all BOD5 values to CBODu. All four point sources were assigned a loading series for NH3,
NO3, OrgN, PO4, and CBODu. Only two, Weyerhaeuser Pulp and New Bern WWTP, were input for
organic phosphorus loading. The dissolved oxygen assignment to these waste streams were defined in the
Boundary Conditions step of the Pre -Processor (Section 2.3.8).
2.3.7 Time Functions
The Time Functions step of the Pre -Processor is where time series of weather and other variables are
defined. The weather series entered here include the daily solar radiation, daily fraction of light, daily
wind speed, and daily air temperature. The remaining time series defined in this step include the benthic
ammonia flux, benthic orthophosphate, and light extinction.
® TITRAT1CH
2-25

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.3.8 Boundary Concentrations
The development and assignment of boundary conditions in the Boundaries step of the Pre -Processor
represents a significant level of effort. There are 96 cells which require definition, each for the 8 state
variables used. This represents 768 time series that must be defined. However, the primary cells are
given the dominant attention. These may be considered in order as headwater, open boundary, point
sources, and remaining freshwater flow input.
The headwater cell representing the Neuse River input to the estuary is the largest fresh flow contributor.
Thus, particular effort was made to process and assign the boundary conditions using ModMon 0 (Figure
2-27).
The open boundary which is near Pamlico Sound was forced with monthly averages or constant values.
ModMon 180 was primarily used to develop the open boundary forcing.
As noted earlier, the water quality of the point sources were primarily entered as loads. However, the
dissolved oxygen assignment was entered as concentration. Furthermore, the chlorophyll -a was assigned
as zero pg/L.
Lastly, the remaining freshwater flow cells were assigned boundaries for the state variables as constants
by reviewing average characteristics observed at station NCDWQ J8770000.
a UNC-IMS
• NCDWQ
I Model Grid
RF3 Streams
Figure 2-27. Water Quality Boundary Stations for Model Input
2-26

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.4 WASP72 MODEL CALIBRATION
2.4.1 Nitrate
The simulation of nitrate is generally capturing the observed trend. There is a build up of concentration in
approximately December — March period and then near complete removal during the growing season.
.�. Figure 2-28 and Figure 2-29 show the time series comparison at ModMon 100 which is just west of the
bend. There is higher nitrate concentrations in the upper reaches of the estuary and much less in the lower
reaches. This is noted in Figure 2-30 and Figure 2-31 for ModMon 180 which is near Pamlico Sound.
The bend NCSU-CAAE stations of Cherry Point 34 and Minnesott 35 (Figure 2-32 and Figure 2-33)
compare well to the observed data.
aalso
0.;.
•
[:
•
Illio
■
.\
•
.
.
til"
Ito Figure 2-28. NO3 Calibration Comparison for 1998 — 2000 at ModMon 100
mak
aho
also
oalio
®mwntwa+
onto
Arno
Sot NO3 Imgt1LE
Bot H03 (mgH'L)
MODMOH.LONG100
2-27

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
■
!
i
.
■
I
■
. ■ • 1.
5
Ur.
{ I .
Lt
■ryx;
■u
�s
■■
S
■ I •
1'.
r•
■
■ •
2001
2002
2003
2004
2001-2006
2005
2000
Sot NO3 Might)
Bat H03 ImgN L)
• MODMON-LONG100
Figure 2-29. NO3 Validation Comparison for 2001 — 2006 at ModMon 100
0.11
0.3
0.7
0.5
0.I
0.3
02
0.1
0.0
i�
it(
1
,
�
iP�
i.
p,
• s�
a,.
1998
1999
1998-2000
2000
Sin NO3 pngH LI
Bnt NO31mON 11
• MODM0114.0NG180
Figure 2-30. NO3 Calibration Comparison for 1998 — 2000 at ModMon 180
TITRATICH
2-28
024
024
104
oft
eft
Aft
r•

a..
AMIN
,r.
ANN
ANA
ink
i► Figure 2-32. NO3 Validation Comparison for 1998 — 2006 at Cherry Point 34
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.9
0.8
0.7
0.6
0.5
0.1
0.3
02
0.1
0.0
r
2001
2002
2003
2004
2001.2006
2005
2006
Sal NO3 {mgN LI
Bnt H03 Itn9N1.)
• MODMON.LONt3180
Figure 2-31. NO3 Validation Comparison for 2001 — 2006 at ModMon 180
0.9
0.8
0.7
0.6
0.5
0.4
0.3
02
0.1
0.0
[ilk1,Hcir
■
I•
°!‘
■
I
'
`
I,7
41
i
,' ,.
1998 1999 2000 2001 2002 2003
1998-2006
2004
2005
2006
6111 NO3 0n0H LI
Bnt NO3 pugN L)
■ CHERRYPT.3-I
— TETRATSCH
2-29

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.9
0.8
0.7
0.6
0.5
0.1
0.3
0.2
0.1
0.0
i
1
Li
I
•
:i 1'II
N
■ 1
1
,
I'
iII
■
i`
i
.}
1998
1999
2000
2001
2002 2003
1998-2006
2001
2005
2006
Sou H03 pngN LI
Bot NO3 pngN LI
MINNESOTT-35
Figure 2-33. NO3 Validation Comparison for 1998 - 2006 at Minnesott 35
Model performance statistics are presented in Table 2-13 and Table 2-14. The surface simulation was
better than the bottom simulation. The EPA TMDL statistics are presented for comparison.
Table 2-13. WASP72 Simulation Nitrate (mgN/L) Statistics, ModMon 100
ModMon 100 Bottom
ModMon 100 Surface
ModMon 100
Surface
Statistic
Calibration
1998 - 2000
Validation
2001 - 2006
Calibration
1998 - 2000
Validation
2001 - 2006
EPA TMDL
1998 - 2000
Count
52
139
52
139
63
Mean Predicted
0.132
0.039
0.132
0.057
0.16
Mean Observed
0.098
0.023
0.154
0.061
0.15
Standard Deviation Predicted
0.196
0.088
0.207
0.101
0.23
Standard Deviation Observed
0.147
0.057
0.185
0.110
0.18
Mean Error (ME)
-0.033
-0.017
0.022
0.004
0.01
ME Percent of Mean Obs.
-33.7%
-74.9%
14.3%
7.3%
Root Mean Square Error
(RMSE)
0.129
0.077
0.125
0.099
0.00
RMSE Percent of Mean Obs.
131.5%
342.1%
81.4%
161.5%
RA2 Correlation
0.59
0.28
0.65
0.32
0.48
® ThT tAT CH
2-30

,,®, Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
rtZ:N Table 2-14. WASP72 Simulation Nitrate (mgN/L) Statistics, ModMon 180
exit
eStN
Om\
IgitN
•
ModMon 180 Bottom
ModMon 180 Surface
•
Statistic
Calibration
1998.- 2000
Validation
2001 - 2006
Calibration
1998 - 2000
Validation
2001 -.2006
Count
12
132
12
132
Mean Predicted
0.013
0.012
0.001
0.002
Mean Observed
0.002
0.004
0.002
0.005
Standard Deviation Predicted
0.006
0.007
0.001
0.006
Standard Deviation Observed
0.003
0.003
0.003
0.013
Mean Error (ME)
-0.011
-0.008
0.001
0.003
ME Percent of Mean Obs.
-453.3%
-206.3%
68.4%
66.4%
Root Mean Square Error (RMSE)
0.013
0.011
0.003
0.014
RMSE Percent of Mean Obs.
520.9%
277.0%
157.5%
265.7%
RA2 Correlation
0.06
0.00
0.00
0.02
2.4.2 Ammonia
The ammonia simulation is similar to nitrate in that the surface values decline during the growing season.
This was important to represent with respect to the dissolved oxygen and chlorophyll -a response
variables. The bottom simulation was more challenging likely due to the significant and complex benthic
fluxes associated with the NRE. The model is generally oversimulating NH3 concentrations in the
- bottom layer of the water column, perhaps as a function of the approximation of the benthic forcing.
However, the more important response variables (DO and chl-a) behave reasonably and the surface
ammonia simulation appears representative. These observations are more evident in ModMon 100
(Figure 2-34 and Figure 2-35) and ModMon 180 (Figure 2-36 and Figure 2-37), perhaps due to a
combination of the benthic NH3 forcing and/or depth of cell. The comparisons at Cherry Point 34 (Figure
2-38) and Minnesott 35 (Figure 2-39) appear to perform better than the other two locations from time
series inspection.
AWN
eloN
ificN
nrnuersai
2-31

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
V4. l
---0.,,,,
•i jj%jjj
A'
'.�
•ilp11M4�.
Sty phi
did.
•
•.r
.314
•r a�
_ i ` Li`
•
**.�
� �'Mlititi■'i:
ji
SA 11.'r•
L
1998
1999
1998-2000
2000
Stu NH3 OngU LI
Bot NH3 I11i0N LI
• MODMON.LONG100
• MODMOH.L01G100
Figure 2-34. NH3 Calibration Comparison for 1998 — 2000 at ModMon 100
0.8
0.7
0.6
0.5
0.4
0.3
02
0.1
0.0
•
r
•
•
■
•
•
■
■
.A'
.U..
1
14
1'i7.�
•
•
t
, j ,J
2001
2002
2003
2004
2001-2006
2005
2006
Sul NH3 (ingN LI
Bot NH3 (tngN L)
• MODMON.LONG100
• MODMON.LONG100
Figure 2-35. NH3 Validation Comparison for 2001 — 2006 at ModMon 100
rsrttAT•0-1
2-32

Alms
•
b
4144
ark
a► Figure 2-37. NH3 Validation Comparison for 2001 — 2006 at ModMon 180
Ash
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.8
0.7
0.G
0.5
0.J
0.3
0.2
0.1
0.0
1998
1999
1998-2000
2000
Sat NH3 ImgN LI
Bot NH3 Itn9H L1
• MODMOH.LOHG180
■ MODMON-L0NG180
Figure 2-36. NH3 Calibration Comparison for 1998 — 2000 at ModMon 180
2001
2002
mi.414.4.0 II
2003 2004
2001 - 2006
2005
200G
Sat NH3 000 LI
Bot NH3 119N LI
• MODMON4W111;180
• MODMON-L01113180
alk
4114 ® TUThA 1o1
2-33

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
■•
■
1998
1999
2000
2001
2002 2003
1998-2006
2004
2005
2006
Su, NH3 OngH LI
Bot NH3 II141 LI
• CHERRYPTJJ
• CHERRYPTJJ
Figure 2-38. NH3 Validation Comparison for 1998 — 2006 at Cherry Point 34
0.8
0.7
0.6
0.5
0.1
0.3
0.2
0.1
0.0
19,10
1999
2000
2001
■
■
2002 2003
1998-2006
2004
2005
2006
Sut NH3 ImgN.11
Bot NH3 pngN L)
• MINNESOTT35
• MINNESOTT35
Figure 2-39. NH3 Validation Comparison for 1998 — 2006 at Minnesott 35
®mnAThcH
2-34

rzts
rats
elaN
AaN
MIN
eXLN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Model performance statistics are presented in Table 2-15 and Table 2-16 for ModMon 100 and ModMon
180. The EPA TMDL statistics are presented in Table 2-15 for comparison.
Table 2-15. WASP72 Simulation Ammonia (mgN/L) Statistics, ModMon 100
ModMon 100.Bottom
ModMon 100.Surface
ModMon 100
. Surface
Statistic
Calibration. ,
1998 - 2000 .
Validation
2001- 2006
,Calibration
1998 -:2000
Validation
2001 - 2006 ti
EPA TMD
1998,- 2000
Count
77
150
77
150
75
Mean Predicted
0.092
0.063
0.031
0.014
0.05
Mean Observed
0.035
0.049
0.025
0.019
0.02
Standard Deviation Predicted
0.077
0.043
0.039
0.016
0.04
Standard Deviation Observed
0.029
0.082
0.027
0.026
0.03
Mean Error (ME)
-0.057
-0.014
-0.006
0.005
0.03
ME Percent of Mean Obs.
-161.2%
-29.2%
-25.4%
27.6%
Root Mean Square Error
(RMSE)
0.088
0.074
0.035
0.030
0.00
RMSE Percent of Mean Obs.
251.5%
150.7%
141.2%
156.7%
RA2 Correlation
0.22
0.21
0.25
0.00
0.00
Table 2-16. WASP72 Simulation Ammonia (mgN/L) Statistics, ModMon 180
ModMon 180 Bottom
ModMon 180 Surface
Statistic
Calibration
1898 - 20•00
Validation
2001.- 2006
Calibration
19•98 - 2000.
Validation
2001 - 2006
•
Count
12
132
12
132
Mean Predicted
0.075
0.070
0.008
0.009
Mean Observed
0.034
0.022
0.012
0.014
Standard Deviation Predicted
0.025
0.027
0.008
0.009
Standard Deviation Observed
0.028
0.027
0.004
0.009
Mean Error (ME)
-0.041
-0.048
0.004
0.006
ME Percent of Mean Obs.
-119.5%
-222.6%
35.2%
39.1%
Root Mean Square Error (RMSE)
0.049
0.055
0.010
0.014
RMSE Percent of Mean Obs.
144.3%
255.9%
79.3%
100.8%
RA2 Correlation
0.17
0.25
0.03
0.00
,
,A‘ ®mRwT1101
MAN
2-35

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2.4.3 Orthophosphate
The observed data generally shows a similar and consistent annual trend in orthophosphate, likely due to
benthic releases coincident to high temperature and low oxygen periods in the estuary. There is a buildup
of orthophosphate from approximately the middle of summer through the fall and then a decline during
the winter period. However, the magnitudes of the simulation are generally less than the spikes shown in
the observed data. This may be explained by multiple considerations, among them are the general
assignment of water quality forcings based on observed data at one to two times a month in contrast to the
complex phenomena that make up the NRE. Figure 2-40 and Figure 2-45 show the time series
comparisons.
0.5
0.1
0.3
0.2
0.1
0.0
•
•
le
' A
•
•
sass
••�
•
•
Os
1998
1999
1998-2000
2000
Sul PO4 ImgP.L1
Bot POl ImgP'LI
MODMOH.LOH ,100
Figure 2-40. PO4 Calibration Comparison for 1998 — 2000 at ModMon 100
(i)
THTRATiCH
2-36

.+w
oak
Amk
�'► Figure 2-41. PO4 Validation Comparison for 2001 — 2006 at ModMon 100
416,
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.5
0.4
0.3
0.2
0.1
0.0
•
■
•
■
•
■
■
■■
■
■
■
B.
•
■
■
■
r
r
2001
2002
2003
2004
2001-2006
2005
2000
Sul PO4 ImoP 1.1
Bot PO4 IInIP LI
• MODMO114.0110100
aft
sok
dria
XMk
AMik
41.11,
Oak
Ilk
ink
0.5
0.J
0.3
0.2
0.1
110
s'
.0II
., f,,. ,, 1
•
.14)0264,m.se....11,...,,N,;km
1998
1999
1998-2000
2000
Sm PO4 Ini.P LI
Bot PO4 1mgP L1
• MIIDMON-LOH6180
Figure 2-42. PO4 Calibration Comparison for 1998 — 2000 at ModMon 180
,^ tUT*A ICH
2-37

Pik
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.5
0.1
0.3
0.2
0.1
0.0
■
•
•
2001
2002
2003
2004
2001 - 2006
2005
2006
- - Su: PO4 Im9P LI
Bot PO4 11n9P LI
• MOBMON-1ON1;180
r
Figure 2-43. PO4 Validation Comparison for 2001 — 2006 at ModMon 180
ink
AN le,
0.5
0.1
0.3
0.2
0.1
0.0
■
.
1 i
4il
1
+
.
.
19J8
1999
2000
2001
2002 2003
1998-2006
2001
2005
2006
Sol P01 Irn9P LI
Bot PO4 Iw9P'LI
• CHERRYPT-34
Figure 2-44. PO4 Validation Comparison for 1998 — 2006 at Cherry Point 34
04
2-38

riMiks
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
0.5
0.,
0.3
0.2
0.1
0.0
■
■
•
•
■
i
91
■
1998
1999
2000
2001
2002 2003
1998-2006
2004
2005
2006
Sul PO4 {mgP LI
Bot PO4 ImgP LI
■ MINNESOTT35
Figure 2-45. PO4 Validation Comparison for 1998 — 2006 at Minnesott 35
2.4.4 Dissolved Oxygen
The dissolved oxygen simulation appears reasonable (Figure 2-46 through Figure 2-51). The vertical
stratification is frequently bound in the observed profiles. It is noted that for the four locations reviewed
across 9 years, there is frequent and recurring low dissolved oxygen in the bottom portions of the water
.•, column as well as depressed surface values.
lank
/1114
oak
IOW
AIN
20
18
16
14
12
10
8
6
2
0
■
1
P "t
' 4, '
: ■
.1
IT
. ;; ' ,
II . ■ ■ 1 r i
r ;'"■
�. . ■
,
!i z �'' ■ ■ �� � etlia1
��
1
1 ff -.., �.,
•,,„,,
is a ■
II i
1
III' ■
iv
IIIIWII
iipliami;1„;T
•
1998
1999
1998-2000
2000
Sin CO ling LI
Bo' D0 long LI
• MODNION10NG100
Figure 2-46. DO Calibration Comparison for 1998 — 2000 at ModMon 100
-� TWTTLATSCli
2-39

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
20
18
10
14
12
10
8
4
2
0
2001
■•
1
■
IC
Igrikliftilk
I
'
.'11-"1411 IV
'7'
-
..ifil
•
■
■ ■ •
wile
•
N.
■
■
2002
2003
2004
2001-2006
2005
2006
Sol DO Ong LI
Bot DO Inig LI
• MODMON-LONG100
Figure 2-47. DO Validation Comparison for 2001 — 2006 at ModMon 100
20
18
16
14
12
10
8
G
4
2
0
■
7 n r 'ILI ■
Yle iLiiifr'lY'
�1
• 1
F 1'...
1■�
i
IIFi
■
•• •
•
t ■
II
•
1
••
1998
1999
1998-2000
2000
SIR DO ling LI
Bot DU Img LI
• MODMON10N6180
Figure 2-48. DO Calibration Comparison for 1998 — 2000 at ModMon 180
®T.TNAT■QI
2-40

Mik
ono
Oak
Ago
rank
411.
Ale
/14
401811,
Figure 2-50. DO Validation Comparison for 1998 - 2006 at Cherry Point 34
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
20
18
16
14
12
10
8
6
4
2
0
2001
F
II/.•
i
` .ItJi1�'
B_
'
driW
1
d..i
r
nt
1Jr,
�h1
11
1
■
■
1
B •
■
2002
2003
2004
2001-2006
2005
2006
Sot DO (mg LI
Bot D0 )mg t)
• MODMON10NG180
Figure 2-49. DO Validation Comparison for 2001 - 2006 at ModMon 180
m
IS
16
i
Mane,ti
,� ' .
,
�
1oID�i�Y(�.,I
1:�11I1{ttt�
lu
1 ` �1
�+
t,R
� `'�A
ll _t
1i-.1i��"r,,
it ., '
�t� .,'
6lif+,',.
I'Iill
•.r :
, ,III.
'' 3.1'
.1
• ill,
II
•
2
,,,
19.18
1999
2000
2001
2002 2003
1998-2006
2001
2005
2006
Sut DO png L1
Boy DO pug LI
■ CHERRYPT-34
nTITRM„CH
2-41

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
20
18
16
14
12
10
8
6
4
2
,..,lr wi, !WAN,.
itilirk
IP1r� !�li:- �� �I''� 71:411 ,�I ' 'II ►11: �k 1L PlIlr .
w� ,
I 1011111111114.1111 ; MIS
�tllILLIE111111111111111111,111111
1998
1999
2001
2002 2003
1998-2006
2004
2005
2006
... Stu DO pu9 LI
Bot DO i1119 u
MIHNESOTr35
Figure 2-51. DO Validation Comparison for 1998 - 2006 at Minnesott 35
The statistics (Table 2-17 and Table 2-18) indicate better agreement in the surface layer of the water
column than the bottom layer.
Table 2-17. WASP72 Simulation Dissolved Oxygen (mg/L) Statistics, ModMon 100
ModMon 100 Bottom
ModMon 100 Surface
ModMon 100
Surface
Statistic
Calibration
1998 - 2000
Validation
2001 - 2006
Calibration
1998 - 2000
Validation
2001 - 2006
EPA TMDL
1998 - 2000
Count
154
152
154
152
268
Mean Predicted
5.5
6.0
9.3
9.3
9.1
Mean Observed
5.9
5.8
9.3
9.9
9.2
Standard Deviation Predicted
2.8
3.0
1.8
1.8
1.6
Standard Deviation Observed
3.1
3.6
2.1
2.1
2.1
Mean Error (ME)
0.4
-0.2
0.0
0.6
-0.1
ME Percent of Mean Obs.
6.3%
-3.1`)/0
-0.5%
6.5%
Root Mean Square Error
(RMSE)
3.1
2.0
1.4
1.4
0.1
RMSE Percent of Mean Obs.
52.6%
35.1%
15.0%
14.2%
RA2 Correlation
0.21
0.67
0.58
0.63
0.56
®17T1iATKJi
2-42

lagtiN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-18. WASP72 Simulation Dissolved Oxygen (mg/L) Statistics, ModMon (At\
AWN
eAt
tgEN
em1
t1
eltN
ez1
tlieN
I
ModMon 180 Bottom
ModMon 180 Surface
Statistic
Calibration
1998 - 2000
Validation
2001 -2006
Calibration
1998 - 2000
Validation
2001 - 2006
Count
75
132
75
132
Mean Predicted
6.1
5.8
8.9
8.7
Mean Observed
7.0
7.3
9.2
9.0
Standard Deviation Predicted
2.6
2.6
1.5
1.5
Standard Deviation Observed
2.5
2.7
1.8
1.6
Mean Error (ME)
0.9
1.5
0.3
0.2
ME Percent of Mean Obs.
12.8%
21.0%
3.7%
2.5%
Root Mean Square Error (RMSE)
1.7
2.0
1.0
0.6
RMSE Percent of Mean Obs.
24.9%
27.3%
11.3%
6.3%
RA2 Correlation
0.68
0.78
0.68
0.90
ex\ 2.4.5 Chlorophyll -a
The NRE is a complex waterbody with many phenomena affecting the dissolved oxygen and
eatN phytoplankton kinetics. Key factors affecting the NRE are multiple phytoplankton species, significant
benthic fluxes, long residence times, shallow nature, and nutrient/light limitations. The model was
developed with the best use of the observed water quality data which were typically one to two
emN observations per month.
Four stations were reviewed for chlorophyll -a observations, they were UNC-IMS ModMon 100 and
ModMon 180 and NCSU-CAAE Cherry Point 34 and Minnesott 35. Three of those four stations are near
the bend. The bend observations indicate algal activity that exceeds 40 µg/L, with some values of two,
three, and more times that value.
,aN The chlorophyll -a simulations show the trends and typical magnitudes present in the observed data but
under -predicts the spikes of the observations (Figure 2-52 through Figure 2-57). The representation of the
trends and typical magnitudes is meaningful for utility of the model in evaluating scenarios. It is noted
that the observed water quality used to force the model is typically one to two observations per month.
The freshwater flow and open boundary water surface elevation forcings are daily while the weather
inputs are hourly. This is contrasted with the under -prediction of observed spikes in that the primary
utility and service of the model is present. That is the model appropriately represents a reasonable
phytoplankton response to the key factors of the NRE. The statistics from comparison of the simulation
to the observations are presented in Table 2-19 and Table 2-20.
e
e
2-43
elitN

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
.oU
!GO
!10
!20
1.00
180
IG0
110
120
100
80
60
■
■
■
■
.
j °n
■■ ■
�1!}
■
20
n
i4M
% 1mt `�`/
•
i
■
■
1
"1K:.
y
is
y
. w■ 1!
ft
1998
1999
1998-2000
2000
Sue Chla l"g L1
Bot Chla lug Li
• MODMON-LONG100
Figure 2-52. ChI-a Calibration Comparison for 1998 — 2000 at ModMon 100
280
260
240
220
200
180
1G0
140
120
100
80
G0
40
20
0
•
•
■
■
•
■
■
■
I.
■
■
•
.
■
■
.
,
■
■
1
me
1'i•
'ac. ■ •
,I■1 f ;.0 i:
M.
•
4
.0
2110
. ■ 1
..sr,,AV
}
'12
' it
ILi
■.r.4
t+ itir•I ;r
v" 'hrq
?r -
'- Mi.,r.,
- kj,%g1 - •— 'Pi'
2001
2002
2003
2001
2001-2006
2005
200G
Sul Chla lugL1
Bot Chla ¢ig Ll
• MODMON-LONG100
Figure 2-53. Chl-a Validation Comparison for 2001 — 2006 at ModMon 100
n
2-44

AIM
AMIN
4111.,
ANN
r
010,
oak
AMIN
AMIN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0
1998
,lam
1•1,'•
�•
. ■
■
I'
t.
1999
1998-2000
2000
Sw Chia Ing LI
Bot Chla pig LI
• M00MON-L0NG180
Figure 2-54. Chl-a Calibration Comparison for 1998 — 2000 at ModMon 180
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0
•
■
•
-•-
2001
2002
2003
2004
2001-2006
2005
2006
Sul Chia 109 11
Bot Chla lug LI
■ MODMON-LONG180
Figure 2-55. Chl-a Validation Comparison for 2001 — 2006 at ModMon 180
® TTT AThc
2-45

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
280
260
240
220
200
180
IG0
110
120
100
80
60
40
20
0
•
1
•
.
■
.
.
■
•
■
.
F
a
-
■•
■
I,
..
, . ti •
...-i
,, ' ti• 7try,•'•..1.T.
,A. i
Al ,
. V ''
if. '?q
-
7
, r
.: - 6 v11"
, ;I,
1998
1999
2000
2001
2002 2003
1998-2006
2004
2005
2006
Sot Chia tog L1
Bot Chia lug LI
• CHERRYPT.31
Figure 2-56. ChI-a Validation Comparison for 1998 — 2006 at Cherry Point 34
280
260
240
220
200
180
160
140
120
100
80
60
10
20
0
1998
•
•
■
■
•
■
•
■
i r
•
■
■
i
'el
,
•
';�efi..
fi,
.�
L, (
i�ati�
M •; • ,�t',4AP
7„0. zik,-.1
' ti,i .
1999
2000
2001
2002 2003
1998-2006
2004
2005
2006
Sin Chia lug LI
Bot Chia lug LI
• F1IHHESOTT35
Figure 2-57. ChI-a Validation Comparison for 1998 — 2006 at Minnesott 35
TITILATSOI
2-46
/"'
eft
011,
eft
Oft
oft
eft
ook
oft
oft
oft
oft
oft
eft
oft
oft
oft
t^
eft
eft
eft
oft
oft
eft
eft
oft
Aft
P•

el IN
rN
tgaN
rat
/sur
rN
el Ks,
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 2-19. WASP72 Simulation Chlorophyll -a (pg1L) Statistics, ModMon 100
-ModMon 100 Bottom
ModMon 100 Surface
ModMon 100
Surface
Statistic
Calibration
1998 - 2000
Validation *,
2001 - 2006' '
Calibration..
1998 - 2000.
Validation
2001 - 2006'
EPA
1998 - 2000
Count
77
150
77
150
75
Mean Predicted
10.5
11.2
20.7
22.0
16.3
Mean Observed
13.9
23.3
18.8
27.9
19.1
Standard Deviation Predicted
5.8
3.5
10.5
9.1
9.1
Standard Deviation Observed
12.5
28.3
17.5
28.0
17.5
Mean Error (ME)
3.4
12.1
-1.9
5.9
-2.8
ME Percent of Mean Obs.
24.6%
51.9%
-10.1%
21.1
Root Mean Square Error
(RMSE)
11.8
30.7
16.0
29.1
2.6
RMSE Percent of Mean Obs.
85.2%
131.7%
84.9%
104.3%
RA2 Correlation
0.17
0.00
0.19
0.01
0.21
Table 2-20. WASP72 Simulation Chlorophyll -a (pg/L) Statistics, ModMon 180
ModMon 180 Bottom
ModMon 180 Surface
Statistic
Calibration
1998 - 2000
Validation
2001 - 2006
Calibration
1998 - 2000
Validation
2001 - 2006
Count
12
132
12
132
Mean Predicted
5.3
5.2
10.9
12.6
Mean Observed
9.2
10.2
16.1
13.3
Standard Deviation Predicted
1.1
1.3
2.6
3.9
Standard Deviation Observed
2.8
5.2
9.7
14.2
Mean Error (ME)
3.9
5.0
5.2
0.7
ME Percent of Mean Obs.
42.1%
49.1%
32.4%
5.4%
Root Mean Square Error (RMSE)
4.6
7.3
10.3
13.3
RMSE Percent of Mean Obs.
49.7%
71.6%
63.9%
100.1%
RA2 Correlation
0.20
0.00
0.09
0.12
2.5 DISCUSSION
,fa The EFDC simulations appear reasonable based on salinity and water temperature. This is important as
the hydrodynamics alone are significant, while they are also part of the underpinning for the WASP
riaN application through the HYD file.
mntatuai
2-47
101

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The WASP simulations capture dissolved oxygen well. The chlorophyll -a simulation and the related
nutrient simulations represent appropriate trends and general magnitudes which are relevant for use of the
model in investigating scenarios, but at times under -predicts peak events. Water quality simulation
improvements may be related to the benthic assignments, constants, temporal forcings or other input
function. It is noted that the NRE is a complex environment and more than one assemblage of
phytoplankton is dominant in different portions, for example in the upper reaches where the environment
is fresher and more nitrogen limited as compared to the area near Pamlico Sound which has higher salt
content. The revisions of the larger TMDL model produced satisfactory performance when compared to
the original EPA TMDL work (simulation years 1998 — 2000).
2-48

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
3 Nested Model
A nested model was developed to represent finer grid resolution of the larger TMDL model for the
investigation of effluent plumes for Havelock and MCAS CP. This presented many technical challenges
as there were no similar nestedapplications that had been developed previously. Nonetheless, all
technical challenges were handled satisfactorily. The nested model will be used to compare on a relative
basis the scenarios with the proposed relocated Havelock discharge to a scenario without the discharge.
3.1 APPROACH
The primary focus of the approach was to capitalize on the existing larger model applications, which were
used for the TMDL. These models served as the basis to force the open boundary of the nested grid. The
approach included the following general steps:
• Select a study area to make a finer grid.
• Determine a summer and winter critical period.
• Pass state variable time series from the larger to the nested grid.
• Consider three phases for the proposed Havelock expansion.
• Consider permit conditions for the representation of MCAS CP WWTP.
3.2 NESTED GRID
The larger grid was developed for the TMDL analysis for the NRE from New Bern to Pamlico Sound.
The current study is focused on a small fraction of that area and at a finer resolution, 3.5 square miles (9.1
sq km) compared to 211 sq miles (546 sq km). The larger grid in the study area has horizontal cell
dimensions of approximately 5,300 feet by 2,759 feet (1,624 m by 841 m). Thus the study area was re-
gridded with horizontal cell dimensions of approximately 532 feet by 420 feet (162 m by 128 m).
Considered another way, one horizontal cell of the larger grid was broken into 60 cells for the nested grid,
substantially increasing the grid resolution. This allowed better representation of the boundary between
land and water, particularly around the confluence of Slocum Creek to NRE.
The focus of this study was the proposed Havelock outfall. However, careful consideration was applied
to the existing MCAS CP outfall due to proximity and potential interaction.
The depth of the ambient (receiving water) is important in a mixing analysis; the depths near the proposed
Havelock outfall and the existing MCAS CP were held as a priority. Chart number 11552 from NOAA's
Office of Coast Survey was used to make a best estimate of the bottom elevation of the study area and
thus ambient depths for the nested grid near the outfalls, approximately 12 — 13 feet (3.7 — 4.0 m).
3.3 CRITICAL PERIODS
3.3.1 Flow
Ambient flow conditions are an important component of a receiving water modeling analysis. Generally,
ow ow an • low velocity are a ' opte . for the critical condition. riverine environments the lowest
7- • a • : = ' : • ' a return"inierva o once in 1 years (7Q 10) is typically used. In an estuarine
environment, like the NRE, the determination of a critical flow condition is less straightforward.
ma►
3-1

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The current NPDES permit for Havelock has both summer (April through October) and winter
(November through March) limits, which is also the case for the MCAS CP permit. This study required
the development of two critical periods (summer and winter) with consideration for flow, water
temperature, salinity, and wind in the Neuse River Estuary (NRE).
Two USGS stream observation stations were used to develop the mode! flow forcing for the NRE
application. They were the Neuse River near Fort Barnwell and the Trent River near Trenton (Table 3-1).
Table 3-1. Monthly Average MCAS Cherry Point and City of Havelock Permit and Performance
Information
Name
USGS ID
Drainage Area (square miles)
Begin Date
Neuse River near Fort Barnwell, NC
02091814
3,900
October 01, 1996
Trent River near Trenton, NC
02092500
168
January 01, 1957
As a consequence of drainage area, the daily average stream flow record at the Neuse River near Fort
Barnwell will be more informative for evaluating low flow periods. The drainage area at this location is
approximately 78 percent of the total drainage area to the NRE. The daily average stream flow record at
Trent River near Trenton was also reviewed for comparison purposes. The 30-day moving average of the
data for each station was plotted in a time series (Figure 3-1). The use of a 30-day moving average allows
for elucidation of prolonged periods of a low flow condition and a sense of the magnitude. Figure 3-1
was inspected and periods near November 2001 (winter) and July — August 2002 (summer) were
identified for further evaluation. They are presented at a finer a time scale in Figure 3-2.
30•Day Moving Average Flow (cros(
1/1998
1/1999
1/2000
1/2001
1/2002
1/2003
1/2004
-Neese R (02091814) -Trent R (02002500)1
1/2005
1/2008
Figure 3-1. 30-Day Moving Average Flow for Stations 02091814 and 02092500
TWIWATIICH
3-2

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
30-Day Moving Average Flow (cros)
10
0.1
L
r r
H
4-
L
r
t-
0.01 1 1 I 1 I 1 1 1 1 I
9/1/2001 10/1/2001 11/12001 12/12001 1/1/2002 2/1/2002 3/12002 4/1/2002 5/1/2002 8/1/2002 7/1/2002 8/1/2002 9/1/2002
—Neuse R (02091814) —Trent R (02092500)
Figure 3-2. 30-Day Moving Average Flow for Stations 02091814 and 02092500, 2001 - 2002
The Neuse River near Fort Barnwell station represents the majority of freshwater input to the NRE and
drains a large area that extends well up to the City of Raleigh. However, the remaining local drainage to
the NRE should still be considered in case there was a period with noteworthy localized rain immediate to
the NRE. The record at Trent River near Trenton was used as a surrogate to evaluate the local condition.
As noted in the 30-day moving average at the Neuse River near Fort Barnwell, the magnitude of flows
near November 2001 is approximately the lowest when compared to other years for the same month.
Furthermore, the Neuse River near Fort Barnwell record shows a declining 30-day moving average
progressing into November 2001.
Leading into the summer of 2002, the Trent River near Trenton record shows a two order of magnitude
decline in the 30-day moving average, leading to the lowest 30-day moving average value for the 1998
through 2006 period. This observation is used as a surrogate for the local drainage area to the NRE and
corroborates the low flow period noted in Neuse River near Fort Barnwell for summer 2002.
3.3.2 Water Temperature
Water temperature is an important parameter because it influences water density, dissolved oxygen (DO)
saturation levels, and estuary kinetics. For DO, warmer temperatures are considered more critical. The
permits of each MCAS Cherry Point and Havelock were written with summer and winter specifications.
It was anticipated that the annual trend of water temperature would not vary from year to year as
meaningfully as salinity. Two stations were reviewed for water temperature, station Bullseye-33
maintained by NCSU — CAAE and ModMon 100 maintained by UNC-CH IMS. Bullseye-33 is located
approximately 50 — 100 meters from the existing MCAS Cherry Point outfall and ModMon 100 is located
northeast of the existing MCAS Cherry Point outfall by approximately 1.2 miles (2 km) (Figure 2-7).
Temperature data for the 1998 through 2006 period are plotted in Figure 3-3 and Figure 3-4 for the two
stations respectively. Finer scale graphs for the flow periods of interest are provided in Figure 3-5 and
Figure 3-6 respectively.
3-3

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
2002 2003
1998-2006
2001
2005
2006
Bottom Temp ICI
Suifece Temp ICI
• BULLSEYE33
Figure 3-3. Water Temperature at Bullseye-33, 1998 - 2006
2002 2003
1998-2006
2005
2006
Bnnnm Temp ICI
Sulfate Temp IC)
• MOUMON-LOH6100
Figure 3-4. Water Temperature at ModMon 100, 1998 - 2006
nTITRATIICH
3-4

a
.41111,
.411111,
nalk
Aft
4110,
lk
Figure 3-6. Water Temperature at ModMon 100, September 2001 — August 2002
Ask
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
40
30
20
10
0
Sep
M
1
■
L'M
'I ,'I
Oct
Nov Dec
Jan Feb M n An MI)?
September 2001 - September 2002
Joni
Jd
A ng
Sep
Bottom Temp ICI
Surface Temp ICI
• BULLSEYE33
Figure 3-5. Water Temperature at Bullseye-33, September 2001 — August 2002
.10
30
20
10
0
Sep
I•
1
1
:si011iLa
•
f
Oct
Nov Dec J. Feb Mu A Miy Jun Jd Aug
September 2001 - September 2002
Sep
Bottom Temp ICI
Surface Temp ICI
• MODM011.10116100
41116,
„— TfmuT■of
3-5

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The month of November 2001 appears to be relatively consistent and the warmer part of the winter
period. The data show that the summer of 1998 was the hottest according to the Bullseye-33 station, but
that was not the same at ModMon 100. Regarding flow, the summer of 1998 was a low flow period as
seen in Figure 3-1, however, the summer 2002 period was deemed to be a lower low flow period.
The review of water temperature indicates that the selection of approximately July — August 2002
(summer) and November 2001 (winter) should be reasonable to represent critical conditions.
3.3.3 Salinity
The same locations used to review water temperature were used to review salinity (Figure 3-7 through
Figure 3-10). Salinity is much more complex in the NRE. Generally the end of 1999 and the end of 2002
through 2003 were high flow periods. As such, the salinity was basically forced out of the NRE. Since
the NRE is poorly connected to the open ocean, has a small tidal range, and a long residence time, it takes
substantial periods of average to low flow conditions to build up the salinity concentration. This can be
seen by reviewing the period after the end of 1999, where there is a general increase in the salinity
concentrations through summer 2002. The range of salinity around November 2001 is similar to other
years for the same month.
The review of the salinity information indicates it is reasonable to adopt approximately November 2001
(winter) as a critical condition as the salinity range is similar to other years for the same month in the
1998 to 2006 period. While the salinity values at each station are highest for the 1998 through 2006
period in summer 2002, they are still reasonably close to other summer high salinity concentration periods
(lower freshwater flow), within approximately 2 PSU. Nonetheless, the salinity data also support the use
of July — August 2002 for the summer critical period.
26
26
24
22
20
18
16
14
12
10
8
4
2
0
.
�■-ii
:g
_•��
•
11
ice
�ut
.
Illitir.il
rll~,�
Ai
t ii i •
•'J
• :.
` .
-.1,
fir .
l
F.
Itii. 31
.1
ill Ti
■'�ri
ui Ail
rl,
'M
MN
17-t•
FE 11.11i,
�C 'AL
i 1E lei
LIIIIIMilliMika!,
1 tr1Ai)
AIL i.I
rimumulumt,
m
ais.1:lu
19.18
1999
2000
2001
2002 2003
1998-2006
2001
2005
2006
Bosom SaI IPSU}
Smfaca SaR(PSU}
• BULLSEYE33
Figure 3-7. Salinity at Bullseye-33, 1998 - 2006
nTUTRATICH
3-6

Jab
/\
rc�
ink
aka
Ask
Aft
Figure 3-9. Salinity at ModMon 100, 1998 - 2006
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
28
26
24
22
20
18
16
11
12
10
8
6
4
2
0
II
■
I
■1
■
■
II
■
•
•
4\
Ill
.a
■■
; ■
,
it
'
•
Jai 01 Ap 01 Jill 01 Oct 01 Jan 02 Ap 02
2001-2002
Jo102
Ot 02
Bottom Salt IPSUI
Sulfate SaltlP$Ul
• BULLSEYE-33
Figure 3-8. Salinity at Bullseye-33, 2001 - 2002
28
2G
21
22
20
18
16
11
12
10
8
6
1
2
0
1998
■11■
;
■iti
i
■
�w
■ ■
Yt 1��'■��
�w ,■w.
ear
Pi- ? l�
11
MR
.!1
11
1I11 oil
1'
a
--a
PI" i
1 i
t,1 ■•
■
■��■�■��{ti1.
�7S4�j111/
RIFIFPIr
1 1
] �yy�''�y
SI `11
I, Nel,,'
■y��
;
iti
TT11-0,,, Millhh�.
i.-Li
11ki1:''W.
AlII �Er1
S'I-{N{.�� i 1� l
1
14,1n •-II�,'IH.I',
l�', Mi
91E1 �‘
1 I , ! / l• iJ
��k,t`Ii�.''ii II
1I I
' 11..iAari ilE
.i.1
i i 1J,2it4f��.IIL'JIl
it ''
■ ifii�i'
I 1•11
;i11I:
i
11
=i T.fi
Itf =MIAMI
V1� U�ta■IIi�l�I
t
IiI'«
1999 2000
2001
2002 2003
1998-2006
2001
2005
2006
Bottom Salt IPSUI
Sulfate SaIfPSU1
• M00M0N-LONG100
016.
4014

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
26
24
22
20
18
16
14
12
10
8
6
2
0
■
■
•
•
la
-
•
:
1
1
, ,
, `
■
■
■
11416
it--1
\ii
;,a•ILL-It
i
}
'H. r
Sep
Oct 11.v Dec J.a Feb Mii A,t May Jun J 11 Aug
September 2001 - September 2002
Sep
Bottom Salt IPSUI
Surface SaItiPSUi
• MODMON-L011G100
Figure 3-10. Salinity at ModMon 100, 2001 - 2002
3.3.4 Wind
The NRE is unique in its generally shallow depth with large surface area. Wind is a significant factor
influencing the hydraulics of the NRE. Additionally, wind can be an important factor for DO analyses in
large open water systems like the NRE. Therefore, the average monthly wind speed for each year was
reviewed as well as comparing to the overall average wind speed by month for the total period of 1998
through 2006.
Table 3-2. Wind Forcing Summary
Month
Average Wind Speed (1998 - 2006) (mint)
January
10.1
February
10.2
March
10.7
April
11.5
May
9.9
June
8.6
July
7.9
August
7.8
September
9.4
October
8.1
November
8.4
December
9.1
TrrRAT10i
3-8
Oft
Oft
Oft
e-
e-
r
Oft
oft

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The November 2001 monthly average wind speed was 8.1 miles per hour (3.6 m/s). The June, July, and
August 2002 monthly average wind speeds were 9.5, 8.3, and 8.7 miles per hour (4.2, 3.7, and 3.9 m/s),
respectively. None of these deviations from the 1998 through 2006 monthly averages are substantial.
The review of the wind record on a monthly basis does not present a substantial reason to avoid the
proposed periods for the respective critical conditions.
3.3.5 Discussion
An existing conditions model framework (1998 through 2006) was evaluated for determination of suitable
conditions to represent critical winter and summer conditions. The selection of approximately July —
August 2002 (summer) and November 2001 (winter) to adopt as critical conditions was evaluated for
flow, water temperature, salinity and wind. The approximate periods were determined to be reasonable
for critical conditions within the period of construction for the model. A further evaluation to focus
within or around these periods was assessed during evaluation of model application results.
3.4 LARGER TO NESTED ASSIGNMENTS
A cornerstone component of this study was to capitalize on the larger model developed for the NRE in
order to represent and force the ambient of the nested models. This was a complex process of harvesting
state variable outputs from the larger model and manipulating them into inputs for the nested model.
I Larger Grid
Nested Grid
/V RF3 Streams
Figure 3-11. Larger and Nested Grids
TIFTRATECH
3-9

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
3.4.1 EFDC
The EFDC model drives the hydrodynamics of the simulation. It is a critical component in representing
the ambient condition for the dilution analysis as well as driving the water quality analysis. The
simulation output passed from the larger model to the nested model included flow, water temperature, and
salinity. Other primary forcings such as wind were applied to the nested model the same as to the larger
model. Rain and evaporation were turned off in the nested model in order to achieve water balance, in
combination with use of an assimilation routine. The approximate contributions of rain and evaporation
are assumed equal and opposite, furthermore, they are small components relative to the overall water
budget for the system due to the substantial drainage area to the NRE. All remaining input coding and
forcings from the larger model were applied to the nested model.
Figure 3-12 presents the nested grid with the descriptors West, North, and East to generally identify each
of the three open boundaries. The figure also presents highlighted perimeter cells around the nested grid,
these are referred to as ghost cells. The ghost cells were used to pass the forcing information from the
larger model to the nested model. The flow output from the larger model was developed on an hourly
basis and by layer. On the west side and east side, the respective larger model grid cell output was
divided by six horizontal cells in the nested model per layer and assigned as input. The proper
inflow/outflow sign was conveyed to the nested model. The north side open boundary required that the
larger model grid cell output be divided by 10 per layer and assigned to the nested model. The same
approach was applied for the passing of the water temperature and salinity output from the larger model
to the nested model.
Figure 3-12. Ghost Cells for Input to Nested Model from Larger Model
TIIITRATIliCH
3-10
1

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The representation of the nested model simulation compared to the larger model was important as the
ambient simulation is a significant component of the mixing analysis. Furthermore, the hydrodynamics
of the nested model drive the water quality simulation in the WASP72 model.
The depth comparison was very similar for the summer critical period (Figure 3-13). Salinity
comparisons for the summer critical period were very good, with infrequent variations around 1 PSU
(Figure 3-14 and Figure 3-15). Water temperature comparisons for the summer critical period were
generally good with limited variation around 1 degree Celsius (Figure 3-16 and Figure 3-17). The
velocity comparisons presented more differences, but the simulation was still reasonable (Figure 3-18 and
Figure 3-19). The literature (Reed et al., 2004, AH, 2002) indicate low velocities around of 0.33 feet per
second (10 cm/s) and lower. Those magnitudes were present in both the larger and nested model.
Depth (m)
4.2
3.0
Jill 04 Jul 18 Aug 01 Aug 15 Aug 29
July 2002 - August 2002
Larger Grid
Nested Grid
Figure 3-13. Summer Critical Period, Depth Simulation Comparison of Larger (52,13) to
Nested (24, 31)
(IL)
„UTRA,h,
3-11

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
Surface Salt (PSU)
2a
22
Jul04
Jul 18
Aug 01
July 2002 - August 2002
Aug 15
Aug 29
Larger Gild
Nested Grid
Figure 3-14. Summer Critical Period, Surface Salinity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
Bottom Salt (PSU)
24
22
20
18
10
14
12
10
Jul 04 Jul 18 Aug 01 Aug 15 Ang 29
July 2002 - August 2002
Larger Gild
Nested Gild
Figure 3-15. Summer Critical Period, Bottom Salinity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
aTIFTRATICH
3-12

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Surface Water Temperature (degC)
32
30
26
24
12
J
J81 04 Jal 18 Aug 01 Aug 15 Aug 29
Juy 2002 - August 2002
I I._•.I...I.II
Figure 3-16. Summer Critical Period, Surface Water Temperature Simulation Comparison of
Larger (52,13) to Nested (24, 31)
Bottom Water Temperature (degC)
32 •
28 --
26• ....
24
16
11
12
i
•
•
Jul 01 Jul 18 Aug 01 Aug 15 Aug 29
July 2002 - August 2002
Laigei aid
Nested Gild
Figure 3-17. Summer Critical Period, Bottom Water Temperature Simulation Comparison of
Larger (52,13) to Nested (24, 31)
NE)
TIPTRAT
3-13

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Surface U Velocity (cm/s)
Lugo Glid
Nested Glid
Figure 3-18. Summer Critical Period, Surface U Velocity Simulation Comparison of Larger (52,13)
to Nested (24, 31)
Bottom U Velocity (cmfs)
30
20-
10
-10 ---
-20
1.
July 2002 - August 2002
Aug 29
— Latgei Gli i
Nested Gild
Figure 3-19. Summer Critical Period, Bottom U Velocity Simulation Comparison of Larger (52,13)
to Nested (24, 31)
t: �J r.ntw,tai
3-14

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
The comparisons of the same parameters for the winter critical period were favorable. Depth again
provided the best comparisons (Figure 3-20). Salinity and water temperature comparisons presented
limited divergence (Figure 3-21 through Figure 3-24). The velocity comparisons (Figure 3-25 and Figure
3-26) showed some minor differences.
Depth (m)
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4 -
3.2 -
3.0
1
I
M1
J J
1
1
.
1
i
1
"
•
.
Nov 01 Nov 08 Nov 15 Hov 22 Nov 29
July 2002 - August 2002
Larger Geld
Nested Geld
Figure 3-20. Winter Critical Period, Depth Simulation Comparison of Larger (52,13) to Nested
(24, 31)
Surface Salt (PSU)
24
22-
a.
20-
18
16-
14-
12-
10 "t `..'ti
8
6
4
ter' Y
1
Nov 01
1
1
1
i
i
Nov 08 Nov 15 Nov 22 Nov 29
July 2002 - August 2002
Larger Geld
Nested Geld
Figure 3-21. Winter Critical Period, Surface Salinity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
c] ITTRATI101
3-15
Figure 3-25. Winter Critical Period, Surface U Velocity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
ID=MAUCH
3-17

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Bottom Water Temperature (deg C)
24
22—
20
18—
16
•
10
8
6
4
Nov 01 Nov 08 Nov 15 Nov 22 Nov 29
November 2001
Luger Grid
Nested GuI
Figure 3-24. Winter Critical Period, Bottom Water Temperature Simulation Comparison of Larger
(52,13) to Nested (24, 31)
Figure 3-25. Winter Critical Period, Surface U Velocity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
TirTRATICH
3-17

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Bottom U Velocity (cm/s)
20
October 20(11- December 2001'
La,gei Grid
Nested Grid
Figure 3-26. Winter Critical Period, Bottom U Velocity Simulation Comparison of Larger (52,13) to
Nested (24, 31)
3.4.2 WASP72
The nested WASP72 simulation was compared to the larger model selectively. The primary response
variables of interest were reviewed to assess reasonability of the nested simulation compared to the larger
model. The dissolved oxygen comparisons (Figure 3-27 and Figure 3-28) were generally close. The
chlorophyll -a comparisons (Figure 3-29 and Figure 3-30) presented a slight oversimulation tendency in
the nested model, but the magnitude of the difference was small, about 2 µg/L or less.
NTTTRATICH
3-18

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
Rested (Lj.k) • (24.31.01) vs Larger (i.j,k)— ;52.13.04)
DO (mglL)
15
13
12
11
10
r r
9 I. a
Jul 04
Jul 18 Aug 01
July 2002 - August 2002
Aug 29
Larger Grid
Nested Grid
Figure 3-27. Summer Critical Period, Surface Dissolved Oxygen Simulation Comparison of Larger
(52,13) to Nested (24, 31)
DO (mgn.)
15
14
13
12
11
10
9
Nested (i.j.k) • (24,31,01) vs Larger (i,j.k) — (52.13.04)
ti
8—
7=
6=
5=
4
Nov 01
ti
Nov 08
Nov 15 Nov 22 Nov 29
November 2001
Larger Gild
Nested Grid
Figure 3-28. Winter Critical Period, Surface Dissolved Oxygen Simulation Comparison of Larger
(52,13) to Nested (24, 31)
® ITTRAtsRie
3-19

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Chia (uglL)
10
30
20
10
0
Nested (I.J.k) - (24.31.04) vs Larger (Ij.k) - (52.13.04)
a;.
.��:--- --
Jul 04
Jul 18 Aug 01 Aug 15 Aug 29
July 2002 - August 2002
Larger Grid
Nested Gtid
Figure 3-29. Summer Critical Period, Surface Chlorophyll -a Simulation Comparison of Larger
(52,13) to Nested (24, 31)
Chia (ugfL)
40
30
20
10
0
Rested 04.4 - {24.31.04) vs Larger (I.J.k) - (52.13.04)
Nov01 Nov08
Nov 15 Nov 22 Nov 29
November 2001
Larger Grid
Nested Gild
Figure 3-30. Winter Critical Period, Surface Chlorophyll -a Simulation Comparison of Larger
(52,13) to Nested (24, 31)
TIITRATKi1
3-20

elet
edEN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
3.5 HAVELOCK WWTP
esia The Havelock outfall is currently located in Slocum Creek (Figure 1-3). The current permit is
summarized in Table 3-3. The Havelock discharge is cited as the cause of oxygen and algal impacts in
Slocum Creek. Havelock is proposing to relocate their outfall to the NRE as a submerged multi -port
diffuser outfall. Furthermore Havelock is planning three phases of expansion in consideration of
anticipated growth and service needs.
eseN
Table 3-3. Current Permit for the City of Havelock WWTP (NPDES Number NC0021253)
OWN
Parameter
Summer-
. Winter
Flow (mgd)
1.9
1.9
Dissolved Oxygen (mg/L)
5.0
5.0
Biochemical Oxygen Demand (mg/L)
5.0
10.0
Ammonia (mgN/L)
0.5
1.0
Total Phosphorus (mgP/L) (quarterly average)
0.7
1.0
Total Nitrogen (IbN/year)
21,400
(AWN There were three proposed phases explored in this study along with the relocation of the outfall to the
NRE. They are summarized in Table 3-4. The information is presented in traditional English units as
eleN
well as those required by WASP72 (metric). They were developed by a process specialist exercising best
judgment along with assuming that certain current permit limits (DO, BOD5, and NH3) will be
maintained during the three expansion phases. This was considered a conservative approach, anticipated
`' to be more stressful than the regular operating effluent values. The nitrogen species assignments respect
eltN the current permit limit of 21,400 pounds per year.
The total phosphorus input for Havelock was assumed to be all orthophosphate in the model. This was
another layer of conservative assumption as orthophosphate is the inorganic form which is available for
elgt
phytoplankton reactions. The existing load from Havelock WWTP based on the current permit is 4,766
lb/year (2,161 kg/y). This loading was not exceeded in any of the three Phases.
An f-ratio of 2.5 was used for Havelock to convert effluent BOD5 values to CBODu values based on
Thomann and Mueller (1987). A long-term BOD study was performed on one sample of Havelock
effluent in 1988. However, it was decided to use literature values to estimate the f-ratio since the testing
occurred 20-years ago and it was only one sample.
PAtN
tigN
elwitN
3-21

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 3-4. Proposed Phases of the Havelock WWTP Discharge
Phase 1
Phase 2
Phase 3
Parameter
Summer
Winter
Summer
Winter
Summer
Winter
Flow (mgd)
2.25
2,25
2.8
2.8
3.5
3.5
Dissolved Oxygen (mg/L)
5.0
5.0
5.0
5.0
5.0
5.0
Biochemical Oxygen Demand (mg/L)
5.0
10.0
5.0
10.0
5.0
10.0
Ammonia (mgN/L)
0.5
1.0
0.5
1.0
0.5
1.0
Nitrate (mgN/L)
1.9
2.0
1.2
1.6
0.7
1.1
Organic N (mgN/L)
0.6
0.2
0.6
0.2
0.6
0.2
Total Nitrogen (mgN/L)
3.0
3.2
2.3
2.8
1.8
2.3
Total Nitrogen (IbN/d)
56.3
60.0
53.7
65.4
52.5
67.1
Total Phosphorus (mgP/L)
0.59
0.84
0.48
0.68
0.38
0.54
Parameters Below Revised for WASP72 Metric Units
CBODu1(kg/d) (f-ratio = 2.5)
106.5
212.9
132.5
265.0
165.6
331.2
Ammonia (kgN/d)
4.3
8.5
5.3
10.6
6.6
13.2
Nitrate (kgN/d)
16.2
17.0
12.7
17.0
9.3
14.6
Organic N (kgN/d)
5.1
1.7
6.4
2.1
7.9
2.6
PO4 = Total Phosphorus (kgP/d)
5.0
7.2
5.1
7.2
5.0
7.2
3.6 EXISTING MCAS CP PERMIT CONDITIONS
The MCAS CP discharge was represented by the current permit for the state variables available in the
model (flow, DO, BOD, NH3, and TP). The NO3 and OrgN values were estimated by reviewing limited
available data. Data for MCAS Cherry Point (MCAS CP) were retrieved from the Permit Compliance
System (PCS) to help determine model effluent forcings. Current performance values for MCAS CP
were calculated from monthly data from December 2004 through March 2007. Review of the facility's
record indicates that improvement from added technological treatment was evident by December 2004,
thus monitoring data following that date were selected as the most representative of current performance.
Data were split into two periods to reflect the seasonal permit requirements, summer (April through
October) and winter (November through March). The data as bounded by the periods noted were
evaluated as averages for the respective summer and winter periods.
The model application was developed with the monthly average permit limits used to define forcings for
the MCAS CP discharge. This is straightforward from the permit limit information provided in Table 3-5
for flow and BOD5. However, nitrogen and phosphorus forcings are not completely determined from the
permit limits. While there are limits for TN load and TP concentration, there are not limits for the species
breakdown for nitrogen and phosphorus needed in the model. The following approach was generally
followed for determining the fractioning of nitrogen:
• The summer and winter periods were each evaluated.
• The existing ammonia limits were assumed unchanged.
TIFTI%ATICH
3-22

raRN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
• The TN concentration value for each summer and winter was determined from the maximum
permitted monthly average flow and waste load allocation for nitrogen.
44)
• The DMR data was used to assess the performance of the plant. The summer average of
ammonia was subtracted from the summer average of TKN to estimate organic N, and likewise
for winter.
eatN
eats
• The MCAS CP DMR data was used to evaluate the summer and winter average of nitrate (NO3).
• The performance values of ammonia (NH3), Org N and NO3 were used to develop percentages
for Org N and NO3 to fit with the prescribed values of ammonia and TN as noted above.
There is a waste load allocation for total nitrogen of 39,421 lb/y or 108 lb/d. Using 3.5 mgd as the
discharge rate and the waste load allocation of 108 lb/d, the corresponding TN-N concentration is 3.7
mgN/L. However, there were two seasons to consider and the ammonia permit limits are 2 and 4 mgN/L
for the summer and winter periods. Holding the ammonia permit limits as the priority, the summer and
EAN winter daily loading values were manually adjusted until a balance was reached that resulted in the yearly
total nitrogen load being below the permit value. The determination of the summer and winter TN
concentration was performed by using April through October (214 days) for summer and November
eseN through March (151 days) for winter, as defined in the NPDES permit.
For the summer period, the average ammonia value was subtracted from the average TKN value (1.49 -
1.10 mgN/L) to estimate an organic N value of 0.39 mgN/L. The average summer NO3 value was 2.51
mgN/L. Therefore, of the remaining nitrogen after the summer average of 1.10 mgN/L for ammonia, 13
percent was organic nitrogen and 87 percent was nitrate.
For the winter period, the average ammonia value was subtracted from the average TKN value (0.97 —
0.54) to estimate an organic N value of 0.43 mgN/L. The average winter NO3 value was 2.43 mgN/L.
Therefore, of the remaining nitrogen after the summer average of 0.54 mgN/L for ammonia, 15 percent
efit was organic nitrogen and 85 percent was nitrate. Since the results of the analyses for summer and winter
periods were similar, for the model application 14 percent of the remaining nitrogen after the permit limit
ARN
assignment of ammonia will be applied to organic nitrogen and the remaining 86 percent will be applied
to nitrate. Table 3-6 presents the values used in the model application.
Based on the current permit limits, the loading from MCAS CP of total phosphorus is 21,309 lb/year.
The total phosphorus value was input to the model as all orthophosphate. This is considered a
`at\ conservative assumption.
An f-ratio of 2.5 was used for MCAS CP to convert effluent BODS values to CBODu values based on
__ Thomann and Mueller (1987).
1
eft\
Amit‘
�1
ARN
OVN
Table 3-5. Current Permit for MCAS CP WWTP (NPDES Number NC0003816)
Parameter
Summer
Winter
Flow (mgd)
3.5
3.5
Dissolved Oxygen (mg/L)
6.0
6.0
Biochemical Oxygen Demand (mg/L)
5.0
10.0
Ammonia (mgN/L)
2.0
4.0
Total Phosphorus (mgP/L) (quarterly average)
2.0
Total Nitrogen (IbN/year)
39,421
rmanai
3-23

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 3-6. MCAS CP WWTP Model Input
Parameter
Summer
'Winter
Flow (mgd)
3.5
3.5
Dissolved Oxygen (mg/L)
6.0
6.0
Biochemical Oxygen Demand (mg/L)
5.0
10.0
Ammonia (mgN/L)
2.0
4.0
Nitrate (mgN/L)
0.86 * (2.85 - 2.0) =0.73
0.86 * (4.85
- 4.0)
=0.73
Organic N (mgN/L)
0.14 * (2.85 - 2.0) =0.12
0.14 * (4.85
- 4.0)
=0.12
Total Nitrogen (mgN/L)
2.85
4.85
Total Nitrogen (IbN/d)
83.2
141.6
Total Phosphorus (mgP/L)
2.0
2.0
Parameters Below Revised for WASP72 Metric Units
CBODu1(kg/d) (f-ratio = 2.5)
165.6
331.2
Ammonia (kgN/d)
26.5
53.0
Nitrate (kgN/d)
9.7
9.7
Organic N (kgN/d)
1.6
1.6
PO4 = Total Phosphorus (kgP/d)
26.5
26.5
3.7 NESTED MODEL APPLICATION
The nested model was constructed to provide finer grid resolution to investigate the study objectives. It
was forced with output from the larger NRE model, the larger model was calibrated to observed data.
The nested model output was compared to the larger model output to confirm reasonability in the
representation of the ambient. Going forward, the nested model output will be compared relatively
against various scenarios in order to investigate dissolved oxygen and chlorophyll -a response differences.
E.] umwriai
3-24
z
f1.'
r'^

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
4 Dilution Analysis
North Carolina Division of Water Quality (DWQ) policy is to require dischargers to protect against acute
water quality impacts in the effluent at the end -of -pipe. Therefore, this dilution analysis is concerned
with chronic dilution which is evaluated based on a 4-day average concentration. The term dilution in
this report only refers to chronic dilution. There were two areas of investigation; 1) the proposed
Havelock dilution and 2) the interaction of the MCAS CP and Havelock effluent plumes.
4.1 JPEFDC SUBROUTINE
Environmental Fluid Dynamics Code (EFDC) is a state of -the -art hydrodynamic model that can be used
to simulate aquatic systems in one, two, and three dimensions. It has evolved over the past two decades
to become one of the most widely used and technically defensible hydrodynamic models. EFDC uses
stretched or sigma vertical coordinates and Cartesian or curvilinear, orthogonal horizontal coordinates to
represent the physical characteristics of a waterbody. It solves three-dimensional, vertically hydrostatic,
free surface, turbulent averaged equations of motion for a variable -density fluid. Dynamically -coupled
transport equations for turbulent kinetic energy, turbulent length scale, salinity and temperature are also
solved. The physics of the EFDC model and many aspects of the computational scheme are equivalent to
the widely used Blumberg -Mellor model and U.S. Army Corps of Engineers' Chesapeake Bay model.
In addition to the farfield transport and fate simulation capability incorporated into EFDC's water quality
and toxic contaminant modules, the code includes a nearfield discharge dilution and mixing zone module.
The nearfield model is based on a Lagrangian buoyant jet and plume model (Frick, 1984; Lee and
Cheung, 1990) and allows representation of submerged single and multiple port diffusers and buoyant
surface jets. The nearfield model provides analysis capabilities similar to CORMIX (Jirka and Doneker,
1991; Jirka and Akar, 1991) while offering two distinct advantages. The first advantage is that a more
realistic representation of ambient current and stratification conditions, provided directly by EFDC
hydrodynamic module, is incorporated into the analysis. The second advantage is that multiple
discharges and multiple nearfield analysis times may be specified to account for varying ambient current
and stratification conditions. For example, the analysis of 10 discharges under 6 ambient conditions each
would require 60 executions of CORMIX, while the entire analysis of the 60 situations would be
produced in a single EFDC simulation. The nearfield simulation may be executed in two modes, the first
providing virtual source information for representing the discharges in a standard EFDC farfield transport
and fate simulation. The second mode directly couples the near field and far field transport modes, again
using a virtual source formulation, during simultaneous near and farfield transport and fate simulations
(Hamrick, 1996).
4.2 CONFIGURATION
A meeting was held on August 14, 2007 to discuss the proposed relocation and expansion of the
Havelock discharge. The attendees included NCDWQ, City of Havelock, Hazen & Sawyer, and Tetra
Tech. The general discussion regarding the proposed outfall configuration for Havelock was to look at
what NCDWQ has already approved and is constructed. Therefore, since MCAS CP is permitted at 3.5
mgd (0.1533 cms) and the proposed Phase 3 flow for Havelock is 3.5 mgd (0.1533 cms), the outfall
configuration for MCAS CP was used in the model for Havelock A brief description of that outfall is 8
ports spaced at 10 feet (3 m) each, for a diffuser length of 70 feet (21.3 m). The ports will have a 0.5 foot
(0.15 m) diameter and be angled 30 degrees upward from a horizontal plane, they will all face the same
direction. The direction of the discharge from the ports will be generally seaward. The port exit velocity
was calculated as feet per second (70 cm/s). The host cell (i=27, j=29) of the jet -plume has a bottom
nrITRATIIICH
4-1

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
elevation of —12.8 feet (-3.9 m). The centerline elevation of the ports was set at —9.8 feet (-3.0 m). The
distance from the centerline of the jet to the bed is represented as 0.9 feet (0.3 m).
The effluent from each Havelock and MCAS CP was assigned a concentration of 100 percent. There was
no consideration for decay, transformation, or any other process. This is typical for most mixing analysis
work and considered conservative.
4.3 LENGTH SCALES
When considering jet -plumes, there are three primary constituents. They are volumetric flux (Q),
momentum flux (M), and buoyancy flux (B). These three constituents are used in a variety of ways to
help characterize the jet -plume (Fischer et al., 1979). In summary, a jet -plume is jet -like when
momentum is dominant and plume -like when buoyancy is dominant. The current application is a
discharge that is parallel to the general seaward direction of the waterbody, however the actual
direction(s) of the ambient (receiving water) is very complex.
The discharge from the proposed outfall into the NRE is a buoyant jet, freshwater waste stream is being
discharged to a saline ambient. Length scale (Jirka et al., 1996) calculations were performed to gain
insight on anticipated behavior of the jet -plume (Table 4-1). This exercise reveals that the jet -like
characteristics will be terminated in a very short distance from the discharge.
Table 4-1. Representative Length Scales for WWTP Effluent and Ambient Characteristics
(Jirka, 1996)
Length
Scale
Description
Ambient Velocity =
fps (30 cmis)
Ambient Velocity =
fps (5 cmis)
LM
(meters)
For combined buoyant jet, transition from jet -like to
plume -like when ambient velocity = 0.0.
0.7
Not Applicable
Lm
(meters)
Length of region beyond which the flow is simply
advected.
0.04
1.3
4.4 MODEL INTERPRETATION
The State of North Carolina requires that chronic mixing zones be determined on a case by case basis
(15A NCAC 2B.0204). North Carolina Division of Water Quality (DWQ) policy is to require dischargers
to protect against acute water quality impacts in the effluent at the end -of -pipe. Therefore, this dilution
analysis is concerned with chronic dilution which is evaluated based on a 4-day average concentration. In
previous conversation with the DWQ NPDES permitting staff (personal communication, Teresa
Rodriguez, DWQ NPDES, July 2007), one rule of thumb that has been applied is for the chronic mixing
zone not to exceed one-third of the width of the receiving water, which would be about 1,733 meters for
this study area. Because application of this rule -of -thumb produces an unrealistically large mixing zone
range, Tetra Tech evaluated dilution at discrete radial distances closer to the proposed outfall.
The use of the EFDC and WASP models has many advantages for the project as a whole. Among them
are a robust embedded nearfield model coupled to the farfield. The Phase 3 scenario was investigated
first because it was likely to be potentially the most stressful scenario. Thus if its impacts were small it
was likely that the impacts of Phases 1 and 2 would be small. The general approach for interpretation of
the dilution simulation follows:
1. Process the nearfield simulation output into chronic (4-day moving average) values for the
termination of the nearfield (CrrF)• (i
nTITRATIICH
4-2
P,
oft
eft
l
ANA
ANN
AN.
ANA

eariN
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ellaN
Aks
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
2. Evaluate these nearfield chronic effluent plume concentration values for 90th percentile, average,
and loth percentile.
3. Process the farfield simulation output into chronic values. The outfall horizontal location (27, 29)
rozN was evaluated for chronic values with each of the four horizontal locations touching its faces,
always using layer 3 and 4. Of these four analyses, the coupling with the highest 90th percentile,
average, and l Oth percentile was adopted to represent the farfield condition (CFF).
4. Calculate the radius of an equivalent area circle for the host cell of the outfall (RFF).
5. Use Equation 1 and Equation 2 to estimate the effluent plume concentrations at 10, 25, 50, and 75
meters from the outfall.
eves
Asks
6. Present results as effluent plume concentration and dilution.
The following equation was used.
—a(R—p )2 Equation 1
C=CNF•e
Where: C = effluent plume concentration at radius R
CNF = chronic nearfield effluent plume concentration
a = unique constant per current statistic
R = radius being evaluated (i.e., 10, 25, 50, and 75 m)
efts
R s radius of the nearfield
ees
elks
elks
elbs
elks
efflts
When the nearfield and farfield endpoints are determined for each statistic being evaluated, the
calculation of the constant alpha follows.
ln(CFF / CNF!
a=-
( R _R FF NF!l2
Equation 2
4.5 PHASE 3 DILUTION RESULTS
The summer and winter periods were each evaluated for three statistics; 90th percentile, average, and 10th
percentile. The statistics were applied to the effluent plume concentration. The 90th percentile applied to
effluent plume concentration results in the least dilution. Furthermore, the Phase 3 flow of 3.5 mgd
(0.1533 cms) was considered as the most critical for Havelock WWTP to represent the highest potential
instream concentration. MCAS CP WWTP discharge was represented at its permit value of 3.5 mgd
(0.1533 cms).
4.5.1 Summer
The summer values are presented in Table 4-2. Figure 4-1 and Figure 4-2 present this information in
graphical format. The difference in dilution based on the average concentration after the termination of
the nearfield simulation through a radius of 25 meters is small, ranging from approximately 7 to 9. After
the radius of 25 meters, the dilution increases significantly, more than doubling by a radius of 50 meters
ARN and greater continuing away from the outfall.
4-3

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 4-2. Summer Effluent Plume Concentration Statistics and Related Dilution, Phase 3
90th Percentile
Average
10th Percentile
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter) i
Concentration
(percent)
Dilution
RNF = 1.8
16.3
6
RNF = 1.6
14.7
7
RNF = 1.3
13.3
8
10
15.9
6
10
14.3
7
10
12.9
8
25
13.2
8
25
11.7
9
25
10.3
10
50
6.48
15
50
5.40
19
50
4.58
22
75
1.95
51
75
1.46
68
75
1.15
87
REF = 85
1.05
96
RFF = 85
0.75
134
RFF = 85
0.56
177
Concentration (Percent(
100 -- -
90 - -
70--
80 - -
50--
40
30
20
10
0
Summer
r
r
T 1
1
L
J
J
L 1
J
J
J L
0
20 30 40 50 60
Radius from Dischorge (m)
—901h Percentile —Average —10th Percentile
70 80 90 100
Figure 4-1. Summer Effluent Plume Concentration, Phase 3
m11AT CH
4-4

leek
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
1e0
160 -
I
140
120 —
100- -
3
a 80.
60
40
20-
0
Summer
L L
L
I I
1
I I
.1
r
10 20 30 40 50 60
Radius from Discharge (m(
—90th Percentile —Average —10th Percentile
70 60 g0 700
Figure 4-2. Summer Dilution, Phase 3
4.5.2 Winter
The winter values are presented in Table 4-3. Figure 4-3 and Figure 4-4 present this information in
graphical format. The simulation output based on the average effluent plume concentration is similar to
the summer results from the termination of the outfall to a radius of 25 meters. Continuing outward,
based on average effluent plume concentrations, the dilution increases significantly, although slightly less
than the summer condition. However, the magnitude of the dilution for each, 19 and greater for summer
and 17 and greater for winter, indicates that a similar robust level of dilution is achieved past a radius of
25 meters.
Table 4-3. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 3
ellek
Oft
tisk
90th Percentile
Average
10th Percentile
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
RNF = 1.8
16.8
6
RNF = 1.7
15.0
7
RNF = 1.5
13.8
7
10
16.4
6
10
14.6
7
10
13.4
7
25
13.7
7
25
12.1
8
25
10.8
9
50
7.06
14
50
5.98
17
50
4.88
20
75
2.28
44
75
1.80
56
75
1.27
79
RFF = 85
1.27
79
RFF = 85
0.97
103
RFF = 85
0.63
158
4-5

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
100
90
80
70
Winter
T
i 60--
Y
a
50 —
11
40
U
30
20 —
10
0
L
J
1 J J
r r t
10 20 30 40 50 60
Raffles from Discharge (m)
—90th Percentile —Average — 10th Percentile
70 80 90 100
Figure 4-3. Winter Effluent Plume Concentration, Phase 3
180
160
140
120
80
40-
0
Winter
r r
r r T
L
J
_1
-1
J
10 20 30 40 50 60
Recline from Discharge (m)
—90th Percentile —Average —10th Percentile I
70 80 90 100
Figure 4-4. Winter Dilution, Phase 3
4.6 PHASE 1 AND 2 DILUTION RESULTS
Phase 1 and 2 effluent plume concentration and dilution results are presented in tabular form only because
they each provide more dilution then the Phase 3 scenario. The statistics were generated on the effluent
plume concentration. then the dilution was calculated.
n
4-6

elaN
esik
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
4.6.1 Summer
The average dilutions presented in Table 4-4 and Table 4-5 do not differ substantially from the summer
Phase 3 scenario from the outfall to a radius of 25 meters. After a radius of 25 meters, both the average
dilution of Phase 1 and Phase 2 become much greater than Phase 3, however noting that the average
dilution in Phase 3 was over 100 before a radius of 85 meters.
Table 4-4. Summer Effluent Plume Concentration Statistics and Related Dilution, Phase 1
90th Percentile .
Average:.
10th Percentile
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration -
(percent)
.
Dilution
Radius
(meter)
Concentration.
(percent)
Dilution
RNF = 1.6
14.6
7
RNF = 1.4
12.3
8
RNF = 1.1
9.77
10
10
14.1
7
10
11.8
8
10
9.43
11
25
11.4
9
25
9.46
11
25
7.51
13
50
5.02
20
50
4.10
24
50
3.23
31
75
1.25
80
75
1.00
100
75
0.78
128
RFF = 85
0.61
164
RFF = 85
0.48
209
RFF = 85
0.37
268
Table 4-5. Summer Effluent Plume Concentration Statistics and Related Dilution, Phase 2
90th Percentile
Average _
10th Percentile
Radius
(meter)
Concentration
(percent)
Dilution
•Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
RNF = 1.7
15.6
6
RNF =1.5
13.5
7
RNF =1.3
11.7
9
10
15.1
7
10
13.1
8
10
11.3
9
25
12.3
8
25
10.5
10
25
9.00
11
50
5.61
18
50
4.64
22
50
3.87
26
75
1.48
68
75
1.16
86
75
0.93
108
RFF = 85
0.74
135
RFF = 85
0.57
176
RFF = 85
0.44
225
4.6.2 Winter
Table 4-6 and Table 4-7 present the effluent plume concentration and corresponding dilution for the
winter critical period, Phase 1 and Phase 2 respectively. The average dilution results are similar to the
summer critical period. There is a small difference in dilution from the outfall to a radius of 25 meters for
all three phases. However, outside a radius of 25 meters the dilution increases substantially, again all
three phases achieve at least a dilution of 100 before a radius of 85 meters.
4-7

emN
SQL'. Percentile
Average
'it
10, Percentile
Radius
(meter)
Concentration
(percent)
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
Radius
.(meter.)
`Concentration
(percent)
Dilution
RNF=1.7
14.3
7
RNF=1.5
11.9
8
RNF=1.4
10.2
10
10
13.9
7
10
11.6
9
10
9.85
10
25
11.6
9
25
9.62
10
25
8.09
12
50
5.86
17
50
4.77
21
50
3.88
26
75
1.84
54
7.5
1.45
69
75
1.12
90
RFF = 85
1.01
99
RFF = 85
0.79
127
RFF = 85
0.59
170
Table 4-7. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 2
90th Percentile :
Average
10"' Percentile
Radius
(meter)
' Concentration
(percent)
Dilution
Radius
(meter).
Concentration
.- (percent)
. .
Dilution
Radius
(meter)
Concentration
(percent)
Dilution
RNF=1.8
15.9
6
RNF=1.6
13.6
7
RNF = 1.5
12.1
8
10
15.5
6
10
13.2
8
10
11.7
9
25
13.0
8
25
11.0
9
25
9.59
10
50
6.57
15
50
5.44
18
50
4.55
22
75
2.07
48
75
1.66
60
75
1.29
78
RFF = 85
1.14
88
RFF = 85
0.90
111
RFF = 85
0.67
149
4.7 PHASE 3 EFFLUENT PLUME INTERACTION
The proposed Havelock WWTP outfall was coded at approximately 850 meters east of the existing
MCAS CP WWTP outfall. The effluent plume interaction was evaluated by executing two simulations
for each of the critical periods. The first simulation was with Havelock WWTP discharge only and the
other was with each MCAS CP WWTP and Havelock WWTP discharge (combined). Furthermore,
Havelock WWTP was evaluated at Phase 3 flow only (3.5 mgd, 0.1533 cms) to represent the highest
potential concentration. The outputs from these simulations were processed similar to what was
described previously for the farfield concentration. That is the output was processed into chronic effluent
plume concentration by averaging layer 3 and 4 of cell (27, 29), the cell that holds the Havelock WWTP
outfall and cell (26, 29). Then these two simulations were summarized and presented in Table 4-8 and
Table 4-9.
4-8
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 4-6. Winter Effluent Plume Concentration Statistics and Related Dilution, Phase 1 ems
ems
rims
ems
ems
emN
ems
ems
ems
lam`
ems
raiN
ems
ems
ems
r"

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Ars
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 4-8. Difference in Chronic Effluent Plume Concentration for Havelock WWTP Only versus
Combined, Summer
Concentration
Statistic
Havelock Only
Combined
Effluent Plume
Concentration (Percent)
Associated
Dilution
Effluent Plume
Concentration (Percent)
Associated
Dilution
90th Percentile
0.89
112.4
1.05
95.2
Average
0.66
151.5
0.75
133.3
10th Percentile
0.49
204.1
0.56
178.6
Table 4-9. Difference in Chronic Effluent Plume Concentration for Havelock WWTP Only versus
Combined, Winter
Concentration
Statistic
Havelock Only
Combined
Effluent Plume
Concentration (Percent)
Associated
Dilution
Effluent Plume
Concentration (Percent)
Associated
Dilution
90th Percentile
1.12
89.3
1.27
78.7
Average
0.83
120.5
0.97
103.1
10th Percentile
0.46
217.4
0.63
158.7
eireN
'm.\ The analysis indicates that on average, whether considering Havelock WWTP only or the combined
eltN effluent plume, the farfield dilution at the proposed Havelock WWTP outfall exceeds a ratio of 100:1.
elltN
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eADN
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eigt
AWN
4-9

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
5 Water Quality Analysis
The focus of the nested models was to compare the scenario without the proposed Havelock outfall (No
Havelock) to the three proposed expansion phases. The following sections summarize simulations for
each of the critical periods, comparing No Havelock to Phase 3 (largest proposed flow) permit scenario
first. Then the Phase 1 and Phase 2 results were reviewed against the No Havelock scenario.
Two critical periods were selected in anticipation of capturing appropriates low flo and higher water
temperature periods to consider the respective summer and winter proposedpe it limits for Havelock.
They were purposefully chosen on a monthly basis in anticipation of further temporal focus once the
detailed modeling began.
5.1 MODEL INTERPRETATION
The model output was reviewed at the location of the proposed Havelock outfall: cell (27, 29). The
simulation output were generated twice per day, thus the two values were averaged to produce a daily
simulation value. The output was further aggregated into surface and bottom output where surface is the
average of layer 3 and 4 while bottom is the average of layer 1 and 2. The variables reviewed were
dissolved oxygen and chlorophyll -a. The water quality standard for dissolved oxygen is not less than
5.0 mg/L (15A NCAC 02B.0220(3)(b)). The water quality standard for chlorophyll -a is 40 µg/L (15A
NCAC 02B.0220(3)(a)). The NRE was placed on the 303(d) list for chlorophyll -a.
5.2 SUMMER PHASE 3 DISSOLVED OXYGEN RESULTS
Figure 5-1 presents the time series of the DO simulations, comparing each surface and bottom output for
the No Havelock and Phase 3 scenarios. Generally, a typical DO stratification pattern is observed, that is
higher values on the surface and lower on the bottom. There are periods where the surface and bottom
values approach each other, likely due to mixing in the water column.
— No Havelock: Surface (Layer 3 & 4)
—No Havelock: Bottom (Layer 1 & 2)
— Phase 3: Surface (Layer 3 & 4)
— Phase 3: Bottom (Layer 1 & 2)
7/1/2002 7/8/2002 7/15/2002 7/22/2002 7/29/2002 8/5/2002 8/12/2002 8/19/2002 8/26/2002
Figure 5-1. Summer Simulated Dissolved Oxygen Values, No Havelock Versus Phase 3 Permit
Scenarios
5-1

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Figure 5-2 presents the daily wind speed and 7-day moving average of freshwater flow at the headwater
boundary near New Bern. There appears to be a relationship with the elevated wind speeds (up to 6 m/s
or 13.5 mi/h) between July 08 —15 and August 05 —12 and the resulting de -stratification of DO observed
in Figure 5-3. The monthly average wind speed for July was 3.5 m/s (7.9 mi/h) and for August it was 3.5
m/s (7.8 mi/h). Furthermore, the 7-day moving average of flow shows some increases near the periods of
de -stratification in DO. The combination of increased wind activity and increased freshwater flow affects
vertical mixing and reaeration. It is recognized that the study area is an estuarine environment and there
are complex interactions affecting mixing and DO levels. Wind and flow values were reviewed because
of their perceived larger impact on these phenomena, however it is noted that there is also tidal signal
impacts, salinity and water temperature distributions to consider.
Wind Speed (m/s)
7/1/2002 7/8/2002 7/15/2002 7/22/2002 7/29/2002
8/5/2002 8/12/2002 8/19/2002 8/28/2002
40
35
30
25
20
15
10
5
0
7-Day Average Flow (cros)
Figure 5-2. Summer Daily Wind Speed and 7-Day Moving Average of Headwater Flow
Figure 5-3 presents the time series of the differences in dissolved oxygen predictions by surface and
bottom for the No Havelock versus Phase 3 scenarios. Note that the figure presents the DO differences
without representation of the corresponding simulated magnitudes. Upon further review, it was observed
that the largest difference during the summer period was after August 05 which also corresponded to the
highest values of surface DO simulated, around 6.5 — 7.0 mg/L. Conversely, during the longest period of
low surface DO, approximately July 22 — 29, DO differences were approximately -0.1 mg/L or less.
5-2

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
ink
7/1/2002 7/8/2002 7/15/2002 7/22/2002 7/29/2002 8/5/2002 8/12/2002 8/19/2002 8/26/2002
Figure 5-3. Summer Simulated Dissolved Oxygen Difference, No Havelock Versus Phase 3
Permit Scenarios
r..
The DO standard was only approached during the critical summer. The largest differences in surface DO
oak
during the summer were observed when the values were above 5 mg/L, closer to 6 mg/L. None of the
r► simulated DO values for the Phase 3 permit scenario were less than 5 mg/L on the surface. The period of
July 22 — 29 had average wind conditions and limited flow changes, this period produced DO differences
typically less than -0.1 mg/L. The largest DO differences occurred when the magnitude of the DO values
�► was generally far enough above 5 mg/L to not warrant water quality standard violation concerns.
.�► Table 5-1 presents the differences between the No Havelock and Phase 3 scenarios for selected statistics.
The average difference at the surface was less than -0.1 mg/L. For comparison, the 10th percentile of
difference compared to the No Havelock scenario was -0.19 mg/L. The statistics were applied to the
•� differences of the scenarios. Thus the 10th percentile captures a negative number, which is interpreted as
the largest DO deficit created by the phase under review.
Sok
Table 5-1. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface and
Bottom, No Havelock Versus Phase 3 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and 2)
90th Percentile
0.01
0.06
Average
-0.08
-0.01
10th Percentile
-0.19
-0.08
5.3 WINTER PHASE 3 DISSOLVED OXYGEN RESULTS
The winter period had higher magnitudes of dissolved oxygen and less stratification (Figure 5-4). The
average monthly wind speed for November was 3.8 m/s (8.4 mi/h). It is noted that at times when the DO
.► stratification is small, the wind magnitude is above average (Figure 5-5), however the apparent correlation
is not as strong as in the summer. The time series of difference between the scenarios (Figure 5-6) is
,— 1*rwnno4
Airak
5-3

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
much more stable than the summer. This is likely due to the lack of any significant freshwater inflow
changes which were present in the summer.
11.0
11/1/2001
11/8/2001
4
—No Havelock: Surface (Layer 3 & 4)
—No Havelock: Bottom (Layer 1 & 2)
—Phase 3: Surface (Layer 3 & 4)
Phase 3: Bottom (Layer 1 & 2)
11/15/2001
11/22/2001
11/29/2001
Figure 5-4. Winter Simulated Dissolved Oxygen Values, No Havelock Versus Phase 3 Permit
Scenarios
Wind Speed (m/s)
7
6-
5
0
11/1/2001
— Daily Wind Speed (m/s)
- Neuse River at Fort Barnwell (02091814)
— 40
-- 35
— 10
—5
11 /8/2001 11/15/2001
11 /22/2001 11/29/2001
0
7-Day Average Flow (cros)
Figure 5-5. Winter Daily Wind Speed and 7-Day Moving Average of Headwater Flow
1„rATSCH
5-4

Oak
All
AIN
AMIN
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
1.0
0.8
0.6
^0.4 -
`of
0.2 -
0
0.0-
w
mU
-0.2
Q-0.4 -
-0.6
-0.8
-1.0
1-
L
r
— Surface (Layer 3 & 4)
— Bottom (Layer 1 & 2)
L
r
11 /1 /2001
11/8/2001 11/15/2001
11 /22/2001
11/29/2001
Figure 5-6. Winter Simulated Dissolved Oxygen Difference, No Havelock Versus Phase 3 Permit
Scenarios
Table 5-2 indicates that the average difference in the surface layer was less than -0.1 mg/L. For
comparison, the loth percentile of difference from the No Havelock scenario was -0.16 mg/L.
Table 5-2. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface and Bottom,
No Havelock Versus Phase 3 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and 2)
90th Percentile
-0.01
0.05
Average
-0.08
0.00
10t Percentile
-0.16
-0.05
5.4 SUMMER PHASE 3 CHLOROPHYLL -A RESULTS
", Figure 5-7 presents the time series of the summer simulation for the No Havelock and Phase 3 permit
scenarios. Generally the magnitudes are 10 — 12 µg/L through the summer period and declining. Figure
5-8 below presents the time series of the difference of the surface and bottom for the two scenarios. A
A� noteworthy observation is the surface difference around August 05 — 12; this was also the period with the
highest simulated DO and greatest DO difference. This short duration of difference is approximately
1 µg/L or less.
,AIR
Alas
AMA
TITAATDCH
5-5

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
Chlorophyll -a (pgIL)
18
16
14 — r
12 — -
10
8
6
7/1/2002 7/8/2002 7/15/2002 7/22/2002 7/29/2002 8/5/2002 8/12/2002 8/19/2002 8/26/2002
J
1
r
r--
J
— No Havelock: Surface (Layer 3 & 4)
— No Havelock: Bottom (Layer 1 & 2)
— Phase 3: Surface (Layer 3 & 4)
Phase 3: Bottom (Layer 1 & 2)
Figure 5-7. Summer Simulated Chlorophyll -a, No Havelock Versus Phase 3 Permit Scenarios
Difference in Chlorophyll -a (pg!L)
2.0 -
1.5
1.0 -
0.5
0.0
-0.5
-1.0
-1.5
-2.0
r
4
T
— Surface (Layer 3 & 4)
— Bottom (Layer 1 & 2)
7/1/2002 7/8/2002 7/15/2002 7/22/2002 7/29/2002 8/5/2002 8/12/2002 8/19/2002 8/26/2002
Figure 5-8. Summer Simulated Chlorophyll -a Difference, No Havelock Versus Phase 3 Permit
Scenarios
Table 5-3 presents a statistical summary of the difference of chlorophyll -a simulations for the No
Havelock versus Phase 3 permit scenarios, comparing average difference to the loth and 90th percentiles
to capture relative variability.
®T.T1MT.o4
5-6

AWN
ntaa
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 5-3. Statistics of the Difference of Chlorophyll -a (pg/L) Simulations for Surface and
Bottom, No Havelock Versus Phase 3 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and 2)
90th Percentile
0.55
0.20
Average
0.17
0.06
10th Percentile
-0.03
0.00
5.5 WINTER PHASE 3 CHLOROPHYLL -A RESULTS
The winter period is typically characterized by less productivity. Figure 5-9 below indicates such with a
downward trend in chlorophyll -a values. Figure 5-10 below indicates differences are generally less than
0.5 µg/L and Table 5-4 supports this interpretation.
Chlorophyll -a (pg!L)
18
16
14
12
10
8
6
11/1/2001
11/8/2001
11/15/2001
—No Havelock:Surface (Layer 38 4)
— No Havelock: Bottom (Layer 1 & 2)
— Phase 3: Surface (Layer 3 & 4)
- - --Phase 3: Bottom (Layer 1 8 2)
11/22/2001
11/29/2001
Figure 5-9. Winter Simulated Chlorophyll -a, No Havelock Versus Phase 3 Permit Scenarios
TTT ATICH
5-7

Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge
December 2008
2.0
1.5 -
`o▪ + 1.0
u -0.5 -
c
23.
-1.0
-1.5
-2.0
r
—Surface (Layer 3 & 4)
—Bottom (Layers 1 & 2)
11 /1 /2001
11/8/2001
11/15/2001
11/22/2001
11/29/2001
114
Figure 5-10. Winter Simulated Chlorophyll -a Difference, No Havelock Versus Phase 3 Permit
Scenarios
Table 5-4. Winter Statistics of the Difference of Chlorophyll -a (pg/L) Simulations for Surface
and Bottom, No Havelock Versus Phase 3 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and 2)
90th Percentile
0.27
0.29
Average
0.10
0.13
10th Percentile
-0.03
0.03
/^
et-
In each of the critical periods the simulated magnitudes of chlorophyll -a are less than half the value of the
water quality standard. The differences in each period are generally less than 1 mg/L.
5.6 SUMMER PHASE 1 AND 2 DISSOLVED OXYGEN RESULTS
The summer Phase 1 and 2 results for the dissolved oxygen simulation are presented in Table 5-5 and
Table 5-6. The average surface difference from the No Havelock scenario is small at -0.05 mg/L and less.
Table 5-5. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface and
Bottom, No Havelock Versus Phase 1 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and 2)
90th Percentile
0.03
0.06
Average
-0.02
-0.01
10th Percentile
-0.06
-0.06
5-8

elaN
reN
eAN
evAN
es k
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 5-6. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface and
Bottom, No Havelock Versus Phase 2 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1. and 2)
90th Percentile
0.02
0.05
Average
-0.05
-0.01
10th Percentile
-0.11
-0.06
5.7 WINTER PHASE 1 AND 2 DISSOLVED OXYGEN RESULTS
The winter Phase 1 and 2 results for the dissolved oxygen simulation are presented in Table 5-7 and Table
5-8. The average surface difference from the No Havelock scenario was small at -0.06 mg/L and less.
The statistics were applied to the differences of the scenarios, therefore the 10th percentile captures a
negative number, which is interpreted as the largest DO deficit created by the phase under review. All
three winter phases create DO differences around -0.10 mg/L.
Table 5-7. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface and Bottom,
No Havelock Versus Phase 1 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1. and 2)
90th Percentile
0.01
0.04
Average
-0.04
0.00
10th Percentile
-0.10
-0.05
Table 5-8. Winter Statistics of the Difference of DO (mg/L) Simulations for Surface and Bottom,
No Havelock Versus Phase 2 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1 and
90th Percentile
0.00
0.04
Average
-0.06
0.00
10th Percentile
-0.11
-0.03
5.8 SUMMER PHASE 1 AND 2 CHLOROPHYLL -A RESULTS
The summer Phase 1 and 2 results for the chlorophyll -a simulation are presented in Table 5-9 and Table
5-10. The average surface difference from the No Havelock scenario was small at 0.27 µg/L and less.
The chlorophyll -a values from Phase 1 and 2 are actually higher than Phase 3. This is likely due to the
higher NO3 load assigned to the Havelock effluent during Phase 1 and 2. Recall that the NO3
assignments were developed by using best judgment and obeying the anticipated ammonia concentration
r limit.
t
ejit
5-9
(41
Ops

•
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 5-9. Summer Statistics of the Difference of Chlorophyll -a (NgIL) Simulations for Surface
and Bottom, No Havelock Versus Phase 1 Permit Scenarios
Surface (Layer 3 and 4)
Bottom (Layer 1, and' 2)
90th Percentile
0.64
0.22
Average
0.27
0.10
10th Percentile
0.07
0.02
Table 5-10. Summer Statistics of the Difference of Chlorophyll -a (NgIL) Simulations for Surface �^
and Bottom, No Havelock Versus Phase 2 Permit Scenarios
Surface (Layer 3 and 4) .
; Bottom.(Layer 1 and 2)
90th Percentile
0.66
0.21
Average
0.22
0.08
10th Percentile
0.02
0.01
5.9 WINTER PHASE 1 AND 2 CHLOROPHYLL -A RESULTS
The winter Phase 1 and 2 results for the chlorophyll -a simulation are presented in Table 5-11 and Table 5-
12. As with the winter Phase 3 results, all the statistics on the chlorophyll -a differences were generally
less than 0.5 µg/L.
Table 5-11. Winter Statistics of the Difference of Chlorophyll -a (NgIL) Simulations for Surface
and Bottom, No Havelock Versus Phase 1 Permit Scenarios
Surface (Layer 3 and 4)
Bottom: (Layer 1 and 2)
90th Percentile
0.36
0.34
Average
0.13
0.14
10th Percentile
-0.01
0.03
Table 5-12. Winter Statistics of the Difference of Chlorophyll -a (NgIL) Simulations for Surface
and Bottom, No Havelock Versus Phase 2 Permit Scenarios ea+
eaN
Surface (Layer 3 and 4)
, Bottom (LayerI and 2)
90thPercentile
0.30
0.34
Average
0.11
0.14
10th Percentile
-0.03
0.03
eiN
5-10

i
Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
6 Water Quality Sensitivity Analysis
A sensitivity analysis was performed to assess the level of impact of the Havelock discharge to the NRE.
It is noted that the investigation of the three proposed phases can be considered as a form of sensitivity
analysis. This section presents the evaluation of different discharge characteristics for the proposed
Havelock outfall. Since this was a sensitivity analysis, some of the discharge characteristics were
assigned at levels that will not be permitted in order to gain information about system response and thus
insight to the proposed permit limits.
6.1 SENSITIVITY ANALYSIS SCENARIOS
The sensitivity analysis was conducted by using the summer proposed Phase 3 scenario as the beginning
condition, adopting the assumption that summer was the more critical period. Four scenarios were
developed to investigate sensitivity of the model, particularly the response variables of DO and
chlorophyll -a. These scenarios are presented in Table 6-1, the summer proposed Phase 3 scenario is
repeated as a reference. A brief description of the sensitivity scenarios is provided in the following
bullets:
• Scenario 1. The summer Phase 3 average performance is an estimate by a process specialist of
the Phase 3 operating performance level. This scenario allows consideration of a reasonable
representation of what the discharge may actually be like.
• Scenario 2. The winter permit limits for ammonia and BOD5 were adopted for the summer
critical period. This scenario is one of three scenarios which explore constituent (NH3 and
BOD5) values that likely will not be permitted for the summer critical period. However, they
were investigated for their value in assessing system response and potential impact of the
Havelock discharge.
• Scenario 3. The BOD5 Phase 3 permit value was multiplied by a factor of 10. This was
considered an order of magnitude investigation of a constituent which may have a primary impact
on the dissolved oxygen response variable.
• Scenario 4. The NH3 Phase 3 permit value was multiplied by a factor of 10. This was
considered an order of magnitude investigation of a constituent that may exert on both the
dissolved oxygen and chlorophyll -a response variables.
0 nrnwroci
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Fes'
Table 6-1. Sensitivity Analysis Scenarios
Parameter
Summer
Phase 3 '
Permit
Scenario 1:
"Summer Phase 3
Averages , '
Performance! ';
Scenario 2• Winter
Perr it Limitsr for
NHa,andtBODS
Applied ;toy=Sommer
' ' Scenario 3-:.
tlfiultiply ^
. tBOD5 10'.
Scenario 4
. .Multiply NH3
by'10
Flow (mgd)
3.5
2.8
3.5
3.5
3.5
Dissolved Oxygen
(mg/L)
5.0
7.0
5.0
5.0
5.0
Biochemical
Oxygen Demand
(mg/L)
5.0
3.0
10.0
50.0
5.0
Ammonia (mgN/L)
0.5
0.2
1.0
0.5
5.0
Nitrate (mgN/L)
0.7
1.0
0.7
0.7
0.7
Organic N (mgN/L)
0.6
0.9
0.6
0.6
0.6
Total Nitrogen
(mgN/L)
1.8
2.1
2.3
1.8
6.3
Total Nitrogen
(IbN/d)
52.5
49.2
67.2
52.5
184.1
Total Phosphorus
(mgPIL)
0.38
0.38
0.38
0.38
0.38
Parameters Below;Revised for WASP72.Met_ric Units
CBODu1(kg/d) (f-
ratio = 2.5)
165.6
79.5
331.2
1656.1
165.6
Ammonia (kgN/d)
6.6
2.1
13.2
6.6
66.2
Nitrate (kgN/d)
9.3
10.6
9.3
9.3
9.3
Organic N (kgN/d)
7.9
9.5
7.9
7.9
7.9
PO4 = Total
Phosphorus
(kgP/d)
5.0
4.0
5.0
5.0
5.0
Note: Bold font was used in the above table to indicate a value in a scenario which was different from the summer
Phase 3 permit scenario.
6.2 SENSITIVITY ANALYSIS RESULTS
The sensitivity analysis simulation output was developed similarly to the previous work which
investigated the various proposed phases. Each sensitivity scenario was compared to the No Havelock
scenario. The DO and chlorophyll -a output were aggregated to a surface daily simulated value, using
output from layer 3 and 4 at the proposed Havelock outfall location. The differences of the output were
evaluated for the 90th percentile, average, and 10th percentile statistics for the response variables DO and
chlorophyll -a. These results are presented in Table 6-2 for DO and Table 6-3 for chlorophyll -a. The
proposed summer Phase 3 differences to the No Havelock scenario are repeated in each table for
comparison purposes. Furthermore, the previous work which investigated the various phases indicated
that the surface simulation differences are most relevant to review.
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
Table 6-2. Summer Statistics of the Difference of DO (mg/L) Simulations for Surface, No
Havelock Versus the Noted Scenario
Summer
Phase 3
Permit
Scenario 1: Summer
Phase 3 Average
Performance
Scenario 2: Winter
Permit Limits for NH3
and BODE Applied to
Summer
Scenario 3:
Multiply
BOD5 10
Scenario 4:
Multiply NH3
by 10
90th
Percentile
0.01
0.02
0.02
-0.01
0.06
Average
-0.08
-0.04
-0.07
-0.11
0.00
10th
Percentile
-0.19
-0.10
-0.18
-0.24
-0.07
Table 6-3. Summer Statistics of the Difference of Chlorophyll -a (pg1L) Simulations for Surface,
No Havelock Versus the Noted Scenario
Summer
Phase 3
Permit
Scenario 1: Summer
Phase 3 Average
Performance
Scenario 2: Winter
Permit Limits for NH3
and BOD5 Applied to
Summer
Scenario 3:
Multiply
BOD5 10
Scenario 4:
Multiply NH3
by 10
90th
Percentile
0.55
0.50
0.72
0.55
1.60
Average
0.17
0.16
0.25
0.17
0.66
10th
Percentile
-0.03
-0.02
0.03
-0.03
0.24
The sensitivity analysis explored scenarios from a reasonable Phase 3 performance operating condition to
order of magnitude changes to important effluent constituents. The results of the sensitivity analysis
indicated that the average differences for DO and chlorophyll -a when compared to the differences
simulated by the Phase 3 permit scenario are small. Scenario 1, which considered representative summer
operating levels at Phase 3, resulted in the average DO difference decreasing to -0.04 mg/L. In Scenario
2, by applying the winter limits to the summer, the chlorophyll -a activity increased slightly which
resulted in a negligible impact to DO differences when compared against those generated from the Phase
3 permit scenario.
The remaining two scenarios, Scenarios 3 and 4, provided the most variations in differences in the
`a, sensitivity analysis. Generally, each explored an order of magnitude change to existing permit
concentrations for BOD5 and NH3, respectively. As anticipated, Scenario 3 created change in the DO
difference and no change in the chlorophyll -a difference as compared to those created by the Phase 3
permit scenario. The average DO difference was -0.11 mg/L compared to the value of -0.08 mg/L. That
is, an order of magnitude change in BOD5 (5 to 50 mg/L) produced a change in the DO difference of
-0.03 mg/L. The last scenario, Scenario 4, investigated an order of magnitude change (0.5 to 5.0 mgN/L)
to the ammonia concentration. The NRE is typically a nitrogen limited system therefore it was
anticipated that this scenario may affect both DO and chlorophyll -a response. While still small, this
scenario created the most impact in the chlorophyll -a simulation. The average chlorophyll -a difference
�` was 0.66 gg/L compared to 0.17 µg/L for the Phase 3 permit scenario. The slight increase in chlorophyll-
,, a activity actually produced enough dissolved oxygen that the average DO difference went to 0.0 mg/L,
compared to -0.08 mg/L for the Phase 3 permit scenario.
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
7 Conclusion
The Havelock WWTP outfall is proposed to be relocated from Slocum Creek to NRE. The proposed
,014
location is east of the existing MCAS CP WWTP outfall by approximately 0.6 miles (1 km); the MCAS
Anik CP WWTP permitted discharge was considered in this analysis. The proposed Havelock outfall was
considered as a submerged multiport diffuser. Three phases of discharge expansion were considered with
the proposed outfall relocation for the Havelock discharge. All three phases were reviewed for chronic
4/14 dilution and DO and chlorophyll -a response for a summer and winter critical period.
— A dynamic model framework was adopted for the investigation of the proposed relocation and expansion
of the Havelock discharge. An application of the calibrated coupled EFDC-WASP models for the larger
NRE was used to harvest ambient forcings for a finer (nested) model. This presented many benefits
— including the ability to investigate dilution as well as water quality through a dynamic simulation.
The results indicated that generally a chronic dilution of 100 was achieved after an approximate radius of
246 feet (75 m) from the outfall. Chronic dilution values of approximately 7 to 10 were common within a
radius of 82 feet (25 m) from the outfall.
The water quality results indicated that the impacts to DO and chlorophyll -a values near the outfall were
..� small. The average DO differences from the Phase 3 scenario compared to the No Havelock scenario
were less than 0.1 mg/L. Similarly, the chlorophyll -a average response difference was less than 1 µg/L.
DO and chlorophyll -a were considered particularly important and therefore a sensitivity analysis was
rr performed. The most stressful scenario was considered by using the summer critical period, Phase 3, and
adjusting the ammonia and BODS concentrations of the Havelock discharge up by an order of magnitude.
oft The results of this sensitivity analysis indicated that on average the DO difference when compared to the
No Havelock scenario was around 0.1 mg/L and less. Again, similarly, the chlorophyll -a average
response difference was less than 1 µg/L.
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Proposed Relocation of the Havelock Wastewater Treatment Plant Discharge December 2008
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