20061581 Ver 1_CAMA Application_20060929

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NCDENR
North Carolina Department of Environment and Natural Resources
Division of Coastal Management
Michael F. Easley, Governor Charles S. Jones, Director William G. Ross Jr., Secretary
u ~~~Q~~ D
September 27, 2006 5 E P 2 9 2006 2 0 0 g 1 g g 7
MEMORANDUM: u~~i~ • ~vAY'~a auAUn
WEt'LANDS AND S'r(~RMWIITER BRANCH
TO: Cyndi Karoly, Supervisor
401 Oversight & Express Permits Unit
Division of Water Quality-Surface Water Protection
FROM: Doug Huggett, Major Permits Coordinator
SUBJECT: CAMA /Dredge & Fill Permit Application Review
Applicant: New Hanover Co. /Well Field and Water Treatment Plant.
Project Location: Field: off of Plantation Rd. and Ogden Park; Site: off of Old Oak Rd; line
and discharge: off of Market St., Porters Neck rd., and Edgewater Club Rd.
Proposed Project: Applicant proposes to construct a new six million-gallon-per-day (mgd) groundwater treatment
plant and well field in the northern part of New Hanover County, with a discharge of two mgd of membrane concentrate to
the AIWW at the Figure Eight Bridge.
Please indicate below your agency's position or viewpoint on the proposed project and return
this form by October 20, 2006. If you have any questions regarding the proposed project,
please contact Robb Mairs or Jim Gregson at [phone], when appropriate, in-depth
comments with supporting data is requested.
REPLY: This agency has no objection to the project as proposed.
This agency has no comment on the proposed project.
This agency approves of the project only if the recommended changes are
incorporated. See attached.
This agency objects to the project for reasons described in the attached
comments.
SIGNED
DATE
127 Cardinal Drive Ext., Wilmington, North Carolina 28405-3845
Phone: [phone] FAX: [phone] Internet: www.nccoastalmanagement.net
An Equal Opportunity 1 Affirmative Action Employer - 50% Recycled 110% Post Consumer Paper

DIVISION OF COASTAL MANAGEMENT
FIELD INVESTIGATION REPORT
1. APPLICANT'S NAME: New Hanover County /Well Field and Water Treatment Plant
2. LOCATION OF PROJECT SITE: Well Field: off of Plantation Road and Ogden Park; plant site:
off of Old Oak Road; concentrate line and discharge: off of Market Street, Porters Neck Road, and
Edgewater Club Road.
Photo Index - 2000: 22-278 M-N 20 1995: 22-260 M-N 7 1989: 175-16 R-S 11
State Plane Coordinates - X: 2374330 Y: 193460 GPS - 0080416A
Lat:34°16'30.45822"N Long: 77°45'39.54155"W
3. INVESTIGATION TYPE: CAMA / D&F
4. INVESTIGATIVE PROCEDURE: Dates of Site Visit - 08/04/06
Was Applicant Present - No
5. PROCESSING PROCEDURE: Application Received - 09/6/06
Office -Wilmington
6. SITE DESCRIPTION:
(A) Local Land Use Plan- Wilmington /New Hanover
Land Classification From LUP -Conservation /Transitional
(B) AEC(s) Involved: ES, EW, PT, OR
(C) Water Dependent: Well site and treatment plant: No Discharge: Yes
(D) Intended Use: Public
(E) Wastewater Treatment: Existing- None
Planned- Six mgd groundwater treatment plant with concentrate
discharge to AIWW at Figure Eight Island Bridge
(F) Type of Structures: Existing- None
Planned- Treatment plant, well field and effluent discharge line with
diffuser structure
(G) Estimated Annual Rate of Erosion: N/A
Source - N/A
7. HABITAT DESCRIPTION: [AREA]
DREDCIFD FTT.T.F.D nTT~FR

(A) Vegetated Wetlands (Coastal / 404) 84,375 sq. ft.
0404) 2 787 s ft.
q'
Coastal
Wetlands
(Temporary)
(B) Non-Vegetated Wetlands (Open Water) 7,840 sq. ft.
(Temporary) 7,840 sq. ft.
(Temporary]
(C) Other - Highground disturbance 9 acres
(D) Total Area Disturbed: 9 acres
(E) Primary Nursery Area: No
(F) Water Classification: SA ORW Open: Yes

New Hanover County Well Field Discharge Line
Page Two
8. PROJECT SUMMARY:
The applicant proposes to construct a new six million-gallon-per-day (mgd) groundwater treatment
plant and well field in the northern part of New Hanover County with a discharge of two mgd of
membrane concentrate to the AIWW at the Figure Eight Bridge.
9. PROJECT DESCRIPTION:
The proposed project is located in the northern part of New Hanover County and consists of four
distinct project areas (waste treatment plant, well field, discharge line and outfall). New Hanover
County is proposing to construct a new six mgd groundwater treatment plant to serve fifteen new well
sites (30 wells). The membrane concentrate from the treated groundwater would be discharged
through 27,000 linear feet (5.1 miles) of 16-inch main to the outfall location south of the Figure Eight
Island Bridge at the AIWW. Only the outfall structure and a portion of the membrane concentrate
main are located with the 575' Outstanding Resource Waters Area of Environmental Concern.
The proposed water treatment plant (WTP) is located ~on a 47-acre tract of land off of Old Oak Road,
in the Ogden area of New Hanover County. This site consists primarily of uplands with six small
§404 Wetland pockets and a series of man-made ditches within and surrounding the property. The
U.S Army Corps of Engineers signed the wetland survey for this tract on March 10, 2006. The
ditches have been classified as waters of the U.S. Vegetation on the tract has been mowed and
consists primarily of Fetterbush (Lyonia htcida), Pepperbush (Clethra alnifolin), Cinnamon Fern
(Os~raunda ciniza~no»zea) and a few scattered Loblolly Pine (Pinus taeda). Two production wells have
been installed on the property. Production Well A is located in the northeast corner of the property
adjacent to Old Oak Road and Production Well B is located in the southwest corner of the property.
An existing dirt road traverses the property from east to west.
The proposed new well field sites are located in the Greenview Ranches Area and within the New
Hanover County Ogden Park tract. The Greenview Ranches area is located to the northeast of the
WTP site and consists primarily of undeveloped land and with the exception of existing un-maintained
dirt roads, is mainly §404 Wetlands. The County has purchased eight lots within this area for the
proposed well field sites. Each lot is approximately five acres in size. Vegetation on the lots consists
primarily of Pond Pine (Pinus serotina), Gallberry (Ilex glabra), Loblolly Bay (Gordonia lasiantha~s),
Titi (Cyrilla racemiflora) and Fetterbush (Lyonia la~cida).
The membrane concentrate line would run from the WTP site to Market Street, along the right-of-way
of Market Street, would then turn east onto the right-of--way of Porters Neck Road, right onto the
right-of--way of Edgewater Club Road and would continue to the AIWW to a point just south of the
Figure Eight Island Bridge.

New Hanover County Well Field Discharge Line
Page Three
The outfall structure would be located on the south side of the Figure Eight Island Bridge, on the
western bank of the AIWW. The outfall would extend off of property owned by Figure Eight Harbor
HOA. Wetlands adjacent to the AIWW at the outfall location consist of a border of §404 Wetlands
vegetated primarily with Sea Ox-eye (Borrichia frutescens), Marsh Elder (Iva frutescens), Groundsel-
tree (Baccharis halinailfolia) and Southern Wax Myrtle (Myrica cerifera) transitioning to mixed high
marsh vegetated with Glasswort (Salicornia spp.), Salt Grass (Spartina patens) and Spike Grass
(Distichlis spicata). Waterward of this high marsh fringe is an area Smooth Cordgrass (Sparti~za
alterniflora) averaging approximately 20-30 feet in width.
The waters of the AIWW at this location are classified SA-ORW by the North Carolina Division of
Water Quality. The area is not designated as a Primary Nursery Area by the North Carolina Division
of Marine Fisheries and is Open to the harvesting of shellfish.
PROPOSED PROJECT
Proposed development at the WTP site would include the construction of an access road entering the
property from Old Oak Road, parking lots, stormwater pond, administration building, WTP and two
1-million gallon circular, pre-stressed concrete tanks for finished water storage. (See Sheet 12 of 14
for detail of the WTP site). Permanent impacts to §404 Wetlands at the WTP site would total 24~ sq.
ft. Permanent impacts to waters of the U.S. at the WTP site from the filling of the existing ditches
would total 31,528 sq. ft.
Development associated with the well field sites would consist of the drilling of a total of 30 wells
from 15 well sites. Two of the well sites (Wells A and B) would be located within the WTP tract.
One well site (Well Q) would be located across Old Oak Road from the WTP site. Four well sites
(Wells M,N,O, and P) would be located within the Ogden Park Tract. The remaining eight well sites
(Wells C,F,G,H,I,J,K and L) would be located within the Greenview Ranches Area along Plantation
Road and two roads located perpendicular to Plantation Road. Atypical well site would consist of
two wells, well houses, generator, raw water lines and access roads. Permanent impacts to §404
Wetlands associated with the well field development would total 84,07 sq. ft. Permanent impacts to
waters of the U.S associated with the well field development would total 16,778 sq. ft.
Development associated with the construction of water mains would consist of two 6-inch to 30 inch,
parallel raw water transmission mains each approximately 17,000 linear feet (3.2 miles.) in length to
convey water pumped from both the Castle Hayne Aquifer and the Pee Dee Aquifer separately to the
WTP. After treatment approximately two mgd of membrane concentrate water would be discharged
through approximately 27,000 linear feet (5.1 miles) of 16-inch pipe to the outfall structure at the
AIWW. Temporary impacts to §404 Wetlands associated with the transmission line would total
approximately 23,933 sq. ft.
The proposed outfall structure would extend as a continuation of the 16-inch HDPE membrane
concentrate line from property located just to the south of the Figure Eight Island Bridge. The pipe
would be located approximately 20 feet south of the bridge and would be trenched through
approximately 225 feet of coastal and §404 Wetlands before reaching the open waters of the AIWW.
The pipe would continue via an open cut (4-feet deep by 4-feet in width) approximately 230 feet

New Hanover County Well Field Discharge Line
Page Four
waterward of the coastal wetlands to a point approximately 60 feet landward of the Figure Eight Island
Bridge fender system. The applicant states that the approximately 550 cubic yards of material would
be temporarily stockpiled next to the trench, creating a 35-feet wide disturbed area. After the pipe is
installed, the material would be returned to the trench. The 16-inch HPDE pipe would terminate in a
multi-port diffuser structure measuring approximately 8 feet in diameter. The 16-inch pipe would be
anchored in the bottom sediment with concrete collars measuring approximately 48 inches in width by
48 inches in depth by 12 inches thick. Collars would be spaced approximately 50 feet apart along the
pipe.. The proposed diffuser structure would be located near the -12 @ MLW contour .line. Up to 2
mgd of membrane concentrate would be discharged to the AIWW. The applicant is in the process of
applying for an NPDES Permit for the discharge. A copy of the NPDES Permit Application and
Environmental Assessment is attached.
10. ANTICIPATED IMPACTS: Construction of the project would disturb approximately nine acres of
high ground. The proposed project would permanently impact approximately 84,375 sq. ft. X404
Wetlands and 48,264 sq. ft. of Waters of the U.S. Approximately 23,958 sq. ft. of X404 Wetlands,
approximately 2,787 sq. ft. of Coastal Wetlands and approximately 7,840 sq. ft. of shallow bottom
would be temporarily impacted through the trenching of the outfall line along Porters Neck Road and
at the AIWW. It is unclear, at this time, what impacts the trenching of the discharge line would have
on shellfish resources. Please refer to attached report accompanying the NPDES Permit application
for a discussion of potential water quality impacts associated with the proposed discharge. The
applicant is proposing to mitigate for the permanent impacts to §404 Wetlands and Waters of the U.S.
by the recording restrictive covenants on all remaining wetlands within the well field lots to prohibit
future fill. The applicant is also proposing to restore at least 3.045 acres of freshwater wetlands within
the WTP tract off of Old Oak Road and is in the process of developing a complete mitigation plan.
Submitted by: Robb Mairs /Jim Gregson Date: September 26, 2006 Office: Wilmington

Form DCM-MP-1
APPLICATION
(To be completed by all applicants)
1. APPLICANT
2pos,5
8
Well Field: off of Plantation Road and Ogden Park•
Plant Site:_off of Old Oak Road; Concentrate Line: off
of Market Street, Porters Neck Road. and Edgewater
Club Road. See Proiect Narrative for details.
a. Landowner:
Name New Hanover County Engineering Dent.
c/o Mr. Gregory Thompson
Address 230 Market Place Drive. Suite 16
C1ty Wilmington State NC
d. Is proposed work within city limits or
planning jurisdiction? X Yes No
e. Name of body of water nearest project (e.g.
river, creek, sound, bay)
Smith Creek (headwatersl, Pages Creek and the
Atlantic Intracoastal Waterway
Zip 28403 Day Phone [phone]
Fax [phone]
b. Authorized Agent:
Name Land Manaeement Groun. c/o Ms. Kim Williams
Address P.O. Box 2522
City Wilmington State NC
Zip 28402
3. DESCRIPTION AND PLANNED USE OF
PROPOSED PROJECT
a. List all development activities you propose
(e.g. building a home, motel, marina, bulkhead,
pier, and excavation and/or filling activities.
Drilling and installing 30 wells, improving roads to
access wells. laving concentrate line in existing road
rights of way, installing outfall pipe at AIWW. Please
see Proiect Narrative and EA for additional details.
Day Phone [phone] Fax [phone]
c. Project name (if any) New Hanover County Well
Field and Water Treatment Plant
NOTE: Permit ~viCC6e issued in name of
landowner(s), and/or project name.
2. LOCATION OF PROPOSED
PROJECT
a. County New Hanover County
b. City, town, community or landmark
Wilmington, NC
c. Street address or secondary road number.
Revised 03/95
b. Is the proposed activity maintenance of an
existing project, new work, or both? New
c. Will the project be for public, private or
commercial use? Public
d. Give a brief description of purpose, use,
methods of construction and daily operations of
proposed project. If more space is needed, please
attach additional pages. The purpose is to provide
high quality. drinking water to northern New Hanover
County residents. Please see Proiect Narrative and EA
for additional details.
RECEIVE
C~CN1 WILh,1lNuTOf~d. ,~~C
SEP o s Zoos

Form DCM-MP-1
4. LAND AND WATER
CHARACTERISTICS
a. Size of entire tract Service Area: 88 s4. miles
b. Size of individual lot(s) N/A
c. Approximate elevation of tract above MHW
or NWL between 0 MSL at AIWW to 45 ft
above MSL at well fields
d. Soil type(s) and texture(s) of tract
Murville-Seagate-Leon Association (at well
fields and WTP)
e. Vegetation on tract Pinzzs taeda, Persea
borbonia, Ilex ~labra Mvrica cerifera
Gordonia lasianthus (well fields and WTP)
f. Man-made features no~v on tract dirt roads, test
wells, old ditches, park facilities at Oaden Park
g. What is the CAMA Land Use Plan land
CIaSSlficatlOn Of the Slte? (Cons:dt thelocal /and useplon.j
X Conservation
Developed
Rural
X Transitional
Community
X Other
h. How is the tract zoned by local government?
R-15 (Well Sites and WTPI
I. Is the proposed project consistent with the
applicable zoning? X Yes No
(Attach =oning compliance certificate, tf applicable)
j. Has a professional archaeological assessment
been done for the tract? Yes X No
If yes, by whom?
k. Is the project located in a National Registered
Historic District or does it involve a National
Register listed or eligible property?
Yes X No
1. Are there wetlands on the site? X Yes No
Coastal (marsh) X Other X
If yes, has a delineation been conducted? X
(Attach documentation, if available)
Revised 03/95
m. Describe existing wastewater treatment
facilities. N/A
n. Describe location and type of discharges to
waters of the state. (For example, surface runoff,
Sanitary wastewater, industrial/commercial
effluent, "wash down'' and residential discharges.)
Membrane discharge concentrate of up to 2
million Gallons per day
o. Describe existing drinking water supply
source.
This proiect would replace 20+ individual wells
scattered over northern New Hanover County
5. ADDITIONAL INFORMATION
In addition to the completed application form, the
following items must be submitted:
* A copy of the deed (with state application
only) or other instrument under which the
applicant claims title to the affected properties.
If the applicant is not claiming to be the owner of
said property, then forward a copy of the deed
or other instrument under which the owner
claims title, plus written permission from the
owner to carry out the project.
* An accurate, dated work plat (including plan
view and cross-sectional drawings) drawn to scale
in black ink on an 8 ''/z" by 11" white paper.
(Refer to Coastal Resources Commission Rule
7J.0203 for a detailed description.)
Please note that original drawings are preferred
and only high quality copies will be accepted.
Blue-line prints or other larger plats are
acceptable only if an adequate number of quality
copies are provided by applicant. (Contact the
U.S. Army Corps of Engineers regarding that
agency's use of larger drawings.) A site or
location map is a part of plat requirements and it
must be sufficiently detailed to guide agency
personnel unfamiliar with the area to
R~C~~`f~g;,)
~~C~~T 1NI! MINGTO~`V, ,^JC
~D 0 6 2006

Form DCM-MP-1
the site. Include highway or secondary road (SR)
numbers, landmarks, and the like.
* A Stormwater Certification, if one is
necessary.
* A list of the-names and complete addresses of
the adjacent waterfront (riparian) landowners
and signed return receipts as proof that such
owners have received a copy of the application
and plats by certified mail. Such landowners
must be advised that they have 30 days in which
to submit comments on the proposed project to the
Division of Coastal Management. Upon signing
this form, the applicant further certifies that such
notice has been provided.
Name Fieure Eisht Homeowners Association
Address 15 Bridee Road: Wilmin~on, NC 28405
Phone
Name Fieure Eiaht Harbor HOA
Address 1308 Edgewater Club Rd: Wilm. NC 28405
Phone
Name
Address
Phone
* A list of previous state or federal permits
issued for work on the project tract. Include
permit numbers, permittee, and issuing dates. A
NWP 33 was issued by the Coms to NHC for
temporary wetland impacts associated with the
installation of test wells (Action ID# 20030 1 1 881.
* A check for $250 made payable to the
Department of Environment, Health, and Natural
Resources (DEHNR) to cover the costs of
processing the application.
* A signed AEC hazard notice for projects in
oceanfront and inlet areas.
* A statement of compliance with the N.C.
Environmental Policy Act (N.C.G.S.113A -1 to
10) If the project involves the expenditure of
public funds or use of public lands, attach a
statement documenting compliance with the North
Revised 03/95
Carolina Environmental Policy Act.
6. CERTIFICATION AND PERMISSION
TO ENTER ON LAND
I understand that any permit issued in response to
this application will allow only the development
described in the application. The project will be
subject to conditions and restrictions contained in
the permit
I certify that to the best of my knowledge, the
proposed activity complies with the State ofNorth
Carolina's approved Coastal Management
Program and will be conducted in a manner
consistent with such program.
I certify that I am authorized to grant, and do in
fact, grant permission to representatives of state
and federal review agencies to enter on the
aforementioned lands in connection with
evaluating information related to this permit
application and follow-up monitoring of the
project.
I further certify that the information provided in
this application is truthful to the best of my
knowledge.
This is the 5~ day of ~z ~.-~liv , 20 66 .
Print Name Fl~++bcr (t ~ t!' . W; (I ;~,...,s
Signature V~/~
andowner or Authorized Agent
Please indicate attachments pertaining to your
proposed project.
X DCM MP-2 Excavation and Fill Information
X DCM MP-3 Upland Development
X DCM MP-4 Structures Information
DCM MP-5 Bridges and Culverts
DCM MP-6 Marina Development
NOTE: Please sign and date each attachment in
the space provided at the bottom of each
form.
R~CE~vE~
ACM WILMINGTON. NC
S E P 0 6 2006

Form DCM-MP-2
EXCAVATION
AND FILL
(Except bridges and culverts)
Attach this form to Joint Application for CAMA
Major Permit, Form DCM-MP-1. Be sure to
complete all other sections of the Joint
Application that relate to this proposed project.
Describe below the purpose of proposed
excavation or fill activities. All values to be
given in feet.
A~~eraQe Final
Existing Project
T.rn ath With Tla.:rh Tl,....t
Access channel
(MLW) or
~~-)
Canal
Boat
Basin
Boat
Ramp
Rock
Groin
Rock
Breakwater
Other (Excluding
shoreline 225' 4' 2'-10' 2'-l0'
stabiliz- (below MLW MLW
ation) MH`'~
1. EXCAVATION
a. Amount of material to be excavated from
below MHW or NWL in cubic yards ~ 550
R~CEi~/ED
DC~~I WiLN11NGT0iV, NC
c E P n 5 2006
b. Type of material to be excavated Sand
c. Does the area to be excavated include coastal
wetlands (marsh), submerged aquatic vegetation
(SAVs) or other wetlands? X Yes No
d. Highground excavation in cubic yards
150.000 cv for concentrate line (temporaryl
2. DISPOSAL OF EXCAVATED
MATERIAL
a. Location of disposal area In uplands and omen
water adiacent to concentrate line (tem orar~
b. Dimensions of disposal area
_ ~ 27,000 LF
c. Do you claim title to disposal area?
Yes X No
If no, attach a letter granting permission from
the owner. NHC is obtainingeasements
d. Will a disposal area be available for future
maintenance? _ Yes No
If yes, where? N/A
Revised 03/95

Form DCM-MP-2
e. Does the disposal area include any coastal
wetlands (marsh), SAVs or other wetlands?
Yes X No
f. Does the disposal include any area in the
water?
X Yes No (Temporary disposal at outfall)
3. SHORELINE STABILIZATION
a. Type of shoreline stabilization N/A
Bulkhead Riprap
b. Length N/A
c. Average distance waterward of MHW or
NWL
N/A
d. Maximum distance waterward of MHW or
NWL
N/A
e. Shoreline erosion during preceding 12 months
£ Type of bulkhead or riprap material
g. Amount of fill in cubic yards to be placed
below water level
(1) Riprap N/A
(2) Bulkhead backfill N/A
h. Type of fill material N/A
i. Source of fill material N/A
4. OTHER FILL ACTIVITIES
_ (Excluding Shoreline Stabilization)
a. Will fill material be brought to site?
X Yes No
If yes,
(1) Amount of material to be placed in the
water None
(2) Dimensions of fill area
N/A
(3) Purpose of fill N/A
b. Will fill material be placed in coastal wetlands
(marsh), SAVs or other wetlands?
X Yes No
If yes,
(1) Dimensions of fill area Perm: 1.937 ac of
404 wetlands, 1.108 ac of Waters of the U.S. Temp:
0.55 ac of 404 wetlands. 0.064 ac of coastal wetlands
(2) Purpose of fill Installation of wells and
surrounding access roads: installation ofwater lines and
concentrate line; construction of WTP.
5. GENERAL
a. How will excavated or fill material be kept on
site and erosion controlled?
Silt fences, seedins
b. What type of construction equipment will be
used (for example, dragline, backhoe, or hydraulic
dredge)?
Backhoe: small barge: excavator/drayline
c. Will wetlands be crossed in transporting
equipment to project site? X Yes No
If yes, explain steps that will be taken to lessen
environmental impacts.
Los~ine mats and construction corridors wilt be
used.
I-rC- Well ~~i l 4,,,..1 -a-r P
Applicant or Proje Name
Signature
~~S/o6
Date
r`~,EC1=9i./~~,
~:~CP,~1 W1LMI~~1GTGi~1. NC
c F ~= n ~ 200r
Revised 03/95

69/25/2665 14:6 9164526666 LANDh1ANAGEMENT
I+'orm bCM~MPT3
UPLAND
DEVELOPMENT
(Construction and/oar Tantd disturbing Activities)
Attach this form to Joint Application for CAMA
Major Permit, For DCM-MP-I. Be sure to
comptctc alt other sections of the Joint
Application that relate to this proposed project.
a_ Type and number of buildings, facilities, units
or structures proposed Construction of
groundwater treatment plant and i 5 well siteg•
installat-on of two water mains and one
concentrate line. Please sec EA and project
narratsve for details.
b. Number of lots or parcels N/A
PAGE 62162
Development Permit may also require a
StormwaterCertification. Has a site development
plan been submitted to the Division of
Environmental Management for review?
Yes X No
Tfyes, date submitted__ DesiErr in AroQress
i. Describe proposed method of sewage disposal.
Proiect will not create sewage
,j. Have the facilities described in Ttcm T_ above
received state or local approval? NlA
(Attach appropriate documentation)
c. Density (give the number of residential units
and the units per acre) NIA
d. Sipe of area to be graded, filled or dishrrbed
including roads. ditches, etc. WTP_;__~20 acres
V','ell sues: 0.25 ac per well site• Concentrate
route: ~ 9 acres (temporary)
e. ]f the proposed project will disturb more than
one acre of land, the Dirtision of Land Resources
must receive an erosion and sedimentation control
plan at least 34 days before land disturbing
activity begins. Ifapplicable, has a sedimentation
and erosion control plan been submitted to the
Division of.T_and Resources? Yes X No
if yes, date submitted Desi in progress
f. List tl~e materials (such as marl, paver stone,
asphalt, or concrete } to be used for paved
surfaces. WTP:.Concrete; Vb'ell Access Roads
gravel
g. Give the percentage of the tract within 75 feet
of MHW or NWL, or within 575 feet in the case
of an Outstanding Resource Water, to be covered
b}• impervious and/or built-upon surfaces, such as
pavement, buildings, rooftops, or to be used for
vehiculardrivcwaysorpa.rking. None
Projects that require a CAM/1, Major
Revi~cd 43/95
k. Describe location and type of proposed
discharged to waters of the state (for example,
surface runoff, sanitar}~ wastewater,
industriallcornmercial effluent, `wash down" and
residential discharges). Minimal surface runoff
from roads, well houses and plant Membrane
concentrate to fl w into the A1WW. NPDE
permit application has been submitted
1. Describe proposed drinking water supply
source (e.g. well, community, public system, etc.)
Proiect is a nronosed raw water supply source for
the northern art of New Hanover County.
m. Will water be impounded? Yes X Nc
if yes, how many acres^
n. Tf the project is an oceanfror;t development,
wl'hen was the lots} platt/e~d an((d~~ reco(rrded~?,/,N//1.
N~k) ~N1~ Wv~.( hl. 4i e.~d W I f
AppTieabt or Proj t Narge
$ignatgre
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Date -
~: ~ ~ - :; %C~~r:

PROJECT NARRATIVE
July 2006; revised September 2006
New Hanover County Well Field and Water Treatment Plant
New Hanover County, NC
1.0 INTRODUCTION
New Hanover County (County) proposes to improve its existing water supply and treatment for
the northeast~part of the County. This project includes additional treatment to improve finished water
quality and better management of groundwater supplies through better spacing of wells and balancing
water supplies from the Pee Dee aquifer and the Castle Hayne aquifer. The County is proposing to
construct a new six million-gallon-per-day (mgd) groundwater treatment plant (WTP) and well field
system in the northern part of the County. Fifteen well sites (two wells at each location for a total of 30
wells) will be used to tap into the Pee Dee and Castle Hayne aquifers. Two parallel raw water
transmission mains will transmit raw water from the well sites to the WTP. One main will transmit
water pumped from the Castle Hayne aquifer, while the other main will transmit water pumped from
the Castle Hayne aquifer. The County is also applying for a National Pollutant Discharge Elimination
System (NPDES) permit to discharge up to two mgd of membrane concentrate into the Atlantic
Intracoastal Waterway (AIWW) at the Figure Eight Bridge. Please note that an Environmental
Assessment for this project was prepared by Arcadis G&M of North Carolina, Inc. and submitted to
NCDENR; Division of Environmental Health. A Finding of No Significant Impact (FONSI) was
issued. Much of the information provided in this narrative was taken from the EA.
2.0 EXISTING CONDITIONS
The project area is located in the northern part of New Hanover County, NC (Sheet 1). The 88
square-mile service area encompasses the northern half of New Hanover County with the exception of
the US 421 corridor between the Cape Fear and Northeast Cape Fear Rivers (Sheet 2). The project area
is bounded by Pender County to the north, the City of Wilmington to the south, the Northeast Cape
Fear River to the east, and the Atlantic Ocean to the west. Below is a description of each project area
(WTP, well field, corridor, and outfall location). Please see Section 4 of the Environme~tars r~ertt~
for additional details. ~'CM WILMINGTQ;~1, NC
5EP 0 6 2006

t~-~ECEIVE.~
ACM WILMING?-G~N. NC
Water Treatment Plant
S E P 0 6 2006
The proposed Water Treatment Plant (WTP) is 44 acres in size and is located off of Old Oak
Road in the Ogden area of New Hanover County (Sheet 3). According to the New Hanover County
Generalized Soil Survey, the site consists of Johnston loam, Murville fine sand, and Seagate fine sand
soil types (Sheet 4). Historically, this site most likely supported a wet pine flatwood community type.
However, the area has been significantly altered through time. Several ditches were placed within and
around the tract many years ago to drain the site. Only a few wetland pockets now exist within the tract
and the ditches have been classified as Waters of the U.S. Ms. Jennifer Frye of the U.S. Army Corps of
Engineers signed the wetland survey for this site on March 10, 2006 (Sheet 5). Vegetation within the
site has been mowed and consists mostly of fetterbush (Lyonia lucida), sweet pepperbush (Clethra
alnifolia), and cinnamon fern (Osmunda cinnamomea) in the herbaceous layer, with a few scattered
loblolly pine (Pinus taeda) trees in the canopy. A dirt path approximately 20'-wide runs east-west
across the site. Two wells have already been installed within the tract; one located in the southeast
corner near Old Oak Road (Well A) and one located in the northwest corner (Well B) of the site.
Surrounding land use is residential or undeveloped. The property is located within the New Hanover
County jurisdiction. The property is currently zoned for single-family residential (R-15) and is
classified as a Wetland Resource Protection Area by the New Hanover County Land Use Plan. All
properties adjacent to the site are currently zoned for single-family residential (R-15). A threatened and
endangered species evaluation was performed for this site in December of 2004. No federally-
protected species were observed. Please see Appendix E of the EA for the complete report.
Well Field Sites
Fifteen well sites are proposed for the well field (Sheet 6). Two of these are existing well sites
at the WTP tract. One well site is located across the road from the WTP. Ten well sites are proposed
within Greenview Ranches and four well sites are proposed within the Ogden Park tract. Eight lots
within the Greenview Ranches area have been purchased by the County. These undeveloped, forested
lots are each approximately five acres in size. Dirt roads were installed many years ago to provide
limited access to the area. Plantation Road runs east west between Murrayville Road and terminates
just before reaching Market Street. This road is approximately 22' wide and has ditches running
parallel to it for a majority of its length. Several smaller dirt roads run north-south through the area.
These roads have not been maintained as well as Plantation Road and large potholes (some of which
have naturalized back to wetlands) exist throughout them. Ditches (Waters of the U.S.) run parallel to
2

GCw1 V`JILMi~~!~~TON, I~JC
SFF 0 6 2000
most of these roads. According to the New Hanover County Generalized Soil Survey, these lots consist
of Leon fine sand (Sheet 4). Most all of these lots consist entirely of 404 wetlands, however upland
areas were found on lots K and L. Furthermore, old ditches that were dug parallel to the existing dirt
roads have a minor drainage effect on the lot located furthest north (J). Surrounding land use is
residential, agricultural (horse farms), or undeveloped. Vegetation within these lots consists of pond
pine (Pinus serotina), gallberry (Ilex glabra), loblolly bay (Gordonia lasianthus), titi (Cyrilla
racemiflora), and fetterbush (Lyonia lucida). These sites are classified as a Wetland Resource
Protection Area by the New Hanover County Land Use Plan.
Four additional well sites are proposed within the Ogden Park tract. This tract is 160 acres in
size and is located off of Market Street (Sheet 7). The County received a Nationwide Permit 26 in 1993
to fill 5.71 acres of wetlands for park facilities. This acreage plus the natural uplands have been
developed into a park that contains baseball fields, soccer fields, tennis courts, playgrounds, rest
rooms, a picnic area, a trail, a pet exercise area, and parking (Sheet 8). The wetlands are forested and
support Murville fine sand soils (Sheet 9). The uplands support Leon fine sand soils. The wetland
survey for these areas is included in this permit application for final Corps approval. This site is
classified as a Wetland Resource Protection Area by the New Hanover County Land Use Plan.
Route of Concentrate Main
The proposed route of the concentrate main will lead from the WTP, along the right of way of
Market Street and then turn right onto the right of way of Porters Neck Road (Sheet 1). The line will
then turn right onto Edgewater Club Road and follow this road to the Atlantic Intracoastal Waterway at
the Figure Eight Bridge.
Outfall Location
The project proposes to discharge up to two mgd of membrane concentrate into the Atlantic
Intracoastal Waterway (AIWW), on the south side of the Figure Eight Bridge (Sheet 10). The AIWW
in this area is classified as SA and Outstanding Resource Water. The SA classification indicates salt
waters used for market shellfishing. The ORW classification is for unique and special surface waters
that are of exceptional state or national recreational or ecological significance and have exceptional
water quality. The average tide range in the AIWW near the Figure Eight Island Bridge is 3.58 feet.
The mean water depth at the proposed discharge location is approximately 12 feet at low tide.
3

i~ECrcivE~
~~>CM WILMINGTON, NC
Freshwater and coastal wetlands have been delineated adjacent to the AIWW and an estuarine Area of
Environmental Concern is located 575' landward of mean high water. The portion of the AIWW in
which the discharge is proposed is an area that is presently open for shellfishing. The adjacent land use
is residential and a boat ramp and pier exist in this vicinity for water access. According to the New
Hanover County Soil Survey, upland soils consist of Wakulla and wetland soils are Tidal Marsh muck
(Sheet 11). Please see the attached NPDES permit application for additional tide data from this area
and a mixing zone analysis (Appendix B).
3.0 PROJECT NEED
Please see Section 2 of the Environmental Assessment for a detailed description of the need for
the project.
4.0 ALTERNATIVES ANALYSIS
Section 3 of the Environmental Assessment describes a no-action alternative, the purchase of
raw water from several other sources, and aCounty-owned surface water treatment plant. At the time
that the EA was prepared, the exact location of the well fields had not yet been determined and an
alternatives analysis for the specific placement of the wells could not be given. This section of the
project narrative describes the factors that dictated the proposed placement of the well fields within
New Hanover County.
Selection of Well Field Sites
The mid-section of New Hanover County was selected as a potential water supply
because of aquifer recharge characteristics determined in groundwater evaluations performed
by BPA Environmental and Engineering, Inc. in 1995 and by Edwin Andrews & Associates,
P.C. in 1996. It is preferable that the wells be placed in an undeveloped area to prevent
groundwater contamination. The Greenview Ranches area is located in the target area and is
largely undeveloped. However, the majority of the Greenview Ranches area consists of
wetlands except for existing dirt roads. To minimize potential impacts, the area was examined
to identify lots that contained uplands. The County attempted to purchase lots with uplands, but
acquisition was largely dictated by those owners who were willing to sell. Mr. Phil Triece, a
local real estate consultant, contacted many landowners to determine who was willing to sell
their property.
4

The proposed location of the wells has been centralized as much as possible to reduce
necessary roadway improvements between well sites. Only those lots located directly off of
three existing roads were purchased. However, the 2001 Concept Design Report indicated that
the wells should be spaced between 800 and 1600 feet apart to ensure an even withdrawal of
the aquifers.
5.0 PROPOSED PROJECT
Please see Section 1 of the Environmental Assessment (Proposed Project Description) for a
detailed description of the proposed project.
Water Treatment Plant
The proposed WTP will be located in the northwestern portion of the property off of Old Oak
Road (Sheet 12). The northern portion of the WTP site is reserved for wetlands mitigation to offset
impacts from the WTP site, well sites, and other offsite construction activities. The southern portion of
the parcel as well as the remaining northern portion of the property is reserved for future County uses.
The proposed access road will connect with Old Oak Rgad opposite of Rochelle Road. The
main plant entrance and exit will be located along the southern property boundary. It will be equipped
with an electric slide gate. All roadways will be asphalt pavement roads. Most roads will be 24-feet
wide with the exception of the chemical unloading area, which will have a 12-ft wide road. The
visitors parking area will be located adjacent to the Administration Building and will include
handicapped spaces for staff and visitors. Parking for WTP staff will be located behind the WTP
building. Parking is also proposed for plant operators and maintenance staff near the Chemical Storage
Area.
The primary treatment process for the WTP will be nanofiltration for softening total organic
carbon (TOC) removal and color removal. Separate membrane filtration units will be provided for the
two source waters to alleviate the potential for membrane fouling from biological growth or saturated
salts. Treatment processes will include cartridge filtration and nanofiltration in series. Following
nanofiltration, permeate from both the Pee Dee and Castle Hayne treatment trains will be blended and
conveyed to packed tower aerators for removal of carbon dioxide, hydrogen sulfide, and oxidation of
any remaining iron in the permeate. Sodium hypochlorite, sodium hydroxide, and corrosion inhibitor
RIEC~9'~°t=~~~
ACM WIL}>>,iP~~r ~ ~.~~~~. P~i~-
5 S E P 0 6 2006

will be added and then the finished water will be stored in two 1.0-million gallon clearwells prior to
pumping to the distribution system.
Two 1-million gallon (MG) circular, pre-stressed concrete tanks will be provided for finished
water storage. The proposed tanks will be 100-feet diameter with 17-ft side water depth. Each tank
will include curtain-type baffle constructed of Hypalon and stainless steel hardware. Influent
connection will be 24-inch diameter and effluent connection will be 30-inch diameter. A tank overflow
and drain will be piped to an onsite stormwater detention pond. Level will be recorded and reported to
SCADA by an ultrasonic level indicator and transmitter.
Well Field Sites
Fifteen well sites are proposed within the northern part of New Hanover County (Sheet 6). Both
the Castle Hayne and Pee Dee aquifers will be tapped at each well site. Therefore, the 6-mgd WTP will
have a total of 30 wells. Two of the well sites (Wells A & B) will be located within the WTP tract. One
well site (Well Q) will be located across the road from the WTP. Four well sites (Wells M, N, O, & P)
will be located within the Ogden Park Tract. The remaining eight well sites (Wells C, F, G, H, I, J, K,
& L) will be located along Plantation Road and two roads located perpendicular to Plantation Road.
Wells must be placed at least 100 feet from any property line, but will be installed as close to the roads
as possible to reduce wetland impacts from the proposed driveway. The width of roadway
improvements will be minimal; only a 12' wide gravel road is proposed with 2' shoulders (Appendix
C; C 10). This will minimize wetland impacts from the road and reduce access by trespassers.
Route of Water Main
Two parallel raw water transmission mains will be constructed to convey raw water from the
well sites to the WTP. One main will convey water pumped from the Castle Hayne aquifer, and the
other main will transmit water pumped from the Pee Dee aquifer. Raw water from each aquifer is
conveyed to the WTP separately to avoid potential biological fouling. Each raw water transmission
main will consist of approximately 17,000 feet (3.2 miles) of line ranging in size from 6-inch to 30-
inch, for a total of 34,000 feet (6.6 miles) of main. Both raw water transmission lines will be located
mainly within the right-of--way of existing unimproved roads in the well field.
RECEivE~
DCM WILMIf~JGTO^1. ~`~
S E P 0 6 2006
6

Outfall Location
The project includes installation of approximately 27,000 feet (5.1 miles) of 16-inch membrane
concentrate discharge line. This discharge line will be routed from the WTP site south to US 17, run
northeast along US 17, east on Porters Neck Road, and southeast along Edgewater Club Road toward
the bridge to Figure Eight Island.
The proposed discharge location is at the Figure Eight Island Bridge at Bridge Road (Sheets 13
& 14). The County is proposing to discharge up to 2 mgd of membrane concentrate to the AIWW. The
proposed discharge would include amulti-port diffuser outfall located along the bottom of the AIWW.
The diffuser would be within the bridge easement of the USACE's AIWW right-of--way. During the
NCSEPA process, the planned design for the effluent outfall structure was to suspend the pipeline
under the bridge structure and the have the pipeline rune vertically down the last set of pilings west of
the bridge fender system. Consultation with the bridge designers resulted in several logistical problems
with attaching the effluent pipeline to the bridge. The issues were as follows:
1. Penetration of the concrete bridge abutment with the pipeline.
2. Uncertainties with attaching suspension elements to an aging concrete girder structure.
3. Foreseeable future maintenance of the bridge that might cause disruption in the use of the
outflow pipeline within the next decade.
For these reasons it was determined that the best course of action was to make the pipeline a
stand-alone structure. The pipeline will be placed underground, utilizing trench and fill construction
methods, out to approximately the -10.0 ft mean low water contour, the extend 55' along the seabed to
the diffuser structure. The pipeline will be secured by a series of pre-cast 4'x4'xl' concrete collars.
The end of the structure will be approximately 60' west of the western bridge fender.
During initial construction, it will be necessary to temporarily excavate 225-ft long, by 4-ft
deep, by 4-ft wide trench with 3:1 side slopes. The trenching operations will result in the excavation of
550 cubic yards of sandy material and the temporary disturbance of a marine area 35-ft wide by 225
long. The area of temporary disturbance includes the area to be utilized for temporary stockpiling of
material. The trench will be dug utilizing a small barge and excavator/dragline. Material will be
excavated and temporarily placed on the seabed next to the trench. After the pipeline is installed,
material excavated from the trench will be returned to the trench, burying the effluent line. Final grades
will be within +/- 1 ft of pre-construction conditions. The mean water depth at the proposed discharge
location is approximately 12 feet at low tide.

7 CEP 0 >; 2GC6

6.0 POTENTIAL ENVIRONMENTAL IMPACTS
Direct Im acts
The proposed project would permanently impact 1.937 acres of 404 wetlands and 1.108 acres
of Waters of the U.S. (Appendix C). In addition, 0.55 acre of 404 wetlands, 0.064 acre of coastal
wetlands, and 0.18 acre of open water will be temporarily impacted through the open cut installation of
the pipe along two places at Porters Neck Road and at the outfall location adjacent to the Figure Eight
Bridge. Excavated material along the concentrate line corridor will be placed in adjacent uplands and
the area will be returned to grade and seeded once the pipe has been installed. Excavated material
below MHW will be temporarily placed on the seabed next to the trench. After the pipeline is installed,
material excavated from the trench will be returned to the trench, burying the effluent line. Final grades
will be within +/- 1 ft ofpre-construction conditions.
This discharge location would be directly adjacent to an open shellfish area, but the effluent is
not expected to affect the shellfish. Additionally, this discharge location is not expected to have any
navigation issues since the mean water depth at the proposed discharge location is approximately 12
feet at low tide at the diffuser will be located adjacent to a bridge fender.
Secondary/Cumulative Impacts to Region
Secondary impacts to wetlands and water quality could occur during and after construction of
the project through erosion and stormwater runoff. These potential impacts will be minimized by the
development and implementation of a Stormwater Plan and a Sedimentation and Erosion Control Plan.
These plans will reduce the potential for erosion or runoff into wetlands and other water bodies located
off site.
The report that accompanies the NPDES permit application evaluates the potential effect that
the proposed discharge from the WTP could have on the salinity of the AIWW and the surrounding
salt marsh in the vicinity of the outfall location. This report found that because of the rapid dilution and
persistent tidal flows in the outfall area, the diffuser will have minimal influence upon the surrounding
salinity regime. Therefore, no negative impacts to water quality from the concentrate are anticipated.
It is important to note that the project does not intend to stimulate growth in Greenview
Ranches, which could create secondary wetland impacts in the region. In fact, it is to the benefit of this
project if development in the Greenview Ranches area is managed in order to protect water quality.
The County is currently preparing an ordinance that would manage growth in the well site area.
8
~~C~6VED
JCt~;~ WIL~i91NGT0~U. iUC

Furthermore, this project will not provide utilities to the Greenview Ranches area. The water being
withdrawn from these proposed wells will be raw. The project will not supply potable water to the
area. In addition, most of the lots in this area will not perk and sewer is not available to this part of the
County. Therefore, additional growth within the area will not be stimulated by this project.
7.0 MITIGATION
The applicant has attempted to avoid and minimize environmental impacts as much as possible.
Wells will be placed in uplands when possible and will be located as close to the roads as permissible
(at least 100' from any property line) to reduce wetland impacts associated with the driveways. The
width of access roads will be minimal (12') to further reduce impacts (Appendix C; Sheet C10).
No permanent wetland impacts will occur from the installation of the water main. The County
will cross wetlands by open cut or by directional drill along Porters Neck Road and Edgewater Club
Road (Appendix C; Sheets C5, C6, & C10). After the pipeline is installed, material excavated from the
trench will be returned to the trench, burying the effluent line. Final grades will be within +/- 1 ft of
pre-construction conditions.
To mitigate for. the 3.045 acres of proposed permanent impacts to 404 wetlands and Waters of
the U.S., restrictive covenants will be recorded on all remaining wetlands within the well field lots to
prohibit any wetland fill beyond what is being requested here. This will protect approximately 25 acres
of wetlands. Finally, the applicant plans to restore at least 3.04 acres of freshwater wetlands within
the WTP tract off of Old Oak Road (Sheet 12). The applicant is in the process of developing a
complete mitigation plan for the proposed restoration.
GCN1 WILMINGT~J~~. '`~<
9 SEP ~? 6 20~F~

LIST OF SHEETS
Sheet 1 Vicinity map of project area
Sheet 2 Service area for project
Sheet 3 Topographic map of WTP and Well Fields
Sheet 4 SCS Soils Map for WTP and Well Fields
Sheet 5 Wetland Survey for WTP
Sheet 6 Aerial photograph of Well Fields
Sheet 7 Topographic map of Ogden Park
Sheet 8 Aerial Photograph of Ogden Park
Sheet 9 SCS Soils Map of Ogden Park
Sheet 10 Topographic Map of Outfall Location
Sheet 11 SCS Soils Map of Outfall Location
Sheet 12 WTP Site Design
Sheet 13 Diffuser Plan View with Elevations
Sheet 14 Cross Section of Diffuser
Appendix A. Environmental Assessment
Appendix B. NPDES Permit Application
Appendix C. Wetland/Waters of the U.S. Impact Maps (C1-9)
Cross Section of Access Road and Directional Drill (C 10)
Cross Section of Typical Well Field Site (C11)
10

CROSS
SECTION 1
CASTLE HAYNE
WELL
(GENERATOR
PAD
PEE DEE
WELL
60' ROW
FENCE
LIMIT OF CONSTRUCTION DISTURBANCE
tT LAYER OF ABC STONE
\ PEE DEE WELLHEAD
CONCRETE PAD
CASTLE HAYNE WELLHEAD
CONCRETE PAD
ERATOR STRUCTURAL FILL
CRETE PAD (IF NESSISARY)
GEOTEXTILE
RESIDUAL SOIL
WATER LINE
FROM WELL
PEE DEE
WATER LINE
STLE HAYNE
TER LINE
WATER LINE
FROM WELL
PRELIMINARY DOCUMENT -NOT FOR CONSTRUCTION
WK 909 MARKET STREET Date : 9/f /06 TYPICAL WELL SITE CROSS SECTION
Wi1.MINGTON, NC 28401
~ICKSON (9'0) ~s2-a2oo scale: NTS NEW HANOVER COUNTY W&S DISTRICT
once Locutions: Drawn : JRW W{LMINGTON, NORTH CAROLINA
community Infrastructure consultants North Carolina Georgia Chk: PLG SHEET 1 OF 1
South Carolina Florida prof. No: 90911.80
SHEET C11
C~.~,IA {!MAJOR PERMIT APPLICATION

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CAMA Major Permit Application
~~.6
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NHC Well Field and WTP
Proposed Well Locations
SCALE 1" = 1500'
New Hanover County, Nc Land Management Group, lnc. SHEET 3 of 14
01-05-371 Environmental Consultants USGS Topgraphic Map
Wilmington, N.C. of Well Sites and WTP
CAMA Major Permit Application July 2006
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NHC Well Field and WTP
New Hanover County, NC Land Management Group, Inc. SHEET 4 of 14
01-05-371 Environmental Consultants Soils Map for
Wilmington, N.C.

CAMA Major Permit Application
July 2006 Well Field and WTP

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Map Source: 1998 NAPP aerial photography
NHC Well Field and WTP
New Hanover County, NC
01-05-371
CAMA Major Permit Application
Land Management Group, Inc.
Environmental Consultants
Wilmington, N.C.
July 2006
SCALE 1 " = 1500'
SHEET6of14
Aerial Photograph of
Well Field and WTP

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NHC Well Field and WTP
New Hanover County, NC Land Managemenl* Group, Inc. SHEET 7 of 14
01-05-371 Environmental Consultants USGS Topographic Map
Wilmington, N.C. of Ogden Park Tract
CAMA Major Permit Application December 2005

Map Source: 1998 NAPP aerial photography
NHC Well Field and WTP
New Hanover County, NC
01-05-371
CAMA Major Permit Application
1 ~
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Environmental Consultants
Wilmington, N.C.
July 2006
SCALE 1" = 800'
SHEET 8 of 14
Aerial Photograph of
Ogden Park Tract
I~

Map Source: NRCS Soils Map.
NHC Well Field and WTP
New Hanover County, NC
01-05-371
CAMA Major Permit Application

Land Management Group, Inc.
Environmental Consultants
Wilmington, N.C.
July 2006
SCALE 1" = 800'
SHEET9of14
Soils Map of
Ogden Park Tract

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SCALE 1" = 800'
Map Source: Scotts Hill Quadrangle 7.5 minute (topographic) 1990.
NHC Well Field and WTP
New Hanover County, Nc Land Management Group, lnc. SHEET 10 of 14
01-05-371 Environmental Consultants
Wilmington, N.C. USGS Topographic Map
CAMA Major Permit Application July 2006 of Outfall Location

*Boundaries are approximate and are r ~~ SITE
not meant to be absolute.
Map Source: NRCS Soils Map.
NHC Well Field and WTP
New Hanover County, NC
01-05-371
CAMA Major Permit Application
Land Management Group, Inc.
Environmental Consultants
Wilmington, N.C.
July 2006
SCALE 1" = 400'
SHEET 11 of 14
Soils Map of
Outfall Location

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~~ ,
_. .; Z~06
APPENDIX C. Wetland /Waters of the U.S. Impact Maps
20061581

List of Wetland and Waters of the U.S. Impacts
'~~<=LIVED
,~~l~l VUIL~viIfJGT~~~,1 ~~
±U!_ 3 ~ 20G5
Permanent Area
404 Wetland
Im act Area
Square Feet
Acres Location
1 574 0.013 Well Field
2 1461 0.034 Well Field
3 825 0.019 Well Field
4 109 0.003 Well Field
5 3910 0.090 Well Field
6 11911 0.273 Well Field
7 377 0.009 Well Field
8 264 0.006 Well Field
9 9831 0.226 Well Field
10 207 0.005 Well Field
11 12227 0.281 Well Field
12 10485 0.241 Well Field
13 18952 0.435 Well Field
14 11091 0.255 Well Field
15 1492 0.034 Well Field
16 359 0.008 Well Field
17 245 0.005 WTP
Total 84320 1.937
Permanent Area
Waters of tue U.S.
Im act Area
Square Feet
Acres Location
1 1324 0.030 Well Field
2 483 0.011 Well Field
3 621 0.014 Well Field
4 5861 0.135 Well Field
5 562 0.013 Well Field
6 529 0.012 Well Field
7 221 0.005 Well Field
8 188 0.004 Well Field
9 575 0.013 Well Field
10 41 0.001 Well Field
11 3620 0.083 Well Field
12 728 0.017 Well Field
13 692 0.016 Well Field
14 784 0.018 Well Field
15 549 0.013 Well Field
16 1890 0.043 WTp
17 439 0.010 WTp
18 29199 0.67 WTP
Total 48306 1.108

List of Wetland and Waters of the U.S. Impacts Contd.
Temporary Area
404 Wetland
Im act Area
Square Feet
Acres Location
1 1699 0.039 Concentrate
2 695 0.016 Concentrate
3 24 0.001 Concentrate
4 754 0.017 O den Park
5 20761 0.477 Outfall
Total 23933 0.55
Temporary Area
Coastal Wetland
Im act Area
Square Feet
Acres Location
1 2807 0.064 Outfall
Total 2807 0.064

TEMPORARY
404
WETLAND

AREA

LOCATION
IMPACT AREA SQUARE FEET ACRES SHEET
1 1699 0.039 C5
2 695 0.016 C5
3 24 0.001 C5
4 754 0.017 C6
5 20761 0.477 C9
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WETLAND
AREA
LOCATION
IMPACT AREA SQUARE FEET ACRES SHEET
1 574 0.013 C2
2 1461 0.034 C2
3 825 0,019 C2
4 109 0.003 C2
5 3910 0.090 C3
6 11911 0.273 C3
7 377 0.009 C3
8 264 0.006 C3
9 9831 0.226 C3
10 207 0.005 C3
11 12227 0.281 C3
12 10485 0.241 C3
13 18952 0.435 C7
14 11091 0.255 C4
15 1492 0.034 C7
16 J59 0.008 C8

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TEMPORARY
COASTAL
WETLANDS AREA LOCATION
IMPACT AREA SQUARE FEET ACRES SHEET
1 2807 0.064 C6
WATERS
OF THE U.S. AREA LOCATION

IMPACT AREA
SQUARE FEET
ACRES SHEET
1 1324 0.030 C2
2 483 0.011 C2
3 621 0.014 C2
4 5861 0.135 C2
5 562 0.013 C2
6 529 0.012 C2
7 221 0.005 C3
B 188 0.004 C3
9 575 0.013 C4
10 41 0.001 C4 1
it 3620 0.083 C4
12 728 0.017 C7 i
13 692 0.016 C7 I
14 784 0.018 C7 I
15 549 0.013 C7
i6 1890 0.043 C11 I
17 439 0.010 C8
® WETLAND IMPACT AREA
SCALE 1'=2000'
WUS IMPACT AREA
WUS = WATERS OF THE UNITED STATES
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NEW HANOVER COUNTY
WATER AND SEWER DISTRICT WATERS OF TAH~U.S. IMPACTS INDEX
WELL FIELD h WATER TREATMENT FACILITY
REW HANO4fR counn, NOR1H cAROUe~ WETLAND IMPACTS

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NEW HANOYER COUNTY WATERS OF THE U.S. IMPACTS
WATER AND SEWER DI5TRICT AND
WELL FIELD d WATER TREATMENT FACILITY
'E'"' ""N01B1 C°'"~'` NORT" CAfD1"" WETLAND IMPACTS

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WATER AND SEWER DISTRICT AND
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WATER AND SEWER DISTRICT AND
WELL FIELD b. WATER TREATMENT FACILITY
'E'"f1At01@' C01"TM~ 10Fn" CAi01JA WETLAND IMPACTS ~ D

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WELL FIELD b. WATER TREATMENT FACILITY 1 O
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WATER AND SEWER DISTRICT AND
WELL FIELD ~ WATER TREATMENT FACILITY .~ ()
'E"' HAN01Bi ~'' NORTM °A~"" WETLAND IMPACTS

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WATER AND SEWER DISTRICT C8
WELL FIELD d WATER TREATMENT FACILITY AND
't"' "AND1'~' C01""'• N0"TM ~""0Li" WETLAND IMPACTS ~ ~'

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NOTES:
1. CONTRACTOR SHALL NOT DISTURB
EXISi1NG DITCH.
TYPICAL SECTION - GRAVEL AC CESS RO AD & PIPES
NOT TO SCALE
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NEW HANOVER COUNTY WATERS OF THE U.S. IMPACTS C10
WATER AND SEWER DISTRICT AND
WELL FIELD ~ WATER TREATMENT FACILITY 10
'E"' HA101'a' ~"TM• "0N1X 0AR0LNA WETLAND IMPACTS

ra
' 20081581
NPDES PERMIT APPLICATION -SHORT FORM C - WTP
For discharges associated with water treatment plants
~tECEIVED
Mail the complete application to: ~~ ~ ~~ v'~l ~ ~ ~,~,} ~ ~ \~ ~ ~ ~ ~~ , ,~ ~ ~,
N. C. Department of Environment and Natural Resources
Division of Water Quality / NPDES Unit ~ i, ~ 2 C
1617 Mail Service Center, Raleigh, NC 27699-1617
lYPDES Per~~i: N~rtaber NC00
If you are completing this form in computer use the TAB key or the up -down arrows to moue from one
field to the next. To check the boxes, click your mouse on top of the box. Otherwise, please print or type.
1. Contact Information:
Owner Name New Hanover County Water and Sewer District
Facility Name New Hanover County Water Treatment Plant and Well Field System
Mailing Address 230 Market Place Drive
City Wilmington
State /Zip Code NC/28403
Telephone Number [phone]
Fax Number [phone]
e-mail Address
2. Location of facility producing discharge:
Check here if same as above ^
Proposed WTP site is located on a 44-acre parcel
northwest of US 17 (Market St). The property is bounded
Street Address or State Road
by Old Oak Road to the southeast and the proposed
Military Cutoff Extension Corridor to the northwest.
City Wilmington
State /Zip Code NC/28411
County New Hanover County
3. Operator Information:
",Tci.Yne oft"~fiT~±. cors7~ltant or other entity that operates the facility. (Note that this is not refemng to the
Operator in Responsible Charge or ORC)
Name W.K. Dickson & Co, Inc.
Mailing Address 909 Market St
City
State /Zip Code
Telephone Number
Fax Number
4. Ownership Status:
Page 1 of 1
Wilmington
NC/28401
[phone]
[phone]
C-WTP 03/05

4t
RECEIVED
~DCM V!!1LMINGTQ,~1, n1C
U!_ 3 a 2~0
APPENDIX B. NPDES Permit Application

f t
5. Type of treatment plant:
^ Conventional (Includes coagulation, flocculation, and sedimentation, usually followed by
filtration and disinfection)
NPDES PERMIT APPLICATION -SHORT FORM C -WTP
For discharges associated with water treatment plants
Federal ^ State ^ Private ^ Public
^ Ion Exchange (Sodium Cycle Cationic ion exchange) ~, , ~, ~_ , ,
® Green Sand Filter (No sodium recharge) - ` ~ ~ ' ,, ~ : _ j,~ ~:
® Membrane Technology (RO, nanofiltration)
Check here if the treatment process also uses a water softener ^
6. Description of source water(s) (i.e. groundwater, surface water)
Groundwater: 50% acquired from the Pee Dee aquifer and 50% from the Castle Hayne aquifer
7. Describe the treatment process(es) for the raw water:
The proposed New Hanover County WTP is a 6-mgd groundwater treatment facility that will
treat water from the Pee Dee and Castle Hayne aquifers. The primary treatment process
wii:: be _~anofil'::-ation for softening total organic carbon (TOC) removal and color removal.
Separate membrane filtration units will be provided for the two source waters to alleviate
the potential for membrane fouling from biological growth or saturated salts. In addition,
raw water from the Castle Hayne has high iron levels and requires pre-treatment prior to
membrane filtration.
The total capacity of the Pee Dee treatment train will be 3.0 mgd, which equates to a raw
water feed rate of approximately 3.6 mgd. Treatment processes will include cartridge
filtration and nanofiltration in series. Three vertical cartridge filter vessels with 5-
micrometer filters will be provided for particulate removal. Two nanofiltration units will
be provided with a permeate capacity of 2.4 mgd. Source water will be blended with
permeate at a rate up to 20 percent (or 0.6 mgd). Design recovery for the nanofiltration
units is 80 percent. Three 1,050-gpm feed pumps will be provided for boosting water to a
feed pressure of about 110 pounds per squaze inch (psi).
The total capacity of the Castle Hayne treatment train will be 3.0 mgd, which equates to a
raw water feed rate of approximately 3.7 mgd. Treatment processes (in series) will include
oxidation with potassium permanganate, tray aeration, raw water detention, greensand
filtration, cartridge filtration, and nanofiltration. A 300,000-gallon raw water detention
tank will provide 2 hours of contact time for potassium permanganate oxidation. Three
greensand filters will be provided for iron and manganese removal. The filters are sized
based on a filter loading rate of 3.0 gpm/squaze feet. Three vertical cartridge filter
vessels with 5-micrometer filters will be provided for pazticulate removal. Two
nanofiltration units will be provided with a permeate capacity of 2.7 mgd. Source water
will be blended with permeate at a rate up to 10 percent (or 0.3 mgd). Design recovery for
the nanofiltration units is 80 percent. Three 1,050-gpm feed pumps will be provided for
boosting water to a feed pressure of about 110 psi.
Following nanofiltration, permeate from both the Pee Dee and Castle Hayne treatment
trains will be blended and the following chemicals will be added: sodium hypochlorite,
sodium hydroxide, and corrosion inhibitor. Finished water will then be conveyed to a 2.0-
million gallon pre-stressed concrete tank for storage. Three vertical-turbine pumps will be
provided to pump finished mater into the distribution system.
Page 2 of 2
C-WTP 03/05

i ~ t
NPDES PERMIT APPLICATION -SHORT FORM C - WTP
For discharges associated with water treatment plants
8. Describe the wastewater and the treatment process(es) for wastewater generated by the
facility:
The proposed WTP includes a waste treatment system for treatment of backwash waste.
Approximately 0.1 mgd of backwash waste will be generated from backwashing greensand
filters. Backwash waste will be conveyed to a storage tank for clarification. Following a
batch clarification process, clazified water will be decanted and conveyed to the
membrane concentrate dischazge line. Solids will be pumped to the sewer system or will
be stored in a residuals storage tank for off-site disposal vial land application by private
contractor.
9. Number of separate dischazge points: 1
Outfall Identification number(s)
10. Frequency of dischazge: Continuous
If intermittent:
Days per week dischazge occurs: Duration:
11. Plant design potable flowrate 8.0 MGD
Backwash or reject flow 2.0 MGD
,--, -- --, f-- : r, ~",,
r.
.- ~ I ~ ~. ~ , .-..
~ ti y ~
~~,
Intermittent ^
12. Name of receiving stream(s) (Provide a map shouring the exact location of each outfali, including
latitude and longitude):
Atlantic Intracoastal Waterway (see attached map).
13. Please list all water treatment additives, including cleaning chemicals, that have the
potential to be dischazged.
Sodium hypochlorite (for disinfection)
Sodium hydroxide (for pH adjustment)
Corrosion inhibitor (for stabilization)
14. Is this facility located on Indian country? (check one)
Yes ^ No
15. Additional Information:
Provide a schematic of flow through the facility, include flow volumes at all points in
the treatment process, and point of addition of chemicals.
Page 3 of 3 ~ C-W'IP 03/05

rr
NPDES PERMIT APPLICATION -SHORT FORM C - WTP
For discharges associated with water treatment plants
Solids Handling Plan
RECS.{\/~
DC1~~1 VVILfv11.NGT0~~~, '~~~
.., ,_
3". rT'G"~T a~~*~licants
Information needed in addition to items 1-I5:
:"°~ applicants -:~~.~sk cs~ntact the NCDENR Customer Service.,Center.
Was the Customer Service Center contacted? ~ Yes ^ No
Analyses of source water collected
Engineering Alternative Analysis
Dischazges from Ion Exchange and Reverse Osmosis plants shall be evaluated using a
water quality model.
17. Applicant Certification
I certify that I am familiaz with the information contained in the application and that to the
best of any knowledge and belief such information is true, complete, and accurate.
Printed name of Person Signing
Title
Signature of Applicant
Date
North Carolina General Statute 143-215.6 (b)(2) provides that: Any person who knowingly makes any false
statement representation, or certification in any application, record, report, plan, or other document files or
required to be maintained under Article 21 or regulations of the Environmental Management Commission
implementing that Article, or who falsifies, tampers with, or knowingly renders inaccurate any recording or
monitoring device or method required to be operated or maintained under Article 21 or regulations of the
Environmental Management Commission implementing that Article, shall be guilty of a misdemeanor punishable
by a fine not to exceed $25,000, or by imprisonment not to exceed six months, or by both. (18 U.S.C. Section
1001 provides a punishment by a fine of not more than $25,000 or imprisonment not more than 5 years, or both,
for a similar offense.)
?~.,.,> d r `d
C-WTP 03/05

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Solids Handling Plan
The proposed WTP includes a waste treatment system for treatment of backwash waste.
Approximately 0.1 mgd of backwash waste will be generated from backwashing
greensand filters. Backwash waste will be conveyed to a storage tank for clarification.
Following a batch clarification process, clarified water will be decanted and conveyed to
the membrane concentrate discharge line. Solids will be pumped to the sewer system or
will be stored in a residuals storage tank for off-site disposal vial land application by
private contractor.
`~~
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r_
Analysis of Source Water Collected
An updated mass balance and concentrate water quality projection was performed in
order to analyze source water to be collected from both the Pee Dee aquifer and Castle
Hayne aquifer. The "Combined" column lists the expected water quality when 4
membrane units are operating (2 Castle Hayne units and 2 Pee Dee units). If one or more
membrane units are not operating, water quality could be affected since the blending
ratios would be different.
The anticipated flows for the concentrate stream are as follows:
Minimum 0.6 MGD for 6-MGD plant
Average 1.0 MGD for 6-MGD plant
Maximum 1.35 MGD for 6-MGD plant, 2.0 MGD for 9-MGD plant

_.
~~Cn~ WILMING I GN. NC
~~~!_ ~ ? zoos
NEW HANOVER COUNTY WATER TREATMENT PLANT
Mass Balance
Pee Dee Aquifer & Castle Hayne Aquifer
PROJECTED CONCENTRATE Concentrate
Test Parameters Units
Castle Hayne
Pee Dee
Combined
Spec. NPDES
Limits
Acidit m /L ~`NfA 38;70 38.70 _~
Aluminum m /L _ 0.0~ _ ND 0.0
Ammonia Nitro-.~~n m /L 0.26-~ 0.44 0.35
.
--_
Ahtirron
Arsenic -

m~iL
m /L -

N/A
ND

> ND
ND

` ND -
ND

.025
Barium m /L 0.0955 ND 0.0
Be Ilium m /L ND ND ND 0.00006
Boron m /L ND 0.24 0.12
Bromate `, m !L ' N/A _ _ ND ND ,. --
Cadmium m /L ND ND ND 0.0025
Calcium m /L 355.200 280.68 317.94
Chloride m /L 59.280 153.24 106.26
Chromium m /L ND ND ND 0.01
Color pt/co 40.800 34.80 37.80
Cop er m /L ND 0.02 0.01
C snide m /L 0.22 ND 0.1 0.0005
Fluoride m /L ND 0.44 0.22
H dro en Sulfide m /L ND 0.00 0.00
Iron m /L 14.008 0.48 7.24
Lead m /L ND 0.02 0.01 0.0125
Ma nesium m /L 8.457 29.56 19.01
Man anese m /L 0.205 0.10 0.15
Mercu m /L ND ND ND 0.000012
Nickel m /L ND ND ND 0.0042
Nitrate m /L ND 0.40 0.20
Nitrite m /L ND ND ND
pH m /L 6.0-9.0
Ortho-Phosphate
Phosphate tofal~~ m /L
m IL~ ~- 0.1 ~_ _
~~N/A ND
~ND ~ 0.1
- -~ ND<
Phosphorus, dotal
-- - m !L ~ ~ N/A ND - ~;-t~D `. 2 ,

Potassium
m /L
2.361 - --
9.46
5.91
Selenium m /L ND ND ND 0.036
Silica m /L 10.243 34.06 22.15
5iticon m %L~ ~~ N/A 15:93 15.9-
Silver.
Sodium mg/L
m /L NIA
29.111 ND
54.41 ND
41.76
S ecific Conductance umhos/cm 1729.467 1684.133 1706.800
Strontium m /L 0.671 1.09 0.88
Sulfate m /L ND ND ND
Sulfides, Total
Sulfieles,~Dsso(ved
- m /L
m IL ~ -~ ND
~- NIA 0.11
,SID 0.06
.NE? `<
Thallium _ -m /c,~L'; ' NIA ~
-
~ ND ~
- ~ ~~iD ~ -
Zinc - ~ - - - - -mom-- ~- N/A ND ' .Np _~_ ---
Tem erature C _
_
Alkalinity mg/L

r ._
RECEIVED
ACM WILMINGTON, NC
NEW HANOVER COUNTY WATER TREATMENT PLANT `'~'f~ } ~ LuO~
i`11ass Balance
Pee Dee Aquifer & Castle Hayne Aquifer
PROJECTED CONCENTRATE Concentrate
Test Parameters Units
Castle Hayne
Pee Dee
Combined
Spec. NPDES
Limits
Bicarbonate as CaC03 m /L ~Q~'0~~' "' t,7*E} ?`_ m ~~~~ _ '~ ~~'
Carbonate m /L u~i~ ,_~~ ' ,0'2
Carbon Dioxide m /L
Total Hardness CaC03 m /L ~ " ~'~" ~~ ~~~
vT
Total Or anic Carbon m /L 41.040 24.00 32.52
Dis.Or anic Carbon m /L 33.360 17.76 25.56
Dissolved Ox en m /L 0.000 0.000 0.000
Total Dissolved Solids m /L
h. , _
_

Total Sus ended Solids -''
m /L
N/A
3.80 _
` 3.80
30
Tota[Set`iab~e Solids m /L - N/A ND ND 0.2
_
Turbidi ntu UNK UN
K UNK 25
Lan tier Saturation u ?1.6 _
y~.. Y:
_ ~
UNK
SDI UNK UNK UNK
Coliform, Total mL ND ND ND

Colifo~m; Feca!
_.
mL - _-__-
ND
ND
`'ND ;'
-
5ulfide`Gerierafin 'Baeferia -- - -- _ _
N~'A
UNK
~ `UNK
--
HeterotrophicPlate Cwnf~. __ - ~`NTA UNK UNK_
Yeast and.Moi~ ~ "'N/A ~ :ND - ND
Assumptions:
1. Total WTP production = 6.0 MGD
2. 25% bypass (Pee Dee) and 0% bypass (Castle Hayne) to Finished Water
3. 80% Recovery Rate through membrane system.
4. Concentrate Flow Rate = 20% of membrane flow = 1.3 MGD.
5. Finished Water Flow Rate =Bypass + Membrane Permeate = (0.75 + 5.25 = 6.0 MGD).
6. Cmax is the projected influent Concentrations based upon the maximum of the values among the three
tested sites.
7. Blended Cmax is based on Cmax for each aquifer and planned pumping rates for each aquifer
8. Predicted Concentrate concentration is based on equation [C=A+4AR]. R is avg rejection rate for each
constituent for nanofiltration systems
Notes:
N/A =Data Not Available
ND =Below detection limit in Raw Water sample
Raw water lead concentrations are questionable. Results in exceedance of spec NPDES. Presence of lead
should b_e further evaluated.
=Data from one aquifer not available. Finished water and Membrane
Concentrate concentrations based on available data only.
= Data based on projections using manuafcturer's software or from
manufacturer's recommendations

_~
R~C~1VE~
~C~~1 ~~11LMINGTGN. N
Engineering Alternatives Analysis
~U-_ :~ 1 2006

._
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3. Alternatives Analysis
3.1 No Action
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Under the no-action alternative, New Hanover County would continue to operate the existing public
groundwater system in the project area. The County would continue to provide little to no treatment of the
groundwater apart from disinfection with chlorine prior to distribution to customers.
One of the major issues associated with maintaining the existing groundwater system is a poorly managed
groundwater supply due to the irregular spacing of well fields by new development over the last decade.
The Cep my has since acquired and is the sole operator of these developer-built well systems. Based on the
12-hour yield of existing groundwater wells, the existing water supply capacity for the County is estimated
to be approximately 5.9 mgd. With the majority of the wells tapped into the Pee Dee aquifer, the majority
of the current supply is provided by the Pee Dee aquifer (12-hour yield of the Pee Dee wells is
approximately 5.3 mgd). Although the current supply is adequate to meet near-term demand projections
for the project area (refer to Section 2.3), conrinued use of the existing groundwater system will continue to
increase demands on the Pee Dee aquifer.
The second major issue with the no-action alternative is the aesthetic quality of the existing water supply.
The majority of the existing groundwater system provides only disinfection prior to distribution to
customers; the existing v~~ater system does meet primary drinking water standards. Customer dissatisfaction
with the water quality is primarily due to aesthetic concerns, such as hardness, iron, and sulfur. Water
quality complaints are well documented by the County, and the majority of the County's customers have
installed water-sofrening equipment. Several communities not currently served by the County, such as
Bald Eagle Lane and Figure Eight Island, are concerned that deteriorating water quality may be a result of
saltwater intrusion from over-pumping aquifers near the AIWW. These communities have submitted
requests to the County for potable water supply. Treatment of the County's water supply with the existing
randomly spaced well system precludes sustainable long-term treatment, particularly when future
regulatory standards are taken into consideration. Implementing treatment at each well site would be costly
to implement and impossible to manage.
The no-action alternative has been eliminated as an acceptable alternative for several reasons. First.
operation of the existing County well system yields a drinking water quality that is aesthetically
unacceptable to the majority of the County's users. Second, the lack of a centralized well field system will
not allow New Hanover County to provide sustainable and cost-effective water treatment, will not allow
the implementation of protected and managed groundwater resources; and will not meet anticipated growth
needs. The lack of a treated, centralized water supply will cause an increased number of private homes to
install private wells. It is likely that the majority of the individual wells would withdraw from the Pee Dee
aquifer, since water quality in the Pee Dee is better than from the surficial or Castle Hayne aquifers.
Demand on the Pee Dee aquifer would continue to increase. The increased use of individual wells will
ARCA.DIS Project No. NC702018 OG00
3-1

_,
~ ~',.~ Tom-: ~'~

Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
limit the County's ability to manage groundwater resources and will result in excessive drawdown of the
Pee Dee aquifer, potentially deteriorating water quality due to saltwater intrusion for many users.
3.2 Purchase of Raw Water from Lower Cape Fear Water and Sewer Authority (LCFWSA)
The LCFWSA is anon-profit public agency created in 1970 to serve New Hanover, Brunswick, Bladen,
Columbus, and Pender Counties. In 1984, the LCFWSA completed a raw water supply system that
consists of a 45-mgd raw water pump station and intake on the Cape Fear River upstream of Lock and Dam
No. 1, 14 miles of 48-inch transmission main, and a 3 million gallon storage reservoir. In 1992, the
LCF~~'SA extended its service area by extending raw water transmission mains approximately 10 miles.
The raw- water main extension consisted of 60-inch and 48-inch mains ser~~ng the City of Wilmington and
two industries along the US 421 corridor.
The LCFWSA currently provides water to Brunswick County, the City of Wilmington, and two industries
in New Hanover Count}' along the US 421 corridor. In 2001, the LCFWSA supplied an average day
demand of approximately 14 mgd to these communities. The LCFWSA establishes raw water user rates
based upon annual water use, estimated expenses, debt service, and depreciation. The published rate for the
year 2002-2003 is ~0.39~"1,000 gallons of raw water supplied. Due to the projected grow-th in the Lower
Cape Fear area, the potential exists that new or existing customers, such as the City of Wilmington or News
Hanover County, would consider obtaining additional raw water supply by purchasing raw water from the
LCFWSA.
The DWR completed a draft water supply plan for the Cape Fear River Basin ('March 2002) that indicates
additional raw water supply is available to the LCFWSA and the City of Wilmington. The draft water
supply plan evaluated w-nether sufficient raw water supply capacity would be available in the Cape Fear
River to meet projected needs through 2050 without significantly affecting the reliability of the Jordan
Lake low-flow augmentation pool, the ability to meet the flow target at the Lillington stream gage, or
negatively affecting downstream flow in the Cape Fear River_ This analysis did not take into account if a
community had sufficient infrastructure to meet projected demands; but rather analyzed only if the
community had sufficient raw water capacity in the area to meet future water demands. Results from this
analysis indicated that 106.6 mgd of raw water supply is available'to the LCF`~' SA and/or the City of
Wilmington. It was assumed that the available supply to each intake would be one-half of the total
available supply, or approximately 53.3 mgd.
According to the 1997 Local Water Supply Plan (LWSP), LCFWSA sales contracts will exceed 45 mgd
before 2010 based on a peak day demand. These sales contracts do not include additional water supply to
New Hanover County or the City of Wilmington. Table 3-1 provides a summary of the 1997 LWSP data
for the LCFWSA. Additionally, the available LCFWSA water supply is limited by the capacity of the
existing raw water pump station and transmission main. The design capacity of the pump station and raw
water transmission mains is 45 mgd. However, the LCFWSA have found that the peak capacity may be
ARCADIS Project Na. NC702018.0000 3 2

,_
r- ~ ~:. 1 ~i ~ L%
i~~ :~
_...,;. ,
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
less than 45 mgd. An upgrade to the pump station and raw water transmission main will be required once
peak-day demands exceed the peak capacity. Should New Hanover County pursue a sales contract with
'~c"~'vT~'SA and ~~ infrast~.rcture upgrade project be approved. the capital cost of New Hanover County's
component of the LCF«"SA infrastructure upgrade project is estimated at approximately $8 million.
Other capital costs would be required if the County were to purchase raw water from the LCFWSA in
addition to the LCFWSA upgrade project. An additional 8 miles of 24-inch raw water transmission main
would be required to serve the New Hanover County project area at a capital cost of approximately
$6 million. (This cost excludes mitigation for environmental impacts). The existing LCFWS transmission
main near the City of Wilmington would be tapped and the new transmission main extended over to a
central location in the project area. Several sensitive en~~ironmental areas would need to be disturbed to
construct this new transmission main. New Hanover County would also need to construct a new surface
water treatment facility for treatment prior to distribution at a capital cost of approximately $24 million.
The total project capital cost for this altemative is projected to be $38 million. This figure includes the
County's portion of the LCFWSA upgrade project-
Table 3-1: Summary of Projected Sales
Contracts for LCFWSA
Sales Contracts''"3
Year (m;d)
1997 40.65
2000 4.65
2010 50.65
2020 50.65
~ Information presented in the 1997 Local Water Supply
Plan.
Z Capacity of raw water transmission system is
approximately 45 mgd.
3 Sales contracts are peak day demand.
Furthermore, New Hanover County Commissioners have historically been concerned with surface water
vulnerability issues. The Lower Cape Fear Coastal Counties are located downstream of several hog farms,
agricultural centers, and industrial dischargers. The County Commissioners have clearly stated that an
independent and reliable water supply is a preferred water supply alternative.
Therefore, this alternative has been eliminated from consideration for several reasons. The LCFWSA does
not currently have adequate raw water supply or infrastructure capacity to meet the projected peak day
needs of the project area even though there is potential raw water supply available in the Cape Fear River.
The combined cost of a new surface water treatment facility and improvements to the raw water
infrastructure system renders this alternative less economically favorable than aCounty-owned
ARCADIS Prom-- ' _ , ~ .. _ _ i; GC00
3-3

r- '~
[:~~,-,~-.iii
_ ., -, ~ ,
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
groundwater treatment plant. In addition, the time required to attain additional raw water supply allocation
will impact the ability of the County to provide high quality drinking water to existing customers and will
likely result in a delay in the ability to meet planned near and long-term water supply needs.
3.3 Purchase Finished Water from Surrounding Counties
Several other water service providers serve the counties surrounding New Hanover. Under this alternative,
New Hanover County would purchase finished water from one or more surrounding counties. Water
service pro`~ders considered in this alternative include Brunswick and Pender Counties. These alternatives
are discussed in the following sections.
3.3.1 Brunswick County
Brunswick County owns and operates two water treatment facilities for a total capacity of 30 mgd. The
first facility is a 24-mgd surface water treatment plant treating raw water purchased from the LCFWSA,
and the second facility is a 6-mgd plant treating groundwater withdrawn from the Castle Hayne aquifer.
According to the 1997 LWSP, Brunswick County has a total raw water supply of 27.4 mgd, which includes
a contract to purchase up to 24 mgd of water from LCFWSA and a 12-hour yield of 3.4 mgd from the
Brunswick County well system.
Brunswick County provides finished water to residential, commercial, and industrial customers located in
Brunswick County. Brunswick County also sells finished water to several local municipalities, including
Carolina Shores, Caswell Beach, Holden Beach, Long Beach, North Brunswick Sanitary Distract, Ocean
Isle Beach, Shallotte, Southport, Sunset Beach, and Yaupon Beach. According to the 1997 LWSP,
Brunswick County has a sales contract totaling 6 mgd and sold approximately 3 mgd of finished water to
these other municipalities.
Water demand forecasts reported in the Brunswick County 1997 LWSP are summarized in Table 3-2. Peak
service area demands were calculated based on a 1997 peaking factor of 1.5. The reported 1997 annual
average and peak day demands were 13.7 and 21 mgd, respectively. The 1997 LWSP indicates that
Brunswick County's peak day demands will exceed the treatment capacity of 30 mgd prior to 2010. The
1997 LWSP indicates that Brunswick County will be investigating a surface water treatment plant
expansion from 25 to 36 mgd- Furthermore, the County's raw water supply is currently limited by the
12-hour yield of the existing groundwater wells and the sales contract with LCFWSA.
ARCADIS Project No. NC702018.0000
3-4

Table 3-2: Water Demand Projections for Brunswick County
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Average Service Peak Service Sales Total Average Total Peak
Area Day Demand Area Demand' Contracts Day Demand DemandZ
Year (mgd) (mgd) (mgd) (mgd) (mgd)
1997' 11.3 17.0 6.0 17.3 23
0
2000 12.1 18.2 7.1 19.2 .
25.3
2010 15.1 22.7 9.0 24.1 31
7
2020 18.2 27.3 10.6 28.8 .
37.9
t Average service area demand, sales, contracts, and total average daily demand reported in 1997 LWSP for
Bnmswick County.
'Peak service area demand calculated based on reported average service area daily demand and 199 7 peaking
factor of 1.~.
3 The total peak day demand was calculated as the sum of the peak day service area demand and outstandi

sales contracts. ng
This altemative has been removed from consideration based on the aforementioned analysis. Brunswick
County does not have sufficient treatment capacity or the raw water supply to meet the needs of the 1`Tew
Hanover County project area. This alternative would require that BrunswZCk County obtain additional raw
water supply capacity and upgrade WTP capacity. Additionally, this analysis does not take into
consideration any improvements to the LCFtiVSA raw water infrastructure system or any costs associated
with the environmental impact of constructing a new finished water transmission main from Brunswick
County to New Hanover County.
3.,;.2 Pender Counh~
Pender County has several small water systems, including Burgaw, Rocky Point -Topsail Water Sewer
District, Surf City, and Topsail Beach. All of these systems rely primarily on groundwater for water
supply. Each of these systems reports a total raw water supply of less than 1 mgd. None of these systems
has water treatment facilities, with the exception of Surf City, which has a 12-mgd groundwater treatment
plant. Based on the limited available resources; purchase of raw or treated water from Pender County has
been eliminated as a viable option.
3.4 Purchase Finished Water from City of Wilmington
New Hanover County has evaluated the possibility of purchasing finished water from the City of
Wilmington. Wilmington owns and operates the 25.9-mgd Sweeney WTP. The City of Wilmington treats
up to 15 mgd of raw water from the Cape Fear River pumped from the City-owned Kings Bluff Pump
Station via 25 miles of 30-inch raw water transmission main. Wilmington also has a 15-mgd raw water
purchase contract with the LCFWSA, pumped ~za the LCFWSA-owned pump station. Thus, the City's
total surface water supply is 30 mgd.
ARCAOIS Project No. NC702018.0000
3-5

~r-¢.'`~-~`' Iii"~
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Final Environmental
'' ~` .f s '`'~~`~ Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
The City of Wilmington has acquired several groundwater well and distribution systems from surrounding
utilities since the submittal of the 1997 LWSP. In 1999, the City of Wilmington purchased a groundwater
system from private utility companies, Cape Fear Utilities Inc. and Quality Water Supplies Inc. The
private utility companies served a large area south and east of the city limits as well as the Shearin Hills
area. The private utility companies owned and operated 23 wells withdrawing water from the Pee Dee
aquifer with a combined 12-hour pumping capacity of 5 mgd. The City has decommissioned the
groundwater system and con~~erted all customers over to the surface water system. Thirteen of these wells,
with a combined 12-hour pumping capacity of 3.2 mgd, were decommissioned between March and
December of 2000. The remaining 10 wells were decommissioned in January 2004 and had a combined
12-hour pumping capacity of 1.8 mgd. The City currently maintains 4 of the 23 wells on active status for
emergency use only. The remaining 19 wells are listed as inactive (dormant) with the DEH and must go
through approval and testing prior to re-activation.
The final decommissioning ofthe groundwater system in January 2004 has increased water demands at the
Sweeney WTP. As a result, the Sweeney WTP experiences peak day demands close to its current rated
capacity of 25.9 mgd. In 2004, the Sweeney WTP reported a peak day demand of almost 24 mgd.
However, the 1997 Lu'SP projected peak-day demands to reach 19.4 mgd in 2000 and 21.3 mgd in 2010.
Based on this trend, it is likely that the City of Wilmington's peak day demand will exceed current
treatment capacity prior to 2010.
In addition to exceeding treatment plant capacity, the water demand projections also indicate that the peak
day demand may exceed the City's raw surface water supply of 30 mgd by 2020, particularly if the City
were to provide finished water to the project area. The City's raw water supply is limited by the capacity of
.the 1 ~-mgd Kings Bluff Pump Station and the existing 15-mgd raw water contract with the LCF`VSA. The
2002 Cape Fear River Basin Water Supply Plan indicates that the City of Wilmington may increase its raw
water supply capacity up to X3.3 mgd. However, the Kings Bluff Pump Station would need to be upgraded
to accommodate a higher design flow, and the raw water transmission main would require 25 miles of
parallel line.
The City is in the process of conducting a water system master plan to identify short-term improvements to
address existing demands associated with decommissioning the groundwater system as well as plans to
address long-term water supply needs.
Based on the above evaluation, the City of Wilmington does not currently have adequate water supply or
treatment capacity to accommodate near-term water supply needs of the northern section of New Hanover
County. Although the City is evaluating short-term improvements, these improvements w i11 only
accommodate existing demands associated with decommissioning the groundwater system.
The ability of the City of Wilmington to serve New Hanover County in the future is also uncertain.
Significant capital improvements will be required for increased water treatment capacity, increased finished
ARCADIS Project No. NC702018.0000
3-R

~r~Jl ~ ~.;;;~~~j{~,1~ ; `~t,i i~C, Final Environmental
Assessment for
' "" ~' " 7:"'=' New Hanover County
.> _ , ~_.
WTP and Well Field
Alternatives Analysis
water pumping and storage capacity, and increased raw water supply intake capacity. It is estimated that
the New Hanover County's portion of the City of Wilmington's treatment plant and finished water
pumping upgrade capital costs would be approximately $21 million based on a County demand of 6 mgd.
Additionally, the County's portion of the raw water infrastructure upgrade would be approximately
$15 million. The total project cost is estimated at $36 million.
The issue of surface water vulnerability should also be taken into consideration for this alternative. An
expansion of the existing Cape Fear River water supply source will not provide an independent and reliable
water supply source to the residents of New Hanover County.
In summary, this alternative has been removed from consideration for several reasons. The City of
Wilmington has inadequate treatment plant capacity to meet near-term water supply demands in the project
area with decommissioning of the groundwater system. Second, the ability of Wilmington to serve long-
term water supply demands in the project area is uncertain. The City of Wilmington will need to expand its
existing facility and attain additional raw water supply capacity before 2010, and a large portion of this cost
would be passed on to New Hanover County customers.
3.5 County-Owned Surface Water Treatment Plant and Raw Water Intake
A County-owned surface WTP and raw water intake alternative explores the possibility of New Hanover
County obtaining a surface water supply source and constructing a surface water treatment plant. Results
from the i;ape Fear Rive- °as_n Water Supply Plan indicate that 106.6 mgd of raw water supply is
available in the Lower +~~!pe Fear area. Currently, the City of Wilmington and the LCFWSA have raw
water intakes in the Lower Cape Fear River with capacities of l~ and 45 mgd, respectively. Therefore,
excess water supply capacity should be available in the Lower Cape Fear to accommodate New Hanover
County needs.
This alternative would require that ivTew Hanover County build a water intake structure and raw water
transmission system to transmit raw water from the Cape Fear River to New Hanover County. To reduce
the potential for withdrawing brackish water, raw water would need to be obtained upstream of US Lock
and Dam No. 1. The raw water transmission main would likely follow the raw water transmission
easements for the LCFWSA and Wilmington's Kings Bluff Pump Station. It is estimated that
approximately 32 miles of 24-inch raw water transmission line would be required for an ultimate WTP
capacity of 8 mgd. It is estimated that the capital construction cost of this raw water transmission system
would be approximately .~26 million.
The County does not own a treatment facility; therefore, this alternative would require the County to build
_ "and operate a surface water treatment facility to treat Cape Fear River water. The cost for a surface water
treatment plant is expected to be much higher than the cost for a groundwater treatment facility. Water
from the Cape Fear River is of poorer quality than water from the Pee Dee or the Castle Havne aquifers.
ARCADIS Proie~t No. NC702018.0000 3-7

Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Also, water quality in the Cape Fear River varies seasonally with storm events. Groundwater quality is
expected to be more stable. The capital construction cost of a new 6-mgd surface water treatment facility
was estimated to be approximately $24 million. Therefore, the total capital construction cost for this
alternative is estimated at $50 million.
This alternative is considered cost-prohibitive and, therefore, has been eliminated as a viable option.
Additionally, this alternative does not take into account the surface water vulnerability issue that is
important to New Hanover County. Additionally, this altemative does not take advantage of existing raw
water transmission structures, such as the LCFWSA raw water transmission system, or share the cost ~.vith
implementing a new transmission system with other users. Also, the en~nronmental issues. associated with
a new transmission main are not fully evaluated and quantified in this discussion.
3.6 New County-owned Membrane Softening Water Treatment Plant and Well Field -Selected Alternative
New Hanover County has selected the County-owned membrane softening treatment plant and well field
system alternative as the future treatment method and reliable, protected, water supply source for the
County. This alternative does not dramatically change the way the current public water supply system is
m~anag~d and operated, with the exception of a method of treatment to produce high quality drinking water,
a centralized and managed well field system, and balancing withdrawals from the Pee Dee aquifer with
water supplied from the Castle Hayne aquifer. This altemative would replace ~.9 mgd of existing County
well system capacity. The rise of consumer complaints and hence the demand for high quality drinking
water has significantly paved the way for the implementation of this project.
`?~:,~ total present worth analysis of the proposed project is provided in Table 3-3. The capital construcrion
cost and the total project cost (including engineering, legal, and administration costs) for the proposed
project is X24 million and $27 million, respectively. The total project cost is less than the capital
construction cost of the other considered alternatives.
There are also several intangible benefits of the proposed project to New Hanover County in addition to
providing a high quality drinking water to County customers. First; the new well field system will replace
the existing well field system and will provide an avenue for the County to effectively manage and protect
groundwater resources. The proposed well field location will move groundwater extractions away from
sensitive coastal areas, thereby minimizing the potential for saltwater intrusion. Second, the proposed
project pro~zdes an independent and protected water supply system.
The proposed project also has the potential benefit of reducing long-term withdrawal from the Pee Dee
aquifer. New Hanover County currently obtains nearly all of it water supply from the Pee Dee aquifer.
Based on 2003 and 2004 demand data, approximately 90 percent of the County's existing demand is met by
water supplied from the Pee Dee aquifer. Average 2004 demand for the Pee Dee aquifer was 2.35 mgd.
- -_ _. >~~~ozois.oooo 3-8

r t....: ~: ~ ~e~ ~-. a-'~
-,; , , _
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
The proposed project includes construction of a 6-mgd WTP where approximately 50 percent of the raw
water supply would be supplied from the Pee Dee aquifer and ~0 percent of the raw water supply would be
supplied from the Castle Hayne aquifer. With a planned membrane recovery rate of 80 percent, a
maximum of 7.3 mgd of raw water would be required to meet a finished water capacity of 6 mgd. Due to
the different treatment requirements for each of these raw water sources; separate treatment systems will
need to be provided for the Castle Hay~ne and Pee Dee aquifers. At peak production, approximately
3.7 mgd of raw water must be pumped from each well system to produce a 3-mgd supply of finished water
from each treatment system.
Since maximum day demands occur only for a short period during the year, the use of the two treatment
systems and their respective well fields throughout the year could be managed such that the average annual
withdrawal from that Pee Dee aquifer during the peak production year does not exceed the current average
annual withdrawal from that aquifer. For example, maximum utilization of the total plant capacity is
expected to occur during a year when the average daily demand is 4 mgd and the maximum daily demand
is 6 mgd. During this same year, an average of 2 mgd of finished water could be supplied by the Castle
Hayne aquifer, while an average of 2 mgd of fmished water could be supplied from the Pee Dee aquifer. Ln
this case; the average withdrawal from the Pee Dee dutZng a year when the plant is at full production could
be linuted to the County's c~.n~rent average withdrawal from the Pee Dee aquifer.
New Hanover County intends to continue working with the City of «'ilmington to plan the year 200 water
supply needs. The County is also exploring the possibility of an interconnect with Wilmington for
emergency backup. Additionally, the County intends to explore the possibility of maintaining a fey=:
existing County wells for emergency backup and/or monitoring. T'ne County will work with DEH to
develop a protocol for this scenario.
The following subsections provide descriptions of the proposed water treatment facility, well field, ra~.v
water transmission main, finished ~z~ater transmission main, and concentrate disposal line.
ARCP.~IS Project No. NC702018.0000 3_9

~-.--- \ I ~.~~
i; -t s'~''r-
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Table 3-3: Present Worth Analysis for Proposed New Hanover Water Treatment Facility
County and Well Field System
Salvage Value
Component Capital Cost Salvage Amount Useful life {yrs)
Site work $472,000 $0 20
Yard Piping $472,000 $0 20
Membrane Treatment -Pee Dee $2,093,000 $0 20
Membrane Treatment -Castle Hayate $2,448,000
Greensand Filters -Castle Hayne $2,180,000
Finished Water and Waste Pumping $618,000 $0 20
Finished Water Storage $59,000 $0 20
Chemical Systems $321,000 $0 20
Instrumentation & Control $83,000 $0 20
Electrical $1,678,000 $0 20
Burldrngs $1,780,000 $0 20
Discharge Concentrate force Main $1,249,000 $0 20
Pee Dee Wells (14 Wells) $2,65,000 $0 20
Pee Dee Raw Water Line 51,089,000 $0
20
Castle Hayne We11s (16 Wells) $2,845,000
Castle Hayne Raw Water Lines $723,000
Finished Water Line $243,000 $0 20
Easement Acquisition $11,000 $151,000 Indefinite
Land Cost for ~VTP $20,000 $250,000 Indefinite
Land Cost for Well Sites $160,000 $160,000 Indefinite
Wetlands Mirigation $280,000 N/A N/A
SUBTOTAL $23;905,000 $561,000 (*)
Present W' ortn Present vv ~i ui vi
Ca ital Cost O&M Cost of O&M Salvage
$23,905,000 $1,766,000 $15,120,000 $177,000
Total Present North for New Hanover $38,8$0,000
County ~VTP and Well Field:
Tune Period = 15 years; Interest Rate = 8 percent
Note: Operation and Maintenance (O&.M) present worth cost includes the water treatment facility; well
field system, and raw and finished water systems.
3-10
~,,, ~ ~.-~~ _o ~ e.oooo

.~
%.
Final Environmental
'~'~ -' Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
3.6.1 Design Criteria for Proposed Water Treatment Facility
The proposed New Hanover County WTP is a 6-mgd groundwater treatment facility that will treat water
from the Pee Dee and Castle Hayne aquifers. The primary treatment process will be nanofiltraiion for
softening total organic carbon (TOC) removal and color removal_ Separate membrane filtration units will
be provided for the two source waters to alleviate the potential for membrane fouling from biological
growth or saturated salts. In addition, raw water from the Castle Hayne has high iron levels and requires
pre-treatment prior to membrane filtration.
Figure 3-1 provides the location of the proposed WTP, well field, and related infrastructure. A process
flow diagram and site plan of the proposed treatment system is illustrated on Figures 3-2 and 3-3,
respectively. The proposed WTP will initially be constructed for 6 mgd with future capability for 7.5 mgd.
The following subsections describe the proposed unit processes.
3.6.1.1 Pee Dee Treatment Train
The total capacity of the Pee Dee treatment train will be 3.0 mgd, which equates to a raw water feed rate of
approximately 3.6 mgd. Treatment processes will include cartridge filtration and nanofiltration in series.
Three vertical cartridge filter vessels with 5-micrometer (µm) filters will be provided for particulate
removal_ Two nanofiltration units will be pro~~ded with a permeate capacity of2.4 mgd. Source water will
be blended with permeate at a rate up to 20 percent (or 0.6 mgd). Design recovery for the nanofiltration
units is 80 percent. Three 1,050-gpm feed pumps will be provided for boosting water to a feed pressure of
about 110 pounds per square inch (psi).
3.6.1.2 Castle Hayne Treatment Train
The total capacity of the Castle Hayne treatment train will be 3.0 mgd, which equates to a raw water feed
rate of approximately 3.7 mgd. Treatment processes (in series) will include oxidation with potassium
permanganate, tray aeration, raw water detention, greensand filtration, cartridge filtration, and
nanofiltration. A 300,000-gallon raw water detention tank will provide 2 hotus of contact time for
potassium permanganate oxidation. Three greensand filters will be provided for iron and manganese
removal. The filters are sized based on a filter loading rate of 3.0 gpm/square feet. Three vertical cartridge
filter vessels with 5-µm filters will be pro~~ided for particulate removal. Two nanofiltration units will be
provided with a permeate capacity of Z.7 mgd. Source water will be blended with permeate at a rate up to
10 percent (or 0.3 mgd). Design recovery for the nanofiltration units is 80 percent. Three 1,050-gpm feed
pumps will be provided for boosting water to a feed pressure of about 110 psi.
ARCADIS Project No. NC702018.0000 3_11

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3.6.1.3 Post Treatment
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Following nanofiltration, permeate from both the Pee Dee and Castle Hayne treatment trains will be
blended and the following chemicals will be added:
• Sodium hypochlorite (for disinfection)
• Sodium hydroxide (for pH adjustment)
Corrosion inhibitor (for stabilization)
Finished water will then be conveyed to a 2.0-million gallon pre-stressed concrete tank for storage. Three
vertical-turbine pumps will be pro~~ided to pump finished water into the distribution system.
3.6.1.4 Backwash Waste Treatment System
The proposed WTP includes a waste treatment system for treatment of backwash waste. Approximately
0.1 mgd of backwash waste will be generated from backwashing greensand filters. Backwash waste will be
conveyed to a storage tank for clarification. Following a batch clarification process, clarified water «ill be
decanted and conveyed to the membrane concentrate discharge line. Solids will be pumped to the sewer
system or will be stored in a residuals storage tank for off-site disposal via land application by private
contractor.
3.6.2 Design Criteria for Proposed Well Fields
A conceptual well-field layout was developed in the 2001 Concept Design report based on results from the
water quality analyses, a 1996 hydrogeolog7c evaluation conducted by Edwin Andrews and Associates, and
pumping tests. Approximately half of the raw water supplied to the 6-mgd WTP will be provided by the
Pee Dee aquifer, while the other half will be provided by the Castle Hayne aquifer. A total 12-hour raw
water supply capacity of 7.3 mgd will be required for the 6-mgd WTP. The required 12-hour raw water
supply capacity was calculated based on a maximum day finished water capacity of 6 mgd assuming an
80 percent recovery rate in the proposed groundwater treatment plant, a 20 percent blending rate for the Pee
Dee aquifer, and a 10 percent blending rate for the Castle Hayne aquifer.
A series of wells will be installed to supply raw water to the WTP. In the 2001 Concept Design Report, it
was projected that each well should be capable of producing water.at a rate of 350 gpm. DENR limits
pumping time at peak day demand to a 12-hour period, so each well could produce water at a maximum
rate of 252,000 gpd (175 gpm). The 2001 Concept Design Report indicates that the wells should be spaced
between 800 and 1,600 feet apart, but indicates that alternate or sequencing operations maybe needed to
prevent excessive drawdown at a well spacing of less than 1,600 feet.
Approximately 16 well sites are proposed for the 6-mgd WTP. Both the Castle Hayne and Pee Dee
aquifers will be tapped at each well site. Therefore, the 6-mgd WTP will have approximately 32 wells.

~ "f
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Two of the new well sites have been permitted and constructed at the proposed `VTP site. The additional
well sites are proposed to be located as shown in Figure 3-l. Four of the well sites will be located along an
unpaved road rc~ ~he~st of the plant site. An additional ten well sites will be located along Plantation Road.
As the County has not yet acquired the land for the proposed well sites, final placement of the well sites
may vary slightly from the proposed placement shown in Figure 3-1. Figure 3-~ illustrates a site plan for a
typical well site.
3.6.3 Design Criteria `or Proposed Raw and Finished Transmission Mains
Two parallel raw water transmission mains will be constructed to transmit raw water from the well sites to
the WTP: One main wZll transmit water pumped from the Castle Hayne aquifer, wMle the other main will
transmit water pumped from the Pee Dee aquifer. Each raw water transmission main will consist of
approximately 17,000 feet (3.2 miles) of line ranging in size from 6-inch to 30-inch. Thus, a total of
34,000 feet (6.4 miles) of raw water transmission will be constructed as part of this project. Both raw water
transmission lines will be located mainly within existing dirt roads in the well field.
Approximately 200 feet of 16-inch finished water line will be installed to transmit finished water from the
WTP to an existing 16-inch line that runs along the south property line.
3.7 Proposed NPDES Discharge
The primary by-product of the membrane softening plant will be a membrane reject stream, which «~Il
consist of concentrated groundwater. In addition, a small waste flow (less than 100,000 gpd) will be
generated from backwashing pressure filters. The total concentrate discharge will have a maximum daily
flow of approximately 2 mgd. An estimate of the membrane concentrate water quality is presented in
Table 3-5.
As part of this EA, the County is seeking an NPDES permit for the discharge of the membrane concentrate
stream to the AIWW. The following section presents results from an evaluation ofnon-discharge
alternatives, describes the proposed NPDES discharge, and outlines dilution modeling that will be
performed to demonstrate compliance with the proposed limits for this discharge.

100' RADIUS
WETLAND AREA ~ ~'\ OF PROTECTION
REMAINING PROPOSED FOR WELL
UNDISTURBED GENERATOR
PROPOSED
11'x17'
WELL HOUSE
/'- _ ~ ~` \
FUTURE WELL (TYP.) / ;:'~ I \ PROPOSED
I ~' - LIMIT OF FILL
POTENTIAL FUTURE < ~
LIMIT OF IMPACT \ \ - - /
\ Gft A VEIL:
~ I ~` _: :.;:_'_ ~:.' ` J / / APPROXIMATE LIMIT OF WETLAND
\ J ~_~ _ .,,~: L _ IMPACT FROM ROADSIDE DITCH
WETLAND AREA\ -
IMPACTED BY GRAVEL
_ ROADSIDE DITCH \ ~ ACCESS 75'
EXISTING R/W ~-~:~ .~' DRIVE
- ~ APPROX. 15' - - -
60' ..EXISTING ~DiRT ROAD`:...._ _,: -_ . ::. ~ .- - - ~ ~ .:: ..: ,
EXISTING R/W _ _ _ _ _ ~ - -
EXIS1lNG ROADSIDE DITCH -y
(APPROXIMATELY 1.5' DEEP) _
MOST CONSERVATIVE AREA = 0.09 ACRES ~~' ' ~ ~'-
OF PROPOSED WETLAND
IMPACT PER WELL SITE
MOST CONSERVATIVE AREA = 0.09 ACRES
OF FUTURE WETLAND IMPACT
PER WELL SITE
TOTAL AREA OF WETLAND = 0.18 ACRES
IMPACT PER WELL SITE
~~ ~ I\~ V i V N9LMINGTON, ENCS 8401
community !nirostructure conswtaMS [phone]
FIGURE 3-4: TYPICAL WELL SITE
I NEW HANOVER COUNTY WATER & SEWER DISTRICT
tr-vaCa J.~c ^„r.a ' L _^? ~ ~ i C I C ! r, .4 n i n u ~ ~ ~ r n +. ~ ~ ~. . ~ . . _

,-.,~ a,,~l;,,~~ ~ ,;,_; ~;"~ Final Environmental
' ~ Assessment for
,;~ New Hanover County
WTP and Well Field
Alternatives Analysis
3.7.1 Evaluation of Alternatives to Surface Discharge
DWQ requires that alternatives to a surface water discharge be evaluated to ensure that surface water
discharge is the most environmentally sound of economically feasible alternatives. The following section
presents results from a concentrate disposal alternatives evaluation. Two potential alternatives to surface
water disposal for the proposed project include reuse opportunities via land application and discharge to an
existing wastewater treatment facility.
Table 3-4: Estimated Membrane Concentrate Water Quality'
Parameter Estimated Concentrate Concentration ~~--
rotas Utssolved Solids (TDS) 1,100 mg,%L
Total Hardness 1,000 mg1L as CaCO;
Turbidity 20 NTU
Total Organic Carbon (TOC) 30 m~'L
pH 7.6
Residual Chlorine iron-Detect
Calcium
355 mg%L
Chloride 400 mg!L
Magnesium `~ ,
mg, L
Sodium 68 mg/L
Suifa~e Non-Detect
1.5 m2~L
Nina~e-Nitrogen < 1 riQ%L
Total Phosphorus`
Non-Detect
Arsenic Non-Detect
Beryllium Non-Detect
Cadmium Non-Detect
Chromium Non-Detect
Copper 0.01 mg/L
Cyanide 0.1 ma,iL
Lead
0.01 m~/L
Meccury Non-Detect
Nickel Non-Detect
Selenium Non-Detect
Silver Non-Detect
Zinc Non-Detect
Based on mass balance conducted for 6-mgd WTP assuming approximately 50 percent of raw
water supplied from Pee Dee aquifer and 50 percent of raw water supplied from Castle Hayne
aquifer. Mass balance assumes 80 percent membrane recovery with 20 percent bypass for Pee
Dee membrane system and no bypass for Castle Hayne membrane system.
ZData from Castle Hayne aquifer not available. Membrane concentrate concentrations based on
Pee Dee data.

r ~C~1 JEJ
DC~,7 ;~~~1±_nnINGTO^•~. NC
JU!. ~ i 2C0~
3. Alternatives Analysis
3.9 No Action
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Under the no-action alternative, New Hanover County would continue to operate the existing public
groundwater system in the project area. The County would continue to provide little to no treatment of the
groundwater apart from disinfection with chlorine prior to distribution to customers.
Cme of the major issues associated with maintaining the existing groundwater system is a poorly managed
groundwater supply due to the irregular spacing of well fields by new development over the last decade.
The County has since acquired and is the sole operator of these developer-built well systems. Based on the
12-hour yield of existing groundwater wells, the existing water supply capacity for the County is estimated
to be approximately 5.9 mgd. With the majority of the wells tapped into the Pee Dee aquifer, the majority
of the current supply is provided by the Pee Dee aquifer (12-hour yield of the Pee Dee wells is
approximately 5.3 mgd). Although the current supply is adequate to meet near-term demand projections
for the project area (refer to Section 2.3), continued use of the existing groundwater system will continue to
increase demands on the Pee Dee aquifer.
The second major issue with the no-action alternative is the aesthetic quality of the existing water supply.
The majority of the existing groundwater system provides only disinfection prior to distribution to
customers; the existing water system does meet primary drinking water standards. Customer dissatisfaction
with the water quality is primarily due to aesthetic concerns, such as hardness, iron, and sulfur. Water
quality complaints are well documented by the County, and the majority of the County's customers have
installed water-softening equipment. Several communities not currently served by the County, such as
Bald Eagle Lane and Figure Eight Lsland, are concerned that deteriorating water quality may be a result of
saltwater intrusion from over-pumping aquifers near the AIWW. These communities have submitted
requests to the County for potable water supply. Treatment of the County's water supply with the existing
randomly spaced well system precludes sustainable long-term treatment, particularly when future
regulatory standards are taken into consideration. Implementing treatment at each well site would be costly
to implement and impossible to manage.
The no-action alternative has been eliminated as an acceptable alternative for several reasons. First,
operation of the existing County well system yields a drinking water quality that is aesthetically
unacceptable to the majority of the County's users. Second, the lack of a centralized well field system will
not allow New Hanover County to provide sustainable and cost-effective water treatment, will not allow
the implementation of protected and managed groundwater resources, and will not meet anticipated growth
needs. The lack of a treated, centralized water supply will cause an increased number of private homes to
install private wells. It is likely that the majority of the individual wells would withdraw from the Pee Dee
aquifer, since water quality in the Pee Dee is better than from the surficial or Castle Hayne aquifers.
Demand on the Pee Dee aquifer would continue to increase. The increased use of individual wells will
ARCADIS Project No. NC702018.0000
~~

~= U ~ ~ V E ~ Final Environmental
~~~~~~:` `~`~'~_~:~11~~1~' a 0+~. ~~~~ Assessment for
New Hanover County
~'%~~- ~ '~~~~~ WTP and Well Field
Alternatives Analysis
limit the County's ability to manage groundwater resources and will result in excessive drawdown of the
Pee Dee aquifer, potentially deteriorating water quality due to saltwater intrusion for many users.
3.2 Purchase of Raw Water from Lower Cape Fear Water and Sewer Authority (LCFWSA)
The LCFWSA is anon-profit public agency created in 1970 to serve New Hanover, Brunswick, Bladen,
Columbus, and Pender Counties. In 1984, the LCFWSA completed a raw water supply system that
consists of a 45-mgd raw water pump station and intake on the Cape Fear River upstream of Lock and Dam
No. 1, 14 miles of 48-inch transmission main, and a 3 million gallon storage reservoir. In 1992, the
LCFWSA extended its service area by extending raw water transmission mains approximately 10 miles.
The raw water main extension consisted of 60-inch and 48-inch mains serving the City of Wilmington and
two industries along the US 421 corridor.
The LCFWSA currently provides water to Brunswick County, the City of Wilmington, and two industries
in New Hanover County along the US 421 corridor. In 2001, the LCFWSA supplied an average day
demand of approximately 14 mgd to these communities. The LCFWSA establishes raw water user rates
based upon annual water use, estimated expenses, debt service, and depreciation. The published rate for the
year 2002-2003 is $0.39/1,000 gallons of raw water supplied. Due to the projected growth in the Lower
Cape Fear area, the potential exists that new or existing customers, such as the City of Wilmington or New
Hanover County, would consider obtaining additional raw water supply by purchasing raw water from the
LCFWSA.
The DWR completed a draft water supply plan for the Cape Fear River Basin (March 2002) that indicates
additional raw water supply is available to the LCFWSA and the City of Wilmington. The draft water
supply plan evaluated whether sufficient raw water supply capacity would be available in the Cape Fear
River to meet projected needs through 2050 without significantly affecting the reliability of the Jordan
Lake low-flow augmentation pool, the ability to meet the flow target at the Lillington stream gage, .or
negatively affecting downstream flow in the Cape Fear River. This analysis did not take into account if a
community had sufficient infrastructure to meet projected demands, but rather analyzed only if the
community had sufficient raw water capacity in the area to meet future water demands. Results from this
analysis indicated that 106.6 mgd of raw water supply is available to the LCFWSA and/or the City of
Wilmington. It was assumed that the available supply to each intake would be one-half of the total
available supply, or approximately 53.3 mgd.
According to the 1997 Local Water Supply Plan (LWSP), LCFWSA sales contracts will exceed 45 mgd
before 2010 based on a peak day demand. These sales contracts do not include additional water supply to
New Hanover County or the City of Wilmington. Table 3-.1 provides a summary of the 1997 LWSP data
for the LCFWSA. Additionally, the available LCFWSA water supply is limited by the capacity of the
existing raw water pump station and transmission main. The design capacity of the pump station and raw
water transmission mains is 45 mgd. However, the LCFWSA have found that the peak capacity maybe
ARCADIS Project No. NC702018.0000 3-2

R~c~~v~c
OCi`n ~.,~~u ,~~1,1~1G?CAN. NC

Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
less than 45 mgd. An upgrade to the pump station and raw water transmission main will be required once
peak-day demands exceed the peak capacity. Should New Hanover County pursue a sales contract with
LCFWSA and an infrastructure upgrade project be approved, the capital cost of New Hanover County's
component of the LCFWSA infrastructure upgrade project is estimated at approximately $8 million.
Other capital costs would be required if the County were to purchase raw water from the LCFWSA in
addition to the LCFWSA upgrade project. An additional 8 miles of 24-inch raw water transmission main
would be required to serve the New Hanover County project area at a capital cost of approximately
$6 million. (This cost excludes mitigation for environmental impacts). The existing LCFWS transnssion
main near the City of Wilmington would be tapped and the new transmission main extended over to a
central location in the project area. Several sensitive environmental areas would need to be disturbed to
construct this new transmission main. New Hanover County would also need to construct a new surface
water treatment facility for treatment prior to distribution at a capital cost of approximately $24 million.
The total project capital cost for this altemative is projected to be $38 million. This figure includes the
County's portion of the LCFWSA upgrade project.
Table 3-1: Summary of Projected Sales
Contracts for LCFWSA
Sales Contracts'' ~' 3
Year (mgd)
1997 40.65
2000 45.65
~ 2010 50.65
2020 50.65
~ 'Information presented in the 1997 Local Water Supply
Plan.
z Capacity of raw water transmission system is
approximately 45 mgd_
s Sales contracts are peak day demand.
Furthermore, New Hanover County Commissioners have historically been concerned with surface water
vulnerability issues. The Lower Cape Fear Coastal Counties are located downstream of several hog farms,
agricultural centers, and industrial dischargers. The County Commissioners have clearly stated that an
independent and reliable water supply is a preferred water supply alternative.
Therefore, this alternative has been eliminated from consideration for several reasons. The LCFWSA does
J not currently have adequate raw water supply or infrastructure capacity to meet the projected peak day
needs of the project area even though there is potential raw water supply available in the Cape Fear River.
The combined cost of a nevi surface water treatment facility and improvements to the raw water
_ _ infrastructure system renders this alternative less economically favorable than aCounty-owned
ARCADIS Project No. NC702018.0000 3-3

~~rCEt'VE.D
I~C~%j '~'~j!i_N1INGTON, NC
~ 1!, _ ;~ ~ ZQQ~
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
groundwater treatment plant. In addition, the time required to attain additional raw water supply allocation
will impact the ability of the County to provide high quality drinking water to existing customers and will
likely result in a delay in the ability to meet planned near and long-term water supply needs.
3.3 Purchase Finished Water from Surrounding Counties
Several other water service providers serve the counties surrounding New Hanover. Under this alternative,
New Hanover County would purchase finished water from one or more surrounding counties. Water
service providers considered in this alternative include Brunswick and Pender Counties. These alternatives
are discussed in the following sections.
3.3.1 Brunswick County
Brunswick County owns and operates two water treatment facilities for a total capacity of 30 mgd. The
first facility is a 24-mgd surface water treatment plant treating raw water purchased from the LCFWSA,
and the second facility is a 6-mgd plant treating groundwater withdrawn from the Castle Hayne aquifer.
According to the 1997 LWSP, Brunswick County has a total raw water supply of 27.4 mgd, which includes
a contract to purchase up to 24 mgd of water from LCFWSA and a 12-hour yield of 3.4 mgd from the
Brunswick County well system.
Brunswick County provides finished water to residential, commercial, and industrial customers located in
Brunswick County. Brunswick County also sells finished water to several local municipalities, including
Carolina Shores, Caswell Beach, Holden Beach, Long Beach, North Brunswick Sanitary District, Ocean
Isle Beach, Shallotte, Southport, Sunset Beach, and Yaupon Beach. According to the 1997 LWSP,
Brunswick County has a sales contract totaling 6 mgd and sold approximately 3 mgd of finished water to
these other municipalities.
Water demand forecasts reported in the Brunswick County 1997 LWSP are summarized in Table 3-2. Peak
service area demands were calculated based on a 1997 peaking factor of 1.5. The reported 1997 annual
average and peak day demands were 13.7 and 21 mgd, respectively. The 1997 LWSP indicates that
Brnr's`"'-~k Co' `'~" r?at ,-.~ u~:nanas . is exceed the treatment capacity of 30 mgd prior to 2010. The
1°°7 L~NSP ir~'r e t'_1~.~ ~~:tlr.~wick Co~.~nt~; ~.~nll be 7rv?;tig3il_~s °,~~"~'a,^.
" ~' ~ ~ „ .~ ~~ e;3: Manz
~xpa~_sion from 2~ to 36 mgd. rurthermore, the County's raw water supply is currently limited by the
12-hour yield of the existing groundwater wells and the sales contract with LCFWSA.
ARCADIS Project No. NC702018.0000
3-4

aCN~ iwl< a,'I,~1G I ON, Nu

Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Table 3-2: Water Demand Projections for Brunswick County
Average Service Peak Service2
Area Day Demand Area Dem
d Sales Total Average Total Peak
an
Year m d Contracts Day Demand
2
Demand
1997' 11.3 m 0 mad an d an d
2000 12.1
18.2 6.0 17.3
7
1 23.0
2010
15.1 22 7 .
19.2
9
0 25.3
2020 18.2
27.3 .
24.1
10
6 31.7
.
28.8 37.9
~ Average service azea demand, sales, contracts, and total average daily demand reported in 1997 LWSP for
Brunswick County.
Z Peak service area demand calculated based on reported average servic

factor of 1.5. e area daily demand and 1997 peaking
3 The total peak day demand was calculated as the sum of the
sales contracts. peak day service area demand and outstanding
This alternative has been removed from consideration based on the aforementioned analysis. Brunswick
County does not have sufficient treatment capacity or the raw water supply to meet the needs of the New
Hanover County project area. This alternative would require that Brunswick County obtain additional raw
water supply capacity and upgrade WTp capacity. Additionally, this analysis does not take into
consideration any improvements to the LCF'WSA raw water infrastructure system or any costs associated
with the environmental impact of constructing a new finished water transmission main from Brunswick
County to New Hanover County.
3.3.2 Pender County
Pender County has several small water systems, including Burgaw, Rocky Point -Topsail Water Sewer
District, Surf City, and Topsail Beach. All of these systems rely primarily on groundwater for water
supply. Each of these systems reports a total raw water supply of less than 1 mgd. None of these systems
has water treatment facilities, with the exception of Surf Ci
plant. Based on the limited available resources, purchase of raw or treated water from PendertCounty has t
been eliminated as a viable option.
3.4 Purchase Finished Water from City of Wilmington
New Hanover County has evaluated the possibility of purchasing finished water from the City of
Wilmington. Wilmington owns and operates the 25.9-mgd Sweeney WTp, The City of Wilmington treats
up to 15 mgd of raw water from the Cape Fear River pumped from the City-owned Kings Bluff Pump
Station via 25 miles of 30-inch raw water transmission main. Wilmington also has a 15-mgd raw water
purchase contract with the LCFWSA, pumped via the LCFWSA-owned pump station. Thus, the City's
total surface water supply is 30 mgd.
ARCADIS Project No. NC702018.0000
3-5

RA=~~IV~~
DC~,~9 WILMINCTO^1. NC
Final Environmental
Jt~i_ 3 1 LGOF Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
The City of Wilmington has acquired several groundwater well and distribution systems from surrounding
utilities since the submittal of the 1997 LWSP. In 1999, the City of Wilmington purchased a groundwater
system from private utility companies, Cape Fear Utilities Inc. and Quality Water Supplies Inc. The
private utility companies served a large area south and east of the city limits as well as the Shearin Hills
area. The private utility companies owned and operated 23 wells withdrawing water from the Pee Dee
aquifer with a combined 12-hour pumping capacity of 5 mgd. The City has decommissioned the
groundwater system and converted all customers over to the surface water system. Thirteen of these wells,
with a combined 12-hour pumping capacity of 3.2 mgd, were decommissioned between March and
December of 2000. The remaining 10 wells were decommissioned in January 2004 and had a combined
12-hour pumping capacity of 1.8 mgd. The City currently maintains 4 of the 23 wells on active status for
emergency use only. The remaining 19 wells are listed as inactive (dormant) with the DEH and must go
through approval and testing prior to re-activation.
The final decommissioning ofthe groundwater system in January 2004 has increased water demands at the
Sweeney WTP. As a result, the Sweeney WTP experiences peak day demands close to its current rated
capacity of 25.9 mgd_ In 2004, the Sweeney WTP reported a peak day demand of almost 24 mgd.
However, the 1997 LWSP projected peak-day demands to reach 19.4 mgd in 2000 and 21.3 mgd in 2010.
Based on this trend, it is likely that the City of Wilmington's peak day demand will exceed current
treatment capacity prior to 2010.
In addition to exceeding treatment plant capacity, the water demand projections also indicate that the peak
day demand may exceed the City's raw surface water supply of 30 mgd by 2020, particularly if the City
were to provide finished water to the project area. The City's raw water supply is limited by the capaciiy of
the 15-mgd Kings Bluff Pump Station and the existing 15-mgd raw water contract with the LCFWSA. The
2002 Cape Fear River Basin Water Supply Plan indicates that the City of Wilmington may increase its raw
water supply capacity up to 53.3 mgd. However, the Kings Bluff Pump Station would need to be upgraded
to accommodate a higher design flow, and the raw water transmission main would require 25 miles of
parallel line.
The City is in the process of conducting a water system master plan to identify short-term improvements to
address existing demands associated with decommissioning the groundwater system as well as plans to
address long-term water supply needs.
Based on the above evaluation, the City of Wilmington does not currently have adequate water supply or
treatment capacity to accommodate near-teen water supply needs of the northern section of New Hanover
County. Although the City is evaluating short-term improvements, these improvements will only
accommodate existing demands associated with decommissioning the groundwater system.
The ability of the City of Wilmington to serve New Hanover County in the future is also uncertain.
Significant capital improvements will be required for increased water treatment capacity, increased finished
ARCADIS Project No. NC702018.0000 3-6

R~'CE~VEi~
1?r11,1 1l1/jl ^/'I~JI` ; ,~~~ i~~l,'. Final Environmental
Assessment for
.iUl_ ~ 1 2006 New Hanover County
WTP and Well Field
Alternatives Analysis
water pumping and storage capacity, and increased raw water supply intake capacity. It is estimated that
the New Hanover County's portion of the City of Wilmington's treatment plant and fmished water
pumping upgrade capital costs would be approximately $21 million based on a County demand of 6 mgd.
Additionally, the County's portion of the raw water infrastructure upgrade would be approximately
X15 million. The total project cost is estimated at $36 million.
The issue of surface water vulnerability should also be taken into consideration for this alternative. An
expansion of the existing Cape Fear River water supply source will not provide an independent and reliable
water supply source to the residents of New Hanover County.
In summary, this altemative has been removed from consideration for several reasons. The City of
Wilmington has inadequate treatment plant capacity to meet near-term water supply demands in the project
area with decommissioning ofthe groundwater system. Second, the ability of Wilmington to serve long-
term water supply demands in the project area is uncertain. The City of Wilmington will need to expand its
existing facility and attain additional raw water supply capacity before 2010, and a large portion of this cost
would be passed on to New Hanover County customers.
3.5 County-Owned Surface Water Treatment Plant and Raw Water intake
A County-owned surface WTP and raw water intake alternative explores the possibility of New Hanover
County obtaining a surface water supply source and constructing a surface water treatment plant. Results
from the Cape Fear River Basin Water Supply Plan indicate that 106.6 mgd of raw water supply is
available in the Lower Cape Fear area. Currently, the City of Wilmington and the LCFWSA have raw
water intakes in the Lower Cape Fear River with capacities of 15 and 45 mgd, respectively. Therefore,
excess water supply capacity should be available in the Lower Cape Fear to accommodate New Hanover
County needs.
This altemative would require that New Hanover County build a water intake structure and raw water
transmission system to transmit raw water from the Cape Fear River to New Hanover County. To reduce
the potential for withdrawing brackish water, raw water would need to be obtained upstream of US Lock
and Dam No. 1. The raw water transmission main would likely follow the raw water transmission
easements for the LCFWSA and Wilmington's Kings Bluff Pump Station. It is estimated that
approximately 32 miles of 24-inch raw water transmission line would be required for an ultimate WTP
capacity of 8 mgd. It is estimated that the capital construction cost of this raw water transmission system
would be approximately $26 million.
The County does not own a treatment facility; therefore, this alternative would require the County to build
and operate a surface water treatment facility to treat Cape Fear River water. The cost for a surface water
treatment plant is expected to be much higher than the cost for a groundwater treatment facility. Water
from the Cape Fear River is of poorer quality than water from the Pee Dee or the Castle Hayne aquifers.
ARCADIS Project No. NC702018.0000
3-7

ra ~_ .~ ~~ r-~
S.~ l.~ ,
;Ui_ .~ i 2006
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Also, water quality in the Cape Fear River varies seasonally with storm events. Groundwater quality is
expected to be more stable. The capital construction cost of a new 6-mgd surface water treatment facility
was estimated to be approximately $24 million. Therefore, the total capital construction cost for this
~rnativ° a estimated at $50 million.
This alternative is considered cost-prohibitive and, therefore, has been eliminated as a viable option.
Additionally, this altemative does not take into account the surface water vulnerability issue that is
important to New Hanover County. Additionally, this alternative does not take advantage of existing raw
water transmission structures, such as the LCFWSA raw water transmission system, or share the cost with
implementing a new transmission system with other users. Also, the environmental issues associated with
anew transmission main are not fully evaluated and quantified in this discussion.
3.6 New County-owned Membrane Softening Water Treatment Plant and Well Field -Selected Alternative
New Hanover County has selected the County-owned membrane softening treatment plant and well field
system altemative as the future treatment method and reliable, protected, water supply source for the
County. This alternative does not dramatically change the way the current public water supply system is
managed and operated, with the exception of a method of treatment to produce high quality drinking water,
a centralized and managed well field system, and balancing withdrawals from the Pee Dee aquifer with
water supplied from the Castle Hayne aquifer. This altemative would replace 5.9 mgd of existing County
well system capacity. The rise of consumer complaints and hence the demand for high quality drinking
water has significantly paved the way for the implementation of this project.
The total present worth analysis of the proposed project is provided in Table 3-3. The capital construction
cost and the total proiect cost (including engineering, legal, and administration costs) for the proposed
project is $24 million and $27 million, respectively. The total project cost is less than the capital
construction cost of the other considered alternatives-
There are also several intangible benefits of the proposed prof ect to New Hanover County in addition to
providing a high quality drinking water to County customers. First, the new well field system will replace
the existing well field system and will provide an avenue for the County to effectively manage and protect
groundwater resources. The proposed well field location will move groundwater extractions away from
sensitive coastal areas, thereby minimizing the potential for saltwater intrusion. Second, the proposed
project provides an independent and protected water supply system.
The proposed project also has the potential benefit of reducing long-term withdrawal from the Pee Dee
aquifer. New Hanover County currently obtains nearly all of it water supply from the Pee Dee aquifer.
Based on 2003 and 2004 demand data, approximately 90 percent of the County's existing demand is met by
water supplied from the Pee Dee aquifer. Average 2004 demand for the Pee Dee aquifer was 2.35 mgd.
ARCADIS Project No. NC702018.0000 ~$

'~CP.;~ ~,~.nl.~~IP~~T01~1. NC
L" - ,~
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
The proposed proj ect includes construction of a 6-mgd WTP where approximately 50 percent of the raw
water supply would be supplied from the Pee Dee aquifer and SO percent of the raw water supply would be
supplied from the Castle Hayne aquifer. With a planned membrane recovery rate of 80 percent, a
maximum of 7.3 mgd of raw water would be required to meet a finished water capacity of 6 mgd. Due to
the different treatment requirements for each of these raw water sources, separate treatment systems will
need to be provided for the Castle Hayne and Pee Dee aquifers. At peak production, approximately
3.7 mgd of raw water must be pumped from each well system to produce a 3-mgd supply of finished water
from each treatment system.
Since maximum day demands occur only for a short period during the year, the use of the two treatment
systems and their respective well fields throughout the year could be managed such that the average annual
withdrawal from that Pee Dee aquifer during the peak production year does not exceed the current average
annual withdrawal from that aquifer. For example, maximum utilization of the total plant capacity is
expected to occur during a year when the average daily demand is 4 mgd and the maximum daily demand
is 6 mgd. During this same year, an average of 2 mgd of finished water could be supplied by the Castle
Hayne aquifer, while an average of 2 mgd of finished water could be supplied from the Pee Dee aquifer. In
this case, the average withdrawal from the Pee Dee during a year when the plant is at full production could
be limited to the County's current average withdrawal from the Pee Dee aquifer.
New Hanover County intends to continue working with the City of Wilmington to plan the year 2050 water
supply needs. The County is also exploring the possibility of an interconnect with Wilmington for
emergency backup. Additionally, the County intends to explore the possibility of maintaining a few
existing County wells for emergency backup and/or monitoring. The County will work with DEH to
develop a protocol for this scenano_
The following subsections provide descriptions of the proposed water treatment facility, well field, raw
water transmission main, finished water transmission main, and concentrate disposal line.
ARCADIS Project No. NC702018.0000
3-9

I~,IECEIVED Final Environmental
C~~(~il ~AI;L.MINGTON, NC Assessment for
New Hanover County
iL)L ~ ' 20~F WTP and Well Field
Alternatives Analysis
Table 3-3: Present Worth Analysis for Proposed New Hanover Water Treatment Facility
County and Well Field System
Salvage Value
Component Capital Cost Salvage Amount Useful life (yrs)
Site work $472,000 $0 20
Yard Piping $472,000 $0 20
Membrane Treatment-Pee Dee $2,093,000 $0 20
Membrane Treatment -Castle Hayne $2,448,000
Greenland Filters -Castle Hayne $2,180 000
Finished Water and Waste Pumping $618 000 $0 20
Finished Water Storage $559,000 $0 20
Chemical Systems $321 000 $0 20
Instrumentation & Control $583,000 $0 20
Electrical $1,678,000 $0 20
Buildings $1,780,000 $0 20
Discharge Concentrate Force Main $1,249,000 $0 20
Pee Dee Wells (14 Wells) $2,655,000 $0 20
Pee Dee Raw Water Line $1,089,000 $0 20
Castle Hayne Wells (16 Wells) $2,845,000
Castle Hayne Raw Water Lines $723,000
Finished Water Line $243,000 $0 20
Easement Acquisition $151,000 $151,000 Indefinite
Land Cost for WTP $250,000 $250,000 Indefinite
Land Cost for Well Sites $160,000 $160,000 Indefinite
Wetlands Mitigation $280,000 N/A N/A
5u1i'1'UT.~L $23,905,000 $561,000 (*)
Present Worth Present Worth of
Capital Cost O&M Cost of O&M Salvage
$23,905,000 $1,766,000 $15,120,000 $177,000
Total Present Worth for New Hanover $38,850,000
County WTP and Well Field:
Time Period = 15 years; Interest Rate = 8 percent
Note: Operation and Maintenance (O&M) present worth cost includes the water treatment facility, well
field system, and raw and finished water systems.
ARCADIS Project No. NC702018.0000
3-10

~;~CE1~/~L~
~1~~:~1 ~1}~Jr~~ IV~~~lVl.'lT~~~. NC
~~~_: ~ ? 2006
3.7.2.2 Mixing Zone Analysis
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
A mixing zone analysis will be conducted based on the data obtained from the field data collected. There
are several models accepted for dilution modeling, with CORMIX~ being the most widely used model.
The models are capable of providing dispersion rates, distances and direction for any known constituent or
pollutant. However, based on the Speculative Limits provided by DWQ and the proposed discharge
characteristics, salinity variations will be the primary parameter of concern for this project.
A two~imensional hydrodynamic model will be utilized to develop a regional flow-field in the AIWW
stretch between the bridge to Figure Eight Island and Nixon Creek. This model will then be used to force a
near-field dispersion model needed to assess the alterations in salinity distribution caused by membrane
concentrate discharge. Forcing conditions for the hydrodynamic model will include information from a
two-day tidal current sun~ey (ADCP surveys, one day during neap tide and one day during spring tide
periods), as well as the long-term tide records described above. The information obtained from the
hydrodynamic analysis will be corroborated with the flow output from recent modeling conducted at
Mason Creek, where the northern model boundary was immediately north of the budge to Figure Eight
Island.
The water quality dispersion model will incorporate ambient salinity conditions to develop a "calibrated"
model of existing conditions. Standard dispersion coefficients associated with diffusers will be utilized to
evaluate the near-field dispersion of the buoyant plume from the proposed discharge. Salinity gradients
associated with existing conditions and the proposed diffuser discharge will be provided. The magnitude of
differences between ambient conditions and post discharge conditions will be estimated. In addition,
results from this modeling will assess changes caused by the proposed discharge relative to natural
variability.
ARCP,DIS Project No. NC702018.0000 3-23

;.~,ECE1vE~ Final Environmental
~(~;\;; v~.11l..Iv11NGTON. NG Assessment for
New Hanover County
' ~~ ~ ~ ZGOE WTP and Well Field
~. ,_.
Alternatives Analysis
3.6.1 Design Criteria for Proposed Water Treatment Facility
The proposed New Hanover County WTP is a 6-mgd groundwater treatment facility that will treat water
from the Pee Dee and Castle Hayne aquifers. The primary treatment process will be nanofiltration for
softening total organic carbon (TOC) removal and color removal. Separate membrane Titration units w711
be provided for the two source waters to alleviate the potential for membrane fouling from biological
growth or saturated salts. In addition, raw water from the Castle Hayne has high iron levels and requires
pre-treatment prior to membrane filtration.
Figure 3-1 provides the location of the proposed WTP, well field, and related infrastructure. A process
flow diagram and site plan of the proposed treatment system is illustrated on Figures 3-2 and 3-3,
respectively. The proposed WTP will initially be constructed for 6 mgd with future capability for 7.5 mgd.
The following subsections describe the proposed unit processes.
3.6.1.1 Pee Dee Treatment Train
The total capacity of the Pee Dee treatment train will be 3.0 mgd, which equates to a raw water feed rate of
approximately 3.6 mgd. Treatment processes will include cartridge filtration and nanofiltration in series.
Three vertical cartridge filter vessels with S-micrometer (µm) filters will be provided for particulate
re.~!O~: al. Two ranonltration units will be provided with a permeate capacity of 2.4 mgd. Source water will
be blended with permeate at a rate up to 20 percent (or 0.6 mgd). Design recovery for the nanofiltration
units is 80 percent. Three 1,050-gpm feed pumps will be provided for boosting water to a feed pressure of
about 110 pounds per square inch (psi).
3.6.1.2 Castle Hayne Treatmenf Train
The total capacity of the Castle Hayne treatment train will be 3.0 mgd, which equates to a raw water f ed
rate of approximately 3.7 mgd. Treatment processes (in series) will include oxidation with potassium
permanganate, tray aeration, raw water detention, greensand filtration, cartridge filtration, and
nanofiltration. A 300,000-gallon raw water detention tank will provide 2 hours of contact time for
potassium permanganate oxidation. Three greensand filters will be provided for iron and mare-anew
removal. The filters are sized based on a filter loading rate of 3.0 gpm/square feet. Three vertical cartridge
filter vessels with 5-µm filters will be provided for particulate removal. Two nanofiltration units will be
provided with a permeate capacity of 2.7 mgd. Source water will be blended with permeate at a rate up to
10 percent (or 0.3 mgd). Design recovery for the nanofiltration units is 80 percent. Three 1,050-gpm feed
pumps will be provided for boosting water to a feed pressure of about 110 psi.
ARCADIS Project No. NC702018.0000 3-11

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~,ECE1~.~E~ Final Environmental
Assessment for
DC~i+ ~~~i~~-M~~G I ~N' Nl' New Hanover County
~ ~~ ~ ~ 20Q~, WTP and Well Field
Alternatives Analysis
3.6.9.3 Post Treatment
Following nanofiltration, permeate from both the Pee Dee and Castle Hayne treatment trains will be
blended and the following chemicals will be added: .
^ Sodium hypochlorite (for disinfection)
^ Sodium hydroxide (for pH adjustment)
^ Corrosion inhibitor (for stabilization)
Finished water will then be conveyed to a 2.0-million gallon pre-stressed concrete tank for storage. Three
vertical-turbine pumps will be provided to pump finished water into the distribution system.
3.6.1.4 Backwash Waste Treatment System
The proposed WTP includes a waste treatment system for treatment of backwash waste. Approximately
0.1 mgd of backwash waste will be generated from backwashing greensand filters. Backwash waste will be
conveyed to a storage tank for clarification. Following a batch clarification process, clarified water will be
decanted and conveyed to the membrane concentrate discharge line. Solids will be pumped to the sewer
system or will be stored in a residuals storage tank for off-site disposal via land application by private
con =-actor.
3.6.2 Design Criteria for Proposed Well Fields
A conceptual well-field layout was developed in the 2001 Concept Design report based on results from the
water quality analyses, a 1996 hydrogeologic evaluation conducted by Edwin Andrews and Associates, and
pumping tests. Approximately half of the raw water supplied to the 6-mgd WTP will be provided by the
Pee Dee aquifer, while the other half will be provided by the Castle Hayne aquifer. A total 12-hour raw
water supply capacity of 7.3 mgd will be required for the 6-mgd WTP. The required 12-hour raw water
supply capacity was calculated based on a maximum day finished water capacity of 6 mgd assuming an
80 percent recovery rate in the proposed groundwater treatment plant, a 20 percent blending rate for the Pee
Dee aquifer, and a 10 percent blending rate for the Castle Hayne aquifer.
A series of wells will be installed to supply raw water to the WTP. In the 2001 Concept Design Report, it
was projected that each well should be capable of producing water,at a rate of 350 gpm. DENR limits
pumping time at peak day demand to a 12-hour period, so each well could produce water at a maximum
rate of 252,000 gpd (175 gpm). The 2001 Concept Design Report indicates that the wells should be spaced
between 800 and 1,600 feet apart, but indicates that alternate or sequencing operations maybe needed to
prevent excessive drawdown at a well spacing of less than 1,600 feet.
Approximately 16 well sites are proposed for the 6-mgd WTP. Both the Castle Hayne and Pee Dee
aquifers will be tapped at each well site. Therefore, the 6-mgd WTP will have approximately 32 wells.
ARCADIS Project No. NC702018.0000 3--15

r-~- .-~ f-- ~ /
DC~~'~"'a ~~'INGTON, NC
t1~_. ~ ? X006
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
Two of the new well sites have been permitted and constructed at the proposed WTP site. The additional
well sites are proposed to be located as shown in Figure 3-1. Four of the well sites will be located along an
unpaved road northeast of the plant site. An additional ten well sites will be located along Plantation Road.
As the County has not yet acquired the land for the proposed well sites, final placement of the well sites
may vary slightly from the proposed placement shown in Figure 3-l. Figure 3-4 illustrates a site plan for a
typical well site.
3.6.3 Design Criteria for Proposed Raw and Finished Transmission Mains
Two parallel raw water transmission mains will be constructed to transmit raw water from the well sites to
the WTP. One main will transmit water pumped from the Castle Hayne aquifer, while the other main will
transmit water pumped from the Pee Dee aquifer. Each raw water transmission main will consist of
approximately 17,000 feet (3.2 miles) of line ranging in size from 6-inch to 30-inch. Thus, a total of
34,000 feet (6.4 miles) of raw water transmission will be constructed as part of this project. Both raw water
transmission lines will be located mainly within existing dirt roads in the well field.
Approximately 200 feet of 16-inch finished water line will be installed to transmit finished water from the
WTP to an existing 16-inch line that runs along the south property line.
3.7 Proposed NPDES Discharge
The primary by-product of the membrane softening plant will be a membrane reject stream, which will
consist of concentrated groundwater. In addition, a small waste flow (less than 100,000 gpd) will be
generated from backwashing pressure filters. The total concentrate discharge will have a maximum daily
flow of approximately 2 mgd. An estimate of the membrane concentrate water quality is presented in
Table 3-5.
As part of this EA, the County is seeking an NPDES permit for the discharge of the membrane concentrate
stream to the AIWW. The following section presents results from an evaluation ofnon-discharge
alternatives, describes the proposed NPDES discharge, and outlines dilution modeling that will be
performed to demonstrate compliance with the proposed limits for this discharge.
ARCADIS Project No. NC702018.0000
3-16

3
WETLAND AREA
REMAINING
UNDISTURBED
PROPOSED
GENERATOR
100' RADIUS
OF PROTECTION
FOR WELL
PROPOSED
11' x 17'
WELL HOUSE
~ -~- ~
- ~
PROPOSED
FUTURE WELL (TYP.) -~- ~ ~ LIMIT OF FILL
POTENTIAL- FUTURE <~ ` ~ ~ />
LIMIT OF IMPACT ~ -: ~~-..-:.~-.-=-'-•~:- /
~, ~~=GI~A~~:=~ ,/ l
~ I ~:~: -- ,°- I / APPROXIMATE LIMIT OF WETLAND
~~ --::~~ ---,:-L IMPACT FROM ROADSIDE DITCH
WETLAND AR A\ " ~_
E
IMPACTED BY - GRAVEL
ROADSIDE DITCH \ - ACCESS 75'
EXISTING R/W ~-~-~ J~ DRIVE
APPROX. 15'
60' - .EXISTING DIRT ROAD.`--~~~---- -~ ~ - .~ -" - - - - ~ ~ - -- - -- -
EXISTING R/W
EXISTING ROADSIDE DITCH -
(APPROXIMATELY 1.5' DEEP)
MOST CONSERVATIVE AREA
OF PROPOSED WETLAND
IMPACT PER WELL SITE
MOST CONSERVATIVE AREA
OF FUTURE WETLAND IMPACT
PER WELL SITE
TOTAL AREA OF WETLAND
IMPACT PER WELL SITE
~~
~~
~ e 909 MARKET STREET
~~~~
ice, i y WILMINGTON, NC 28401
commuNty InlrasiruGUre consultams (910 762-4200

~~ffi~
ARCADIS .,
~~
= 0.09 ACRES
= 0.09 ACRES
= 0.18 ACRES
,- - -~ ~ ~_
FIGURE 3-4: TYPICAL WELL SITE
NEW HANOVER COUNTY WATER & SEWER DISTRICT
WELL FIELD AND WATER TREATMENT FACILITY

EECEIVE~
C~Ci~;" `.,~jii_n.~INGTON, NC Final Environmental
Assessment for
~_IL'L ~ L~~~ New Hanover County
WTP and Well Field
Alternatives Analysis
3.7.1 Evaluation of Alternatives to Surface Discharge
DWQ requires that alternatives to a surface water discharge be evaluated to ensure that surface water
discharge is the most environmentally sound of economically feasible alternatives. The following section
presents results from a concentrate disposal alternatives evaluation. Two potential alternatives to surface
water disposal for the proposed project include reuse opportunities via land application and discharge to an
existing wastewater treatment facility.
Table 3-4: Estimated Membrane Concentrate Water Quality'
Parameter Estimated Concentrate Concentration
Total Dissolved Solids (TDS) 1,100 mg/L
Total Hardness 1,000 mg/L as CaC03
Turbidity 20 NTU
Total Organic Carbon (TOC) 30 mg/L
pH
7.6
Residual Chlorine Non-Detect
Calcium 355 mg/L
Chloride 400 mg/L
Magnesium 22 mg/L
Sodium 68 mg/L
Sulfate
Non-Detect
Ammonia-Nitrogen 1.5 mg/L
Nitrate-Nitrogen

Total Phosphorus'- < 1 mg/L
Non-Detect
Arsenic Non-Detect
Beryllium
Non-Detect
Cadmium
Non-Detect
Chromium
Non-Detect
Copper
0.01 mg/L
Cyanide 0.1 mg/L
Lead
0.01 mg/L
Mercury Non-Detect
Nickel
Non-Detect
Selenium Non-Detect
Silver
Non-Detect
Zinc Non-Detect
tBased on mass balance conducted for 6-mgd VPII' assu
i
m
ng approximately 50 percent of raw
water supplied from Pee Dee aquifer and 50 percent of raw water supplied from Castle Hayne
aquifer. Mass balance assumes 80 percent membrane recovery with 20 percent bypass for Pee
Dee membrane system and no bypass for Castl
H
e
a
Z yne membrane system
Data from Castle Hayne aquifer not available. Membrane concentrate concentrations based o

Pee Dee data. n
ARCADIS Project No. NC702018.0000
3-18

RECEIVED
QCPiI ~hiILM1{~IGTGN. NC
;~ ;~ ~, , 200
1, ~~ FI
3.7.1.1. Reuse via Land Application
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alternatives Analysis
One alternative for disposing of the membrane concentrate is through reuse via land application. Based on
the location of the project and land use of the surrounding area, the most suitable land application option
would be sprinkler imgation on a golf course. Several golf courses are located near the proposed routing of
the concentrate disposal line along Porters Neck Road. Because the volume of membrane concentrate
produced will greatly exceed the irrigation requirements, this reuse option would be considered a secondary
disposal option to reduce the volume of concentrate that would be disposed of by other methods.
Results from this evaluation indicate that land application is not an environmentally feasible option.
Review of anticipated concentrate water quality indicates that land application may be severely restricted
due to potential osmotic effects, specific ion toxicity, and reduced soil permeability from application of a
waste stream with high sodium content (Metcalf and Eddy, 2003). For land application to be a viable
option, the waste stream must meet minimum hydraulic and water quality criteria. With an anticipated total
dissolved solids (TDS) concentration of between 1,000 and 2,000 milligrams per liter (mglL), land
application rates for the membrane concentrate will be moderately restricted due to potential osmotic
effects. In addition, specific ion toxicity may occur due to elevated sodium and chloride concentrations. At
the anticipated sodium concentration, the membrane concentrate is categorized as slightly-to-moderately
restricted for land application uses but at the anticipated chloride concentrate, the membrane concentrate is
categorized as severely restricted to land application uses. Finally, at the expected sodium concentration,
the membrane concentrate is anticipated to cause potential infiltration problems due to deterioration of the
r-.ysicai soil conditions. The severe land application restrictions outlined above make this option
environmentally infeasible.
At aninter-agency scoping meeting held on March 22, 2005 regarding the proposed NPDES discharge,
DWQ expressed concern about potential groundwater issues associated with land application of a highly
saline concentrate stream. Follow-up conversations with the Groundwater Section of DWQ indicate that
elevated chloride concentrations are already an issue in the Castle 1?a?~e aquifer in the vicinity of the golf
courses located in the Porters Neck area. Land application of the membrane concentrate in this area could
raise additional concerns regarding increased salinity concentrations in the surrounding aquifers (DWQ
Groundwater Section, Personal Communication with Charles Stehman, Apri12005).
3.7.1.2 Discharge to an Existing Wastewater Treatment Facility
A second option for disposal of the membrane concentrate is to discharge to the City of Wilmington
Northside WWTP. This alternative would require installation of a pump station and 44,500 feet (8.4 miles)
of force main (12-inch diameter} to convey membrane concentrate from the proposed WTP site to
Northside WWIP. The estimated capital cost for the pump station and force main line is approximately
$5 million.
~.RC:4DIS Project No. NC702018.0000 3_ ~

EC E 1 V E C) Final Environmental
~C~~1 ~/VlLMiNGTON, N J Assessment for
New Hanover County
l I ~_ :3 1 2006 WTP and Well Field
Alternatives Analysis
In addition to the pump station and force main costs, New Hanover County would likely be required to pay
a capacity use fee for the capacity at the Northside WWTP. It is estimated that the WWTp capital cost
associated with 2 mgd of wastewater treatment capacity at the Northside WWTP is $7.2 million (McKim &
Creed 2003). Therefore, the cost associated with building a force main, pump station and the expansion
required by the Northside WWTP would make this alternative economically infeasible.
In addition to being an economically unattractive option, this disposal option has several other significant
disadvantages. First, the introduction of high concentrations of TDS and monovalent cations, such as
sodium, can deteriorate settling performance in a biological treatment system. Second, the addition of this
waste stream would consume valuable wastewater treatment capacity. The City of Wilmington and the
NHCWSD have entered into a joint project to expand the City of Wilmington's Northside WWTP from 8
to 16 mgd to accommodate growth in the region. One of the primary purposes of this expansion is to
accommodate projected population growth through 2020. An additional expansion would likely be
required to accommodate a new 2-mgd discharge.
3.7.1.3 Selected Alternative -Surface Water Discharge
Based on results from the alternatives evaluation, surface water discharge has been identified as the most
feasible disposal option for the membrane concentrate stream. Therefore, as part of this project, the County
is seeking an NPDES permit for the discharge of the membrane concentrate.
The original proposed membrane concentrate discharge location for the project was to the headwaters of
Pages Creek. Pages Creek is classified as an SA water, but is closed to shellfishing in this location.
Speculative limits for a proposed concentrate discharge to Pages Creek were received from the DWQ in
2001. Since this time, the County has reviewed the proposed project and discharge location with ITNCW's
Center for Marine Science. Researchers with the Tidal Creeks Program suggested that the originally
proposed discharge location to Pages Creek would be problematic due to the presence of nitrogen
compounds in the concentrate. Research has indicated that nitrogen is the limiting nutrient in the majority
of creeks in the County and that this discharge could potentially be detrimental to existing water quality in
Pages Creek. Researchers with the Tidal Creeks Program recommended that the County relocate the
discharge near or into the AIWW.
Based on feedback regarding Pages Creek, the County has decided to move forward with efforts to
discharge the membrane concentrate to the AIWW. Two potential discharge locations to the AIWW were
identified. The first location would be at the end of Porters Neck Road. The second location would be
located south, either along or near the bridge to Figure Eight Island on Bridge Road. This segment of the
AIWW (from Mason's Inlet north to Topsail) is classified as an SA Outstanding Resource Water (ORW).
DWQ has indicated that a discharge to this segment of the AIWW would be feasible (as anon-domestic
and non-process industrial discharge). DWQ issued speculative limits for the proposed discharge to the
.AIWW in December 2004. A copy of the speculative limits is provided in Appendix A.
ARCADIS Project No. NC702018.0000
3-20

~ ~~ ~ f ~~ ~ ~ Final Environmental
I~(;l\;' 41111_;•,lif~lUTC~~~. (`1~i Assessment for
„n,,P New Hanover County
`''''~ WTP and Well Field
Alternatives Analysis
An inter-agency scoping meeting, including representatives from DCM, DWQ, DEH Shellfish Sanitation
Section, and the USACE, was conducted on March 22, 2005, to discuss potential discharge location(s) for
the proposed NPDES concentrate discharge to the AIWW. Agency guidance provided during this meeting
was used to identify potential concerns associated with the proposed discharge and to identify a preferred
location for outfall. A meeting summary is provided in Appendix B. Participating agencies at this meeting
indicated that placement of the effluent structure at the Figure Eight Island Bridge would create the least
overall impact.
Based on feedback from the respective agencies, a discharge location into the Middle Sound along the
AIWW at the Figure Eight Island Bridge was selected as the preferred discharge location. Figure 3-1
illustrates the proposed discharge location. A 16-inch concentrate discharge line will be routed from the
WTP site south to US 17, run northeast along US 17, east on Porters Neck Road, and southeast along
Edgewater Creek Road toward the bridge to Figure Eight Island. The project includes installation of
approximately 27,000 feet (6.1 miles) of 16-inch membrane concentrate discharge line. The discharge line
is sized to accommodate a future expansion of the WTP to 7.5 mgd. The estimated capital cost for the
membrane concentrate discharge line is approximately $1.5 million.
The proposed discharge would include amulti-port diffuser outfall located along the bottom of the AIWW.
The diffuser would be within the bridge easement of the USACE's AIWWrlght-of--way. The current plan
is to route the pipeline under the roadway structure of the bridge and then vertically down the last set of
pilings on the west side of the bridge. This discharge location would be directly adjacent to an open
shellfish area, but the effluent is not expected to affect the shellfish. Additionally, this discharge location is
not expected to have any navigation issues_
The mean water depth at the proposed discharge location is approximately 15 feet at low tide. The tides in
the proposed discharge area are semi-diurnal, with two daily tide cycles of uneven magnitude_ Because this
is a tidal area rather than riverine environment, it is expected that neap tidal (lowest monthly tidal range)
conditions will best represent the 7~ay duration, 10-year frequency low stream flow (7Q 10) typically used
for effluent discharge calculations, while spring tides will best represent typical high-water conditions.
Neap and spring tidal ranges in this area are approximately 3.0 feet and 4.8 feet, respectively. Therefore,
the worst-case mean water depth at the proposed discharge location will vary between approximately
15 and 18 feet.
Hydrodynamic modeling of tidal flows within this area have been conducted at varying levels for the
Mason Inlet Relocation Project (ATTv1, 2000; GBA, 2003), and these data have been used in initial
calculations. From these data, it has been determined that the tides within Middle Sound are affected by
Masonboro Inlet, Mason Inlet, and Rich's Inlet. The tidal exchange in the areas south of Figure Eight
Island Bridge are predominantly affected by Mason Inlet and Masonboro Inlet, while the area north of the
bridge is predominantly serviced through Rich's Inlet. The bridge itself is the "break point" between tidal
ARCADIS Proj~t No. NC702018.0000 3-21

RECEiVEi~
I~C~~~,i ~~11LMINGTv~J. IvJC
~UL 3 1 2006
Final Environmental
Assessment for
New Hanover County
WTP and Well Field
Alterna#ives Analysis
exchange to the .south and tidal exchange to the north. As a result, the proximity of the structure to the
bridge will affect both speed and direction of effluent dispersion.
3.7.2 Dilution Modeling for Proposed NPDES Discharge
The DENR Guidance Document for Water Treatment Plant Permitting recommends that dilution modeling
be conducted to evaluate dilution and mixing of membrane concentrate within the receiving stream. A
mixing zone analysis will be performed for the proposed membrane concentrate as part of the NPDES
permitting process. This mixing zone analysis will be used to assess potential impacts of the proposed
discharge at the selected discharge location and to demonstrate compliance with applicable water quality
standards and speculative NPDES limits.
As it has been important to determine the best location for the outfall structure prior to performing the tidal
data collection and modeling efforts, the tidal study and mixing zone analysis will be conducted separately
from development of the EA. A description of the data collection and diluting modeling that will be
conducted is provided in the following subsections. The results of the study described below will be
provided as part of the NPDES permitting cover.
3.7.2.1 Hydrodynamic and Water Quality Field Data Collection Including Bathymetry
The approach of the proposed tidal study will be to conduct all field data collection simultaneously.
Knowledge of the area indicates that the project area maybe treated as a closed embayment and field data
collection efforts are focused as such. Bathymetric (profile) data.will be collected in the area from Rich's
Inlet just north of Nixon Creek to 1,000 feet south of the bridge to Figure Eight Island and will include the
marina basin area. Data will be collected using USACE's standards and would include profiles on 250-foot
centers. Existing rectified aerial photography will be utilized to acquire elevations of the weddry tidal
marsh within the project area.
In order to properly evaluate tidal flows through the project area, pressure sensor tide gauges will be
installed north and south of the proposed discharge point. The sensors will collect continuous water surface
elevations for one lunar tide cycle (30 days). The tide gauges will be properly calibrated to the same datum
as the bathymetric data_ Asper the NPDES requirements, background salinity and temperature data will be
collected north of the study area on the AIWW at the confluence of Green Channel and the AIWW. The
bathymetric and tidal data will be used to generate the model used to perform the mixing zone analysis. In
addition, Acoustic Doppler Current Profiling (ADCP) will be performed to calibrate water flow parameters
within the model.
_ Pre-project water quality samples will be taken three times during the 30-day study period at both of the
tide gauge locations and at the background test location. Per NPDES requirements, the samples will be
tested for dissolved oxygen (DO), temperature, pH, conductivity, salinity, and chlorides.
ARCADIS Project No. NC702018.0000 3_22

~I I~ ~ _ _ J
NEW HANOVER COUNTY WATER TREATMENT
PLANT OUTFACE DIFFUSION STUDY,
NEW HANOVER COUNTY, NORTH CAROLINA
by Trey Ruthven
John Ramsey
DRAFT REPORT -December 2005
1
Applied Coastal Research and Engineering, Inc.
766 Falmouth Road, Building A, Unit 1 C
i Mashpee, MA 02649
....~.
ii+ed

R~CE~V~D
ACM V~IILMINGTON. NG
~UL 3 1 200E
Water Quality Model
The average tide range in the Atlantic Intracoastal Waterway near the Figure "8" Island
Bridge is 3.58 ft. The outfall's proposed location for installation is at a depth of
approximately 12 ft NII.,W. The depth of water over the outfall will increase to
approximately 15.6 ft near high tide. Complex tidal flow patterns exist in the Intracoastal
Waterway near the bridge and result from the interaction of tidal-induced water level
fluctuations between Mason Inlet to the south and Rich Inlet to the north. A two-
dimensional finite element water quality model, RMA-4, was employed to study the
effects of water treatment discharge on the Intracoastal Waterway. The RMA-4 model
provides an appropriate tool for determuung salinity changes in the intermediate and far-
field regions surrounding the proposed outfall structure. The results of this study are
attached to this report.

~~CEIViCD
~C>1~ N/lLMINGTGN. ~ti!C
JUt. 3 1 2006
1. INTRODUCTION
The purpose of this study was to examine the influence of the discharge from the
New Hanover County Water Treatment Plant upon the salinity in the Intracoastal
Waterway and the surrounding salt marsh. The New Hanover County Water Treatment
Plant draws water from the Pee Dee and Castle Hayne aquifers in New Hanover County,
North Carolina. The plant plans to produce 9 million gallons of fresh water a day with a
byproduct of between 0.9 and 2.0 million gallons a day of partially saline water. The
saline discharge water is planned to have a concentration of 536.4 mg/L or 0.536 ppt
and will be discharged into the Intracoastal Waterway at the "Figure 8" Island Bridge
shown in Figure 1. The overall purpose of the modeling effort was to determine the
influence of the discharge upon salinity concentrations in the Intracoastal Waterway and
the adjoining salt marshes, which have a salinity concretion of approximately 35,200
mg/L or 35.2 ppt.
Due to the complex tidal flow patterns in the Intracoastal Waterway around
"Figure 8" Island Bridge resulting from the interaction between Mason and Rich Inlets,
the dispersion of the water treatment discharge was evaluated using two-dimensional
(depth-averaged) hydrodynamic and dispersion models. The numerical models allow for
a quantitative assessment of the dispersion taking into account the complex flow
patterns and mixing which could not be achieved using standard dispersion only models.
The study area extends north and south of the "Figure 8" Island Bridge and
encompasses sections of the Middle Sound marsh. The bounds of the model were
determined by the field data that was available to determine various physical properties
needed to parameterize the hydrodynamic and dispersion models.
The evaluation of dispersion from the water treatment discharge proceeded as
two component efforts. The first portion of the study focused on the development of a
numerical hydrodynamic model of the Intracoastal Waterway. Using bathymetry survey
data made available by Gahagan & Bryant Associates (GBA), a model grid was
generated for use with the RMA-2 hydrodynamic code. Tide data collected by GBA
within the study area was used to provide open boundary time series required to run the
RMA-2 model. Additionally, measured Acoustic Doppler Current Profiler (ADGP) data
collected at the "Figure 8" Island Bridge was used to validate the model.
The hydrodynamic model was used as the basis of the second component to this
study, the dispersion and mixing of the water treatment discharge within the Intracoastal
Waterway. The model was run over afive-day period to examine mixing trends and
dispersion patterns. Results of the analyses provide insight into the impacts the outfall
will have on the system. Amore detailed evaluation of the discharge dispersion in the
Intracoastal Waterway is presented in Section 4.

~~
~~~~ ~/J
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Figure 1. ~ Topographic map detailing the area between Mason Inlet and Rich Inlet, in New
Hanover County, North Carolina. The "Figure 8" Island Bridge is located in the
center of the map and is the location of the New Hanover County Water Treatment
Plant discharge.
3

F
t
~~ !~' ; .
~ ~~_ ~ ? X06
4
will be located on the western pier of the bridge, adjacent to the navigation channel.

2. DATA ANALYSIS
The field data collection portion of this study was performed by GBA. To
characterize the physical properties of the Intracoastal Waterway, field data was need to
describe and parameterize the numerical models. Bathymetry was collected along the
Intracoastal Waterway so that it could be accurately represented within the computer
hydrodynamic model. In addition to the bathymetry, tide data were also collected in the
system. Temporally varying tide height records were utilized to "drive" the circulation
model, and also to calibrate and verify its performance. In addition, ADCP flow data
collected at the "Figure 8" Island Bridge provided independent validation of the
performance of the calibrated model.
2.1 Bathymetry Data
Bathymetry along the Intracoastal Waterway was collected by GBA during April
2005. The survey paths are shown in Figure 3. The resulting bathymetric surface
created by interpolating the data to a finite element mesh is shown in Figure 4. All
bathymetry was tide corrected, and referenced to the North Geodetic Vertical Datum
(NGVD 29). Although no bathymetry data was available within the Middle Sound marsh,
channel and marsh plan elevations were estimated from previous work in the vicinity of
nearby Mason Inlet.
2.2 Tide Data Collection
Tide data records were collected at three stations in the Intracoastal Waterway
by GBA. The first was located at the "Figure 8" Island Bridge, the second gage was
located north of the bridge along the channel, and the third was in the Nixon Channel.
The locations of the stations are represented by the red triangles in Figure 5. The
Temperature Depth Recorders (TDR) used to record the tide data were deployed for a
41-day period between May 27, 2005 and July 7, 2005. The elevation of each gauge
was surveyed relative to NGVD 29. Each tide record was used to as the open boundary
condition of the hydrodynamic model.
Plots of the tide data from the three gauges are shown in Figure 6, for the entire
41-day deployment. The spring-to-neap variations in tide range are easily discernable in
these plots. A visual comparison between tide elevations at the three stations shows
that there is only a minor variation in the tide range between the stations. In addition, the
phase lag between the gauges also was very small, indicating a relatively weak
elevation gradient across the model domain. Therefore, the hydrodynamic model results
were very sensitive to small changes in tidal elevation and phase.
~~>
~l it ~~ ~ `i
i _ -. ~..
5

~ c ~ ~~
r`~- ~ 1 ;,
.i LJ11. ~ t ,a... iv _ .. ~-
~~,!_ '_ [046
Figure 3. Transects from the bathymetry survey.

hydrodynamic model. Contours represent the bottom elevation relative to
NGVD 29.

~~ _ f3 ~ _'. U ~.
7

~U~ i ~.~
nr.ti,~ 1~~~ ~,i~,~~-.
r„_„ - _ __

Figure 5. Tide gage locations.

~Ci1~1~VV~ y~ NG ~D
ON. NC
JIJI 3 1 2006
A1WVV Figure 8 Tide Gage
3
2
1
0
-1
-2
n
0
~ 4
z
3
c ~
0
"> 1
W
m
U
-1
3 -~
3
2
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-2
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PJWW Tide Gage
O5l3JA5 O6r04105 06ti19A5 C6/14A5 06/19x05 06/14/05 O6119A5 07A4105
Nizan Channel Tide Gage
05/30rA5 06N4A5 06109/05 06/14,95 06/19x05 06(14105 06129/05 07x94105
Figure 6. Plots of observed tides for the 41-day period between May 27 and July 7, 2005.
The top plot shows tides for "Figure 8" Island Bridge, the middle plots shows the
tides North along Intracoastal Waterway, and the bottom plot shows tides recorded
for the Nixon Channel. All water levels are referenced to the North Geodetic
Vertical Datum (NGVD 29).
2.3 ADCP Data Collection
The measurements were collected using an. Acoustic Doppler Current Profiler
(ADCP) mounted aboard a small survey vessel by GBA on June 22, 2005. The boat
repeatedly navigated apre-defined set of transect lines through the area, approximately
every 30 minutes, with the ADCP continuously collecting current profiles. This pattern
was repeated for an approximate 14-hour duration to ensure measurements over the
entire tidal cycle. The results of the data collection effort are high-resolution
observations of the spatial and temporal variations in tidal current patterns throughout
the survey area.
9

i~~L~1Vi=:~'.
!UI,. ~ .3. ~OOE
3. HYDRODYNAMIC MODELING
For the modeling of the water treatment outfall along the Intracoastal Waterway,
Applied Coastal utilized astate-of--the-art computer model to evaluate tidal circulation.
The. particular model employed was the RMA-2 model developed by Resource
Management Associates (King, 1990). It is atwo-dimensional, depth-averaged finite
element model, capable of simulating transient hydrodynamics. The model is widely
accepted and tested for analyses of estuaries or rivers. Applied Coastal staff members
have utilized RMA-2 for numerous hydrodynamic studies including a hydrodynamic and
sediment transport analyses of Mason Inlet and Middle Sound System New Hanover
County, North Carolina (Kelley and Ramsey, 2003), a marsh habitat reclamation project
in Chesapeake Bay (Ramsey and Ruthven, 2003), and a hydrodynamic and sediment
transport analyses in St. Lucie Inlet, adjoin portions of AIWW, and in the Indian River of
Martin County, FL (Ramsey et al, 2005).
3.1 Model Theory
In its original form, RMA-2 was developed by William Norton and Ian King under
contract with the U.S. Army Corps of Engineers (Norton et al., 1973). Further
development included the introduction of one-dimensional elements, state-of-the-art pre-
and post-processing data programs, and the use of elements with curved borders.
Recently, the graphic pre- and post-processing routines were updated by a Brigham
Young University through a package called the Surface water Modeling System or SMS
(BYU, 1998). Graphics generated in support of this report primarily were generated
within the SMS modeling package.
RMA-2 is a finite element model designed for simulating one- and two-
dimensional depth-averaged hydrodynamic systems. The dependent variables are
velocity and water depth, and the equations solved are the depth-averaged Navier
Stokes equations. Reynolds assumptions are incorporated as an eddy viscosity effect to
represent turbulent energy losses. Other terms in the governing equations permit friction
losses (approximated either by a Chezy or Manning formulation), Coriolis effects, and
surface wind stresses. All the coefficients associated with these terms may vary from
element to element. The model utilizes quadrilaterals and triangles to represent the
prototype system. Element boundaries may either be curved or straight.
The time dependence of the governing equations is incorporated within the
solution technique needed to solve the set of simultaneous equations. This technique is
implicit; therefore, unconditionally stable. Once the equations are solved, corrections to
the initial estimate of velocity and water elevation are employed, and the equations are
re-solved until the convergence criteria is met.
3.2 Model Setup
There are three main steps required to implement RMA-2:
Grid generation
Boundary condition specification
Calibration
10

R~UE1~~1=~
DChil VVILMING OiV. NC
JU! 3 ~ 2000
The extent of the finite element grid was generated using digital aerial
photographs covering the area between Mason and Rich Inlets. The aerial photographs
were provided by GBA. Atime-varying water surface elevation boundary condition
(measured tide) was specified at the north and south boundaries of the Intracoastal
Waterway and along the main marsh channel along Nixon Channel based upon the tide
gauge data collected at those locations. Once the grid and boundary conditions were
set, the model was calibrated to ensure accurate predictions of tidal flows. Various
friction and eddy viscosity coefficients were adjusted, through several model calibration
simulations for the system, to obtain agreement between measured and modeled tides
and the ADCP measurements.
3.2.1 Grid generation
The grid generation process was aided by the use of the SMS package. Digital
aerial orthophotos and bathymetry survey data were imported to SMS, and a finite
element grid was generated to represent the system. The aerial photographs were used
to determine the land boundary of the system, as well as determine the surface
coverage of salt marsh. The bathymetry data was interpolated to the developed finite
element mesh of the system. The completed grid consists of 2,376 nodes, which
describe 995' two-dimensional (depth-averaged) quadratic elements. The grid covers
approximately 900 acres. The maximum nodal depth is _-17.04 ft (NGVD 29), in
Intracoastal Waterway. A portion of the completed grid mesh is shown in Figure 7.
Figure 7
Plot of hydrodynamic model grid mesh around the "Figure 8" Island Bridge. Color
contours represent the bathymetric elevations assigned to the grid.
11

FiECE~\/E~,
~7CM U/ILMING! 0~~1. I`JC
:1UL ~ ~ 200b
The finite element grid for the system provided the detail necessary to evaluate
accurately the variation in hydrodynamic properties along the Intracoastal Waterway and
wide areas of salt marsh. The SMS grid generation program was used to develop
quadrilateral and triangular two-dimensional elements throughout the estuary. Grid
resolution was governed by two factors: 1) expected flow patterns, and 2) the
bathymetric variability of the system. Relatively fine grid resolution was employed where
complex flow patterns were expected and where bathymetric coverage allowed. For
example, smaller node spacing surrounding the "Figure 8" Island Bridge was utilized to
represent the water treatment diffuser and the mixing zone of the diffuser with the
Intracoastal Waterway tidal flow. Widely spaced nodes were often employed in areas
where flow patterns are not likely to change dramatically, such as in the marsh plains,
where dramatic differences in flow are not anticipated. Appropriate implementation of
wider node spacing and larger elements reduced computer run time with no sacrifice of
accuracy.
3.2.2 Boundary condition specification
Three types of boundary conditions were employed for the RMA-2 model of the
system: 1) "slip" boundaries, 2) tidal elevation boundaries, and 3) flow boundaries. All of
the elements with land borders have "slip" boundary conditions, where the direction of
flow was constrained shore-parallel. The model generated all internal boundary
conditions from the governing conservation equations. Tidal boundary conditions were
specified at the boundaries of the Intracoastal Waterway and marsh channel along the
Nixon Channel. Tide gauge measurements provided the required data. Dynamic (time-
varying) model simulations specified a new water surface elevation every model time
step (10 minutes). Flow from the water treatment plant was specified as a flow boundary
condition based upon the expected discharge rates.
3.2.3 Calibration
After developing the finite element grids, and specifying boundary conditions, the
model of the waterway was calibrated. The calibration procedure ensures that the
model predicts accurately what was observed in nature during the field measurement
program. Numerous model simulations are required for an estuary model, specifying a
range of friction and eddy viscosity coefficients, to calibrate the model.
Calibration of the hydrodynamic model required a close match between the
modeled and measured tides and flows. The model was calibrated using visual and
numerical references to check the agreement between modeled and measured tides.
The coefficients utilized for model calibration were based on previous experience with
other estuarine/salt marsh systems with similar tidal characteristics.
3.2.3.a Friction coefficients
Friction inhibits flow along the bottom of estuary channels or other flow regions
where velocities are relatively high. Friction is a measure of the channel roughness, and
can cause both significant amplitude damping and phase delay of the tidal signal.
Friction is approximated in RMA-2 as a Manning coefficient, and is applied to grid areas
by user specified material types. Initially, Manning's friction coefficients between 0.02
and 0.07 were specified for all element material types. These values correspond to
12

R~C~1V~
ACM WILMIwGT~'+`a. N~,
Table 1. Manning's Roughness coefficients used in
simulations of modeled waterway. These
waterway delineations correspond to the
material pe areas shown in Fi ure 8.
System Embayment Bottom
Friction
Dischar a 0.030
Marsh Channel 0.035
Marina Channel 0.025
Marsh Plain 0.070
Iq~ 0.025
3.2.3.b Turbulent exchange coefficients
JUL. 3 1 CVOs`
Turbulent exchange coefficients approximate energy losses due to internal
friction between fluid particles. The significance of turbulent energy losses increases
where flow is swifter, such as inlets and bridge constrictions. According to King (1990),
these values are proportional to element dimensions (numerical effects) and flow
velocities (physics). In most cases, the modeled systems were relatively insensitive to
turbulent exchange coefficients because there were no regions of strong turbulent flow.
Typically, model turbulence coefficients were set between 80 and 200 Ib-sec/ft2.
3.2.3.c Marsh porosity processes
Modeled hydrodynamics were complicated by wetting/drying cycles on the marsh
plain included in the model.. Cyclically wet/dry areas of the marsh will tend to store
waters as the tide begins to ebb and then slowly release water as the water level drops
within the creeks and channels. This store-and-release characteristic of these marsh
regions was partially responsible for the distortion of the tidal signal, and the elongation
of the ebb phase of the tide. On the flood phase, water rises within the channels and
creeks initially until water surface elevation reaches the marsh plain, when at this point
the water level remains nearly constant as water `fans' out over the marsh surface. The
rapid flooding of the marsh surface corresponds to a flattening out of the tide curve
approaching high water. Marsh porosity is a feature of the RMA-2 model that permits the
modeling of hydrodynamics in marshes. This model feature essentially simulates the
store-and-release capability of the marsh plain by allowing grid elements to transition
gradually between wet and dry states. This technique allows RMA-2 to change the
ability of an element to hold water, like squeezing a sponge. The marsh porosity feature
of RMA-2 is typically utilized in estuarine systems where the marsh plain has a
significant impact on the hydrodynamics of a system.
3.2.3.d Comparison of modeled tides and measured tide data
A visual calibration was used for the modeled tidal hydrodynamics in the coves.
Generally a harmonic analysis would be done to calibrate the modeled tides against
gage measurements throughout the estuary system. Since the gauge records were
used to drive the tidal boundary conditions, a harmonic analysis of the water levels could
not be used to provide a clear indication of the calibration. As stated previously, the
relatively small tidal amplitude and phase differences across the model domain caused
the hydrodynamic model to be sensitive to small changes. Instead, it was determined
14

RECElVE~
LLCM WILMINGTON. NC
.iUl. 3 ~ ~00~
typical Manning's coefficients determined experimentally in smooth earth-lined channels
with no weeds (low friction) to winding channels and marsh plains with higher friction
(Henderson, 1966).
To improve mode! accuracy, friction coefficients were varied throughout the
model domain. First, the Manning's coefficients were matched to bottom type. For
example, lower friction coefficients were specified for the smooth bottom of the channels,
versus the vegetated marsh surface, which provides greater flow resistance. Final
model calibration runs incorporated various specific values for Manning's friction
coefficients, depending upon flow damping characteristics of separate regions within
each estuary. The final layout of material types is shown in Figure 8. Manning's values
for different bottom types were initially selected based ranges provided by the Civil
Engineering Reference Manual (Lindeburg, 1992), and values were incrementally
changed when necessary to obtain a close match between measured and modeled
tides. Final calibrated friction coefficients are summarized in the Table 1.
F
lel
13
y calibration parameters.

R~CE~V~~
?~CP~f ~'JILMINGTGrv), Nt,
that a reasonable match of the tidal signal combined with the proper trends in the flow a
data used for validation would provide appropriate confidence in model results.
A visual calibration of the model was achieved using the aforementioned values
for friction and turbulent exchange. Figures 9 and 10 illustrate the seven-day calibration
simulation. Modeled (dotted line) and measured (solid line) tides are illustrated at each
model location with a corresponding TDR. The graphs indicated excellent agreement
between the model and data.
5
d.5
4
3.5
3
2.5
z 2
m 1.5
7
0.5
0
-0.5
-~
-1.5
-~
Figure 8 Bridge Gage
06!18 06/19 0680 06!11 06!12 06!13 06(24 06!25
Tme
5
4.5
4
3.5
.., 3
2.5
z 2
7.5
7
-~~ 0.5
~ 0
-0.5
.7
•1.5
0~ 06121 06/22
Tme
Figure 9. Comparison of model output and measured tides for the TDR location at the "Figure
8" Island Bridge.
15

IAWW Gage
c~
z
C
{
_~
Time
c~
z
3
~~
~rn
Time

Figure 10. Comparison of model output and measured tides for the TDR location along north
edge of the Intracoastal Waterway.
3.2.3.e Comparison of modeled flows and measured flow data
In addition to depth-averaged velocities, the total flow rate of water flowing
through a channel can be computed with the hydrodynamic model. Flow rates where
computed across a transect in the Intracoastal Waterway just north of the "Figure 8"
Island Bridge. The variation of flow as the tide floods and ebbs is seen in the plot of
channel flow rates in Figure 11. The maximum flood flow rates reach approximately
4,000 ft3/sec. Maximum ebb flow rates are greater, or about 7,000 ft3/sec.
A verification of the model was conducted by comparing flow rates computed
from ADCP measurements to flow rates extracted from the hydrodynamic model. The
hydrodynamic model was run for the period of June 18 to June 26, 2005 to simulate the
time period when the ADCP measurements were taken (June 22, 2005). Flow
measurements were extracted from the model at the location of the ADCP measurement
transect. A comparison of the modeled and measured flow rates for the transect is
shown in Figure 11. The graphs show that the model follows the trends and
characteristics of the ADCP data. However, the model indicates a slightly different flow
pattern than the measurements.
,-, =ice ;= i'~l ~.. ~
r+~
~'a. ~~
ii +, ; 1 206
. J _. 16

r. {~ ..1 -- , ., f C- ~
uC~;l ~~,;!i_i~~1!NG ! val. I~JC
.~~ ~!_ i 1 200fi
There are several possible reasons for the differences between modeled and
measured flow. The primary limitation of ADCP measurements is the inability to capture
the outer edges of the channel as a result of depth limitations associated with the survey
technique. For example, shallow water depths at the channel edges prevent
measurements in these areas creating data gaps. The size of these gaps is dependent
of the side slopes of the channel. For this case, the measured flow rates are assumed to
be 10 to 15 percent lower than actual flow rates. Secondly, the ADCP is unable to
measure velocities in the first 1 to 2 feet of the water column, both due to the ADCP
transducer being suspended below the water surface and acoustic signal blanking
across the first measurement cell. The ADCP cannot take measurements across the first
measurement cell since a time gap is required between the transmission and receipt of
the acoustic signal. To account for this unmeasured portion of the water column, the
standard ADCP software allows assumptions to be made about the velocity profiles and
uses this information to predict the flow in the unmeasured areas. This can lead to slight
under- or over- predictions in surface currents and currents in the sides of the channel,
thereby under- or over-predicting of flow rates. The current measurement limitations
(primarily the loss of data near the shallow channel edges) provide a reasonable
explanation for the observed error. Therefore, the ADCP measurements within the
Intracoastal Waterway provided adequate measurements to verify the results of the
hydrodynamic model.
3
4
3
v 'z
'm0_ Q
.~
.7.
1 I I I I 1 I I I I I I I ~ I -- I----
i

~ / \
\ /
1_ /
~.
'
~~ ~ _~ ~ //

\:~
~. \
.. ..
..
\\ ~
h 04h ~h OBh 10h 1Jh 1dh ' 1fih 1flh Jrlh ~~M mh
hour, June 71, 2CA5
'figure 11
Comparison of computed flow rates for the ADCP transect at the "Figure 8" Island
Bridge. Model period shown corresponds to transition from high to low tide and
back to high tide. Positive flow indicates southerly flow, while negative flow
indicates northerly flow.
17

4. DISPERSION CHARACTERISTICS
Several different data types and calculations were required to support the
dispersion modeling effort for the water treatment outfall into the Intracoastal Waterway.
These include the output from the hydrodynamics model, measurements of background
salinity, and estimates on the performance of the diffuser.
4.1 Model Description and Application
A two-dimensional finite element water quality model, RMA-4 (King, 1990), was
employed to study the effects of water treatment discharge on the Intracoastal
Waterway. The RMA-4 model has the capability for the simulation of advection-diffusion
processes in aquatic environments. It is the constituent transport model counterpart of
the RMA-2 hydrodynamic model used to simulate the fluid dynamics. Like RMA-2
numerical code, RMA-4 is atwo-dimensional, depth averaged finite element model
capable of simulating time-dependent. The RMA-4 model was developed with support
from the US Army Corps of Engineers (USAGE) Waterways Experiment Station (WES),
and is widely accepted and tested.
The overall approach involves modeling the salinity as a conservative
constituent. The salinity modeling is based upon CTD data collected by GBA and
analyses of the expected discharge from the water treatment plant. Water column
salinity measurements were utilized as model boundaries and as calibration data.
Hydrodynamic model output (discussed in Section 3) provided the remaining information
(tides, currents, and bathymetry) needed to parameterize the dispersion model of the
system.
4.2 Model Formulation
The formulation of the model is for two-dimensional depth-averaged systems in
which concentration in the vertical direction is assumed uniform. The depth-averaged
assumption is justified since vertical mixing by wind and tidal processes prevent
significant stratification in the model domain. The governing equation of the RMA-4
constituent model can be most simply expressed as a form of the transport equation, in
two dimensions:
a~ a~ a~ a a~ a ac
-+u-+v- _ -D -+-D -+6
at ax ay ax X ax ay y ay
where c in the water quality constituent concentration; t is time; u and v are the velocities
in the x and y directions, respectively; DX and D,, are the model dispersion coefficients in
the x and y directions; and 6 is the constituent source/sink term. Since the model
utilizes input from the RMA-2 model, a similar implicit solution technique is employed for
the RMA-4 model.
The model is therefore used to compute spatially and temporally varying
concentrations c of the modeled constituent (i.e., salinity), based on model inputs of 1)
water depth and velocity computed using the RMA-2 hydrodynamic model; 2) mass
loading input of the modeled constituent; and 3) user selected values of'the model
dispersion coefficients.
18

The RMA-4 model can be utilized to predict both spatial and temporal variations
in total for a given system. At each time step, the model computes constituent
concentrations over the entire finite element grid and utilizes a continuity of mass
equation to check these results. Similar to the hydrodynamic model, the water quality
model evaluates model parameters at every element at 10-minute time intervals
throughout the grid system. For this application, the RMA-4 model was used to predict
tidally averaged total salinity concentrations. In general, the RMA-4 model is designed
to evaluate far-field advection and dispersion processes. Since the water from the
treatment plant will be introduced to the Intracoastal Waterway through a diffuser
system, it will be readily mixed with the tidal waters adjacent to the "Figure 8" Island
Bridge. Therefore, the RMA-4 model provides an appropriate tool for determining salinity
changes in the intermediate and far-field regions surrounding the diffuser (i.e. more than
10 feet from the actual discharge).
4.3 Hydrodynamics and Tidal Circulation
Extensive field measurements and hydrodynamic modeling of the waterway were
an essential preparatory step to the development of the dispersion model. The result of
this work, among other things, was a model output representing the transport of water
within the system. Files of node locations and node connectivity for the RMA-2V model
grid were transferred to the RMA-4 water quality model; therefore, the computational grid
for the hydrodynamic model also was the computational grid .for the dispersion model.
The period of hydrodynamic output for the dispersion model run was the one described
in Section 3 of this report.
4.4 Measured Salinity Concentrations in the Intracoastal Waterway
In order to create a model that realistically simulates the salinity concentrations in
the system in response to the loading from the water treatment plant, it is necessary to
calibrate the model to actual measurements of water column salinity concentrations.
GBA conducted measurements of conductivity, temperature, and depth (CTD) to identify
gradients in salinity along the Intracoastal Waterway and analyze the influence of fresh
water inflow. CTD casts were taken at six stations throughout the area (Figure 12). The
sampling of the stations was conducted on October 3, 2005.
Typical vertical profiles of salinity are shown in Figure 13. There is no vertical
stratification seen in any of the CTD casts. The casts reveal that there is little variation in
salinity throughout the waterway or with the system. The mean concentration of salinity
is approximately 35 ppt. The lack of salinity gradients was noted at all of the CTD
locations.
~r~E., • ~~ ~,~„ _~„
- _ . ~ ~ -,
_. _ _ ~ ~J v
19

rn '- r-
~;~i, 9 .ti,;t j ~~~.;
... ..,.i i'~~~~iV~ i~ .. ~~~..
l + ~ ~'vUtF1.
20
Figure 12. Locations of CTD sampling stations.

~~~~ v~~ ,
ACM ~~/ILi1~?ING f0i~1. rJC
'~U! v 1 200
Cast 1 Cast 2 Cast 3 Cast 4 Cast 5

34 fi~linity lP3ll~
345 35 35
.5
34 Siliniry IPSN
345 35 35
.5
3 S+Gniry ~PSUI
4 345 35 35
.5 S~fmiq ~PSU~
3i 345 35 ~
.5
3
B Salinity (PSU)
4 345 35 35
.5
B 0 0 3
1 2
] 2 2
4 2
4 4
4 4 fi
6 6 6 i
3 B
8
Z
~ 8
a
~ B
a
~ 1
..
~
~
~ IO
16 16 10 .
I
12
14 12 12
14
14
I 12
14
14
Ifi
IB 16
16 1fi
1B 1
.. 16
16

Figure 13. Vertical profiles of depth versus salinity measured on October 3. 2005 at "Figure 8"
Island Bridge casts 1 through 5.
4.5 Dispersion Model Setup
Required inputs to the RMA-4 model include a computational mesh, computed
water elevations and velocities at all nodes of the mesh, constituent mass loading, and
spatially varying values of the dispersion coefficient. Because the RMA-4 model is part
of a suite of integrated computer models, the finite-element meshes and the resulting
hydrodynamic simulations previously developed for the system was used for the water
quality constituent modeling portion of this study.
For the model, an initial total salinity concentration equal to the concentration at
the open boundary was applied to the entire model domain. The model was then run for
a simulated month-long (28 day) spin-up period. At the end of the spin-up period, the
model was run for an additional 10 tidal cycle (125 hour) period. Model results were
recorded only after the initial spin-up period. The time step used for the dispersion
computations was 10 minutes, which corresponds to the time step of the hydrodynamics
input for the system.
4.5.1 Boundary Condition Specification
The only required inputs into the RMA4 salinity model of the system, in addition
to the RMA2 hydrodynamic model output, were salinities at the model open boundaries
21

~'~C~s"W~:r;
and the salinity of the water treatment discharge. The open boundary salinity was set at
35.2 ppt based on the CTD data. For water treatment discharge the salinity was set at
0.536 ppt based projected water treatment discharge information. The discharge input
used for the model was 3.09 ft3/sec or 3,000,000 gallons/day based on the maximum
predicted output from the water treatment plant. The discharge was distributed along
the side of the grid at the "Figure 8" Island Bridge within a 1-D element to represent the
diffuser. The diffuser is a combination of 4, 8-inch pipes, distributed over a 12-foot
square. The near-field mixing zone around the diffuser can not be accurately
represented in the model, so the 1-D element with similar dispersion characteristics was
added to represent the diffuser. This approach allows for accurate modeling of
intermediate and far-field diffusion characteristics, which specifically are the areas of
concern for this modeling exercise.
4.5.2 Model Calibration
Calibration of the salinity model generally proceeds by changing model
dispersion coefficients so that model output of salinity concentrations matched measured
data. However, due to the lack of variation in measured salinity concentrations the
model can not be calibrated against the measured variations throughout different tidal
cycles. Thus, the dispersion coefficient (E) values were set in model by using default
values of E for each grid material type based on the flow regime and observed values at
other locations. Observed values of E (Fischer, et al., 1979) vary between order 10 and
order 1000 m2/sec for riverine estuary systems characterized by relatively wide channels
(compared to channel depth) with moderate currents (from tides or atmospheric forcing).
Observed values of E in these calmer areas typically range between order 10 and order
0.001 mZ/sec (USAGE, 2001). The final values of E used in each sub-area of the
modeled systems are presented in Table 2. The dispersion coefficients values are
similar to values employed by Applied Coastal at other locations with similar
hydrodynamics characteristics.
Table 2. Values of longitudinal dispersion coefficient, E, used in
calibrated RMA4 model runs of salinity concentration
for Intracoastal system.

Embayment Division m2 sec
Discharge 2.0
Marsh Channel 15.0
Marina Channel 15.0
Marsh Plain 15.0
IAWW 15.0
Contour plots of the modeled salinities are presented in Figures 14 and 15, the
color contours indicate salinity concentrations throughout the model domain. Though
model dispersion coefficients were not rigorously calibrated, the model approximates
salinity gradients in the waterways.
22

~~C~9ii~
DCM V~II~MIi~lGTO~~~. i~~v

Figure 14. Contour plots of modeled salinity concentrations (ppt) in IAWW, for water treatment
discharge of 2.0 MGD.
Figure 15. Contour plots of modeled salinity concentrations (ppt) in IAWW, for water treatment
discharge of 2.0 MGD.
23

~JCfv14~lILMINGTQ~~~. NC
J1)L ~ 1 2006
~.
Figure 16. Example of hydrodynamic model output for a single time step where maximum flood
velocities occur for this tide cycle. Color contours indicate velocity magnitude, and
vectors indicate the direction of flow.
Figure 17. Example of hydrodynamic model output for a single time step where maximum ebb
! velocities occur for this tide cycle. Color contours indicate velocity magnitude, and
vectors indicate the direction of flow.
25

R~CE1V~~
~3CM ~JVI! MI~!GTn~1. NU
JUI_. 3 1 200
5. CONCLUSIONS
The goal of this study was to examine the influence of the discharge from the
New Hanover County Water Treatment ,Plant upon the salinity in the Intracoastal
Waterway and the surrounding salt marsh. The final calibrated models serve as a useful
tool for evaluating the circulation, variation in flow patterns, and the diffusion of the
discharge water into the surround environment.
Magnitude of flow passing by the "Figure 8" Island Bridge over the tidal cycle is
orders of magnitude greater than the proposed discharge from the water treatment plant.
The 2.0 MGD of discharge from the water treatment plant equates to 3.09 ft3/s of flow
being emitted into the Intracoastal Waterway compared to the average tidal flows of
3,500 to 4,500 ft3/s passing through the channel at the bridge. Therefore, the effect of
the diffuser on regional hydrodynamics is negligible. Contour plots of the flow velocities
in the vicinity of the "Figure 8" Island Bridge are shown in Figures 16 and 17. The model
run shows flood velocities in the channels are slightly larger than velocities during
maximum ebb. At no time did the simulations of the diffuser indicate changes to existing
tidal flow patterns.
Dissipation of the discharge from the water treatment plant begins immediately in
the diffusion model. Once the discharge is subject to the tidal flows in the channel,
mixing begins and the salinity increases rapidly to background conditions. The areas of
salt marsh are unaffected by the reduced salinity due to the flow patterns keeping the
discharge largely constrained to the channel. The tidal flow along the Intracoastal
Waterway mixes with the discharge rapidly and raises the concentration to within or
above 99-percent (34.8 ppt) of the ambient rate within 500 feet of the diffuser. With the
rapid dilution and persistent tidal flows in the area of the "Figure 8" Island Bridge, the
diffuser will have minimal influence upon the surrounding salinity regime. The modeling
does not present any indication that the low salinity discharge from the outfall will have
any adversely impacts to the Intracoastal Waterway bordering salt marsh systems.
24

R~C~~V~r~
~CIU1 VViLMlP~1GT~,V. N

7. REFERENCES
Brigham Young University (1998). "User's Manual, Surfacewater Modeling System."
Chow, V. T. (1959). Open Channel Hydraulics, McGraw-Hill, NY.
Dyer, K.R. (1997). Estuaries, A Physical Introduction, 2"d Edition, John Wiley & Sons,
NY, 195 pp.
Fischer, H.B., E.J. List, R.C.Y. Koh, J. Imberger, and N. H. Brooks (1979). Mixing in
Inland and Coastal Waters. Academic Press, Inc., Saan Diego, CA, 483 pp.
Kelley, Sean. (2003). "Mason Inlet and Middle Sound System New Hanover County,
North Carolina, Hydrodynamic and Sediment Transport Analyses of Present
Conditions and Dredging Alternatives." Applied Coastal Research and
Engineering, Inc.
King, Ian P. (1996). "Users Guide to RMA2 Version 4.2." US Army Corps of Engineers
- Waterways Experiment Station Hydraulics Laboratory.
King, Ian P. (1990). "Program Documentation -RMA2 - A Two Dimensional Finite
Element Model for Flow in Estuaries and Streams." Resource Management
Associates, Lafayette, CA.
Lindeburg, Michael R. (1992). Civil Engineering Reference ~Aanu~a!, Sixth Edition.
Professional Publications, Inc., Belmont, CA.
Norton, W.R., I.P. King and G.T. Orlob (1973). "A Finite Element Model for Lower
Granite Reservoir", prepared for the Walla Walla District, U.S. Army Corps of
Engineers, Walla Walla, WA.
Ramsey, J. and T. Ruthven. (2003). "Hydrodynamic Analysis of Hog Marsh and Poplar
Island Cell 3D." Applied Coastal Research and Engineering, Inc.
Van de Kreeke, J. (1988). "Chapter 3: Dispersion in Shallow Estuaries." In:
Hydrodynamics of Estuaries, Volume I, Estuarine Physics, (B.J. Kjerfve, ed.).
CRC Press, Inc. pp. 27-39.
Zimmerman, J.T.F. (1988). "Chapter 6: Estuarine Residence Times." In:
Hydrodynamics of Estuaries, Volume I, Estuarine Physics, (B.J. Kjerfve, ed.).
CRC Press, Inc. pp. 75-84.

26