NC0085359_Engineering Alternatives Analysis_20100816

NPDES DOCYNENT SCANNING COVER SHEET
NPDES Permit:
NC0085839
Twelve Mile Creek WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
August 16, 2010
Miss documerit ism priiited on reu511e paper - ignore any
content on the re'rerg se side

HAZEN AND SAWYER
Environmental Engineers & Scientists
August 16, 2010
Mr. Tom Belnick, Supervisor
Complex Permitting Unit
Surface Water Protection Section - NPDES
Division of Water Quality
N.C. Department of Environment and Natural Resources
512 North Salisbury Street
Raleigh, North Carolina 27604
Dear Mr. Belnick:
‚ve
Hazen and Sawyer, P.C.
4944 Parkway Plaza Blvd.
Suite 375
Charlotte, NC 28217
17041357-3150
1704) 357-3152 (Fax)
64(
Re: Expansion Alternatives Development Study
Twelve Mile Creek WWTP
Union County, Nort
NPDES Permit N
aro
NC0085359
Please find attached three (3) copies of the Expansion Alternatives Development Study for
Union County's Twelve Mile Creek Wastewater Treatment Plant (WWTP). This study was
referenced at our meeting on June 8th, 2010 and in recent conversations between your office
and the County. If you could distribute a copy each to Mr. Jeff Poupart and to Mr. Chuck
Wakild, we would appreciate it. We are also sending copies to Mr. Rob Krebs and Ms. Donna
Hood at the Mooresville Regional Office.
Thank you for your assistance on this project and we look forward to further discussions. If you
have any questions or would like additional information, please do not hesitate to contact me at
704-357-3150 or at jstruve(cr�hazenandsawyer.com.
Very truly yours,
HAZEN AND SAWYER, P.C.
-n.
James N. Struve, P.E.
Vice President
cc: Mr. Ed Goscicki, Union County Public Works
Mr. Scott Huneycutt, Union County Public Works
Mr. Scott Alpert, Hazen and Sawyer
Attachment.
Teelnick 081610 Itr
New York, NY • Philadelphia, PA • Raleigh, NC . Charlotte, NC Greensboro, NC • Greensboro, NC • Charleston, SC • Atlanta, GA . Fairfax, VA Hampton Roads, VA • Baltimore, MD • Cincinnati, OH • Hollywood, FL • Boca Raton, FL • Miami, FL

TECHNICAL MEMORANDUM
PREPARED FOR: Union County Public Works
Union County, North Carolina
PREPARED BY: Hazen and Sawyer, P.C.
Jim Struve, PE; Scott Alpert, PhD, PE; Julie Doll, PE
DATE: August 2, 2010
SUBJECT:
Twelve Mile Creek Wastewater Treatment Plant
Expansion Alternatives Development Study
Task Order No. 28
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DISTRIBUTION: Union County Public Works
Ed Goscicki, PE; Scott Huneycutt, PE; Mark Tye; John Hahn
Introduction
The Twelve Mile Creek Wastewater Treatment Plant (WWTP) is currently rated for treatment of a
maximum month flow rate of 6 million gallons per day (MGD). The plant's liquid treatment process
consists of screening and grit removal, advanced secondary treatment for BOD, nitrogen, and
phosphorus removal, secondary clarification, filtration, UV disinfection, and cascade aeration prior to
discharge into Twelve Mile Creek. Solids treatment includes gravity belt thickening and aerobic
digestion with final biosolids disposal onto permitted agricultural farmland.
Currently, the Twelve Mile Creek WWTP treats approximately 3.3 MGD with a maximum month flow of
3.72 MGD. Union County (County) has expressed concern that the remaining plant capacity will be
quickly consumed once the economy improves and the housing market rebounds. The North Carolina
Department of Environment and Natural Resources' (NCDENR's) Division of Water Quality (DWQ) has
previously indicated that the permitting of additional discharge into Twelve Mile Creek is unlikely
because of upstream and downstream dissolved oxygen (DO) concentrations below 5.0 mg/L.
To avoid a shortage of wastewater capacity in the near future, alternatives for expansion of the Twelve
Mile Creek WWTP and/or disposal of wastewater generated in southwestern Union County need tp-be_
i�—
developed and evaluated. The objective of the Expansion Alternatives Development Study is to pr vii
the County with the required information to shortlist the alternative(s) that could be further refine
developed to cost-effectively provide approximately 3 MGD of additional capacity at the Twelve Mile o
` N
Creek WWTP. -
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
-1-
H ZE1\ AND W1 rR
Environmental Engineers 8 Scientists

Expansion and Disposal Alternatives
The County and Hazen and Sawyer have previously met with NC DWQ and the South Carolina
Department of Health and Environmental Control (SCDHEC) to discuss a proposed expansion of the
' Twelve Mjle Creek WWTP. These meetings confirmed that a new permit for additional discharge to
Twelve Mile Creek (Creek) is highly unlikely based on the apparent lack of assimilative capacity for
oxygen -demanding wastes in the Creek. As such, alternative disposal and/or treatment options will
need to be developed for future wastewater treatment capacity in this service area. As part of the
current study, six alternatives have been developed and are listed below:
• Alternative 1: Buy Additional Capacity at Charlotte Mecklenburg Utilities' (CMU's) McAlpine
Creek Wastewater Management Facility (WWMF)
• Alternative 2: Build and Buy Capacity at Lancaster County (SC) Water and Sewer District's
(LCWSD's) Indian Land WWTP
• Alternative 3: Partner with LCWSD to Build a New WWTP
• Alternative 4: Develop a Non -Conjunctive Reuse System
• Alternative 5: Discharge Additional Plant Effluent into Twelve Mile Creek
• Alternative 6: Pump Additional Plant Effluent to the Catawba River
Each of these alternatives was evaluated based on cost, constructability, permitting, schedule, and
feasibility. These alternatives are discussed in detail in this section.
Alternative 1: Buy Additional Capacity at the McAlpine Creek WWMF (Charlotte -Mecklenburg
Utilities)
As part of Alternative 1, the County would negotiate with Charlotte -Mecklenburg Utilities to buy additional
treatment capacity at the McAlpine Creek WWMF. The County currently holds a contract with CMU that
defines a total treatment allocation of up to 3 MGD at the McAlpine Creek WWMF, under which the
current financed capacity by the County is 1 MGD. However, the County has exceeded the 1 MGD of
purchased capacity and has reached a maximum month flow of 1.3 MGD. As such, the County has
requested and received approval from CMU for an additional 1.7 MGD of flow from the proposed
Diversion Force Main and Pump Station. Thus, Alternative 1 would require an agreement with CMU for
an additional 3 MGD of treatment capacity (i.e., 1.3 MGD current flow + 1.7 MGD of recently approved
flow + 3.0 MGD of additional flow for this alternative = 6 MGD total flow). Capital improvements required
for this alternative include:
• Expansion of the proposed Diversion Pump Station, or construction of a new parallel pump
station at the Twelve Mile Creek WWTP, to convey an additional 3 MGD to the Six Mile Creek
Interceptor. Conversations with the design engineers of the Diversion Pump Station (Kimley-
Horn) indicated that the Diversion Pump Station as designed could be expanded to 9 MGD by
replacement of the proposed pumps with those rated for higher flow rates. However, the
Twelve Mile Creek WWTP Expansion Alternatives - 2 -
August 2010
HAM AND SOWER
Environmental Engineers & Scientists

tirg
fat
proposed total dynamic head (TDH) characteristics of the pumps for the existing/proposed force
main between the Plant and the Six Mile Creek Interceptor are such that Kimley-Horn
determined that expansion above 3 MGD would require the construction of an intermediate
,At\ pump station approximately half -way along the force main route.
• Potential construction of a new parallel force main between the Twelve Mile Creek WWTP and
Six Mile Creek Interceptor. As described in the bullet above, the proposed Diversion Pump
Station force main that connects to an existing force main could likely convey an additional 3
oc\ MGD; however, the static head and friction losses may be such that an intermediate pump
station and/or parallel force main may be required.
411LN • Potential expansion of the existing Six Mile Creek Pump Station and parallel force main from the
Six Mile Creek Pump Station to the 30-inch McAlpine Tributary No. 1A gravity sewer. According
to CMU, the existing Six Mile Creek Pump Station is undergoing an expansion to meet the peak
'ck) flows (up to 15 MGD) currently being experienced at the pump station. After expansion, the
pump station will be rated for a firm peak flow of 18 MGD. According to the PER originally
,la\ written for the pump station, the force main downstream of the pump station is rated for 20
MGD. This force main is relatively short and connects to a series of gravity sewers that convey
flow to the McAlpine Creek WWMF. However, CMU was uncertain as to the hydraulic capacity
of these gravity pipelines and of the Six Mile Creek Interceptor upstream of the pump station.
A site plan showing the Twelve Mile Creek WWTP and the route of the force main to the Six Mile Creek
Interceptor is shown in Figure 1. Additional analysis would need to be performed to evaluate the
available capacity of the Six Mile Creek Interceptor, the Six Mile Creek Pump Station, and the force main
and gravity sewer piping between the Six Mile Creek Pump Station and the McAlpine Creek WWMF.
For the purposes of this alternatives evaluation, it is assumed that a new pump station would need to be
esit constructed either at the Twelve Mile Creek WWTP or as an intermediate station as described by
,RN Kimley-Horn, and that the Six Mile Creek Pump Station and the gravity and pressure pipelines upstream
and downstream have available capacity for an additional 3 MGD. Should this latter assumption be
estN
proved incorrect by a more detailed study, the design and construction of parallel infrastructure could be
complex and expensive, especially since it would involve infrastructure additions in both Union and
Mecklenburg Counties.
elit)
In addition, it is likely that the McAlpine Creek WWMF, currently rated for 64 MGD, would need to be
expanded to handle additional flow from the County. The flows at the McAlpine Creek WWMF have
eaN
averaged 48.8, 54.6, 54.8, and 59.2 MGD in each month between November 2009 and February 2010.
These latest flow rates are during wet winter months, but it is apparent that the flows are approaching
plant capacity. Additional capacity at McAlpine Creek WWMF may become available when CMU's
proposed Long Creek WWTP is online; however, the new plant will not be complete until at least the
year 2015, which may be too distant to be feasible as an alternative for this study. The next planned
expansion of the McAlpine Creek WWMF would not be scheduled until decisions about the Long Creek
egiN WWTP are complete.
tsaN
,ffit1 Twelve Mile Creek WWTP Expansion Alternatives - 3 - HAZEN AND SA!,y.ERAugust2010 1Environmental Engneers 8 SScilentists

Six Mile Creek Pump Station
1 Parallel Gravity Sewer
MARV/
FIGURE 1
Alternative 1 -
Buy Additional Capacity at CMU's McAlpine Creek WWMF
Proposed Parallel Force Main
Twelve Mile Creek WWTP
JIM W11'SON Ro
New/Expanded
Diversion Pump Station
0
cuTwaeRTSc �
Force Main
- Road
Stream
3.000 6,000
HAZENAND SAWYER
Enviranmental Engineers & Scientists

The current contract between the County and CMU, signed in 1996, defines the County's total treatment
allocation as 3 MGD at the McAlpine Creek WWMF. This flow rate, as mentioned previously, has been
approved by CMU for total flow from the County. Thus, any additional flow to the plant from the County
would require a new contract or a contract amendment. As a reference for a potential new contract,
other key items from the current agreement between the City of Charlotte and Union County include:
rAt
• The 1996 County "Financed Treatment Capacity" was 1 MGD. This value is defined as the
amount of capacity to treat wastewater, the funding for which is financed by the County,
including the outfall expansion and plant expansion projects. The maximum amount of the
County Financed Treatment Capacity is the County Treatment Allocation.
• The County Treatment Allocation from the 1996 Agreement is 3 MGD and is defined as the
number of gallons of wastewater, expressed as a daily average and calculated over the course
of a calendar month, which the County is authorized to discharge regularly in the Outfall Project.
• A notification of intent to increase the County Financed Treatment Capacity (currently defined as
extN 1 MGD) must be requested prior to the average annual flow at the McAlpine Creek WWMF
reaching 51.2 MGD with further limitations at a flow rate of 57.6 MGD.
• The County shall share the Six Mile Creek Pump Station power costs.
• As of July 1, 2008, the County would be billed $0.73 per 1,000 gallons (up to 1 MGD) for
treatment at the McAlpine Creek WWMF.
▪ The Outfall Project (ca. 1997) consisted of a force main with capacity of 18 MGD, pump station
with capacity of 6 MGD, and the Outfall with capacity of 12 MGD.
eiLN • The County average daily wastewater discharge from every County sewer line discharging into
the Outfall, calculated over the course of a calendar month, will not exceed the County
Treatment Allocation.
• The volume of wastewater from the County discharging into the Outfall will be measured by
metering facilities installed by the County and operated/maintained by the City.
• The County pays one -sixteenth (1/16) of the project costs associated with the 1996-1997 Outfall
ese, Project and for the expansion of the McAlpine Creek WWMF from 48 MGD to 64 MGD.
• If the County proposes at any time to increase the County Financed Treatment Capacity, the
Director of CMU will provide the County with the schedule of debt service payments on such
costs required for improvements to the WWMF:
o For an increase in the County Financed Treatment Capacity using the project costs of
the plant expansion from 48 MGD to 64 MGD, the County's share of the costs shall be
based upon a fraction defined by a numerator equal to the increase in the County
Financed Treatment Capacity and by a denominator of sixteen (16) MGD.
o For an increase in the County Financed Treatment Capacity using the project costs of a
rAN subsequent plant expansion at the McAlpine Creek WWMF, the County's share of the
costs shall be based upon a fraction defined by a numerator equal to the increase in the
County Financed Treatment Capacity and by a denominator equal to the difference
between the total treatment capacity after the plant expansion and the total treatment
fietN
capacity immediately prior to the plant expansion. Relevant project costs include those
Twelve Mile Creek WWTP Expansion Alternatives - 5 - HAM AND SAYERAugust 2010 Enviromental Engineersrs&Scientists
elk\
eaN

associated with the Outfall and Outfall pump station expansion.
• The County may give the Director of CMU written notice at any time of the County's intent to
increase the County Financed Treatment Capacity (provided that it does not exceed the County
Treatment Allocation and that McAlpine Creek WWMF average daily flow does not exceed 51.2
MGD). The County's share of costs for an increase in the County's Financed Treatment
Capacity shall also be based on costs associated with the Outfall and Outfall pump station
project.
Estimated capital costs and key operating costs for Alternative 1 are shown in Table Nos. 1 and 2. The
capital cost estimate assumes that a new pump station will need to be constructed either at the Twelve
Mile Creek WWTP or at an intermediate location between the treatment plant and the Six Mile Creek
Interceptor. The capital costs for the pump station (and all new and expanded pump stations considered
in other alternatives) are based on a unit cost per gallon that is consistent with previous projects
designed by Hazen and Sawyer. As described above, it is assumed that the interceptor, the Six Mile
Creek Pump Station, and the existing downstream force main and gravity sewer have sufficient capacity
to handle an additional 3 MGD. The cost per gallon to expand the McAlpine Creek WWMF is estimated
based on the construction costs of the expansion of the plant from 48 MGD to 64 MGD and the follow-up
related projects for reliability and regulatory compliance. A future expansion at the McAlpine Creek
WWMF would likely increase rated capacity from 64 MGD to 80 MGD, and, for the purposes of this
evaluation, the County would request a financed allocation of 3 MGD. The treatment costs at the
McAlpine Creek WWMF, shown in Table 2, are based on a letter from CMU (July 2008) describing the
unit cost to be billed to Union County. The pump head required to pump from the Twelve Mile Creek
WWTP to the Six Mile Creek Interceptor is estimated based on approximate static and friction losses.
The pump head for the Six Mile Creek Pump Station is based on the characteristics of the pump
currently installed.
Twelve Mile Creek WWTP Expansion Alternatives - 6 -
August 2010
HAZEN AND SOUR
Environmental Engineers & Scientists

.4111,
wileN
Table 1: Estimated Capital Costs — Alternative 1
Description
Capital Cost Estimate
Union County Infrastructure
New or Expanded Diversion Pump Station (3 MGD @ $1/Gal)
$3,000,000
18-in Force Main (38,000 LF) to Six Mile Creek Interceptor
$6,840,000
Category Subtotal
$9, 840, 000
Infrastructure in Mecklenburg County
Parallel 36-in Gravity (0 LF) to Six Mile Creek Pump Station
$0
Six Mile Creek Pump Station Expansion
$0
Parallel 24-in FM (0 LF) from PS to McAlpine Interceptor
$0
(Assume existing infrastructure has sufficient capacity.)
Subtotal
$0
County Percentage
100%
Category Subtotal
$0
McAlpine Creek WWMF Expansion
Construction (at $5.00 per Gal) (Expand from 64 to 80 MGD)
$80,000,000
County Percentage (3 of 16 MGD = 3/16)
19%
Category Subtotal
$15.000,000
Subtotal 1
$24, 840, 000
Contingencies (25% of Subtotal 1)
$6,210,000
Subtotal 2
$31,050,000
Contractor OH / Profit (10% of Subtotal 2)
$3,105,000
Mobilize / Demobilize (1.5% of Subtotal 2)
$465,750
Insurance / Bonds (1.5% of Subtotal 2)
$465,750
TOTAL
$35,086,500
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
-7-
HAZEN AND SAWY1R
Environmental Engineers i Scientists

Table 2: Estimated Key O&M Costs — Alternative 1
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to Six Mile Creek Interceptor)
Head (ft)
200
Flow (MGD)
3
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
981,892
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$58,914
Pumping Costs at Six Mile Creek Pump Station
Head (ft)
185
Flow (MGD)
3
Efficiency (%)
70
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
908,250
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$54,495
County Portion
100%
Subtotal
$54,495
Treatment Cost at McAlpine Creek WWMF
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$0.73
Treatment Costs ($/Yr)
$799,350
Total Key Annual O&M Costs $912,800
Alternative 2: Build and Buy Capacity at the Indian Land WWTP (LCWSD)
For this alternative, the County would partner with Lancaster County (SC) Water and Sewer District to
build and buy treatment capacity at the Indian Land WWTP. The Indian Land WWTP is a 2 MGD
advanced secondary treatment facility constructed in 2001 to serve the Indian Land community of
Lancaster County. Treated effluent from the Indian Land WWTP is ultimately discharged into the
Catawba River. To accommodate 3 MGD from Union County, the Indian Land WWTP would need to be
expanded. In addition, capital improvements would include the construction of a new pump station at
the Twelve Mile Creek WWTP to convey up to 3 MGD to the Indian Land WWTP. This pump station
could be integrated into the design of the proposed Diversion Pump Station such that one wet well is
shared but pumps are dedicated individually for flow to either CMU or LCWSD. Alternative 2 would also
require a new force main between the Twelve Mile Creek WWTP and the Indian Land WWTP, an
Twelve Mile Creek WWTP Expansion Alternatives - 8 -
August 2010
HAM AND SOUR
Environmental Engineers 8 Scientists

example route for which is shown in Figure 2. Capital cost estimates for Alternative 2 are shown in
Table 3 and key O&M costs in Table 4. The capital cost for expansion of the Indian Land WWTP is
estimated at a unit cost of $7 per gallon, which corresponds to the calculated cost for expansion of the
Twelve Mile Creek WWTP (as detailed later in this report). For the pumping energy costs, the required
pump head was estimated using the approximate static and friction losses for the force main route
shown in Figure 2. The treatment costs for the Indian Land WWTP are based on the estimated unit
costs at the Twelve Mile Creek WWTP.
Conversations with SCDHEC revealed that the Indian Land WWTP has, in place, approved NPDES
permits for expansion of flow up to 15 MGD. Separate permit limits have been established for a phased
approach in expansion with total design flows of 1.2, 2.0, 4.0, 7.5, and 15 MGD. However, the approved
208 Water Quality Management Plan does not explicitly state that LCWSD can accept wastewater flows
generated within the State of North Carolina. Thus, the 208 Plan will need to be amended/modified,
which is initiated through a letter of intent outlining an agreement that LCWSD is willing to accept flows
from Union County. The letter must also indicate that other alternatives were evaluated and that this
alternative was recommended. A 30-day public notification period for public comment will also be
required once the 208 Amendment has been accepted by SCDHEC. Then, construction permits could
be issued for the force main (within South Carolina) and the treatment plant expansion. DWQ would still
need to approve that portion of the force main within North Carolina.
Table 3: Estimated Capital Costs — Alternative 2
Description
Capital Cost Estimate
Union County Infrastructure
Raw Sewage Pump Station at Twelve Mile Creek WWTP (3 MGD @ $1/Gal)
$3,000,000
18-in DIP Force Main (36,250 LF) to Indian Land WWTP
$6,525,000
Category Subtotal
$9, 525, 000
Indian Land WWTP Expansion
Construction (at $7.00 per Gal) (Expand from 2 to 7.5 MGD)
$38,500,000
County Percentage (3 of 5.5 MGD = 3/5.5)
55%
Category Subtotal
$21,000,000
Subtotal 1
$30,525,000
Contingencies (25% of Subtotal 1)
$7,631,250
Subtotal 2
$38,156,250
Contractor OH / Profit (10% of Subtotal 2)
$3,815,625
Mobilize / Demobilize (1.5% of Subtotal 2)
$572,344
Insurance / Bonds (1.5% of Subtotal 2)
$572,344
TOTAL $43,116,600
Twelve Mile Creek WWTP Expansion Alternatives - 9 -
August 2010
HAZEN AND ► AWER
Environmental Engineers & Scientists

Table 4: Estimated Key O&M Costs - Alternative 2
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to Indian Land WWTP)
Head (ft)
180
Flow (MGD)
3
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
883,703
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$53,022
Treatment Cost at Indian Land WWTP
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$2.00
Treatment Costs ($/Yr)
$2,190,000
Total Key Annual O&M Costs $2,243,000
Twelve Mile Creek WWTP Expansion Alternatives - 10 -
August 2010
HAZ N AND ► WER
Environmental Engineers & Scientists
rek
rok
Oft
r
et -
I~
Aim

Indian Land WWTP
Proposed Force Main
FIGURE 2
Alternative 2 -
Build and Buy Capacity at LCWSD's Indian Land WWTP
Twelve Mile Creek WWTP
New
Pump
Station
Legend
■ WWTP
Force Main
- Road
Stream
3.000 6,000
HAZEN AND SAWYER
Env irsnmentalEnginests & Scientists
— L

Alternative 3: Partner with LCWSD to Build a New Wastewater Treatment Plant
Alternative 3 requires a partnership with LCWSD to construct a new WWTP to serve portions of both
Union and Lancaster Counties. Both counties would need to develop appropriate service areas and
identify a location for this new treatment plant. This treatment plant would ultimately discharge into the
Catawba River. The complexities involved in permitting a new wastewater plant, especially for a plant
jointly owned by counties in two states, could result in a lengthy design and construction process.
An example location for a new treatment plant is shown in Figure 3, which includes a potential force
main route from the Twelve Mile Creek WWTP to the new plant. The proposed location of the new plant
was estimated based on the following:
• Wastewater generated in Lancaster County south of Highway 5 is transferred to the City of
Lancaster's wastewater treatment facility.
• The Indian Land WWTP serves the northern portion of Lancaster County.
• SCDHEC has previously declined to give speculative permit limits for a new discharge into
Twelve Mile Creek between the NC/SC state line and the Catawba River.
Capital and key O&M cost estimates for Alternative 3 are shown in Table 5 and Table 6, respectively.
The unit cost for construction of the new plant is higher than that of the expansion of the Indian Land
WWTP to account for additional costs associated with a new facility, such as site grading and clearing,
administration facilities, land purchases, etc. For key O&M costs, pumping head was estimated based
on approximate static and friction losses, and the treatment unit cost was set equal to that used for the
Indian Land WWTP.
Twelve Mile Creek WWTP Expansion Altematives - 12 -
August 2010
WIN AND SOUR
Environmental Engineers & Scientists

Table 5: Estimated Capital Costs — Alternative 3
Description
Capital Cost Estimate
Union County Infrastructure
Raw Sewage Pump Station at Twelve Mile Creek WWTP (3 MGD @ $1/Gal)
$3,000,000
18-in DIP Force Main (49,200 LF) to New Plant
$8,856,000
Category Subtotal
$11,856,000
New Treatment Plant Construction
Construction (6 MGD at $8.00 per Gal) (New 6 MGD Plant)
$48,000,000
County Percentage (3 of 6 MGD = 3/6)
50%
Category Subtotal
$24,000,000
Subtotal 1
$35,856,000
Contingencies (25% of Subtotal 1)
$8,964,000
Subtotal 2
$44, 820, 000
Contractor OH / Profit (10% of Subtotal 2)
$4,482,000
Mobilize / Demobilize (1.5% of Subtotal 2)
$672,300
Insurance / Bonds (1.5% of Subtotal 2)
$672,300
TOTAL $50,646,600
Table 6: Estimated Key O&M Costs — Alternative 3
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to New WWTP)
Head (ft)
200
Flow (MGD)
3
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
981,892
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$58,914
Treatment Cost at New WWTP
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$2.00
Treatment Costs ($/Yr)
$2,190,000
Total Key Annual O&M Costs $2,248,900
Twelve Mile Creek WWTP Expansion Alternatives - 13 -
August 2010
HAZEN AND S4\WER
Environmental Engineers & Scientists

Twelve Mile Creek WWTP
0 Dobys Bridge
a
Proposed Force Main
Pinehil
mlel
walterS
Honcho
Proposed WWTP
atm
State Highway 3 • O�
FIGURE 3
Alternative 3 -
Partner with LCWSD to Build New WWTP
Cis PINE OPK
New
Pump
Station
KENStd-
Legend
■ WWTP
CCALL
FALL
Force Main
-- Road
Stream
Envirsnmental Engineers & Scientists

1
egt
1
occaN
Alternative 4: Develop a Non -Conjunctive Reuse System
Alternative 4 focuses on developing a non -conjunctive reuse system to land apply final treated effluent
from the Twelve Mile Creek WWTP onto suitable and available land within the vicinity (3 to 6 mile radius)
of the Plant. To achieve this objective, the County would need to identify potential end users, such as
developers and farmers, that would benefit from a reliable source of irrigation water for landscaping and
agricultural crops. In addition, this alternative would require:
• Expansion of the Twelve Mile Creek WWTP and installation of flow equalization and final effluent
storage necessary for a reuse system.
• Construction of effluent conveyance facilities from the Plant to the land application site(s).
• Development of reclaimed water ordinances, standards, guidelines, and details.
raN The Land Application Unit of DWQ describes "non -conjunctive reuse" as a wastewater treatment system
that relies on reclaimed water uses to account for all of the generated wastewater (i.e., zero direct
discharge to a surface water). As such, additional requirements are imposed to address system
reliability in permitting a non -conjunctive system. Further, since the generated reclaimed water must be
continuously discharged through the land application system (or stored for future land application), the
County would be dependent on others (i.e., agricultural and development land owners) to accept the
L 1 treated wastewater. Thus, Tong -term contracts would need to be pursued. Alternatively, the County
could purchase the land application site(s) to maintain control. However, these purchases would
significantly increase the cost of this option and the County would be responsible for maintenance of the
property.
Discussions with DWQ indicate that a seasonal discharge permit could be considered for a Twelve Mile
,ate Creek WWTP reuse system. In this tiered approach, the non -conjunctive reuse would be required
during the warm weather months when stream flow is low, but discharge to Twelve Mile Creek would be
allowed during the winter months when stream flows are high. This approach still requires the
infrastructure that would be necessary for a full-time non -conjunctive system. However, the treated
effluent storage requirements could be reduced since stream discharge will be allowed during wet
weather months when most of the storage would be needed.
eArN
For a flow rate of 3.0 MGD and an average land application rate of 1-inch per week, the wetted area
eaN
required equals 774 acres. If it is assumed that after subtracting stream buffers, property line buffers,
r steep slopes, etc., approximately 60% of a dedicated reuse property is irrigable, a total land area of
1,290 acres would be required for land application. The other significant land use for this option would
be the area necessary for treated wastewater storage. Since a design flow rate of 3 MGD would need to
be land applied and application would not be allowed during wet weather periods, thirty (30) days of
storage (or 90 MG) would be recommended if a seasonal discharge permit is not obtained. A seasonal
discharge permit may allow reduction of this storage to approximately ten (10) days, or 30 million
gallons. For either size, an earthen storage basin would likely be the most cost-effective option, but
�1 Twelve Mile Creek WWTP Expansion Alternatives -15 - RAM AND
August 2010 SVY.EREnvironmental Engineerss & Scientists
e

would be land -intensive with the 90-million-gallon reservoir occupying a footprint of approximately 20
acres. Locating over 1,300 acres near the Twelve Mile Creek WWTP that are available for irrigation and
storage will be a challenge.
Figure 4 shows several large contiguous tracts of land that could be considered for reuse/land
application within approximately seven miles of the Twelve Mile Creek WWTP. The proposed force
mains to convey treated effluent to these sites are also shown. Note that these properties were selected
based on their size, zoning classification, and proximity to the treatment plant. No detailed
investigations have been performed as to the suitability of the land for application or to the availability of
the properties. A location for the large effluent storage reservoir has not been selected, but for the
purposes of this evaluation, it is assumed that one or more reservoirs could be located at the application
sites.
In 2005, a Preliminary Engineering Report (PER) was prepared for the County for a potential reuse
system at the Twelve Mile Creek WWTP (HDR, 2005). This PER was written at a time when population
and development growth was high within the County and in the Charlotte region. As such, the report
focused on a reuse system to help offset high potable water demands during the spring and summer
when residential irrigation and other demands peak. The PER did not consider the use of a reclaimed
water system as an alternative disposal for an increase in plant capacity, but rather for reuse benefits
such as sustainability, a diversion of normally -discharged effluent during the hot dry months when
stream flows are low and assimilative capacity is reduced, and offsetting additional demand on potable
water systems. The PER focused on the installation of water reuse infrastructure at the Twelve Mile
Creek WWTP and the potential reuse demand within a 2-mile radius of the plant. The following is a
bulleted summary of the PER findings:
• Two potential irrigation sites were selected, including a development adjacent to the plant owned
by GS Carolina Property (1,073 acres, of which 62 acres would be available for reuse irrigation)
and two unidentified tracts of land within a two mile radius of the plant totaling approximately
1,000 acres, of which an estimated 100 acres would be available for reuse irrigation.
• The PER reported that much of the rural and agricultural lands surrounding the treatment plant
have been rezoned for residential and commercial development, and that no significant feasible
industrial or agricultural reuse opportunities existed within the proposed reuse service area.
• The current plant effluent water quality would generally meet reuse requirements for monthly
average and daily maximum BOD5, TSS, and NH4-N concentrations. Additional disinfection
would be required to meet reclaimed water fecal coliform standards. The PER recommended
installation of a hypochlorite feed system both for meeting reclaimed fecal coliform standards
and for providing a disinfectant residual to prevent biological growth in the reuse water
distribution system.
• The average reclaimed water flow rate based on the identified properties was calculated as
630,000 GPD (0.63 MGD). The infrastructure would be designed to deliver this flow rate over an
Twelve Mile Creek WWTP Expansion Altematives - 16 -
August 2010
HAM AND StYER
Environmental Engineers & Scientists

%1
(AN
toiN
ex1
8-hour per day irrigation schedule, and distribution piping and reclaimed water pumps would be
`aA, sized for a peak demand of four times the average daily system design flow.
• Infrastructure additions at the plant would include:
evz4 o An effluent weir box, valve system, flow meter, and turbidimeter constructed upstream of
a ground storage system to allow bypass of the reclaimed water system if turbidity
approached 10 NTU
o A bulk filling station for non -potable water truck access
o Reuse pump stations
• Other recommendations included a County -wide reclaimed water master plan, cooperation with
the County Planning Department to educate developers, a public education and outreach
program, draft ordinance language supporting reuse, and design standards for reuse system
components (backflow prevention, pipe labeling, signage, etc.)
Table 7 describes the current regulations for reclaimed water in North Carolina.
151
earN
t
.,
eAltN
AstN
est)
Table 7: Summary of Reuse Regulations
Purpose
Utilization of tertiary treated wastewater effluent used in a beneficial manner and for the
purpose of conservation of the state's water resources by reducing the use of a water resource
(potable, surface, or ground water) [15A NCAC 02T .0901]
Effluent
Standards
• Monthly Avg BOD5 5 10 mg/L
o Daily Max BOD5 _5. 15 mg/L
• Monthly Avg TSS 5 5 mg/L
o Daily Max TSS 5 10 mg/L
• Monthly Avg NH3 5 4 mg/L
o Daily Max NH3 5 6 mg/L
• Monthly Geometric Mean Fecal Coliform 5 14/100 mL
o Daily Max Fecal Coliform 5 25/100 mL
• Turbidity 5 10 NTU
Design Criteria
(Non-
Conjunctive)
• Aerated flow equalization facilities with capacity of at least 25% of daily system design flow.
• Dual facilities for all essential treatment units.
• Continuous online monitoring for turbidity and flow.
• Five-day side -stream detention pond for effluent exceeding turbidity or fecal coliform levels.
• Automatically activated standby power supply onsite, capable of powering all essential
treatment units under design conditions.
• Minimum of 30 days of residual storage.
• Influent pump station that can meet peak flow with largest pump out of service, has standby
power, and has power failure and high water telemetry.
Beneficial
Utilization
Residential lawns, golf courses, cemeteries, parks, school grounds, industrial or commercial
site grounds, landscape areas, highway medians, roadways
Utilization
Requirements
• Public notification
• Record -keeping program
• Program of education and approval for all uses on property not owned by generator
• Program of routine review and inspection for all uses on property not owned by generator
• Land application of effluents must be on property controlled by the generator unless a
contractual agreement is provided.
Limitations
No irrigation of direct food chain crops
Other
Requirements
Setbacks, Operation and Maintenance Plan, Residuals Management Plan
Twelve Mile Creek WWTP Expansion Alternatives - 17 -
August 2010
EA7EN AND SAWYFR
Environmental Engineers & Scientists

FIGURE 4
Alternative 4 -
Development of a Non -Conjunctive Reuse System
Legend
■ WWTP
oft
t^
Oft
t0/4
Oft
ttttrrrtr. Force Man
Road
Stream
Pcl Potential Reuse Parcels
0 3.000 6,000
Feet
HAZEvAND SAWYER
Environmental Engineers & Scientists
ook

fiszs
EARN
As of April 2010, NC DWQ and the Environmental Management Commission (EMC) were considering
EARN revisions to the reclaimed water rules. The major changes associated with the proposed rules are the
establishment of two classes of reclaimed water with stricter microbiological and physical limits for a
EARN defined Class A water that is intended for indirect contact irrigation for food chain crops that will not be
peeled, skinned, cooked, or thermally processed prior to consumption.
EARN
Estimated capital and key O&M costs for a 3 MGD non -conjunctive reuse system at the Twelve Mile
ER` Creek WWTP are shown in Table 8 and Table 9, respectively. Details concerning the expansion of the
Twelve Mile Creek WWTP for Alternatives 4, 5, and 6 are described in a later section. The cost for
EARN treatment at the Twelve Mile Creek WWTP is estimated at $2.00 per 1,000 gallons based on
communications with County staff. The pump head values for both the systems described in Table 9
EAN
were estimated based on approximate static head and friction losses.
tiaN
fAt
reAt
rotN
r
eabN
eabN
Twelve Mile Creek WWTP Expansion Alternatives - 19 -ilk\ HVEN AND SWVERAugust 2010 &Environmental Engineers 8
Scientists
1
tgrz

Table 8: Estimated Capital Costs — Alternative 4
Description
Capital Cost Estimate
Twelve Mile Creek WWTP Expansion
Influent Pumping, Coarse Screening, and Flow Equalization
$6,500,000
Preliminary Treatment Facility
$1,500,000
Biological (Secondary) Treatment
$5,810,000
Tertiary Filtration, Disinfection, and Post Aeration
$2,088,000
Sludge Thickening, Digesters, and Sludge Storage
$5,000,000
Odor Control
$2,000,000
Standby Power
$1,000,000
Category Subtotal
$23, 898, 000
Reuse Infrastructure
5-Day Onsite Storage (15 MG @ $0.15/Gal)
$2,250,000
Return Pump Station (1 MGD @ $1/Gal)
$1,000,000
Reuse Pump Station (WWTP to Eq Storage) (3 MGD @ $1/Gal)
$3,000,000
Equalization Storage Reservoir (90 MG @ $0.15/Gal)
$13,500,000
Effluent Pump Station (Eq Storage to Fields) (3 MGD @ $1/Gal)
$3,000,000
Additional Disinfection System
$400,000
Irrigation Land (1,285 acres @ $50,000/acre)
$64,250,000
Category Subtotal
$87,400,000
Piping
18-in DIP Force Main (83,500 LF) from WWTP to Eq Reservoir*
$15,030,000
24-in DIP Force Main (2,000 LF) from Eq Reservoir to Irrigation Sites
$480,000
Category Subtotal
$15,030,000
Subtotal 1
$126,328,000
Contingencies (25% of [Subtotal 1 minus land cost])
$15,519,500
Subtotal 2
$141,847,500
Contractor OH / Profit (10% of [Subtotal 2 minus land cost])
$7,759,750
Mobilize / Demobilize (1.5% of [Subtotal 2 minus land cost])
$1,163,963
Insurance / Bonds (1.5% of [Subtotal 2 minus land cost])
$1,163,963
TOTAL
Total without estimated purchase cost of irrigation land
$151,935,200
$87,685,200
'Assume equalization reservoirs are located at irrigation sites shown in Figure 4.
Twelve Mile Creek WWTP Expansion Alternatives - 20 -
August 2010
HiZE AND ► t % 1 ER
Environmental Engineers 8 Scientists

Table 9: Estimated Key O&M Costs — Alternative 4
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to Flow Equalization Reservoirs)
Head (ft)
215
Flow (MGD)
3
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
1,055,534
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($lYr)
$63,332
Pumping Costs (from Flow Equalization Reservoirs to Irrigation Sites)
Head (ft)
35
Flow (MGD) (=3 MGD applied over 8 hrs/day)
9
Efficiency (%)
70%
Hours per Year
2,920
Energy Usage (kW-Hr/Yr)
171,831
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$10,310
Treatment Costs
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$2.00
Treatment Costs ($/Yr)
$2,190,000
Total Key Annual O&M Costs
$2,263,600
Alternative 5: Discharge Additional Plant Effluent into Twelve Mile Creek
Alternative 5 proposes that the Twelve Mile Creek WWTP be expanded to 9 MGD with the total flow
being discharged at the current location or the additional 3 MGD conveyed upstream prior to discharge
into Twelve Mile Creek. For this alternative to be achieved, the County would need to demonstrate to
the NC DWQ that Twelve Mile Creek has additional assimilative capacity and that additional flow could
potentially improve overall water quality within the stream.
An initial water quality stream assessment and scoping level model were included as part of this study to
establish an engineering opinion as to whether Twelve Mile Creek can receive additional discharge
Twelve Mile Creek WWTP Expansion Alternatives - 21 -
August 2010
HAZEN AM SWER
Environmental Engineers 8 Scientists

beyond the Plant's rated capacity of 6 MGD and whether the supporting evidence is of sufficient strength
to obtain regulatory approval from SCDHEC and NC DWQ. The modeling results suggest that the
Twelve Mile Creek WWTP discharge does not cause dissolved oxygen (DO) concentrations to worsen
downstream of the outfall. To the contrary, the discharge appears to significantly increase DO
concentrations over what would be expected without the effluent flow present in the channel. This
finding, as shown in Figure 5, is a result of the increased flow velocity produced by the effluent that, in
turn, increases reaeration of the stream without substantially increasing ultimate biochemical oxygen
demand (BOD) that would offset the increased reaeration. Furthermore, the scoping model results
suggest that DO concentrations would be expected to further increase with the addition of effluent
treated to the same tertiary levels as the current effluent. This conclusion suggests that there is
assimilative capacity for increased discharge to Twelve Mile Creek, and that the effluent should be
considered a valuable resource to be utilized. Based on these findings, the County should re -initiate
talks with NC DWQ regarding keeping the plant effluent within the watershed. Options for discharging
highly reclaimed water to support restoration of Twelve Mile Creek under summer low flow conditions
appear much more likely to achieve sustainability goals than do the alternatives of pumping the water to
other discharge locations.
However, convincing both DWQ and SCDHEC will still be a challenge. Although the DO standard of 5
mg/L will not be met a significant amount of the time, the discharge is essentially a resource that
improves DO given the level of BOD and nutrient removal through the treatment plant. One location of
concern is a zone below Hwy 521 and before Van Wyck Road in South Carolina where the slope flattens
significantly. The area was not accessed during stream reconnaissance, but aerial and available LIDAR
information confirm a change of physical conditions. The model results show a significant drop in DO in
that segment (as seen in Figure 5), but without onsite investigations, it is difficult to know what is really
happening at this location. As such, both DWQ and SCDHEC will likely require intensive stream profiling
during the summer low flow periods [e.g., a walking profile with DO measurements every 500 ft between
June and September when flow conditions are low (less than 1 cfs at the Six Mile gage)]. Since the
modeling results are sensitive to oxygen decay and reaeration rates, the regulatory agencies will also
request verification of those values used in the model, for which currently only educated assumptions
have been made. Verification is best done when sufficient flow and DO is available in the stream. It is
also likely that, if an expansion is approved, additional downstream sampling may be required.
Complete results of the stream assessment and model are provided in the Appendix.
Twelve Mile Creek WWTP Expansion Alternatives - 22 -
August 2010
HA7EN AND SIVVYFdt
Environmental Engineers a Scientists

41.1
--Zero
Existing Actual (Qeff = 3.4 MGD) Discharge
Observed DO Summer 07
---Existing Permitted (Qeff = 6.0 MGD) Iri
15
Expanded Flow (Qeff = MGD)
DO (mg/L)
-I, N W A (J1 C)
iiii/. ■
Prr- A
10 epvti
n 1 7 2 A A A 7 A a 1n 11 17 14 1.4.
Distance from WWTP Discharge Location (mi)
Figure 5: Twelve Mile Creek Modeling Results
Beyond the above requirements, the regulatory approval of this alternative may also be facilitated by
comparison of alternatives on an overall environmental impact basis that evaluates carbon footprints of
each option, secondary impacts of long sewer pipelines, and total nutrient uptake across the Catawba
basin (e.g., discharge of bioavailable phosphorus and nitrogen directly to the Catawba River is more
likely to contribute to eutrophication issues than if uptake is allowed via plant roots and microbial activity
in the canopied Twelve Mile Creek stream channel).
DWQ also continues to express an interest in learning more about the proprietary dissolved oxygen
supplementation systems (e.g., BluelnGreen and ECO2 SuperOxygenation) that are currently being
marketed for low DO surface waters. These types of systems are still unproven but further evaluation
and/or piloting could help facilitate additional discussions with DWQ on options for discharging more flow
AMA
into Twelve Mile Creek.
AMIN
AVON
oasis
ANN
Table 10 and Table 11 describe estimated capital and key O&M costs, respectively, for Alternative 5.
The capital costs assume that the additional 3 MGD can be discharged at the current creek outfall
location, and thus, no force main or pump station costs are included.
Twelve Mile Creek WWTP Expansion Alternatives - 23 -
August 2010
HAZE AND SkwiER
Environmental Engineers & Scientists

Table 10: Estimated Capital Costs — Alternative 5
Description
Capital Cost Estimate
Twelve Mile Creek WWTP Expansion
Influent Pumping, Coarse Screening, and Flow Equalization
$6,500,000
Preliminary Treatment Facility
$1,500,000
Biological (Secondary) Treatment
$5,810,000
Tertiary Filtration, Disinfection, and Post Aeration
$2,088,000
Sludge Thickening, Digesters, and Sludge Storage
$5,000,000
Odor Control
$2,000,000
Standby Power
$1,000,000
Category Subtotal
$23,898,000
Effluent Pump Station and Piping
Effluent Pump Station at the Twelve Mile Creek WWTP (0 MGD @ $1/Gal)
$0
18-in DIP Force Main (0 LF)
$0
(Assume gravity outfall at current discharge location.)
Category Subtotal
$0
Subtotal 1
$23,898,000
Contingencies (25% of Subtotal 1)
$5,974,500
Subtotal 2
$29, 872, 500
Contractor OH / Profit (10% of Subtotal 2)
$2,987,250
Mobilize / Demobilize (1.5% of Subtotal 2)
$448,088
Insurance / Bonds (1.5% of Subtotal 2)
$448,088
TOTAL
$33,755,900
Twelve Mile Creek WWTP Expansion Alternatives - 24 -
August 2010
HAZE AND SW/ER
Environmental Engineers & Scientists

Table 11: Estimated Key O&M Costs — Alternative 5
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to Discharge Site)
Head (ft) (Assume gravity discharge at current creek outfall location.)
0
Flow (MGD)
0
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
0
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$0
Treatment Costs at Twelve Mile Creek WWTP
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$2.00
Treatment Costs ($/Yr)
$2,190,000
Total Key Annual O&M Costs $2,190,000
Alternative 6: Pump Additional Plant Effluent to the Catawba River
For Alternative 6, the Twelve Mile Creek WWTP would be expanded to 9 MGD and the flows above 6
MGD would be conveyed and discharged directly to the Catawba River near the Catawba River Water
Treatment Plant. Speculative limits to discharge directly to the Catawba River were issued by SCDHEC
in January 2008 for additional flows of 3, 6, and 9 MGD. A copy of this letter, which includes the mass
and concentration limits for the plant effluent, is included in the Appendix.
Also included in the wasteload allocation issued by SCDHEC is the requirement that the Twelve Mile
Creek WWTP be assigned a reliability classification of Class I since the proposed location of the
discharge into the Catawba River is within a water supply intake area as defined by SCDHEC.
Reliability Classification I requires specific redundancies and backup components for most of the
~'^ treatment processes within the plant. These requirements are described in Section 67.400 of
SCDHEC's Standards for Wastewater Facility Construction (May 2002).
The County currently splits ownership of, and receives drinking water from, the Catawba River Water
Treatment Plant (WTP). Two parallel high -service pipelines (one 24-inch diameter, one 42-inch
diameter) convey water from the WTP to Union County. The 24-inch pipeline, which is installed between
the WTP and the distribution storage tanks located on Sims Road, may be redundant and would not be
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
- 25 -
HAZEN AND SAWYER
Environmental Engineers & Scientists

needed to meet current and near -term water supply demands. As such, one option within this
alternative is to construct a new force main between the Twelve Mile Creek WWTP and the Sims Road
area, and then convert the existing 24-inch diameter force main from drinking water to wastewater
conveyance. Any taps into the existing 24-inch pipe must be confirmed and transferred to the 42-inch
pipeline. The existing air release valves would also need to be replaced with ones more appropriate for
wastewater service. Following conversion of the pipe to wastewater service, the pipe would need to be
well -marked along its entire length to prevent new water service taps from being inadvertently installed in
the future. Downstream of the existing 24-inch pipeline, near the Catawba River WTP, a new gravity or
pressure pipeline would be installed to the discharge location on the Catawba River. A route for the
proposed piping is shown in Figure 6.
Estimates for capital costs for Alternative 6 are shown in Table 12. Key O&M costs are detailed in Table
13. The pumping head value used for the O&M costs is based on estimated static and friction losses for
the piping route shown in Figure 6.
Table 12: Estimated Capital Costs — Alternative 6
Description
Capital Cost Estimate
Twelve Mile Creek WWTP Expansion
Influent Pumping, Coarse Screening, and Flow Equalization
$6,500,000
Preliminary Treatment Facility
$1,500,000
Biological (Secondary) Treatment
$5,810,000
Tertiary Filtration, Disinfection, and Post Aeration
$2,088,000
Sludge Thickening, Digesters, and Sludge Storage
$5,000,000
Odor Control
$2,000,000
Standby Power
$1,000,000
Sub -Total
$23, 898, 000
Effluent Pump Station and Piping
Effluent Pump Station at the Twelve Mile Creek WWTP (3 MGD @ $1lGal)
$3,000,000
18-in DIP Force Main (29,000 LF)
$5,220,000
Conversion of Existing Piping from Water to Wastewater
$250,000
Sub -Total
$8,470,000
Subtotal 1
$32,368,000
Contingencies (25% of Subtotal 1)
$8,092,000
Subtotal 2
$40,460,000
Contractor OH / Profit (10% of Subtotal 2)
$4,046,000
Mobilize / Demobilize (1.5% of Subtotal 2)
$606,900
Insurance / Bonds (1.5% of Subtotal 2)
$606,900
TOTAL
$45,719,800
Twelve Mile Creek WWTP Expansion Alternatives - 26 -
August 2010
17HZEN AND Sk\WER
Environmental Engineers & Scientists
flask
ANN
AMIN
r
ASK
ARK

Table 13: Estimated Key O&M Costs — Alternative 6
Description
Quantity
Pumping Costs (from Twelve Mile Creek WWTP to Discharge Site)
Head (ft)
280
Flow (MGD)
3
Efficiency (%)
70%
Hours per Year
8,760
Energy Usage (kW-Hr/Yr)
1,374,649
Energy Unit Cost ($/kW-Hr)
$0.06
Cost of Energy for Pumping ($/Yr)
$82,479
Treatment Costs at Twelve Mile Creek WWTP
Flow Rate (MGD)
3
Days per Year
365
Total Flow (Million Gallons/Yr)
1,095
Unit Cost of Treatment ($/1,000 Gallons Treated)
$2.00
Treatment Costs ($/Yr)
$2,190,000
Total Key Annual O&M Costs $2,272,500
Twelve Mile Creek WWTP Expansion Alternatives - 27 -
August 2010
HAZEN AND SAWYER
Environmental Engineers 8 Scientists

Twelve Mile Creek WWTP
Proposed Effluent
Pump Station
Proposed Force Main
Catawba River WTP
Proposed Catawba River Discharge
Sims Road
Storage Tank
Existing 24" Waterline
(Converted to Effluent
Force Main)
FIGURE 6
Alternative 6 -
Pump Additional Plant Effluent to the Catawba River
Legend
■ WWTP MIMI Existing Force Main N
Num Force Main
■ WTP - Road
Stream
• Tank
0 3,000 6.000
Envir3nmental Engineers & Scientists

els\
est1
Expansion of the Twelve Mile Creek WWTP for Alternatives 4, 5, and 6
Alternatives 4, 5, and 6 would require expansion of the Twelve Mile Creek WWTP by a minimum of 3
MGD. This section describes the major plant processes and the improvements necessary to achieve 9
MGD total maximum month flow through the plant.
Influent Pumping and Coarse Screening
The existing influent pump station has a total capacity of 20.2 MGD and a firm capacity of 14.75 MGD.
,,t\ For a plant expansion to a maximum month flow rate of 9 MGD, additional influent pumps will be
required to meet the peak hour flow rate of 22.5 MGD (2.5 times the maximum month flow rate) with one
unit out of service. A new parallel influent pump station is recommended to gain the additional 7.75
MGD (22.5—14.75) to provide total influent pumping capacity for the peak flow conditions for the 9 MGD
rat\ expansion. It is recommended that the new structure be oversized to handle a firm capacity of 22.75
,\ MGD in addition to the existing pump station's firm capacity of 14.75 MGD. This additional capacity
would allow for the future addition of influent pumps if the plant decides to expand to 15 MGD (maximum
month flow) and thus needs an influent pumping firm peak capacity of 37.5 MGD. Adequate land
appears to be available for the new pump station directly west of the existing pump station and across
from the existing access drive. In addition, if expansion of the plant is pursued in parallel with additional
transfer of flow to CMU and/or LCWSD, the new influent pump station should be consolidated with the
diversion pump stations.
Currently, the raw wastewater is screened upstream of the influent pump station by a screenings facility
that consists of one %-inch fine mechanical screen and one bypass channel with a 1/2-inch manual
screen. The plant has experienced operational problems with this screening facility and often influent
flow bypasses the screens. It is recommended that the screens be replaced with coarse bar screens in
order to ensure the removal of large debris upstream of the influent pumps. A fine screenings facility is
recommended downstream of the influent pumps. The fine screenings facility is described in more detail
eatN in the "Fine Screenings and Grit Removal Section" below.
,, gN Flow Equalization
The plant does not have existing onsite flow equalization volume. Flow equalization is recommended in
order to provide the plant with storage volume to equalize influent flow from peak hour and peak day flow
spikes. Flow can be diverted from the influent pump station force main to an above ground equalization
tank through the use of a modulating valve. A storage tank with three million gallons of storage is
recommended for the expansion to 9 MGD. For the reuse option (Alternative 4), the plant would be
required to have aerated flow equalization equal to a minimum of 25% of daily design flow.
Flow Metering
The raw wastewater is pumped from the influent pump station to the Twelve Mile Creek WWTP through
an existing 24-inch force main that travels along the eastern side of the plant. An existing 18-inch
Telk\welve Mile Creek WWTP Expansion Alternatives - 29 - HAZEN AND SYER
August 2010 S
Environmental Engineers & Scientists
%k1
elk1

magnetic flow meter is located just upstream of the existing grit facility and accurately reports flows from
1.0 MGD to 15.1 MGD. A 16-inch force main, currently out of service, travels along the western side of
the plant and connects to the 24-inch force main at a tee just upstream of the flow meter. A second tee
is located off of the 16-inch line for the provision of a future parallel flow meter. Utilization of the 16-inch
force main and installation of a parallel flow meter will be required to accurately measure peak plant
flows once the plant expands to 9 MGD.
Fine Screenings and Grit Removal
The plant currently has a grit removal facility that consists of one vortex grit collector with a rated
capacity of 15 MGD. While it is not imperative to design grit removal equipment for peak flows, it is good
practice to provide equipment redundancy. Therefore, an additional grit collector with associated grit
washing and dewatering equipment should be installed as part of a plant expansion. In addition, a fine
screenings facility upstream of the grit facility would ensure that any debris that is not removed by the
coarse screenings facility upstream of the influent pumps would be removed prior to entering the plant.
Installation of two mechanical fine screens, associated screenings compactors, and one manual screen
within a bypass channel is recommended. The installation of fine screens and an additional grit collector
will help to prolong the life of downstream equipment and reduce maintenance requirements throughout
the plant.
Biological Treatment
In 2007, Hazen and Sawyer modeled the plant's activated sludge process using BioWin software to
determine the capacity of the existing liquid treatment process and the improvements necessary for
increased flow rates. BioWin is a dynamic wastewater treatment process modeling and simulation
software package widely utilized for process design and optimization. From this previous analysis, it
was determined that modifying the oxidation ditches to provide for "once -through", plug -flow hydraulics
could increase the treatment capacity of the existing basins by at least an estimated 2 MGD (total all
basins) and possibly as much as 3 MGD depending on effluent limits and the results of recommended
stress testing of the basins and secondary clarifiers.
Plug -flow hydraulics provide for greater nitrification efficiency, thus reducing the required aerobic solids
retention time (SRT) to maintain nitrification. This reduction in SRT also promotes biological phosphorus
removal by reducing cell decay and resulting phosphorus release experienced at long sludge ages. The
result is a reduction in the overall total aerobic volume required. Thus, the existing oxidation ditches
could handle increased flow without the need for additional oxidation ditch tank volume. However, re -
rating the existing equipment for a 9 MGD expansion without providing additional aeration volume would
require operating the process at a very high solids loading rate. This high rate could put the plant at risk
of not having sufficient flexibility to maintain nitrification during extreme weather conditions. For the
purposes of this alternatives analysis, it is assumed that the existing oxidation ditches will be modified to
provide plug -flow hydraulics, and an additional 1 MGD of aeration tank volume would be required to
comfortably handle an increase in flow of 3 MGD. The cost estimate reflects this requirement as the
addition of a single 1 MGD plug flow aeration tank (although it is likely that a larger tank would actually
Twelve Mile Creek WWTP Expansion Alternatives - 30 -
August 2010
HA7,EN AND SGWER
Environmental Engineers a Scientists

eartiN
exeN
est1
be installed to accommodate future flows). Stress -testing the existing secondary clarifiers could prove
' that no additional aeration tank volume would be required to meet the permit limits by running the
rse, process at a high solids loading rate of 4,500 mg/L MLSS. Additionally, postponing modifications to the
(MN oxidation ditches and providing new larger plug flow aeration tanks may prove to be a better alternative if
✓ the plant plans to expand in the future. If the County proceeds with plant expansion, it is recommended
that further testing be performed and alternatives be considered to account for future build -out
conditions.
\ The current three -stage configuration of the oxidation ditches for the denitrification of the nitrified
wastewater would be maintained, and the anaerobic and anoxic zones within the existing oxidation
ditches would function similarly to current operations. Although the Twelve Mile Creek WWTP permit
does not require nitrate or total nitrogen removal, maintaining denitrification capabilities is advantageous
rlitN in providing alkalinity recovery. Denitrification is especially critical in meeting the low total phosphorus
limitations imposed at the Twelve Mile Creek WWTP since reduction of nitrate in the effluent reduces the
nitrate which is recycled back to the anaerobic zone via the RAS. Introduction of excessive nitrate into
the anaerobic zone leads to competition between denitrifiers and PAOs for readily biodegradable carbon
(rbCOD) and reduces biological phosphorus removal efficiency.
rst, Modifications to the existing oxidation ditches to provide plug -flow hydraulics and higher treatment
capacity would include the following:
(its
• Baffle walls would be installed in the oxidation ditch to eliminate recirculation and provide a
"once -through" plug -flow system.
• The existing aeration system in the oxidation ditches would be replaced with fine bubble diffused
aeration to provide better oxygen transfer.
to, • The velocity flow gate in each basin (which regulates the amount of nitrate return to the anoxic
ex,
zone) would be shut and nitrified recycle (NRCY) pumps and piping would be added to return
nitrate to the anoxic zone.
• The anoxic zones would be fitted with fine bubble diffusers to allow the zones to alternate
(swing) between anoxic and aerobic to maintain sufficient nitrification during cold weather.
r • Mixers would be installed in the swing zones to maintain appropriate solids mixing when the
zone air diffusers are off.
• Air would be provided by new high speed single -stage blowers.
`st., The BioWin process modeling indicated that modifying the existing oxidation ditches could be successful
in meeting the effluent criteria anticipated based on the plant's current NPDES permit limits and the
speculative limits issued by SCDHEC for discharge into the Catawba River.
Two new 85-foot diameter secondary clarifiers and associated return activated sludge (RAS) pumping
facilities would be recommended to handle the increased flow rate and potentially higher solids loading
rate (4,500 mg/L MLSS) resulting from the rerating of the existing oxidation ditches. The MLSS splitter
rsIzs
Twelve Mile Creek WWTP Expansion Alternatives - 31 - SAWYERAugust 2010
Environmental Engineers & Scientists

box, which splits flow to the secondary clarifiers, was originally designed for future plant expansion and
would likely not require major modifications.
Tertiary Filtration
The existing tertiary filter facility consists of four traveling hood filters with a total surface area of 1,728
square feet. Two additional traveling hood filters would be required to provide adequate capacity for the
plant expansion to 9 MGD. However, it should be noted that the existing traveling hood filters have
proven to be problematic and unreliable at the plant. Deep bed filters sized to handle the entire plant
flow should be considered as an alternative to installing new traveling hood filters for the plant. Deep
bed filters are generally more reliable and require less maintenance than traveling hood filters, they allow
design for higher filtration rates, and they can also be converted to denitrification filters in the future if
plant limits become more stringent. Given the increased cost requirement for replacing the entire tertiary
filter facility with deep bed filters, this option was not included in the cost estimate for this study.
However, it is recommended that a new deep bed filter facility be considered as a replacement
alternative if the plant is to be expanded.
Disinfection
The existing ultraviolet (UV) disinfection facility includes two channels, each with two banks of UV lamps.
Based on the reported design criteria of this system, an additional channel with two additional UV banks
would be required for a plant expansion to 9 MGD. Additional disinfection would be required to meet
reclaimed water fecal coliform standards if a plant reuse system is developed (Alternative 4). Installation
of a hypochlorite feed system is recommended to meet reclaimed fecal coliform standards and to
provide a disinfectant residual to prevent biological growth in the reuse water distribution system.
Post Aeration
Post aeration is presently achieved by a cascade aerator located downstream of the UV facility. A plant
expansion will require the construction of a new cascade aerator to handle the increased flow rate.
Sludge Thickening
In 2010, the plant was upgraded and a new gravity belt thickener (GBT) was installed for sludge
thickening. The GBT is sized for the plant's current rated capacity of 6 MGD. A new GBT would be
required if the plant expands to 9 MGD. A new GBT facility is recommended to house the existing GBT
and one additional 2.0-meter GBT. While two 2.0-meter GBTs are adequate to process the sludge for
the 9 MGD plant expansion, it is suggested that the GBT building be sized to house two 3.0-meter GBTs
(or a third 2.0-meter GBT) for future plant flows. Polymer feed facilities would be located within the new
GBT facility.
Digester and Sludge Storage
The existing plant has four aerobic digesters. Two digesters are 50-feet in diameter and provide
approximately 0.25 million gallons of sludge storage volume each. Two digesters are 96-feet in diameter
and provide approximately 1.1 million gallons of sludge storage volume each. Thus, the total sludge
Twelve Mile Creek WWTP Expansion Altematives - 32 -
August 2010
AA7M AND SwwFdi
Environmental Engineers & Scientists

elk)
storage capacity at the existing plant is approximately 2.7 million gallons. The existing digesters do not
provide sufficient capacity to meet proposed flows at the plant. With a plant expansion to 9 MGD, it is
estimated that an additional 3 million gallons of digester volume will be required. The new digesters
would be fitted with dome covers and would require additional blower capacity and coarse bubble
diffusers for mixing.
Odor Control
Expansion of the plant's odor control facility will be required to provide adequate odor control for a new
flow equalization structure, additional digesters, and a new GBT facility. The recently constructed odor
control system is designed for future expansion and includes adequate space and piping tie-in locations
for new scrubbing towers, chemical feed tanks and pumps, and foul air ductwork.
Standby Power
Standby generators will be required for the plant expansion to protect against power outage of the new
equipment. It is anticipated that one 1,000 kW standby generator will be required for the new plant
equipment and an additional 1,000 kW standby generator will be required for the influent pump station
and coarse screenings facility expansion and improvements.
Ancillary Plant Processes
Additional plant improvements that should be considered with a plant expansion include the following:
• Site improvements to maintain proper access to existing and new equipment.
• Process yard piping upgrades as necessary for expanded flows.
• Plant process water improvements based on new equipment requirements.
,st) The capital costs for the plant improvements described in this section for expansion to 9 MGD are
detailed in Table 15. These costs are also included in each of the alternatives requiring an expansion of
the Twelve Mile Creek WWTP.
tjt
Twelve Mile Creek WWTP Expansion Alternatives - 33 - AD ►WYE R
August 2010 �� 1
Environmental Engineers & Scientists
/ali1
/SG1

Table 15: Estimated Capital Costs for Expansion of the Twelve Mile Creek WWTP to 9 MGD
Description
Capital Cost Estimate
Twelve Mile Creek WWTP Expansion
Influent Pump Station and Coarse Screens
$3,500,000
Flow Equalization Tanks (3 MG @ $1/Gal)
$3,000,000
Preliminary Treatment Facility (Screen and Grit Facility Improvements)
$1,500,000
Oxidation Ditch Retrofit — Fine Bubble Diffusers
$750,000
High -Speed Centrifugal Blowers (4 — 5,500 SCFM Blowers)
$1,000,000
Blower Building
$360,000
Blower Air Piping
$300,000
Nitrified Recycle Pumps/Piping (4 — 4.5 MGD Pumps)
$400,000
Additional Aeration Volume (New Plug Flow Aeration Basin)
$1,000,000
Secondary Clarifiers and RAS Pump Station
$2,000,000
Traveling Bridge Filters (2 Additional)
$1,038,000
UV Disinfection — Additional Channel and Equipment
$750,000
Cascade Aerator
$300,000
New Digesters and Blowers
$3,500,000
Gravity Belt Thickener Facility
$1,500,000
Odor Control Facility Improvements
$2,000,000
Standby Power
$1,000,000
Subtotal 1
$23,898,000
Contingencies (20% of Subtotal 1)
$4,779,600
Subtotal 2
$28,677,600
Contractor OH / Profit (10% of Subtotal 2)
$2,867,760
Mobilize / Demobilize (1.5% of Subtotal 2)
$430,164
Insurance / Bonds (1.5% of Subtotal 2)
$430,164
TOTAL
$32,405,700
Twelve Mile Creek WWTP Expansion Alternatives - 34 -
August 2010
HAZENAND SOUR
Environmental Engineers & Scientists
014
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Cost Estimate Summary
Capital and key O&M costs for each alternative were presented with the descriptions above. A summary
of the major capital and O&M cost centers is provided in Table 15. Table 16 compares the total cost
estimates for each alternative and includes a 20-year equivalent annual cost (EAC) that takes into
account both capital and key O&M expenditures. The 20-year EAC assumes an interest rate of 4% and
that the O&M costs increase by 2% each year. The capital, O&M, and EAC costs are shown graphically
in Figure 7.
Table 16: Summary of Estimated Costs
Alternative
Description
1 Buy Additional Capacity at CMU's
McAlpine Creek WWMF
2 Build and Buy Capacity at LCWSD's
Indian Land WWTP
3 Partner with LCWSD to Build a New
WWTP
4 Develop a Non -Conjunctive Reuse
O&M
Capital Costs Costs
$35,086,500 $912,800
$43,116,600 $2,243,000
$50,646,600 $2,248,900
20-Year Equal
Annual Cost
(Capital + O&M)
$3,662,530
$5,828,420
$6,389,480
System (Land Purchase Not $87,685,200 $2,263,600
Included)
5 Discharge Additional Plant Effluent
into Twelve Mile Creek
6 Pump Additional Plant Effluent to the $45,719,800 $2,272,500
Catawba River
$9,132, 250
$33,755,900 $2,190,000
$5,076,890
$6,054,900
Twelve Mile Creek WWTP Expansion Alternatives - 35 -
August 2010
HAZEN ANDS ER
Environmental Engineers 6 Scientists

Capital Costs/ 20-Yr EAC
$100,000,000
$90,000,000
$80,000,000
$70,000,000
$60,000,000
$50,000,000
$40,000,000
$30,000,000
$20,000,000
$10,000,000
■
Alt 1. Buy Additional Alt 2- Build and Buy Alt 3- Partner with Alt 4- Develop a Alt 5-Discharge Alt 6-Pump
Capacity at CMU's Capacityat LCWSD's LCWSD to Build a Non•conjunctive Additional Plant Additional Plant
McAlpine Creek Indian Land WWTP New WWTP Reuse System (Land Effluent into Twelve Effluent to the
WWMF Purchase Not Mile Creek Catawba River
Included)
IN Capital Costs • 20-Yr EAC • Key O&M Costs
$5,000,000
$4,500,000
$4,000,000
$3,so0,000
$3,000,000
$2,500,000
$2,000,000
$1,500,000
$1,000,000
$500,000
so
Figure 7: Comparison of Estimated Costs
Regulatory and Constructability Impacts
Non -cost factors, such as regulatory ease, schedule, and constructability, were considered for each
alternative. These factors and key issues for each alternative are summarized in Table 17.
Twelve Mile Creek WWTP Expansion Alternatives - 36 -
August 2010
HAZE1\ AND t&WYER
Environmental Engineers & Scientists

) ) ))))) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) f ) )
Table 15: Summary of Major Cost Centers
Alternative 1 — McAlpine Creek WWMF
Alternative 2 — Indian Land WWTP
Alternative 3 — New LCWSD WWTP
Major Capital
• Potential expansion of the McAlpine
• Raw sewage pump station at the Twelve
• Raw sewage pump station at the Twelve
Cost Centers
Creek WWMF (County Fraction)
Mile Creek WWTP
Mile Creek WWTP
• Replacement of pumps in the proposed
• Force main from the Twelve Mile Creek
• Construction of a new wastewater
Diversion Pump Station and construction
WWTP to the Indian Land WWTP
treatment plant (County fraction)
of an intermediate pump station, or
• Expansion of the Indian Land WWTP
• Force main from the Twelve Mile Creek
construction of a new parallel pump
station (and force main)
(County fraction)
WWTP to the new WWTP
• Potential parallel interceptor, force main,
and gravity sewer to the McAlpine Creek
WWMF
Major O&M
• Pumping energy at Diversion Pump
• Pumping energy of new raw sewage
• Pumping energy of new raw sewage
Cost Centers
Station
pump station
pump station
• Pumping energy at the Six Mile Creek
• Unit cost for treatment at Indian Land
• Unit cost for treatment at new WWTP
Pump Station
WWTP
• Unit cost for treatment at McAlpine Creek
WWMF
Twelve Mile Creek WWTP Expansion Alternatives - 37 -
August 2010
HAM AND S&WYER
Environmental Engineers & Scientists

Table 15: Summary of Major Cost Centers (continued)
Alternative 4 — Reuse
Alternative 5 — Twelve Mile Creek Discharge
Alternative 6— Catawba River Discharge
Major Capital
• Expansion of the Twelve Mile Creek
• Expansion of the Twelve Mile Creek
• Expansion of the Twelve Mile Creek
Cost Centers
WWTP
WWTP
WWTP
• Reuse infrastructure including effluent
• Potential effluent pump station if discharge
• Effluent pump station at the Twelve Mile
pumping station(s), 5-day storage
located upstream of existing
Creek WWTP
reservoir, effluent flow equalization
• Potential force main piping if discharge
• Force main from the treatment plant to
reservoir, and secondary disinfection
facilities
located upstream of existing
the discharge location on the Catawba
River
• Land purchases and/or long-term leases
Major O&M
• Unit cost of treatment at Twelve Mile
• Unit cost of treatment at Twelve Mile Creek
• Unit cost of treatment at Twelve Mile
Cost Centers
Creek WWTP
WWTP
Creek WWTP
• Pumping energy from the treatment plant
to the effluent equalization reservoir
• Potential pumping energy if discharge
located upstream of existing
• Pumping energy of effluent pump station
• Pumping energy from the effluent
equalization reservoir to the land
application sites
• Maintenance costs for any County -owned
land
Twelve Mile Creek WWTP Expansion Alternatives - 38 -
August 2010
HAZEN AND S&WER
Environmental Engineers & Scientists
13))))4313))))))333333)) ) ) ) ) ) ) ) ) ) ) ) ) ) 3) 1 3))

) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) 1 ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) )
Table 17: Summary of Non -Cost Factors
Impacts
Alternative 1 — McAlpine Creek WWMF
Alternative 2 — Indian Land WWTP
Alternative 3 — New LCWSD WWTP
Constructability / Feasibility
The County has the infrastructure for
The Indian Land WWTP is currently
Since the wastewater flow in Lancaster
this alternative in place (or pending)
only rated for 2 MGD; thus, treating 3
County south of Highway 5 is
and a contract to transfer flow to the
MGD from the County would require a
transferred to the City of Lancaster's
McAlpine Creek WWMF. However,
based on recent flows at the McAlpine
significant expansion project. Further, a
contract would need to be negotiated
treatment facilities and Lancaster
County operates the Indian Land
Creek WWMF, CMU may not have
additional capacity to sell to the County.
with LCWSD for acceptance of flow.
WWTP to handle flows in the northern
part of Lancaster County, there is likely
little need for LCWSD to invest in a new
treatment plant.
Regulatory / Permitting
If additional capacity is available at the
The Indian Land WWTP has an existing
Permitting for a new wastewater
McAlpine Creek WWMF, permitting
NPDES permit for expansion up to 15
treatment plant, especially one that
should only be required by DWQ for the
MGD, including wasteload allocations
may involve regulatory agencies in both
expansion of the Diversion Pump
Station and associated piping.
at 1.5, 2, 4, 7.5, and 15 MGD.
However, the approved 208 Plan will
need to be amended/modified to
include flows from North Carolina. A
30-day notification period for public
comment will also be required.
Permitting will also include that
associated with the force main in both
North Carolina and South Carolina.
North Carolina and South Carolina,
would be extensive. SCDHEC has
recently indicated that the 208 Water
Quality Management Plan approval
would be very difficult, especially since
the Indian Land WWTP nearby has
already been permitted to serve as a
regional facility. Both the 208 Plan
approval and the NPDES approval will
require for each a public comment
period and an appeal period.
Schedule
If the McAlpine Creek WWMF requires
The schedule for this alternative would
The schedule would be dictated by the
expansion and/or capacity will not be
be dictated by the expansion of the
permitting process (potentially 2-4
available until the proposed Long Creek
treatment plant and the negotiation of a
years), the construction of a new
WWTP is online, additional County flow
contract between the County and
treatment plant, and the negotiation of
may not be granted until 2014 or
thereafter.
LCWSD.
a contract between the County and
LCWSD.
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
-39-
HAM AND SOWER
Environmental Engineers 8 Scientists

Table 17: Summary of Non -cost Factors (continued)
Impacts
Alternative 4 — Reuse
Alternative 5 — Twelve Mile Creek
Alternative 6— Catawba River
Discharge
Discharge
Constructability / Feasibility
The largest impediment to the reuse
This alternative is, by far, the simplest
A force main between the Twelve Mile
alternative is finding enough irrigable
land that can continuously accept up to
in terms of construction and operation,
and would require capital and O&M
Creek WWTP and the potential
discharge location south of the
3 MGD under a non -conjunctive reuse
costs well below the other alternatives if
Catawba River WTP would be lengthy
permit. Much of the land surrounding
the discharge location remains at the
and expensive. The alternative to use
the plant is zoned for residential
existing location. If the effluent is
the existing 24-inch water line would
development that is capable of minimal
discharged upstream of the plant, costs
reduce construction costs but require
reclaimed water use. Thus, long
of a pump station and force main must
that all existing connections are
pumping distances may be required. In
addition, large storage reservoirs would
be required to equalize diurnal and wet-
weather irrigation limitations.
be considered. The feasibility of this
alternative is limited by regulatory
acceptance of further discharges into
Twelve Mile Creek.
verified.
Regulatory / Permitting
Although DWQ would favor the
NCDWQ has previously stated that
Permitting for this alternative would be
beneficial reuse of reclaimed
additional discharge to Twelve Mile
coordinated with regulatory agencies in
wastewater, a non -conjunctive permit
Creek will not be approved based on
both North Carolina and South
for land application of 3 MGD will
low DO concentrations and low
Carolina. SCDHEC has previously
require significant redundancy in
seasonal stream flows. Thus, even if
issued speculative limits for this
treatment, storage, and irrigable
the supporting evidence that the creek
discharge. However, since a new
property. One alternative is a seasonal
has additional assimilative capacity is
NPDES permit for discharge into the
discharge permit to land apply final
strong, obtaining regulatory approval
Catawba River would need to be
effluent during the summer and to
from NC DWQ will be challenging.
obtained, SCDHEC will require the full
discharge to Twelve Mile Creek during
Expensive modeling and long-term
208 Plan regulatory review and NPDES
the winter.
sampling may be required.
review (both with public comment and
appeal periods).
Schedule
The critical path for a reuse system of
Obtaining regulatory approval from NC
Approval by SCDHEC represents the
this size will be the identification and
purchase of the required land area.
DWQ could be a long process,
especially if long-term sampling and/or
modeling is required.
critical path for this alternative.
Permitting alone could be 2-4 years.
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
-40-
I]AZEN AND SAWYER
Environmental Engineers & Scientists
I))) ) ) 33))) 1 ! /)))) /))))) / I)))) )))) )))))) )

AIM
AMOK
AMIN
Recommendations
Following evaluation of the capital costs, key O&M costs, and critical non -cost factors, a decision matrix
was developed to help compare the six alternatives under consideration. This matrix is shown in Table
18. In the decision matrix, the capital and key O&M costs were normalized to the alternative with the
highest cost and then scaled to a value between 1 and 5, with 1 being more favorable and 5 being less
favorable. The non -cost factors of Regulatory/Permitting and Schedule were assigned ratings between 1
and 5 for each alternative, again with 1 being more favorable and 5 being less favorable. The four
decision categories were then assigned a weighting factor based on importance to the County and a
weighted average for each alternative was calculated. The alternatives were then ranked based on their
weighted averages.
Table 18: Decision Matrix
Decision Factor
Capital Costs
(Quantitative)
1
CMU
McAlpine
2.00
2
LCWSD
Indian Land
2.46
Alternative
3
LCWSD
New Plant
2.89
4
Reuse
5.00
5
Twelve Mile
Creek
1.92
6
Catawba
River
2.61
Weight
0.25
O&M Costs
(Quantitative)
0.40
0.99
0.99
1.00
0.96
1.00
0.25
Regulatory /
Permitting
(Qualitative)
1
2
5
3
4
4
0.25
Timeline
(Qualitative)
4
1
5
5
4
4
0.25
Weighted Average
1.85
1.61
3.47
3.50
2.72
2.90
Rank
2
1
5
6
3
4
1 = Most Favorable, 5 = Least Favorable
4111,,
The objective of the Expansion Alternatives Development Study was to provide the County with the
required information to shortlist the alternative(s) that could be further refined and developed to cost-
effectively provide approximately 3 MGD of additional capacity at the Twelve Mile Creek WWTP. Based
on the ranks assigned in the decision matrix, it appears that the three most feasible, cost-effective
options are,
1. Alternative 2: Build and Buy Capacity at LCWSD's Indian Land WWTP
2. Alternative 1: Buy Additional Capacity at CMU's McAlpine Creek WWMF
3. Alternative 5: Discharge Additional Plant Effluent into Twelve Mile Creek
The next steps in moving forward with these options would be more formal discussions with LCWSD
(Alternative 2), discussions with CMU (Alternative 1), and NC DWQ (Alternative 5). In addition, DWQ
and SCDHEC should be consulted to determine in more detail the necessary permitting steps prior to
RIR
proceeding with any alternative. As summarized in the next section, preliminary meetings with NC DWQ
and SCDHEC were conducted to solicit feedback on the alternatives discussed in this memorandum.
Twelve Mile Creek WWTP Expansion Alternatives - 41 -
August 2010
HAZEN AM SASWER
Environmental Engineers & Scientists

Regulatory Coordination
On June 8, 2010, the County and Hazen and Sawyer met with representatives from NC DWQ to discuss
the status of the project and project developments since formal comments were received in 2006/2007.
The six alternatives for wastewater diversion and discharge were summarized and feedback from NC
DWQ was offered. All of the alternatives still appear to be feasible in terms of NC DWQ permit approval.
The County and Hazen and Sawyer also met with SCDHEC on June 1, 2010 to solicit feedback on the
alternatives that directly or indirectly impact South Carolina. A summary of the comments, sorted by
alternative, are shown in Table 19. Table 19 also lists the key participants of each meeting.
As mentioned in Table 19, NC DWQ requested that the County resubmit its request for speculative limits
such that DWQ can formally respond to the feasibility of this alternative. Hazen and Sawyer also agreed
to forward complete stream modeling results and data files such that DWQ's Modeling and TMDL Unit
could review. [Note that the requested letter was issued by Hazen and Sawyer on June 16, 2010
(reference copy of letter in the Appendix) and modeling files were sent directly by Hazen and Sawyer's
sub -consultant Tetra Tech to DWQ.] SCDHEC stated that the permitting requests for any of the
alternatives would require quantifying the impact of capital and operating costs on user rates. This
economic evaluation will likely be required for NC DWQ as well. In addition, SCDHEC mentioned that,
although not directly involved in the alternatives under consideration, its current work in evaluating
tighter phosphorus permit limits for Fishing Creek Reservoir, could lead to similar requirements for any
new permits for this project.
Table 19: Summary of Regulatory Meeting Comments
Key Regulatory
Participants at
Meeting
NC DWQ
• Mr. Tom Belnick — Supervisor,
NPDES Complex Permitting Unit
• Ms. Kathy Stecker— Supervisor,
Modeling and TMDL Unit
• Mr. Jeff Poupart — Supervisor, Point
Source Branch, Surface Water
• Mr. Michael Parker — Surface Water
Protection (Mooresville)
SCDHEC
• Mr. Jeff deBessonet, Director, Water
Facilities Permitting
• Mr. Mike Montebello, Manager,
Domestic Wastewater Permitting
Section
• Mr. Jaeho Ho, Engineer, Domestic
Wastewater Permitting Section
• Ms. Anne Rone McGovern,
208 Program Coordinator, Catawba
Watershed Manager
Alternative 1: Buy
Additional Capacity at
CMU's McAlpine
Creek WWMF
• No direct comments. NC DWQ is
familiar with the County's current
contract with CMU, with CMU's
capacity limitations, and with the
current decisions facing CMU (i.e.,
whether to expand the McAlpine
Creek WWMF and/or build the
proposed Long Creek WWTP).
• Based on McAlpine's discharge
location, SCDHEC has a general
understanding of CMU's current
status of treatment capacity.
• DHEC mentioned that LCWSD may
have also inquired about the
potential to send flow to the
McAlpine Creek WWMF.
Twelve Mile Creek WWTP Expansion Alternatives - 42 -
August 2010
II4ZE \ AND SWER
Environmental Engineers & Scientists

Table 19: Summary of Regulatory Meeting Comments (continued)
Alternative 2: Build
and Buy Capacity at
LCWSD's Indian
Land WWTP
NC DWQ
• NC DWQ would have little direct
input in this alternative beyond
permitting of the force main to carry
flow to the Indian Land WWTP.
SCDHEC
• At this meeting, Hazen and Sawyer
received (through its earlier FOI
request) the PER for the Indian
Land Wastewater Treatment Plant
Expansion (August 2005)
• Based on comments made by
SCDHEC during this meeting, the
basis for the permitting of 15 MGD
for the Indian Land WWTP was that,
at the time of permitting of the plant,
future flow projections included the
intentions to build very large
developments in the area (e.g., the
Waxhaw Creek development). With
the economic downturn, these
developments never came to
fruition.
• For this alternative, since the plant
would be receiving flows from NC,
and NC is not mentioned within the
current 208 Plan, permitting would
include a major 208 Amendment
and require a public comment
period.
Alternative 3: Partner
with LCWSD to Build
a New WWTP
• NC DWQ would have little input in
this alternative beyond permitting of
the force main to carry flow to the
new WWTP.
• SCDHEC was aware of the earlier
discussions by LCWSD that a new
plant could have been needed in
the future if the large planned
developments in the northern part of
Lancaster County had been built.
This alternative seems unlikely
given the impact of the current
economic environment on
wastewater flow projections.
Alternative 4:
Develop a Non -
conjunctive Reuse
System
• NC DWQ would request a thorough
review of the reuse options but
understands the large capital
investment and limited user
availability.
• Hazen and Sawyer described the
negative public response from
several years ago when the County
considered land use for effluent
disposal.
• NC DWQ is willing to consider a
seasonal discharge permit as part of
a reuse alternative.
• SCDHEC will require that reuse and
land application be considered as
an option prior to granting approval
of any discharge permits.
Twelve Mile Creek WWTP Expansion Alternatives - 43 -
August 2010
HAZEN AND S&WER
Environmental Engineers & Scientists

Table 19: Summary of Regulatory Meeting Comments (continued)
Alternative 5:
Discharge Additional
Plant Effluent into
Twelve Mile Creek
NC DWQ
• Following a summary of the results of
the QUAL2E stream water quality
model, NC DWQ confirmed that an
expanded discharge into Twelve Mile
Creek may still be a potential
alternative.
• Based on the potential for low flows
in the stream, NC DWQ questioned
whether there are alternatives in the
upstream watershed that would lead
to an increase in base flows. As part
of the conversation on watershed
protection and non -point -source
discharges, Stormwater Discharges
from Municipal Separate Storm
Sewer Systems (MS4) was
discussed.
• It was noted that the stream is listed
as impaired for copper and turbidity
and that any future permitting would
require consideration of these
standards.
• NC DWQ discussed the potential for
tighter ammonia limits as it considers
loading throughout the basin.
• NC DWQ asked that a new letter be
issued formally requesting
speculative limits for an expanded
discharge.
SCDHEC
• Beyond ensuring that the overall
phosphorus mass loadings are not
exceeded from Twelve Mile Creek,
SCDHEC would not have a direct
role in the permitting of this option.
Alternative 6: Pump
Additional Plant
Effluent to the
Catawba River
• NC DWQ would have little direct
input in this alternative beyond
permitting of the force main to carry
flow to the Catawba River.
• The environmental and sustainability
impacts of this option versus the
benefits of expanding the discharge
into Twelve Mile Creek at the
treatment plant were discussed.
• The permitting of this alternative
should not be impacted by the
availability of permitted capacity at
the Indian Land WWTP.
• For this alternative, permitting would
require a 208 Amendment (and
public comment period) and a new
NPDES permit approval (and public
comment period).
Twelve Mile Creek WWTP Expansion Alternatives - 44 -
August 2010
HAZEN AND SAWYER
Environmental Engineers & Scientists

/221
,� SCDHEC Speculative Wasteload Allocation
Discharge to the Catawba River
Twelve Mile Creek WWTP, Union County, NC
January 29, 2008
ent Twelve Mile Creek WWTP Expansion Alternatives ANDHAZEN SYERAugust 2010
Environmental Engineers & Scientists
�1

01114,
ARK
,ate
ink
ink
BCA?tD:
Paul C. Aughtry, III
Chairman
Edwin H. Cooper, III
Vice Chairman
-even G. Kisner
PROMOTE PROI'EC1' PROSPER
'crerary C. Earl Hunter, Commissioner
Promoting and protecting the health of the public and the environment
January 29, 2008
Mr. James N. Struve, P.E.
Hazen and Sawyer, P.C.
4944 Parkway Plaza Blvd. Suite 375
Charlotte, NC 28217
RE: Twelve Mile Creek WWTP, Union County, NC - Wasteload Allocation
NPDES Permit No. SC00Proposed
Lancaster County
Dear Mr. Struve:
BOARD:
Henry C. Scott
M. David Mitchell, MD
Glenn A. McCall
Coleman I.. Buckhouse, MD
The Water Quality Modeling Section has reviewed your request asking for a wasteload allocation for
the proposed discharge to Twelve Mile Creek and Catawba River, and determined that a wasteload
allocation for the proposed discharge to Twelve Mile Crgp.K__c.Qnot..t su_r„ed due to t e water
—quality—in the receiving water. As a backup plan, a wasteload allocation has been o6tamed'for
TwefV ' Mile Creek' WWTP at the proposed flow of 3, 6, and 9 MGD to Catawba River. This
wasteload information will replace or supersede all previous wasteload information provided based
on new information presented by the Water Quality Modeling Section.
Based on the wasteload allocation, the NPDES limits can be expected to be as follows (these are
generally monthly average values unless noted, additional limits with weekly average and daily
maximum concentrations may also be included):
Parameter
Mass Limits (Ibs/day)
Concentration Limits (mg/L)
Monthly Average
Weekly
Average
Daily Maximum
Monthly
Average
Weekly
Average
Daily
Maximum
Flow (MGD)
3/6/9
3/6/9
SODS (Mar -Oct)
125/250/375
188/375/563
---
5
7.5
---
BOD5 (Nov -Feb)
250/500/750
375/751/1126
--
10
15
---
TSS
750/1501 /2252
1126/2252/3378
—
30
45
---
NH3-N (Mar -Oct)
25/50/75
38/75/113
---
1
1.5
---
NH3-N (Nov -Feb)
50/100/150
75/150/225
---
2
3
---
TRC
0.28/0.55/0.83
--
0.48/0.95/1.43
0.011
---
0.019
Dissolved Oxygen
--
---
__
--
_-
6.0(minimum
at all times)
Fecal Coliform
---
---
---
200/100mL
---
4001100mL
Total Cadmium
0.0085/0.017/0.026
--
0.048/0.095/0.14
0.00034
--
0.0019
Total Copper
0.24/0.49/0.73
--
0.33/0.65/0.98
0.0097
--
0.013
Total Lead
0.08/0.16/0.24
—
2.08/4.15/6.23
0.0032
--
0.083
Total Zinc
MR
—
4.0/8.0/12.0
MR
---
0.16
Total Phosphorus
Monthly Average: 41 7
12 Month Average: 20.85
—
- -
---
Total Nitrogen
MR MR j —
MR
MR
---
WET Chronic
©100%
SOUTH CAROLINA DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROL
2600 Bull Street • Columbia, SC 29201 • Phone: [phone] • www.scdhec.gov

elk\
(111
f"
The following conditions should be noted. The wasteload is informational only until the following
actions occur:
r4
1. A determination whether the project is consistent with the applicable 208 Water Quality Plan
must be made on the proposed discharge during the NPDES permit process. e"''
2. In situations where a permittee proposes a new or expanded discharge into surface waters
whose quality is greater than water quality standards (i.e., higher quality waters), an r"•
�
alternatives analysis shall be included in the engineering report. The report should also ro',
show that the proposal is necessary to important social and economic development in the
area of the receiving waters such that the discharge should be allowed under the anti -
degradation r'R`
provisions of Regulation 61-68 (Water Quality Standards). The alternatives r,",
analysis shall demonstrate that none of the following applicable alternatives are
economically and technologically reasonable: r�
(a) Reuse that would minimize or eliminate the need to lower water quality;
(b) Use of other discharge locations; e,
(c) Connection to other wastewater treatment facilities;
(d) Use of land application;
(e) Product or raw material substitution; and r"'N
(f) Any other treatment option or alternative, which would minimize or eliminate the need
to lower water quality.
r"N
2. An NPDES permit application and preliminary engineering report is provided on the
proposed discharge. Please note that the NPDES permitting action must be completed in ("`
accordance with Regulation 61-9, and no appeals filed, before a Construction Permit could (41°,
be considered for this project.
3. The selected wasteload allocation is subject to EPA Region IV certification since this is a
raliN
major facility.
r"'N
4. Additional metals testing and/or requirements may be necessary subject to information
provided with the NPDES application and/or PER. Submission of available effluent metals ("'
data may result in specific pollutants to be added or deleted from the limits. l.,
5. Please note that the applicant must comply with the provisions of R61-9.600 (Viability r'1°'
Requirements) that address entities owing wastewater systems have the technical, (41",
managerial and financial means to comply with the regulations as a prerequisite for receiving
a wastewater discharge permit (NPDES). As part of the NPDES process, please provide a 'a'
business plan (e.g. audit) or other documents identifying the viability of the facilities. rEt,
6. Please note that Twelve Mile Creek WWTP will have a reliabili classification of class I, in r44‘
accordance with R.61-67. The WWTP assigned a class s a I meet a requirements listed
in Section 67.400. We would verify Class I wastewater reliability items at the time you
propose the outfall line which will require a SC construction permit (provided an NPDES err,
permit is issued and not appealed).
ea's
If you have any questions, please do not hesitate to call me at [phone].
Sincerely, f'°'
6tpckeg
Michael J. Montebello, Manager
Domestic Wastewater Permitting Section
Water Facilities Permitting Division

jh
cc: Region 3, Lancaster EQC Office
Beth Quattlebaum, SC DI-IEC (w/a)
Mark E. Tye, Perblic Works Department, Union County, NC (w/a)
Jeff deBessonet, Director, Water Facilities Permitting Division
Larry Turner, Manager, Water Quality Modeling Section
Erica A. Johnson, Water Quality Modeling Section
Attachment Wasteload Allocation Worksheet

Scoping Level Assessment of Assimilative
Capacity in Twelve Mile Creek Below
the Union County WWTP
Tetra Tech, April 2010
Twelve Mile Creek WTP Expansion AlternativesWEN AND SWYERAugust2010
W
Environmental Engineers & Scientists

Scoping Level Assessment
of Assimilative Capacity
in Twelve Mile Creek
Below the Union County WWTP
Prepared for
Union County
Public Works Department
500 N. Main St. Suite 500
Monroe, NC 28112-4730
and
Hazen & Sawyer, P.C.
4944 Parkway Plaza Blvd., Suite 375
Charlotte, NC 28217
Prepared by
TETRA TECH
3200 Chapel Hill -Nelson Hwy, Suite 105 • PO Box 14409
Research Triangle Park, NC 27709
April 2010

Tt Scoping Assessment — Twelve Mile Creek April 2010
Table of Contents
1 Introduction 1
2 Review of Existing Information 3
2.1 Description of Information Reviewed 3
2.2 Preliminary Synthesis 3 P"�
2.2.1 WWTP Discharge Characteristics 4 r(1'N
2.2.2 Water Quality in Twelve Mile Creek 4 r�
2.2.3 County — DWQ Permitting Correspondence 8 r41'N
2.2.4 Preliminary Discussion 8 rI'LN
3 Scoping Level Modeling Analysis 11
3.1 Field Reconnaissance 11
3.1.1 Purpose 11
3.1.2 General Description of Field Survey Methods 1 I
3.1.3 Field Measurements and Observations 12
3.2 Model Setup 14
3.2.1 Reach Delineation 14
3.2.2 Reach Hydraulics 15
3.2.3 Water Quality Model Input Assumptions 17
3.2.4 Methods for Estimating Model Kinetics 18
3.2.5 Baseline Model Calibration Fit 19
3.2.6 Model Application 22
4 Conclusions and Discussion 25
5 References 27
Appendix A. Channel Cross Sections A-1
Appendix B. UAL2E Model Input and Output B-1
rd`'N
r^

Tt Scoping Assessment — Twelve Mile Creek April 2010
List of Tables
Table 1. Median DO Concentrations Observed by County during the Summer 2009 6
Table 2. Location of Cross Section Measurements on Twelve Mile Creek 12
Table 3. Summary of Model Flow Input Assumptions 17
Table 4. Hydraulic Parameters for the QUAL2E Modeling Reaches 17
Table 5. Water Quality and Typical Summer Flow Rates Assumed for the Twelve Mile Creek
QUAL2E Model 18
Table 6. Summary of Model Kinetic Rate Assumptions 19
® ma
ii

Tt Scoping Assessment — Twelve Mile Creek April 2010
List of Figures
Figure 1. Location Map for Twelve Mile Creek Watershed 5
Figure 2. Field with Poultry Litter Recently Applied 7
Figure 3. Woody Debris Obstructing Tributary Flow 7
Figure 4. Cross Section at Site 01, Upstream of the WWTP Discharge 12
Figure 5. Location of Channel Cross Section Measurements on Twelve Mile Creek 13
Figure 6. Plot of Cross Section Data for Site 01, Upstream of the WWTP Discharge 14
Figure 7. Slope Approximations Based on LIDAR Data 15
Figure 8. Comparison of Simulated and Observed Low Flow Velocities with Manning's n = 0.2 16
Figure 9. Example of Obstructions in Twelve Mile Creek that Influence Velocity (near Site 2) 16
Figure 10. Comparison of Simulated and Observed Dissolved Oxygen in Twelve Mile Creek 20
Figure 11. Impacts of Varying the Deoxygenation Rate by 20 Percent 21
Figure 12. Impacts of Varying the Reaeration Rate by 20 Percent 21
Figure 13. Impacts of Varying the Sediment Oxygen Demand Rate by 20 Percent 22
Figure 14. Simulated Dissolved Oxygen Concentrations for Four Modeling Scenarios 23
iii

Tt Scoping Assessment — Twelve Mile Creek April 2010
(This page left intentionally blank.)
Eil TIFIVATOC114
iv

Tt Scoping Assessment — Twelve Mile Creek April 2010
1 Introduction
Tetra Tech is conducting a Scoping level study of assimilative capacity in Twelve Mile Creek for Union
County. The county is exploring expansion of its Twelve Mile Creek Wastewater Treatment Plant
(WWTP). Low summer flows and periodic low dissolved oxygen (DO) concentrations have led the North
Carolina Division of Water Quality (DWQ) to question the ability of the receiving water to assimilate
treated wastewater. Tetra Tech is examining factors affecting assimilative capacity more closely to
provide feedback to the county and DWQ on whether expansion of discharge to Twelve Mile Creek is
worth pursuing.
To conduct this work, Tetra Tech performed three tasks. The first task involved compiling and reviewing
existing information to establish an understanding of how assimilative capacity has been evaluated to date
in light of available water quality data. Tetra Tech then performed field reconnaissance and survey to
obtain channel cross -sectional information, longitudinal elevation data, and visual inspection of the
receiving waters downstream of the county WWTP. The third task involved setup and application of a
QUAL2E stream water quality model2 using available and survey information, to examine assimilative
capacity in Twelve Mile Creek.
This report documents the findings of all three tasks, and provides recommendations and conclusions
based on the research performed.
1

Tt Scoping Assessment — Twelve Mile Creek April 2010
(This page left intentionally blank.)
E:I
2

ik's
Tt Scoping Assessment — Twelve Mile Creek April 2010
2 Review of Existing Information
Task 1 of the Tetra Tech study involved compiling and synthesizing the existing information. The
purpose of this first step was to develop a greater understanding of the issues and how assimilative
capacity has been evaluated to date. efr`
2.1 DESCRIPTION OF INFORMATION REVIEWED
The following sources of information were reviewed by the project team:
1. The DWQ Permit File (reviewed in the Archdale Building, Raleigh) contains the NPDES permit,
fact sheet, wasteload allocation modeling notes, compliance and enforcement information, and
related correspondence. rR\
2. Basinwide Assessment Report — Catawba River Basin. North Carolina Department of
Environment and Natural Resources (NCDENR) DWQ Environmental Sciences Section. April
2008.
3. Catawba River Basin Ambient Monitoring System Report (January 1, 2003 through December
31, 2007). NCDENR DWQ.
4. Catawba River Basin Management Plan. NCDENR DWQ. September 2004. (r'`
5. North Carolina Ecosystem Enhancement Program Targeted Watersheds of the Catawba River e`
Basin. 2003.
6. Watershed Water Quality Assessment: Catawba River Basin. South Carolina Department of r1°N
Health and Environmental Control. December 2005.
7. Temperature and DO Monitoring for Twelve Mile Creek. Union County, 2001 — 2009;
information included photos and personal communication with Nelson Baker, Union County e`
WWTP Lab Coordinator, who has collected the instream data for the county since 2000. r"RN
8. USGS stream flow estimates for Twelve Mile Creek (Station #02146900) and Six Mile Creek
(Station #021469901). Letter from Curtis Weaver, USGS Hydrologist, to McKim and Creed (July
15, 2002).
9. USGS historical flow information at Twelve Mile Creek near Waxhaw (Station 02146900) e"''
recorded from 1961 through 2003; and at Station 0214685800 in Six Mile Creek near Pineville e,
recorded from 2007 through present.
10. GIS data (National Hydrography Dataset and USEPA Envirofacts Geodatabase).
2.2 PRELIMINARY SYNTHESIS
Twelve Mile Creek is part of the Catawba River subbasin 03-08-38 in North Carolina, along with Six
Mile Creek and Waxhaw Creek. Six Mile Creek joins Twelve Mile Creek approximately 3 miles after it r•�,
crosses over into South Carolina. Twelve Mile Creek is located within the Carolina Slate Belt geologic
formation which is characterized by high levels of rock substrate and low summer flows (NCDENR,
2008).
The Union County Twelve Mile Creek WWTP discharges to the creek approximately 2 miles above the (411+
North Carolina -South Carolina state lint (Figure 1). The distance from the WWTP outfall to the junction ow\
of Twelve Mile Creek with the Catawba River is roughl 15 miles. The drainage area above the WWTP
outfall is approximately 76.5 square miles (USGS Station #0214 00), with an estimated average flow of ehN
72.7 cfs, a 7Q10 flow of 0.1 cfs, and a 30Q2 flow of 3.2 cfs (USGS, 2002). The USGS has also estimated
TITRwTsw 3
ram+

roe1
/IE1
Tt Scoping Assessment — Twelve Mile Creek April 2010
the drainage area at the mouth of Six Mile Creek (Station # 021469901) as 39.6 square miles, with an
estimated average flow of 37.6 cfs, a 7Q10 of 0.05 cfs and a 30Q2 of 1.6 cfs.
est, 2.2.1 WWTP Discharge Characteristics
The existing NPDES Permit (NC0085359) for the Twelve Mile Creek WWTP permits a monthly average
discharge up to 6 MGD. Other permit limits include:
BODS: 5 mg/L monthly average
nst,
NH3N: 1 mg/L monthly average
DO: 6 mg/L daily average
Total Copper: 10.3 pg/L daily average
Total Phosphorus (TP): 41.7 lbs/day monthly average; 20.85 lbs/day 12-month average
The annual average daily flow rate for 2009 was 3.4 MGD (NCDENR Permit file). Effluent
characteristics as contained in the NPDES permit application are listed as:
pH: range of 6.3 to 8.97 SU
Temperature maximum: 25.8 degrees Celsius
BODS (955 samples): 3.2 mg/L daily average [Jun — Oct averages —0.8 mg/L]
TSS: 2.7 mg/L daily average
NH3N: < 0.01 mg/L daily average
egaN TKN: 1.3 mg/L daily average [1.6 mg/L daily maximum]
NO2+NO3: 4.0 mg/L daily average [5.9 mg/L daily maximum]
TP: 0.55 mg/L daily average [0.86 mg/L daily maximum]
est, The effluent from the Twelve Mile Creek WWTP flows down a cascade to an underground pipe that
travels approximately one -quarter mile prior to entering the receiving stream (Nelson Baker, personal
communication with Trevor Clements on March 18, 2010).
2.2.2 Water Quality in Twelve Mile Creek
The NCDENR DWQ Ambient Monitoring System Report (2008) indicates that data collected in Twelve
Mile Creek at the NC16 crossing near Waxhaw (Station # C9819500) have resulted in a designation of
exe
impairment caused by fecal coliform and turbidity standard violations. Over 24 percent of the
est, observations violated the fecal coliform standard (geometric mean of 200 col/100mL), and over
13 percent of the turbidity observations exceeded the standard(50 NTU). Other observations by DWQ
included 0.9 percent exceedance of the DO standard (minimum of 4 mg7L), 1.7 percent exceedance of the
pH standard (> 9 SU). Ninety percent of the 60 DO observations were above 5 mg/L. Ninety percent of
the 60 temperature observations were recorded below 23.4 degrees Celsius. Nelson Baker with Union
County has pointed out that the state has created a weir for sampling that aerates the water such that DO
may be registering higher concentrations than would be naturally occurring in the creek upstream of the
discharge point.
tJ1TThAT.04 4

Tt Scoping Assessment - Twelve Mile Creek April 2010
North Carolina
4,—
South Carolina
South Carolina
Two,. MN Gook WaNnMd
MECKLENBURG COUNTY
North Carolina
UNION COUNTY
Legend
® Point Source Discharge
NC_boundary
County Boundary
Six Mile Creek Subwatershed
Twelve Mile WWTP Subwatershed
Twelve Mile Watershed
0 0.5 1 2 3 4
Miles
Figure 1. Location Map for Twelve Mile Creek Watershed
5

Tt Scoping Assessment — Twelve Mile Creek April 2010
The NCDENR Basinwide Assessment Report for the Catawba River Basin (2008) indicates that fish
AN. populations were evaluated at two locations in Twelve Mile Creek during 2007, East Fork at SR 1008 and
,.� West Fork at SR1321. No benthic macroinverbrate data were collected in Twelve Mile Creek. The fish
communities were rated "Good" at both locations using the NCIBI method. Total habitat scores at the two
sites both rated moderate (66 and 67, respectively, on a scale of 100), just above the threshold of low
habitat quality (62 points).
•, As part of its NPDES permit requirements, Union County has been collecting instream data on
temperature and dissolved oxygen. County staff calibrate meters daily and adhere to standard sampling
protocols. Records from 2001— 2009 reveal a relatively high frequency of days during the summer period
where DO drops below the state standard daily average of 5 mg/L and daily minimum of 4 mg/L, both
upstream and downstream of the WWTP outfall. Generally, downstream DO is higher than upstream DO.
In 2009, monitoring was expanded to 12 upstream locations. Median concentrations for the 35
observations collected at each site by the county in the summer of 2009 between May 14 and August 27
are provided in Table 1 below.
Ank
Auk
II k
ink
.014
oft
Aft
014
Table 1. Median DO Concentrations Observed by County during the Summer 2009
Monitoring Site Description
Median DO
(mg/L)
DOWNSTREAM: 1 1/4 Mile Below Plant Discharge at SR-1301 Bridge
5.62
12-MILE PLANT: Effluent outfall
7.93
UPSTREAM 1: 1/4 Mile Above Plant Discharge at NC-16 Bridge
5.45
UPSTREAM 2 -TRIB: Cuthbertson Rd. 1/4 Mile off NC-16 at SR-1321 Bridge
6.29
UPSTREAM 3 - TRIB: Howie Mine Rd. 3/4 Mile from NC-16 at SR 1008 Bridge
3.71
UPSTREAM 4: Waxhaw - Indian Trail Rd. between New Town Rd. and NC-16 at SR-1008 Bridge
4.23
UPSTREAM 5: Shannon Dr. 1/4 mile Off of Waxhaw-Indian Trail Rd. at SR-1328 Bridge
4.46
UPSTREAM 6 - TRIB: Shannon Dr. 3/4 mile Off of Waxhaw Indian Trail Rd. at SR-1328 Bridge
4.04
UPSTREAM 7 - TRIB: Billy Howie Rd. between Pleasant Grove Rd. & New Town Rd. at SR-1329 Bridge
5.51
UPSTREAM 8 - TRIB: Chamberwood Rd. 2/10 of a Mile off New Town Rd. at SR-1336 Bridge
5.60
UPSTREAM 9 - TRIB: S. Potters Rd. 1/4 Mile from New Town Rd. at SR-1162 Bridge
4.02
UPSTREAM 10: S. Potters Rd. between New Town Rd. and NC-84 at SR-1162 Bridge
3.39
UPSTREAM 11: Bridge on NC-84 1/2 Mile from S. Potters Rd.
3.84
UPSTREAM 12 - TRIB: Bridge on NC-84 1 1/2 Miles from S. Potters Rd.
3.25
Although data were not collected at the exact same time at each site, in general all sites were sampled
within a 2-hour window providing for relative comparability. The headwater samples (Upstream 10 -12)
— have the lowest median concentrations, ranging from 3.25 to 3.84 mg/L. Where Twelve Mile Creek
TlITRATICH
6

Tt Scoping Assessment — Twelve Mile Creek April 2010
crosses Shannon Drive (Upstream 5) and Waxhaw-Indian Trail Road (Upstream 4), median DO ranges
between 4.23 and 4.46 mg/L, or roughly 1 mg/L higher than the headwaters. By the time the creek crosses
NC16 one -quarter mile upstream of the WWTP outfall (Upstream 1), median DO concentration climbed
another 1 mg/L to over 5.4 mg/L. The median for Downstream 1 was over 5.6 mg/L. Note that the 20`h
percentile for Downstream 1 was 5 mg/L (meaning that 80 percent of the time it was above 5 mg/L),
whereas the 20`h percentile for Upstream 1 was 4.2 mg/L.
Monitoring has also been conducted in the South Carolina portion of Twelve Mile Creek. Between May
and August 2002, 38 measurements -were made at the bridge crossing in South Carolina at SC29-93
(approximately 2 miles below the discharge). The median concentration was 4.8 mg/L, compared with
median concentrations of 3.1 mg/L immediately upstream of the WWTP outfall and 5.1 mg/L at SR1301
one -quarter mile downstream of the discharge for the same period. Between May and August 2003,
37 measurements at SC29-93 generated a median concentration of 6.5 mg/L compared with median
concentrations of 6.7 mg/L immediately upstream of the WWTP outfall and 6.8 mg/L at SR1301
one -quarter mile downstream of the discharge for the same period.
In 2007, 75 measurements were taken between mid -June and the end of September further downstream in
South Carolina at SR521 (about 5 miles downstream of the outfall) and at the Hwy 55 crossing outside
Van Wyck (roughly 13 miles downstream). Median concentrations at these locations were 5.2 mg/L and
5.1 mg/L, respectively, compared with median concentrations of 3.5 mg/L immediately upstream of the
WWTP outfall and 5.7 mg/L at SR1301 one -quarter mile downstream.
In addition to routine instream DO monitoring, county staff did some investigative work to look for
factors that may be impacting instream DO levels. The county documented portions of the watershed
where a large portion of land is covered with poultry litter, locations where cattle and horses have access
to stream channels, and several locations where stream or tributary flow is obstructed by woody debris
particularly as flow levels decrease. Several photos taken by the county illustrate obstructions and sources
/ of organic material (see examples in Figure 2 and Figure 3). A primary conclusion reached by county
monitoring staff during their 2009 intensive summer monitoring is that during low flow conditions, debris
dams and other obstructions slow stream velocity in many locations decreasing reaeration rates and
providing longer residence time for organic material to decay and draw down DO concentrations (internal
memo from John Hahn; and personal communication with Nelson Baker, 2/2/10).
Figure 2. Field with Poultry Litter Recently
Applied
TITRAT1CH
Figure 3. Woody Debris Obstructing Tributary
Flow
7

eistN
Tt Scoping Assessment— Twelve Mile Creek April 2010
2.2.3 County - DWQ Permitting Correspondence
The May 18, 2007 letter from Susan Wilson (former Supervisor of the Western NPDES Program for
DWQ) referenced monitoring data collected prior to that time that revealed concentrations below the NC
water quality standard of 5 mg/L daily average. Ms. Wilson further stated that a "percentage of the
downstream dissolved oxygen values were lower than upstream values, indicating that the existing
WWTP discharge is having an adverse impact on dissolved oxygen levels in Twelve Mile Creek." She
also indicated that DWQ was unable to successfully model the receiving stream, and because of that fact
and the substandard instream conditions, DWQ was not willing to provide speculative limits for
wastewater expansion. Several alternatives to increased discharge into Twelve Mile Creek were proposed
for consideration by Union County including pumping discharge down to the Catawba River.
In November 2008, county representatives met with Tom Belnick (new Supervisor of the Western
NPDES Program for DWQ), and followed up with a letter to Mr. Belnick from Mr. Mark Tye, Assistant
Public Works Director. One alternative that the county posed in that correspondence was to use the
Twelve Mile Creek effluent to increase DO levels upstream by pumping a portion of the effluent and
discharging it upstream of the current outfall.
2.2.4 Preliminary Discussion
The primary question at hand is whether there is assimilative capacity in Twelve Mile Creek for an
rx\ expanded wasteflow from the county's WWTP. There is a substantial amount of monitoring data that
demonstrate that DO concentrations in Twelve Mile Creek frequently drop below 5.0 mg/L during
summer periods when flows are low. This is observed both upstream and downstream of the Twelve Mile
ems Creek WWTP outfall, and the county does not dispute this fact. A key consideration, however, is whether
elat, the county's effluent is contributinto lower downstream DO concentrations that occasional) dro
below the North Carolina and SoutiLCarolina standards, or whether the efuent may a helping DO
'AN conditions overall in the receiving waters.
It is premature to fully accept the DWQ NPDES Permit Program premise that a "percentage of the
downstream dissolved oxygen values were lower than upstream values, indicating that the existing
WWTP discharge is having an adverse impact on dissolved oxygen levels in Twelve Mile Creek." This
Oft\ premise does not acknowledge that instream DO concentrations are a function of fate and transport
processes. In this case, there are other sources of organic material in addition to the WWTP that
contribute to biochemical oxygen demand (BOD) in the receiving stream. Additionally, slugs of low DO
`elt water can move downstream through advective transport. In particular, summer precipitation events can
result in runoff that pushes lower DO volumes downstream and can increase loads of BOD from nonpoint
sources that further decrease instream DO. For example, these processes appear evident in the county
monitoring data collected in August 2007 when prior to a precipitation event on 8/22/2007 upstream DO
concentration was 1.4 mg/L, Downstream 1 was 5.7 mg/L indicating an immediate impact from the
higher DO effluent, and Downstream 2 was 5.4 mg/L. Following the event on 8/23/2007, upstream DO
increased to 3.5 mg/L and Downstream 1 decreased to 3.7 mg/L and Downstream 2 to 4.0 mg/L.
Therefore, at a scoping level it is better to compare long-term central tendencies (e.g., medians) than
discrete observations in order to understand general DO patterns in the receiving stream.
Because of the multiple factors that affect instream DO concentrations (i.e., transport rates, reaeration
rates, sediment oxygen demand rates, BOD and nitrogen decay rates, sources of BOD and ammonia), fate
and transport models have been developed by USGS, USEPA and others to simulate these interactions.
DWQ has indicated that it had not been able to develop a model that was capable of simulating DO well
in Twelve Mile Creek. The DWQ NPDES permit file contains documentation that shows that efforts were
''N made with a relatively course Streeter -Phelps -based model (referred to as a Level B model by DWQ). The
Level B model is based on general assumptions for hydrology and instream kinetics, so it is not surprising
® TIFTRATOCH 8

Tt Scoping Assessment — Twelve Mile Creek April 2010
that it did not replicate conditions well in the relatively unique Twelve Mile Creek. A more representative
modeling analysis is required.
With regard to pumping the water upstream, there are numerous challenges to evaluating this. As the
2009 county data show, lowest DO concentrations on average are found all the way up near the
headwaters of Twelve Mile Creek. Additionally, low DO is found in many of the tributaries such that
even if a portion of the discharge were pumped upstream to the mainstem of one or both forks of Twelve
Mile Creek, tributary DO would likely remain low. Evaluating the overall effect of such an option would
require intensive monitoring of flow -velocity relationships, sources of BOD, SOD, decay rates, etc., so
that a reliable modeling analysis could be conducted to answer this question. For this scoping level
analysis, Tetra Tech focused on evaluating assimilative capacity below the existing outfall location.
ci=TRAMP'
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Tt Scoping Assessment — Twelve Mile Creek April 2010
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TRRAT■CH
10

Tt Scoping Assessment — Twelve Mile Creek April 2010
3 Scoping Level Modeling Analysis
3.1 FIELD RECONNAISSANCE
3.1.1 Purpose
Tetra Tech had three primary objectives in conducting its field survey to support model development:
1. Obtain channel cross -sections to support estimation of depth during summer periods when stream
width below the outfall drops to 10 to 15 feet (stream description provided by Nelson Baker,
personal communication with Trevor Clements on February 2, 2010).
2. Observe channel features to support scoping model reach delineation:
a. Identify locations of noticeable elevation changes (e.g., falls).
b. Note locations and length of pooling areas.
c. Note upstream and downstream locations of significant changes in other channel features
(e.g., width).
3. Observe condition of channel bottom material to help with estimates of sediment oxygen demand
and channel roughness.
3.1.2 General Description of Field Survey Methods
Tetra Tech field staff collected data using the following general methods:
1. Record general site information
a. GPS coordinates were recorded using a hand-held GPS unit, and entered manually for
backup on a site description field worksheet.
b. Photographs were taken of upstream and downstream features for each site using a digital
camera, recording digital photo numbers on the field worksheets.
2. Channel cross-section measurement
a. Benchmark stakes were set and flagged with orange tape at the top of each bank for each
site. GPS coordinates were recorded at the benchmark locations.
b. Measuring tape was strung across the stream channel from one benchmark to the other
(Figure 4).
c. Elevations of the channel bottom along each cross-section transect were surveyed by one
field staff member using a site level, while the other field staff member waded across the
stream channel under the tape holding the staff rod to provide the survey target at key
locations along the transect. Highest resolution of the stream bottom shape was obtained
for 10 feet on either side of the channel thalweg.
3. Channel elevation
a. Additional channel elevations were surveyed using the site level and rod to record
thalweg elevation at measured distances (>_ 100 ft) upstream and downstream of each
cross-section. This information helped with refinement of reach slope.
4. Channel substrate material
a. Field staff used a shovel to dig out a sample of substrate from the central channel (i.e.,
within 5 ft either side of the thalweg), and then took a photo of the sample with a
reference for size (e.g., shovel showing in the photo).
b. Notes were then made on the site field sheet regarding substrate composition (silt, sand,
organic material, pebble, rock).
11

oak
likk
Tt Scoping Assessment — Twelve Mile Creek April 2010
Figure 4. Cross Section at Site 01, Upstream of the WWTP Discharge
3.1.3 Field Measurements and Observations
Tetra Tech collected cross sectional measurements at six locations on Twelve Mile Creek on March 9 and
March 10. 2010 (Table 2 and Figure 5). (Note: the reaches shown in the figure are described in
Section 3.2.)
Table 2. Location of Cross Section Measurements on Twelve Mile Creek
Site ID
Description
Latitude
Longitude
01
Upstream of WWTP discharge
34.949183°
80.76282°
02
Downstream of WWTP discharge
34.94973°
80.76424°
03
Upstream of the SR1301 bridge
34.94502°
80.77159°
04
Downstream of the SC29-93 bridge
34.92709°
80.79897°
05
Downstream of the Hwy 521 bridge
34.91537°
80.81623°
06
Upstream of Van Wyck Road bridge
34.85963°
80.85178°
12

Tt Scoping Assessment — Twelve Mile Creek April 2010
Two. PA. Cs* A.M.
0 0.25 0.5
Legend
0 X-Section Locations
Model Reach IDs
A
- B
C
D
E
F
G
H
O NC_boundary
County Boundary
Six Mile Creek Subwatershed
Twelve Mile WWTP Subwatershed
Twelve Mile Watershed
1.5 2
Miles
Figure 5. Location of Channel Cross Section Measurements on Twelve Mile Creek
T1TRATittOi
13

Tt Scoping Assessment — Twelve Mile Creek
April 2010
Cross section measurements were input to the Winxspro 3.0 Channel Cross Section Analyzer program.
Figure 6 shows a plot of the data collected, with zero station (0.0) at left -bank floodplain, facing
downstream. Similar plots were generated for the other five cross sections (Appendix A).
Figure 6. Plot of Cross Section Data for Site 01, Upstream of the WWTP Discharge
3.2 MODEL SETUP
The QUAL2E model (Brown and Barnwell, 1987) was selected for a steady-state simulation of the fate
and transport of the WWTP discharge and its impacts on the dissolved oxygen balance for Twelve Mile
Creek. The application of QUAL2E is well established in North Carolina and USEPA Region 4, and can
be set up quickly to conduct a scoping level modeling analysis. The key parameters that impact
simulation of dissolved oxygen are 1) the average depth and velocity of each model reach, 2) the water
quantity and water quality of the receiving stream and the effluent, and 3) the rates of reaeration, sediment
oxygen demand, and deoxygenation. This section summarizes the methods used to set up the QUAL2E
model and estimate these parameters.
3.2.1 Reach Delineation
The QUAL2E model simulates fate and transport of chemicals in uniformly spaced increments that make
up modeling reaches. Conditions within each reach are generally consistent with respect to channel slope,
width, depth, and velocity. For this scoping level modeling analysis, reach breaks corresponding to
changes in channel slope were estimated from 10-meter LIDAR (light detection and ranging) contour data
measured along the top of bank for the entire length of the channel. Figure 7 shows the elevation data
measured along the left bank with the average -slope trendline for each reach (A through 1). Though this
coarse analysis generates a longitudinal profile with considerable "noise," the general pattern of elevation
change provides a good indication of average channel slope.
TRTRATOCH
14

Tt Scoping Assessment— Twelve Mile Creek
April 2010
510.00
500.00
490.00
480.00
° 470.00
w
460.00
450.00
440.00
430.00
tLeft Bank
Rch A
Rch C
1'
I
Rch B . .
t
♦ ..i
•
♦
1s >
Rch
D
r Rch E
I"--Ia
Rch G
Rch F
Rch Htilliiiiiiil
i
Rch l
0
10000
20000
30000
40000
Station (ft)
50000
60000
70000
80000
0011
0114
Figure 7. Slope Approximations Based on LIDAR Data
001*
For this system, the incremental length selected for the QUAL2E model is 0.1 miles. Because the
QUAL2E model limits the number of increments to 20 for each model reach, two of the slope -based
reaches were split so that the total reach length did not exceed two miles (20 * 0.1 mile = 2.0 miles).
Model reach lengths are summarized below in Table 3.
3.2.2 Reach Hydraulics
The average slopes estimated from the elevation data were input to Winxspro along with the nearest cross
section to estimate the average velocity and depth for each reach. The user must also input Manning's n
for this analysis. To determine the appropriate value for this system, Tetra Tech increased Manning's n
until simulated velocities under low flow conditions matched those measured by the USGS at the Twelve
Mile Creek gage at Station #02146900 for a substantial number of low flow (< 10 cfs) days (Figure 8).
This gage is located in a reach that has a channel slope of 0.0005 ft/ft based on the LIDAR analysis.
Reach D has the same slope, and was therefore selected for this comparison. Figure 8 shows the simulated
velocity (pink box) in Reach D assuming a Manning's n of 0.20. Note that this analysis is based on a
simulated flow of 5.5 cfs, which is the average of the low flow measurements reported by USGS,
excluding the outlier of 0.58 ft/s at a flow of 4.19 cfs.
®TIT Al a'
15
14
eft
Oak
Oft
r
r►
004
Iv

Tt Scoping Assessment — Twelve Mile Creek April 2010
Velocity (ft/s)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
USGS • Simulated
0
0
•♦
1
♦ •
2
♦ • ♦
4 6
Flow (cfs)
8
10 12
Figure 8. Comparison of Simulated and Observed Low Flow Velocities with Manning's n = 0.2
Manning's n values are typically in the range of 0.02 to 0.06 for unobstructed stream channels. A
Manning's n of 0.20 indicates that significant obstructions are present that are slowing the movement of
the water. During the field visit in March, Tetra Tech observed several locations where excessive material
could be seen at the water surface. During low flow conditions, obstructions that may not have been
evident during the March event likely -Ea -Cie significant act on the passage of low flow volumes.
Figure 9 shows an example of debris that was visible in the channel in the vicinity of cross section'02.
Field notes from another location indicate the presence of eight groups of debris within the line of sight of
the cross section measurement taken downstream of Highway 521 (these photos are not shown because
they are difficult to decipher due to poor light conditions present at dusk when the photos were taken).
Figure 9. Example of Obstructions in Twelve Mile Creek that Influence Velocity (near Site 2)
nTIITRATSCH
16

Tt Scoping Assessment - Twelve Mile Creek
April 2010
August 2009 represented a recent period when flow conditions were low and water quality patterns were
typical of summer conditions. Based on flow measured at the USGS Six Mile Creek gage of 0.7 cfs
between August 18 and 27, 2009, flow in the Twelve Mile Creek above the effluent discharge was
estimated at 1.35 cfs based upon drainage area apportioning. The WWTP flow reflects 2009 average daily
flow reported in the NPDES permit application. Flow assumptions are summarized in Table 3.
/11
Iv
Table 3. Summary of Model Flow Input Assumptions 014
Model Input
Twelve Mile Creek Above
the Effluent Discharge
Six Mile Creek
WWTP
Flow (cfs)
1.35
0.7
5.26
Table 4 summarizes the hydraulic parameters for each QUAL2E modeling reach (1 through 11) for the
August 2009 typical low flow condition (headwater flow of 1.35 cfs plus effluent discharge flow rate of
5.26 cfs equals total channel flow of 6.6 cfs).
Table 4. Hydraulic Parameters for the QUAL2E Modeling Reaches
QUAL2E
Reach
Slope-
based
Reach
Corresponding
Cross Section
Reach
Length
(mi)
Average
Reach
Slope (ft/ft)
Average
Velocity
(ft/s)
Average
Depth (ft)
1
A
02
1.4
0.0008
0.21
1.05
2
6
03
0.7
0.0003
0.15
1.22
3
C
03
1.0
0.0011
0.21
0.86
4
D
04
1.9
0.0005
0.20
1.38
5
D
04
1.9
0.0005
0.20
1.38
6
E
05
1.8
0.0001
0.09
1.67
7
E
05
1.8
0.0001
0.09
1.67
8
F
05
0.6
0.0022
.0.26
0.66
9
G
06
1.3
0.0003
0.13
1.05
10
H
06
0.7
0.0008
0.17
0.78
11
I
06
1.5
0.0007
0.17
0.80
3.2.3 Water Quality Model Input Assumptions
Along with water quantity information, the QUAL2E model uses the water quality of the receiving stream
and all point source discharges to drive the fate and transport simulation. Table 5 sumtarizes the
upstream, WWTP, and Six Mile Creek water quality inputs to the system. Upstream temperature and DO
nTETRA
17
Oft
11.
eh-
410.
Aims
006,
Oak
Ask

ink
Tt Scoping Assessment — Twelve Mile Creek April 2010
concentration assumptions were based on four observations each by Union County during the period
^ between August 18 and 27, 2009. Upstream concentrations for ammonia, nitrate -nitrite, and organic
,.� nitrogen were assumed to reflect the long term data collected by DWQ and reported in their Catawba
River Ambient Monitoring System Report (NCDENR, 2008) at Station Number C9819500 in Twelve
Mile Creek upstream of the discharge (represents reported mean of 60 observations). Background
..� conditions in Six Mile Creek were estimated to be the same as Twelve Mile Creek. Observations of
upstream and Six Mile Creek BOD5 and BOD ultimate concentrations were not available, so model input
Alk assumptions were based upon data available for a similar piedmont stream system (Tetra Tech, 2008).
Aft Effluent (WWTP) temperature and DO were also taken from data collected by the County for the period
between August 18 and 27, 2009. Ammonia, nitrate -nitrite, organic nitrogen, and BOD5 concentrations
for the effluent input were based upon information provided in the January 10, 2010 NPDES permit
application, which provided averages for 955 observations (from which representative summer values
were estimated). BOD ultimate concentration for the effluent was estimated by multi • 1 in: the B • D5
0814
concentration by 2.47 w . lc is e -ratio recommen • - • i omann ' . ' an • .A. Mueller (1987) for
�* c• g : • to BOD ultimate for this type of discharge.
sok Table 5. Water Quality and Typical Summer Flow Rates Assumed for the Twelve Mile Creek
QUAL2E Model
Allek
Oki
aw
Oak
4114,
Model Input
Twelve Mile Creek Above
the Effluent Discharge
Six Mile Creek
WWTP All
Temperature (°F)
75.9
75.9
76.3
DO (mg/L)
3.3
3.3
6.5
Ammonia (mg-N/L)
0.05
0.05
0.1
NO3 plus NO2 (mg-N/L)
0.34
0.34
4.03
Organic N (mg-N/L)
0.46
0.46
1.2
BOD5 (mg/L)
No instream measurement.
Use BODult = 0.75 mg/L
No instream
measurement. Use
BODult = 0.75 mg/L
0.80
BODult (mg/L)
1.98
3.2.4 Methods for Estimating Model Kinetics
Primary kinetic parameters for BOD-DO simulation in QUAL2E are the deoxygenation rate (kd) for
Ask
carbonaceous BOD, reaeration rate (ka), and sediment oxygen demand (SOD). Table 6 summarizes the
.� model assumptions for these key reaction rates.
�► Model rates for IQ were calculated for each reach based on the Bosco equation, which incorporates slope,
velocity, and depth into the estimation of kd (USEPA, 1985).
The QUAL2E model provides the user a choice of eight simulation options for estimating ka for each
modeling reach when measured values are not available. The Thackston and Krenkel method was selected
for this analysis because field data collected from a North Carolina Piedmont stream with similar channel
characteristics indicate that this method provides a good estimate of reaeration for wide, relatively low -
sloped channels (Tetra Tech, 2008).
SOD was used as a calibration parameter to adjust simulated dissolved oxygen concentrations to expected
�► ranges based on the median DO concentrations from 75 measurements collected in Twelve Mile Creek at
411164
18

114
odk
Tt Scoping Assessment — Twelve Mile Creek April 2010
one upstream and four downstream stations June through August 2007. To simulate observed DO
measurements in this channel, the rate of sediment oxygen demand was set to 0.25 L/d at 20 °C.
Table 6. Summary of Model Kinetic Rate Assumptions
QUAL2E
Reach
kd (1/d)
ka (1/d)
SOD (1/d)
1
0.057
4.47
0.25
2
0.042
2.60
0.25
3
0.071
5.70
0.25
4
0.045
3.05
0.25
5
0.045
3.05
0.25
6
0.035
1.05
0.25
7
0.035
1.05
0.25
8
0.135
9.90
0.25
9
0.042
2.68
0.25
10
0.059
5.10
0.25
11
0.056
4.95
0.25
3.2.5 Baseline Model Calibration Fit
Figure 10 compares the QUAL2E model output to observations collected in Twelve Mile Creek during
the summer of 2007 (median, 10th percentile, and 90th percentile). This model seems to approximate
conditions in Twelve Mile Creek fairly well and as a scoping level model, should be sufficient to test the
impacts of various scenarios regarding effluent quantity and quality on simulated dissolved oxygen
concentrations. N that the model redicts a ra id decline in dissolved oxygen concentration from mile
6.8 to 10.4 because the slope of this_ reach is very low relative to the rest o t e mo e t t .
Unt' n ortuniate yy, road access in this section is limited and there are no monitoring data to confirm w�iether
or not dissolved oxygen decreases to 2 mg/L in this section during the summer months.
19
oft
oft
oft
eft
/wk
01/4
101.4
0.14
oft
.004
Oft
oft
oft
P`

Tt Scoping Assessment — Twelve Mile Creek April 2010
Simulated DO Observed Summer 2007 DO Pattern
90th percentile
Median
�10'h percentile
-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Distance (mi)
Figure 10. Comparison of Simulated and Observed Dissolved Oxygen in Twelve Mile Creek
3.2.5.1 Model Sensitivity
A model analysis was conducted to observe how sensitive DO predictions are to changes in the three
primary kinetic parameters: deoxygenation rate (kd), reaeration rate (ka), and SOD. To perform the test,
each parameter's specifications were decreased and increased by 20 percent, respectively.
Figure 11 through Figure 13 show the impacts of varying each kinetic rate on simulated dissolved oxygen
concentrations for the existing actual scenario. The analysis indicates that DO predictions are not very
sensitive to the kd rate (Figure 11), which is not pr rising since instreanlroirartmate concentrationsons
are not that hig .
Predicted DO is about equally sensitive to ka and SOD rates (Figure 12 and Figure 13). A 20 percent
increase or decrease in either parameter produces a change in DO of approximately 0.5 to 1.0 mg/L
depending on reach location. There does not appear to be significant bias such that the model should be
able to be applied for scoping level assimilative capacity analysis, focusing on relative differences
between modeling scenarios.
20

Tt Scoping Assessment — Twelve Mlle Creek
April 2010
—Existing --Increase Kd by 20%
cJ Observed DO Summer 07 —.Decrease Kd by 20%
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Distance (mi)
Figure 11. Impacts of Varying the Deoxygenation Rate by 20 Percent
—Existing —Increase Ka by 20%
El Observed DO Summer 07 - --- Decrease Ka by 20%
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Distance (mi)
Figure 12. Impacts of Varying the Reaeration Rate by 20 Percent
oITTRATOCH
21

Tt Scoping Assessment — Twelve Mile Creek
April 2010
7
6
5
J
4
E
O 3
0
2
1
0
Existing
Increase SOD by 20%
• Observed DO Summer 07 - Decrease SOD by 20%
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Distance (mi)
Figure 13. Impacts of Varying the Sediment Oxygen Demand Rate by 20 Percent
3.2.6 Model Application
3.2.6.1 Scenario Description
Two rimary Scoping questions need to be answered:
there a sag in DO concentration below the outfall that is increased by the WWTP discharge?
oes DO concentration in the receiving waters improve with increased wasteflow?
The following scenarios were set up and run to help answer the questions.
1) Existing Actual Conditions: Model setup reflects existing average WWTP discharge flowrate
(3.4 MGD) and quality (Table 5).
2) Zero Discharge: Model setup reduces WWTP discharge flow rate to 0 MGD.
3) Existing Permitted Conditions: Model setup reflects an increase in WWTP discharge flow rate to
6 MGD with permit limits for dissolved oxygen (6 mg/L), BOD5 (5 mg/L), and ammonia
(1 mg-N/L).
4) Expanded Flow: Model setup reflects an increase in WWTP discharge flow rate to 15 MGD with
permit limits for dissolved oxygen (6 mg/L), BOD5 (5 mg/L), and ammonia (1 mg-N/L).
3.2.6.2 Scenario Results
Figure 14. shows the impacts of the four modeling scenarios on simulated dissolved oxygen
concentrations. Comparison of the existing actual discharge scenario (green line) to the zero discharge
scenario (blue line) indicates that DO concentrations would be expected to be far lower under typica
summer conditions, ranging between approximately 1.0 and 4.0 mg/L depending on reach location. The
difference be between existing actual and existing permitted conditions (green line versus magenta line), on
TITRATSCH
22

Tt Scoping Assessment — Twelve Mile Creek
April 2010
the other hand, is almost negligible. panding the wasteflow to 15 MGD (orange line) would largely be
expected to increase DO downstream of the outfall by roughly 0.1 to 0.8 mg/L depending on the reach --
location.
—Existing Actual (Qeff= 3.4 MGD) ----• Zero Discharge (ktcKy uu O
Existing Permitted (Qeff = 6.0 MGD) Observed DO Summer 07
Expanded Flow (Qeff = 15 MGD)
7
6
5
J
4
E
O 3
0
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Distance (mi)
Figure 14. Simulated Dissolved Oxygen Concentrations for Four Modeling Scenarios
Appendix B contains the model input and output files for each of the baseline and scenario runs.
®T,,,W„a
23

Tt Scoping Assessment — Twelve Mile Creek April 2010
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24

Tt Scoping Assessment — Twelve Mile Creek April 2010
4 Conclusions and Discussion
The modeling results suggest that the existing Union County WWTP discharge does not cause DO to
worsen downstream of the outfall. To the contrary, the discharge appears to significantly increase DO
concentrations over what would be expected without the effluent flow present in the channel. This is a
result of increased flow velocity produced by the effluent that in turn increases reaeration without
substantially increasing BOD ultimate to offset the increased reaeration.
Furthermore, the scoping model results suggest that DO concentrations would be expected to further
increase with the addition of effluent treated to the same tertiary levels as the current effluent. This would
suggest that there is assimilative capacity for increased discharge to Twelve Mile Creek, and that the
effluent should be considered a valuable resource to be utilized rather than a nuisance to be disposed of,
potentially by pumping it 14 miles downstream to the Catawba River.
From an overall community sustainability perspective, putting water back to good use in the watershed is
preferred to pumping the water down to the Catawba River. Core principles for sustainable water
management include valuing the resource, providing multiple benefits, and achieving a triple bottom line
(environmental protection, economic viability, and social acceptance). Pumping water down to the
Catawba treats the water as a waste to be disposed of rather than a resource that can provide multiple
benefits. Additionally, building and operating a 14-mile pipeline increases the plant's carbon footprint
rather than reducing it, and increases the amount of infrastructure that must be operated and maintained
(and that is expensive to replace down the road).
A more sustainable concept would be keeping the wastewater treatment system close to the source of the
water and using it for multiple purposes including irrigation, nonpotable industrial and commercial use,
groundwater recharge, wetland creation, habitat restoration, and public amenities (gardens, parks,
recreation areas, etc.). Keeping systems close together and not using potable water for all water uses
typically reduces energy use, is cheaper to build and operate, and provides for an increased quality of life
for the public if multiple benefits are employed. Some communities are now building distributed
wastewater systems to achieve these objectives. Building smaller systems that are designed, built,
operated and maintained by a central responsible management entity allows for "just in time" service (i.e.,
do not have a large facility that is well below capacity for many years) and more sustainable operations. If
the effluents from these facilities are used for other purposes that ultimately allow for infiltration to the
ground rather than being directly discharged to streams, there is a better chance of helping maintain
natural water tables and baseflows during the summer (a significant issue in the Twelve Mile Creek
watershed).
It is the recommendation of Tetra Tech that Union County re -initiate talks with DWQ regarding keeping
the effluent within the watershed. Options to reuse the wastewater, perhaps by incorporating a more
distributed system in conjunction with other infrastructure (water supply and stormwater), or in
discharging highly reclaimed water to support restoration of Twelve Mile Creek under summer low flow
conditions appears much more likely to achieve triple bottom line sustainability goals than does the
alternative of pumping the water to discharge to the Catawba River.
® TRRATICH
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Tt Scoping Assessment — Twelve Mile Creek April 2010
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IDTETRATIICH
26

Tt Scoping Assessment — Twelve Mile Creek April 2010
5 References
Brown and Barnwell. 1987. The Enhanced Stream Water Quality Models QUAL2E and QUAL2E-
UNCAS: Documentation and User Manual. EPA/600/3-87/077, May 1987.
NCDENR. 2008. Basinwide Assessment Report — Catawba River Basin. North Carolina Department of
Environment and Natural Resources DWQ Environmental Sciences Section.
USEPA. 1985. Rates, Constants, and Kinetics Formulations in Surface Water Quality Modeling (Second
Edition). EPA/600/3-85/040, June 1985.
USGS. 2002. U.S. Geologic Survey stream flow estimates for Twelve Mile Creek (Station #02146900)
and Six Mile Creek (Station #021469901). Letter from Curtis Weaver, USGS Hydrologist, to McKim and
Creed (July 15, 2002).
Tetra Tech. 2008. Results of Phase 1 Field Monitoring and Model Updates for the High Point Westside
Discharge to Rich Fork Creek. Prepared for the City of High Point, NC.
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Tt Scoping Assessment — Twelve Mile Creek April 2010
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28

Tt Scoping Assessment — Twelve Mile Creek April 2010
Appendix A. Channel Cross Sections
cinrnualai
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Tt Scoping Assessment — Twelve Mile Creek April 2010
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Tt Scoping Assessment - Twelve Mile Creek
April 2010
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Tt Scoping Assessment - Twelve Mile Creek
April 2010
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Tt Scoping Assessment — Twelve Mile Creek April 2010
Appendix B. QUAL2E Model Input and Output
Table of Contents
Existing Actual Input File B-3
Existing Actual Output File B-7
Existing Permitted Input File B-44
Existing Permitted Output File B-48
Expanded Flow Input File B-85
Expanded Flow Output File B-89
Zero Effluent Discharge Input File B-126
Zero Effluent Discharge Output File B-130
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Appendix B of the Scoping Level Assessment Report (Tetra Tech,
2010) has not been included as part of this Technical Memorandum
to limit page count. The Appendix in its entirety (165 pages) will be
provided upon request.
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Twelve Mile Creek WWTP Expansion Alternativestit\ RAM AND
(�,� YE
August 2010 AIi�� 1 �l
Environmental Engineers & Scientists
PA.1
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Letter of Request for Speculative Limits
June 2010
Twelve Mile Creek WWTP Expansion Alternatives
August 2010
HAM AND SAWYM
Environmental Engineers & Scientists

HAZEN AND SAWYER
Environmental Engineers & Scientists
June 16, 2010
Mr. Tom Belnick, Supervisor
Complex Permitting Unit
Surface Water Protection Section - NPDES
Division of Water Quality
N.C. Department of Environment and Natural Resources
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
Dear Mr. Belnick:
Hazen and Sawyer, P.C.
4944 Parkway Plaza Blvd.
Suite 375
Charlotte, NC 28211
i 7041357-3150
(1041 357-3152 (Fax)
Re: Request for Speculative Limits
Twelve Mile Creek VWVTP
Union County, North Carolina
NPDES Permit No. NC0085359
On behalf of Union County, Hazen and Sawyer would like to thank you for meeting with us
on June 8th, 2010 to discuss the expansion options for the County's Twelve Mile Creek
Wastewater Treatment Plant (VWViTP). As discussed in the draft report for the Expansion
Alternatives Development Study that we left with you for your review, the County has been
pursuing several options for disposal and/or diversion of projected future wastewater flows in
the Twelve Mile Creek WWTP service area. These options range from diverting raw sewage
to other wastewater treatment plants operated by neighboring utilities to pumping treated
effluent directly to the Catawba River.
The County has also been diligent over the past three years in collecting dissolved oxygen
data in the creek both upstream and downstream of the current discharge. Using this data, a
scoping level model of additional treated effluent discharge into the creek was completed as
part of our alternatives analysis. Since the results were favorable, we would like to request
reconsideration of increasing discharge flows into Twelve Mile Creek.
Based on the above and your recommendation for continuing this discussion, we are hereby
requesting speculative NPDES discharge limits for an expansion of the VWVTP's current
permitted capacity of 6.0 mgd to future expanded total capacities of 9.0, 12.0, and 15.0 mgd
(i.e., increasing discharge by 3, 6, and 9 mgd) to account for near -term and long-term
wastewater needs. Since expansion of the current discharge represents one of the most
favorable options in terms of capital costs, O&M costs, and overall sustainability, the County
is willing to discuss a range of options for improvements and control within the watershed to
ensure long-term environmental protection of the creek.
T9elnick 061610 itr.Cacx
NEW York, NY • Philadelphia, PA • Raleigh, NC • Charlotte, NC • Greensboro, NC • Greensboro, NC • Charleston, SC • Atlanta, GA • Fairfax, VA • Hampton Roads, VA • Baltimore, MO • Cincinnati, OH • Hollywood, FL • Boca Raton, FL • Miami, Fl.

HAZEN AND SAWYER
Mr. Tom Belnick
Page 2 of 2
Thank you for review of this request for speculative limits and for your assistance on this project.
If you have any questions or would like additional information, please do not hesitate to contact
me at 704-357-3150 or at istruve a.hazenandsawyer.com.
Very truly yours,
HAZEN AND SAWYER, P.C.
T1.
James N. Struve, P.E.
Vice President
cc: Mr. Ed Goscicki, Union County Public Works
Mr. Scott Huneycutt, Union County Public Works
Mr. Scott Alpert, Hazen and Sawyer
TBalruck 061610 Ilr docx