NC0063096_Speculative Limits_20100223

NPDES DOCUHENT SCANNING COVER SHEET
NC0063096
Holly Springs WWTP
NPDES Permit:
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Meeting Notes
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
February 23, 2010
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NCDENR
North Carolina aeparr►Y,errt of Environment and Natural Resources
Division of Water Quality
Cdeen H. Sullins Dee Freerrgn
aredor Secretary
February 23, 2010
Ms. Stephanie Sudano, PE,
Director of Engineering
P. O. Box 8
Holly Springs, NC 27540
Subject: Speculative Limits
Town of Holly Springs WWTP
Wake County
Dear Ms. Sudano:
This letter is in response to your request for speculative effluent limits for a discharge to the White Oak Creek
arm of Harris Lake, above New Hill -Holleman Road. You requested limits for flows of 6.0 MGD and 8.0 MGD
of treated wastewater.
The speculative limits presented here are based on our understanding of the proposal and of present
environmental conditions. In providing this information, the Division of Water Quality (DWQ) does not
guarantee that it will actually issue an NPDES permit for this discharge, or that the effluent limitations will be
just as presented here. The Division will make final decisions on these matters only after it receives and
evaluates a formal NPDES permit application for the expanded discharge and considers any public comments
on the proposed permit conditions. The Town must also obtain other approvals prior to submitting its permit
application to the Division (see below).
Environmental Assessments of New and Expanding Treatment Facilities
As you know, the Town must evaluate and address the potential environmental impacts of this project before
receiving a modified permit. Anyone proposing to construct new or expanded wastewater treatment facilities
using public funds or public (state) lands must first prepare an environmental assessment (EA) when
wastewater flows (1) equal or exceed 0.5 MGD or (2) exceed one-third of the 7010 flow of the receiving
stream. The Division will not accept a permit application for a project requiring an environmental assessment
until it has approved the EA and sent a Finding of No Significant Impact (FONSI) to the State Clearinghouse
for review and comment. Further, we cannot modify or issue the permit until the Clearinghouse has approved
the FONSI. Please contact Ms. Hannah Stallings of DWQ's Planning Section for further information regarding
the requirements of the N.C. Environmental Policy Act. You can reach Ms. Stallings directly at [phone],
or by email at [e-mail].
1617 Mail Service Center, Raleigh, North Carolina 27699`1617
!.oration: 512 N. Salisbury St Raleigh, North Cardina27604
Ranee 919-807-63001 FAX: [phone] O stc rer Service:1-877.MS6748
Internet vwtw.nomaterquality.org
No NthCarolina
attire,

Engineering Alternatives Analysis (EAA)
The Town's EA must include an approvable engineering alternatives analysis (EAA), performed according to
the guidelines in our website (see link below). This includes a 20-year present worth analysis of land
application options. The Division must approve an EAA before issuing or modifying any permit to authorize the
discharge of new or expanding flows. The purpose of the EAA is to justify the proposed wastewater flow rate
and provide a detailed analysis of treatment and disposal alternatives, including a thorough evaluation of non -
discharge and other alternatives such as spray irrigation, water conservation, and inflow and infiltration
reduction. In accordance with the North Carolina General Statutes, the preferred alternative must be the
practicable waste treatment and disposal alternative with the least adverse impact on the environment. Non -
discharge and other alternatives to discharge are considered to be environmentally preferable to a surface
water discharge. You can find this and other permit -related information at the NPDES Unit website:
http://www.ncwateraualitv.orq/NPDES/.
Speculative Effluent Limitations
Based on the available information, speculative limits for a 6.0 and an 8.0 MGD discharge from the Town of
Holly Springs WWTP into Harris Lake, classified as Class C waters, are according to the following table:
Table 1. Summary of Speculative Effluent Limitations for both 6.0 MGD and 8.0 MGD
` .` ,.
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a 3 f
' , ' { r SPECULATIVE. '
r EFFLUENT LIMITA lOf1S-
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t
Flow
6.0/8.0
MGD
BOD, 5-day, 202C '
5.0 mg/L
7.5 mg/L
Ammonia - Nitrogen
1.0 mg/L
3.0 mg/L
Total Suspended Solids 1
30.0 mg/L
45.0 mg/L
Dissolved Oxygen
Minimum 7.0 mg/L (daily average)
pH
Within the range of 6.0 to 9.0 standard units at all times
Fecal Coliform
(Geometric mean)
200/100
mL
400/100
mL
Total Residual Chlorine 2
28 pg/L
Total Nitrogen
5.0 mg/L
Total Phosphorus
0.5 mg/L
Orthophosphorus
0.27 mg/L
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604
Phone: [phone] FAX: [phone] Customer Service: 1-877-623-6748
Internet: www.ncwaterquaiity.org
An Equal Opportunity 1 Affirmative Action Employer
NohCarolina
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Footnotes:
(1) BOD and TSS include a minimum of 85% removal on a monthly average basis.
(2) Total Residual Chlorine limit applies if chlorine or chlorine derivative is used for disinfection. The
Division shall consider all effluent TRC values reported below 50 pg/I to be in compliance...
BOD5 and NH3-N: The monthly average limits for BOD5 and NH3-N (ammonia nitrogen) are based on
modeling results.
Total Suspended Solids (TSS): The limits for total suspended solids are standard for secondary treatment of
municipal wastewater.
Dissolved Oxygen: This limit was set to correspond to the minimum amount used in modeling
Fecal Coliform, pH: The limits for fecal coliform bacteria and pH represent water quality standards for Class C
waters (T15A NCAC 2B .0211).
Total Nitrogen, Total Phosphorus, Orthophosphorus: Nutrient limits are based on the modeling results.
If you have any questions about these limits, feel free to contact me at [phone], or by email at
gil. vinzani @ncdenr.gov.
Sincerely,
Gil Vinzani, PE
Eastern NPDES Program
Cc: Raleigh Regional Office, Surface Water Protection
Jennifer Haynie, DWQ Construction Grants and Loans
Alan Clark, DWQ/Planning
Central Files
NPDES Files
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604
Phone: [phone] FAX: [phone] \ Customer Service: 1-877-623-6748
Internet: www.ncwaterquality.org
An Equal Opportunity 1 Affirmative Action Employer
NorthCarolina
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INTEROFFICE MEMORANDUM
TO: Gil Vinzani, Eastern NPDES Unit
FROM: Pam Behm, Modeling & TMDL Unit (MTU)
SUBJECT: MTU Comments on Holly Springs Request for Speculative Limits to Discharge into
Harris Lake
DATE: 2/16/2010
CC: Matt Matthews, Alan Clark, Jennifer Haynie, Jeff Poupart, Danny Smith, Kathy
Stecker, Dianne Reid, Nora Deamer
The following sections provide a summary of the Modeling and TMDL Unit's (MTU) evaluation
of the proposed Holly Springs discharge into Harris Lake. DWQ received a request for
speculative limits on December 21, 2009.
The first section below provides a summary of the impacts using the three lake discharge
evaluation criteria that MTU used for this analysis. The second section below provides a
summary of the MTU recommendations for permit limits and monitoring frequencies. These
should be applied if the Division decides to move forward with speculative limits for the
proposed discharge given the impacts described below.
LAKE DISCHARGE EVALUATION CRITERIA
Does the proposed new discharge cause a violation of the chlorophyll -a standard?
The model predicts that there will be chlorophyll -a exceedances if the proposed total
phosphorus (TP) limit of 0.5 mg/L is 100% orthophosphate (PO4-P). The model indicates
that Harris Lake is highly responsive to phosphorus. The TP limit of 0.5 mg/L alone will
not be protective. The TP limit should be 0.27 mg/L.
Does the proposed new discharge cause chlorophyll -a concentrations to exceed the
proposed threshold of 25 ug/L at the 90th percentile?
For this analysis, the MTU looked at the 90th percentile for baseline vs. predicted
chlorophyll -a for the model segment receiving the discharge because this is where the
impact is most pronounced. As shown below in Figure 1, chlorophyll -a is below 15 ug/L
90% of the time for the baseline scenario. For the proposed discharge, using 0.27 mg/L
as the PO4-P concentration, the 90th percentile for Phase I (6 MGD) is about 20 ug/L and
about 22 ug/L for Phase II (8 MGD). Therefore, modeling indicates that the proposed

new discharge will not exceed the proposed chlorophyll -a threshold of 25 ug/L at the
90th percentile.
50
45
40
35
30
25
20
15
10
5
0
Chlorophyll a Duration Curve for White Oak Arm Discharge
® Baseline -0.5 mg/LTP 6mgd =0.5 mg/LTP 8mgd --- 90% —Standard
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Time < Value
Figure 1. Chlorophyll -a duration curve for the baseline and proposed discharge scenarios
(using 0.27 mg/L as the PO4-P concentration in the proposed discharge).
What is the impact of the proposed new discharge on dissolved oxygen?
Modeling indicates that there is very little impact on the dissolved oxygen
concentrations in the hypolimnion from the proposed discharge. Dissolved oxygen
concentrations in the proposed discharge ranged from 7.0 — 9.0 mg/L in the model.
MTU RECOMMENDATIONS
Maximum Limits (6 or 8 MGD)
Table 1 shows the maximum limits and monitoring frequencies that MTU recommends
should be used for speculative limits. These should be applied to both proposed phases
of the discharge and should be applicable year-round. The modeling submitted to DWQ
by Holly Springs used this approach (year-round limits and the same concentrations for
both phases).
2

Table 1. MTU Recommended Effluent Limits and Monitoring Frequency
Parameter
Concentration Limit
Monitoring
Frequency
Total Phosphorus
0.27 mg/L
Weekly
Ammonia
1 mg/L
Weekly
Total Nitrogen
5 mg/L
Weekly
Dissolved Oxygen
7 mg/L (minimum)*
Weekly
BOD
5 mg/L
Weekly
* Minimum value used in model, so this should be applied in the permit.
In -lake Monitoring
Downstream sampling on the White Oak Arm of Harris Lake should be required as well,
weekly from April -October, for the following parameters: depth profiles of dissolved
oxygen, temperature, conductivity, and pH and photic zone composite sampling for
total phosphorus, orthophosphate, total nitrogen, and chlorophyll -a.
3

MEMORANDUM CH211i71HILL
Responses to DWQ Modeling and TMDL Unit Comments on Holly Springs
Speculative Limits Request for Harris Lake
PREPARED FOR: Kathy Stecker/NC DWQ
PREPARED BY: CH2M HILL
COPIES: Town of Holly Springs
DATE: February 10, 2010
CH2M HILL received comments from North Carolina Division of Water Quality (DWQ) regarding the
analysis performed to support the request for speculative limits for a Holly Springs Wastewater
treatment plant discharge to Harris Lake. This memorandum responds to DWQ's comments on the
technical approach.
Comment 1:
Provide an evaluation of lake response for Phase I and Phase II scenarios using a discharge of 0.5
mg/L orthophosphate. This is considered a worst case scenario relative to the assumption used in
the technical memorandum which split the 0.5 mg/L total phosphorus into organic and inorganic
fractions. Provide the results for all three segments in the White Oak Creek arm of Harris Lake.
Response 1:
The modeling results presented on January 8'h, 2010 specified the fraction of phosphorus that was in
the readily available orthophosphate form as 55 percent. The reason for setting it at this level will be
discussed later in this response. To meet DWQ's request, the model was rerun with an input of 0.5
mg/L of orthophosphate (PO4-P). Since the model is sensitive to this form of phosphorus,
chlorophyll a levels increased. Under the Phase I discharge, the chlorophyll a levels remained below
25 µg/L at least 90 percent of the time. Under Phase II, the chlorophyll a levels remained below 25
µg/L approximately 86 percent of the time in the segment where the discharge would enter.
Chlorophyll a levels would remain below 25 µg/L at least 90 percent of the time in the other two
segments of White Oak Creek. Frequency plots of chlorophyll a are provided in Attachment 1.
Figures 1-1 through 1-3 show the comparison of chlorophyll a predictions for each of the three
segments used to represent the White Oak arm of Harris Lake in the CE-QUAL-W2. Timeseries plots
for these three segments are provided in Attachment 1 as Figures 1-4 through 1-6.
As mentioned earlier, the orthophosphate fraction was set at 55 percent for the speculative limits
request analysis. The plant uses a 5-stage Bardenpho system with cloth filters and chemical
additions to get the TP below 0.5 mg/L. This type of system will always have an organic phosphorus
component since not all of the organic matter, in the form of suspended solids, are removed.
Chemical additions, which remove PO4-P, are the primary means of removing phosphorus after the
filtration stage.

RESPONSES TO DWQ MODELING AND TMDL UNIT COMMENTS
A review of the Barderipho process was performed to estimate the ratio of PO4-P to TP. The 55
percent level was based on the following assumptions:
• The effluent total suspended solids (TSS) in the discharge would be 5 mg/L. Approximately
80 percent of this (4.0 mg/L) would be volatile suspended solids (VSS).
• The biological process results in approximately 4 to 6 percent of the VSS (0.16 to 0.24 mg/L)
being organic phosphorus.
• The biological process also yields soluble P concentrations of approximately 0.1 to 0.3 mg/L
if the TP levels are below 0.5 mg/L.
The modeling analysis used the high end of the range by assuming that 0.3 mg/L was PO4-P and 0.24
mg/L was organic P. This was considered to be a realistic representation of the Holly Spring
discharge. This results in a split of 55 percent orthophosphate and 45 percent organic or bound
phosphorus.
To aid in the removal of phosphorus, a plant can use metal salts to meet a permit limit of 0.5 mg/L.
This process uses iron sulfate or aluminum sulfate to bind PO4-P into a floc which will settle out of
the water column. This reduces the overall fraction of phosphorus in the PO4-P form since the PO4-
P component is removed but the inorganic or chemically bound fraction is increased.
Holly Spring is utilizing an aluminum sulfate process to reduce phosphorus levels. Studies have
shown that phosphorus bound to aluminum salts remains unavailable to algal populations (WI DNR,
2003). Related studies indicate that the bound phosphorus does not disassociate even under anoxic
conditions and may actually remove phosphorus from the water column and immobilize it in bottom
sediments (Welch and Cooke, 2009).
Based on our understanding of Holly Springs' wastewater process, the stoichiometry of the organic
matter in the process, and the effectiveness of the alum treatment, we conclude that the
assumption of PO4-P being 55 percent of the total phosphorus fraction is appropriate. The
remaining evaluations described in this memo continue to use this assumption.
Comment 2:
Please provide an evaluation of the proposed discharge including the impacts from future landuse
changes.
Response 2:
The initial modeling efforts performed in 2008 for the Western Wake Regional Water Reclamation
Facility included an evaluation of future landuse under future conditions. For this assessment, all the
land in the drainage was assumed to be built -out to the uses identified in the Wake, Chatham, Lee,
and Harnett future landuse plans. It was also assumed that stormwater ordinances including
stormwater Best Management Practices (BMPs) would be in place. The initial evaluations indicated
that little change would be seen in future nutrient loadings when compared to existing loadings.
2

RESPONSES TO DWQ MODELING AND TMDL UNIT COMMENTS
This result is primarily due to the fact that much of the watershed is owned by Progress Energy and
will remain forested. Of the remaining land, approximately 20 percent is expected to have a
different use in the future. Sixty percent of this land is shifting from agricultural or barren land, with
relatively high nutrient loading rates, to low density or very low density residential which have low
nutrient loading rates. The remaining areas are shifting to higher density residential or commercial
lands with BMPs. The stormwater ordinances will mitigate much of the increase in nutrients from
these urbanizing areas. A comparison of the 6 mgd scenario using existing landuse and future
landuse is provided in Figure 1-7 of Attachment 1.
The model inputs for the Holly Springs evaluations were revised to include the potential change in
nutrient loading which would occur under the future build -out scenario. Figures 1-8 through 1-10 of
Attachment 1 show the comparison of chlorophyll a frequency curves for each of the three
segments used to represent the White Oak arm of Harris Lake in the CE-QUAL-W2. Timeseries plots
for these three segments are provided in Attachment 1 as Figures 1-11 through 1-13. As seen in the
analyses presented on January 8`I' 2010, both Phase I (6mgd) and Phase II (8mgd) discharges to the
White Oak Creek Arm of Harris Lake with TP levels of 0.5 mg/L are not expected to increase
chlorophyll a concentrations above the standard of 40 ug/L. In addition, the trigger of 25 ug/L
chlorophyll a was not exceeded more than 10 percent of the time under either Phase I or Phase II
flows.
Comment 3:
Please provide documentation showing a comparison of the levels below which the lake is anoxic
under the baseline and discharge scenarios.
Response 3:
Attachment 1 provides the required documentation. A time -depth plot of dissolved oxygen (DO) was
first generated to determine when the anoxic zone was the largest. Figure 1-14 shows this
timeseries. The years 2006 and 2008 both showed periods with a large anoxic zone. Two dates,
which showed a deep anoxic zone, were selected by further evaluating the depth of the anoxic zone
for 2006 and 2008. The more detailed time -depth plots and a comparison of DO at the three
segments of the White Oak arm of Harris Lake are provided in Figures 1-15 through 1-18. A very
small change in the depth at which goes anoxic is seen between the existing and discharge
scenarios. The difference is actually exaggerated to some extent since the Phase II scenario has a
slightly higher average lake level due to the continuous discharge. If the surface elevations were
equal, the differences in the location of the anoxic zone would be even smaller. This indicates that
the proposed discharge would have little effect on the depth at which the lake arm goes avoxic
during the summer.
3

MEMORANDUM
To: File (CS370908-01, CS370722-02)
From: Jennifer Haynie
Construction Grants and Loans Section
Facilities Evaluation Unit
Date: January 11, 2010
Subject: Summary of Meeting between DWQ and Holly Springs on January 6, 2010
The purpose of this memorandum is to summarize the meeting which took place on Wednesday,
January 6, 2010 at the Holly Springs Town Hall.
Meeting Attendees
• Klaus Albertin, CH2MHi11
• Pam Behm, Division of Water Quality, Modeling and TMDL Unit
• Alan Clark, Division of Water Quality, Planning Section
• Kim Colson, Division of Water Quality, Construction Grants and Loans Section
• Carl Dean, Town of Holly Springs
• Jennifer Haynie, Division of Water Quality, Construction Grants and Loans Section
• Bill Kreutzberger, CH2MHill
• Matt Matthews, Division of Water Quality, Surface Water Protection Section
• Jenny Mizelle, Town of Holly Springs
• Amy Moore, Town of Holly Springs
• Ed Powell, Davis -Martin -Powell
• Jeff Poupart, Division of Water Quality, Point Source Branch
• John Schifaro, Town of Holly Springs
• Chuck Simmons, Town of Holly Springs
• Danny Smith, Division of Water Quality, Raleigh Regional Office
• Kathy Stecker, Division of Water Quality, Modeling and TMDL Unit
• Stephanie Sudano, Town of Holly Springs
• Gil Vinzani, Division of Water Quality, NPDES East Unit
Meeting Summary
Presentation on Speculative Limits Request
Klaus Albertin made a presentation entitled "Town of Holly Springs Speculative Limits Request
to Discharge to Harris Lake." The following provides a summary of the discussion after the
presentation.
C:1Da:uments and Senings\gil_vinzani Local Settings\Temporary Internet Files\Conteat.Oudook\IFBI3\VEI3S110 01 08 !lolly Springs Meeting Sununary.doc
1

Matt Matthews asked how the removal of the discharge from Utley Creek would impact waters
in the creek and in the White Oak arm of Harris Lake. Klaus replied that the flow in Utley Creek
would decrease due to the removal of the discharge. However, the water in the White Oak arm
of Harris Lake would increase due to an increase in the permit discharge limits [6.0 MGD to 8.0
MOD].
Pam inquired about the average depth of the water in the White Oak arm of Harris Lake. Klaus
replied that it was pretty shallow, less than 20 feet. She also asked about whether future land use
within the watershed of Harris Lake was taken into consideration. Klaus stated that it was not
factored into the last graph (duration curve for chlorophyll -a) but that land use was taken into
consideration for the analysis done for the Western Wake Partners.
Danny asked whether placing the discharge point near the intake to the Progress Energy facility
had been considered. Bill replied that Progress Energy did not want their intake location close to
the location of their intake.
Presentation on Supplemental Monitoring
Bill Kreutzberger made a presentation entitled "Supplemental Monitoring — Preliminary
Results." While the presentation did not generate any discussion specifically related to this
topic, Stephanie presented an additional graph that shows the trend of phosphorus levels from the
first part of August through the first part of December. Note that portions of the expanded plant
are coming online during this time period.
Other Discussion and Questions
Matt asked what the Town considered to be the general timeline for this project. Stephanie
stated that the Western Wake EIS process is nearing its end, which will clear the way to submit
permit applications. The Town needs to move forward with this process because it has money
tied up some with the Western Wake Regional Water Reclamation Facility (WWRWRF) itself
and in the effluent force main. The Town's goal is to by the middle of the summer begin work
on an Engineering Report/Environmental Information Document (ER/EID) for submittal.
Additionally, with each passing day, the Town is spending money in the Western Wake
Partnership.
Someone asked about the reasons that are pushing the Town away from the Western Wake
Partnership. Stephanie replied that currently, the Town has approximately $35 million invested
in the Western Wake Partnership, which includes the effluent line to the WWRWRF.
Additionally, the Town has a reclaimed water system and hopes to utilize the system to offset the
amount of potable water used for nonpotable uses.
Danny suggested that the macrophyte issue may be an issue that needs to address. Hydrilla and
water primrose can be a problem, and is influenced by depth, clarity, and water temperature.
These factors influence their growth more than nutrients or other wastewater constituents, and
the Town will need to keep this potential issue in mind.
C:\Documents and Seuings\gil_vinznni\Lcal Settings\ Temporary Internet Files1Content.OuikmkJF13BWEBS\lO01 OS Holly Springs Meeting Sunnuary.doc
2

Stephanie stated that it would be helpful for DWQ to supply a rough timeline. Pam responded
that it generally takes a minimum of 30 days for the TMDL and Modeling Unit to review the
data and model and comment on it. Once the NPDES East Unit receives the needed information
from the Modeling and TMDL Unit, it is a relatively simple process to send the speculative
limits letter. Most of the time will be taken up with data and model review as well as back and
forth between the Modeling and TMDL Unit and CH2MHill.
Action Items
• CH2MHill will incorporate future land use into their modeling analysis.
• DWQ Modeling and TMDL Unit will review the model, files, and memorandum associated
with the speculative limits request and will send comments to CH2MHi11.
Attachments
Cc: Kim Colson, Division of Water Quality, Construction Grants and Loans Section
Daniel Blaisdell, Division of Water Quality, Construction Grants and Loans Section
Alan Clark, Division of Water Quality, Planning Section
Matt Matthews, Division of Water Quality, Surface Water Protection Section
Jeff Poupart, Division of Water Quality, Surface Water Protection Section, Point Source
Branch
Kathy Stecker, Division of Water Quality, Planning Section, Modeling and TMDL Unit
Pam Behm, Division of Water Quality, Planning Section, Modeling and TMDL Unit
Gil Vinzani, Division of Water Quality, Surface Water Protection Section, NPDES East
Unit
Danny Smith, Division of Water Quality, Raleigh Regional Office
Melba McGee, NC Department of Environment and Natural Resources, Office of
Legislative and Intergovernmental Affairs
Henry Wicker, U.S. Army Corps of Engineers
C:\Documems anti Seuings\gil vinzani\Local Senings\Tcuy>orary Internet Files 10111 08 Iloll c Spring, Minting Summary.doc
3

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THE TOWN OF
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Springs
CAROLINA
TOWN OF HOLLY SPRINGS
ENGINEERING DEPARTMENT
PO Box 8 Holly Springs, NC 27540
[phone] • FAX [phone]
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Town of Holly Springs Speculative Limits Request to
Discharge to Harris Lake
January 6, 2oeir a i °
Council Chambers - Holly Springs Town Hall*
AGENDA
• Introductions
• Background on Town WWTP expansion and discharge
• Development of Harris Lake Model
• Application of Model to Holly Springs Discharge Evaluation
• Modeling results for Holly Springs Discharge Scenarios
• Proposed limits for Harris Lake Discharge
• Speculative limits discussion
• Supplemental monitoring program — preliminary results
• Summary and Path forward
NC-5S EX c�' 4-rt"-V
eewio-t .c . fit` S5
*128 South Main Street - Holly Springs, NC

1/6/2010
iYD"V'
Supplemental Monitoring —
Preliminary Results
town orlion, Spring:. 6J:muart. _i o
Supplemental Monitoring
egan in July 2009 `1
❑ ampling at five locations from above WWTP
to White Oak Creek arm of Harris Lake
❑ Monthly nutrient and chl a observations
o Twice monthly field parameter observation in
summer (once monthly in winter)
o Used contractor for UCFRBA and MCFRBA
monitoring coalitions
1

1/6/2010
Observations from Preliminary Results
❑ Moderate reduction in nutrients in Utley
Creek
o Similar chl a levels in Thomas Mill Pond and
White Oak Creek arm of lake
o Inlake TP concentrations below o.4 mg/L
result in chl a levels near 25 ug/L
o Elevated chl a levels seen when TP levels were
high
o Recent TP and chl a observations are much
higher than historical data seen at station S2
n Due to WW1? system transition �"-
-7
2009 Total Nitrogen Monitoring Results
2009 Total Phosphorus Monitoring Results
7
s•
a•
0
UTGI t1TC4 urGS u1C-7 UIGID
station
¢ i
2

1/6/2010
2009 Chlorophyll a Monitoring Results
100
90
80 -
70
60
W-
40 -
3o
20 -
10 -
0
U7C-5 (TMP)
IAJ
UTC-10
(Hartle)
Stations
Comparison of Recent and Historical
MonitoringWhite Oak Creek Arm
C
OS
05
04
; 03
01
NO, 206 M
2507
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SO
53
3
40
10
0
1071. AM SOC.
Nutrient levels increased in WWTP
Effluent in Mid-2009
17:.=•—••:"
•
- -1-4/
3

Town of Holly Springs Speculative
Limits Request to Discharge to Harris
Lake
January 6, 2010
Agenda
• Background on Holly Springs WWTP
Discharge
• Development of Harris Lake Model
• Application of Model to Holly Springs
Discharge Evaluation
• Modeling results
• Proposed limits
• Speculative Limits Discussion
• Supplemental monitoring program
• Summary and path forward
Development of Harris Lake Model
• Utilized the USACE CE-QUAL-W2 modeling
framework
• Performed initial calibration followed by
detailed monitoring in 2008
• Refined calibration in 2009
• Presented to NC DWQ and addressed
comments
• Received approval notification of calibration
(eoe ( 2t>` s
1

Station S2: Apr - July 2008 DO Comparison
Application of Model to Holly Springs
Lake Discharge Evaluation
o Began with model calibrated for 2008
o Added discharge to White Oak Creek arm of
Harris Lake above New Hill Holleman Rd
(Segment 18)
o Created two scenarios; Phase I (6 mgd) and
Phase II (8 mgd)
o Specified discharge characteristics as 5 mg/L
TN;0.5 mg/L TP, 5 mg/L BOD, and 1 mg/L
Application of Model to Holly Springs
Lake Discharge Evaluation (cont.)
A Evaluated chlorophyll a response in White
Oak Creek arm, the main body of the lake, and
above the Main Dam
o Compared the baseline with the Phase I and
Phase II results
�• Chlorophyll a levels remain below 40 ug/L for p
all scenarios _— -
♦ Largest Increase is seen in White Oak Creek
arm
♦mChlorophyll a levels do not exceed 25 ug/L
ore than -3 percent of time at any location
�vLC,Lfi Ii� ?� C1G 0 - S
1-0 TN
3

w
s
40
IS
10
5
o�
0%
ChImplyl a DISIStit41 Cora to NMte Oak Arm Discharge
—Pewit*
^O.s myt TP Dowd—O.5mr1.7Fen050 --s0%—&Y1Aara
—1 —
I
f
—
I
101a
20% 30% 40% 50% 110% 70% 00% 00%
Patera tenon <ra0a
100%
Proposed Limits
0 5 mglL TN
0 0.5 mg/L TP Q Z7
0 5 mg/L BOD i
0 1 mglL NH3-N
0 Predicted to maintain chl a below 25 ug/L at
least 95 percent of time
Speculative Limits Discussion
5

Progress Energy
Ms. Coleen Sullins
Director
NC Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Dear Ms. Sullins:
Christopher L Burton
Vice President
Harris Nuclear Plant
Progress Energy Carolinas, Inc.
December 22, 2009
` DEC 29 2009
1.iG.,
Progress Energy has been informed that the Town of Holly Springs plans to submit a
request for speculative limits from the NC Division of Water Quality (NCDWQ) for a
discharge of treated wastewater directly to Harris Lake. Our understanding is that this
treated wastewater is currently discharged to Utley Creek, a tributary to Harris Lake.
This letter is to inform you that Progress Energy is aware of this pending request and
has no objections to the Town pursuing this request with NCDWQ.
As the entity responsible for the development of Harris Lake and the primary user of
the water resources stored therein, Progress Energy acknowledges and takes seriously,
its role as a primary environmental steward for the lake. If there are questions or
concerns regarding this information or the request from the Town, please contact my
office at [phone].
Sincerely,
CLB:lmr
c: File
P.O. Box 165
New Hill, NC 27562
r > 919.362.2502
F> 919.362.2095

TIIF TOWN Of
Iiolly
Springs
P.O.Box 8
128 S. Main Street
Holly Springs, N.C. 27540
www.hollyspringsnc.us
[phone]
Fax: [phone]
Mayor's Office Fax:
[phone]
December 21, 2009
Mr. David L. (Matt) Matthews
Chief, Surface Water Protection Section
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
RECEIVED
D
DENR - WATER QUALITY
POINT SOURCE BRANCH
Subject: Request for Speculative Limits for Harris Lake
Town of Holly Springs, Wake County
Dear Mr. Matthews:
The Town of Holly Springs is requesting that Division of Water Quality
(DWQ) consider the issuance of speculative permit limits for a discharge to
the White Oak Creek arm of Harris Lake. Attached is a technical
memorandum that evaluates a discharge to the lake. The following
paragraphs provide background and additional information related to this
request.
The Town of Holly Springs has been working for many years with DWQ, our
neighboring communities, and consultants to meet the needs of the Town for
increased wastewater treatment capacity. Currently, we discharge to Utley
Creek, a tributary to the White Oak arm of Harris Lake. The Town has
received a Finding of No Significant Impact (FONSI) from DWQ to expand
our wastewater treatment facilities to a capacity of 6 MGD and has received
speculative permits for a discharge to the Cape Fear River below Buckhorn
Dam for up to 8 MGD [in conjunction with speculative limits for the Western
Wake Water Reclamation Facility (WRF) of an additional 30 MGD]. We have
been working closely with the Towns of Apex, Cary and Morrisville as part of
the Western Wake Partners to complete the Federal Environmental Impact
Statement (EIS) for the proposed wastewater management facilities which
would collect raw wastewater from the other Partners, treat that wastewater
at a site near New Hill, and would jointly convey that effluent and effluent
from the Town of Holly Springs Utley Creek WWTP to the Cape Fear River.
As part of the EIS process, the Partners developed a nutrient response model
in cooperation with Progress Energy and DWQ to evaluate the potential for
discharging effluent into Harris Lake. The process leading to approval of the
model calibration by DWQ included the following steps:
• Initial meetings to discuss model development and other issues (such as
required model development and calibration data, discharge location, etc.)
involving the Partners, Progress Energy and DWQ followed by periodic
meetings to discuss model development progress

Mr. David L. (Matt) Matthews
Page 2
December 21, 2009
• Development of a modeling and monitoring plan with review and input
by DWQ
• Initial model development and calibration report based on data prior to
2007
• Detailed bathymetric survey of Harris Lake in 2008 by Progress Energy
• Intensive water quality monitoring in 2008 by Progress Energy including
summer bi-weekly sampling at six locations
• Revised model calibration report incorporating 2008 monitoring data
• Responses to DWQ comments and requests for additional information
• DWQ approval of the model calibration on May 22nd, 2009
The Final EIS for the Western Wake Wastewater Management Facilities
indicates that a Harris Lake discharge does not meet the purpose and need for
the project because of the additional length of time required to address
interbasin transfer (IBT) requirements for the communities (Towns of Apex,
Cary, and Morrisville and RTP South) that obtain water supply from Jordan
Lake. Therefore, a speculative limits request for the discharge to Harris Lake
from the Western Wake WRF has not been made to DWQ. The Town of Holly
Springs does not have IBT issues associated with a discharge to Harris Lake
and the Final EIS indicates that the Town may pursue a discharge to Harris
Lake and evaluate the impacts through an amendment to their State
EA/ FONSI or to the Federal EIS.
The Town of Holly Springs is interested in options to a Cape Fear River
discharge because the capital cost associated with pumping and conveyance
facilities to get their effluent over to the Western Wake WRF effluent pump
station and the Town's share of the Western Wake facilities totals about $35
million. Pumping and maintenance costs would be in addition to this capital
cost. In addition to the costs, impacts from the pipeline construction to the
Western Wake WRF would be reduced and there would be water resources
benefits to keeping the discharge in the Harris Lake watershed. These benefits
include fewer wetland and stream impacts for a shorter pipeline, less energy
(and thus fewer emissions of green house gases) for effluent pumping, and
greater flexibility for managing Harris Lake under potential future operations
by Progress Energy. For these reasons, the Town of Holly Springs is
considering a discharge to the White Oak Creek arm of Harris Lake above
New Hill - Holleman Road. The Town is currently working with Progress
Energy on a specific location for the discharge point as well as other issues
associated with getting an easement through Progress Energy property.

Mr. David L. (Matt) Matthews
Page 3
December 21, 2009
The attached technical memorandum evaluates a proposed discharge to the
White Oak Creek arm of Harris Lake and indicates that the lake can assimilate
both a 6 MGD and future 8 MGD discharge from the Town consistent with
DWQ's evolving strategy for managing nutrients and eutrophication in North
Carolina. The memorandum indicates that with effluent nutrient criteria
limits of 5 mg/L for Total Nitrogen and 0.5 mg/L for Total Phosphorus,
chlorophyll a levels are projected to exceed 25 ug/ L less than 4 percent of the
time, which is below DWQ's proposed threshold of 10 percent for managing
nutrients, under either a 6 or 8 MGD discharge scenario. Predicted
chlorophyll a levels do not approach the water quality standard under
existing conditions or with discharges at these limits.
We will be contacting you to arrange a meeting to discuss our request. If you
have a need for additional information or other questions prior to this
meeting, please do not hesitate to call me at (919) - 557-3938. We appreciate
your consideration of our request.
Stephanie Sudano, PE
Director of Engineering
c: Coleen Sullins/DWQ
Kathy Stecker/DWQ
Jeff Poupart/DWQ
Bill Kreutzberger/CH2MHill
Mike Slusher/ DMP
Carl Dean/Town of Holly Springs
13282

TECHNICAL MEMORANDUM CH2MHILL
Evaluation of Potential Holly Springs Discharge
Scenarios
PREPARED FOR: Town of Holly Springs
PREPARED BY: CH2M HILL
DATE: December 7, 2009
Purpose and Introduction
The Western Wake Partners (Partners) are proposing a new water reclamation facility
(WRF) in southwestern Wake County and have received speculative limits from the NC
Division of Water Quality (DWQ) for a discharge to the Cape Fear River below Buckhorn
Dam from their WRF and from an expansion of the Town of Holly Springs Utley Creek
WRF. The discharges to the Cape Fear River would be through a shared effluent pipeline.
As an alternative to the Cape Fear River discharge, Harris Lake was evaluated as a potential
receiving water body. The Partners worked with DWQ to determine a technical approach
which could be used to demonstrate that a Harris Lake discharge would be acceptable.
A detailed water quality model was developed for the Partners to evaluate the changes that
might occur in Harris Lake. This model was reviewed and accepted by DWQ. However, the
Partners have subsequently determined that a Harris Lake discharge does not meet the
purpose and need of their project because of the time frame to receive an IBT approval for
the discharge. Since the Town of Holly Springs does not have to contend with an IBT
approval, the Town would like to evaluate the feasibility of discharging to Harris Lake. The
model developed to evaluate the Western Wake WRF was adapted to evaluate the impacts
of a discharge of the effluent from the Holly Springs WRF to the White Oak Creek Arm of
the lake.
Of primary interest are potential increases in algal populations, as measured by chlorophyll
a concentrations as a result of the discharge. This technical memorandum describes the
development and evaluation of a number of potential Holly Springs discharge scenarios.
The scenario evaluation builds on the CE-QUAL-W2 model calibrated using 2006 - 2008
monitoring data and approved by DWQ. The calibrated model was used to compare a
baseline condition with two potential scenarios to evaluate changes in lake water quality.
Results of these scenario runs are summarized in this technical memorandum.
Background Information
The Western Wake Partners, composed of the Towns of Apex, Cary, Morrisville and Holly
Springs, are proposing a new WRF in Southwestern Wake County to serve the Towns of
Apex, Cary, and Morrisville. The Town of Holly Springs would share the effluent line; both
treatment facilities would discharge to the Cape Fear River below Buckhorn Dam. An EIS of
the proposed project is currently under development and being led by the U.S. Army Corps
of Engineers (USACE) under the National Environmental Policy Act (NEPA). This EIS is
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX 1
COPYRIGHT 2009 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
prepared in cooperation with agencies of the NC Department of Environment and Natural
Resources (DENR), especially DWQ and the Western Wake Partners. The Partners had
considered a discharge to Harris Lake to reduce the length of the effluent pipeline and to
provide greater flexibility in managing water resources by storing the effluent in an
impoundment. The shorter pipeline would also result in fewer impacts to wetlands and
streams, reduced pumping costs, and a smaller carbon footprint.
FIGURE 1
Harris Lake Location Map
- &stem Wake WSW Urtique Carponen
mm dal
PJ'10 iYlml
. i4aiunw•nf
lJxlrrvN•t ..
BYOl vrn Dw l
Draft EIS - Febntari 2009
Source: CDM 2009
M��E
�• /HOLLYTh
.... C. SPRINGS
•tY R`�
.•
Poterta Ixxim DI
Icily Sprir>i Utley
Leek t.WTF ckdal
Figure 2-3
Proposed Project with Alternative
Discharges to Iris Lake
C.,y C.o.n I.YPo<. Main
• F..siv u•.1•1C10. kn. ran
Cory Clove, l•••1 D•nly 9••.•
.. [ryl.:l•• Conn CrM• Em.•
• • • Ats•Crl•C.n. M•il
• -•A. B.rJI B•o.f•'.,••ry 9..r
fie.. C•••\ Sur• Sam
• •r E•••.• C ••y r•••
• rr a ..yY. Ci.nys•61ok.
Enrol fun. Ws•
inI C•r-V3•lan
®1lbwalr iu.n�en 1`Lt
O r'•��wWN.I
WEB
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX 2
COPYRIGHT 2009 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
Harris Lake is a manmade reservoir that provides cooling, process, and domestic water for
the Shearon Harris Nuclear Power Plant (SHNP). The construction of two additional reactor
units is being proposed. These units would also utilise Harris Lake for cooling water and
removal of heat load. To provide sufficient long term cooling capacity, the water level of
Harris Lake would be raised from a mean operating level of 220 feet National Geodetic
Vertical Datum of 1988 (NGVD88) to a mean level of 240 feet NGVD88. Water from the
Cape Fear River, in addition to direct drainage from the watershed area, would be required
to fill and maintain the required pool level for normal operations. A WRF discharge to
Harris Lake was considered since it would provide a consistent flow to the reservoir and
would reduce the required withdrawals from the Cape Fear River. This option is not being
pursued for the discharge from the new WRF due to issues related to interbasin transfer
regulations. However, the analysis tools used to evaluate a discharge from the Western
Wake WRF can also be used to predict changes to water quality from the discharge of the
Holly Springs portion of the WRF to Harris Lake.
DWQ required that the changes that could potentially occur to Harris Lake be assessed with
a calibrated nutrient response model before this option could be considered. A combination
of a Generalized Watershed Loading Function (GWLF) model and a CE-QUAL-W2 lake
water quality model was developed to quantify the changes which would occur. The CE-
QUAL-W2 model is a two-dimensional, longitudinal/vertical, hydrodynamic, and water
quality model designed to evaluate water quality in lakes and reservoirs. The model has
been applied to rivers, lakes, reservoirs, estuaries, and combinations thereof (Cole and
Wells, 2002). The model computes water levels, temperature, and numerous other water
quality parameters such as dissolved oxygen, nutrients, organic matter, algae, pH, the
carbonate cycle, bacteria, and dissolved and suspended solids.
The technical memorandum (TM) entitled Development and Calibration of a CE-QUAL-W2
Model for Harris Lake including 2008 Update (CH2M HILL, 2009) describes the development
and calibration of a CE-QUAL-W2 model to calculate changes to Harris Lake water quality
as a result of discharging effluent from the proposed Western Wake Regional Water
Reclamation Facility to Harris Reservoir. The model was originally constructed and applied
to provide initial insight into potential effects of the WRF discharge to Harris Lake.
Subsequent efforts using more detailed monitoring data collected in 2008 at the locations
shown in Figure 2 refined and validated the model.
The 2008 validation efforts strongly support the conclusion that the draft CE-QUAL-W2
model of Harris Lake accurately represents the physical and chemical behavior of the lake.
The results of the 2008 model validation update and supplemental information were
provided to DWQ for review. The model calibration was approved by DWQ on May 22nd,
2009 (personal communication, 2009).
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX 3
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
FIGURE 2
2008 Harris Reservoir Sampling Locations
b
:12)-:- '''', \
:`- hj 1
r .ter L
'-
b 1P ca
�, o.-
S2
'0-I
-
0
cA
,
iL.� r.tf
pHFHAM
�f
NETT
,„4_,Legend
Hams Lake Modeling Segments
A
0 0.25 0.5 1 1.5 2
Miles
Harris Reservoir
2008 Sampling Locations
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX 4
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
Scenario Evaluation
Since our analysis indicates that Harris Lake is not currently impaired, the scenario
development was guided by the nutrient management proposals currently being evaluated
by DWQ for prevention of nutrient impairment. Based on a September 10, 2009 presentation
to the EMC, DWQ is proposing a threshold criterion for piedmont reservoirs of no more
than 10 percent of values exceeding a chlorophyll a level of 25 ug/L. If this level is exceeded,
DWQ is proposing a number of management possibilities, including no new discharges
directly to reservoirs or nutrient limits for new and expanding discharges of TN levels of 5
mg/L and TP levels of 0.5 mg/L.
The calibrated model was modified to evaluate two potential scenarios to identify changes
in chlorophyll levels resulting from nutrient loading and potential algal production. These
scenarios were intended to simulate the potential range of discharge rates and
characteristics that are under consideration for the current managed lake level.
Baseline Scenario
The baseline for the scenario evaluation is the calibrated model for the period from 2006 -
2008. This period was specified by DWQ in their comments on the initial Western Wake
WRF scenario evaluations. This period includes both an extreme drought year (2007) as well
as relatively wet years (2006, 2008). This allows for the evaluation of the scenarios under
conditions where inflows to the lake are limited and also when nonpoint source loadings are
high. The lake level is maintained at a 220' level. All inputs and model parameter values are
the same between the baseline and each scenario with the exception of the changes
described below.
White Oak Creek Discharge Scenarios
The Holly Springs WRF is expected to be constructed in two phases. Phase I with a
discharge rate of 6 mgd is expected to meet wastewater capacity requirements through the
year 2020. Phase II, with a discharge rate of 8 mgd is expected to meet wastewater capacity
requirements through the year 2030.
The two potential scenarios of interest are described as follows:
1) Phase I_0.5 - A Holly Springs WWTP discharge of 6 mgd. Discharge characteristics
for the discharge would be 0.5 mg/L total phosphorus, 1 mg/L ammonia, total
nitrogen of 5 mg/ L, and biochemical oxygen demand of 5 mg/ L. The discharge
would be directly to the White Oak Creek Arm of Harris Lake.
2) Phase II_0.5 - A Holly Springs WWTP discharge of 8 mgd. Discharge characteristics
for the discharge would be 0.5 mg/L total phosphorus, 1 mg/L ammonia, total
nitrogen of 5 mg/L, and biochemical oxygen demand of 5 mg/L. The discharge
would be directly to the White Oak Creek Arm of Harris Lake.
Results
The baseline condition and two scenarios were run to evaluate changes in water quality for
the period from 2006 through 2008. As in earlier comparisons, changes in chlorophyll a were
the primary parameter of interest since it is an indicator of algal biomass and there is a
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
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5

EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
water quality standard for chlorophyll a. The current State water quality standard is 40
ug/L. An additional, lower value of 25 ug/1 has been proposed as a potential "trigger" to
identify waterbodies which are beginning to have eutrophication issues, where nutrient
management within the watershed should be warranted.
Comparison of Phase 9 Scenarios
The simulation was run for the period from 2001 through 2008 and results for the analysis
period of 2006 through 2008 were extracted. Plates 1 through 3 provide a comparison of
chlorophyll a at three locations of interest. It can be seen that chlorophyll a concentrations
are estimated to remain below 40 ug/L for all scenarios. Earlier analyses suggest that the
lake tends to be phosphorus limited. For this reason, any increase in phosphorus Loadings
increases algal growth. However, a 0.50 mg/L TP discharge is predicted to have a small
impact with a maximum increase in chlorophyll a of less than 7 ug/L. The highest
chlorophyll a levels are seen in the White Oak Creek Arm segment with a maximum value
of approximately 32 ug/L.
Chlorophyll a responses were also evaluated using a frequency duration curve (See Plates 4
- 6). These curves are developed by determining the percent of predictions that fall below a
given value and plotting them on a continuum. For example, in Plate 4, approximately 97
percent of calculated concentrations in the White Oak Creek Arm. segment fall below 25
ug/L for an 8 mgd discharge. It can be seen that neither discharge level results in the
potential "trigger" level being exceeded more than ten percent of the time at any of the
evaluation locations.
Conclusions
The comparisons of the proposed scenarios to the baseline condition indicate that a
discharge to the White Oak Creek Arm of Harris Lake with TP levels of 0.5 mg/L are not
expected to increase chlorophyll a concentrations above the standard of 40 ug/L. In
addition, the trigger of 25 ug/L chlorophyll a was not exceeded more than 10 percent of the
time under either Phase I or Phase II flows.
References
Behm, Pamela/North Carolina Division of Water Quality. 2009. Personal communication
with Klaus Albertin/CH2M HILL, May 22.
CDM/CH2M HILL. 2009. Draft Environmental Impact Statement - Western Wake Regional
Wastewater Management Facilities. Prepared for the U.S. Army Corps of Engineers.
CH2M HILL. 2009. Development and Calibration of a CE-QUAL-W2 Model for Harris Lake
including 2008 Update.
Cole and Wells. 2002. CE-QUAL-W2: A Two -Dimensional, Laterally Averaged,
Hydrodynamic and Water Quality Model, Version 3.2. U. S. Army Corps of Engineers.
Washington, DC.
Sullins, Colleen/North Carolina NC Department of Environment and Natural Resources.
2009. Personal communication with -Bill Kreutzberger on September 10, 2009.
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX 6
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50
45
40
35
J
C)
co 25
20
30
15
10
5
Chlorophyll a Comparison for White Oak Arm Discharge
—Baseline
6mgd —8mgd Standard
0
1/1/2006
1,1
7/1/2006 1 /1 /2007 7/1/2007 1/1/2008 7/1/2008
PLATE 1
Comparison of chlorophyll a Concentrations in White Oak Arm (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
7
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
50
45
40
35
a)
a
25
30
20
15
10
5
Chlorophyll a Comparison in Main Lake near Station M2
—Baseline
----6mgd —8mgd —Standard
r
AAk
V Ilk
0
1/1/2006
7/1/2006 1 /1 /2007 7/1/2007 1/1/2008 7/1/2008
PLATE 2
Comparison of chlorophyll a Concentrations in Main Lake near Station M2 (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009,DOCX
8
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
50
45
40
35
r..
30
ea 25
▪ 20
15
10
5
Chlorophyll a Comparison for Dam Segment
—Baseline
— --6mgd —8mgd Standard
0
1/1/2006
11171 TIP
L
7/1/2006 1 /1 /2007 7/1/2007 1/1/2008 7/1/2008
PLATE 3
Comparison of chlorophyll a Concentrations in Main Dam Segment (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
9
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
J
s
0
50
45
40
35
30
25
20
15
10
5
0
Chlorophyll a Duration Curve for White Oak Arm Discharge
® Baseline
0.5 mg/LTP 6mgd —0.5 mg/LTP 8mgd 90% --Standard
J
0%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Time < Value
PLATE 4
Chlorophyll a Concentration Duration Plot in White Oak Arm (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
10
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
50
45
40
35
J
30
ca 25
s
c.)
20
15
10
5
0
Chlorophyll a Duration Curve in Main Lake near Station M2
— Baseline 0.5 mg/LTP, 6mgd —0.5 mg/LTP, 8mgd 90% Standard
0%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Time < Value
PLATE 5
Chlorophyll a Concentration Duration Plot in Main Lake near Station M2 (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
11
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EVALUATION OF POTENTIAL HOLLY SPRINGS DISCHARGE SCENARIOS
50
45
40
35
30
25
20
15
10
5
Chlorophyll a Duration Curve for Main Dam Segment
Baseline 0.5 mg/LTP 6mgd ®0.5 mg/LTP 8mgd 90% —Standard
i
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Time < Value
PLATE 6
Chlorophyll a Concentration Duration Plot in Main Dam Segment (2006 — 2008)
HOLLY SPRINGS SCENARIOS TM FOR DWQ 12072009.DOCX
12
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