NC0041696_Speculative Limits_19980724

NPDES DOCUMENT !;CANNING COVER SHEET
NPDES Permit:
NC0041696
Lake Rhodhiss WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Report
Instream Assessment (67b)
t
.°
Speculative Limits
Environmental Assessment (EA)
Document Date:
July 24, 1998
This document is printed on reuse paper - ignore any
content on the resrerse side

•
JAMES B. HUNTJR.ir;.
'GOVERNOR ACC
WAYNE MCDENITT
SBCRETARY.
- A. PRESTON HOWARD,
R.; RE.
4" 1RECTOR
ni:
•
•
•
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WATER QUALITY.
Mr. Jeffrey V. Morse, Town Manager
Town of Valdese
P.O. Box 339
Valdese, North Carolina 28690-0339
Subject:
July 24, 1998
Speculative Limits for the Town of Valdese WWTP
NPDES Permit No. NC0041696
Burke County
Dear Mr. Morse:
Based on your request, the staff of the NPDES Unit of the Point Source
Branch has reviewed the previously recommended speculative limits for the
subject facility. In a letter dated May 13, 1991, the Division had supplied the
Town with speculative limits for expansion flows of 9.5 MGD and 11.5 MGD.
At that time, effluent limits for the oxygen -consuming parameters, BOD5 and
NH3 were given based on DWQ's Best Professional Judgement (BPJ) and lake
studies in the Catawba River Basin.
The application of BPJ limits of BOD5 =15 mg/I, NH3 = 4 mg/I, and DO
> 5 mg/1 to all new and expanding dischargers to the Catawba chain lakes remains
a DWQ management strategy to help reduce the impact of point sources
discharging directly into these major waterbodies. The speculative limits
previously recommended for BOD5, NH4 and DO are still applicable at this time.
However, DWQ staff is reviewing the results of a recently completed water
quality model on Rhodhiss Lake, which will be incorporated into the second
Catawba River Basin Management Plan. Preliminary reviews indicate that there
may need to be some revisions of the nitrogenous inputs (i.e. NH3) of direct
dischargers into the lake. If final reviews indicate that an NH3 limit more
stringent that 4 mg/1 should be given, the Town will be notified immediately of
this modification.
Please be advised that response to this request does not guarantee that the
Division will issue an NPDES permit to discharge treated wastewater into these
receiving waters. It should be noted that new and expanding facilities, involving
P.O. BOX 29535, RALEIGH, NORTH CAROLINA 27626-0535
PHONE [phone] FAX [phone]
AN EQUAL OPPORTUNITY /AFFIRMATIVE ACTION EMPLOYER - 50% RECYCLED/10% POST -CONSUMER PAPER

Letter to Jeffrey V. Morse
Page 2
an expenditure of public funds or use of public (state) lands, will be required to prepare
an environmental assessment (EA) when wasteflows: 1) exceed or equal
0.5 MGD, or 2) exceed one-third of the 7Q10 flow of the receiving stream. DWQ will
not accept a permit application for a project requiring an EA until the document has been
approved by the Department of Environment and Natural Resources and a Finding of No
Significant Impact (FONSI) has been sent to the state Clearinghouse for review and
comment.
The EA should contain a clear justification for the proposed facility and an
analysis of potential alternatives that should include a thorough evaluation of non -
discharge alternatives. Nondischarge alternatives or alternatives to expansion,
such as spray irrigation, water conservation inflow and infiltration reduction or
connection to a regional treatment and disposal system, are considered to be
environmentally preferable to a surface water discharge. In accordance with the North
Carolina General Statutes, the practicable waste treatment and disposal alternative with
the least adverse impact on the environment is required to be implemented. 'If the EA
demonstrates that the project may result in a significant adverse affect on the quality of
the environment, an Environmental Impact Statement would be required. The Division
of Water Quality's Planning Branch can provide further information regarding the
requirements of the N.C. Environmental Policy Act.
The United States Geological Survey (USGS) has recently published the results of
a study of Rhodhiss Lake. This report included an analysis of ambient water quality
conditions and estimates of nutrient loading and suspended solids. Results indicated that
although the majority of suspended solids, nitrogen and phosphorus entering the reservoir
were from nonpoint sources, a "significant " amount of the nitrogen and phosphorus was
contributed by point sources. With existing stages of eutrophication in Rhodhiss Lake,
DWQ recommends that expanding wastewater treatment plants be designed so that they
can be easily upgraded for nutrient removal. This would be a proactive measure in the
event that nutrient limits are necessary in the future.
A quarterly whole effluent chronic toxicity test for the 9.5 MGD and 11.5 MGD
expansions of 6% and 7%, respectively, would still be assigned. A complete evaluation
of limits and monitoring requirements for metals and other toxicants will be addressed at
the time of formal NPDES application.

Letter to Jeffrey V. Morse
Page 3
We hope this information provides some assistance in your planning endeavors.
As previously mentioned final NPDES effluent limitations will be determined after a
formal permit application and modification request has been submitted to the Division. If
there are any additional questions concerning this matter, please feel free to contact
Jackie Nowell at [phone] (ext. 512).
Sincerely,
David A. Goodric
NPDES Unit Supervisor
Water Quality Section
DAG/JMN
cc: Larry Coble, WSRO
Bobby Blowe, Construction Grants
Local Government Assistance Unit
Central Files
NPDES Permit File

MEMO F orn:
To.
Division of Water Quality
Date: 7�Z z/ F8
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North Carolina Department of Environment and Natural Resources
PO Box 29535, Raleigh, North Carolina 27626-0535 / Phone: [phone]

July 21, 1998
Mr. Jeffrey V. Morse, Town Manager
Town of Valdese
P.O. Box 339
Valdese, North Carolina 28690-0339
Subject: Speculative Limits for the Town of Valdese WWTP
Dear Mr. Morse:
Based on your request, the staff of the NPDES Unit of the Point Source
Branch has reviewed the previously recommended speculative limits for the
subject facility. In a letter dated May 13, 1991, the Division had supplied the
Town with speculative limits for expansion flows of 9.5 MGD and 11.5 MGD.
At that time, effluent limits for the oxygen -consuming parameters, BOD5 and '
NH3 were given based on DWQ's Best Professional Judgement (BPJ) and lake tier
• the Cat River Basin. The application of BPJ limits of BOD5 =15,
NH3 = 4, and D 5 o all new and expanding dischargers to the Catawba chain
lakes r management strategy to help reduce the impact of point
sources discharging directly into these major waterbodies. The speculative limits
recommended for BOD5, NH3 and DO are still applicable.
The United States Geological Survey (USGS) has recently published the
results of a study of Rhodhiss Lake. This report included an analysis of ambient
water quality conditions and estimates of nutrient loading and suspended solids.
With existing stages of eutrophication and documented water quality problems in
Rhodhiss Lake, and other tributary arms above lakes, DWQ &oes not recommend
r�S l continuing with the minimum level of wastewater treatment for direct discharges
t Innaat dition, nu ri rrr1 ding can cause w�lrty problems in lakes.
(\ V 7 For)(expanding wastewater treatment plants, it is recommended that the
treatment plants be designed so that they can be easily upgraded for nutrient
removal. This would be a proactive measure in the event that nutrient limits are
necessary in the future.
A quarterly whole effluent chronic toxicity test for the 9.5 MGD and 11.5 MGD
expansions of 6% and 7%, respectively, would still be assigned. A complete
*ota etc-A,,l-6 a:f -Kns

Letter to Jeffrey V. Morse
Page 2
evaluation of limits and monitoring requirements for metals and other toxicants
will be addressed at the time of formal NPDES application.
We hope this information provides some assistance in your planning
endeavors. As previously mentioned, final NPDES effluent limitations will be
determined after a formal permit application and modification request has been
submitted to the Division. If there are any additional questions concerning this
matter, please feel free to contact Jackie Nowell at [phone] (ext. 512).
Sincerely,
David A. Goodrich
NPDES Unit Supervisor
Water Quality Section
DAG/JMN
cc: Larry Coble, WSRO
Bobby Blowe, Construction Grants
Local Government Assistance Unit
Central Files
NPDES Permit File

Chapter 6 - Basinwide Goals, Water Quality Concerns and Recommended Management Strategies
General Recommended Strategies for
Expanding and Proposed Dischargers in the Catawba Basin
The transitional environment between free flowing streams and lakes is a potentially sensitive area
to loading of oxygen demanding wastes. As stream waters slow and deepen as they enter a lake,
the rate at which oxygen enters the water is reduced. This means that a concentration of oxygen
demanding waste that was acceptable in a free flowing stream may result in dissolved oxygen
levels below the State standard.
The seven major reservoirs that make up the chain of lakes along the Catawba River create many
transition zones between streams and lakes. The hundreds of tributaries to the seven major
reservoirs create local environments where waters may be relatively sensitive to oxygen demanding
wastes. Due to the transitional nature of such waters, the exact allowable amount of oxygen
demanding wastes that can be discharged without impairing water quality is difficult to determine.
Water quality studies can be conducted on a case -by -case basis to support wasteload allocations.
However, due to the widespread occurrence of transitional waters in the Catawba Basin and the
high demand on water for the assimilation of oxygen -consuming wastes, a basinwide strategy is
recommended. Over the past five years, DEM has implemented a minimum treatment strategy for
discharges of oxygen demanding waste in the Lake Norman watershed. It is recommended that
this strategy, described below, be extended to all seven major lakes in the Catawba Basin.
All new and expanding dischargers of oxygen -consuming wastes that discharge to the Catawba
River Chain of Lakes or are predicted to increase oxygen -demanding waste loading to the lakes,
(Lake James, Rhodhiss Lake, Lake Hickory, Lookout Shoals Lake, Lake Norman, Mountain
Island Lake, and Lake Wylie) will be required to meet a minimum of advanced treatment limits.
Typical NPDES permit conditions for advanced treatment facilities are 15 mg/1 BOD5 and 4 mg/1
NH3-N. These limits will help to protect water quality standards in the Catawba River chain of
lakes and will allow for continued growth in the region.
6.3.1 Catawba River Mainstem Watersheds (Subbasins 03-08-30 to 03-08-33)
Subbasin 03-08-30 (Catawba River Headwaters, Lake Tames)
Corpening Creek
Corpening Creek has been listed as an impaired stream due to non -point source pollution from
agricultural and urban runoff from the City of Marion. In addition, Corpening Creek receives
treated wastewater from the 3.0 MGD Marion WWTP via Youngs Fork Creek. Benthic
macroinvertebrate studies conducted above and below the Marion WWTP indicate only Fair water
quality above the discharge and Fair (1985) or Poor (1990) water quality below the discharge.
This suggests that the Marion WWTP was affecting the invertebrate community but that upstream
non -point pollution sources play a significant role in the stream impairment.
Over the past three years, the Marion WWTP has averaged less than 5 mg/1 BOD5 and less that 1
mg/1 NH3-N. These concentrations of oxygen -consuming wastes are well below the facilities
secondary treatment based limits. Therefore it is recommended that efforts to address water quality
issues in the Corpening Creek watershed be concentrated upon non -point source pollution
reduction. Section 6.8 contains several recommendations that the City of Marion should consider
in order to begin addressing urban stormwater pollution. Additional information and guidance can
be provided by DEM's Water Quality Section.
Lake James
At present Lake James is fully supporting its designated uses and there is no indication that the lake
is adversely impacted by the discharge of oxygen -consuming wastes. However, there is
6-6

Chapter 6 - Basinwide Goals, Water Quality Concerns and Recommended Management Strategies
Catawba Creek
All existing surface water discharges in these watersheds with a ermitted desin flow of
greater than or equal to 0.05 MGD should be required to apply state -of -art nutrient removal
technology. Existing facilities have been notified of this strategy and will be required to meet
permit limits of 0.5 mg/1 TP and TN limits of 4 mg/1 in the summer and 8 mg/1 in the winter by
2006. Interim limits of 1.0 mg/1 TP and 6.0 mg/1 TN (summer) will become effective January
1, 2001. Based on a comparison between Figure 3.4, in Chapter 3, and Figure 6.1, it can be
seen that these recommendations would result in reducing the predicted chlorophyll a
concentration in Catawba creek from 74 ug/1 (Figure 3.4) to 35 ug/1 (Figure 6.1).
Crowders Creek
By January 1, 2000, it is recommended that all facilities with a permitted design flow of greater
than or equal to 1 MGD will be required to meet limits of 1.0 mg/1 TP and 6.0 mg/1 TN. The
nitrogen limits would apply for the months of April through October only. Based on a
comparison between Figure 3.4, in Chapter 3, and Figure 6.1, it can be seen that these
recommendations would result in reducing the predicted chlorophyll a concentration in the
creek from 43 ug/1 to 33 ug/1.
Non point sources
All tributaries to Lake Wylie should be targeted by the NC Division of Soil and Water
Conservation for cost share funds for use in implementation of best management practices
(BMPs). When possible, resources should be targeted toward implementation of BMPs in the
Catawba Creek, Crowders Creek, and the South Fork Catawba River watersheds since a
significant amount of the nutrients reaching these streams is from non -point sources. Since the
South Fork Catawba River provides by far the largest nutrient load of any tributary to Lake
Wylie, the South Fork should be considered the highest priority for implementation of BMPs.
6.4.2 Mountain Island Lake
DEM and Mecklenburg County are completing a two-year cooperative study of nutrient loading in
the McDowell Creek watershed and the eutrophic response in Mountain Island Lake. Preliminary
data suggest that the CMUD McDowell Creek WWTP discharge is the largest source of nutrients to
the McDowell Creek arm of Mountain Island Lake. This facility will be required to implement
nutrient removal upon major modification or expansion.
6.4.3 Rhodhiss Lake and Lake Hickory
The WPCOG and the USGS in conjunction with DEM are presently
quality study of Rhodhiss Lake and Lake Hickory. The objctives othis�studyinclude an effort to
quantify nutrient loading to the lakes and to evaluate eutrophic response to nutrient enrichment.
Both lakes receive significant nutrient loading from point and non -point sources.
When compared to other major lakes in the Catawba river basin, Rhodhiss Lake and Lake Hickory
have relatively fast velocities and short retention times (see Table 2.1 in Chapter 2). This suggests
that these lakes may be less sensitive to nutrient enrichment than other lakes in the Catawba river
basin, as mixing and limited retention time in the reservoirs may limit algal growth. Specific
management plans for point and/or non -point source pollution sources to Rhodhiss Lake and Lake
Hickory will be developed after completion of the WPCOG, USGS, DEM study and incorporated
into the second edition of the Catawba basinwide plan.
6- 16

-z/iFP-W/
Rhodhiss Lake, North Carolina: Analysis of Ambient
Conditions and Simulation of Hydrodynamics,
Constituent Transport, and Water -Quality
Characteristics, 1993-94
By Mary J. Giorgino and Jerad D. Bales
U.S. GEOLOGICAL SURVEY
Water -Resources Investigations Report 97-4131
Prepared in cooperation with the
WESTERN PIEDMONT COUNCIL OF GOVERNMENTS
Raleigh, North Carolina
1997

CONCLUSIONS
From January 1993 through March 1994,
ambient water -quality conditions in Rhodhiss Lake
varied spatially and seasonally. Distributions of
temperature revealed dynamic patterns of water
circulation and material transport in the reservoir.
Generally, the shallow upstream end of Rhodhiss Lake
was unstratified and well oxygenated. This riverine
zone was characterized by high turbidity and total
suspended solids, and elevated concentrations of
nitrate, orthophosphate, and total phosphorus.
Concentrations of total suspended solids, nitrate,
orthophosphate, and total phosphorus decreased in a
downstream direction from the headwaters to the dam.
An increase in specific conductance was frequently
observed at mid -reservoir, usually at a depth of 4 to
6 m, downstream from a municipal WWTP outfall.
From about mid -reservoir to the dam, Rhodhiss
Lake thermally stratified during the summer of 1993.
During the summer, headwater inflows generally were
cooler than surface waters downstream and, therefore,
tended to sink and move as an interflow toward the
dam. Fall and winter temperature distributions
indicated multiple, alternating periods of stratification
and mixing from mid -reservoir to the dam. Following
the onset of thermal stratification in May 1993,
dissolved oxygen in this reach was quickly depleted
from bottom waters, and low concentrations persisted
in the hypolimnion throughout the summer. Inorganic
nutrients — nitrate, ammonia, and orthophosphate
—were depleted from the epilimnion during the
summer, probably by algal uptake. At the same time,
ammonia concentrations increased in the hypolimnion.
Concentrations of orthophosphate and total phos-
phorus also tended to be higher in bottom waters than
in surface waters during the summer.
Based on nutrient concentrations, Rhodhiss Lake
is classified eutrophic. However, nuisance levels of
phytoplankton were rarely observed, possibly because
short residence time and mixing patterns suppressed
algal growth. Limited light as a result of high abiogenic
turbidity also may have been a factor at the Huffman
Bridge site. From May through September 1993, mean
chlorophyll a concentrations were 1.4 µg/L at Huffman
Bridge, 10.2 µg/L at mid -reservoir, and 7.9 µg/L near
the dam. A maximum concentration of 52 µg/L was
observed at mid -reservoir on November 17,1993, and
was the only value that exceeded the State water -
quality standard for chlorophyll a of 40 µg/L.
Lower Creek had high specific conductance,
high concentrations of total suspended solids, and was
nutrient enriched. Fecal coliform concentrations
exceeded 200 cols/100 ml in 76 percent of the samples.
The two highest values occurred when streamflow was
elevated, but values in excess of 200 cols/100 ml were
observed across a wide range of flow conditions. Con-
centrations of fecal coliform bacteria greater than 200
cols/100 ml also were observed in Rhodhiss Lake-
37 percent of the time in the headwaters and 16 percent
of the time at mid -reservoir and in the forebay.
Maximum concentrations at reservoir sites occurred in
conjunction with heavy rainfall in March 1993.
Loadings of total suspended solids, nitrogen, and
phosphorus were calculated for Lower Creek site 53,
Rhodhiss Lake at Huffman Bridge (site 20), and for
selected point -source discharges. Results indicated that
almost all of the suspended solids and the majority of
the nitrogen and phosphorus entering the headwaters of
the reservoir originated from nonpoint sources.
Approximately 26 percent of the suspended solids
load, 21 percent of the total phosphorus load, and
6 percent of the total nitrogen load to the upper end of
Rhodhiss Lake occurred during one storm event during
March 23-25, 1993.
Nonetheless, point sources contributed
significant amounts of nutrients. Seven point sources
accounted for more than 99 percent of the permitted
wastewater flow in the Rhodhiss Lake watershed
downstream from Lake James. Five of these point
sources were located upstream from Huffman Bridge
and contributed 27 percent of the total nitrogen load
and 22 percent of the total phosphorus load. One of the
remaining point sources, a municipal WWTP, added
approximately 80,900 kg of nitrogen and 30,500 kg of
phosphorus to the mid -section of Rhodhiss Lake during
the study period.
A hydrodynamic and water -quality computer
model was used to simulate flow, transport, and water -
quality conditions in Rhodhiss Lake for 1993-94
conditions, and for other selected hypothetical condi-
tions. The model domain extended from Huffman
Bridge to Rhodhiss Dam, or a distance of 18.5 km, and
included five embayments or coves. There were
37 computational segments along the mainstem of the
reservoir, and each cove was represented by three
segments. All segments are 500 m long and 1 m thick.
Segment widths were chosen to represent the longi-
tudinal and vertical width variations in the reservoir
and to properly represent the reservoir volume, which
was estimated to be about 59 million m3.
Model simulations were made using data from
April 1, 1993, through Air 25, 1994. Model data
included (1) a record ofboudy flows at Huffman
Conclusions 59

Bridge and at Rhodhiss Dam, (2) estimated daily
mean inflows for the five embayments, (3) hourly
water temperature at Huffman Bridge, (4) daily mean
water temperature for the five embayments, (5) hourly
meteorological conditions (air temperature, dewpoint
temperature, cloud cover, and wind speed and
direction), (6) water -supply withdrawal rates, (7)
wastewater discharge rates, and (8) concentrations of
selected constituents in the inflows. The model
includes five parameters governing hydrodynamics and
heat transport, and 57 chemical kinetic rate
coefficients.
There was good agreement between measured
and simulated water levels at Rhodhiss Dam. The root
mean square difference between measured and simu-
lated water levels was 0.085 m, the maximum positive
(water level under -predicted) difference was 0.15 m,
and the maximum negative difference was 0.38 m.
Eighty percent of the differences between measured
and simulated water levels were between 0.02 and
0.12 m. The total range in measured water level during
the simulation period was 1.32 m.
At the mid -reservoir measurement site, water
temperature during April 1993 through March 1994
ranged from about 4 to about 30 °C. The difference
between each of the measured and corresponding
simulated water temperatures was computed for the
mid -reservoir site. The mean difference was -0.24 °C;
80 percent of the differences were between 1.26 and
-1.80 °C; and 95 percent of the differences were
between 1.7 and -2.4 °C. All of the results from the
water temperature simulations suggest that (1) the
calibrated model provides a reasonable simulation of
water temperature in Rhodhiss Lake, with most of the
simulated values within about 2 °C of the actual value;
and (2) near -bottom water temperature, particularly in
the deeper parts of the reservoir, is typically over -
predicted from 1 to 3 °C during the warmer months.
The simulated near -surface water temperatures
generally agree more closely with corresponding
measured values than simulated near -bottom water
temperatures. This, along with the simulated vertical
profiles of water temperature, suggest that themodel
over -predicts vertical mixing, resulting in excessive
transport of warmer surface waters to the cooler, deeper
waters of the reservoir.
Eleven water -chemistry constituents were
included in the Rhodhiss Lake model. Analysis of
results focused on DO, algae, and PO4 because ambient
water -quality standards exit for DO and algae, and also
because of the importance of PO4 in stimulating
phytoplankton growth. The difference between each
measured DO value at the mid -reservoir measurement
60 Rhodhiss Lake, North Carolina, 1993-94
site and the simulated DO at the corresponding time
and depth was calculated. These differences were
compared to the corresponding measured DO concen-
trations, the measurement date, and the depth of
measurement. Measured and simulated DO closely
agree when the ambient DO concentrations are greater
than about 8 mg/L. When the measured DO is between
about 5 and 8 mg/L, the simulated DO is typically
greater than the corresponding value. Differences
between measured and simulated DO for measured
concentrations less than about 5 mg/L vary, but
differences are likely due to poor simulation of the
timing of events. Most of the over -predictions at the
mid -reservoir site were at mid -depth, or depths
between about 2 and 7 m below the water surface.
These are the depths where the DO values of between
5 and 8 mg/L, which were over -simulated, most often
occur.
The cumulative frequency of occurrence of
measured DO concentrations at the mid -reservoir site
was determined and a similar analysis was performed
using the simulated DO values which correspond to
times at which DO measurements were made. The
frequency of occurrence of DO concentrations less
than 5 mg/L was almost the same for measured and
simulated DO. For DO concentrations between about
5 and 12 mg/L, simulated DO values were greater than
measured DO values. For example, about 50 percent of
the time simulated DO values were less than or equal to
about 9.5 mg/L; but measured DO values were less
than or equal to about 8.5 mg/L 50 percent of the time.
Generally, regulators and resource managers are most
interested in the occurrence of DO concentrations less
than 5 mg/L as opposed to higher values.
The calibrated model provides a reasonable
simulation of DO concentration in Rhodhiss Lake.
Near -surface and near -bottom DO appears to be
predicted better than DO concentrations at mid -depth,
where DO typically is over -predicted. There is good
agreement between simulated and measured frequency
of occurrence of DO concentrations less than 5 mg/L in
the reservoir, simulation of the exact timing of the low
DO events appears to be within about 5 days of the
actual occurrence. The simulated DO profiles do not
always exhibit the complex variations of DO with
depth which are seen in the measurements.
The calibrated Rhodhiss Lake model was
applied using 1993-94 boundary data to simulate the
movement of a neutrally buoyant, conservative tracer
through the reservoir. Results from these simulations
demonstrate (1) the use of the Rhodhiss Lake model in
evaluating the movement of a short-term or long-term
release into the reservoir, (2) the manner in which

nonconservative materials move through the reservoir,
without the confounding effects of chemical transform-
ations, regeneration, and settling; (3) the difficulty in
identifying a single residence time for the reservoir -
"residence times" vary seasonally, as well as with
depth; and (4) the effects of density stratification on
transport processes.
The effects of increased air temperature and
wind speed on DO concentrations were evaluated using
the model. The warmer temperatures slightly increased
the amount of time that simulated DO concentrations
were below 4 mg/L throughout the reservoir, but
increased wind speed had little effect on DO concen-
trations (probably because of interflow). Simulations
were made of the effects on DO concentrations and
algae as a result of changes in PO4 loadings from
Catawba River inflows (nonpoint sources) and from
bottom sediments. A 30-percent reduction in inflow
concentrations resulted in about a 20-percent decrease
in the maximum algal concentration. A 50-percent
reduction in the PO4 release rate from bottom
sediments resulted in only a small reduction in algal
concentrations, primarily in the spring.
The effects of changes in point -source discharge
concentrations of PO4 were simulated. Algal concen-
trations were affected only slightly; but when the
discharge rate was doubled and the PO4 concentration
was equal to the measured total phosphorus concen-
tration in the discharge, DO concentrations in the
reservoir were reduced. When the point -source
discharge was moved from about 9 m below the water
surface to 1 m below the water surface, simulated algal
concentrations were 2 to 3 times greater than for the
deep discharge. This was a result of the increased
deliveries of PO4 to the photic zone.
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W.H., 1994, Water -resources data, North Carolina,
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determination of inorganic substances in water and
fluvial sediments: U.S. Geological Survey Techniques
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545 p.
Guy, H.P., 1969, Laboratory theory and methods for
sediment analysis: U.S. Geological Survey Techniques
of Water -Resources Investigations, book 5, chap. Cl,
58 p.
Jaynes, M.L., 1994, Hydrologic, water -quality, and
meteorologic data from selected sites in the upper
Catawba River Basin, North Carolina, January 1993
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References 61

Valdese WWTP
Residual Chlorine
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (UG/L)
UPS BACKGROUND LEVEL (
IWC (%)
Allowable Concentration (ug
Fecal Limit
Ratio of 15.5 :1
228.7
9.5
14.725
17.0
0
6.05
281.03
Ammonia as NH3
(summer)
7Q10 (CFS) 228.7
DESIGN FLOW (MGD) 9.5
DESIGN FLOW (CFS) 14.725
STREAM STD (MG/L) 1.0
UPS BACKGROUND LEVEL 0.22
IWC (%) 6.05
Allowable Concentration (IT 13.11
Ammonia as NH3
(winter)
7Q10 (CFS)
200/100m1 DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
228.7
9.5
14.725
1.8
UPS BACKGROUND LEVEL 0.22
IWC (%) 6.05
Allowable Concentration (IT 26.34
7/20/98
JMN
NC0041696

Valdese WWTP
Residual Chlorine
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (UG/L)
UPS BACKGROUND LEVEL
IWC (%)
Allowable Concentration (ug
Fecal Limit
Ratio of 12.8 :1
228.7
11.5
17.825
17.0
0
7.23
235.12
Ammonia as NH3
(summer)
7Q10 (CFS) 228.7
DESIGN FLOW (MGD) 11.5
DESIGN FLOW (CFS) 17.825
STREAM STD (MG/L) 1.0
UPS BACKGROUND LEVEL 0.22
IWC (%) 7.23
Allowable Concentration (rr 11.01
Ammonia as NH3
(winter)
7010 (CFS) 228.7
200/100m1 DESIGN FLOW (MGD) 11.5
DESIGN FLOW (CFS) 17.825
STREAM STD (MG/L) 1.8
UPS BACKGROUND LEVEL 0.22
IWC (%) 7.23
Allowable Concentration (IT 22.07
7/20/98
JMN
NC0041696