NC0004979_Updated Supplemental Data for Permit Renewal_19960226

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Dukc Fou er Companrr
Eicct ric Sisimm Support
13339 Hggu Ferri Road
Huniersrr!'e. NC 28078-7939
DUPCZE PO d'EP
February 26, 1996
Mr: David A. Goodrich
NCDEHNR/Water Quality
Division of Environmental Management
P.O. Box 27687
512 N. Salisbury St.
Raleigh, North Carolina 27611-7687
Subject: Allen Steam Station
NPDES Permit No. NC0004979
Updated Supplemental Data for Permit Renewal
Certified: Z 403 319 120
Dear Mr. Goodrich:
Please find attached, updated supplemental information to be used in conjunction with the permit
renewal information already submitted. It was agreed that Allen's prior permit application
submittal (May 24, 1994) would suffice for the current renewal process. The revisions to the
supplemental data submitted May 24, 1994, are indicated in bold italic type. Please discard the
old supplemental data and replace it with the attached, updated supplemental data.
Please contact Mike Kowalewski at 704-875-4315 with any questions.
Sincerely,
`John S. Carter, Technical System Manager
(I. nvironmental Division
JElectric System Support
MEK/attachment

Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
General Information
Plant Allen utilizes water from the Catawba River for condenser cooling and
service water requirements. A schematic flow diagram of water use and
discharges indicating typical (average) flow rates for individual waste streams at
Plant Allen is attached. A brief discussion of each discharge follows. All flows are
based on historical data where possible or pump design capacities and normal run-
times.
Discharge 001 - Condenser Cooling Water (CM
Condenser Cooling Water
The CCW system is a once -through, non -contact cooling water`system that
removes heat rejected from the condensers and other selected heat exchangers.
Each of the 5 units at Plant Allen has two condenser cooling pumps. The number
of pumps used is dependent on unit load and intake temperatures with more
pumps running with higher loads and intake temperatures.
Units 1 and 2 share a common cooling water supply tunnel served by a total of 4
CCW pumps. Units 3 and 4 also share a tunnel and a total of 4 CCW pumps.
Unit 5 has a separate tunnel and 2 CCW pumps. The common tunnel design
enables three pumps to give Units 1 and 2 or 3 and 4 the equivalent of 1 1/2
pump operation. The 1 1/2 pumps operation adds an economical range or
flexibility when units are on partial load and when intake water temperatures are
minimal.
CONDENSER COOLING WATER PUMP CAPACITY
UNIT # 1 -PUMP GPM
1
55,500
2
55,500
3
83,000
4
83,000
5
83,000
1.5 -PUMP GPM
74,800
74,800
111,200
111,200
2 -PUMPS GPM
83,500
83,500
126,000
126,000
126,000
MAXIMUM COOLING WATER FLOW 545,000 GPM
All condenser tubes at Plant Allen are cleaned manually with metal or rubber plugs.
Mechanical cleaning is required once a year for most units. Chlorine or other
biocides are not used.
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
DischaMa 002 - Ash Basin
Storm Water run-off
The ash basin at Plant Allen accommodates flows from the yard drainage sump,
coal yard sump, ash removal lines and rainfall run-off from the basin watershed
area. The average rainfall run-off flows are based on 47 inches of rain per year
with 100% run-off from pond surfaces and 50% run-off from other areas. The
average run-off for the ash basin watershed area is 0.57 MGD. Average run-off to
the yard drainage sump is calculated to be 0.018 MGD.
The normal rainfall run-off plus ground water seepage from the coal pile area is
routed to the coal yard sump via the coal handling sumps. Perforated pipes
beneath the coal pile convey the ground water to the coal handling sumps. The
total average flow to the coal yard sump is calculated to be 0.053 MGD.
Oil Storage Run -Off
Plant Allen has an above ground oil storage tank with a capacity of 100,000
gallons, an above ground 5,000 gallon used oil storage tank and one underground
gas tank with a 550 gallon capacity. The above ground tanks have primary
containment in the form of dikes. Any spills not contained within the dikes
would be routed to the ash basin through the yard sumps. The underground gas
tank is of double -walled fiberglass construction.
All storage facilities are presently covered under the Spill Prevention and
Countermeasure Plan.
Boiler Cleaning:
All 5 boilers at Plant Allen are chemically gleaned with the next cleaning :scheduled
for 1997. The volume of the boilers determines the quantity of chemicals required
for a cleaning. Boilers #1 and #2 each have a water side volume of 26,700
gallons. The volume of boilers #3, #4, and #5 is 40,100 gallons each. The
volume of dilute waste chemical discharged from unit #1 or #2 during a cleaning is
294,000 gallons. The volume of diluted waste chemicals drained from #3, #4 and
#5 totals 450,000 gallons each. These wastes are drained through temporary
piping to the permanent ash removal lines which flow to the ash basin.
Immediately prior to the beginning of a boiler chemical cleaning procedure,
additional blocks are added to the ash basin discharge structure. This assures
longer retention time of the chemical wastes for proper treatment through
neutralization, precipitation, and ion -exchange as documented in the Ash Basin
Equivalency Demonstration (October, 1976). A list of the chemicals and amounts
required to clean the boilers at Piant Allen follows:
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
Chemicals
Boilers 1 &2
Boilers 3. 4 & 5
sodium bromate
550 lbs
550 lbs
ammonium carbonate
1000 lbs
1000 lbs
ammonium hydroxide
850 gal
950 gal
hydrochloric acid
3700 gal
5500 gal
thiourea
1680 lbs
2010 lbs
Citric acid
300 lbs
400 lbs
sodium sulfite
100 lbs
100 lbs
ammonium bifluoride
1100 lbs
1700 lbs
soda ash
2200 lbs
3400 lbs
Floor Drains
The wastes which enter the floor drains at Plant. Allen accumulate in the boiler
room sumps and turbine room sumps.
The water which flows to the boiler room sumps originates from such sources as
floor wash water, boiler blowdown, water treatment waste, condensates,
equipment cooling water, sealing water and miscellaneous leakage (refer to the
attached schematic of water flow for individual flows).The effluent from the units
1 through 4 boiler room sumps is flushed to the yard drain sump. The effluent
from the unit 5 boiler room sump is flushed to the power house sump, which is
then flushed to the yard drain sump.
The turbine room sumps accommodate flows from floor washing, leakage, and
occasional condenser water box drainage. The effluent from units 1 through 5
turbine room sumps are flushed to the yard drainage sump.
'1
Water Treatment System
The water treatment wastes at Plant Allen consist of sedimentation, filter
backwash, demineralizer regeneration wastes and boiler blowdown. The make-up
water treatment system is comprised of a clarifier, 5 gravity filters, 2 activated
carbon filters and a set of demineralizers. Make-up water is used in the boilers.
Clarifier:
The clarifier has an average production of -0.252 MGD. Polymer and clay
are used to affect precipitation and thus remove suspended solids from the
raw river water. Desludging of the clarifier takes places approximately 8%
of the unit run-time with an average volume of 2300 GPD going to the ash
basin.
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5
Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
Gravity Filters:
There are 5 gravity filters which follow the clarifier in the water treatment
process. One of these filters is backwashed every day with a waste flow of
21,000 GPD. The gravity filters are changed out on an as -needed basis with
approximately 620 ft3 of used filter medium (anthracite) disposed of in the
ash basin. In September of 1996, all 5 gravity filters will be physically
removed and replaced with two pressure filters for filtration. Each pressure
vessel will contain 75 ft3 of anthracite, 34 ft3 of quartz, and 17 ft3 of
garnet. Each vessel will use product water to backwash at a rate of 561
gpm. On average, one vessel will backwash per day. The contents of the
pressure .filters will periodically be changed out as needed with the used
filter medium disposed of in the ash basin.
Activated Carbon Filters
In addition to the gravity filters, there are 2 activated carbon filters. These
filters are backwashed twice per month. Approximately 30,000 gallons of
water are required to backwash each of these filters. The activated carbon
filters are composed of approximately 250 ft3 of granular activated carbon
(coal). The spent filter medium is changed out yearly and is disposed of in
the ash basin.
Reverse Osmosis (RO) Prefilters:
There are 2 Reverse Osmosis (RO) prefilter vessels containing spent bead
resin which are used to filter suspended solids. Both filters are backwashed
once per week with the backwashed material routed to the ash basin. Total
waste for both filters is 4500 gallons per week. Sometime later this year,
the spent resin filter medium will be replaced with sand. However, the
overall process will remain the sam&-. �
Reverse Osmosis Unit.
A Reverse Osmosis (RO) unit is used to decrease .the conductivity in the
make-up water, thereby increasing the -efficiency of the demineralizers and
reducing the amount of chemical needed for demineralizer regeneration.
Sulfuric acid (25%) is injected at a rate of approximately 5 gal/day to control
pH. During operation, the unit has a continual blowdown of 60 gal/min
which is discharged to the ash basin. Sodium bisulfite is then injected
downstream of the RO unit to remove any residual chlorine.- The
concentration of sodium bisulfite is maintained at 2 ppm. The RO unit is
cleaned on a quarterly basis with the waste going to the yard drains and
eventually the ash basin. During a cleaning, approximately 30 lbs of the
cleaner OSMO AD -20 containing sulfamic acid, citric acid and sodium lauryl
sulfate is used. EDTA may also be employed as an additional cleaning agent
at a rate of 40 lbs per quarterly cleaning. The manufacturer of the RO
membrane recommends that a small amount of biocide (1sothiazolone
derivative) be used as needed to control biofouling. Generally, the amount
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
of biocide needed is on the order of 1 - 2 grams in 3 gallons of water. Also
used is a generic cleaner consisting of tri -sodium phosphate, sodium
laurylsulfate and sulfuric acid with approximately 400 gallons of waste
water going to the ash basin.
Demineralizer:
The demineralizer consists of 2 mixed -bed cells. Only one of these cells is
operated at any one time. The cell which is in operation is regenerated
approximately once every 4 days of operation. A regeneration requires 42
gallons of sulfuric acid (78-80%) and 150 gallons of 50% sodium
hydroxide. An average dilute waste chemical and rinse flow of 20,000 gal
is realized. The dilute acid and caustic are discharged to the floor drains
simultaneously through the same header for neutralization purposes. All
regeneration wastes are flushed to the ash basin. Once every 5 years,
1000 lbs of sodium hydrosulfite will be used clean the demineralizer resin.
The demineralizer resin is changed out approximately once every 5 years
with the spent resin going to the ash basin. Approximately 1 mL of -the
surfactant Triton CF -54 or similar product is added to the new resin to
improve separation...
Boiler Blo wdo wn:
Each of the 5 boilers at Plant Allen blowdown at an average rate of
approximately 500 lbs. of steam per hour. The blowdown is allowed to
flash in a blowdown tank. Most of the blowdown is vented to the
atmosphere with a minimal amount of condensate discharged to the boiler
room sump. The average condensate flow to this sump is 0.004 MGD.
Hydrazine is maintained at a concentration of 25 ppb in ,the condensate
system for deoxygenation. A minute amount of hydrazine (< 10 ppb) may
be present in the condensate flow to the boiler room sump.
Sanitary Wastes
A well supplies the drinking water requirements of Plant Allen. The sanitary waste
at Plant Allen is treated in a septic tank followed by a sand filter. Approximately
190 people are responsible for the load on this system. An average flow of 4850
GPD is treated by the unit. The sand filter effluent is routed to the ash basin via
the coal yard drainage sump. The sand filter sand is replaced on as -needed basis
with the sand disposed of in the ash basin.
Preheater Flushes
Preheaters-are flushed with raw water approximately 2 times per year to remove
sludge and corrosion products. There are 5 preheaters at Allen Steam Station that
would require approximately 100,000 gallons of flush water each. The flush
water is routed to the ash basin.
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
Ash Disposal
Plant Allen utilizes electrostatic precipitators to remove fly ash from its stack
gases. These precipitators require approximately 4.5 MGD for fly ash sluicing to
the ash basin. Bottom ash sluicing to the basin requires approximately 2.8 MGD
for a total average ash removal flow of 7.3 MGD.
Recirculating Water System
Plant Allen has 2 recirculating water systems (RCW): a chiller system and a pump
cooling water system. Both systems use the biocide H-310, H-303WB, H-300 or
similar products. In addition, the corrosion inhibitor CS or similar product is used.
Generally, these systems are closed loop, but may need to be drained occasionally.
All such water would enter the floor drains and then be discharged to the ash
basin.
Miscellaneous Waste Streams
Laboratory Wastes:
The chemistry lab on site performs a variety of water analyses and routine
sample collections. Therefore several chemicals are used in the lab in small
quantities for sample preservation, bottle rinsing, equipment calibration,
conductivity analyses, etc. The wastes are flushed down the sink and
discharged into the yard drainage sump and then pumped to the ash basin.
(See attached table of hazardous substances for specific chemicals used and
maximum quantities kept in the lab.)
CO2 Injection System:
During warmer periods of the year, -'algae blooms occur in the ash basin
causing pH levels to rise. A CO2 system is utilized during these events to ,
maintain the pH level below 9.0 standard units.
Turbine Non-destructive Testing:
Approximately once per year, one turbine is tested for cracks in the
generator shaft using an ultrasonic nondestructive test. During the process
a maximum of 400 gal of demineralized water mixed with 4 gal of corrosion
inhibitor is used and discharged to the ash basin.
Heat Exchanger Cleaning:
From time to time, it may be necessary to clean the small heat exchangers
with polyacrylamide, polyacrylate, sodium laurylsulfate and tri-
sodiumphosphate. All wastes would be routed to the ash basin.
Condensate Polishers:
Plant Allen utilizes condensate polishers which divert a portion of the normal
condensate (closed system) flow through one of two cells per unit. The
polishers provide filtration as well as ion exchange functions to remove or
G

Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
substantially reduce dissolved solids and suspended matter present in the
condensate stream. The polishers require precoating with a combination of
anion and cation resin. To facilitate precoating, 125-150 mL of a solution of
polyacrylic acid (25%) is added to the precoat slurry. Upon exhaustion, the
precoat is removed from the filters by water / air blasting and flushed to the
ash basin via sumps. Condensate water is used to remove the exhausted
precoat at the rate of:
Unit 1 & 2 - 1558 gal/precoat
Units 3 -5 - 2090 gal/precoat.
A total average waste flow of approximately 980 GPD to the ash basin is
realized.
Condenser Leakage Testing:
Fluorescing Dye Method
Approximately 1 Ib. of a disodium fluorescing dye added to 15,000 gals of
demineralized water is used occasionally to test the condensers for leakage.
All wastes from the testing would be routed to the ash basin.
Sulfur Hexafluoride Method:
Periodically, sulfur hexafluoride is injected into the condenser tubes to locate
condenser tube leaks. Sulfur hexafluoride is a chemically inert,
nonflammable, nontoxic gas with an extremely low water solubility. It is
estimated that 150 grams of sulfur hexafluoride would be used during the
leak detection process. Most of the sulfur hexafluoride will be volatilized
during the leak detection process.
Discha&= 003 -
Outfall 003 discharges into. the CCW discharge canal. The discharge consists of
cooling water from units 4 and 5 mill oil coolers, boiler feedpump hydraulic coolers
and other miscellaneous equipment cooling. This water is once -through, non -
contact cooling water withdrawn from the service water system.
Dischame 004 -
Equipment Cooling Water
Cooling water for units 1 and 2 mill oil coolers, boiler feed pump hydraulic coupling
and other miscellaneous equipment is discharged through outfall 004. This water
is once -through, non -contact water drawn from the service water system.. In
addition, water from a vehicle rinse -down area is directed to this outfall. The rinse
water contains no soaps or other additives
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
Intake Screen Backwash
The intake screens at Plant Allen are flushed on an "as needed" basis. Backwash
usually averages 2 hours per shift. The average volume required is 0.84 MGD.
The large debris floating on the river is caught on the parallel bar screens. This
trash is collected and disposed of in a landfill. The silt, twigs, leaves and other
light debris collected on the rotating screens are indigenous to the river and are
therefore flushed back with no harmful environmental consequences.
Discharge 005 - Asiatic Clam Rho
Water for the Unit 5 CCW water is filtered for Asiatic clams. Asiatic clams,
common in Lake Wylie, can clog the condenser tubes. This filter is backwashed
once a week for 15 minutes. A maximum flow of 3000 GPD is realized. No
other additives are in the backwash water.
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
Plant Allen 316(a) Determination
Duke Power Company's 316(a) demonstration (March 1976) concluded that the
"heated discharge from Plant Allen is such that the protection and propagation of a
balanced indigenous aquatic community in and on Lake Wylie is assured."
Duke's operation experience during the past five years under the thermal
limitations imposed in NPDES Permit No. NC0004979 substantiates the above
conclusion and further supports Duke's belief that the operating characteristics of
the station have a minimal effect of the aquatic environment of Lake Wylie.
Surveys of the aquatic community in Lake Wylie demonstrate that a Balanced
Indigenous Population exists in Lake Wylie (see attached report). Accordingly,
Duke requests a 316(a) variance and further requests that the thermal limitations
imposed in the permit be continued. -
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Plant Allen, Gaston County
NPDES # NC0004979
2/26/96
LIST OF HAZARDOUS SUBSTANCES (SECTION 31 1)
SUBSTANCE
QUANTITY
LOCATION
USE
Ammonia molybdate
2000 gm
Lab
Water Analysis
Acetic acid
1 qt
"
Ammonia
1 Ib (gas)
Powerhouse
Water treatment
Ammonium hydroxide
55 gal
11it
Chlorine
15001b
ifif
Ferric sulfate
360 g
Lab
Water Analyses
Hydrochloric acid
2 gal
itif
Monoethylamine
6 L
it
Water Analyses
Nitric acid
6 qt
if
Potassium hydroxide
3 Ib
it
Sodium bisulfite
5 Ib
Powerhouse
Water Treatment
Sodium hydroxide
5000 gal
ifDemineralizer
regen.
Sulfuric acid
5000 gal
Yard
Demineralizer regen
Sulfamic acid
100 Ib
Powerhouse
RO unit cleaning -
Values represent maximum quantities on-site and do not necessarily reflect
quantities discharges. Treatment of these and other chemical substances is
achieved by the ash basin. Refer to "NPDES Supplemental Information" for a list
of chemicals and amounts used for boiler cleaning.
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