NC0004961_Renewal Application_20090827

f
` Duke
CORPORATE EHS SERV/CES
Energy®
Duke Energy Corporation
526 South Church St
Charlotte, NC 28202
Mailing Address
August 27, 2009
EC13K / PO Box 1006
g
Charlotte, NC 28201-1006
Ms Charles H Weaver, Jr ,I'VE"A D
State of North Carolina t
Department of Environment and Natural ReSR S
Division of Water Quality2111
NPDES Unit AUG 3 1
1617 Mail Service Center
Raleigh, North Carolina 27699-1617 DENR , WATER OUAL11Y
POINT SOURCE BRANCH
Subject- Duke Energy Carolinas LLC — NPDES Permit Application
Riverbend Steam Station - #NC0004961
Dear Mr Weaver
Duke Power requests the subject permit be renewed and reissued The above
referenced permit expires February 28, 2010. As mandated by North Carolina
Administrative Code 15A NCAC 2H 0105 (e), this permit application for renewal is
being submitted at least 180 days prior to expiration of the current permit
Please find enclosed in triplicate, the renewal application, which includes the
following items*
EPA Form 1
EPA Form 2C
EPA Form 2F
Site Maps
Water Flow Diagram
Supplemental Information
Duke Power requests notification that this application is complete
Additionally, the attached report, "Assessment of Balanced and Indigenous
Populations in Mountain Island Lake," continues to indicate recovery of aquatic
populations and includes a request to approve recommended monitoring program
modifications going forward Therefore, this report also supports renewal of the
current thermal monitoring requirements of outfall #001.
www duke -energy com

The following monitoring reductions at outfall #002 are requested based on
historical monitoring data.
• Total Suspended Solids — reduce monitoring frequency from 2/month to
1 /month.
• Oil & Grease —reduce monitoring frequency from 2/year to 1/year.
• Total Copper — eliminate quarterly monitoring requirement, only monitor
during boiler chemical cleanings.
• Total Iron - eliminate quarterly monitoring requirement, only monitor during
boiler chemical cleanings.
• Total Nitrogen — reduce monitoring frequency from 2/year to 1/year.
• Total Phosphorous —reduce monitoring frequency from 2/year to 1/year.
Thank you in advance for your assistance on this matter Should you have
questions regarding this application, please contact me at [phone].
Sincerely,
,Lkw(_
Allen Stowe
Water Management
Attachments
cc w/: Mr. David Russell - NCDENR Winston-Salem R.O.
Mr. Jimmie Overton — NCDENR, Raleigh, N.C. (BIP Report 3 copies)

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REFERENCE: �Y
BACKGROUND DATA: USGS TOPOGRAPHIC QUAD, MOUNT ISLAND LAKE AND LAKE NORMAN SOUTH �' cJ 1
,NAD 83, METERS WAS OBTAINED FROM NC ONEMAP GEOGRAPHICAL INFORMATION (GIS) WEBSITE. Kilometers
THE PROPERTY DATA WAS OBTAINED FROM THE GASTON COUNTY NORTH CAROLINAGIS DEPARTMENT.
' PLEASE NOTE THIS DATA IS FOR INFORMATIONAL PURPOSES ONLY. IT IS NOT MEANT FOR DESIGN, LEGAL, 0 0.5 1�
OR ANY OTHER USES. THERE ARE NO GUARANTEES ABOUT ITS ACCURACY. S&ME, INC. ASSUMES NO
RESPONSIBILITY FOR ANY DECISION MADE OR ANY ACTIONS TAKEN BY THE USER BASED UPON Miles
INFORMATION OBTAINED FROM THE ABOVE DATA.
SCALE: AS SHOWN FIGURE
DATE: Duke
LOCATION MAP No.
06-08-2009 RIVERBEND STEAM STATION
DRAWN BY: RDP NPDES # NCO04961 1
PROJECT NO: PowEnergy. RIVERBEND STEAM STATION
L 1411 08-140 1 GASTON COUNTY, NORTH CAROLINA

INTAKE TUNNEL FROM CATAWBA RIVER
335 MGD
INTAKE SCREEN BACKWASH
' INDUCED FAN & PREHEATER
BEARING COOLING WATER
PLANT CHILLER SYSTEM
TURBINE Ll 13E OIL COOLERS
CONDENSATE COOLERS
EXHAUST STEAM CONDENSERS
INTAKE TUNNEL UNWATERING
SUMP
FILTERED WATER AND ASH
REMOVAL SYSTEM
FILTERED WATER SYSTEM
LINE DRAWING OF WATER FLOW THROUGH RIVERBEND STEAM STATION
INDUCED DRAFT FAN COOLING 0.15 11GD
WATER
PREHEATER BEARING COOLING 0.15 MGD
WATER
NC#0004961 Permit Appl.
August 2009
STORM WATER FROM ROOF
DRAINS AND PAVING
0.01 MGD
Y
0.023 MGD
DRINKING WATER SYSTEM STORM WATER FROM COAL PILE
(Mount Holly Drinking Water Supply)
GENERAL PLANT/I'RAILER
SANITARY WASTEWATER
LABORATORY DRAINS
CHEMICAL MAKEUP TANKS AND
DRUMS RIN&ATF.
DEMINERALIZER SYSTEM
0.004 MGD
GRAVITY FILTER BACKWASH
AND CLARIFIER SLUDGE
Flows are approximated averages which have wide variability on a daily basis.
r
ZMN S
�3 MGD( GROUNDWATER REMEDIATION
OHJWATERSEPARATOR
O.OS NIDD TRACK TOPPER SUMP
(GROUNDWATER)
ASH REMOVAL SYSTEM
3 MG D
� v
LJ NIGD
L Nil,
SANITARY SYSTEM
0.006 MGD
1 MGD
TURBINE ROOM SUMPS
F
BOMER ROOM SUMPS ASH BASIN
1.3 MGD
STORM WATER FROM POND EVAPORATION
AREAS AND UPGRADIENT 0.31 MGD AND SEEPAGE
WATERSHED 1 MGD
0.004 MGD
OLD END PIT SUMP
002 (5 MGD)
001 MOUNTAIN ISLAND LAKE
361.5 MGD)

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 2 of 20
General Information
Riverbend Steam Station (RB) is a coal-fired electric generating plant owned and operated by
Duke Energy Corporation. RB is located at 175 Steam Plant Road, six miles northeast of Mount
Holly, North Carolina.
RB's first three generating units were retired in the late 1970s. Units 4 and 5 are each capable of
generating 94,000 kilowatts of electricity. Units 6 and 7 are rated at 133,000 kilowatts each.
In addition to the coal-fired units, four combustion turbines supply 30,000 kilowatts each for use
during periods of peak demand for electricity. Combustion turbines operate differently from
steam plants. They burn oil or natural gas to heat compressed air, which expands and drives a
turbine -generator to produce electricity.
RB utilizes water pumped from the Catawba River (Mountain Island Lake). The outfalls at RB
discharge the water back into the Catawba River. A schematic flow diagram of water use,
treatment and discharge is on Page 22 of 22 of this document. A narrative description of the
individual waste streams follows.
Outfall 001 - Condenser Cooling Water (CCW)
The CCW system is a once through non -contact cooling water system which removes heat from
the condensers and other selected heat exchangers Raw water from the Catawba River is passed
through condensers and auxiliary equipment on a "once -through" basis to cool equipment and
condense exhaust steam from the turbines.
When RB is operating at full power, it is has a design capacity to pump 622.1 Million Gallons
per Day (MGD) of cooling water through a network of tubes that runs through the condenser and
selected heat exchangers (e.g. turbine lube oil cooler, condensate cooler, plant chiller system).
This raw water in the condenser tubes absorbs heat from a closed system of highly purified
exhaust steam from the turbines and converts it back to water. Condensed exhaust steam is then
returned to the boilers and is recycled a number of times. The cooling water is returned to the
lake. No chemicals are added and only heat rejected from the condensers and auxiliary
equipment is absorbed by the cooling water, hence the term "once through, non -contact cooling
water" is applied.
The condensers tubes are periodically cleaned mechanically. Metal or plastic scrapers are forced
through the tubes to rid them of scale or other deposits.
Each unit at RB has two CCW pumps. The pump capacities are listed below. Normal plant
operation of the CCW pumps is based on intake and discharge temperatures and unit load.
Further, the units are operated on different computer highways or WDPF control systems to
avoid a system trip that would suddenly reduce production of electricity. This practice leads to a
higher reliability factor for the units and protection of aquatic life taking refuge in the discharge
canal during cold weather. Multiple control units assure that the entire discharge flow at outfall
001 and the heated effluent will not suddenly stop.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 3 of 20
Unit No. I -Pump GPM 2 -Pump GPM
1 36,000 72,000
2 36,000 72,000
4 33,500 67,000
5 33,500 67,000
6 38,500 77,000
7 38,500 77,000
Filter Backwash from Raw Water Intake Screening Device
Raw water intake screens are backwashed on an as needed basis. Normally, the screens require
backwashing once per twelve hour shift for a period of approximately 20 minutes. The water
required for backwashing is supplied by a low pressure service pump with a design capacity of
800 gpm. Therefore, the average flow of water used to backwash the screens is 0.032 MGD.
Should it become necessary to backwash the screens on a continuous basis the maximum flow
would be 1.15 MGD. This intake screen backwash is discharged into the condenser cooling
water line downstream of the condensers. The debris collected on the screens consists mainly of
twigs, leaves, and other material indigenous to the Catawba River.
Intake Tunnel Unwatering Sump
In the event that maintenance activities are needed in the intake tunnels an unwatering sump is
provided to remove water from the tunnel(s). To date this operation has not been performed, but
it is available should the need arise. Raw water in the tunnels can be removed by a sump pump
to the discharge side of the condensers which would then exit at outfall 001.
Turbine Non -Destructive Testing
Bore sonic testing of turbine rotors is infrequent, approximately once every 5 years. A maximum
of 400 gallons of demineralized water mixed with 4 gallons of a corrosion inhibitor, e.g. Calgon
CS, is used during the testing per unit. The mixture is drained and mixed with once through
cooling water downstream of the condensers which discharges at outfall 001.
Sawdust Addition to the Condenser
When the condenser tubes are suspected to be leaking, Riverbend Steam Station adds as needed
proximately 50 pounds of sawdust in the plant intake area, in order to temporarily stop the
leaks. Once the unit comes off line, the leaks are then permanently repaired.
Outfall 002 - Ash Basin
The ash basin at RB accommodates flows from the yard drainage sump, boiler room sump, ash
removal system and non -point source storm water. Total average influent from these sources
combined is approximately 5 MGD. At times, due to unit loads, rainfall, evaporation and
seepage of ash basin ponds, the amount of effluent may be quite different than influent volumes.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 4 of 20
pH Adjustment
During warm 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 between 9.0 and 6.0
standard units. An acid injection system utilizing sulfuric acid and also a sodium hydroxide
injection system may also be utilized for additional pH adjustment.
Yard Drainage Sump
The yard drainage sump is a large concrete structure that has four level controlled pumps that
direct wastewater from RB to the ash basin. These pumps are operated on a rotating basis.
Usually two pumps are arranged so that one pump is used in a primary capacity and the other is
backup. After a preselected period the controls are changed so that different pumps are utilized.
The yard drainage sump collects wastewater from many sources, such as, sanitary system,
groundwater remediation system, and turbine room sumps. This sump also collects once through
non -contact cooling water from the induced draft (ID) fan motors and the preheater bearings
located in the emission stacks. The yard drainage sump also collects storm water runoff from the
coal pile, rail access, powerhouse roof and paving. Groundwater from a foundation drainage
system under the track hopper is also intermittently discharged to the yard drainage sump. The
combined average flow from all sources tied to the yard drain sump is approximately 1.4 MGD.
Sanitary System
Plant sanitary wastes are treated by a series of three 4,000 gallon septic tanks in parallel and a
1,200 gallon holding tank. Sanitary effluent is pumped from the discharge chamber of the septic
tanks to the ash basin via the yard drainage sump for final treatment. The sanitary waste system
is designed for 12,500 gallons per day. This design was based on a maximum and average of
300 and 150 people, respectively. Based on annual data the average daily flow to the yard drain
sump has been approximately 0.006 MGD.
The sanitary system accommodates wastewater flow from the following sources:
• general plant sanitary wastewater
• chemical makeup tanks and drum rinseate (Intermittent rinse water containing small
amounts of aluminum sulfate, sodium hydroxide, hydrazine, ammonium hydroxide)
• laboratory drains (Small amounts of laboratory chemicals used to test wastewater
effluents and high purity boiler water)
• office trailer sanitary wastewater.
Ground Water Remediation System
This system was installed in 1992. Groundwater is pumped through an oil water separator and
then to the turbine room sump. Trace amounts of volatile organic compounds may be in this
wastewater, such as naphthalene, chrysene, methyl tert-butyl ether, and bis (2-ethylhexyl)
phthalate. The average daily flow from this system is 2 gpm approximately 0.003 MGD. A
revised groundwater corrective action plan has been submitted to NC DENR that specifies a
treatment capacity capable of 20 gpm or 0.03 MGD.
Vehicle Rinse -down System
Effluent from a vehicle rinse -down area is directed to the ash basin. The rinse water contains no
soaps or other additives.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 5 of 20
Turbine Room Sumps
The turbine room sumps collect approximately 1 MGD of wastewater via a network of floor
drains from intermittent sources listed below:
• Condensate from the feed water system (seal water, valve and pump leakage, cooling
water, vents),
• Equipment cooling water, i.e. air compressors,
• Floor wash water containing janitorial products,
• Boiler room sump overflow and
• Emergency fire fighting water Chiller condensates.
ID Fan and Preheater Bearing Cooling Water
Once through non -contact cooling water is supplied to the ID Fan motor and preheater bearings
to remove excess heat. The rate of flow through these two pieces of equipment which discharges
to the yard drainage sump is approximately 0.03 MGD.
Railroad Track Hopper Sump
This sump collects groundwater from a foundation drain system underneath the track hopper.
The flow is usually intermittent, and the pump capacity is 100 gpm MGD. On a daily basis it is
estimated that the run time is 50% which would correspond to a flow of 0.05 MGD.
Boiler Room Sumps
The average flow pumped from the boiler room sumps directly to the ash basin is approximately
1.3 MGD. The sources of input to the boiler room sumps include the following:
Filtered Water System to the Old End Pit Sump
The filtered water treatment system at RB consists of a clarifier, five gravity filters, two
activated carbon filters, Reverse Osmosis (RO) system and one set of demineralizers.
Wastewater and filter media from the filtered water system (except RO and demineralizer
wastewater which goes to the boiler room sump) is drained to what RB commonly refers
to as the "Old End Pit Sump". From the pit sump the wastewater is pumped to the Boiler
Room Sump.
Clarifier
The clarifier utilizes typical water treatment chemicals such as, aluminum sulfate, sodium
hydroxide, and calcium hypochlorite for the primary treatment of raw water. The
sedimentation wastes collected in the clarifier consists of solids that were suspended in
the service water plus aluminum hydroxide precipitate formed as a result of adding
aluminum sulfate (alum) and sodium hydroxide. The quantity of alum used per year is
approximately 1320 gal/yr. The average volume of water required for desludging the
clarifier is approximately 0.002 MGD. These sedimentation wastes, along with dilute
water treatment chemicals, and by-products are piped to a floor drain which flows to the
old end pit sump where they are drained to the 4 and 5 boiler room sump and ultimately
to the ash basin.
Gravity Filters
There are five gravity filters composed of anthracite (coal) which follow the clarifier in
the water treatment process. Normally, one of these filters is backwashed each day.
Approximately 0.002 MGD of backwash water is required for each filter. This

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 6 of 20
wastewater flows through floor drains to the old end pit sump which pumps to the yard
drain sump. The anthracite filter is changed on an as needed basis with the spent filter
media being sluiced to the ash basin via the boiler room sump.
Activated Carbon Filters
The filtered water system includes one activated carbon filter. This filter is typically
backwashed once a week. The flow of water required to backwash filters is 30 minutes at
100-120 gpm. The backwash flows to the #9 and #10 boiler room sump and is pumped to
the yard drain sump. Approximately 60 ft3 of activated carbon is replaced yearly with the
spent carbon sluiced to the ash basin via the boiler room sump.
Reverse Osmosis (RO) Prefilters
There is one RO prefilter vessel containing —twenty-one 1 micron cartridge filters which
are used to filter suspended solids. Cartridges are changed out every 1-2 months.
Reverse Osmosis Unit
A RO unit is used to purify the make-up water, thereby increasing the efficiency of the
demineralizers and reducing the amount of annual chemicals needed for demineralizer
regeneration. During operation, the unit has a continual blowdown of 50 gpm, which is
discharged to boiler room sump and then to the ash basin. The RO unit is cleaned on a
quarterly basis with the wastewater going to the # 9 and #10 boiler room sump and then
to the ash basin. During cleaning, approximately 30 lbs of the cleaner OSMO AD -20
containing sulfamic acid, citric acid and sodium lauryl sulfate is used. Also used is a
generic cleaner consisting of tri -sodium laurylsulfate, sulfuric acid and a biocide with
approximately 400 gallons of wastewater which is sluiced to the ash basin.
Demineralizer regeneration wastewater
The demineralizers consist of 2 mixed -bed cells which supply make-up water to the
boilers and other closed systems. Normal plant operation requires that only one
demineralizer cell operates at a time. Each cell has a capacity of 140 gpm. Each cell is
regenerated approximately 12 times per year. Each year RB will use an estimated 800
gallons of 50% caustic and 400 gallons of 93% sulfuric acid for demineralizer
regenerations. An average diluted waste chemical and rinse flow is approximately 0.004
MGD. The diluted acid and caustic are discharged from the cell simultaneously through
the same pipe header for neutralization purposes. The regeneration wastes flow to the #9
and #10 boiler room sump, to the yard drain sump and then is pumped to the ash basin.
The spent resin is sluiced to the ash basin.
Closed system drainage, cleanings, testing containing:
Closed systems containing corrosion inhibitors, e.g. Calgon CS and MCS plus2, Biocides,
e.g. Calgon H-300 and H-510, Bulab 6002, Cleanings, e.g. small heat exchangers,
Dispersant, e.g. polyacrylamide, Wetting agent, e.g. sodium lauryl sulfate, Detergent, e.g.
tri -sodium phosphate, Leak testing, e.g. disodium fluorescing dye are utilized. These
chemicals are periodically routed to the station sumps and ultimately to the ash basin.
Miscellaneous system leakages:
Small leaks from pump packings and seals, valve seals, pipe connections periodically
occur and are sent to the ash basin via plant sumps.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 7 of 20
Boiler blowdown
During unit startup and until water chemistry stabilizes, the blowdown from the boilers is
allowed to flash into a blowdown tank. After water chemistry has stabilized the amount
blowdown condensate flow is miniscule. The condensate is drained to the boiler room
sumps. Trace amounts of hydrazine, ammonia, and silica oxide is present in the
condensate. During normal operation Boilers #7 and #8 blowdown at an average rate of
1000 lbs. of steam per hour. Boilers #9 and #10 blowdown at an average rate of 1000 lbs.
of steam per hour. The combined condensate flow from these blowdown averages
approximately 0.005 MGD. This flow is routed to ash basin via the boiler room sump. A
significant portion of this blowdown steam is vented to the atmosphere.
Chemical Cleaning of Boilers
Boilers #7, #8, #9 and #10 at RB are chemically cleaned on an as needed basis (Boilers
#146 are retired). Boiler tube inspections are performed during outages to determine if
cleanings need to be scheduled. Boilers #7 and #8 are natural circulation boilers and #9
and #10 are controlled circulation boilers.
The volume of the boilers determines the quantity of chemicals required for cleaning.
Boilers #7 and #8 each have a water -side volume of 26,300 gallons. The volume of #9
and #10 boilers is 24,900 gallons each. The total volume of dilute waste chemicals,
including rinses, discharged from #7 or #8 boilers during a chemical cleaning is 365,000
gallons. The total volume of diluted waste chemicals drained from #9 or #10 is
approximately 275,000 gallons. These wastewaters are drained to the boiler room sump
which pumps directly to the ash basin. Immediately prior to the beginning of a boiler
cleaning, additional stop logs are added to the ash basin discharge structure. This action
ensures longer retention time of the chemical wastes in the ash basin for proper treatment
through dilution, neutralization, precipitation, and ion -exchange as documented in the
Ash Basin Equivalency Demonstration (October 1976). Chemicals and approximate
amounts required to clean the boilers are listed below:
CLEANING CHEMICALS AMOUNT USED PER BOILER
18t Stage (Copper Removal Solution) Boiler #7 or #8 Boiler #9 or #10
Sodium Bromate 550 lb 550 lb
Ammonium Carbonate
*Ammonium Hydroxide
(26°Be')
2°d Stage (Iron Removal Solution)
(Includes rinses and neutralization)
*Hydrochloric Acid (31.5%) (20°Be')
*Ammonium Bifluoride (0.5%)
Copper Complexer (0.75%)
1000 lb
850 gal
1000 lb
850 gal
Boiler #7 or #8 Boiler #9 or #10
3600 gal 3400 gal
11001b 10501b
16601b 16301b
Thiourea or equivalent
Sodium Carbonate 3000 lb 3200 lb
Citric Acid 300 lb 200 lb

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 8 of 20
Alkaline Boilouts Boiler 47 or #8 Boiler 49 or #10
(only after major boiler tube work)
Soda Ash 2000 lb 2000 lb
Triton X-100 Detergent (0.5%) 10 gal 10 gal
Antifoam Agent (0.025%) 5 gal 5 gal
*These chemicals are present in amounts greater than the reportable quantity as identified under
the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). If a
spill of these chemicals did occur it would in most cases be sent to the ash basin where
treatment would occur.
Ash Removal System
RB utilizes electrostatic precipitators as its air pollution control devices. The fly ash captured in
these precipitators is water -sluiced to the ash basin. Bottom ash from the boilers is also water -
sluiced to the ash basin. Approximately 3 MGD of water is required for this purpose.
Electrostatic precipitators at RB are normally cleaned by mechanically vibrating the wires and
rapping the plates inside the precipitator. Before major precipitator work is performed the
precipitators are washed down with water. The wash water is pumped to the ash basin.
Miscellaneous
The ash basin receives the following miscellaneous wastestreams: Laboratory wastes,
photographic wastewater, de-icing products and expired reagents.that will be co -managed other
wastewater for compliance with NPDES permit limits.
Outfall 002A — Yard Drainage Sump Overflow
An overflow pipe that directs flow from the sump to the ground was included in the construction
of the yard sump. This modification was performed to prevent submergence and damage of the
pump motors within the sumps in the event that all pumps failed or redundant power supply lines
could not be restored in a timely manner. Given significant overflows, the waste water could
potentially flow into the Catawba River. This type of incident will rarely occur.
Spill Prevention
Oil Storage
RB presently has four above ground oil storage tanks - one 4,250,000 gallon fuel oil tank, one
27,000 gallon light -off fuel oil tank, one 20,000 gallon mineral oil storage tank, and one 2,000
gallon used oil storage tank.
All above ground tanks have secondary containment provided which are capable of containing
the entire contents of the tank. An oil trap tank is located in the drainage area of the 4.25 million
gallon oil tank as an added precaution.
All oil storage facilities are presently covered under Spill Prevention Control and
Countermeasure Plans (SPCC), as well as a site Facility Response Plan (FRP).

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 9 of 20
STORM WATER
RB has several storm water outfalls that discharge to the Catawba River. RB was included in the
group application submitted to the Environmental Protection Agency in March of 1991. Storm
water outfalls SW001, SWO02 and SWO03 have been evaluated and are representative of the
other storm water outfalls at RB.
Site Description
The RB site covers 572 acres and includes a plant yard of approximately 20 acres and three
switchyards, which cover about eight acres. The coal storage yard encompasses 13 acres. The
site also includes a one acre scrap yard and several construction spoil areas. Across the site, there
are approximately two miles of rail access and one mile of paved roadways. The primary and
secondary ash settling basins have surface areas of approximately 41 and 28 acres, respectively.
Prior to construction of the ash settling basins, waste ash was disposed in the cinder pit, which
covers approximately 9 acres between the coal yard and ash basins.
Soils at RB are typical of the region and are predominantly micaceous sandy silts with some clay.
The topography is generally flat with some rolling hills in outlying, undeveloped areas.
There are 14storm water discharges and three NPDES permitted discharges at RB. Samples were
collected from outfalls SW001, SWO02 and SW003.
Facility Drainage and Inventory of Significant Materials and Controls
Stormwater
In the station area, stormwater runoff flows overland to concrete ditches and catch basins, which
are connected to a buried network of corrugated metal pipes (CMP). The network was originally
designed to route flow to several primary trunk lines, which flows into Mountain Island Lake.
Stormwater runoff from most areas subject to significant materials and activities has been
rerouted through either the yard sump or oil/water separator tanks. Effluent from the yard sump
is pumped to the ash settling basin. Stormwater processed through oil/water separators is
discharged to Mountain Island Lake. Station personnel routinely inspect the plant yard and
switchyards for potential spill sources. The intake and discharge canals, yard sump, and ash
basin are inspected dally for evidence of oil leakage.
Based on pipe networks and site topography, the Riverbend site was divided into individual
drainage basins as shown in the attached site drawings. This section details thirteen of fourteen
storm water outfalls (Outfall 9 has been abandoned). Also identified are three regions of
nonpoint source stormwater runoff that flow overland to Mountain Island Lake. Additional
outfalls may have been excluded because either they have been abandoned or because they are
not located within the vicinity of the station or any industrial activity. To provide a complete
description of the storm water drainage system, the yard sump system is also characterized.
A description of the drainage area, significant materials, and material control measures are
presented for each drainage basin. In addition to the significant materials particular to each
drainage basin, herbicides are applied to selected areas throughout Riverbend Steam Station to
eliminate undesirable vegetation along railways, ash pipelines, yard sump pipelines, and the

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 10 of 20
perimeter fence. Herbicides are also applied in switchyards, gravel lots, and rip -rap areas. All
herbicides used at Riverbend Steam Station are approved by the company and considered safe to
the environment when used according to directions. Records are retained at the site to document
information such as: the areas treated, the herbicide used and the amounts of herbicide used.
• Outfall1
Discharge Structure: 24 inch (") diameter () CMP
Location: Western bank of the intake canal
Control Structure: 10,000 gallon oil separator tank #3
Drainage Area: 4.1 acres
Area Description
This drainage basin includes a 2.7 acre portion of the main switchyard and 8,700 ft2 of the plant
yard between the powerhouse and Combustion Turbine (CT) area. The powerhouse covers about
1.5 acres of this drainage basin. 100 percent of the drainage area is paved or roofed.
Sijznificant Materials / Controls
Oil: Oil -cooled transformers and circuit breakers in the main switchyard contain a total of
approximately 120,000 gallons of oil. About two-thirds of the main switchyard falls within this
drainage area. Some switchgear equipment have containment pits beneath them. This substation
is inspected twice daily for fluid loss from switchgear equipment. All runoff from this drainage
basin is processed through the 10,000 gallon oil separator tank #3.
• Outfall2
Discharge Structure: 21" CMP
Location: Western bank of the intake canal
Control Structure: 10,000 gallon oil separator tank #2
Drainage Area: 13.6 acres
Area Description
This drainage area includes the 44 kV switchyard, a portion of the main switchyard, and the
circuit breakers for the 230 kV switchyard; these segments cover 0.4, 1.7, and 0.5 acres,
respectively. Two control buildings for the CTs are located within this basin. There is half an
acre of yard and parking area between the CT control rooms and the main switchyard. To the
south of the main switchyard, there are approximately six acres of lawn area. The railroad
embankment along the eastern basin boundary is sloped at a ratio of 1.5 horizontal to 1 vertical
(1.5H: 1V). The embankment and railways cover approximately 2.3 acres. To the east of the
railways is the fuel unloading area which covers about 0.9 acres. About one mile of railways and
one-third mile of paved roadways pass through the area. Approximately 35 percent of this
drainage basin is paved. All runoff from this drainage basin is processed through the 10,000
gallon oil separator tank #2. There is a vehicle rinse area within this basin, but the effluent is not
discharged through this outfall because it is routed to the ash basin through the septic system.
Significant Materials / Controls
Oil: The main switchyard, 44 kV switchyard, and 230 kV switchyard each contain a total
volume of 120,000, 10,000, and 6,700 gallons of mineral oil per switchyard, respectively. The
main switchyard and the 230 kV switchyard are only partially located within this basin. Some
switchgear equipment have containment pits beneath them. The main switchyard and the 44 kV
switchyard are inspected twice daily for fluid loss from switchgear equipment.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 11 of 20
There are two 18,000 gallon storage tanks in the main switchyard. These tanks have been closed
out and labeled "out of service." Transformers in the CT area contain 9,559 gallons of mineral
oil. Each CT unit contains about 400 gallons of oil.
If maintenance were necessary for the CTs, lube oil would be transferred from the units via a
tanker truck to a holding tank located in drainage basin #6.
The fuel oil unloading area is located along the eastern basin boundary, beside the railways. Two
of the ten bays are operable. In the fuel oil unloading area, diesel fuel is transferred from an
8,000 gallon tanker truck to an underground pipeline which flows to the 4,250,000 gallon fuel oil
bulk storage tank located south of the CTs. The pipeline is equipped with a back flow preventer.
DOT unloading procedures are followed. Drainage from the fuel oil unloading area is processed
through a 30,000 gallon oil separator tank located at the base of the railroad embankment, on the
south side of the plant access road. Storm water exits the oil/water separator tank by way of a 12
inch diameter concrete pipe which discharges into a concrete ditch. The ditch leads to a CMP
network that leads to the 10,000 gallon oil separator tank #2.
• Outfall3
Discharge Structure: 36" CMP
Location: Western bank of the intake canal
Drainage Area: 15.4 acres
Area Description
This drainage area includes approximately one-half acre of the containment dike slopes at the
fuel oil bulk storage tank. Approximately ten acres of lawn area border the plant access road.
Drainage from the three acre, 230 kV switchyard is discharged into a concrete ditch which leads
to this outfall. About 900 feet of paved access road and 800 feet of railways border this area.
Approximately 5 percent of this drainage basin is paved.
Significant Materials / Controls
Oil: The fuel oil bulk storage tank is an aboveground, galvanized steel cylinder surrounded by
an earthen berm sufficient in height to contain a total spill of 4,250,000 gallons plus rainfall.
Normally, the tank holds between 800,000 and 1,200,000 gallons of oil. Rainfall collected
within the containment berm is inspected for the presence of oil before being drained through a
manually operated siphon to Outfall 6.
Adjacent to the fuel oil bulk storage tank, about three feet of piping which conveys diesel fuel
from the fuel oil unloading area to the tank passes above grade over a concrete drainage ditch.
Switchgear equipment in the 230 kV yard contains approximately 6,700 gallons of oil. A 400
gallon oil rupture collection tank collects drainage from the two station service transformers
which contain a total of 226 gallons of mineral oil. Runoff from the 230 kV switchyard is
discharged into a concrete ditch running along the north side of the yard. The ditch passes under
the plant access road through a 36 inch diameter CMP. The west end of the CMP has a swing
gate which would be closed to help contain oil spillage from the switchyard.
• Outfall4
Discharge Structure: 15" RCP
Location: East of county road #1912
Drainage Area: 4.9 acres

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 12 of 20
Area Description
This drainage basin is bound on the west by the access road for the fuel oil unloading area and on
the east by county road #1912. Approximately 15 percent of the drainage basin is paved; the rest
is grass.
Significant Materials / Controls
Oil: A transformer for the fuel oil pumps is located within this basin, and it contains 482
gallons of mineral oil. A berm is installed around the transformer to contain any spills that could
occur.
The access road to the fuel oil unloading area forms the western boundary of this basin. The
tanker trucks which transport fuel oil have a capacity of 8,000 gallons.
• Outfall5
Discharge Structure: 24" CMP
Location: South of the 230 kV switchyard
Drainage Area: 3.5 acres
Area Description
This outfall conveys runoff off-site, beneath the plant access road to a drainage ditch along
county road #1912. Approximately eight percent of this drainage area is paved, and the rest is
grass.
Significant Materials / Controls
There are no significant materials stored within this area.
• Outfall6
Discharge Structure: 36" CMP
Location: Western bank of the intake canal
Control Structure: 20,000 gallon oil separator tank #1
Drainage Area: 5.4 acres
Area Description
This drainage area includes approximately 1.1 acres of the CT area. There are about three acres
of lawn areas, including the slopes of the containment dike for the fuel oil bulk storage tank. The
jet engine instrumentation house and warehouse are located within this drainage area.
Approximately 500 feet of paved roadway passes through the area. About 35 percent of the total
drainage area is either paved or roofed. All runoff from this drainage basin is processed through
the 20,000 gallon oil/water separator tank #1.
Significant Materials / Controls
Oil: The fuel oil bulk storage tank is an above ground, galvanized steel cylinder surrounded by
an earthen berm sufficient in height to contain a total spill of 4,250,000 gallons plus rainfall.
Normally, the tank holds between 800,000 and 1,200,000 gallons of oil. Rainfall collected
within the containment berm is inspected for the presence of oil before being drained through a
manually operated siphon to a concrete ditch at the base of the embankment. The ditch leads to
the #1 oil/water separator tank. Oil supply lines from the bulk storage tank to the CTs are
aboveground. There is a valve at the bulk fuel oil storage tank that would be manually closed in
the event of pipe leakage.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 13 of 20
Each CT unit contains approximately 400 gallons of oil.
• Outfall7
Discharge Structure: 24" steel pipe
Location: West of the coal pile
Drainage Area: 1.1 acres
Area Description
This drainage basin contains a lay -down yard where various scrap materials are stored.
Approximately 250 feet of gravel road pass through the area.
Significant Materials / Controls
There are no significant materials stored within this area.
• Outfall8
Discharge Structure: 36" CMP
Location: East of the yard sump, into Mountain Island Lake
Drainage Area: —65 acres
Area Description
Outfall 8 now encompasses the drainage area of outfall 9 since the influent to this outfall was
blocked. Outfall 8 previously drained 32.7 acres and Outfall 9 previously drained 26 acres. The
36" CMP, formerly known as Outfall 9, which is located north of the cinder pit and goes into
Mountain Island Lake, has been abandoned.
This drainage basin contains a 700,000 cubic feet ash stack and a closed out ash stack.
Approximately 6,150 feet of railways and 2,425 feet of gravel road are contained in Outfall 8.
Approximately 7 acres of woodlands are included within this basin. Approximately three percent
of this drainage basin is paved.
This drainage basin includes the cinder pit, which covers approximately nine acres to the east of
the coal yard. There is a one acre scrap yard adjacent to the cinder pit. Prior to construction of
the ash settling basins, ash was disposed in the cinder pit.
Rainfall runoff within this drainage basin flows to the cinder pit. The cinder pit is bermed along
its western and northern borders for containment purposes. The only outlet from the cinder pit is
a three foot tall CMP riser, making the cinder pit a very large detention pond. Discharge from
Outfall 8 is infrequent. Rainfall runoff in this drainage basin is usually detained in the cinder pit
and either evaporates into the atmosphere or infiltrates the ground.
Significant Materials
Oil: The transformer associated with the yard sump system contains 275 gallons of mineral oil
which is contained within a berm.
Ash: Parallel to the railroads, southeast of the cinder pit, ash is sluiced above grade in piping to
the ash basins.
Wastewater:
Parallel to the railroads, southeast of the cinder pit, effluent from the boiler room sumps is
pumped above grade in piping to the ash basins.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 14 of 20
Discharge from the yard sump is pumped to the ash basin through above grade pipelines located
atop the dike which forms the northern border of the drainage basin.
• Outfall 9 (Abandoned in place)
• Outfall 10
Discharge Structure: 18" CMP
Location: North of W.F. Lark Fossil Maintenance Facility
Drainage Area: 0.8 acres
Area Description
Outfall 10 discharges in the wooded area north of the W.F. Lark Fossil Maintenance Facility;
flow is then overland to Mountain Island Lake. This drainage basin includes approximately
6,000 square feet of roofed area and 7,000 square feet of paved storage area. There is about 250
feet of paved access road. Approximately 50 percent of this drainage basin is paved or roofed.
Significant Materials
There are no significant materials stored within this drainage area.
• Outfall 11
Discharge Structure: 18" CMP
Location: North of W.F. Lark Fossil Maintenance Facility
Drainage Area: 1.2 acres
Area Description
Outfall 11 discharges in the wooded area west of the W.F. Lark Fossil Maintenance Facility; flow
is then overland to a creek leading to Mountain Island Lake. This drainage basin includes
approximately 11,000 square feet of roofed area and 33,000 square feet of paved parking area.
There is about 250 feet of paved access road. Approximately 70 percent of this drainage basin is
paved or roofed.
Significant Materials
There are no significant materials stored within this drainage area.
• Outfall 12
Discharge Structure: 8" polyethylene pipe
Location: North of W.F Lark Fossil Maintenance Facility
Drainage Area: 3,000 square feet
Area Description
Outfall 12 discharges in the wooded area north of the W.F. Lark Fossil Maintenance Facility;
flow is then overland to Mountain Island Lake. This outfall conveys roof drainage from
approximately 3,000 square feet of roofed area. 100 percent of this drainage basin is roofed.
Significant Materials
There are no significant materials on the roof of Lark Fossil Maintenance Facility.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 15 of 20
• Outfall 13
Discharge Structure: 12" CMP
Location: Grassy area around septic tank/ Part of Area East of Intake Canal
Drainage Area: Approximately 400 square feet
Area Description
Outfall 13 discharges into Mountain Island Lake. Discharge is infrequent.
Significant Materials
There are no significant materials stored within this area.
• Outfall 14
Discharge Structure: 12" CMP
Location: Grassy area near road/ Part of Area East of Intake Canal
Drainage Area: Approximately 400 square feet
Area Description
Outfall 14 discharges into Mountain Island Lake. Discharge is infrequent.
Significant Materials
There are no significant materials stored within this area.
• Area West of Intake Canal
The rest of this area is a non -point source drainage area covering approximately 1.5 acres
between Outfalls 1 and 6. About one acre is paved parking and yard area. A trailer with roof
area of 1,800 ft2 is included within this area. Approximately 66 percent of this drainage area is
paved or roofed. Abandoned steam lines pass through this basin.
Significant Materials / Controls
There are no significant materials stored within this area.
• Area East of Intake Canal
This is a non -point source drainage area. The area covers approximately one acre extending from
the powerhouse up to the septic tank system. Roof area for the light -off oil tank and several
small sheds totals about 4,000 ft2. Approximately 15 percent of this drainage basin is paved or
roofed.
Significant Materials / Controls
Oil: Diesel fuel is piped above ground from the fuel oil bulk storage tank to the light -off oil
tank located adjacent to the powerhouse. The piping can be manually closed at the bulk fuel oil
storage tank, if necessary. The light off -tank has a capacity of 27,000 gallons and is surrounded
by a concrete containment pit capable of holding a total spill. The tank is covered to prevent
storm water collection.
• Area North of Drainage Basins 10 and 11
There are no catch basins in the northern half of the paved parking/storage area at W.F. Lark
Maintenance Facility, so runoff flows overland to Mountain Island Lake. This drainage area
covers approximately 1.5 acres extending from drainage areas 10 and 11 to the woods north of

Riverbend Steam Station, Gaston County
• NPDES Permit # NC0004961
Page 16 of 20
W.F. Lark Maintenance Facility. About 15,000 ft2 are roofed. Approximately 75 percent of this
drainage basin is paved or roofed.
Significant Materials / Controls
Various liquids such as coolants, oil, and cleaners are stored outside in 55 gallon drums. Usually,
a total of about 30 drums are stored under cover, in a shed.
Yard Sump Systems
There is one yard holding sump at Riverbend Steam Station.
• Yard Sump
The yard sump is located between the coal yard and cinder pit, on the north. The drainage basin
for the yard sump covers about 22 acres. Effluent from the yard sump is pumped to the ash basin
through a 30 inch diameter ductile iron pipe. Emergency overflow would go to Mountain Island
Lake via a 24 inch diameter CMP. This outfall is designated as NPDES Outfall 002a.
Area Description
Inflow to the yard sump is collected from the powerhouse, the plant yard, the coal yard, and the
septic tank system. Roof drainage comes from approximately 1.3 acres of the powerhouse roof.
From inside the powerhouse, discharge from turbine room sumps and floor drains is routed to the
yard sump. The plant yard covers about five acres and includes coal handling facilities,
warehouses, storage sheds, and the tractor maintenance house. These facilities have total roof
area of about one acre. The coal yard encompasses 13 acres, and runoff is routed to the yard
sump. There are approximately 2,900 feet of railways and 1,700 feet of paved/gravel roadways
within the basin. Paved and roofed areas represent about 25 percent of the drainage basin.
Significant Materials / Controls
Oil: PCB contaminated mineral oil collected from various Duke Energy locations is brought
to Riverbend and used as fuel within the plant. The mineral oil is transported in 6,000 gallon
tankers and transferred to the 20,000 gallon, used mineral oil tank for storage. During transfer
from the transport tanker to the storage tank, the truck parks within a bermed area. Transfer
guidelines stipulate that the drain within the bermed area must be covered during oil transfers.
Guidelines include procedures for prevention of oil spillage from the transfer hose and require
the transfer valve to be locked when not in use. The used mineral oil tank is located at the
northwest corner of the powerhouse. The steel tank is above grade and is surrounded by a
concrete containment pit capable of containing a total spill. The tank and pit are covered to
prevent storm water collection.
A smaller used oil tank with 2,000 gallons of storage capacity is located east of the paint and oil
warehouse. Used oil from miscellaneous plant and maintenance operations is pumped from 55
gallon drums into this tank. When the used oil tank is nearly full, the contents are transferred to a
transport tanker for off-site disposal. There is a steel containment pit beneath the tank which
would provide partial containment.
New and used oil is stored in 55 gallon drums throughout the plant. Drums are stored inside the
tractor maintenance building, coal handling facilities, the oil and paint warehouse, and in the
turbine floor. New oil drums are stored in a covered area outside the oil and paint warehouse,
and the floor slopes down towards the plant yard. A total of approximately 60 drums of used and

new oil are stored within this drainage area.
turbine floor.
Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 17 of 20
Oily waste is stored on the southeast end of the
There are three refueling stations for bulldozers, locomotives, and company vehicles. The fuel
line to the bulldozer and locomotive stations is enclosed within a PVC pipe, which drains to the
light -off tank containment pit. The locomotive refueling station is located directly over a
drainage ditch going to the yard sump. Gasoline is supplied to company vehicles from a 1,000
gallon underground storage tank.
A transformer associated with coal handling activities is located at the junction house and
contains 197 gallons of oil. Two transformers associated with the precipitators are located on the
north side of the powerhouse, and each contains 205 gallons of oil.
Chemicals:
A 750 gallon, sulfuric acid tank is located at the northeast corner of the powerhouse. The tank is
surrounded by an earthen berm. Both sulfuric acid and sodium hydroxide are unloaded in this
area. The 12,000 gallon sodium hydroxide tank is located in the basement of the powerhouse.
DOT procedures are followed during unloading.
Various chemicals are stored in 55 gallon drums throughout this drainage basin. A few drums
are stored in the tractor maintenance garage. These drums contain anti -freeze, cleaners and
Steam Jenny compound. Approximately 20 drums of oil are stored in the covered area outside
the oil and paint warehouse. Empty drums are stored outside the warehouse.
Hazardous Waste:
Hazardous wastes are placed in a satellite accumulation area in a small shed to the west of the oil
and paint warehouse. The floor of the shed is constructed to provide containment to a depth of
four inches which should be sufficient for the maximum volume of waste stored.
Wastewater:
Plant wastewater from equipment discharges, floor drains, sumps, etc. is routed to the yard sump.
If case an oil and/or chemical spill were to occur this spilled material will be captured and routed
to the yard sump. Liquid effluent from the septic tank system is routed to the yard sump.
Discharge from the yard sump is piped to the ash basin. Effluent from the boiler room sumps is
pumped above ground through this area to the ash basin.
Ash: Ash is sluiced in piping above grade through this drainage basin to the ash settling basin.
Hazardous and Toxic Substances
Hazardous and Toxic Substances Table 2c- 3
At RB, the potential for toxic and hazardous substances being discharged is very low. In
reference to Item V -D of Form 2-C, the substances identified under Table 2c-3 that may be in the
discharge are as follows: Acetaldehyde, Aniline, Asbestos, Benzoyl Chloride, Cresol,
Cyclohexane, Cyclohexanone, Formaldehyde, Styrene, Triethanolamine, Vanadium and
Zirconium.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 18 of 20
Other - During the course of the year products such as commercial cleaners and laboratory
reagents may be purchased which contain very low levels of a substance found in Table 2c-3. It
is not anticipated that these products will impact the ash basin's capacity to comply with its
toxicity limits, since their concentrations would be extremely low.
40 CFR 117 and CERCLA Hazardous Substances
The following table identifies hazardous substances located on-site that may be released to the
ash basin during a spill in quantities equal to or greater than the reportable quantity (RQ) levels
as referenced in 40 CFR 117, 302 and 355. This list is being provided in order to qualify for the
spill reportability exemption provided under 40 CFR 117 and the Comprehensive Environmental
Response Compensation and Liability Act (CERCLA). These values below represent the
maximum quantities on-site that could be released at one time and sent to the ash basin. They do
not reflect quantities that may be discharged through typical use.
Substance Quantity (lbs.) Source
Calcium Hypochlorite 32.5 Warehouse
Hydrazine 750 Warehouse
Sodium hydroxide 18,765 Tank
Sulfuric Acid 5,004 Bulk Storage Tank
Riverbend Steam Station 316(a) Determination
Duke Energy's operating experience during the past five years under the thermal limitations
imposed in NPDES Permit No. NC#0004961 substantiates EPA's 316(a) determination (May
1975) for Riverbend that the "thermal component of the discharge assures the protection and
propagation of shellfish, fish and wildlife in and on the receiving body of water."
In Duke's judgment the operating characteristics of the station have a minimal effect on the
aquatic environment of Mountain Island Lake. The character of the thermal discharge has not
changed since the original 316(a) determination. Accordingly, Duke requests that the thermal
limitations as modified in the present permit be continued.
Riverbend Steam Station 316 (b) Review
In conjunction with the rulemaking process for the new Phase II 316(b) rule pertaining to fish
impingement and entrainment, historical data and permitting records were reviewed. Initial
316(a) and 316(b) studies associated with enactment of the Clean Water Act concluded that the
location, construction capacity, and design of the cooling water intake were not detrimental to the
aquatic ecosystem and minimize adverse environmental impacts. Both North Carolina and EPA
regulators concurred in 1976 that 316(b) fish impingement and entrainment studies were no
longer needed at that time. Currently the Phase II 316(b) rule for existing facilities that was
remanded will be rewrittenby EPA and is expected to be published for public comment in 2009
or 2010.

Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 19 of 20
Ash Basin Capacity
Part II.A(8.) of the existing NPDES permit requires the permittee to provide and maintain at all
times a minimum free water volume (between the top of the sediment level and the minimum
discharge elevation) equivalent to the sum of the maximum 24 hour plant discharges plus all
direct rainfall and all runoff flows to the pond resulting from a 10 year, 24 hour rainfall event,
when using a runoff coefficient of 1.0.
Determination of Wet Weather Detention Volume: Wet Weather Detention Volume is the sum of the
runoff accumulated in the ash basin which results from a 10 -yr 24 -hr storm (assuming 100% runoff)
plus the maximum 24 -hr dry weather waste stream which discharges to the Ash Basin (refer to
NPDES Permit NC0004961)
I
II.
Estimate Runoff to the Ash Basin from a 10 -yr 24 -hr storm:
1. Natural Drainage Area of Ash Basin =
Station Yard Drainage Area Pumped to Ash Basin =
Total =
2. Precipitation from 10 -yr 24 -hr storm =
3. Total Stormwater Runoff to Ash Basin =
(Assuming 100%
runoff)
Estimated Maximum 24 -hr Dry Weather Waste Stream Discharging to Ash Basin:
Maximum recorded Ash Basin Discharge =
2. Increase maximum daily disharge by 10% for
conservatism and convert units to acre-feet =
Wet Weather Detention Volume:
Sum of Parts I. and II. =
98.7 Acres
21.8 Acres
120.5 Acres
5.0 Inches
50.21 Acre-feet
10,660,000 Gallons/da
35.98 Acre-feet
86.19 Acre-feet

IV
Riverbend Steam Station, Gaston County
NPDES Permit # NC0004961
Page 20 of 20
Estimated Quantity of Solids (Ash) to be discharged to Ash Basin through December 31, 2015.
Note: NPDES Permit expiration date is 2/28/10.
* Calculation assumes an in-place ash density of 55 lbs. per cubic foot.
* Estimated volumes and weights taken from 2009 CCP Ten Year Plan, Regulated
V. Estimated Total Storage Volume Required through 2015:
Wet Weather Detention Volume =
Estimated Solids to Ash Basin =
Total =
VI. Results:
Primary Cell
Secondary Cell
2007-2008 Ash Removal Project
Estimated Solids to Basin Oct. 2005 - Dec. 2008
Total
Note: Available Storage based on basin survey dated 9/28/2005
Required Storage Volume Through 12/31/2015:
86.2 Acre-feet
309.0 Acre-feet
395.1 Acre-feet
132.6 Acre-feet
369.6 Acre-feet
393.6 Acre-feet
328.6 Acre-feet
567.1 Acre-feet
395.1 Acre-feet
Based on these calculations, there is sufficient capacity in the ash basin to provide the
retention volume specified in the permit through the year 2015.
Actual or
Estimated
Estimated
Estimated
Coal
Ash
Ash
Consumption
Production
Production
Time Period
1000's tons
% Ash
1000's tons
Ac -ft
2009
372.4
11.60%
43.20
36.07
2010
574.8
12.10%
69.55
58.06
2011
679.7
11.90%
80.89
67.52
2012
574.3
11.80%
67.77
56.57
2013
452.8
10.90%
49.36
41.20
2014
477.7
10.90%
52.07
43.47
2015
1 463.0
10.90%
50.46
42.13
Total
3222.32
370.10
308.95
* Calculation assumes an in-place ash density of 55 lbs. per cubic foot.
* Estimated volumes and weights taken from 2009 CCP Ten Year Plan, Regulated
V. Estimated Total Storage Volume Required through 2015:
Wet Weather Detention Volume =
Estimated Solids to Ash Basin =
Total =
VI. Results:
Primary Cell
Secondary Cell
2007-2008 Ash Removal Project
Estimated Solids to Basin Oct. 2005 - Dec. 2008
Total
Note: Available Storage based on basin survey dated 9/28/2005
Required Storage Volume Through 12/31/2015:
86.2 Acre-feet
309.0 Acre-feet
395.1 Acre-feet
132.6 Acre-feet
369.6 Acre-feet
393.6 Acre-feet
328.6 Acre-feet
567.1 Acre-feet
395.1 Acre-feet
Based on these calculations, there is sufficient capacity in the ash basin to provide the
retention volume specified in the permit through the year 2015.