NC0004961_Permit Modification_19961028

,State of North Carolina
Department of Environment,
Health and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Jonathan B. Howes, Secretary
A. Preston Howard, Jr., P.E., Director
A40
— V
C)EHNR
October 28, 1996
Mr. John S. Carter
Duke Power Company
13339 Hagers Ferry Road
Huntersville, North Carolina 28078-7929
Subject: Permit Modification
NPDES Permit NC0004961
Riverbend Steam Station
Gaston County
Dear Mr. Carter:
This letter responds to your August 30, 1996 letter requesting changes to permit NC0004961 to
correct errors made in the permit. On the Effluent Limitations and Monitoring Requirements for outfall
001: In footnote 2, the spelling of "must" has been corrected. On the Effluent Limitations and Monitoring
Requirements for outfall. 002: the monitoring frequency for flow has been changed from daily to weekly.
This letter also addresses the relocation of the downstream temperature monitoring station for
Riverbend Steam Station from the forebay to the tailrace of Mountain Island Lake Dam. Bob Caccia (Duke
Power) has discussed this relocation with Paul Clark of our staff. According to their conversations, the
temperature monitoring method used at the tailrace location will be different than the method used at the
forebay location. Specifically, a thermister will monitor temperature and will transmit data electronically to
Duke's main database computer system. The Division has some concern with thermister calibration.
The thermister location will be in the vicinity of a Hydrolab multi -parameter unit used to collect
data for relicensing the facility. It is understood that the Hydrolab unit will collect data similar to that of
the thermister. Thermister data will adequately meet Duke Power's compliance requirements and Duke
Power will not be required to report the Hydrolab data for compliance purposes. However, the Division
requests that the Hydrolab data be sent to the NPDES Permits Group for informational purposes.
Bob Caccia agreed that Duke Power would include a cover letter with their DMR submittal
confirming the new downstream monitoring location and the use of new monitoring equipment. This
submittal would also include more detailed information on the new monitoring equipment. The Division
requests that thermister calibration information be included with the submittal.
Please find enclosed the modified sections of the permit referenced in the preceding paragraph.
Replace the original sections in your permit with the newer enclosed sections and discard the original
sections. All other terms and conditions contained in the original permit remain unchanged and in full
effect. These permit modifications are issued pursuant to the requirements of North Carolina General
Statutes 143-215.1 and the Memorandum of Agreement Between North Carolina and the U.S.
Environmental Protection Agency.
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post -consumer paper

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Mr. Carter
$est 28, 1996
Page 2
If any parts, measurement frequencies or sampling requirements contained in this permit
modification are unacceptable to you, you have the right to an adjudicatory hearing upon written request
within thirty (30) days following receipt of this letter. This request must be in the form of a written
petition, conforming to Chapter 150B of the North Carolina General Statutes, an filed with the Office of
Administrative Hearings, Post Office Drawer 27447, Raleigh, North Carolina 27611-7447. Unless such
demand is made this decision shall be final and binding.
If you have any questions, please contact Paul B. Clark at [phone] extension 580.
Sincerely,
/�w �- 4
111-�-
Preston Howard,
Enclosures
cc: Central Files
Mooresville Regional Office, Water Quality Section
Roosevelt Childress, EPA
Permits and Engineering Unit (Permit Files)
Facility Assessment Unit
r., P.E.

A. (1). EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS Permit No. NC0004961 V
During the period beginning on the effective date of the permit and lasting until expiration, the Permittee is authorized to discharge from
outfall(s) serial number 001. Such discharges shall be limited and monitored by the Permittee as specified below:
Effluent Characteristics Discharge Limitations Monitoring Requirements
Measurement Sample Sample
Monthly Avg. Weekly Avg. Daily Avg. Frequency Type Location 1
Flow Daily Pump Logs I or E
Temperature' C (° F) 35 (95) Daily Grab E
Temperature ° C (° F) 2 32 (89.6) Daily Grab D
Temperature 3 Daily Grab I, E
Footnotes:
1 Sample locations: E - Effluent, I - Intake, D- Downstream at Mountain Island Lake Dam.
2 The ambient temperature shall not exceed 32.0° C (89.6° F), and is defined as the daily average downstream water temperature. When the Riverbend
Station effluent temperature is recorded below 32.0° C (89.6° F), as a daily average, then monitoring and reporting of the downstream water
temperature is not required. In cases where the Permittee experiences equipment problems and is unable to obtain daily temperatures from the existing
temperature monitoring system, the temperature monitoring must be reestablished within five working days.
3 This temperature requirement in effect when only units with a shared control system are operating.
1. If the daily average intake temperature is below 2.5° C (36.5° F), the daily average effluent temperature shall not exceed 10° C (50° F), and
2. If the daily average intake temperature ranges from 2.5° C (36.5° F) to 12.8° C (55° F), the daily average effluent temperature shall not exceed two
times the intake temperature (° F) minus 23.
Chlorination of the once through cooling water shall not be allowed at this facility. Should Duke Power wish to chlorinate its once through cooling water,
a permit modification must be requested prior to commencing chlorination.
The Regional Administrator has determined pursuant to Section 316 (a) of the Act that the thermal component of the discharge assures the protection and
propagation of a balanced, indigenous population of shellfish, fish, and wildlife in the receiving body of water.
There shall be no discharge of floating solids or visible foam in other than trace amounts.
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A. (2). EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS Permit No. NC0004961 1
During the period beginning on the effective date of the permit and lasting until expiration, the Permittee is authorized to discharge from
outfall(s) serial number 002. Such discharges shall be limited and monitored by the Permittee as specified below:
Effluent Characteristics
Flow
Total Suspended Solids 2
Oil and Grease
Total Copper
Total Iron
Total Arsenic
Total Selenium
Total Nitrogen (NO2+NO3+TKN)
Taal Phosphorus
Chronic Toxicity 3
Footnotes:
Discharge Limitations
Monthly Avg. Weekly Avg. Daily Max.
1 Sample locations: E - Effluent, I - Intake.
23.0 mg/1
11.0 mg/l
1.0 mg/l
1.0 mg/1
75.0 mg/1
15.0 mg/1
1.0 mg/1
1.0 mg/1
Monitorins Reauirements
Measurement
Sample
Sample
Frequency
Tyne
Location 1
Weekly
PumpLogs/Est I or E
2/month
Grab
E
Monthly
Grab
E
2/month
Grab
E
2/month
Grab
E
Monthly
Grab
E
Monthly
Grab
E
Quarterly
Grab
E
Quarterly
Grab
E
Quarterly
Grab
E
2 Monthly average of 43 mg/1 is permitted provided that the Permittee can satisfactorily demonstrate that the difference between 23 mg/1 and 43 mg/1 is a
result of the concentration of total suspended solids in the intake water.
3 Chronic Toxicity (Ceriodaphnia) P/F at 10%; January, April, July, October; See Part III, Condition J.
The metal cleaning waste, coal pile runoff, ash transport water, domestic wastewater, and low volume waste shall be discharged into the ash settling
pond.
The pH shall not be less than 6.0 standard units nor greater than 9.0 standard units and shall monitored 2/month at the effluent by grab sample.
There shall be no discharge of floating solids or visible foam in other thafi trach amounts.
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