NC0004979_Minor Modification_20080908

Michael F. Easley, Governor
otfl pG State of North Carolina
William G. Ross, Jr., Secretary
t— Department of Environment and Natural Resources
O.0 Coleen H. Sullins, Director
Division of Water Quality
September 8, 2008
Mr. Michael Ruhe
Duke Energy Corporation
P.O. Box 1006
Mail Code EC11E
Charlotte, North Carolina 28201
Subject: NPDES Minor Modification
Permit No. NC0004979
Allen Steam Station
Gaston County
Dear Mr. Ruhe:
The subject individual NPDES permit issued on September 11, 2006 has been modified as per your
request. Please find attached the modified,sections of -this permit, and replace the old pages with the
modified pages. This permit modification is issued pursuant to the requirements of North Carolina
General Statute 143-215.1 and the Memorandum of Agreement between North Carolina and the U.S.
Environmental Protection Agency dated December 6, 1983 (and as subsequently amended).
The following permit modification is authorized by this letter:
• Duke Energy is authorized to route landfill leachate to the existing ash basin wastewater
treatment system. This.minor modification is necessary so that Duke may change from its
current ash sluicing operation to a dry ash handling system, which is expected to reduce
overall pollutant loading to the ash pond.
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, and filed with the office of
Administrative Hearings, Post Office Drawer 27447, Raleigh, North Carolina 27611-7447. Unless such a
demand is made, this permit shall be final and binding.
This permit does not affect the legal requirements to obtain other permits which may be required by the
Division of Water Quality or permits required by the Division of Land Resources, Coastal Area
Management Act, or any other Federal or Local governmental permits may be required.
If you have any questions or need additional information, please contact Toya Fields, telephone number
[phone].
Sincere
?Zoeen ullins
cc: NPDES File
Central Files
Mooresville Regional Office, Water Quality
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone [phone] FAX [phone] NoRhCarolina
512 N. Salisbury Street, Raleigh, North Carolina 27604 On the Internet at http://www.ncwaterquality.org Naturally
An Equal Opportunity/Affirmative Action Employer

Permit NC0004979
SUPPLEMENT TO PERMIT COVER SHEET
All previous NPDES Permits issued to this facility, whether for operation or discharge are hereby revoked. As of
this permit issuance, any previously issued permit bearing this number is no longer effective. Therefore, the
exclusive authority to operate and discharge from this facility arises under the permit conditions, requirements,
terms, and provisions included herein.
Duke Energy Corporation is hereby authorized to:
1. Continue to discharge:
• Once through cooling water (outfall 001)
• Operate a septic tank and ash pond with pH adjustment and discharge domestic
wastewater, stormwater runoff, ash sluice, water treatment system wastewaters, FGD
system blowdown, landfill leachate, and miscellaneous cleaning and maintenance
wash waters (002).
• Coal yard sump overflow (002A) and power house sump overflow (002B)
• Miscellaneous equipment non -contact cooling and sealing water (003)
• Miscellaneous non -contact cooling water, vehicle washwater, and intake screen
backwash (004)
From a facility located at the Plant Allen Steam Station on Plant Allen Road (NCSR 2525),
south of Belmont in Gaston County, and
2. Without adding detergents or chemicals of any kind, discharge Asiatic clam/debris filter
backwash (of the intake filter screen) (see Part A.7); and
3. After receiving an Authorization to Construct from the Construction Grants and Loans
Section, construct and operate a FGD wet scrubber wastewater treatment system discharging
to the ash settling basin through internal outfall 005; and
4. Discharge from said treatment works at the location specified on the attached map into the
Catawba River (outfalls 002, 002A, 002B and 004) and the South Fork Catawba River (outfalls
001 and 003) which are classified Class WS -V B waters, respectively, in the Catawba River
Basin.
14

Allen Steam Station -Minor NPDES Permit Modification Request
Subject: Allen Steam Station - Minor NPDES Permit Modification Request
From: "Stowe, Allen" <j astowe @ duke-energy.com>
Date: Thu, 14 Aug 2008 09:59:41 -0400
To: "Toya Fields" <[e-mail]>
Toya,
Please review the two attached tables. Table 2 illustrates how the concentration values used in the calculations
highlighted in Table 3 were determined. Table 3 estimates the proposed wastewater quality at the ash basin
discharge (for various flow scenarios) when the leachate from the proposed ash landfill is introduced. Please note
that these calculations are extremely conservative because they assume the same level of loading from the ash
basin after the conversion to dry ash handling. I have compared this information with the DMR and Form 2C data.
Based on this review, it doesn't appear that these results should result in any new permit limits or more stringent
current limits. This is because the estimated leachate volume is very small in relation to the ash basin discharge
volume. Please refer to the sample calculation at footnote (5) on Table 3.
Please review this information and let me know if the Allen Steam Station NPDES permit can be modified to
incorporate leachate from the proposed ash landfill. Also, do I need to formally submit these tables to you by
means of a hard copy and a cover letter? Please advise. If you need additional information, don't hesitate to
contact me. Thanks
Allen Stowe
Office [phone]
Cell [phone]
Wastewater Characterization 081208.pdf
Allen Wastewater
Content -Description: Characterization
081208.pdf
Content -Type: application/octet-stream
Content -Encoding: base64
1 of 1 8/21/2008 2:28 PM

TABLE 2
SPLP-TCLP RESULTS PROVIDED BY DUKE ENERGY
DUKE ENERGY - ALLEN STEAM STATION *S&ME
S&ME Project No. 1356-06-825
All concentrations in micrograms per liter (Ng/1): NA Not Analyzed
Ash and Sludge samples analyzed by SPLP (except for the Ash Mercury -Hg analysis).
The Ash Hg results (samples from 2004-2005) for SPLP analyses were reported as less than 0.001 and 0.005
pg/L. Alternative leaching tests with varying pH values indicated values of 0.01 pg/L, which is used above.
Gypsum analyzed by TCLP. BRL - Below Reporting Limits.
Ash samples from Plant Allen, May 22, 2008 (except for mercury as noted above).
Gypsum samples from Plant Marshall, February 4, 2008.
Clarifier sludge from Belews Creek, April 30 and May 19, 2008 (Highest values provided above).
All samples represent closest approximation to Plant Allen waste stream.
S:\1356\PROJECTS\2006\1356-06-825 Duke Power -Allen Steam Station Ash Landfill\Permit (To Construct) Application\ATC DWQ NDPDES Permitting\RAB
Leachate -Pond Discharge Calcs Final 08.08.08.xis, Tab 2 for report
Parameter
Ash
Gypsum
Clarifier
Sludge
Sludge Value
used in Calc
Max.
Conc.
Total with
95% Ash
5% Sludge
Parameters with current NPDES Dischar a Limits
u
Co er
130
NA
< 10.0
10
130
<124
e
Vr
Iron
254
NA
249
249
254
254
e
Selenium 1
15.6 1
BRL
44
44
44
17.02
Parameters without current NPDES Discharge Limits
s
Arsenic
11.6
BRL
20.5
20.5
20.5
12.0
Boron
1,320
NA
32,400
32,400
32,400
1942
d
Cadmium
3.9
BRL
< 1.0
1
3.9
<3.8
Chloride
28,600
NA
222,000
222,000
222,000
38270
Or
Chromium
11.7
BRL
< 5.0
5
11.7
<11.6
Fluoride
2,980
NA
6,920
6,920
6,920
3,177
Tra
Mercury
0.01
BRL
< 1.0
1
< 1.0
<0.0595
Manganese
1,130
NA
< 150
150
1,130
<1081
Ni.
Nickel
1,410
NA
< 10.0
10
1,410
<1340
Pb-
Lead
< 5.0
BRL
< 5.0
5
< 5.0
<5
LS041
Sulfate
139,000
NA
1,550,000
1,550,000
1,550,000
209,550
All concentrations in micrograms per liter (Ng/1): NA Not Analyzed
Ash and Sludge samples analyzed by SPLP (except for the Ash Mercury -Hg analysis).
The Ash Hg results (samples from 2004-2005) for SPLP analyses were reported as less than 0.001 and 0.005
pg/L. Alternative leaching tests with varying pH values indicated values of 0.01 pg/L, which is used above.
Gypsum analyzed by TCLP. BRL - Below Reporting Limits.
Ash samples from Plant Allen, May 22, 2008 (except for mercury as noted above).
Gypsum samples from Plant Marshall, February 4, 2008.
Clarifier sludge from Belews Creek, April 30 and May 19, 2008 (Highest values provided above).
All samples represent closest approximation to Plant Allen waste stream.
S:\1356\PROJECTS\2006\1356-06-825 Duke Power -Allen Steam Station Ash Landfill\Permit (To Construct) Application\ATC DWQ NDPDES Permitting\RAB
Leachate -Pond Discharge Calcs Final 08.08.08.xis, Tab 2 for report

TABLE 3 *S&ME
PROJECTED ACTIVE ASH BASIN DISCHARGE CALCULATIONS
DUKE ENERGY - ALLEN STEAM STATION
&ME Project No. 1356-06-825
Notes:
(1) Estimated leachate flow rate is a maximum flow rate calculated during design modeling performed by S&ME
(2) Average and Maximum Pond Flow from Duke Energy monthly monitoring 2005-2007
(3) Estimated concentrations from SPLP analyses of Ash and Clarifier Sludge and TCLP analysis of Gypsum. All
Gypsum results were below reporting limits. Estimated Leachate Concentrations based on 95% Ash and 5%
Clarifier Sludge Results.
(4) Ash Basin concentrations from June 26, 2008 sample
(5) Example Calculation, Sulfate: (209.,550 x 0.26%) + (65,000 x 99.74%) = 65,190
pg/L: micrograms per liter
gpd: gallons per day
S:\1356\PROJECTS\2006\1356-06-825 Duke Power -Allen Steam Station Ash Landfill\Permit (To Construct) Applicalion\ATC DWQ NDPDES Permitting\RAB Leachate -Pond Discharge Calcs Final 08.08.08.x1s, Tab 3 for report
Estimated
Leachate (1)
d
Average Ash
Basin (2)
d
Avg. Estimated
Total Flow
d
Estimated
Leachate (1)
d
Maximum Ash
Basin (2)
d
Max Estimated
Total Flow
d
Flow Rate
25,097
19,100,000
19,125,097
25,097
24,500,000
24,525,097
Percentage
0.13%
99.87%
100%
0.10%
.99.90%
100%
50% Ash Pond Flow Rate
25,097
9,550,000
9,575,097
25,097
12,250,000
12,275,097
Percentage
0.26%
99.74%
100%
0.20%
99.80%
100%
Notes:
(1) Estimated leachate flow rate is a maximum flow rate calculated during design modeling performed by S&ME
(2) Average and Maximum Pond Flow from Duke Energy monthly monitoring 2005-2007
(3) Estimated concentrations from SPLP analyses of Ash and Clarifier Sludge and TCLP analysis of Gypsum. All
Gypsum results were below reporting limits. Estimated Leachate Concentrations based on 95% Ash and 5%
Clarifier Sludge Results.
(4) Ash Basin concentrations from June 26, 2008 sample
(5) Example Calculation, Sulfate: (209.,550 x 0.26%) + (65,000 x 99.74%) = 65,190
pg/L: micrograms per liter
gpd: gallons per day
S:\1356\PROJECTS\2006\1356-06-825 Duke Power -Allen Steam Station Ash Landfill\Permit (To Construct) Applicalion\ATC DWQ NDPDES Permitting\RAB Leachate -Pond Discharge Calcs Final 08.08.08.x1s, Tab 3 for report
Parameter
Estimated
Leachate
Concentration (3)
(ug/L)
Ash Basin
Concentration (4)
(Ng/L)
Ave Flow
Projected
Discharge
Concentration (5)
(Ng/L)
Max Flow
Projected
Discharge
Concentration
(ug/L)
50% Ave Flow
Projected
Discharge
Concentration
(Ng/L)
50% Max Flow
Projected
Discharge
Concentration
(u9/L)
Parameters with current NPDES Discharge Limits
Cu
lCopper
1 <124
18
<18
<18
<18
<18
Fe
Ilron
1 254
143
143
143
143
143
Se
ISelenium
1 17
4.05
4.07
4.06
4.08
4.08
Parameters without current NPDES Discharge Limits
As
Arsenic
12
3.34
3.35
3.35
3.36
3.36
B
Boron
1,942
324
326
326
328
327
Cd
Cadmium
<3.84
0.84
<0.84
<0.84
<0.85
<0.85
Cl
Chloride
38,270
27,000
27,015
27,012
27,030
27,023
Cr
Chromium
<11.6
<1.0
<1.0
<1.0
<1.0
<1.0
F
Fluoride
3,177
<10,000
<9,991
<9,993
<9,982
<9,986
Hq
Mercury
<0.06
0.0013
<0.0014
<0.0014
<0.0015
<0.0014'
Mn
Manganese
<1,081
119
<120
<120
<122 1
<121
Ni
Nickel
<1,340
32.5
<34.2 1
<33.8
<35.9
<35.2
Pb
Lead
<5
<2
<2
<2
<2
<2
SO4
Sulfate
209,550
65,000
65,190
65,148
65,379
65,296
Notes:
(1) Estimated leachate flow rate is a maximum flow rate calculated during design modeling performed by S&ME
(2) Average and Maximum Pond Flow from Duke Energy monthly monitoring 2005-2007
(3) Estimated concentrations from SPLP analyses of Ash and Clarifier Sludge and TCLP analysis of Gypsum. All
Gypsum results were below reporting limits. Estimated Leachate Concentrations based on 95% Ash and 5%
Clarifier Sludge Results.
(4) Ash Basin concentrations from June 26, 2008 sample
(5) Example Calculation, Sulfate: (209.,550 x 0.26%) + (65,000 x 99.74%) = 65,190
pg/L: micrograms per liter
gpd: gallons per day
S:\1356\PROJECTS\2006\1356-06-825 Duke Power -Allen Steam Station Ash Landfill\Permit (To Construct) Applicalion\ATC DWQ NDPDES Permitting\RAB Leachate -Pond Discharge Calcs Final 08.08.08.x1s, Tab 3 for report

Re: FW: Duke Energy/Allen Steam Station- NPDES •Permit Modification
Subject: Re: FW: Duke Energy/Allen Steam Station- NPDES Permit Modification
From: "Stowe, Jimmie A Jr" <[e-mail]>
Date: Tue, 10 Jun 2008 10:30:06 -0400
To: <[e-mail]>
Toya, thanks for the quick response. Would it be OK to pursue the minor first so that landfill construction can begin
and work on the major mod later with a separate request?
Allen Stowe - sent using Blackberry
704-516-5548
----- Original Message -----
From: Toya Fields <[e-mail]>
To: Hallman, Christopher D
Cc: Manes, Theodore A; Kenneth Daly <[e-mail]>; Wylie, Robert R; Stowe, Jimmie A Jr; Nispel,
Debbie; Scruggs, Donald L
Sent: Mon Jun 09 16:59:18 2008
Subject: Re: FW: Duke Energy/Allen Steam Station- NPDES Permit Modification
Thanks Allen,
Since the leachate wastewater won't change the characteristics of the ash pond discharge, it could be considered a
minor modification, but you are going to have to request a major modification to have the selenium reduced. My
thoughts are that you might as well send in a formal major modification request for all of this together. After you
send it in, it will be assigned to a permit writer and we can get moving on both issues. Since it will be a major
modification it will need to go through the 30 day public notice.
Toya
Hallman, Christopher D wrote:
Information forwarded for Allen Stowe.
From: Stowe, Jimmie A Jr
Sent: Friday, June 06, 2008 7:52 PM
To: Hallman, Christopher D; Manes, Theodore A; Kenneth Daly
Subject: RE: Duke Energy/Allen Steam Station- NPDES Permit Modification
Toya,
1 of 4 .9/8/2008 10:19 AM

Re: FW: Duke Energy/Allen Steam Station- NPDES Permit Modification
Hopefully I now have some of the information that you have requested. I have attached a report compiled by
S&ME. This report calculates copper, iron, and selenium NPDES discharge concentrations at the Allen ash basin
based on leachate from the projected landfill. These calculations are based on the projected volume of the leachate,
actual leachate concentration from Allen dry ash, and the actual ash basin flow at Allen. The discharge
concentrations based on leachate conservatively assume the same mass loading as the current ash sluicing
operations. Empirical data at other Duke stations that are now disposing of this waste stream (i.e. the flyash/FGD
scrubber sludge/gypsum mixture) in synthetic lined landfills have demonstrated a reduction in overall loading to the
ash basin. The purpose of this study is to illustrate that even when higher than expected mass loading is assumed,
the result is that there is no increase of these pollutants in the wastewater at the NPDES outfall. Allen Steam Station
is converting to a dry ash handling system and this leachate would be managed in the existing ash basin wastewater
treatment system. The proposed landfill would be a state-of-the-art landfill with a double synthetic liner and
leachate collection system. The clarifier sludge was obtained from the Belews Creek FGD wastewater treatment
system. Allen Steam Station is expected to employ a similar wastewater treatment technology as Belews Creek
Steam Station.
I have also attached two spreadsheets that lists selenium concentrations over the last five years. Please note
that in 2004, selenium treatment in the ash basin was refined. As a result of these modifications, selenium
concentrations at the ash basin discharge have been significantly reduced over the last 3-4 years. The leachate from
the dry ash landfill will be also treated in the ash basin as well (see Figure 1).
Based on this information; Duke Energy makes two requests:
1) The selenium limit for the ash basin discharge be recalculated based on DMR data from the past three
years, and
2) Allow the construction of the proposed synthetically lined dry ash landfill without a NPDES permit
modification. This request is based on the rationale that the wastewater treatment system (i.e. the Allen ash basin) is
not being altered to treat the landfill leachate. The only difference is that majority of the pollutants will be conveyed
to the ash basin as landfill leachate rather than the ash sluice system.
I wanted you to receive this information as soon as possible. If I need to follow-up with a more formal hard
copy submittal, please let me know. Since we are in need of a timely decision on this matter; please don't hesitate to
contact me via cell phone [phone]) if I can be of any assistance.
Thanks for your efforts on our behalf.
Allen Stowe
Office [phone]
Cell [phone]
2 of 4 9/8/2008 10:19 AM

Re: FW: Duke Energy/Allen Steam Station- NPDES Permit Modification
From: Toya Fields [mailto:[e-mail]]
Sent: Thursday, April 24, 2008 2:10 PM
To: Stowe, Jimmie A Jr
Cc: Hallman, Christopher D; Manes, Theodore A; Scruggs, Donald L; [e-mail]
Subject: Re: Duke Energy/Allen Steam Station- NPDES Permit Modification
Hi Jimmie,
I think our phone system may finally be back up but I have heard some murmurs of difficulties this morning.
I'd need more information about the characteristics of the leachate before I could give you a good answer. How
does it compare to the ash slurry going to the ash pond? Do you have any information on the expected constituents
and concentrations? What about an estimated discharge volume? If its very similar to the existing ash slurry then it
could very well be a minor mod. However if its very different or very concentrated then it may not be.
Toya
Stowe, Jimmie A Jr wrote:
Toya,
I tried to call you but it seems like your office telephone isn't functioning properly.
We have submitted an application to construct a synthetically lined landfill at Allen Steam Station (NPDES
#NC0004979) to the NC DENR Solid Waste Section. The construction of this landfill was not mentioned in the
most recent NPDES modification. Once this landfill is constructed and placed into operation, the leachate will be
collected in a sump and routed to the station's ash basin for treatment. Will this activity be considered a major or
minor NPDES modification? What information do you need to process the NPDES modification?
The current plan is to begin landfill construction once the application is approved by the Solid Waste Section,
which is expected within the next 1-2 months.
Please call me at 704-516-5548 to discuss. Thanks for your help.
Allen Stowe
Office [phone]
Cell [phone]
3 of 4 9/8/2008 10:19 AM

Re: FW: Duke Energy/Allen Steam Station- NPDES Permit Modification
Toya Fields - [e-mail]
Environmental Engineer I
Western NPDES Program
Division of Water Quality
Tel: [phone] x 551
Fax: [phone]
Toya Fields - toya.fields @ncmail.net
Environmental Engineer II
Eastern NPDES Program
Division of Water Quality
Tel: [phone] x 551
Fax: [phone]
4 of 4 9/8/2008 10:19 AM