Updated 10/18/07 

## South Carolina Generating Company (SCGENCO)
A.M. Williams Station

- Highway 52 Ash Disposal Facility

NPDES Permit No. SC00 46175

Permitting Engineer: Byron M Amick Revised: February 27, 2009

Facility Rating: Major Minor

Issuance (New) Reissuance Modification Minor Modification

If any part of this application is for a new facility or e xpansion of an existing facility or increase in permitted limits, an antidegradation review may be required per the requirements of R.61

- 68.D. If required, the antidegradation review will be included as part of the permit application.

Site Address: US Highway 52, Moncks Corner, SC 29461 County: Berkeley

Watershed: Basin 03 (Catawba-Santee River Basin)

Facility Description (include SIC code): The Highway 52 Ash Disposal Facility is a proposed landfill for the disposal of coal ash from SCGENCO/Williams Station in Goose Creek, SC with one (1) outfall for runoff and leachate. SIC Code is 4953; Refuse Systems

Receiving Waters and Classification by outfall: Wappoola Swa mp to Molly Branch to the Cooper River Is any discharge to Impaired Waters? No (see State 303(d) list for impaired waters) If Yes, list the monitoring station number(s) and parameter(s) causing impairment: None

Does any discharge have the potential to affect a threatened or endangered species? No (endangered species information from SCDNR Heritage Trust, 2006) If Yes, list the species and the waterbody i n which the species resides:

Outfalls are discussed in Section I of this rationale with a general description of the discharge, treatment system, stream flows and other pertinent information about each outfall.

EPA rev iew of the draft permit is required if any box below is checked (Mark all that apply) Permits with discharges which may adversely affect the waters of another State (Coordination with the other State is also required)

List State and nam e of waterbody(ies) that reach affected state: NA Major permits Permits with any discharge subject to any of the primary industrial categories (see R.61

- 9.122, Appendix A) Permits with any discharge with an average flow exceeding 0.5 MGD Permits for federal facilities with a daily av erage discharge exceeding 0.05 MGD Modification(s) to any permit listed above or a mod that changes a permit to put it into one of the above categories (where it previously was not) Modification to any permit where the s chedule of compliance interim dates are extended more than once

List of Attachments to this Rationale:

Attachment 1 Permit Application

Attachment 2 Water Quality Spreadsheets

Attachment 3 Map of Drinking Water Intake/Source Water Protection Area Relat ive to Discharge 

## F ACT 

## S HEET

AND 

## P ERMIT 

## R

ATIONALERationale Page 2 of 32

Permit No. SC00 46175

I. PERMIT LIMITATIONS AND MONITORING REQUIREMENTS

Outfall 001 Description of outfall, receiving water and wastewater treatment system: The Williams Highway 52 Ash Disposal Facility is a proposed landfill for the disposal of coal ash fro m SCGENCO’s Williams Station in Goose Creek, SC. This landfill will have a sedimentation pond for the collection of ash landfill runoff, ash landfill leachate, and truck wash water. The discharge from the pond will flow to Wappoola Swamp to Molly Branch, then to the west branch of the Cooper River (Class FW). This facility will eventually replace the Williams Highway 17A Ash Disposal Facility, therefore NPDES permit #SC0039535 may be used as guidance to determine limitations. Since this facility has not begun operation no plans have yet been developed for the disposal of sanitary wastewater.

Operator requirements: Based on the proposed treatment system described above and the Pollution Control Act (PCA), the treatment system may be classified as Group I

- Physical/Chemical . The Environmental Certification Board Rules require

that a Grade D

- Physical/Chemical operator be assigned to operate the proposed facility. Inspections of the facility will be required on a daily basis per Regulation 61

- 9.122.41(e).

I nformation for this outfall is based on NPDES Permit Application: 2D dated 3/3/05

Data from Discharge Monitoring Reports (DMRs) and NPDES permit application (including all subsequent data pres ented)

from 1/1/03

- 9/30/05 has been used to evaluate permit limitations.

Previous permit limits are based on the permit (or modification) effective date of January 1, 2003

.

All waterbody data is provided on the attached Water Quality Spreadsheets. This data includes 7Q10, annual average flow, dilution factors, hardness, TSS and other information as explained in this rationale. Additional information as necessary to explain the values used will be provided below.

A. Flow

1. Previous permit limits (effective January 1, 2003 ): Monthly Average: MR, MGD Daily Maximum: MR, MGD Sampling Frequency: 1/month Sample Type: Instantaneous

2. NPDES Application 2D (dated 3/3/05): Average Flow: 0.053 MGD

3. NPDES Application 2D (dated 9/25/98): Average Flow: 0.040 MGD

4. Construction Permit Application for Permit #19,188

- IW (dated 3/19/08) : Average Flow: 0.388 MGD

5. DMR Data: Discharge has not begun.

6. Conclusion: Flow monitoring will continue as previously permitted. Monthly Average: MR, MGD Daily Maximum: MR, MGD Sampling Frequency: 1/month Sample Type: Instantaneous

B. Total Suspended Solids (TSS)

1. Previous permit limits (effective January 1, 2003 ): Monthly Average: MR, mg/l Daily Maximum: 50 mg/l Sampling Frequency: 1/month Sample Type: Grab

2. NPDES Application 2D (dat ed 3/3/05): not reportedRationale Page 3 of 32

Permit No. SC00 46175

3. NPDES Application 2D (dated 9/25/98): Monthly Average: 20 mg/l Daily Maximum: 100 mg/l

4. DMR Data: Discharge has not begun.

5. Other information: The existing limit has been applied based on eng ineering judgment.

6. PQL: 1.0 mg/l (Method SM2540D)

7. Conclusion: The limit will remain as previously permitted. Monthly Average: MR, mg/l Daily Maximum: 50 mg/l Sampling Frequency: 1/month Sample Type: Grab

C. pH

1. Previous Permit Limits (effective January 1, 2003 ): 6.0

– 8.5 standard units. Sampling Frequency: 1/month Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): Monthly Average: 8.5 su Daily Maximum: 9.0 su

4. DMR Data: Discharge has not begun.

5. Water Classification & Standards: SC Reg. 61

- 68 (2004), Section G.10.f. states that the Class Fresh Waters standards for pH shall always be “B etween 6.0 and 8.5”.

6. Conclusion: pH shall be between 6.0 and 8.5, based on Water Classification & Standards. Sampling Frequency: 1/month Sample Type: Grab

D. Oil and Grease

1. Previous permit limits (effective January 1, 2003 ): Monthly Average: 10 mg/l Daily Maximum: 15 mg/l Sampling Frequency: 1/month Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/ 98): Monthly Average: 10 mg/l Daily Maximum: 20 mg/l

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Classification & Standards: SC Reg. 61

- 68 (2004), Section E.5.b. states that all ground waters and

surface waters o f the State shall at all times, regardless of flow, be free from floating debris, oil, grease, scum, and other floating material attributable to sewage, industrial waste, or other water in amounts sufficient to be unsightly to such a degree as to create a nuisance or interfere with classified water uses or existing water uses.

7. Other Information: Historically, using engineering judgment, the Department has determined that in order to achieve the narrative limit, as stated in Regulation 61

- 68, a limit is requ ired for Oil & Grease of 10 mg/l monthly average, and 15 mg/l daily maximum.

8. PQL: 5.0 mg/l (Method 1664A)

9. Conclusion: Since truck washing activities contribute oil and grease to this discharge, the limit will remain as previously permitted.

Month ly Average: 10 mg/l Daily Maximum: 15 mg/l Sampling Frequency: 1/month Sample Type: GrabRationale Page 4 of 32

Permit No. SC00 46175

E. Aluminum, total

1. Previous permit limits (effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. DMR Data: Discharge has not begun.

4. Effluent limitations guidelines: N/A

5. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = none

CMC: daily maximum = none

6. Water Quality Criteria for Protection of Human Health:

- from SC Reg. 61

- 68, Appendix 1(2004): (1) Water & Organism Consumption: none (2) Organism Consumption: none (3) Drinking Water MCL (Maximum Contaminant Level): none

7. Other I nformation: Freshwater Aquatic Life

- from 53 FR 33178 (Aug. 30, 1988): CCC: monthly average = 0.087 mg/l CMC: daily maximum = 0.750 mg/l

8. Practical Quantitation Limit: 50  g/l (EPA Methods 200.7 or 200.8 )

9. Conclusion: This facility is not involved in th e production of aluminum or aluminum products. Since there is no State Standard for aluminum, no limit for aluminum will be established in this permit.

F. Arsenic, total

1. Previous permit limits (effective January 1, 2003 ): Monthly Average: 0.827  g/l Daily Maximum: 1.21  g/l Sampling Frequency: 1/month Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/9 8): Monthly Average: 0.03 mg/l Daily Maximum: 0.19 mg/l

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of Freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2008): CCC: monthly average = 0.150 mg/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CaCO 3 the derived monthly average is 0.3582 mg/l CMC: daily maximum = 0.340 mg/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CaCO 3 the derived daily maximum is 0.8119 m g/l

7. Water Quality Criteria for Protection of Human Health: CARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2008): (1) Water & Organism Consumption: none (2) Organism Consumption: none
(3) Drinking Water MCL (Maximum Contaminant Level): 10  g/l monthly avera ge = 10  g/l x 19486 (DF 4 ) = 195 mg/l daily maximum = 1.86(194.86 mg/l) = 362 mg/l

8. Practical Quantitation Limit: 5  g/l (EPA Methods 200.8, 200.9, or SM3113B )

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, arsenic was not shown to have a reasonable potential to cause or contribute to a violation of the state standard. Therefore no limit will be established at this time. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of t he start of discharge from this facility. Based on the results reported in the EPA Application Form 2C the permit will be modified to add parameters and limitations, if necessary.Rationale Page 5 of 32

Permit No. SC00 46175

G. Cadmium, total

1. Previous permit limits (effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): not reported

4. DMR Data: Discharge has not begun.

5. Ef fluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = 0.10  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CaCO 3 the derived monthly average is 0.000329 mg/l CMC: daily maximum = 0.53  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CaCO 3 the derived daily maximum is 0.001805 mg/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, App endix 1(2004): (1) Water & Organism Consumption: none (2) Organism Consumption: none
(3) Drinking Water MCL (Maximum Contaminant Level): 5  g/l monthly average = 5  g/l x 13034 (DF 3 ) = 65.2 mg/l daily maximum = 1.46(65.2 mg/l) = 95.2 mg/l

8. Practical Quan titation Limit: 0.1  g/l (EPA Methods 200.8, 200.9, or SM3113B )

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, cadmium was not shown to have a reasonable potential to cause or contribute to a violation of the state standard. Ther efore no limit will be established at this time. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of the start of discharge from this facility. Based on the results reported in the EPA Application Fo rm 2C the permit will be modified to add parameters and limitations, if necessary.

H. Copper, total

1. Previous permit limits (effective January 1, 2003 ): Monthly Average:

--- Daily Maximum: MR, mg/l Sampling Frequency: 1/y ear Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): not reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations g uidelines: N/A

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = 2.9  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.01068 mg/l

CMC: da ily maximum = 3.8  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.01399 mg/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2004):
(1) Water & Organism Con sumption: 1300  g/l =1.3 mg/l monthly average = 1.300 mg/l x 13034 (DF 3 ) = 16,944 mg/l daily maximum = 1.46(16,944 mg/l) = 24,738 mg/l (2) Organism Consumption: none (3) Drinking Water MCL (Maximum Contaminant Level): none

8. Practical Quantitation Limit: 10  g/l (EPA Methods 200.7, 200.8, 200.9, or SM3113B )Rationale Page 6 of 32

Permit No. SC00 46175

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, cooper was not shown to have a reasonable potential to cause or contribute to a violation of the state standa rd. Therefore no limit will be established at this time. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of the start of discharge from this facility. Based on the results reported in the EPA Appli cation Form 2C the permit will be modified to add parameters and limitations, if necessary.

I. Iron, total

1. Previous permit limits (effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): Monthly Average: 1.15 mg/l Daily Maximum: 5.00 mg/l

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2008): CCC: monthly average = none CMC: daily maximum = none

7. Water Quality Criteria for Protection of Human Health:

- from SC Reg. 61

- 68, Appendix 1(2008): (1) Water & Organism Consumption: none (2) Organism Consumption: none (3) Drinking Water MCL (Maximum Contaminant Level): none

8. Practical Quantitation Limit: 20  g/l (EPA Methods 200.7 or 200.8 )

9. Conclusion: Since there is no State Standard for iron, no limit for iron will be established in this permit.

J. Manganese, total

1. Previous permit limits (effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): not reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1( 2008): CCC: monthly average = none CMC: daily maximum = none

7. Water Quality Criteria for Protection of Human Health:

- from SC Reg. 61

- 68, Appendix 1(2008): (1) Water & Organism Consumption: none (2) Organism Consumption: none (3) Drinking Water MCL (Ma ximum Contaminant Level): none

8. Practical Quantitation Limit: 10  g/l (EPA Methods 200.7 or 200.8 )

9. Conclusion: Since there is no State Standard for manganese, no limit will be established in this permit.

K. Mercury, total

1. Previous permit limits ( effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): not reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/ARationale Page 7 of 32

Permit No. SC00 46175

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = 0.91  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.0021 mg/l CMC: daily maximum = 1.6  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.0037 mg/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2004):
(1) Water & Organism Consumption: 0.050  g/l monthly average = 0.050  g/l x 13034 (DF 3 ) = 0.6517 mg/l daily maximum = 1.46(0.6517 mg/l) = 0.9515 mg/l
(2) Organism Consumption: 0.051  g/l monthly average = 0. 051  g/l x 1.0 (DF 1 ) = 0.000051 mg/l daily maximum = 1.46(0.000051 mg/l) = 0.000074 mg/l
(3) Drinking Water MCL (Maximum Contaminant Level): 2  g/l monthly average = 2  g/l x 13034 (DF 3 ) = 26.07 mg/l daily maximum = 1.46(26.07 mg/l) = 38.06 mg/l

8. Practical Quantitation Limit: 0.0005  g/l (EPA Methods 1669(sampling)/1631E (analysis) )

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, mercury was not shown to have a reasonable potential to cause or contribute to a viola tion of the state standard. Therefore no limit will be established at this time. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of the start of discharge from this facility. Based on the results r eported in the EPA Application Form 2C the permit will be modified to add parameters and limitations, if necessary.

L. Nickel, total

1. Previous permit limits (effective January 1, 2003 ): Monthly Average:

--- Daily Maximum: MR, mg/l Sampling Frequency: 1/year Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): not reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = 16  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the sta ndard is 0.05767 mg/l CMC: daily maximum = 150  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.5412 mg/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2004):
(1) Water & Organism Consumption: 610  g/l = 0.61 mg/l monthly average = 0.61 mg/l x 13034 (DF 3 ) = 7,950 mg/l daily maximum = 1.46(7,950 mg/l) = 11,607 mg/l
(2) Organism Consumption: 4600  g/l = 4.60 mg/l monthly average = 4.60 mg/l x 1.0 (DF 1 ) = 4.60 mg/l daily maximum = 1.46(4.60 mg/l) = 6.716 mg/l (3) Drinking Water MCL (Maximum Contaminant Level): none

8. Practical Quantitation Limit: 10  g/l (EPA Methods 200.8, 200.9, or SM3113B )Rationale Page 8 of 32

Permit No. SC00 46175

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, nickel was not shown to have a reasonable potential to cause or contribute to a violation of the state standard. Therefore no limit will be established at this time. The permittee will be required to submit a compl ete EPA Application Form 2C within eighteen (18) months of the start of discharge from this facility. Based on the results reported in the EPA Application Form 2C the permit will be modified to add parameters and limitations, if necessary.

M. Selenium, t otal

1. Previous permit limits (effective January 1, 2003 ): not limited

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25 /98): not reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/A

6. Water Quality Criteria for Protection of Freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = 5.0  g/l CMC: daily maximum = none

- since there is no CMC the daily maximum will be twice the monthly average, or 1 0.0  g/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2004):
(1) Water & Organism Consumption: 170  g/l monthly average = 170  g/l x 13034 (DF 3 ) = 2,216 mg/l daily maximum = 1.46(2,216 mg/l) = 3,235 mg/l
(2) Organism Consumption: 4,200  g/l monthly average = 4,200  g/l x 1.0 (DF 1 ) = 4.2 mg/l daily maximum = 1.46(4.2 mg/l) = 6.13 m g/l
(3) Drinking Water MCL (Maximum Contaminant Level): 50  g/l monthly average = 50  g/l x 13034 (DF 3 ) = 652 mg/l daily maximum = 1.46(652 mg/l) = 952 mg/l

8. Practical Quantitation Limit: 5  g/l (EPA Methods 200.8, 200.9, or SM3113B )

9. Conclu sion: Using the Highway 17A ash disposal facility as guidance, it was unclear if selenium would have a reasonable potential to cause or contribute to a violation of the state standard. However, having no data reported for this site, we have added a requir ement to monitor and report. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of the start of discharge from this facility. Based on the results reported in the EPA Application Form 2C the permit wil l be modified to add parameters and limitations, if necessary. Monthly Average: MR, mg/l Daily Maximum: MR, mg/l Sampling Frequency: 1/month Sample Type: Grab

N. Zinc, total

1. Previous permit limits (effective January 1, 2003 ): Monthly Average:

--- Daily Maximum: MR, mg/l Sampling Frequency: 1/year Sample Type: Grab

2. NPDES Application 2D (dated 3/3/05): not reported

3. NPDES Application 2D (dated 9/25/98): no t reported

4. DMR Data: Discharge has not begun.

5. Effluent limitations guidelines: N/ARationale Page 9 of 32

Permit No. SC00 46175

6. Water Quality Criteria for Protection of freshwater Aquatic Life

- from SC Reg. 61

- 68, Appendix 1(2004): CCC: monthly average = none CMC: daily maximum = 37  g/l

- using a stream TSS of 1 mg/l and hardness 25 mg/l as CACO 3 the standard is 0.1803 mg/l

7. Water Quality Criteria for Protection of Human Health: NONCARCINOGEN

- from SC Reg. 61

- 68, Appendix 1(2004):
(1) Water & Organism Consumption: 7,400  g/l monthly av erage = 7400  g/l x 13034 (DF 3 ) = 96,450 mg/l daily maximum = 1.46(96,450 mg/l) = 140,800 mg/l
(2) Organism Consumption: 26,000  g/l monthly average = 26,000  g/l x 1.0 (DF 1 ) = 26 mg/l daily maximum = 1.46(26 mg/l) = 37.96 mg/l (3) Drinking Water MCL (Maxi mum Contaminant Level): none

8. Practical Quantitation Limit: 10  g/l (EPA Methods 200.7, 200.8, 200.9, 289.1, SM3113B or SM3111B )

9. Conclusion: Using the Highway 17A ash disposal facility as guidance, zinc was not shown to have a reasonable potential to cause or contribute to a violation of the state standard. Therefore no limit will be established at this time. The permittee will be required to submit a complete EPA Application Form 2C within eighteen (18) months of the start of discharge from this fa cility. Based on the results reported in the EPA Application Form 2C the permit will be modified to add parameters and limitations, if necessary.

Whole Effluent Toxicity (WET)

Previous permit requirements (effective January 1, 2003 ): chronic toxicity CTC: 100% expressed as a maximum of 40% effect and an average of 25% effect.

- Monitor and report for reproduction and mortality at the CTC Species: Ceriodaphnia dubia Dilution Series:0%, 50%, 60%, 71%, 84%, 100% Sampling frequency: 1/quarter Sample type: Grab

DMR Data: Discharge has not begun.

Mixing Zone and Zone of Initial Dilution (ZID) Information: discharge to zero 7Q10 stream, therefore no mixing

zone or dilution allowed.

Other information: Due to the fact that t he discharge is complex, quarterly toxicity testing will continue to be required.

From the information described above, using the procedures in Regulation 61

- 9.122.44(d)(1)(ii), the Department has determined that this discharge causes, has the reasonable potential to cause or contributes to an excursion of the narrative water quality standards in Regulation 61

- 68.A.4, which says that “It is the goal of the Department...to provide for the survival and propogation of a balanced indigenous aquatic community of flora and fauna” and

“free

- from” criterion in R.61

- 68.E.5. Therefore, limitations on WET are needed.

Testing Requirements for this permit:

Your permit requirements are expressed as a maximum of 40% effect and an average of 25% effect. These

limita tions are designed to protect to the narrative water quality criterion for toxicity of “no toxics in toxic amounts.” For a monitoring period where a single test is performed, the Department has determined that an average 25% effect closely corresponds to 0.05 alpha level and a maximum 40% effect is close to 0.01 alpha level under current test design and methods. This approach mirrors EPA’s use of IC 25, the Inhibition Concentration or

concentration at which 25% effect exists.Rationale Page 10 of 32

Permit No. SC00 46175

Dilution Factor = 7Q10 + Flow of Discharge = 0.0 MGD + 0.053 MGD = 1.0

Flow of Discharge 0.053

Instream Waste Concentration = 1/IWC x 100 = 1/1 x 100 = 100%

Chronic toxicity testing will be performed at the chronic test concentration (CTC) of 100%.

The following calcula tion, as explained in the Bureau’s guidance document Options for Data Analysis of Whole Effluent Toxicity Testing Required by NPDES Permits , September 2001, shows how the multiple concentrations are derived. To determine a geometric series of effluent con centrations given a low concentration L , a high

concentration H, and n concentrations, the concentration factor is

F = (H/L) 1/(n

- 1) and the i th concentration is C i = L * F i

- 1

Where, F is the concentration factor and n is the number of concentrat ions:

For n = 5, L = 50, and H = 100, F = 100 1/(5

- 1) = 2 1/4 = 1.19

50

After determining the concentration factor the following formula is used to determine the test concentrations:

C i = L x F (I

- 1) where, I is the number of concentrations

Deter mining the four concentrations: Note; I = 1,2, 3, 4, 5

C 1 = 50 x 1.19 (1

- 1) = 50%

C 2 = 50 x 1.19 (2

- 1) = 60%

C 3 = 50 x 1.19 (3

- 1) = 71%

C 4 = 50 x 1.19 (4

- 1) = 84%

For this discharge situation, the concentrations are 0%, 50%, 60%, 71%, 84% and 100% for eac h multiple

concentration test.

Groundwater Monitoring

Based on the recommendations of the Department’s Groundwater Quality Section, the permittee shall continue to monitor and report each of the two (2) groundwater monitoring wells (MW

- 1A and MW

- 5) semi

- annually for the following parameters:

Water Table Elevation Arsenic Lead Depth to the Water Table Cadmium Mercury Field pH Chlorides Nickel Field Specific Conductance Chromium Zinc Field Turbidity Copper Selenium

T otal Dissolved Solids (TDS) Iron Sulfate as SO 4Rationale Page 11 of 32

Permit No. SC00 46175

II. GENERAL INFORMATION

A. The effluent from this facility may be subject to the requirements of any of the following regulations: R.61

- 68,

R.61

- 69, R.61

- 9.122, 124, 125, 129, 133, and 403; 40 CF R Part 136; Subchapter N (40 CFR Parts 400 through 402 and 404 through 471); and R.61

- 9.503, 504 and 505.

B. Authority: This permit is written in accordance with applicable laws and regulations including, but not limited to, Regulation 61

- 9, Regulation 6 1

- 68, Pollution Control Act and Clean Water Act.

C. Under R.61

- 9.124.8 (Fact Sheet), a fact sheet shall be prepared for every draft permit for a major NPDES facility or activity, for every Class I sludge management facility, for every NPDES draft permit t hat incorporates a variance or requires an explanation under section 124.56(b), and for every draft permit which the Department finds is the subject

of wide

- spread public interest or raises major issues.

D. The conclusions noted in the Rationale establi sh proposed effluent limitations and permit requirements addressed

in R.61

- 9.122.43 (Establishing Permit Conditions), R.61

- 9.122.44 (Establishing Limitations, Standards and other permit conditions) and other appropriate sections of R.61

- 9.

III. BACKGROUND AND PROCEDURES FOR PERMIT LIMIT DEVELOPMENT

A. The receiving waterbody 7Q10, annual average flow or other critical flow condition at the discharge point, and 7Q10, annual average flow, or other critical flow condition at the boundary of the source water protection area above a proposed or existing drinking water intake (if applicable) are determined by the SCDHEC’s Wasteload Allocation Section. The 7Q10, Annual Average Flow or other critical flow conditions are based on information published or verified by the USGS, an estimate extrapolation from published or verified USGS data or from data provided by the permittee. These flows may be adjusted by the Wasteload Allocation Section to account for existing water withdrawals that impact the flow. The 7Q10 ( or 30Q5 if provided by the applicant), annual average flow at the discharge point, or other critical flow condition or 7Q10 (or 30Q5 if provided by the applicant), annual average flow or other critical flow condition at the boundary of the SWP area for a p roposed or existing drinking water intake will be used to determine dilution factors, as appropriate, in accordance with R.61

- 68.C.4.a & 4.b for aquatic life, human health, and organoleptic effects respectively.

B. Water and organism consumption and dr inking water MCL data will be evaluated as human health values when calculating dilution factors. “The Department may, after Notice of Intent included in a notice of a proposed NPDES permit in accordance with Regulation 61

- 9.124.10, determine that drinkin g water MCLs or W/O shall not apply to discharges to those waterbodies where there is: no potential to affect an existing or proposed drinking

water source and no state

- approved source water protection area.” For permitting purposes, a proposed drinking

w ater source is one for which a complete permit application, including plans and specifications for the intake, is on file with the Department at the time of consideration of an NPDES permit application for a discharge that will affect or has the potential to affect the drinking water source (R.61

- 68.E.14.c(5)). The Department defines the source water protection (SWP) area to be the primary SWP area delineated by the Source

- Water Assessment and Protection (SWAP) Program initiated by the EPA and required by t he states to identify SWP areas to protect drinking water sources. Using the procedure described in the document entitled, “Determination of the Primary and Secondary Source

- Water Protection Areas for Selected Surface

- Water Public

- Supply Systems in South Carolina, 1999,” USGS Water Resource Investigations Report 00

- 4097, the primary SWP area for a drinking water intake is the area which encompasses all 14

- digit Hydrologic Unit Code (HUC) basins that adjoin streams, tributaries, and reservoirs between an in take and the upstream 10

- percent exceedance, 24

- hour travel distance (TOT 10 ). The entire basin above a drinking water intake has been designated as the SWP area where the drainage area is equal to or less than one HUC basin or is estimated to have less th an 24

- hours of instream travel time between the intake and the HUC basin in the headwaters of the drainage basin.

C. Application of numeric criteria to protect human health: If separate numeric criteria are given for organism consumption, water and organ ism consumption (W/O), and drinking water Maximum Contaminant Levels (MCLs), they shall be applied as appropriate. The most stringent of the criteria shall be applied to protect the existing and classified uses of the waters of the State (R.61

- 68.E.14.b(1 )).Rationale Page 12 of 32

Permit No. SC00 46175

D. Numeric criteria have been established in R.61

- 68 based on organoleptic data (prevention of undesirable taste and odor). For those substances which have aquatic life and/or human health numeric criteria and organoleptic numeric criteria, the most st

ringent of the three shall be used for derivation of permit effluent limitations. See R.61

- 68.E.13.

E. Sampling Frequency: Samples and measurements taken for the purpose of monitoring shall be representative of the monitored activity. Monitoring results m ust be conducted according to test procedures approved under 40 CFR Part 136, unless other test procedures have been specified in the permit (R.61

- 9.122.41(j)(4)). Typically, requirements to report monitoring results shall be established on a case

- by

- case basis with a frequency dependent on the nature and effect of the discharge but in no case less than once a year (R.61

- 9.122.44(i)(2)).

F. Compliance Schedules:

1. A person issued an NPDES permit by the Department who is not in compliance with applicable effluent standards and limitations or other requirements contained therein at the time the permit is issued, shall be required to achieve compliance within a period of time as set forth by the Department, with effluent standards and limitations,

with wate r quality standards, or with specific requirements or conditions set by the Department. The Department shall require compliance with terms and conditions of the permit in the shortest reasonable period of time as determined thereby or within a time schedu le for compliance which shall be specified in the issued permit. (R.61

- 9.122.47(c)(1))

2. If a time schedule for compliance specified in an NPDES permit which is established by the Department, exceeds nine (9) months, the time schedule shall provide for interim dates of achievement for compliance with certain applicable terms and conditions of the permit. (R.61

- 9.122.47(c)(2))

G. Procedure for establishing effluent limitations:

1. Effluent limits (mass and concentration) for Five day Biochemical Oxygen De mand (BOD 5 ), Ultimate Oxygen Demand (UOD), Dissolved Oxygen (DO), Total Ammonia Nitrogen (as N), and Nutrients (e.g., nitrogen and phosphorus) are established by the Wasteload Allocation (WLA) Section, with consideration given to technology

- based limitatio ns.

a. Five day Biochemical Oxygen Demand BOD 5 , Ultimate Oxygen Demand (UOD), Dissolved Oxygen (DO):

Effluent limits for conventional oxygen demanding constituents (BOD 5 , UOD and DO) are established to protect in

- stream water quality, while utilizing a port ion of the assimilative capacity of the receiving water. The ability of a water body to assimilate oxygen

- demanding substances is a function of its physical and chemical characteristics above and below the discharge point. Various mathematical techniques, called models, have been developed to estimate this capacity. The Department follows the procedures as outlined in the “State/EPA Region IV Agreement on the Development of Wasteload Allocations/Total Maximum Daily Loads and NPDES Permit Limitations” date d October 30, 1991 (as updated) for determining the assimilative capacity of a given water body. Mathematical models such as QUAL2E and QUAL2E

UNCAS are used in accordance with “Enhanced Stream Water Quality Models QUAL2E and QUAL2E

UNCAS: Documentation a nd Users Manual” (EPA/600/3

- 87/007; dated May 1987) as updated. BOD 5 and UOD values determined from modeling results will be used in permitting as monthly average derived limits (C wla ). Daily maximum derived limits will typically be determined by multipl ying the monthly average value by two.

For facilities subject to effluent guidelines limitations or other technology

- based limitations, BOD 5 will also be evaluated in accordance with the applicable industrial categorical guidelines. These guidelines will be identified in Part I of this rationale when they are applicable to the permit.Rationale Page 13 of 32

Permit No. SC00 46175

b. Total Ammonia Nitrogen (as N):

Ammonia limitations based on oxygen demand will be determined from modeling information as described

above. These values will be used as m onthly average derived limits and a daily maximum will typically be determined by multiplying the monthly average derived limit by two. These values will be compared with the ammonia water quality criteria for protection of aquatic life from Regulation 61

- 68, Attachment 3 and any categorical limitations. The more stringent of the limitations will be imposed. Calculations for aquatic

life criteria and other wasteload recommendations are shown in Part I of this rationale when ammonia is a pollutant of concer n.

c. Discharges of Nutrients:

In order to protect and maintain lakes and other waters of the State, consideration is given to the control of nutrients reaching the waters of the State. Therefore, in accordance with regulation R.61

- 68.E.11
, the Department controls the nutrients as prescribed below. Nutrient limitations will be determined from the best available information and/or modeling performed by the Wasteload Allocation Section to meet these water quality standards.

i. Discharges of nutrients from a ll sources, including point and nonpoint, to waters of the State shall be prohibited or limited if the discharge would result in or if the waters experience growths of microscopic or macroscopic vegetation such that the water quality standards would be vio lated or the existing or classified uses of the waters would be impaired. Loading of nutrients shall be addressed on an individual basis as necessary to ensure compliance with the narrative and numeric criteria.

ii. Numeric nutrient criteria for lakes ar e based on an ecoregional approach which takes into account the geographic location of the lakes within the State and are listed below. These numeric criteria are applicable to lakes of 40 acres or more. Lakes of less than 40 acres will continue to be pr otected by

the narrative criteria.

1. For the Blue Ridge Mountains ecoregion of the State, total phosphorus shall not exceed 0.02 mg/l, chlorophyll a shall not exceed 10 ug/l, and total nitrogen shall not exceed 0.35 mg/l

2. For the Piedmont and Southeastern P lains ecoregions of the State, total phosphorus shall not exceed 0.06 mg/l, chlorophyll a shall not exceed 40 ug/l, and total nitrogen shall not exceed 1.50 mg/l

3. For the Middle Atlantic Coastal Plains ecoregion of the State, total phosphorus shall not exc eed 0.09 mg/l, chlorophyll a shall not exceed 40 ug/l, and total nitrogen shall not exceed 1.50 mg/l.

iii. In evaluating the effects of nutrients upon the quality of lakes and other waters of the State, the Department may consider, but not be limited to, such factors as the hydrology and morphometry of the waterbody, the existing and projected trophic state, characteristics of the loadings, and other control mechanisms in order to protect the existing and classified uses of the waters.

iv. The Department shall take appropriate action, to include, but not limited to: establishing numeric effluent limitations in permits, establishing Total Maximum Daily Loads, establishing waste load allocations, and establishing load allocations for nutrients to ensure that the lakes attain and maintain the narrative and numeric criteria and other applicable water quality standards.

v. The criteria specific to lakes shall be applicable to all portions of the lake. For this purpose, the Department shall define the applicabl e area to be that area covered when measured at full pool

elevation.Rationale Page 14 of 32

Permit No. SC00 46175

2. Effluent concentration limits ( C efflim ) for parameters other than the parameters listed in G.1.a

- c (except ammonia toxicity calculations) above are established using the following pro cedures:

Q 7Q10 7Q10 or other critical flow condition of the receiving water at the discharge point in mgd.

(may require adjustment for withdrawals)

AAF

d Average Annual Flow (AAF) or other critical flow condition of the receiving water at the discharge point in mgd. (may require adjustment for withdrawals) Q 7Q10i 7Q10 or other critical flow condition of the receiving water at the SWP Area boundary in mgd.

AAF

i Average Annual Flow (AAF) of the receiving water at the SWP Area boundary in mgd. Q d Lon g term average discharge flow in mgd.

a. Determine dilution factors: The following information is to be used (where applicable) for establishing effluent concentration limits:

DF 1 : Dilution factor based on 7Q10 or other critical flow condition of the r eceiving water at the discharge point ( Q 7Q10 ). This dilution factor is used to determine the derived limits for protection of the following aquatic life and human health concerns for the reasons indicated:

i. Aquatic Life (see R.61

- 68.C.4.a(1)). Protec tion of aquatic life on a short

- term basis is needed at the point where aquatic organisms become exposed to the discharge.

ii. Human Health

– Organism Consumption for parameters identified as non

- carcinogens per

R.61

- 68.C.4.b(1). Protection for human heal th on a short

- term basis for consumption of aquatic organisms is needed at the point the aquatic organisms become exposed to the discharge.

DF 2 : Dilution factor, at the discharge point, based on the Average Annual Flow of the recei ving water at the discharge point (

AAF d ) . This dilution factor is used to determine the derived limits for protection of the following human health and organoleptic concerns for the reasons indicated:

i. Human Health

– Organism Consumption for parameters identified as carcinogens per R.61

- 68.C.4.b(1). Protection for human health on a long

- term basis to prevent cancer due to consumption of aquatic organisms is needed at the point the aquatic organisms become exposed to the discharge.

ii. Organoleptic effec ts per R.61

- 68.C.4.b(1). Protection for taste and odor issues related to the discharge is needed at the point where the discharge enters the receiving water.

DF 3 : Dilution factor based on the 7Q10 or other critical flow condit ion at the source water protection area boundary for protection of a proposed or existing water intake downstream of the discharge ( Q 7Q10i ). This dilution factor is used to determine the derived limits for protection of the following

human health concerns for the reasons indicated:Rationale Page 15 of 32

Permit No. SC00 46175

i. Human Health

– Water and Organism Consumption for parameters identified as non

carcinogens per R.61

- 68.C.4.b(1) and E.14.c(5) to protect for short

- term health effects when the discharge is above any drinking water intake. P rotection of human health relative to drinking the water from the waterbody and consuming aquatic organisms from the same waterbody is provided by this criterion, but drinking the water withdrawn from the waterbody may require a potentially higher level of protection in terms of applicable dilution than consumption of organisms. In addition, to satisfy the requirements of R.61

- 68.C.10(a), the Department has determined that dilution at the boundary of the Source Water Protection area will protect the source water protection area and drinking water intake to meet this requirement.

For discharges except those to lakes affecting the primary source water protection (SWP) area, dilution will be determined using the largest flow (7Q10 or annual average flow, as appropriate) associated with any TOT10 point along the SWP area boundary upstream of the drinking water intake of concern. For discharges to lakes affecting the primary SWP area, dilution will be determined using the sum of the flows (7Q10 or average annua l flow, as appropriate) associated with all TOT10 point(s) along the SWP area boundary upstream of the drinking water intake of concern. If multiple drinking water intakes are present below the discharge, the SWP area of the intake closest to the discharge will be protected. If the entire basin is designated as the SWP area, the boundary will be the TOT10 at the beginning of the basin, even if it is outside the State boundaries (e.g. North Carolina).

ii. Human Health

- Drinking Water Maximum Contaminant Le vel (MCL) for parameters

identified as non

- carcinogens per R.61

- 68.C.4.b(1) and E.14.c(5) to protect for short

- term health effects when the discharge is above any drinking water intake. Protection of human health relative to drinking the water from the w aterbody after conventional treatment per R.61

- 68.G is provided by this criterion. In addition, to satisfy the requirements of R.61

- 68.C.10(a), the Department has determined that dilution at the boundary of the Source Water Protection area will protect the source water protection area and drinking water intake to meet this requirement.

For discharges except those to lakes affecting the primary source water protection (SWP) area, dilution will be determined using the largest flow (7Q10 or annual average f low, as appropriate) associated with any TOT10 point along the SWP area boundary upstream of the drinking water intake of concern. For discharges to lakes affecting the primary SWP area, dilution will be determined using the sum of the flows (7Q10 or avera ge annual flow, as appropriate) associated with all TOT10 point(s) along the SWP area boundary upstream of the drinking water intake of concern. If multiple drinking water intakes are present below the discharge, the SWP area of the intake closest to the d ischarge will be protected. If the entire basin is designated as the SWP area, the boundary will be the TOT10 at the beginning of the basin, even if it is outside the State boundaries (e.g. North Carolina).

DF 4 : Dilution factor ba sed on the Average Annual Flow at the source water protection area boundary for protection of a proposed or existing water intake downstream of the discharge ( AAF i ). This dilution factor is used to determine the derived limits for protection of the follo wing human

health concerns for the reasons indicated:Rationale Page 16 of 32

Permit No. SC00 46175

i. Human Health

– Water and Organism Consumption for parameters identified as carcinogens per R.61

- 68.C.4.b(1) and E.14.c(5) to protect for long

- term health effects due to cancer when the discharge is ab ove any drinking water intake. Protection of human health relative to drinking the water from the waterbody and consuming aquatic organisms from the same waterbody is provided by this criterion, but drinking the water withdrawn from the waterbody

may requ ire a potentially higher level of protection in terms of applicable dilution than consumption of organisms. In addition, to satisfy the requirements of R.61

- 68.C.10(a), the Department has determined that dilution at the boundary of the Source Water Protec tion area will protect the source water protection area and drinking water intake to meet this requirement.

For discharges except those to lakes affecting the primary source water protection (SWP) area, dilution will be determined using the largest flow (7Q10 or annual average flow, as appropriate) associated with any TOT10 point along the SWP area boundary upstream of the drinking water intake of concern. For discharges to lakes affecting the primary SWP area, dilution will be determined using the sum of the flows (7Q10 or average annual flow, as appropriate) associated with all TOT10 point(s) along the SWP area boundary upstream of the drinking water intake of concern. If multiple drinking water intakes are present below the discharge, the SWP area of th e intake closest to the discharge will be protected. If the entire basin is designated as the SWP area, the boundary will be the TOT10 at the beginning of the basin, even if it is outside the State boundaries (e.g. North Carolina).

ii. Human Health

- Drin king Water Maximum Contaminant Level (MCL) for parameters identified as carcinogens per R.61

- 68.C.4.b(1) and E.14.c(5) to protect for long

- term health effects due to cancer when the discharge is above any drinking water intake. Protection of

human health relative to drinking the water from the waterbody and consuming aquatic organisms from the same waterbody is provided by this criterion, but drinking the water withdrawn from the waterbody may require a potentially higher level of protection in terms of

ap plicable dilution than consumption of organisms. In addition, to satisfy the requirements of

R.61

- 68.C.10(a), the Department has determined that dilution at the boundary of the Source Water Protection area will protect the source water protection area and drinking water intake to meet this requirement.

For discharges except those to lakes affecting the primary source water protection (SWP) area, dilution will be determined using the largest flow (7Q10 or annual average flow, as appropriate) associated w ith any TOT10 point along the SWP area boundary upstream of the drinking water intake of concern. For discharges to lakes affecting the primary SWP area, dilution will be determined using the sum of the flows (7Q10 or average annual flow, as appropriate) a ssociated with all TOT10 point(s) along the SWP area boundary upstream of the drinking water intake of concern. If multiple drinking water intakes are present below the discharge, the SWP area of the intake closest to the discharge will be protected. If th e entire basin is designated as the SWP area, the boundary will be the TOT10 at the beginning of the basin, even if it is outside the State boundaries (e.g. North Carolina).

b. Determine derived limits using the following procedure s:

WQS al Freshwater Standard (based on an established criteria or other published data per R.61

- 68) for protection of Aquatic Life; may be a CCC or CMC as defined belowRationale Page 17 of 32

Permit No. SC00 46175

WQS

org Standard (based on an established criteria or other published data per R.61

- 68) for protection of

Human Health

– Organism Consumption WQS

wo Standard (based on an established criteria or other published data per R.61

- 68) for protection of

Human Health

– Water & Organism Consumption. WQS mcl Standard (based on an established criteria o r other published data per R.61

- 68) for Drinking Water MCL (Maximum Contaminant Level). WQS ol : Standard (based on an established criteria or other published data per R.61

- 68) based on Organoleptic Data.

C aqlife Concentration limit derived from aquatic li fe data

C HH Concentration limit derived from human health data as determined from organism ( C org ), water/organism ( C

wo )and MCL ( C mcl ) data

C ol Concentration limit derived from organoleptic data

C b The b ackground concentration of the concerned parameter in mg/l is typically determined from ambient monitoring data or data provided by applicant. If the waterbody to which the discharge flows is not on the 303(d) list, the 90 th percentile of ambient monitoring data for aquatic life protection for the paramet ers identified in the Appendix (Water Quality Numeric Criteria) to Regulation 61

- 68 from the last 3 years, or whatever is available if less than 3 years, will typically be used. If the waterbody to which the discharge flows is not on the 303(d) list, the m edian value of ambient monitoring data for human health protection for the parameters identified in the Appendix (Water Quality Numeric Criteria) to Regulation 61

- 68 from the last 3 years, or whatever is available if less than 3 years, will typically be us ed. The background concentration is assumed to be zero (0) in the absence of actual data based on Departmental guidance and EPA

recommendation.

i. Determine the derived limits for protection of Aquatic Life ( C aqlife )

1. The following guidelines apply to det ermining aquatic life limits using this basic equation:

a. Typically, the Criterion Maximum Concentration (CMC) is applied as a daily maximum derived limit and the Criterion Continuous Concentration (CCC) is applied as a monthly

aver age derived limit, after consideration of dilution and background concentrations. The CMC and CCC for specific metals will be adjusted using the procedures in 60 FR 22229, “Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollu tants; States’ Compliance

- Revision of Metals Criteria,” May 4, 1995 and the “Technical Guidance on Interpretation and Implementation of Aquatic Life Metals Criteria,” Oct. 1, 1993 and applied as a daily maximum and monthly average, respectively, after cons ideration of dilution and background concentrations. For specific metals, this calculation is explained in detail

later in this rationale.

monthly average = C aqlife using CCC as WQS al daily maximum = C aqlife using CMC as WQS al

b. If only a CMC exists for a particular parameter, the daily maximum derived permit limit will be set using that value, after consideration of dilution and background concentrations. If no other values (e.g., human health) exist for that parameter on which to base a monthly ave rage limit and the discharge is continuous, the monthly average will be set equal to the daily maximum to satisfy Regulation 61

- 9.122.45(d). In no case shall the monthly average limit be set higher than the daily maximum limit. If only a CCC is given, it will be used as a monthlyRationale Page 18 of 32

Permit No. SC00 46175

average derived limit and the daily maximum derived limit will be two (2) times the value obtained for the monthly average based on a simplified statistical procedure for determining permit limits recommended in Section 5.4.2 of t he US EPA’s “Technical Support Document for Water Quality

- based Toxics Control”, EPA/505/2

- 90

- 001, March 1991 (hereafter known as the TSD).

If a CCC exists and no CMC exists and no other acute or chronic data exists, the aquatic life

limits are

month ly average = C aqlife using CCC as WQS al daily maximum = 2 x C aqlife

If a CMC and no CCC exists, and no other acute or chronic data exists, the aquatic life limits

are

monthly average = C aqlife using CMC as WQS al daily maximum = C aqlife using CMC as WQ S al

c. If only an acute toxicity effect concentration for a number of species for a particular pollutant is given as a LC 50 , the lowest concentration should be divided by an acute

- to

- chronic ratio (ACR) of 10 and a sensitivity factor of 3.3, for an acceptabl e instream concentration in order to protect against chronic toxicity effects (R.61

- 68.E.16.a(1)). Other acute toxicity data will be handled similarly. The value obtained from this calculation will be used as a monthly average

derived limit after considera tion of dilution and background concentrations. The daily maximum will be two (2) times the value obtained for the monthly average based on a simplified statistical procedure for determining permit limits recommended in Section 5.4.2 of

the TSD.

monthl y average = C aqlife using other data as WQS al daily maximum = 2 x C aqlife

d. If a chronic toxicity effect concentration for a number of species for a particular pollutant is given as a no observed effect concentration (NOEC), the lowest concentration should be divided by a sensitivity factor of 3.3 in order to protect against chronic toxicity to the most sensitive species (R.61

- 68.E.16.a(2)). Other chronic toxicity data will be handled similarly.

The value obtained from this calculation will be used as a mon thly average derived limit after consideration of dilution and background concentrations. The daily maximum will be two (2) times the value obtained for the monthly average based on a simplified statistical procedure for determining permit limits recommen ded in Section 5.4.2 of the TSD.

monthly average = C aqlife using other data as WQS al daily maximum = 2 x C aqlife

e. If both acute and chronic data are available for a particular pollutant, monthly average derived

limit will be calculated as in c and d ab ove for each acute and chronic, respectively. The more stringent of the monthly average derived limits will be the monthly average derived limit used after consideration of dilution and background concentrations. The daily maximum will be two (2) times t he value obtained for the monthly average based on a simplified statistical procedure for determining permit limits recommended in Section 5.4.2 of the TSD.

monthly average = C aqlife using other data as WQS al daily maximum = 2 x C aqlifeRationale Page 19 of 32

Permit No. SC00 46175

f. Consider the background concentration ( C b ) of the parameter of concern. If the background concentration is equal to or greater than the applicable standard ( WQS, as defined above) for the parameter of concern, then the derived concentration limit ( C aqlife ) for that p arameter is established equal to the standard ( WQS ) so that no additional amount of that pollutant is added to the waterbody. An exception exists where the naturally occurring instream concentration for a substance is higher than the derived permit effluen t limitation. In those situations, the Department may establish permit effluent limitations ( C efflim ) at a level higher than the derived limit, but no higher than the natural background concentration (i.e. a “rise above background” limit). In such cases, the Department may require biological instream monitoring and/or whole effluent toxicity (WET) testing (R.61

- 68.E.14.c(2)).

If C b is not based on naturally occurring concentrations and

Then, generally,

.

If C b i s based on naturally occurring concentrations and

Then, generally,

.

2. Metals: Regulation 61

- 9.122.45(c) requires that permit limits be expressed in terms of total recoverable metal (with limited exceptions). I n order to translate from the water quality criterion to a total recoverable metal, Regulation R.61

- 68.E.14.c(4) provides for the use of the EPA Office of Water Policy and "Technical Guidance on Interpretation and Implementation of Aquatic Life

Metals Crit eria", October 1, 1993. A subsequent revision published in the Federal Register (60 FR 22229) on May 4, 1995 updated the data in the original report. See R.61

- 68 Appendix for CMC and CCC values and equations, Attachment 1 for “Conversion Factors for Diss olved Metals” and Attachment 2 “Parameters for Calculating Freshwater Dissolved Metals Criteria that

are Hardness

- Dependent”.

Per R.61

- 68.E.14.a(3), the CMC and CCC are based on a hardness of 25 mg/l if the ambient or mixed stream hardness is equal to o r less than 25 mg/l. Concentrations of hardness less than 400 mg/l may be based on the mixed stream hardness if it is greater than 25 mg/l and less than 400 mg/l and 400 mg/l if the ambient stream hardness is greater than 400 mg/l. The ambient stream

hard ness is assumed to be 25 mg/l in the absence of actual stream data. Mixed stream hardness may be determined using flow

- weighted effluent hardness and stream hardness.

The following equations and constants will be used to calculate aquatic life metals li mits based on

these documents. The values of the terms referenced in this section and determined from the equations below are included in the Metals spreadsheet attached to this rationale. The following metals are subject to this section:

arsenic lead

cadmium mercury chromium (III & VI) nickel

copper zinc

The equation for C d below changes the total metal to dissolved metal. From Technical Guidance Manual for Performing Waste Load Allocations Book II, Rivers and Streams , EPA/44 0/484/022.Rationale Page 20 of 32

Permit No. SC00 46175

(adjusted for hardness)

where C

d = Dissolved metal concentration (μg/l)

S = a constant to represent the CCC or CMC (μg/l)

CF = Conversion factor considered most relevant in fresh water for aquatic life as defined by EPA for each metal

Once the dissolved metal concentration is known, determine C p using the equation for C d above and the following equations.

where C

p = Particulate sorbed metal concentra tion (μg/l). This value represents the revised water quality criterion for the metal to be used for ambient data comparison.

K pb = Linear partition coefficient using the stream TSS (liters/mg)

K po = Metal

- specific equilibrium constant (liters/mg)

a = Metal

- specific constant

TSS b = Background or in

- stream Total Suspended Solids (TSS) concentration (mg/l). The background TSS is assumed to be 1 mg/l in the absence of actual instream data based on the 5th percentile of ambient TSS data on

South Car olina waterbodies from 1993

- 2000.

To determine the effluent limit ( C aqlife )

, use the following equations to translate the limits into a

total recoverable metal concentration.

where TSS

e = Effluent Total Suspended Solids (TSS) con centration (mg/l) determined

from actual long

- term average data or proposed permit limits if no data

available.

TSS avg = Average in

- stream (mixed) TSS concentration (mg/l)

where C t = Total metal concentration ( μg/l)

K p = Linear partition coefficient (liters/mg). This is the distribution of metal at equilibrium between the particulate and dissolved forms.

Once C t has been calculated, it is multiplied by DF 1 and background concentrations are accounted

for to obt ain the derived limit (max or avg) ( C aqlife ):Rationale Page 21 of 32

Permit No. SC00 46175

monthly average = C aqlife based on CCC daily maximum = C aqlife based on CMC

3. Where a Water Effects Ratio (WER) is used to adjust a criterion, derived limits for the adjusted aquatic li fe criterion ( C aqlife

- adj ) are calculated as follows. The WER is a type of site

- specific permit effluent limit (as allowed by R.61

- 68.E.14.c(7)) derived using a ratio determined from EPA methodology. Both DHEC and EPA must approve the WER prior to implem entation. See EPA's
1994 “Interim Guidance on the Determination and Use of Water

- Effect Ratios (WERs) for Metals.” The approved WER will be shown in the water quality spreadsheets on the Data sheet. The revised aquatic life value will be shown with the WER, hardness and dissolved metals adjustments, as appropriate, in the aquatic life columns on the Pollutant spreadsheet.

a. For metals identified in #2 above, revise the equation for S as follows:

S = [CCC or CMC (adjusted for hardness)] x WER

F ollow the remaining calculations in #2 above to get an adjusted C aqlife value that will be used

to determine derived limits:

monthly average = C aqlife

- adj based on CCC daily maximum = C aqlife

- adj based on CMC

b. For other parameters, use the appropriate equation in #1 above to derive an adjusted C aqlife value. The monthly average will be calculated as follows using the appropriate WQS al and the daily maximum calculated using the appropriate equations in #1 above.

4. Where the Reca lculation Procedure is used to adjust a criterion, derived limits for the adjusted aquatic life criterion ( C aqlife

- adj ) are calculated as follows. The Recalculation Procedure is intended

to cause a site

- specific criterion to appropriately differ from the State

- adopted national aquatic life criterion if justified by demonstrated pertinent toxicological differences between the aquatic species that occur at the site and those that were used in the derivation of the criterion. It is important to note that the site (the portion of the waterbody or watershed being affected) must be clearly defined. This procedure is used to develop site

- specific criteria in accordance with R.61

- 68.C.12. Both DHEC and EPA must approve the recalculated criterion prior to impleme ntation. The recalculated criterion will require an update to the Water Classifications and Standards Regulations, R.61

- 68 and 61

- 69.

The approved recalculated aquatic life criteria ( SS

- CCC and SS

- CMC, as appropriate) will be shown adjusted for hardness on the Data spreadsheet. The additional dissolved metals adjustments, as appropriate, will be shown in the aquatic life columns on the Pollutant spreadsheet. If the parameter being adjusted is one of the metals in #2 above, SS will include all the appropr iate metals adjustments.Rationale Page 22 of 32

Permit No. SC00 46175

monthly average = C aqlife

- adj based on CCC daily maximum = C aqlife

- adj based on CMC

5. Where a WER and recalculation procedure are combined to adjust a criterion, derived limits ( C aqlife

- adj ) for aquatic life protection are calculated by combining the calculations in #3 and #4.

monthly average = C aqlife

- adj based on CCC daily maximum = C aqlife

- adj based on CMC

6. Other scientifically defensible methods for developing site

- specific aquati c life effluent limits or

site

- specific criterion may be used on a case

- by

- case basis.

ii. Determine derived limits for protection of Human Health

1. The following guidelines apply to determining human health limits:

a. The human health criterion given by Regulation 61

- 68 will be applied as a monthly average derived limit after consideration of dilution and background concentrations ( C HH

- avg ). Exceptions exist based on EPA criteria and are indicated for specific parameters. No limits on

human health b ased on water and organism consumption or drinking water MCLs will be imposed if there is no potential to affect an existing or proposed drinking water intake and no

state

- approved source water protection area (i.e., if there is no intake downstream of the discharge) in accordance with Regulation 61

- 68.E.14.c(5).

b. The daily maximum permit limit will be determined from the monthly average value from (a) above and a multiplier ( M) determined using a statistical procedure recommended in Section 5.5 using avera ge = 95 th percentile from Table 5

- 3 in the TSD. The permitted or proposed number of samples per month (n) is used with the coefficient of variation (CV) to determine

M

.

where:

CV = co efficient of variation of the effluent concentration. For a data set where

n >10, the CV is calculated as standard deviation divided by mean for the data set being evaluated. For data set where n <10, the CV is estimated to equal

0.6. For less than 10 item s of data, the uncertainty in the CV is too large to

calculate a standard deviation or mean with sufficient confidence.Rationale Page 23 of 32

Permit No. SC00 46175

n = the number of effluent samples per month (where frequency is less than 1/month, n =1)

z
m = the percentile exceedance probability fo r the daily maximum permit limit (=2.326 for 99 th percentile basis)

z
a = the percentile exceedance probability for the monthly average permit limit (=1.645 for 95 th percentile basis)

C HH

- max = M * C HH

- avg

c. Consider the background concentration ( C b ) of the parameter of concern. If the background concentration is equal to or greater than the applicable standard ( WQS, as defined above) for the parameter of concern, then the derived concentration limit ( C HH e ) for that parameter and for the protection of th at standard is established equal to the standard ( WQS ). An exception exists where the naturally occurring instream concentration for a substance is higher than the derived permit effluent limitation. In those situations, the Department may establish perm it effluent limitations ( C efflim ) at a level higher than the derived limit, but no higher than the natural background concentration (i.e. a “rise above background” limit). In such cases, the Department may require biological instream monitoring and/or whol e effluent toxicity (WET) testing (See R.61

- 68.E.14.c(3)).

If C b is not based on naturally occurring concentrations and

Then, generally,

.

If C b is based on naturally occurring concentrations and

Then, generally,

.

2. Human Health

– Organism Consumption ( C org ).

a. For Carcinogens The Monthly Average is calculated as follows:

The Daily Maximum is calculated as

C org

- max = M * C org

b. For No n

- carcinogens The Monthly Average is calculated as follows:

The Daily Maximum is calculated asRationale Page 24 of 32

Permit No. SC00 46175

C org

- max = M * C org

3. Human Health

– Water and Organism Consumption ( C

wo )

a. For Carcinogens The Monthly Average is calculated as f ollows:

The Daily Maximum is calculated as

C

wo

- max = M * C

wo

b. For Non

- carcinogens The Monthly Average is calculated as follows:

The Daily Maximum is calculated as

C

wo

- max = M * C

wo

4. Human Health

– Drink ing Water Maximum Contaminant Level (MCL) ( C mcl ).

a. For Carcinogens The Monthly Average is calculated as follows:

The Daily Maximum is calculated as

C mcl

- max = M * C mcl

b. For Non

- carcinogens The Monthly Average is calculated as f ollows:

The Daily Maximum is calculated as

C mcl

- max = M * C mclRationale Page 25 of 32

Permit No. SC00 46175

5. Organoleptic criteria ( C ol ).

The Monthly Average is calculated as follows:

The Daily Maximum is calculated as

C ol

- max = M * C ol

iii. P aram eters given in a wasteload allocation for oxygen

- demanding pollutants and nutrients will be

limited as monthly average = C
wla

daily maximum = 2 x C
wla

c. Determine the most stringent of applicable water quality data using the monthly average derived l imits

determined above:

monthly average C efflim = minimum of derived monthly averages ( C aqlife , C

org , C

wo , C mcl , C

ol , C wla ) daily maximum C efflim = minimum of derived daily maximums ( C aqlife , C

org

- max , C

wo

- max , C

mcl

- max , C

ol

- max , C

wla

- max )

d. Determi ne whether the discharge causes, has the reasonable potential to cause or contributes to a water quality violation.

Regulation 61

- 9.122.44(d)(1)(i) states: “Limitations must control all pollutants or pollutant parameters (either conventional, nonconventio nal, or toxic pollutants) which the Department determines are or may be discharged at a level which will cause, have the reasonable potential to cause, or contribute to an excursion above any State water quality standard, including State narrative criteria for water quality.”

When determining whether a discharge causes, has the reasonable potential to cause or contributes to an instream excursion, the Department will use procedures which account for controls on point and nonpoint sources of pollution, the variability of the pollutant in the effluent, the sensitivity of the species to toxicity testing (when evaluating whole effluent toxicity), and, where appropriate, the dilution of the effluent in the receiving water (R.61

- 9.122.44(d)(1)(ii)).

Based on th e above statements, there are three scenarios when limitations are required, as follows:

i. When data provided by the permit applicant indicates discharge values greater than the proposed limitation derived above, that discharge may cause an excursion abo ve a narrative or numeric water quality criterion.

ii. A discharge may be determined to contribute to an excursion of a water quality criterion when the waterbody is impaired (e.g., on the 303(d) list) for the parameter of concern and that parameter is a lso being discharged at levels above the water quality criterion.

iii. Reasonable potential to cause a water quality violation is determined using the following information:

The Department will primarily use EPA’s Technical Support Document (TSD) for det ermining reasonable potential using effluent data. Other methods may be used as well to evaluate data sets. All pollutants given in a wasteload allocation or an effluent limitation guideline will be limited in the permit.Rationale Page 26 of 32

Permit No. SC00 46175

When effluent data consists of non

- quantifiable/non

- detectable values or when no effluent data is available, other factors and information are considered to determine reasonable potential. In situations where a pollutant is known to be present in the wastestream (due to production data or other information), we know it is being discharged and has the potential to impact even though it may not be quantifiable. The fact that it is present will be enough information to say reasonable potential exists for that pollutant. Therefore, a reaso nable potential decision is based on various data and information, and not just non

- quantifiable/non

- detectable data. Consideration is given to existing data, dilution in the waterbody, type of receiving water, designated use, type of industry/wastestream , ambient data, history of compliance, and history of toxic impact. If any source of information indicates reasonable potential to cause or contribute to an exceedance of the water quality standard, a water quality limit will be

established.

Note: The result of the following calculations may indicate that reasonable potential does not exist. However, as stated above, other information may “override” this numerical determination to justify the

need for a limit.

1. The procedure for determining reasonab le potential from actual effluent data is explained in Box

3

- 2 on page 53 of the TSD. Multiplying factors are determined from Table 3

- 2 at a 95% confidence level and 95% probability in Section 3.3.2. The following describes the procedures

used for determ ining reasonable potential for chemical

- specific parameters and WET, under certain circumstances. More information on determining reasonable potential for WET is given in

Item 2 below.

Step 1: Data Analysis: The statistical calculations involved in the “Reasonable Potential” analysis require discrete numerical data. The following describes how the effluent data will be used in determining reasonable potential.

Actual analytical results should be used whenever possible. Results less than detection and quantification should be used as follows:

a. If the permittee reports results below the practical quantitation limit (PQL) (as defined by the permit), then the reported “less than PQL” value for a given sample is generally

assumed to be zero.

b. If the p ermittee uses a detection/quantification level that is greater than the PQL, then the reported “less than” value for a given sample is generally assumed to be a discrete value equal to the detection/quantification level used by the permittee.

c. If the re ported data consists of both discrete and non

- discrete values and/or the data is reported using varying detection/quantification levels, then, generally, a combination of the above two approaches is used, or the data is evaluated in a manner that is most

a ppropriate for that data set.

Note: For information on the acceptable analytical methods and PQLs please refer to NPDES permit application attachment titled “Practical Quantitation Limits (PQL) and Approved Test Methods.”

Step 2: Using data from the perm it application, other data supplied by the applicant and/or Discharge Monitoring Report (DMR) data, determine the total number of observations ( n ) for a particular set of effluent data and determine the highest value ( C

max ) from that data

set. For the mont hly average comparison, the data set will include monthly average resultsRationale Page 27 of 32

Permit No. SC00 46175

and n will be the number of months in which they sampled in the time period being evaluated. For the daily maximum comparison, the data set will include daily maximum

results and n will be the total number of samples in the time period being evaluated. Individual results may not necessarily be used in the calculation.

Step 3: Determine the coefficient of variation ( CV ) for the data set. For a data set where n >10, the

CV is calcula ted as standard deviation divided by mean for the data set being evaluated.

For data set where n <10, the CV is estimated to equal 0.6. For less than 10 items of data, the uncertainty in the CV is too large to calculate a standard deviation or mean with

s ufficient confidence.

for

for

where: = Standard Deviation of the samples

= Mean of the samples

Step 4: Determine the appropriate multiplying factor ( MF ) from either Table 3

- 2 or using the

formulae in Section 3.3.2 of the TSD.

a. Determine the percentile represented by the highest concentration in the sample data.

where: p

n = Percentile represente d by the highest concentration in the data

n = number of samples Confidence Level = 0.95 i.e. 95%

b. Determine the multiplying factor ( MF ), which is the relationship between the percentile described above ( C

p ) and the selected upper bound of the log normal effluent distribution,

which in this case will be the 95 th percentile ( C 95 ).

where: Z

95 is the standardized Z

- score for the 95 th percentile of the standardized

normal distribution = 1.645

Z

p is the standardized Z

- score for the p th percentile of the standardized normal distribution.(determined in (b) above)

Note: The values of Z

- scores are listed in tables for the normal distribution. If using Microsoft® Excel, this can be calculated using the NORMSINV function.Rationale Page 28 of 32

Permit No. SC00 46175

Step 5: Multiply the highest value from the data set ( C

max ) by the multiplying factor ( MF ) determined in Step 4 to obtain the maximum receiving water concentration ( RWC ).

Step 6: RWC ≤ Derived limit ( C efflim ) implies that reasonable potential does not exist.

RWC > Derived limit ( C efflim ) implies that reasonable potential exists.

2. Reasonable potential for Whole Effluent Toxicity (WET) may be determined from numerical data using the followin g procedure:

a. When the effluent data is given in terms of percent effluent as an IC 25 , LC 50 and/or NOEC

values:

Step 1: Convert the given values to toxic units: TU

a for acute data and TU

c for chronic data, respectively, using the following formulae. P lease note that an NOEC derived using the

IC 25 is approximately the analogue of an NOEC derived using hypothesis testing. The IC 25 is the preferred statistical method for determining the NOEC (EPA TSD, March 1991, p.6).

or if IC 25 available

Step 2: Using DMR data or other data provided by the applicant, determine the total number of observations ( n ) for a particular set of effluent data and determine the highest value ( TU
a ,

max or TU

c , m ax ) from that data set.

Step 3: Determine the coefficient of variation ( CV ) for the data set. For a data set where n >10, the

CV is calculated as standard deviation divided by mean. For data set where n <10, the CV is estimated to equal 0.6. For less t han 10 items of data, the uncertainty in the CV is too large to calculate a standard deviation or mean with sufficient confidence.

Step 4: Determine the appropriate multiplying factor ( MF ) from either Table 3

- 2 or using the formulae in Section 3.3.2. (see iii.1, Step 4 above).

Step 5: Multiply the highest value of TU

a , max or TU

c , max from the data set by the multiplying factor ( MF ) determined in Step 4 and the dilution at the edge of the mixing zone (the test concentration obtained from mixing zone model ing or demonstration) to obtain the maximum receiving water concentration ( RWC )

RWC for Acute Toxicity = [ TU

a , max * MF * conc. at MZ boundary]

RWC for Chronic Toxicity = [ TU

c , max * MF * conc. at MZ boundary ]

Step 6: RWC for Acute Toxicity ≤ 0.3TU

a implies that a reasonable potential does not exist

RWC for Acute Toxicity > 0.3TU

a implies that a reasonable potential exists

RWC for Chronic Toxicity ≤ 1.0TU

c implies that a reasonable potential does not exist

RWC for Chroni c Toxicity > 1.0TU

c implies that a reasonable potential existsRationale Page 29 of 32

Permit No. SC00 46175

b. When pass/fail effluent data only is available and all tests have passed, the Department may be able to determine reasonable potential in a manner similar to above assuming the test

concentr ation of interest is greater than or equal to the concentration at which the permittee has tested. If the permittee has not tested at or above the test concentration of interest, the Department cannot say that reasonable potential does not exist, unless p erhaps, circumstances related to the discharge have changed. If any failures exist in the data set, reasonable potential may be determined to exist.

c. Other methods for determining reasonable potential may be used if appropriately justified.

e. Consi der Effluent Limitations Guidelines (ELG or Categorical guidelines)

The more stringent of the effluent limitations guidelines average and maximum derived limits and water quality

- derived average and maximum limits shall be used as permit limits, unless ot her information indicates more stringent limits are needed (e.g. previous permit limits due to backsliding). Categorical limitations based on mass may be converted to concentration using the long

- term average flow of the discharge for comparison to the mo nthly average and daily maximum derived limits.

1. For effluent guidelines based on production, limits will be calculated as follows:

where

ELG lim : the mass limit, in lbs/day, for an applicable pollutant based on the production

EL Gprod: the production rate, in lbs, for the applicable guideline(s), usually based on long

- term average data

ELG: the effluent guideline limitation, given as a measure of production (e.g. lbs/1000 lbs), for an applicable pollutant

2. For effluent guidel ines based on flow, limits will typically be calculated as follows:

ELG lim: the mass limit, in lbs/day, for the applicable pollutant based on the applicable flow ELGflow: the long

- term average process flow rate, in MGD, for the a pplicable guideline(s) (unless

otherwise specified in the guideline)

ELG: the concentration limitation, in mg/l, for the applicable pollutant from the applicable guideline(s)

H. Other considerations

1. When the derived permit effluent limitation based on aquatic life numeric criteria is below the practical quantitation limit for a substance, the derived permit effluent limitation shall include an accompanying statement in the permit that the practical quantitation limit using approved analytical methods shall be considered as being in compliance with the limit. Appropriate biological monitoring requirements shall be incorporated into the permit to determine compliance with appropriate water quality standards (R.61

- 68.E.14.c(2)).



### 2. When the derived per mit effluent limitation based on human health numeric criteria is below the practical quantitation limit for a substance, the derived permit effluent limitation shall include an accompanying statement in the permit that the practical quantitation limit usi ng approved analytical methods shall be considered as being in compliance with the limit (R.61

- 68.E.14.c(3)).

3. The effluent concentration limits determined above may not necessarily be the NPDES permit limit. NPDES

Permit limits are determined after a reasonable potential analysis is conducted using these derived limits and also after evaluating other issues such as anti

- backsliding and antidegradation.Rationale Page 30 of 32

Permit No. SC00 46175

4. When mass limits are calculated, the formula to be used is as follows.

Mass (lb/day) = Flow ( mgd) * Concentration (mg/l) * 8.345

5. Per Regulation 61

- 9.122.45(d), for continuous discharges all permit effluent limitations, standards, and prohibitions, including those necessary to achieve water quality standards, shall unless impracticable be state d as maximum daily and average monthly discharge limitations for all dischargers other than publicly owned

treatment works.

6. Antibacksliding: When a permit is reissued, the terms and conditions of the reissued permit must be at least as stringent as th ose final limits in the previous permit unless certain exceptions are met (see Regulation 61

- 9.122.44.l).

IV. PROCEDURES FOR REACHING A FINAL PERMIT DECISION

A. Comment Period (R.61

- 9.124.10 and 11)

The Department of Health and Environmental Control propo ses to issue an NPDES permit to this applicant subject to the effluent limitations and special conditions outlined in this document. These determinations are tentative.

During the public comment period, any interested person may submit written comments on the draft permit to the following address:

SC Dept. of Health and Environmental Control Water Facilities Permitting Division

Bureau of Water

2600 Bull Street Columbia, South Carolina 29201

For additional information, interested persons may contact Byron M Amick at 803

- 898

- 4236

.

All written comments received during the period beginning July 28, 2006 and ending on August 28, 2006 shall be considered in making the final decision and shall be answered as prescribed below. See Public Notice # 06

- 187

- R

.

Per R.61

- 9.124.17, the Department is only required to issue a response to comm ents when a final permit is issued. This response shall:

1. Specify which provisions, if any, of the draft permit have been changed in the final permit decision, and the reasons for the change; and

2. Briefly describe and respond to all significant comments o n the draft permit raised during the public comment period, or during any hearing.

The response to comments shall be available to the public.

B. Public Hearings (R.61

- 9.124.11 and 12)

During the public comment period, any interested person may request a pu blic hearing, if no hearing has already been scheduled. A request for a public hearing shall be in writing and shall state the nature of the issues proposed to be raised in the hearing.Rationale Page 31 of 32

Permit No. SC00 46175

Determinations and Scheduling.

1. Within the thirty (30) day comm ent period or other applicable comment period provided after posting or publishing of a public notice, an applicant, any affected state or interstate agency, the Regional Administrator or any other interested person or agency may file a petition with the D epartment for a public hearing on an application for a permit. A petition for a public hearing shall indicate the specific reasons why a hearing is requested, the existing or proposed discharge identified therein and specifically indicate which portions o f the application or other permit form or information constitutes necessity for a public hearing. If the Department determines that a petition constitutes significant cause or that there is sufficient public interest in an application for a public hearing , it may direct the scheduling of a hearing thereon.

2. A hearing shall be scheduled not less than four (4) nor more than eight (8) weeks after the Department determines the necessity of the hearing in the geographical location of the applicant or, at the di scretion of the Department, at another appropriate location, and shall be noticed at least thirty (30) days before the hearing. The notice of public hearing shall be transmitted to the applicant and shall be published in at least one (1) newspaper of gene ral circulation in the geographical area of the existing or proposed discharge identified on the permit application and shall be mailed to any person or group upon request thereof. Notice shall be mailed to all persons and governmental agencies which rece ived a copy of the notice or the fact sheet for the permit application.

3. The Department may hold a single public hearing on related groups of permit applications.

4. The Department may also hold a public hearing at its discretion, whenever, for instance, suc h a hearing might clarify one or more issues involved in the permit decision;

5. Public notice of the hearing shall be given in accordance with R.61

- 9.124.10.

Any person may submit oral or written statements and data concerning the draft permit. Reasonable limits may be set upon the time allowed for oral statements, and the submission of statements in writing may be required. The public comment period under R.61

- 9.124.10 shall automatically be extended to the close of any public hearing

under this section. The hearing officer may also extend the comment period by so stating at the hearing.

A tape recording or written transcript of the hearing shall be made available to the public.

C. Obligation to raise issues and provide information during the public comment period. (R.61

- 9.124.13)

All persons, including applicants, who believe any condition of a draft permit is inappropriate or that the Department’s tentative decision to deny an application, terminate a permit, or prepare a draft permit is inapprop riate, must raise all reasonably ascertainable issues and submit all reasonably available arguments supporting their position by the close of the public comment period (including any public hearing). No issue shall be raised during an appeal by any party t hat was not submitted to the administrative record as part of the preparation and comment on a draft permit, unless good cause is shown for the failure to submit it. Any supporting materials which are submitted shall be included in full and may not be inco rporated by reference, unless they are already part of the administrative record in the same proceeding, or consist of State or Federal statutes and regulations, Department and EPA documents of general applicability, or other generally available reference materials. Commenters shall make supporting materials not already included in the administrative record available. (A comment period longer than 30 days may be necessary to give commenters a reasonable opportunity to comply with the requirements of this section. Additional time shall be granted under R.61

- 9.124.10 to the extent that a commenter who requests additional time demonstrates the need for such time).Rationale Page 32 of 32

Permit No. SC00 46175

D. Issuance and Effective Date of the Permit

1. After the close of the public comment period on a draft permit, the Department shall issue a final permit decision. The Department shall notify the applicant and each person who has submitted written comments or requested notice of the final permit decision. This notice shall include reference to t he procedures for appealing a decision on a permit. For the purposes of this section, a final permit decision means a final decision to issue, deny, modify, revoke and reissue, or terminate a permit.

2. A final permit decision shall become effective 30 days after the service of notice of the decision unless:

(a) A later effective date is specified in the decision; or

(b) No comments requested a change in the draft permit, in which case the permit shall become effective on

the effective date shown in the issued permit.

3. Issuance or Denial of Permits. An appeal to a final determination of the Department or to a condition of a permit issued or the denial of a permit pursuant to the State law and Regulation 61

- 9, shall be in accordance with and subject to 48

- 1

- 200 of the SC Code (see E below).

E. Adjudicatory Hearings

The issuance of this permit by the S.C. Department of Health and Environmental Control (Department) becomes the final agency decision 15 days after notice of the decision has been mailed to the applicant or respondent, unless a written request for final review is filed with the Department.

An applicant, permittee, licensee, or affected person who wishes to appeal this decision must file a written request

for final review with the Clerk of the Board at the following address or by facsimile at 803

- 898

- 3323:

Clerk of the Board

SC DHEC

2600 Bull Street Columbia, SC 29201

The request for final review should include the following:

1. The grounds on which the Department’s decision is challenged and the specific changes sought in the decision,

2. A statement of any significant issues or factors the Board should consider in deciding how to handle the matter,

and

3. A copy of the Department’s decision or action under review.

If the 15th day occurs on a weekend or State holiday, the request is due to be received by the Clerk of the Board on the next working day. The request for final review must be received by the Clerk of the Board by 5:00 p.m. on the date it is due. If a timely request for final revie w is filed with the Clerk of the Board, the Clerk will provide additional information regarding procedures.

The Board of Health and Environmental Control has 60 days from the date of receipt of a request for final review

to conduct a final review confe rence. The conference may be conducted by the Board, its designee, or a committee of three members of the Board appointed by the chair.

If a final review conference is not conducted within 60 days, the Department decision becomes the final agency

decis ion, and a party may request a contested case hearing before the Administrative Law Court within 30 days

after the deadline for the final review conference.

Information pertaining to adjudicatory matters may be obtained by contacting the Legal Office of the Department of Health and Environmental Control, 2600 Bull Street, Columbia, South Carolina or by calling 803

- 898

- 3350.