NC0024945_Correspondence_20040913

NPDES DOCUMENT SCANNING COVER SHEET
NC0024945
Irwin Creek WWTP
NPDES Permit:
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Draft Permit
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
September 13, 2004
This document ioec printed on reuose paper - ignore any
content on the re cerise side

subject: [Fwd: Sugar and Irwin WWTP's]
From: Jackie Nowell <[e-mail]>
Date: Mon, 13 Sep 2004 11:05:05 -0400
To: Mark McIntire <mark.mcintirencmail.net>
Mark, will get you a hard copy of this latest letter. I f we could review it first, then decide when to meet with
them.
Original Message 5-uCkla NC uu Z 4 9 '3 7
Subject:Sugar and Irwin WWTP's
Date:Thu, 9 Sep 2004 11:53:40 -0400 h e.w t )J 1 W 2,4 9 /4 5
From:Jarrell, Jackie <[e-mail]>
To:'jackie,wiwellAncmail.net' <jackie.nowell(7a,ncmail.net>
CC:Padgett, Dawn <DPadgett@a,ci.charlotte.nc.us>
Hi Jackie, Hope you are doing well. I hope that you have had a chance to
review the letters that we sent to you and Mark in July and then
August(followup) regarding proposed Water Quality Based Limits for both
Sugar and Irwin Creek WWTP's. As you know both of these permits are now
3years expired and we are anxious to get these permits resolved as I am sure
that your division is. We would like to schedule a meeting with you in
Raleigh (or you are welcome to come here) to discuss the permits and resolve
any issues. I would like to propose some dates to you for a meeting:
Friday, September 24 morning
Tuesday September, 28 morning
Wednesday, September 29 morning
Hopefully one of these dates would work for you and anyone else from your
office that needs to attend. Please let me know as soon as possible. I
really appreciate your attention to this. Look forward to hearing from you
soon. Thanks.
Jackie Jarrell
[phone] ext.238
[e-mail]
1 of 1 9/13/2004 11:25 AM

SCENARIO FIVE
Archdale Ashley
Space Need 6th East 7th 9th East 9th NW 12th NE 13th NW House Parkview Parker -Lincoln Central Files
% of Total ft2 5,424 3,300 5,024 1,788 3,239 2,050 3,667 4,573 7,187 1,780
TOTAL
38,032
Aquifer Protection Section
Section Chief -- 6
--Groundwater Protection Unit 8
Land Application Permits & Compliance 8
Animal Feeding Operations Permitting 7
Planning Section _
Section Chief 4
Basinwide Planning Unit 7
Classifications & Standards Unit 7
Groundwater Planning Unit 7
Modeling & TMDL Unit 6
Nonpoint Source Planning Unit 8
Surface Water Protection Section
Section Chief 2
Point Source Branch Head 5
Western NPDES Permitting Unit 8
Eastern NPDES Permitting Unit 8
Collection System & Pretreatment 8.
Wetlands & Stormwater Branch Head 5
401 Oversight/Express Permitting 7
Transportation Permitting 6
Stormwater Permitting Unit 7
Program Development 9
NPS Assistance & Compliance Oversight 6
Assistant Director, Personnel,...
Assistant Director's Office 5
Technical Assistance & Certification Unit 9
Information Processing Unit 6
Water Ouality Budget Planning & Analysis
Budget Office 4
Assistant Director RO
Assistant Director's Office 3
Central Flles 2
16.79%
2.96 %
4.72 %
4.86 %
4.24 %
22.83%
2.07%
4.09%
4.09%
4.09%
3.61%
4.86%
40.48%
1.04%
2.63%
4.58%
4.58%
4.72 %
2.63%
4.09%
3.47 %
_ 6,066
_ 1,071
_ 1.706
_ 1,758'
_ 1,531
_ 8,250
_ 749
_ 1,479
1,479
_
0
(0)
(0)
0
(0)
0
0
0
0
(0)
0
0
(0)
(0)
(0)
0
0
0
0
(0)
0
0
(0)
(0)
(0)
(0)
(228)
1,071
1,706
_
1,758
_
1,531
_
_
749
1,479
1,479
1 479
1,479
1,305
1,305
1,758
1,758
14,630
_
_ 374
949
1.654
1,654
1,706
_ 949
1,479
1.253
374
949
1,479
1,253
1.531
949
—
1,654
1,654
1,706
4.24%
5.20%I
3.32%
10.39%
2.70%�
5.06%
2.63%
2.00%
2.00%
1.81%
1.81%
5.71 %
1,531
_ 1,880
_ 1,201
3,754
1,880
1,201
212 y
975
1,828
952
489
274
_
1,828
952
—
723
723
723
653
653
653
2,062
2,290
SUBTOTAL
Conference Room Nood (168 staff w/10 ft2 per) 168
Storage Need (26 units w/100 ft2 per unit)
100.00% 36,138
1,680
2,600
�^
38,260
1,680
2,600
TOTAL
40,418 0 (8)
0
(17)1 210
375
1,186
13
417
(510) 33,980
Square•footage for all available space includes actual circulation square -footage but does not include conference rooms.
This scenario assumes that relevant groundwater files are combined with central files.

J
CHARLOTTE.,
j j ""' :� I'
lj !J .1 [ I
•
August 19, 2004
Jacquelyn M. Nowell
NPDES Unit
Division of Water Quality
North Carolina Department of
Environment and Natural Resources
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
Re: NPDES Permits NCO24945 (Irwin Creek) and
NC0024937 (Sugar Creek)
Dear Ms. Nowell:
L.
•
r •
We are providing this information as a supplement to our July 1, 2004, letter to
Mark McIntire concerning water quality -based effluent limits (WQBELs) for the Irwin
Creek and Sugar Creek wastewater treatment plants ("WWTPs"). This letter sets forth
additional calculations for copper and zinc WQBELs factoring in TSS data -- as reflected
in the WQBEL permitting approach utilized by South Carolina Department of Health and
Environmental Control (DHEC) and identified in the DHEC correspondence from Mr.
Mike Montebello to you (provided to us by e-mail dated July 14, 2004). In light of the
fact that the effect of partitioning on total suspended solids to establish WQBELs for
metals is utilized by DHEC and would not be novel, we request that this approach, which
is also recommended by EPA, be utilized by DENR in the permitting of the Charlotte
Mecklenburg Utility ("CMU") WWTPs. As such, this letter sets forth revised WQBEL
calculations utilizing the TSS partitioning coefficients.
Mr. Montebello notes in his correspondence that, in the absence of actual stream
data, DHEC uses a background TSS of 1 mg/1— which is based on the 5th percentile of
ambient TSS data on South Carolina streams from 1993 — 2000. While we question and
reserve our right to challenge the use of the 5th percentile TSS concentration', as reflected
Mr. Montebello also notes that DHEC uses a hardness of 25 mg/1 in the absence of actual effluent data or
based on the 10th percentile of actual effluent hardness data. To date, we have been unable to ascertain the
basis for using these specified percentiles in addition to the 7Q10 drought stream flow and the design
WWTP flow as the basis for establishing WQBELs. Neither of these approaches is required by applicable
South Carolina regulation or law. This combination of factors yields very restrictive effluent limitations
with a potential for exceedance much more remote than the once in three years upon which the water
quality standards for protection of aquatic life are based.
CHARLOTTE-MECKLENBURG UTILITIES
Environmental Management Division
4000 Westmont Drive
Charlotte, NC 28217
PH: 704/357-1344

by the enclosed calculations, the copper and zinc limits should significantly change such
that it may become a moot issue.
At design flow conditions used for establishing water quality -based effluent
limitations (e.g., WWTP design flow and 7Q10 stream flow), the stream contribution is
relatively minor and the background TSS concentration has little impact. Consistent with
the approach used in the TSD , the below calculations use the mean TSS for the effluent,
particularly in light of the fact that the combination of 7Q10 flow and design WWTP
flow already provides a very high degree of protection. These data are summarized in the
table below.
Statistical Evaluation of DMR TSS Performance Data
July 2001— June 2004
Parameter
Irwin Creek3
Sugar Creek4
Number of Observations
769
766
Mean
2.40 mg/1
2.44 mg/1
The data summarized above indicate that both facilities provide a very high
degree of treatment with average effluent TSS at 2.4 mg/1. The effluent exerts a
significant influence on the instream TSS because both WWTPs discharge to effluent
dominated streams. At drought conditions, the instream waste concentration (IWC) for
the Irwin Creek WWTP is 82.3 percents. The IWC for the Sugar Creek WWTP is 90.1
percents. Even under the DHEC approach where the upstream flow in the receiving
water is assumed to have a background TSS of 1.0 mg/1 (e.g., the 5th percentile TSS
referenced by Mr. Montebello), the TSS after mixing would be 2.15 mg/1 for the Irwin
Creek WWTP and 2.30 mg/1 for the Sugar Creek WWTP.
These TSS concentrations, after mixing under design conditions, were used with
the partitioning coefficients identified in Mr. Montebello's correspondence to you to
2 The Technical Support Document for Water Quality -based Toxics Control (TSD; EPA, 1991)
recommends that secondary parameters, which influence toxicity, be established using EPA's DESCON
model. The model correlates these secondary parameters with flow to meet the once -in -three-year
exceedance frequency allowed by water quality criteria. If flow is not correlated with the secondary
parameter, the model will yield the mean concentration as the most appropriate for use in developing water
quality -based effluent limits.
3 The coefficient of variation, as determined using the delta log -normal statistical method in the TSD, was
0.56 indicating that the effluent TSS is not highly variable.
4 The coefficient of variation, as determined using the delta log -normal statistical method in the TSD, was
0.71 indicating that the effluent TSS is not highly variable.
5 The design conditions for the Irwin Creek WWTP are 15 MGD and 7Q10 = 4.9 cfs.
6 The design conditions for the Sugar Creek WWTP are 20 MGD and 7Q10 = 3.4 cfs.

calculate the dissolved fraction of each metal for use in calculating WQBELs for each
WWTP. The dissolved fractions (FD) for each metal are summarized below.
Dissolved Fractions Calculated from Partition Coefficients
Parameter
Irwin Creek WWTP
Sugar Creek WWTP
Total Suspended Solids
2.15 mg/1
2.30 mg/1
FD (copper)
0.441
0.437
FD (zinc)
0.389
0.385
These dissolved fractions should be used to calculate WQBELs for the total
recoverable forms of copper and zinc. As discussed in our previous letter, the appropriate
hardness for establishing WQBELs for these metals is 85 mg/1 for the Irwin Creek
WWTP and 63 mg/1 for the Sugar Creek WWTP. The appropriate WQBELs based on
these hardness values and dissolved fractions are summarized below.
Water Quality -Based Effluent Limits
Parameter
Irwin Creek
Sugar Creek
Copper
Zinc
Copper
Zinc
7Q10 Flow
4.9 cfs
3.4 cfs
WWTP Flow
15 MGD
20 MGD
Hardness
85 mg/1
63 mg/1
TSS
2.15 mg/1
2.15 mg/1
2.30 mg/1
2.30 mg/1
FD
0.441
0.389
0.437
0.385
WQS (dissolved)
11.53 µg/1
102.1 µg/1
8.70 µg/1
79.2 µg/1
WLA (dissolved)
13.96 µg/1
123.7 µg/1
9.66 µg/1
87.9 µg/1
WQBEL
(total recoverable)
31.6 µg/1
317.5 µg/1
22.1 µg/1
228.4 µg/1
7 The critical condition for TSS partitioning occurs at the 7Q10 flows. As instream flows increase, the
calculated WQBELs would increase.

We hope that this analysis, fully consistent with the preferred WQBEL permitting
approach of DHEC, is helpful for the DENR development of WQBELs for the CMZJ
WWTPs. We will soon be contacting you to arrange a meeting so that we can resolve
any outstanding issues associated with the copper and zinc limits and to assure that
appropriate WQBELs are established.
Sincerely,
(,,,..t. .4.......Lc.. -A t
cqueline A. Jarrell, P.E.
Environmental Management Division Supt.
C: D. Padgett
B. Gullet
file