NC0087645_Speculative Limits_20080729

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July 29, 2008
The Honorable Walter Lea Thomas IV, Mayor
Town of Milton
P.O. Box 85
Milton, North Carolina 27305
Dear Mayor Thomas:
Michael F. Easley, Governor
State of North Carolina
William G. Ross, Jr., Secretary
Department of Environment and Natural Resources
Coleen H. Sullins, Director
Division of Water Quality
Subject: Speculative Limits for Milton WWTP
NPDES Permit No. NCO087645
Caswell County
This letter is in response to the request for speculative effluent limits for a proposed expansion
of the Milton WWTP from 0.025 MGD to 0.035 and 0.050 MGD. Mr. David L. Honeycutt of
Dewberry & Davis, Inc. submitted this request to our office on your behalf. In April2002, the
Division of Water Quality (DWQ) provided speculative limits to the Town for 0.050 MGD. The
speculative limits given at that time remain the same with the inclusion of summer weekly
average limits for NH3-N. Speculative limits for 0.035 MGD are now included in this letter.
ReceivingStream. tream. The speculative request was for the expansion of Milton's discharge at its
existing location into Country Line Creek. Country Line Creek is classified as a C waterbody in
the Roanoke River Basin. The best usage of these waters includes aquatic life propagation and
maintenance of biological integrity, wildlife, secondary recreation, and agriculture.
The current Milton WWTP discharge point in Country Line Creek has a drainage area of 137.5
square miles, with an estimated average flow of 124 cfs; a summer 7Q10 flow of 0.7 cfs and a
winter 7Q10 flow of 6 cfs. Country Line Creek is a tributary to a segment of the Dan River,
located in the Commonwealth of Virginia.
Speculative Limits. Based on current available information, speculative effluent limits for the
discharge at an expansion flow of 0.035 MGD are presented in Table 1. Speculative limits for an
expansion flow of 0.050 MGD are presented in Table 2. .
A complete evaluation of these limits and monitoring frequencies, in addition to monitoring
requirements for metals and other toxicants, will be addressed upon receipt of a formal NPDES
permit request. The recommended summer limits for ammonia (NH3-N) are calculated to
protect against toxicity instream.
The following procedure has been recently implemented by the Division of Water Quality
(DWQ): Total residual chlorine (TRC) compliance level changed to 50 ug/l. Effective March 1,
2008, the Division received EPA approval to allow a 50 ug/1 TRC compliance level. This change
is due to analytical difficulties with TRC measurements. Facilities will still be required to report
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone [phone] FAX [phone] Nopp" e Carolina
512 N. Salisbury Street, Raleigh, North Carolina 27604 On the Internet at http://h2o.enr.state.nc.us/tllrQ!!�
An Equal Opportunity/Affirmative Adon Employer

Letter to Mayor Thomas
page 2
actual results on their monthly discharge monitoring report (DMR) submittals, but for
compliance purposes, all TRC values reported below 50 ug/l will be considered to be in
compliance with the permit. The permittee shall continue to record and submit all values
reported by a North Carolina certified laboratory (including field certified), even if these values
fall below 50 ug/l.
TABLE 1. Speculative Limits for Milton WWTP at 0.035 MGD
Effluent Characteristic
Effluent Limitations
Monthly
Average
Weekly Average
Daily Maximum
Flow
0.035 MGD
BOD5
30 m /L
45 m /L
NH3 as N (summer)
11.5 m /L
34.5 m /L
NH3 as N (winter)
Monitor only
TSS
30 m /L
45 m /L
Total Residual Chlorine
28 u /L
H
6.0 - 9.0 S.U.
Fecal coliform (geometric
mean)
200/100 mL
400/100 mL
TABLE 2. Speculative Limits for Milton WWTP at 0.050 MGD
Effluent Characteristic
Effluent Limitations
Monthly
Average
Weekly Average
Daily Maximum
Flow
0.050 MGD
BOD5
30 m /L
45 m /L
NH3 as N (summer)
5.9 m /L
17.7 m /L
NH3 as N (winter)
Monitor only
TSS
30 m /L
45 m /L
Total Residual Chlorine
28 u /L
H
6.0 - 9.0 S.U.
Fecal coliform (geometric
mean)
200/100 mL
400/100 mL
Engineering Alternatives Analysis-(EAA). 'Please note that the Division cannot .guarantee that
an NPDES permit modification for an expansion will be issued with these speculative limits.
Final decisions can only be made after the Division receives and evaluates a formal permit
application for the Town's proposed expansion. In accordance with the North Carolina General
Statutes, the practicable wastewater treatment and disposal alternative with the least adverse
impact on the environment is required to be implemented. Therefore, as a component of all
NPDES permit applications for new or expanding flow, a detailed engineering alternatives
analysis (EAA) must be prepared. The EAA must justify requested flows, and provide an
analysis of potential wastewater treatment alternatives. Alternatives to a surface water
2

Letter to Mayor Thomas
page 3
discharge, such as spray/drip irrigation, wastewater reuse, or inflow/infiltration reduction, are
considered to be environmentally preferable. A copy of the EAA guidance document is
attached to this letter. Permit applications for new or expanding flow will be returned as
incomplete if all EAA requirements are not adequately addressed. If you have any questions
regarding these requirements, please contact the DWQ NPDES Program at 919-807-6300.
The fee schedule for NPDES permits has changed as of September 1, 2007. Application fees for
this major modification will be $260 should the Town pursue this expansion. If you have any
questions about these speculative limits or NPDES permitting requirements, please feel free to
contact Jackie Nowell at [phone].
Respe y,
Susan A. Wilson, P.E.
Supervisor, Western NPDES Program
Attachment: EAA Guidance Document
cc: (without Attachment)
U.S. Fish and Wildlife Service, Ecological Services, PO Box 33726, Raleigh, NC 27636-3726
Attn: Sara Myers
Doug Holmes, EIT/Dewberry & Davis, 551 Piney Forest Road Danville, Va. 24543-1509
Winston Salem Regional Office/Surface Water Protection Supervisor
Dan Blaisdell/ Construction Grants and Loans
Central Files
NPDES Permit File
PERCS Unit
3

Town of Milton WWTP
Spec request for 0.035 MGD and 0.050 MGD
Country Line Creek 030204
Roanoke River Basin
jnm
Facility is requesting spec limits for above flows. Currently permitted for 0.025 MGD
w/ existing limits of BOD5=30 mg/l, NH3 = 15 mg/l, no DO limit. ATC issued in May
2007. Facility is not built yet (per 7/1/2008 plant inspection report).
A letter for flow reduction approval was issued by PERCS in November 2007. Evidently
just a little over 23,000 GPD is permitted out to the current service area. With a design
flow of 25,000 GPD, Town is already at 92% of design capacity and has not been built
yet. Per plant inspection report of 7/l/2008, Town is "working to increase the capacity
of the plant design". Will require a major mod of the permit and a new ATC".
Milton requested spec limits in April 2002 for 0.050 MGD. Level B model results at
that time indicated secondary BOD5 limits would be protective of the instream DO
standard, however NH3 limits were needed for protection against ammonia toxicity.
Limits for 0.050 MGD given in the 2002 spec letter will be reassigned with the inclusion
of a weekly average limit for NH3. At the lower flow of 0.035 MGD, it is assumed that
BOD limits of 30 mg/l will protect, and NH3 tox limits will be given for this flow.
Recommended spec limits:
0.050 MGD
BOD5= 30 mg/l;
summer NH3 r 5.9 mg/l (mo. avg.); 17.7 mg/l (wkly avg.)
winter NH3 monitoring only
TRC = 28 ug/l
0.035 MGD
BOD5= 30 mg/l;
summer NH3 = 11.5 mg/1(mo. avg.); 34.5 mg/l (wkly avg.)
winter NH3 monitoring only
TRC = 28 ug/1

551 Piney Forest Road 434 797 4497
Danville, Virginia 24540-3353 434 797 4341 fax
IN'Dewberry° P.O. Box 1509 •Danville, Virginia 24543-1509 www.dewbertycom
July 10, 2008
�C�Ob�
Karen Rust JUL 14 2008 D
Division of Water Quality - NPDES Unit I
1617 Mail Service Center DENR - WATER DUALITY
Raleigh, NC 27699 POINT sNlRrr o,,..,_..
Re: Milton, NC — WWTP Speculative Limits
To Karen Rust:
This letter is written to request speculative permit limits for the Town of Milton
Wastewater Treatment Plant. The plant's current permit (NC0087645) became effective
September 1, 2007 and expires on May 31, 2012. The current permit is for a 0.025 MGD
facility. We request speculative permit limits for a possible expansion to 0.035 MGD and
also to 0.05 MGD. The discharge location would remain unchanged.
Sincerely,
Dewberry & Davis, Inc.
Q�
Doug Holmes, EIT
Project Engineer
DAH/dah/chn
cc: Jenny Graznak, NC DENR
Ken Pohlig, Division of Water Quality
Amanda Bader, Dewberry
P:\50000941\Hdmin\Correspondence\Milton Speculative Limits Rcquest.docx
Dewberry & Davis, Inc.

Milton WWTP @ 0.035 MGD
Residual Chlorine
Ammonia as NH3
(summer)
7Q10 (CFS)
0.73
7Q10 (CFS)
0.73
DESIGN FLOW (MGD)
0.035
DESIGN FLOW (MGD)
0.035
DESIGN FLOW (CFS)
0.05425
DESIGN FLOW (CFS)
0.05425
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
UPS BACKGROUND LEVEL (t
0
UPS BACKGROUND LEVEL
0.22
IWC (%)
6.92
IWC (%)
6.92
Allowable Concentration (ugi
245.76
Allowable Concentration (m
11.50
Ammonia as NH3
(winter)
7Q10 (CFS)
6.19
Fecal Limit
2001100ml
DESIGN FLOW (MGD)
0.035
Ratio of 13.5 :1
DESIGN FLOW (CFS)
0.05425
STREAM STD (MG/L)
1.8
UPS BACKGROUND LEVEL
0.22
IWC (%)
0.87
Allowable Concentration (m
182.08
NC0087645 7/23/2008

proposed Milton WWTP
L c) o ' v Ili (;-"
Residual Chlorine
Ammonia as NH3
(summer)
7Q10 (CFS)
0.73
7Q10 (CFS)
0.73
DESIGN FLOW (MGD)
0.05
DESIGN FLOW (MGD)
0.05
DESIGN FLOW (CFS)
0.0775
DESIGN FLOW (CFS)
0.0775
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
UPS BACKGROUND LEVEL (U
0
UPS BACKGROUND LEVEL
0.48
IWC (%)
9.60
IWC (%)
9.60
Allowable Concentration (ug/
177.13
Allowable Concentration (m
5.90
Ammonia as NH3
(winter)
7Q10 (CFS)
6.19
Fecal Limit
200/100ml
DESIGN FLOW (MGD)
0.05
Ratio of 9.4 :1
DESIGN FLOW (CFS)
0.0775
STREAM STD (MG/L)
1.8
UPS BACKGROUND LEVEL
0.22
IWC (%)
1.24
Allowable Concentration (m
128.00
3/14/02

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SUMMER,
MODEL FOR PROP. MILTON WWTP
BOD5=30, NH3=5.9 FOR TOXICITY
---------- MODEL RESULTS ----------
Discharger : TOWN OF MILTON
Receiving Stream : COUNTRY LINE CREEK
------------------------------------------------------------
The End D.O. is 7.46 mg/l.
The End CBOD is 1.97 mg/l.
The EndNBODis0_97
- - - ---------------------------------------------------
WLA
WLA
WLA
DO Min CBOD
NBOD
DO
Waste Flow
. (mg/1) Milepoint Reach # (mg/1)
(mg/1)
(mg/1)
. .(mgd)
- --
Segment 1
5.30 1.90 2
45.00
26.55
0.00
0.05000
Reach 1
0.00
0.00
0.00
0.00000
Reach 2
.0.00
0.00
0.00
0.00000
Reach 3

F
r'
r
*** MODEL SUMMARY DATA ***,
/eceiving
arger : TOWN OF MILTON Subbasin 030204,
Stream : COUNTRY LINE CREEK Stream Class: C
r 7Q10 : 0.7 Winter 7Q10 6.2
'Design Temperature: 25.0
SLOP
VELfPCsTY
DftTHldesignl
Kd
Ka
Ka
------------
ILmileHl
--------------------------------------------------------------------
ft/mEl
I
@20°
Idesigni
@20°
Idesignl
Segment
1
I 1.30)
3.70I
0.100
10.73
10.27 10.22
10.74 I
0.67I
0.44
Reach
--------------------------------------------------------------------------------
1
Segment
1
I 0.60I
1.80I
0.100 TI
0.73
10.27 10.21
10.36 I
0.32I
0.44
Reach
--------------------------------------------------------------------------------
2
Segment
1
I 1.00I
1.80I
0.910 15.70
10.27 10.22
11.61 I
1.441
0.44
Reach 3
Flow
cf s
Segment 1 Reach 1
Waste 0.077
Headwaters 0.730
Tributary 0.000
* Runoff 0.000
Segment 1 Reach 2
CBOD I NBOD I D.O.
mg/1 mg/1 mg/1
45.000
26.550
0.000
2.000
1.000
7.440
2.000
1.000
7.440
2.000
1.000
7.440
Waste
0.000
0.000
0.000
0.000
Tributary
0.000
2.000
1.000
7.440
* Runoff
0.000
2.000
1.000
7.440
Segment 1
Reach 3
Waste
0.000
0.000
0.000
0.000
Tributary
442.000
2.000
1.000
7.440
* Runoff
0.000
2.000
1.000
7.440
* Runoff flow is in cfs/mile

Seg #
Reach #
Seg Mi
D.O.
CBOD
1
1
0.00
6.73
6.13
4u
1
1
0.10
6.61
6.03
1
1
0.20
6.49
5.93
1
1
0.30
6-.39
5.83
1
1
0.40
6.30
5.73
1
1
0.50
6.21
5.64
1
1
0.60
6.13
5.54
1
1
0.70
6.06
5.45
1
1
0.80
6.00
5.36
1
1
0.90
5.94
5.27
1
1
1.00
5.88
5.18
1
1
1.10
5.84
5.10
1
1
1.20
5.80
5.01
1
1
1.30
5.76
4.93
1
2
1.30
5.76
4.93
1
2
1.36
5.70
4.88
1
2
1.42
5.65
4.83
1
2
1.48
5.60
4.79
1
2
1.54
5.55
4.74
1
2
1.60
5.51
4.69
1
2
1.66
5.46-
4.65
1
2
1.72
5.42
4.60
1
2
1.78
5.38
4.56
1
2
1.84
5.34
4.51
1
2
1..90
5.30
4.47
1
3
1.90
7.44
2.00
1
3
2.00
7.44
2.00
1
3
2.10
7.44
2.00
1
3
2.20
7.44
1.99
1
3
2.30
7.45
1.99
1
3
2.40
7.45
1.99
1
3
2.50
7.45
1.98
1
3
2.60
7.45
1.98
1
3
2.70
7.45
1.98
1
3
2.80
7.46
1.97
1
3
2.90
7.46
1.97
Seg #
Reach #
Seg Mi
D.O.
CBOD
y
SUMMER
MODEL FOR PROP. MILTON WWTP
BOD5=3.0, NH3=5.9 FOR TOXICITY
NBOD
Flow
3.45
0.81
3.36
0.81
3.27
0.81
3.18
0.81
3.10
0.81
3.02
0.81
2.94
0.81
2.86
0.81
2.78
0.81
2.71
0.81
2.64
0.81
2.57
0.81
2.50
0.81
2.43
0.81
2.43
0.81
2.39
0.81
2.35
0.81
2.32
0.81
2.28
'0.81
2.24
0.81
2.21
0.81
2.17
0.81
2.14
0.81
2.10
0.81
2.07
0.81
1.00
442.81
1.00
442.81
1.00
442.81
0.99
442.81
0.99
442.81
0.99
442.81
0.98
442.81
0.98
442.81
0.98
442.81
0.98
442.81
0.97
442.81
NBOD
Flow