NC0026441_Speculative Limits_19870210

WDES DOCUMENT SCAMMIM& COVER SHEET
NPDES Permit:
NCO026441
Siler City WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Engineering Alternatives Analysis
201 Facilities Plan
Instream Assessment
Speculative Limits
Permit History
Date Range:
Document Date:
February 10, 1987
THIS DOCUMENT IS PRINTED ON REUSE PAPER - IONORE ANY CONTENT ON THE
REVERSE SIDE

State of North Carolina
Department of Natural Resources and Community Development
Division of Environmental Management
512 North Salisbury Street • Raleigh, North Carolina 27611
1987 10,
James G. Martin, Governor February R. Paul Wilms
S. Thomas Rhodes, Secretary Director
Mr. David T. Upchurch
Hobbs, Upchurch & Associates, P.A.
290 SW Broad Street
Southern Pines, NC 28387
Dear Mr. Upchurch:
As per your request, I am providing you with suggested limits for
the Siler City WWTP if they expand their facility from 1.8 to 3.0 MGD.
Please remember that these are preliminary limits and cannot be regarded
as any assurance of a change in the existing permit. If Siler City wishes
to modify their permit for an expansion to 3.0 MGD, they should submit a
formal application.
The suggested limits are as follows:
Loves Creek
Rocky River
Summer
Winter
Summer
Winter
BOD5
(mg/1)
9
18
8
16
NH
(mg/1)
6
12
5
10
DO
_ (mg/1)
6
6
6
6
TSS
(mg/1)
30
30
30
30
Fecal
Coliform (#/100ml)
1000
1000
1000
1000
pH
(SU)
6-9
6-9
6-9
6-9
Note:
Since the effluent
contains industrial
waste,
there will
also be a
toxicity testing
requirement
added if Siler
City wishes
to amend
their existing permit.
Please feel free to contact me if you have any questions concerning
the above limits.
Sinc ely,
J/J David Vogt
JDV:gh VVV
cc: Ben Shivar, Town Manager, Town of Siler City
Raleigh Regional Office
Dale Overcash
Trevor Clements
Pollution Pwrention Pars
e
PO. Box 27687, Raleigh, North Carolina 27611-7687 lelephone 919-733-7015
An Fmul norm tnoity Affirmative Action Emnl�

Sri V :: ZA 3 ,z 1 3-1-1 3
A �3)
HOBBS, UPCHURCH & ASSOCIATES, P. A.
CONSULTING ENGINEERS
January 119, 1987 M l ii 91!
Mr. Trevor Clements
Water Quality Section ' CHMLA.L $tk�,r•.
Division of Environmental Management
P. 0. Boat 27687
Raieigh, North Carolina 27611.
Re: Upgrading of Waste Treatment Plant
Siler City, North Carolina
Dear Mr. Clements:
The Town of Siler City, North Carolina, presently operates a
1.8 MGD waste treatment plant, Permit No. NC. 0026441., which
discharges into a small stream called Loves Creek. The
discharge point on Loves creex 1s approximately 'L,500 linear
feet upstream of the confluence with Rocky River. The Town of
5iier Citv wishes to upgrade this waste treatment plant to 3.0
MGD with expansion capabilities to 4.0 MGD.
Our firm is presently preparing -preliminary designs and cost
estimates for these improvements. We therefore request A
preliminary waste load allocations for a 3.0 MGD.discharge into
Loves Creek. In addition, because of the close proximity to
oc y River, we request that a preliminary loading model be
performed for a 3.0 MGD discharge on Rocky River just 13.
downstream of Loves tree
We would appreciate any assistance, no matter how preliminary,
you can give us on this project. Thank you.
Sincerei/�y,,
HOBB,Sr U HURCH & AS CI ES, P.A.
David T. Up�rch, P.E.
CC: Mr. Ben Shivar, Town Manager
Mr. Joel Brower, Public Works Director
POST OFFICE BOX 1735
290 SW BROAD STREET SOUTHERN PINES, N.C. 28387 919-692-5616

SV MMer
---------- MODEL RESULTS ----------
Discharger
:
TOWN OF SILER CITY
Receiving Stream :
ROCKY RIVER
The End D.O.
is 5.24
mg/l.
The End CBOD
is 23.69
mg/l.
The End NBOD
-----------------------------------------------------------------------
is 0.00
mg/l.
WLA
WLA
WLA
DO Min
CBOD
NBOD
DO Waste Flow
(mg/1)
Milepoint Reach # (mg/1)
(mg/1)
(mg/1) (mgd)
Segment 1
------
5.08
---------------- ----
1.20 1
----
-- ----------
Reach 1
39
0.00
6.00 3.00000
,1.0
30 DSs
9 . s tj =
39

Su,Kvme✓
*** MODEL SUMMARY DATA ***
Discharger : TOWN OF SILER CITY Subbasin : 03O612
Receiving Stream : ROCKY RIVER Stream Class: C
Summer 701O : 0.5 Winter 7Q1O : 1.
Design Temperature: 25.
:LENGTH: SLOPE! VELOCITY ! DEPTH! KI 1 K1 1 K2 I K2 1 KN I KN 1 KNR 1 KNR
1 mile 1 ft/mil fps t ft (design! 320' Wesignl 820' (design! 220' !design: 1204 1
Segment 1 1 2.021 11.501 0.184 t 1.37 1 0.48 1 0.38 1 4.24 1 3.811 0.00 1 0.00 ! 0.00 0.00 1
Reach 1 1 i 1 1 1 1 1 1 1 t 1 1
1
Flow
1
cfs
Segment 1
Reach
1
Waste
1
4.650
Headwaters:
0.500
Tributary
1
0.000
* Runoff
I
0.000
CSOD 1 NBOD D.O. 1
mg/1 1 mg/1 mg/1
1 39.000 1 0.000 1 6.000
2.000 1 0.000 I 7.560
1 0.000 . 0.000 1 0.000
1 0.000 . 0.000 1 0.000
* Runoff flow is in cfs/mile

w,Je e
--------- MODEL RESULTS
Discharger- : 'TOWN OF SILER CITY
Receiving Stream : ROCKY RIVER
---------------------------------------------
The End D.O.'.is 5.13 mg/l.
The End CBOD is 58.84 mg/l.
The End NBOD is 0.00 mg/l.
-------------------------------------------------
WLA
CBOD
(mg/1)
86
DO Min
(mg/1)' Milepoint Reach #i
Segment 1 5.09 1.60 1
Reach 1
-I- 4 • S- pu "3 = 7 �
(a, X S . M M tr l _ 'a.o O b) + 4, �( 5)
-----------------
WLA
WLA
NBOD
DO Waste Flow
(mg/1)
(mg/1) (mgd)
------------
0.00
6.00 3.00000

*** MODEL SUMMARY DATA ***
w„ ev-
Discharger : TOWN OF SILER CITY Subbasin : 030612
Receiving Stream : ROCKY RIVER Stream Class: C
Summer 7010 : 0.5 Winter 7010 : 1.
Design Temperature: 15.
:L816TH: SLOPE: VELOCITY : DEPTH; K1 : KI : K2 : K2 : KN : KN : KNR : KNR :
: mile : ft/mi: fps : ft design; 320' :design: 120' ;design: 120' ;design; 120'
Segment 1 ; 2.001 11.50: 0.197 : 1.39 ; 0.31 : 0.39 ; 3.66 ; 4.09: 0.00 ; 0.00 : 0.00 : 0.00
Reach 1 : : : : : ; : :
Flow
CBOD :
:
cfs ;
mg/1 :
Segment i
Reach
1
Waste
:
4.650
86.000 ;
Headwaters:
1.000 :
2.000 ;
Tributary
.
0.000 :
0.000 .
w Runoff
1
0.000 :
0.000 :
* Runoff flow is in cfs/mile
NFOD :
D.O. :
mg/l 1
mg/l :
0.000 :
6.000
0.000 :
9.200
0.000 :
0.000
0.000
0.000

SumMe�
---------- MODEL RESULTS
-----------
Discharger
:
TOWN OF SILER CITY
Receiving Stream :
----------------------------------------------------------------------
LOVES CREEK;
The End D.O.
is 5.01
mg/l.
The End CEOD
is 28.35
mg/l.
The End NBOD
---------------------------------------------
is 0.00
mg/l.
-------------------------
WLA
WL.A
WLA
DO Min
CBOD
NBOD
DO
Waste Flow
(mg/1)
------
Milepaint Reach #
----------------
(mg/1)
----
(mg/1)
----
(mg/1)
--
(mgd)
----------
Segment 1
4.96
2.02 2
Reach 1
45
0.00
6.00
3.00000
Reach 2
0
0.00
0.00
0.00000

5VP4ME/`
*** MODEL SUMMARY DATA ***
Discharger : TOWN OF SILER CITY S'ubbasin : 030612
Receiving Stream : LOVES CREEK Stream Class: C
Summer 7Q1O : 0.2 Winter 701O : 0.4
Design Temperature: 25.
:LENGTH; SLOPE; VELOCITY : DEPTH: KI : KI 1 K2 1 K2 : KN : K11 : KNR 1 KNR
: mile : ft/mi: fps 1 ft :design; 1204 ;design; 51204 :design: 1204 !design: Q08
Segment 1 1 0.42; 47.60: 0.581 : 0.75 : 1.01 : 0.80 155.55 1 49.821 0.00 : 0.00 : 0.00 : 0.00 1
Reach 1 1 1: 1 : ; ; : 1
Segment 1 : 2.00: 11.50: 0.184 1 1.37 1 0.48 1 0.38 : 4.25 1 3.811 0.00 ; 0.00 1 0.00 1 0.00 :
Reach 2 : ; ; ; : 1 1 :
Flow 1
CBOD ;
NFOD ;
D.O.
cfs 1
mg/1 ;
mg/i
mg/1
Segment 1
Reach 1
Waste
4.650 :
45.000 1
0.00O :
6.000
Headwaters; 0.200 ;
2.000 ;
0.000 ;
7.560
Tributary
. 0.000 1
0.000 :
0.000 :
0.000
* Runoff
1 0.000 1
0.000 :
0.000 ;
0.000
Segment 1 Reach 2
Waste 1 0.000
Tributary ; 0.300 1
* Runoff ; 0.000 :
0.000 : 0.000 : 0.000
2.000 ; 0.000 1 7.560
0.000 : 0.000 1 0.000
* Runoff flow is in cfs/mile

U)%
---------- MODEL RESULTS ----------
Discharger
:
TOWN OF SILER CITY
Receiving Stream :
---------------------------------------------------------------------------
LOVES CREEK
The End D.O.
is 5.05
mg/l.
The End CBOD
is 62.53
mg/l.
The End NBOD
----------------------------------------------------------------------
is 0.00
mg/l.
WLA
WLA
WLA
DO Min
CBOD
NBOD
DO
Waste Flow
(mg/1)
Milepoint Reach #
(frig/1)
(mg/1)
(mg/1)
(mgd)
Segment 1
------
5.05
----------------
2.42 2
----
----
--
----------
Reach 1
94
0.00
6.00
3.00000
Reach 2
0
0.00
0.00
0.00000
a K S Lj.M vti o f =
UNN3

w',Jtr
*** MODEL SUMMARY DATA ***
Discharger : TOWN OF SILER CITY Subbasin : 030612
Receiving Stream : LOVES CREEK Stream Class: C
Summer 701O : 0.2 Winter 7Q1O : 0.4
Design Temperature: 15.
;LENGTH: SLOPE; VELOCITY ; DEPTH! K1 : Kl : K2 1 K2 : KN : KN : KNR 1 KNR 1
1 mile : ft/mi: fps ; ft !design: 320' :design! 220' !design! 820' :design! 120' :
Segment 1 : 0.42: 47.601 0.599 1 0.75 ! 0.65 : 0.02 :44.85 1 50.00: 0.00 1 0.00 ; 0.00 : 0.00
Reach 1 1 1 1 : 1 1 : : : 1 : :
Segment 1 1 2.001 11.50: 0.198 1 1.38 : 0.31 1 0.39 1 3.67 1 4.09: 0.00 : 0.00 ; 0.00 1 0.00 1
Reach 2: 1 1 : : : 1 1 1 :
:
Flow 1
CDOD
; NBOD ;
D.D. :
cfs
mg/1
mg/1 :
mg/1
Segment 1
Reach 1
Waste
;
4.650 1
94.000
1 0.000 1
6.000
Headwaters:
0.400 ;
2.000
: 0.000 ;
9.200
Tributary
1
0.000
0.000
0.000
0.000
* Runoff
;
0.000 :
0.000
; 0.000 1
0.000
Segment 1
Reach
2
Waste
1
0.000 :
0.000
1 O.000 !
O.000
Tributary
:
0.600 ;
2.000
: 0.000 :
9.200
* Runoff
;
0.000 1
0.000
: 0.000 ;
O.O00
* Runoff flaw is in cfs/mile

Tritor
Screen
6K(5 e Wu'l
To Loves Creek
Aeration
Pump
JH
Station #2
F-I
Basins
Control
Post
Building
Aerati�
Grit Parshall Flow
Chamber Flume Junct
Equalization Pump
Racin Shatinn 41'
tter
Box
#1
Secondary N
�j Clarifiers
G�NrXC/S�Z�� #2
0'
i.trifica-
tion Basin
#1
Chlorine
Contact
Final
Clarifiers
#2
F. Schematic of Wastewater:,Flow ' C ;RAM
Town of Siler City
Wastewater Treatment Facility
Siler City, Chatham County,"N. C.
NPDES No. NCO026441 May 16,'1986

m.'�
DESIGN DATA
FOR
UPGRADING THE TOWN OF SILER CITY'S
.EXISTING 1.80 MGD WASTEWATER TREATMENT PLANT
CHATHAM COUNTY,
NORTH CAROLINA

PLAN AND SPECIFICATION REVIEW
SKETCH OF ELIGIBLE PROJECT
Page 2 of
Date
Sketch of eligible project (Include number and types of process units, sewer
stationing, receiving stream, etc.)
I1 1:% 16 r
II S=REEN
L aNJ
AEKATED
Q 0 1 L J TAT) 0 PJ 6piT 6H4MBER
BASIN
PA R:5 H A, L L
FLJMC
Su NGTIoH
BOIL
PUMP
WA4re 3�V AGE
EL
E 'Y� ,:5 - t5 C1 -.7
R
PUMP
-,-,
rump A SL u D
?AITP �,J I CATI� N
T)
PQA9
N A GENERAL H E M AT!
C- L FJ, I F 11 F L o
TOW N I L'r
CL, SToftr CHL Z, E.
Ife i C)
CON T Pb L- U-
A G -ri 0 0
L- 0 v E s P, E. E K

F:=
1. EXISTING AERATION BASIN.
a. Two tanks, each 61' x 137' x 15'
Total cubic feet of existing aeration basin =
2 x 61 x 137 x 15 = 250,710 cu. ft.
b. Volume of existing settling tanks to be converted to aeration
28' x 60' x 11' x (2 tanks) = 36,960 cu. ft.
C. Total volume to be used for aeration =
287,670 cu. ft. x 7.48 = 2,151,770 gallons
d. Total flow thru basin =
Design flow = 1.80 MGD (from flow equalization)
Recirculation = 50%
e. Detention time =
2,151,770 Gal(24) = 19.13 hrs.
2,700,000 Gal Includes 50% Recirculation
f. Pumps followine aeration basin to Dump water to secondary clarifiers:
(1) Use two (2) 1900 GPM pumps
(2) Space for future 950 GPM pump
2. SECONDARY CLARIFIERS (Following Aeration Basin)
Flow: 2.70 MGD, arrived at as follows:
Average flow = 1.80 MGD
Recirculation @ 50% _ .90 MGD
Total 2.70 MGD `Z
v�
Use 2 Clarifiers (1.35 MGD to each unit)
?cn
`4 J
'[[ 1

11
2. SECONDARY CLARIFIERS (Continued)
Assume: a. Surface settling rate = 500 GPD/Ft2
b. Detention time = 4 hrs.
Surface Area Required = 1,350,000 = 2700 Ft2
500
Volume based on 4 hrs. detention = 1,350,000 x 4 = 30,080 Ft3
7.48 x 24
Depth = 30 080 Ft3
270� = 11.14 Ft.
Assuming circular design, radius = sq. root of 2700 = 29.32 Ft.
3.14
Therefore, use 60' Diameter Circular Clarifiers
Weir Loading Rate =. 1,350,000 = 7,162 Gal/Ft
3.14 x 60
Summary: Use 2 Secondary Clarifiers
Each 60' in Diameter with 11.14 feet of water depth.
3. NITRIFICATION BASIN
Given: Two (2) tanks -.0.90 MGD thru each basin
Avg. NH3 N = 30 mg/1
Min. Temp. = 10' C.
Operating pH = 7.5
MLVSS Concentration = 1,500 mg/l
Taken From EPA "Nitrification and Denitrification Facilities", Oct., 1971
a. NH3 Load"
� J
(1) Avg. = .9(8.34) (30) = 225.18 lb/dayi�`7
(2) Maximum = 225.18 x 1.5 = 337.77 lb/da}(��

3. NITRIFICATION BASIN (Continued)
b. Tank Volume @ 10' C., MLVSS = 1,500 mg/l
(1) From Fig. 6-3, Vol. Loading = 8.2 lb/1000 Ft.3
(2) Tank Volume = 337.77 x 1000 = 41,191.46 Ft.3
8.2
C. Tank Volume adjusted to pH 7.8 (Fig. 6-4
41,191.5 = 55,664 Ft3
.74'
d. Detention Time = 55,664 x 24 x 7.48 = 9.99 hrs.
1,000,000
Therefore, Detention Time = 10.0 Hours
e. .Assuming @ 13 Ft. Water Depth, each tank requires: --
55;664'Ft3=.'4282 sq ft.--for. a.'total of 8,564 sq 'ft..for
13 Ft'
1.80 MGD: _ Use 38 x.113'; 4294 Ft:2
4. FINAL CLARIFIERS
5 Following Nitrification Basin:
Same criteria as SECONDARY CLARIFIERS. Therefore use 2 - 60'
Diameter Clarifiers.
5. CHLORINE CONTACT TANK
Assume 30 min. detention, and flow .of 1.80 MGD
Volume = 30 x 1,800,000 = 37,500 gallons `v 47
60 x24 \�
Cu. Ft. = 5,013, assuming a 10' Water Depth, need 501.3 Sq. t C
surface area. Therefore use 22.5' x 22.5' x 10'�, WD-i�N�� N

r
6. POST AERATION
Assume 30 Min. detention, therefore, same size as Chlorine Contact Tank.
Use 22.5' x 22.5' x 10' WD
7. AIR REQUIREMENTS
a. Flow Equalization - 500,000 Gal. Capacity
Aeration is to be provided in flow equalization basin for blending of
the wastewater, to prevent solids from settling, and to prevent the
wastewater from becoming septic. Mixing requirements are 0.03 HP per
1000 gallons of storage and Air Requirements are 2 Ft.3/min. per -
1000 gallons of storage.
Therefore, need 0.03(500,000) = 15 HP of floating aerators for mixing
1000
and 2 ,(500,000) = 1000 CFM of air. Therefore approximately 29.4 HP -of
`1000
floating aerators�is. required 'for 'air requirements.--
Total HP = 15 + 29.4 = 44 4,` therefore 45 HP in floating aerators` "
b. 'Extended.Aeration Basing-
(1) Organic loading, influent to basin = 300 mg/l BOD
BODS loading = 300 (8.34)(1.8).= 4504 lb/day
Lb. 02/day required = 4504 (1.0) = 4504
Blower capacity assuming 2000 cu. ft. of air per. lb. BOD =
4504(2000) = 6250 cu. ft./min
24 x 60
(2) There are presently 2 - 2500 CFM blowers and 1 - 1250 CFM blower
for a total rated capacity of 6,250 CFM. It is
an additional 2500 CFM blower be installed.

I
I,
l ,•
7. AIR REQUIREMENTS.( Continued)
C. Nitrification Basin - Assuming influent NH3 = 30 mg/1
NH3 load = 1.8 (8.34)(30) = 450 lb!_ay
(1) Maximum NH3 load = 450 (1.5) = 676 lb/day
(2) BOD load = 1.8 (8.34)(30) = 450 lb/day
(3) Oxygen required for NH3 oxidation = 676 x 4.6 = 3110
lb/day
(4) Oxygen required for BOD reduction = 450 x 1 • = 450
lb/day
Total 3560
lb/day
Assuming actual oxygen transfer rate is 2 lb/HP-hr, need
3560 lh (HP-hr) day = 74 HP
day(2 lb) 24 hrs.
Therefore, install 80 HP of floating aerators.
8.,`AEROBIC .SLUDGE DIGESTER:'
Assuming 0 15r1b. sludge. produced':for each`lb ,of-,BOD-r'educed, the
quantity of sludge is:
`z
300 x 8; 4 x l:?8 .15 = 675.5 lb.
r
€
Assuming a solids concentration of 0_75% in.the waste sludge, .
675.5 =. 1443'cu. ft. of ,waste sludge is produced'.per
day.,
3
62.4(.0075)
-
_
Using 15 days storage time for digester storage capacity,
1443(15) _
21,650,cu: ft. is required. This is the equivalent .of
21,650 = 1.2 cu. ft. per capita
18,000
Using 2 units, 10,825 cu. ft. is required for each digester. Assuming
12 ft. liquid depth, 10,825 = 902 sq. ft. of surface ftoY
12 rGl. 0
S,•, sh e�5

a
8. AEROBIC SLUDGE DIGESTER (Continued)
Using a circular tank, the radius equals the square root of 902 = 17 Ft.
3. 14
Therefore, use two (2) 34' diameter aerobic sludge digesters.
9. CONTROL BUILDING.
The Control Building will house the following functions:
A. General Office Space.
B. Laboratory Facilities.
C. Plant Instrumentation and Controls
D. Storage and Generator.
E- Recirculation Pumps and Piping
10. � FLOW EQUALIZATION.
It was recommended'in the Siler City 201,Facilities. Plan that,a'li0 million.
.:gallon flow equalization basin be installed at'tHis.plant. This was 'sized,7,_
as such,`'due to.the peak flows caused in part by some -of the industrial dis-
charges. However, since the Plan was approved, the two (2) significant
industries made known their plans to discharge their wastes more uniformly:
'This, therefore, is sufficient cause to.'re'duce.the volume of the equaliza-.
tion basin to 0.50.million gallons. The basin will be a'concrete lined
earth basin with 2:1 side slopes, three.(3) feet. of free board, and four
(4) feet constant bottom storage to prevent scouring. The overall dimen-
sions .are as,follows: at top _ 77'_ x 200'; at bottom - 17' x 140'; at 4 Ft.
constant storage level - 33' x 156'; water level - 65' x 188'. This yields
a net storage volume of 504,600 gallons.
N�gg1

Page 4 of
Date
Project - DESIM CRITERIA
1. Scope of project:
Check if included in this contract
( ) a. Interceptor or outfall sewers .
( ) b. Pump station(s) and force main(s)
c. Wastewater treatment facilities
( ) d. Other
2.
Project loading::..
µ
Average Flow "
At Present Time
In Design Year (1925)
a.
Industrial flow
_mgd
d
mgd
Domestic flow.
60—Mgd
n�
G
mgd
Total .flow
1D,
I®•:. mgd
1. �D
mgd
b:
.Indust=ial BOD
PPm„
pr°! >:..
Dor,:estic BOD
JR�V PPm
pFm
Total BOD..
ppm
'.
`. C.
Industrial susp.
solids
PPm
{.
Domestic susp.
solids
pom
Total susp• r
solids PP--p ,m
3. Principal types of Industrial wastes: U'n `�'_-� ��r'c r•t V.
4. Decree of treatment:
A present
Removal time
a. BOD �8 %
b Suspended
solids. 8� %
Initially/
after project
9 S -f- %

PLAN AND SPECIFICATION REVIEW
SKETCH OF ELIGIBLE PROJECT
Page 2 of
Date
Sketch O2 eligible Project (lnclU,�e nUGlJer a � types Of Process Units, SeYler
stationing, receiving stream, etc.)
JpN�yyl �.
k
��r
s
a.

PLANS AND SPECIFICATIONS REVIEW
Page 1 of
Date
Project No. ;Gl 2 /-Gj NPDL-S Permit No.
Applicant 1 P�-, F GiL- C^ J V v
Design Engineer '•`'� r _ : ! :.i,:^
J
Project VJs^"c`Y� t •( l (� J C� _ G 1 _I�-f i
Contract I. D.
Est. Construction Contract Amounts)
Approval by State Engineer" Date
Conditions for Approval (attach copy of certification letter and plan
and specification approval letter )
Description of project in terms of type of treatment, flow capacity; and process units: