HomeMy WebLinkAboutNC0021849_Instream Assessment_19880429G�r-o o3orsz
DIVISION OF ENVIRONMENTAL MANAGEMENT
April 29, 1988
MEMORANDUM
TO: Jim Mulligan
L
THROUGH: Trevor Clemens
Steve Tedder
FROM: Thomas Stockton'(
SUBJECT: Town of Hertford 67B Instream Assessment
NPDES No. NCO033618
Perquimans County
Summary and Conclusions
An assessment has been completed by Technical Support to determine the impact
on the Perquimans River of an additional 0.0194 mgd of oxygen -consuming waste-
water from the Hertford WWTP. The Hertford WWTP discharges to a channel approxi-
mately 1600 feet long that directs effluent flow to the Perquimans River. The
channel is obstructed by vegetation including sizeable trees. Modeled as a
direct discharge to the Perquimans River the Pre JOC wasteflow (0.2928 mgd) is
predicted to result in a D.O. sag of 0.60 mg/l. The additional wasteflow is pre-
dicted to result in a cumulative D.O. sag of 0.64 mg/l. This additional depres-
sion of 0.04 mg/l is not considered significant by the EMC criteria for evaivaL-
ing 67B requests. Actual impact is expected to be less due to the treatment pro-
vided by the effluent channel. A "significant impact" of an additional 0.5 mg/1
sag is not predicted to occur at a wasteflow less than 0.54 mgd.
Analysis and Results
This analysis was performed using the DEM Level B estuary model. Suggested
JOC limits for the facility are 40 mg/l BODE, with no NH:, or D.O. limit. The
assessment was performed with a pre JOC flow of 0.2928 mgd, calculated as the
average flow from February 1987 to January 1988, and a current JOC flow of 0.3122
mgd. Analysis was also performed to determine the flow at which a "significant
impact" would be predicted. The Perquimans River was assumed to be 5 feet deep with
an effective width of 500 feet. The freshwater flow into the system was 0.0 cfs
and a dispersion coefficient of 0.10 mil/day was used. Reaction rates were
calculated with standard Level B estuary modeling equations.
The D.O. minimum is predicted to occur at the outfall. The wasteflow at
which a significant impact is predicted is 0.54 mgd. Modeling results are
attached and a summary table is provided below.
Scenario Wasteflow
Pre JOC 0.2928
Requested JOC 0.3122
Maximum Allowable 0.5400
cc. Kent Wiggins
George Everett
D.O. Minimum
6.57
6.53
6.07
4011000-N
4010
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_ 5.0
i \ (ine}
f �� ....
Cem > t_ `tio-
CeAls
— . �'.�..>- 1 I'np{er 7f�uyoy o ,y \ { •�� .11, • � r � 1• . 1719
:.i7.5
�t,,\ - -� rl�� _ Yj �` .-. y ^ _ - ... - - _ --fir ,'_ �� � y - '\ •, i' .
il�wrP — - `/ l{
12'30" ';1�'.', .. ;.' _ - _. - _ _. _ _ Trailer
�4 ,/•. ` _. _ _ ^ Y _ �- t\ '� - .� �. Park
BM
4007
Water]
Trailer Tank
Park
\ y , Bear Garden `
_ Point 3
` • yir' 4C r"tk Ferry
400E -- /./` -- - - - / `mil I �_ __1' T
TBs ST'1
u2 - .i,: o_.� hPau �� /,•'•(�� Crow C i.
.nU�R/H �: , Point
Jennle� I
Discharger:
Water Body:
Wasteflow:
BOD5:
NH3-N:
CBOD/BOD5:
Tidal (Y,N):
Tide data (Y,N):
Net inflow:
Depth:
Width:
Hertford WWTP
Perquimans River
0.2928 mgd
40 mg/l
20 mg/1
1.5
Y
N
0.000 cfs
5.0 ft
500.00 ft
Design: 0.4000 mgd
Pre SOC: 0.2928 mgd
SOC: 0.0194 mgd
Post SOC: 0.3122 mgd
Ambient
Data
____________
CBOD:
2.00
mg/l
NH3-N:
0.50
mg/l
DO:
7.17
mg/l
Temp:
29
»C
Salinity:
10
ppt
DO Sat:
7.28
mg/l
90% Sati
6.55
mg/]
CBOD
decay (Kd):
0.534
May @ 29»C
NH3-N
decay (Kn):
0.534
/dey @ R90C
Advec velocity:
0.003
mpd
Reareation
(Ka):
0.400
/day @ 290C (O'
' Estuarine number:
6074
Dispersion
(E):
0.100
mie/d
-----------------------------------------------------------------
Components
of the
deficit
CBOD
NH3-N
DO
DO Deficit
CBOD
N8OD
Milept
______
(mg/1)
______
(mg/1)
______
(mg/1)
______
(mg/1)
_________
(mg/1)
_______
(Mg/1)
______
outfall
0.38
0.13
0.0
0.88
0.13
6.57
0.60
0.24
0.36
0.1
0.30
0.10
6.59
0.58
0.23
0.35
0.2
0.24
0.08
6.62
0.55
0-22
0.33
0.3
0.19
0.06
6.66
0.51
0.20
0.31
0.4
0.15
0.05
6'70
0.47
0'19
0'28
0.5
0.12
0.04
6.75
0.42
0.17
0.25
0.6
0.09
0.03
6.80
0.37
0'15
0.22
0.7
0.08
0.03
6,84
0-33
0'13
0.20
0.8
0.06
0.02
6.88
0.29
0.12
0.17
Discharger:
Hertford
WWTP
Design:
0.4000
mgc}
'�--- - -'Water'Body:
Merquimans-'Ri,or
'
- Pre SOC:
0-2928
mgd
Wasteflow:
0.3122
mgd
SOC:
0'0194
mgd
BOD5:
40
mg/l
Post SOC:
0.3122
mgd
NH3-N:
20
mg/l
CBOD/BOD5:
1.5
Ambient Data
Tidal (Y,N):
Y
--------------
CBOD:
2.00
mg/l
Tide data (Y,N):
N
NH3-N:
0.50
mg/l
Net inflow:
0.000
cfs
DO:
7,17
mg/l
Depth:
5.0
ft
Temp:
29
«C
Width:
500.00
ft
Salinity:
10
ppt
DO Sat:
7.28
mg/l
90% Sat:
6.55
mg/l
CBOD
decay (Kd):
0.534
/day @ 29^C
NH3-N
decay (Kn):
0.534
/day @ 290C
Advec velocity;
0.003
mpd
Reareation
(Ka):
0'400
/day @ 291C (O'
, Estuarine number:
_________________________________________________________________
5343
Dispersion
(E):
0.100
mie/d
Components
of the
deficit
CBOD
NH3-N
DO
DO Deficit
CBOD
NBOD
Milept
______
(mg/1)
(mg/l)
(mg/1)
(mg/1)
(mg/l)
(mg/1)
outfall
______
0.41
______
0.14
______
_________
_______
______
0.0
0.40
0.13
6.53
0.64
0.25
0.38
0.1
0'32
0.11
6.55
0.62
0.25
0.37
0.2
0.25
0-08
6'58
0'59
0.24
0.35
0.3
0.20
0.07
6'62
0.55
0.22
0.33
0.4
0.16
0,05
6.67
0,50
0'20
0,30
0.5
0.13
0.04
6.72
0.45
0'18
0.27
0.6
0'10
0,03
6'77
0'40
0'16
0.24 .
0.7
0.08
0.03
6.82
0.35
0'14
0.21
0.8
0'06
0'02
6.86
0.31
0.12
0.19
'
Discharger:
Hertford WWTP
Design:
0'4000
mgd
Water Body:
Perquimans River
Pre SOC:
0'2928
mgd
Wasteflow:
0.5400
mgd
SOC:
0.0194
mgd
BOD5:
40
mg/l
Post SOC:
0.3122
mgd
' NH3-N:
20
mg/l
CBOD/BOD5:
1.5
Ambient Data
Tidal (Y,N):
Y
-------------
CBOD:
2.00
mg/l
Tide data (Y,N):
N
NH3-N:
0.50
mg/l
Net inflow:
0.000
cfs
DO:
7.17
mg/l
Depth:
5.0
ft
Temp:
29
^C
Width:
500.00
ft
Salinity:
10
ppt
DO Sat:
7-28
mg/l
90% Sat:
6.55
mg/l
CBOD
decay (Kd):
0.534
/day @ 290C
NH3-N
decay (Kn):
0.534
/day @ 291C
Advec velocity:
0.005
mpd
Reareation
(Ka):
0,400
/day @ 290C (O'
� Estuarine number:
_________________________________________________________________
1786
Dispersion (E):
0.100
mie/d
Components
of the
deficit
CBOD
NH3-N
DO
DO Deficit
CBOD
NBOD
Milept
------
(mg/l)
------
(mg/l)
------
(mg/l)
------
(mg/l)
---------
(mg/l)
-------
(mg/l)
------
outfall
0'71
0'24
0.0
0.69
0.23
6.07
1.10
0.44
0.66
0.1
0'55
0.18
6'09
1.08
0.43
0.65
0'2
0.44
0.15
6'15
1,02
0.41
0.61
0.3
0-35
0.12
6.22
0.95
0.38
0.57
0,4
0'28
0.09
6'30
0'87
0.35
0.52
0.5
0'22
0.07
6.39
0.78
0.31
0.47
0'6
0,18
0.06
6.47
0'70
0.28
0'42
0.7
0.14
0.05
6.55
0.62
0'25
0.37
0.8
0'11
0.04
6'63
0.54
0.22
0.32
Request Form for In -stream Assessment for 67B
NAME OF FACILITY 1��
SUBBASIN
COUNTY����_�_
_ ->� DESIGN FLOW
RECEIVING STREAM � � '(
BACKGROUND DATA ;
A, why is SOC needed?
(Facility is out of compliance with which
effluent limits?)
B. History of SOC requests:
1. Monthly Average waste flow -—
prior to any SOC 0
mgd
Time period averaged n�
thru Q
2. Previously approved SOC's:
Date:__-
ate:- flow:
mgd
Date; flow: _�^
---------- mgd
total of previously approved SOC flow;
m g d
3. Flows lost from plant
(facilities that have gone flow: mgd
Off line)
4 • q�urrent SOC request ,t�
flow: U•�) I `- -mgd
5. Total plant flow post-SOC
(sum of original flow and
SOC flow minus losses) ILmgd
.. 6. �Is - this
-a-n accurate flow balance for plant? Why/why not?
.,'%
C• Please attach DMR summary for
Parame-
ters. If possible past Year for all permitted
facility include reports from previous Parame-
Y has been under SOC for more rears if
than a year,
CURRENT SOC-REQUEST :
A, Request is for domestic or industrial waste? ation, please specify percentages. If itis a combin-
Z>O % qt
B• What type of industry? Please attach
�! any pertinent data.
C• The region proposes the following SOC limits:
BOD5 .401 e" 0
mg/l
NH3
mg/1
DO
mg/1
TSS O
fecal coliform_02d)d
#/100m1
pH--�=� SU
other parameters
D. W"At.is the basis for these limits? '
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