NC0047384_Staff Comments_20170615

Grzyb, Julie
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Templeton, Mike
Thursday, June 15, 2017 12:59 PM
Hennessy, John
Grzyb, Julie; Rodriguez, Teresa
greensboro soc calcs
47384 alt SOC calcs.xlsx
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I didn't find the modeling files for TZO nor any of the historic WLAs (which seem to be missing entirely from the permit files).
So we would have to reconstruct a model to evaluate the discharge in any detail. That's not likely to happen anytime soon.
However, the limits we set for 56 MGD represent the same ultimate BOD load as the limits for 40 MGD. So we can calculate
the equivalent limits using the City's actual WW flows for an SOC. The attached spreadsheet does that. I modified Martie's
spreadsheet to include the revised calculations. Parts of her sheet (rows for NB and for her totals) that aren't used in the new
calcs are hidden, just to clean up the page, and the new calcs are shown as green text.
The resulting limits for BOD and ammonia are lower than what Martie proposed. The BOD limits are about 3/4 of hers, and the
ammonia limits are about 1/3 of hers. Limits for TSS and fecals would not change.
Basis of the Calculations
In modeling water quality impacts of oxygen -demanding wastes, the allowable loads are evaluated in terms of ultimate BOD
(BODu) and are then converted back to the equivalent BODs and NH3-N concentrations (or masses) before applying as limits.
The following conversion factors are involved, and you can see can see them in the formulas for individual cells in the
spreadsheet:
Units of NBOD exerted per unit of NH3-N = 4.5 (displayed as c.NBOD.NH3N in the formulas) (NBOD is ultimate
nitrogenous BOD)
Ratio of BODu to BODs = 2.0 (c.BODu.BODS)
Ratio of BODs to CBODs = 30/25 = 1.2 (c.BOD5.CBOD5)
So, putting it all together, BODu = [ CBODs * (BODs/CBODs) * (BODu/BODs) ] + [ NH3-N * NBOD/ NH3-N
Flows
I looked at the plants' flow records from 2012 on to see if the last five months are suitable for these calculations. In that time
period, January through April have had the highest combined flows, so using Jan -Apr 2017 (or Jan -May 2017, as Martie
proposes) to calculate interim limits seems reasonable.
Let me know if you have any questions.
— Mike T
Michael E. Templeton, P.E.
Wastewater Permitting Section
Division of Water Resources
Department of Environmental Quality
Office: 9ch Floor, Archdale Building
512 North Salisbury Street, Raleigh, NC 27604
Mailing Address: 1617 Mail Service Center, Raleigh, NC 27699-1617
Office: 919-807-6402
mike.templeton(alncdenr.gov
Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.
1

City of Greensboro POTWs - WA Bubble Permit Limit Calculations using Actual Flows
Bubble limit
(mg/I)_ _
13.0
POTW
Parameter
Permitted Flow WA Permit Limit
(MGD) Summer (mg/I)
Permitted
Pounds
Equivalent BODu Actual Combined
(lb/d) Flow (MGD)
TZO
CBOD
40 6.0
2,002
4,804 ENTER BELOW
T20'
CBOD
56.0
6.0
2,802
6,725
33.35
10.1
POTW
Parameter
Permitted Flow
(MGD)
WA Permit Limit
Winter (mg/I)
Permitted
Pounds
Equivalent BODu
(Ib/d)
TZ0
CBOD
40
12.0.
4,003
9,608
25.9
TZO'
CBOD
56.0
12.0
5,604
13,451
20.1
POTW
Parameter
Permitted Flow
(MGD)
WA Permit Limit
Summer (mg/I)
Permitted
Pounds
Equivalent BODu
(lb/d)
TZO
NH3-N
40
6.0
2,002
9,007
13.0
TZO'
NH3-N
56.0
2.46
1,149
5,170
4.1
Permitted Flow
(MGD)
POTW
Parameter
WA Permit Limit
Winter (mg/I)
Permitted Equivalent BODu
Pounds (Ib/d)
TZ0
NH3-N
40 12.0
4,003 18,014
25.9
TZO'
NH3-N
56.0 4.92
2,298
10,340
8.3
Summer Loads
TZO BODu 40 13,811
TZO' BODu 56 11,896
Winter Loads
TZO BODu 40 27,622
TZO' BODu 56 23,791
POTW
Parameter
Permitted Flow
(MGD)
WA Permit Limit Year-
Round (mg/I)
Permitted
Pounds
TZ0
TSS
_
40 45
15,012
75.6
TZO'
TSS
56.0
415.0
WA Permit Limit
Year -Round (col/100)
45.0
POTW
Parameter
Permitted Flow
(MGD)
Permitted
Pounds
TZO
Fecal
40 400
N/A
TZO'
Fecal
Actual Flow
(MGD)
56.0
400.0
400.0
Combined Flow
(MGD)
POTW
NB
6.907
TZO
27.598
Jan 2017
34.505
NB
6.916
TZO
23.987
Feb 2017
30.903
NB
6.770
TZO
24.875
Mar 2017
31.645
NB
6.907
TZO
29.22
Apr 2017
36.127
NB
7.17
TZO
26.39
May 2017
33.56
AVG
33.348
1/1
47384 alt SOC calcs.xlsx, WA Limits
8/1/2017, 3:44 PM

City of Greensboro POTWs - MA Bubble Permit Limit Calculations using Actual Flows
POTW
Parameter
Permitted Flow
(MGD)
MA Permit Limit
Summer (mg/I)
Permitted
Pounds
Equivalent BODu
(Ib/d)
Actual Combined
Flow (MGD)
Bubble limit
(mg/I)
TZO
CBOD
40
4.0
1,334
3,203
ENTER BELOW
8.6
TZO'
CBOD
56.0
4.0
1,868
4,484
33.35
6.7
POTW
Parameter
Permitted Flow
(MGD)
MA Permit Limit Winter
(mg/l)
Permitted
Pounds
Equivalent BODu
(lb/d)
TZO
CBOD
40
8.0
2,669
6,405
17.3
TZO'
CBOD
56.0
8.0
3,736
8,967
__
13.4
POTW
Parameter
Permitted Flow MA Permit Limit
(MGD) Summer (mg/I)
Permitted Equivalent BODu
Pounds (lb/d)
TZO
NH3-N
40
2.0
667
3,002
4.3 _
1.4
TZO'
NH3-N
56.0
0.82
383
1,723
POTW
Parameter
Permitted Flow
(MGD)
MA Permit Limit Winter
(mg/I)
Permitted
Pounds
Equivalent BODu
(Ib/d)
TZ0
NH3-N
40
4.0
1,334
6,005
_
8.6
TZO'
NH3-N
56.0
1.64
766
3,447
_
2.8
Summer Loads - Comparison
TZO BODu 40 6,205
TZO' BODu 56 6,207
Winter Loads - Comparison
TZ0 BODu 40 12,410
TZO' BODu 56 12,414
POTW
Parameter
Permitted Flow
(MGD)
MA Permit Limit Year-
Round (mg/I)
Permitted
Pounds
TZO
TSS
40
30
10,008
50.4
TZO'
TSS
56.0
30.0
30.0
POTW
Parameter
Permitted Flow
(MGD)
MA Permit Limit
Year -Round (col/100)
Permitted
Pounds
TZ0
Fecal
40
200
N/A
TZO'
Fecal
56.0
200.0
200.0
T
Actual Flow
(MGD)
Combined Flow
(MGD)
POTW
NB
6.907
TZ0
27.598
-
Jan 2017
34.505
NB
6.916
TZ0
23.987
Feb 2017
30.903
NB
6.770
TZ0
24.875
Mar 2017
31.645
NB
6.907
TZ0
29.22
Apr 2017
36.127
NB
7.17
TZO
May 2017
26.39
33.56
1/1
47384 alt SOC calcs.xlsx, MA Limits
8/1/2017, 3:44 PM