Where:
| |||||||
Ct
|
=
|
Total cost to be recovered from all outside
users.
| |||||
Qou
|
=
|
Volume of wastewater from the individual outside
user in gallons per day.
| |||||
Qtou
|
=
|
Total volume of wastewater from all outside
users in gallons per day.
| |||||
Bou
|
=
|
Five-day biochemical oxygen demand from the
individual outside user in pounds per day.
| |||||
Btou
|
=
|
Five-day biochemical oxygen demand from all
outside users in pounds per day.
| |||||
Sou
|
=
|
Total suspended solids from the individual outside
user in pounds per day.
| |||||
Stou
|
=
|
Total suspended solids from all outside users
in pounds per day.
| |||||
Pou
|
=
|
Any identified pollutant for which treatment
is required and cost is incurred from the individual outside user
in pounds per day.
| |||||
Ptou
|
=
|
Any identified pollutant for which treatment
is required and cost is incurred from all outside users in pounds
per day.
|
Collection system fee
|
=
|
Qou
_____
Qt
|
x
|
IDMou
______
IDMt
|
x
|
(collection debt service + collection O &
M)
|
Where:
| ||||
Qou
|
=
|
Volume of wastewater from outside user in gallons
per day.
| ||
Qt
|
=
|
Volume of total wastewater in gallons per day
flowing through the interceptor containing the outside user's contribution.
| ||
IDMou
|
=
|
Inch diameter - mile of City of Watertown sewer
interceptor through which the outside user's wastewater contribution
will flow.
| ||
IDMt
|
=
|
Total inch diameter - mile of the City of Watertown
sewer collection system.
|
TABLE I
Limitations on Toxic Substances Entering
the Public Sewers
| |
---|---|
Substance
|
Limitation
(parts per million)
|
Iron, as Fe
|
5.0
|
Chromium, as Cr (hexavalent)
|
2.0
|
Copper, as Cu
|
1.0
|
Zinc, as Zn
|
4.0
|
Chlorine demand
|
15.0
|
Phenol
|
1.0
|
Cyanide, as CN
|
2.0
|
Nickel
|
1.0
|
Sum of chromium (hexavalent), copper, zinc and
nickel, not greater than
|
10.0
|
SCHEDULE A
Calculation of Surcharge For High-Strength
Waste
| |||
---|---|---|---|
Range of BOD
(parts per million)
|
Range of Suspended Solids
(parts per million)
|
Range of Chlorine Demand
(parts per million)
|
Percent of Sewer Service Charge
|
0-300
|
0-350
|
0-15
|
(No surcharge)
|
300-350
|
350-400
|
15-25
|
5%
|
350-400
|
400-450
|
25-35
|
10%
|
400-450
|
450-500
|
35-45
|
15%
|
450-500
|
500-550
|
45-55
|
20%
|
500-550
|
550-600
|
55-65
|
25%
|
550-600
|
600-650
|
65-75
|
30%
|
[Each increment of 50 parts per million (BOD,
suspended solids) or 10 parts per million (chlorine demand) accompanied
by an increase of 5% in sewer service charge.]
|
Illustrative Example:
Composite sampling and analysis by the City
during a particular month revealed the following data on liquid wastes
from User A, whose sewer service charge for that month is $1,000.
|
Week Number
|
BOD
(parts per million)
|
Suspended Solids
(parts per million)
|
Chlorine Demand
(parts per million)
|
---|---|---|---|
1
|
290
|
310
|
43
|
2
|
340
|
360
|
45
|
3
|
410
|
370
|
53
|
4
|
470
|
409
|
49
|
Calculation of Surcharge:
| ||
Average monthly BOD
|
= 378 parts per million
| |
Average monthly suspended solids
|
= 362 parts per million
| |
Average monthly chlorine demand
|
= 48 parts per million
| |
BOD surcharge
|
= 10% x $1,000
|
= $100
|
Suspended solids surcharge
|
= 5% x $1,000
|
= $ 50
|
Chlorine demand surcharge
|
= 20% x $1,000
|
= $200
|
TOTAL SURCHARGE
|