Using an average of all applicable sample results, a surcharge will be determined for every permitted source of industrial waste based on the following formula:

S = V x 8.34 [A (BOD-200) + B (TSS-200)],
 
Or, if the Chemical Oxygen Demand (COD) is more than 2.25 times greater than the BOD, then the formula is:
 
S = V x 8.34 [C (COD-450) + B (TSS-200)]
 
Where:
 
S = Surcharge in dollars that will appear on the customer's monthly bills.
V = Wastewater actually billed in millions of gallons during the billing period.
8.34 = Pounds per gallon of water
A = Unit charge in dollars per pound of BOD in excess of 200 mg/L, currently $0.5043 per lb. If measured BOD is less than 200, the rate does not apply.
BOD = Biochemical Oxygen Demand in milligrams per liter (mg/l).
200 = Normal BOD and normal TSS in mg/l.
B = Unit charge in dollars per pound of TSS in excess of 200 mg/L, currently $0.1087 per lb. If measure TSS is less than 200, the rate does not apply.
TSS = Total Suspended Solids in milligrams per liter (mg/l).
C = Unit charge in dollars per pound of COD in excess of 450 mg/L, currently $0.2242 per lb. If the COD is less than 450 mg/L, the rate does not apply.
COD = Chemical Oxygen Demand in milligrams per liter (mg/l)
450 = Normal COD in milligrams per liter (mg/l.)

The surcharge billed (S) changes according to the wastewater billed (V), which may vary from one month to the next. For that reason, it is often more useful to discuss surcharges in terms of the Surcharge Factor, the quality component of the surcharge formula. This is expressed as:

(SF) = 8.34[A(BOD-200)+B(SS-200)]
 
Or, if the COD is more than 2.25 times greater than the BOD, then the formula is:
 
(SF) = 8.34[C(COD-450)+B(SS-200)]

View sample surcharge calculations or use our Surcharge Calculator.