In addition to the base user charges applicable pursuant to § 51.095, users discharging pollutants to the wastewater treatment works, whose average concentration, as defined in § 51.085, in one or more classifications exceeds in any month that concentration defined as normal in § 51.085 in the corresponding classification shall be subject to surcharges calculated as follows:
(A) Surcharges for each billing period during a calendar year shall be based upon the following values for the calendar year: the estimated total operation and maintenance expenses (Cto); the estimated total pounds of BOD received at the plant (Bt); and the estimated total pounds of suspended solids received at the plant (St). Data not available shall be estimated in the most practical manner possible.
(B) Surcharge on user charges per pound of BOD in excess of normal equals:
Cto x .40
Bt
Bt
Until revised pursuant to the provisions of § 51.099, the surcharge for BOD in excess of normal concentration shall be $.37 per pound.
(C) Surcharge on user charges per pound of suspended solids in excess of normal equal:
Cto x 0.30
St
St
Until revised pursuant to the provisions of § 51.099, the surcharge for suspended solids in excess of normal concentration shall be $.27 per pound.
(D) Pounds of BOD per billing period subject to surcharge equals: average concentration of BOD, calculated pursuant to § 51.085 in milligrams per liter minus 216 milligrams per liter times the volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 gallons times .0083. If the average concentration of BOD is 216 milligrams per liter, or less, no surcharge for BOD shall apply.
(E) Pounds of suspended solids per billing period subject to surcharge equals: average concentration of suspended solids calculated pursuant to § 51.085, in milligrams per liter minus 260 milligrams per liter times the volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 gallons times .0083. If the average concentration of suspended solids is 260 milligrams per liter, or less, no surcharge for suspended solids shall apply.
(F) Surcharge on user charges equals the pounds of BOD calculated pursuant to division (D) of this section times surcharges per pound calculated pursuant to division (B) of this section plus pounds of suspended solids calculated pursuant to division (E) of this section times surcharge per pound calculated pursuant to division (C) of this section.
(G) Formulas as contained in divisions (B) and (C) of this section shall be subject to adjustment as necessary based upon annual audit of sewer revenue fund expenses.
(1981 Code, § 51.096) (Ord. 6405-90, passed 9-10-1990)