(A) In addition to the base user charges applicable pursuant to § 50.15, users discharging pollutants to the wastewater treatment works of the municipal utilities, whose average concentration, as defined in § 50.11, in one or more classifications exceeds in any month that concentration defined as normal in § 50.11 in the corresponding classification shall be subject to surcharges calculated as follows.
(1) Surcharges for each billing period during a calendar year shall be based on the following values for the previous three-year average. Data not available shall be estimated in the most practical manner possible.
(a) Estimated total operation and maintenance expenses of the wastewater treatment plant and the wastewater collection system pursuant to § 50.15(B)(1)(a) Cto;
(b) Estimated total pounds of BOD received at the plant Bt;
(c) Estimated total pounds of suspended solids received at the plant St;
(d) Estimated total pounds of phosphorus received at the plant Pt;
(e) Estimated total pounds of grease received at the plant Gt;
(f) Estimated total pounds of ammonia nitrogen received at the plant At;
(g) Estimated total pounds of MBAS received at the plant Mt;
(h) Estimated total pounds of Total Dissolved Solids received at the plant Tt.
(2) Surcharge on user charges per pound of BOD in excess of normal equals: Cto multiplied by 0.24 divided by Bt
(3) Surcharge on user charges per pound of suspended solids in excess of normal equals: Cto multiplied by 0.17 divided by St
(4) Surcharge on user charges per pound of phosphorus in excess of normal equals: Cto multiplied by 0.05 divided by Pt
(5) Surcharge on user charges per pound of grease in excess of normal equals: Cto multiplied by 0.02 divided by Gt
(6) Surcharge on user charges per pound of ammonia nitrogen in excess of normal equals: Cto multiplied by 0.03 divided by At
(7) Surcharge on user charges per pound of MBAS in excess of normal equals: Cto multiplied by 0.02 divided by Mt
(8) Surcharge on user charges per pound of Total Dissolved Solids in excess of normal equals: Cto multiplied by 0.01 divided by Tt
(9) Pounds of BOD per billing subject to surcharge equals: (Average concentration of BOD, calculated pursuant to § 50.11 in milligrams per liter minus 200 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of BOD is 200 milligrams per liter or less, no surcharge for BOD shall apply.
(10) Pounds of suspended solids per billing period subject to surcharge equals: (Average concentration of suspended solids, calculated pursuant to § 50.11, in milligrams per liter minus 240 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of suspended solids is 240 milligrams per liter or less, no surcharge for suspended solids shall apply.
(11) Pounds of phosphorus per billing period subject to surcharge equals: (Average concentration of phosphorus, calculated pursuant to § 50.11, in milligrams per liter minus ten milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of phosphorus is ten milligrams per liter or less, no surcharge for phosphorus shall apply.
(12) Pounds of grease per billing period subject to surcharge equals: (Average concentration of grease, calculated pursuant to § 50.11 in milligrams per liter minus 35 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of suspended solids is 35 milligrams per liter or less, no surcharge for grease shall apply.
(13) Pounds of ammonia nitrogen per billing period subject to surcharge equals: (Average concentration of ammonia nitrogen, calculated pursuant to § 50.11 in milligrams per liter minus 15 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of ammonia nitrogen solids is 15 milligrams per liter or less, no surcharge for ammonia nitrogen shall apply.
(14) Pounds of MBAS per billing period subject to surcharge equals: (Average concentration of MBAS, calculated pursuant to § 50.11 in milligrams per liter minus 10 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of MBAS solids is 10 milligrams per liter or less, no surcharge for MBAS shall apply.
(15) Pounds of Total Dissolved Solids per billing period subject to surcharge equals: (Average concentration of Total Dissolved Solids, calculated pursuant to § 50.11 in milligrams per liter minus 500 milligrams per liter) times volume of wastewater discharged from the user to the wastewater treatment works per billing period, in 1,000 cubic feet times 0.06238. If the average concentration of Total Dissolved Solids is 500 milligrams per liter or less, no surcharge for Total Dissolved Solids shall apply.
(16) Surcharge on user charges equals pounds of BOD calculated pursuant to division (A)(9) above times surcharge per pound calculated pursuant to division (A)(2) above; plus pounds of suspended solids calculated pursuant to division (A)(10) above times surcharge per pound calculated pursuant to division (A)(3) above; plus pounds of phosphorus calculated pursuant to division (A)(11) above times surcharge per pound calculated pursuant to division (A)(4) above; plus pounds of grease calculated pursuant to division (A)(12) above times surcharge per pound calculated pursuant to division (A)(5) above; plus pounds of ammonia nitrogen calculated pursuant to division (A)(13) above times surcharge per pound calculated pursuant to division (A)(6) above; plus pounds of MBAS calculated pursuant to division (A)(14) above times surcharge per pound calculated pursuant to division (A)(7) above; plus pounds of Total Dissolved Solids calculated pursuant to division (A)(15) above times surcharge per pound calculatd pursuant to division (A)(8) above.
(17) Formulas as contained in division(A)(2), (A)(3), (A)(4), (A)(5), (A)(6), (A)(7), and (A)(8) above shall be subject to adjustment as necessary based on annual audit of sewer revenue fund expenses.
(B) Surcharges may also be established for pollutants other than those provided in this section which are permitted to be discharged to the wastewater treatment works by the municipal utilities, after pretreatment or without pretreatment.
(C) Surcharges levied pursuant to this section shall be billed monthly or as otherwise established by the Board of Municipal Utilities. The rates shall be as established by the Board of Municipal Utilities.
(1980 Code, § 50.16) (Ord. 3928, passed 12-17-1979; Am. Ord. 7520, passed 2-6-2006; Am. Ord. 8840, passed 4-20-2020; Am. Ord. 9078, passed 3-20-2023)