(A) Calculating billable flows and loading.
(1) Measurement of wastewater volume. The charges assessed residential users and those users of other classes discharging normal domestic strength wastewater shall be established proportionately according to billable wastewater volume. Billable wastewater volume shall be calculated as follows:
(a) Residential users. Billable wastewater volume for residential users shall be calculated on the basis of metered water usage. The wastewater will be billed monthly based off of actual water usage for the months of November through April. May through October the wastewater shall be calculated by an average water usage from the prior November through April months. The city may require residential users to install water meters for the purpose of determining billable wastewater volume.
(b) Nonresidential users.
1. The billable wastewater volume of nonresidential users may be determined in the same manner as for residential users, except that if the city determines that there are significant seasonal variations in the metered water usage of nonresidential users resulting in a proportionate increase (or decrease) in wastewater volume, then billable wastewater volume shall be:
a. Calculated on the basis of quarterly metered water usage as recorded throughout the year, or
b. Calculated on the basis of wastewater flow meters.
2. The city may, at its discretion, require nonresidential users to install such additional water meters or wastewater flow meters as may be necessary to determine billable wastewater volume.
(2) Determination of loadings from metered water usage. The billable amounts of BOD and TSS will be calculated from the volume of metered water usage, as determined above, where the billable quantities will be those attributable to wastewater at a concentration of 250 mg/l BOD and 300 mg/l TSS (normal domestic strength wastewater).
(B) Determination of sewer service charges for normal domestic strength users. User charges for normal domestic strength users shall be determined as follows:
(1) Calculation of unit costs for treatment of normal domestic strength wastewater:
Un = Uf + [(Ubod)(1.560)] + [(Utss)(1.871)]
Where: Un = Unit cost of operation, maintenance, and replacement to treat normal domestic strength, in $/CCf.
Uf = Unit cost for treatment of billable flow in $/CCF.
Ubod = Unit cost for treatment of BOD in $/lb.
Utss = Unit cost for treatment of TSS in $/lb.
1.560 = Lbs. of BOD in 1 CCF of normal domestic strength wastewater.
1.871 = Lbs. of TSS in 1 CCF of normal domestic strength wastewater.
(2) Calculation of sewer service charge for normal domestic strength wastewater:
SSC = Br + DSC + (Un x Bwv)
Where: SSC = Sewer service charge
Br = Base rate
DSC = Debt service charge
Un = Unit cost for operation, maintenance, and replacement to treat normal domestic strength, in $/CCF.
Bwv = Billable wastewater volume of the particular user in CCF.
(Ord. 150, passed 7-26-90; Am. Ord. 386, passed 1-11-16)