(a) The standard strengths for biochemical oxygen demand and suspended solids, as shown in Section 924.06 shall be subtracted from the average strengths, as determined in Section 924.08, to determine the extra strengths of each industrial class user for each strength surcharge billing period. The extra strengths and the volume of sewage charged for the billing period shall then be used to determine the weight in pounds of biochemical oxygen demand (BOD) and suspended solids (SS) to be charged for strength surcharge. The BOD surcharge shall be based on pounds of BOD or 0.5 times the pounds of chemical oxygen demand, whichever is greater.
(b) For use in determining the BOD and SS concentrations, an average will be used which will be established from a minimum of two tests per month taken on composite samples.
(c) The charges for handling those wastes exceeding the limits set forth above shall be based on the following formula:
Cs=(Bc x B + Sc x S) Vu x 8.345
Cs=surcharge
Bc=unit cost for BOD (see Chapter 925 for rate)
B=concentration of BOD (exceeding base of 200 mg/l)
Sc=unit cost for suspended solids (see Chapter 925 for rate)
S=concentration of suspended solids (exceeding base of 250 mg/l)
Vu=total volume of flow in million gallons 8.345=constant of proportionality
(d) The charges calculated from the rate structure for any billing period plus the cost of surcharge as calculated in subsection (c) hereof, will be the charge made to that customer for that billing period.
(Ord. 82-211. Passed 12-13-82.)