The wastewater service charge shall be computed by the following formula:
CW = CM+(Vu-X)CU
Where CW = Amount of waste service charge ($) per bill period;
CM = Minimum charge for operation, maintenance and replacement;
Vu = Wastewater volume for the billing period;
X = Allowable consumption in gallons for the minimum charge; and
CU = Basic user rate for operation, maintenance and replacement.
(1999 Code, § 38-4-35)