Assume a retail outlet uses a total of 95,193 gallons of water per year, is given a landscape irrigation allowance of 10% and a general strength assignment of moderate. What is the annual Sewer Service Charge?
Step 1
First, convert the total water consumption to the amount of wastewater discharge using the landscape irrigation factor. Given the 10% allowance, 90% of the total water consumed is wastewater.
95,193 gal./year x 0.90 = 85,674 gal./year
Step 2
The total flow must be converted into units of 1,000 gallons. Divide the total flow by 1,000.
Volume = 85,674 gal./year ÷ 1,000= 85.674 K gal./year
Step3
Multiply the results of step 2 by the current rate for moderate strength wastewater of $2.23 per 1,000 gallons*.
85.674 K gal./year x $2.23 per 1,000 gal. = $191.05
Assume an industrial business discharges 100,000 gallons of wastewater per year and is given a specific assignment of 1250 mg/L COD and 300 mg/L SS. What are the annual Sewer Service Charges?
Step 1
First, a calculation must be done to convert strength assignments in milligrams per liter (mg/L) to pounds per gallons (lbs/gal.). The conversion factor is .000008344.
COD = 1250 mg/l x 0.000008344 = 0.01043 lbs/gal.
SS = 300 mg/l x 0.000008344 = 0.002503 lbs/gal.
Step 2
Use the loadings calculated in Step 1 in lb/gal. times the total flow to get total pounds per year.
COD = 0.01043 lbs/gal. x 100,000 gal./year = 1043 lbs./year
SS = 0.002503 lbs/gal. x 100,000 gal./year = 250.3lbs/year
Step 3
Convert volume, COD and SS to units compatible with the rates which are in increments of 1,000. Divide all three figures by 1,000.
Volume = 100,000 gal./yr. ÷ 1,000 = 100 K gal./year
COD = 1043 lbs/year ÷ 1,000 = 1.043 K lbs/year
SS = 250.3 lbs/year ÷ 1,000 = 0.2503 K lbs/year
Step 4
Multiply the results of Step 3 by the current rates to arrive at the total yearly Sewer Service Charge.
Volume =100 x $1.23* = $123.00
COD = 1.043 x $125.80* = $131.21
SS = 0.2503 x $230.66* = $57.73
TOTAL = $311.94
* Rates for 2003-2004
Questions on how your charges have been determined can be answered by calling Customer Service Representatives at (510) 477-7500.
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