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Section 2 User Characteristics <br /> <br />2-2 <br />Use of contents on this sheet is subject to the limitations specified at the end of this document. <br />2.4 Customer Class Wastewater Flow and BOD/SS Concentrations <br />Listed in the table below are flows and BOD/SS concentrations for each customer class that are used to <br />develop wastewater rates. Residential customer class wastewater flow is based on metered winter water <br />use. Commercial customer classes wastewater flow is based on metered potable water use. Industrial <br />User wastewater flow is based on effluent meter measurements. Flow from Inflow/Infiltration (I/I) is <br />based on a comparison of summer and winter flows to the City’s Water Pollution Control Plant (WPCP).2 <br />All flow data is for FY18. <br />Residential wastewater BOD/SS concentration estimates for the Residential customer class are based <br />on a mass loading analysis.3 Wastewater BOD/SS concentration estimates for Commercial customer <br />classes are based on data gathered by other wastewater agencies. Industrial User wastewater BOD/SS <br />concentration are based on sampling and analysis of wastewater discharge from each user. Wastewater <br />BOD/SS concentration estimates for I/I are based on data gathered by other wastewater agencies. All <br />BOD/SS concentration data is for FY18. <br /> <br />Table 2-1. Customer Class Wastewater Discharge Characteristics <br /> <br /> <br /> <br /> <br />2 Inflow is stormwater that enters into sanitary sewer systems at points of direct connection to the systems. Various sources <br />contribute to the inflow, including footing/foundation drains, roof drains or leaders, downspouts, drains from window wells, <br />outdoor basement stairwells, drains from driveways, groundwater/basement sump pumps, and even streams. Infiltration is <br />groundwater that enters sanitary sewer systems through cracks and/or leaks in the sanitary sewer pipes. Cracks or leaks in <br />sanitary sewer pipes or manholes may be caused by age related deterioration, loose joints, poor design, installation or <br />maintenance errors, damage or root infiltration. <br />3 A mass loading analysis compares the amount of BOD and SS treated at the City’s Water Pollution Control Plant with the <br />amount of BOD and SS discharged by Residential customers, Commercial customers, Industrial User customers and added by <br />Inflow/Infiltration. <br />Number of Flow Strength <br />Billing Average Data BOD SS Data <br />Units gpd/Unit Source mg/L mg/L Source <br />Residential <br />Single family 14,142 145 water meter 300 320 <br />Multiple family 4,243 121 water meter 300 320 <br />Nonres <br />Auto, Steam cleaning 63 680 water meter 1,000 1,100 <br />Bakeries 3 74 water meter 1,000 600 <br />Laundries 23 3,024 water meter 450 240 <br />Markets & foods 34 1,026 water meter 800 900 <br />Mixed Use 265 333 water meter 800 800 <br />Restaurants 97 968 water meter 1,000 600 <br />Other Commercial 1,182 611 water meter 300 320 <br />Institutional <br />Schools 31 1,180 water meter 300 320 <br />Industrial 20 26,649 effluent meter 1,574 605 lab analysis <br />Inflow/Infiltration 1 210,046 estimated 20 60 estimated <br />mass loading <br />analysis <br />data <br />generated by <br />other <br />wastewater <br />agencies <br />98