Billable Equivalent Residential Unit (ERU) fees are $90 per ERU. All nonresidential properties, which includes, but not limited to Multi-Family, Commercial, Government, Non-Profit, Industrial etc. are billed a flat rate of $90 per ERU of impervious area on their property. One ERU is equal to 3952 sq. ft. So, for example if a Nonresidential site has 1- 3952 sq. ft., they will be billed one (1) ERU. If a non-residential site has 3,953 or greater sq. ft., of impervious area, they will be billed the appropriate ERU’s associated with the impervious area on the property. These fees are billed on the annual County Property Tax Assessment.