An ERU is a unit of measure which serves as an index to compare the runoff generated by different size properties with different amounts of impervious surface. Impervious surface is any surface which does not allow water to pass through to the soil. Rooftops, driveways, parking lots and streets are familiar examples of impervious surface.
The equivalent residential unit in the city for the purpose of service charge ratemaking has been determined through engineering analysis to be a gross area of 11,000 square feet and a coefficient of runoff of 0.30.
Because the hydrologic response of all detached single-family residential properties is substantially similar to this equivalent unit definitions, they shall be billed for one equivalent residential unit.