Agricultural Parcels

Stormwater Fee Calculations
First, an Equivalent Residential Unit (ERU) is calculated. In Yakima County, the City of Yakima and City of Union Gap, this was done by statistically sampling residential properties and averaging the amount of impervious surface using aerial photography and the County Geographical Information System (GIS). Based on this analysis, 1 ERU is 3,600 square feet. Next, the property or land area of all developed parcels in the County are classified into one of the following general classes based on zoning land use categories:
  • Urban residential
  • Urban commercial/industrial (including government, military, schools, churches, etc)
  • Urban agricultural
  • Exempt
Assignment of ERU to residential parcels varies between the regional municipalities. For urban commercial, industrial, institutional, and governmental parcels, the number of urban ERUs is determined by dividing the amount of impervious surface (in feet squared) on the parcel by 3,600 square feet. ERUs for urban agricultural parcels are based on parcel size, as shown below.
Parcel Size
Urban ERUs
Up to 1 acre
0.5 ERU
Greater than 1 acre, up to and including 5 acres
1 ERU
Greater than 5 acres, up to and including 20 acres
1.5 ERU
Greater than 20 acres, up to and including 40 acres
2 ERU
Greater than 40 acres, up to and including 70 acres
3 ERU
Greater than 70 acres, up to and including 100 acres
4 ERU
Greater than 100 acres (parcel sizes in acres)
Parcel Size Divided by 25
Lastly, the total number of ERUs is divided into the annual estimated budget for the utility to determine a base rate. The base rate is then multiplied by the number of ERUs associated with a parcel to calculate a parcel fee. The process follows methods used nationally for other stormwater utilities and provides an equitable distribution of the utility cost based on relative impact to water quality and stormwater runoff.