Storm Water Utilities

What is a Storm Water Utility?

  • Similar to a sewer or water utility.
  • Provides a service to the public and is financed through the regular billing of customers through user charges.

Why Consider a Storm Water Utility

  • Storm water systems require regular maintenance, repair and expansion.
  • More storm water to handle due to development (quantity).
  • Movement away from conbined sewer systems (storm and sanitary)
  • Regulations and permitting
  • Increasing demands on already stressed sources of storm water funding (taxes, assessments, general fund, street fund, etc.).
  • State and federal assistance reduced.
  • Known or predictable amount allows for planning, prioritizing and scheduling of projects.
  • Provides a reliable funding mechanism for selected storm water project costs.
  • All contributors of storm water are involved.

How Do You Get Started?

  • Identify current or existing storm water costs.
    • Operation & Maintenance
    • Billing
    • Other Administrative
    • Capital Improvement Program
    • Debt
  • Estimate future costs and needs from a Comprehensive Storm Water Master Plan.
    • Operation & Maintenance
    • Billing
    • Other Administrative
    • Capital Improvement Program
    • Debt
    • Priorities/Scheduling


  • Can be accomplished through passage of an ordinance.


  • Flat Rate
    • Each land use type is charged the same rate, regardless of the size of the parcel and the amount of imperviousness.
  • Hydrologic Response Formula
    • The size of the parcel is taken into consideration, as well as the type of land use. Could use a range of sizes.
    • The more intense types of land uses cause more runoff (different runoff coefficients).
  • Equivalent Residential Unit (ERU)
    • Provides a fair and equitable method of recovering storm water related costs.
    • An impervious surface (roof, driveway, sidewalk) will not absorb the rainwater.  This causes runoff.
    • Fees based on impervious area recognize that those properties with more runoff use the storm water system more, and pay a higher proportional rate.
    • Need to measure or estimate the impervious areas for all parcels of land.
    • Single family residential properties are assumed to be homogeneous enough (in size and impervious area) that they all can be charged the same rate, whereas commercial and industrial parcels need to be examined individually.
    • The single family residential properties can be “standardized” by selecting a random sample of parcels, measuring the impervious area, and then calculating an average. This is one Equivalent Residential Unit (ERU).
    • The impervious area of all non-residential parcels must be measured.
    • Billing is simplified if impervious area for each non-single family residential parcel is put into units equivalent to the average impervious area for single family residential properties, or the number of ERUs.
    • The matrix below shows the possible revenues for various ERU rates (slope of the line will depend on total number of ERUs in a municipality).

Utility Revenue Matrix

Other Considerations

  • Credits for on-site retention/detention.
  • Credits for educational programs.
  • Credits for approved projects.

Jones & Henry
Engineers, Ltd.