Storm Water Fee

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City of Carmel Storm Water Fees

The storm water fee helps fund the City’s drainage projects, storm sewer maintenance, storm water program, and new storm sewer construction. The storm water fee was adopted to provide a perpetual, dedicated source of funding. The chart below shows the storm water rates effective as of January 2021. As of 2017, on January 1st of each year, rates automatically increase by 3% from the previous year’s fee.

Storm Water Fee Table

 Property Type  Equivalent Residential Unit (ERU)
 Monthly Fee

Single Family Residence
(residential or agricultural)

 1  $5.91

Condominium, Townehome,
Multifamily (per dwelling unit)

 1  $5.91
Non-Residential (apartments, commercial,
industrial, tax-exempt properties and agricultural)

Impervious Area /
 $5.91 x ERU
(but no less than $5.74, unless unimproved)*
Unimproved Properties
(< 400 sq. ft. of impervious, applies to all property types)
 0.33  $1.96

*Non-residential properties that have > 400 sq. ft. and < 4,150 sq. ft.
will be charged a minimum of $5.91 or equivalent to one ERU.

Non-Residential Example:

 Property containing 8,300 square feet would be divided by 4,150 (2 ERUs) and then multiplied by $5.91 to get the total monthly amount of $11.82.

Apartment Fee Billings

Apartment complexes are considered non-residential, so the fee for the overall complex will vary based on the non-residential fee calculation. The fee will be added to the main complex utility billing account. Apartment residents should contact their apartment office to determine how this fee will be applied.

Storm Water Rate Study

A Storm Water Rate Study was completed for the City of Carmel in 2013. The study determined that establishing an equivalent residential unit (ERU) rate system was the most fair and equitable method of assessing storm water fees to all property owners.

In an ERU rate system, the impervious surface areas (roofs, driveways, sheds, etc.) of single family residential parcels are sampled throughout the city and an average impervious area is determined. The study found that the average impervious area of a single family residential (SFR) property in Carmel is 4,150 square feet. The impervious area for each non-residential property was then calculated and divided by the ERU square footage to determine how many multiples of the ERU exist on the non-SFR property. The total amount of ERUs in the city was then equated with a monetary value which would meet the projected yearly budgetary needs of the Department.

Non-SFR properties/units will be charged a multiple of $5.91 per month based on the square footage of impervious area on the property divided by 4,150 square feet. For example, a property containing 8,300 square feet, would be charged $11.82 per month ((8,300 / 4,150) x $5.91 = $11.82). Non-SFR properties containing less than 4,150 square feet will be charged a minimum of 1 ERU or $5.91 per month.

All unimproved residential properties that contain no impervious areas will be charged 0.33 ERUs or $1.96 (0.33 x $5.88) per month.

To view the complete Storm Water Rate Study, please click here.

If you have questions or concerns,
please contact the Department of Storm Water Management at
(317) 571-2441 or email