Stormwater Utility Fee Estimator

The Stormwater Utility Fee Estimator is a tool to help property owners view the estimated number of billing units on their property, so they will have a better understanding of their future stormwater utility fee.  Currently, the stormwater program is funded through the Sanitary District Tax based on a property’s real estate assessment. A stormwater utility, however, is calculated based on the amount of impervious surface on a parcel (hard surfaces like roofs and driveways that don’t let rain runoff soak into the ground).  The Stormwater Utility is proposed to replace the current sanitary district tax.  

The stormwater utility billing unit, or Equivalent Residential Unit (ERU), is 2400 square feet of impervious area (IA).  This is the median impervious area on Arlington County residential parcels. Learn more about a stormwater utility with this Infographic or Fact Sheet.

Arlington’s stormwater utility is still in development. The information reflected here is not final and is for illustrative and informational purposes only. Arlington County makes no guaranties or warranties regarding the accuracy and use of this information. Impervious surface area measurements are  being fine-tuned and revised so they reflect the most accurate representation of impervious area for each property. 

An example of a rate structure the County is considering for the Stormwater Utility is as follows:

Customer Class Impervious Area (IA) in Square Feet (SF)    

   Billing Unit (ERU) = 2400 square feet of impervious area


Single Family Attached

 N/A  0.6 ERU Townhouse or duplex
 Single Family Residential Detached  ≤1600 SF  0.6 ERU  
 >1600 - ≤3600 SF  1.0 ERU  
 >3600 - ≤4800 SF  1.7 ERU  
 >4800SF  Per ERU  
 Multi-Family    0.18 per Dwelling Unit      

The proposed fee structure is 0.18 ERU per housing unit. For example, if an apartment building has 150 units, it would be charged 150 x 0.18, or 27 ERUs. Using an estimated Stormwater fee of $230 per ERU, would mean this apartment building would be charged 27 ERU x $230, or $6,210 annually.  This information is shown at the parent parcel level for apartments. A condo owner with one unit in a building, would be charged 0.18 ERU. This information is shown at the unit parcel level.

 Non-Residential    Per ERU

Billed per ERU of measured impervious area. ERUs are calculated by dividing the total impervious surface area for each eligible parcel by 2,400. The result is rounded up to the nearest whole number. For example, a parcel with 6,000 square feet of impervious surface area would be responsible for three (3) ERUs: 6,000 ÷ 2,400 = 2.5, which is rounded up to 3.


Because Arlington’s stormwater utility is still in development, the rate per ERU has not been finalized yet. Additionally, since the utility fee is based on a cost recovery model, it is also dependent upon the adopted budget.  The County Board will consider the fee level for adoption during the FY 2024 budget process in Spring 2023. For illustrative purposes, an example rate is $230-250 per ERU.

  • Single family residential customers will be able to see which billing tier they will likely fall into based upon the preliminary impervious area (IA) analysis (see table above).
  • Multi-family properties (including condos and apartments) will be able to see the total number of ERUs that have been preliminarily assigned to their main property location, based on the sample fee structure.
  • Non-Residential properties will be able to see the total number of ERUs on their property.


View the Fee Estimator Map

Submit comments or questions on the Fee Estimator or the ERU estimate for your property 

Pursuant to Section 54.1-402 of the Code of Virginia, any determination of topography or contours, or any depiction of physical improvements, property lines or boundaries on the Webmap is for general information only and shall not be used for the design, modification, or construction of improvements to real property or for flood plain determination.

For more information, visit our Stormwater Utility project website. 

Stormwater Utility Fee Estimator FAQs

What is a Equivalent Residential Unit (ERU)?   An ERU is the billing unit for a stormwater utility. One ERU is the median impervious coverage for single-family detached properties in Arlington, which is estimated to be 2,400 square feet.  A fee for one ERU will be established for the stormwater utility and properties would be charged based on how many ERUs are on the property.  One ERU is currently estimated to cost around $230-250/year, but this number will change as the utility and future budgets are finalized.

What is the Bill Estimator?  The Bill Estimator is a tool that lets property owners see the estimated impervious cover and number of ERUs on their property. 

How do I use the WebMap?

  • Search by Address:   
    1. Enter an address. 
    2. There may be two or more results:
    • Arlington Geocoder:  Address Location
    • Property Fee Data:  Estimated Annual Fee
    Click on a Parcel:
    A pop up will appear displaying the estimated stormwater utility fee information.  If there is more than one record for the parcel, use the address drop down in the pop up to select the desired address.  Or click on the Next to scroll through the associated records.  
    Turn Layers On and Off:   
    Select the Layers tab to view the available layers.  The layers can be turned on or off.
    To zoom to the full extent of the map, click on  

    Zoom to Full Extent:  

    To interactively pan around the map, click on:   
    What if some of the areas shown as impervious on my property are actually a permeable surface?   There will be a credit program where property owners can receive reductions for actions taken to reduce runoff on their property. 

What if I think the impervious calculation for my property is not correct?  There will be an appeal process if you think the impervious cover calculation for your property is not correct.

If a single-family residential detached property has less than 2400 sq ft, will it still be charged 1 ERU?    The County has proposed a rate structure with several tiers for single family detached properties, with the initial tier of 0.6 ERU for properties with lower levels of impervious area.  See the table above for the proposed rate structure.

What’s the cost impact to homeowners?  For an average homeowner, the current sanitary district tax is around $130 per year.  Under a stormwater utility, 90% of single-family homeowners will be charged 1 ERU or less.  1 ERU is currently estimated at $230-250 per year (please note these numbers may change as the rate structure and future budgets are finalized).

Why are some properties shown with 0 or TBD ERUs on the map?  The development of the stormwater utility is still underway. If a property is made up of multiple parcels, the ERU information is associated with the main parcel and the related parcels are shown with 0 ERUs.  If we do not have information for a parcel yet, it is shown as TBD.

View more Stormwater Utility FAQs