Stormwater Rates
The stormwater rate system bills properties based on usage of the storm water system, as represented by impervious area. Impervious surfaces do not absorb water. Examples of impervious areas include roofs, pavement, sidewalks, patios, and gravel or crushed stone surfaces.
A computer analysis of infrared aerial photographs is able to distinguish hard, impervious surfaces in contrast to areas that can absorb stormwater, such as lawns and gardens. The computer program assigns the residential property into one of four billing tiers to more equitably distribute costs proportional to use instead of using a flat fee. Homes with larger impervious areas pay more. You can review your property's stormwater assessment online and, if desired, submit an appeal (see below).
Single and two-family residential properties are placed in one of the following four rate tiers, depending on the square footage of impervious area.
| | Single-Family and Two-Family Residential | ||
| Tier # | Measured impervious area | Representative
Impervious Area Midpoint of Tier listed on the Water Utilities Bill |
Quarterly
Charge* |
| Tier 1 | Up to 2,187 square feet | 0.03706 acres | $28.43 |
| Tier 2 | > 2,187 to 4,175 square feet | 0.06486 acres | $49.75 |
| Tier 3 | > 4,175 to 7,110 square feet | 0.11117 acres | $85.27 |
| Tier 4 | > 7,110 square feet | 0.19456 acres | $149.24 |
* Plus a $4.07 customer service charge per quarter.
Commercial and other properties (e.g., multi-family, office, institutional, and industrial land uses) are billed directly on the impervious areas at a rate of $767.06 per acre per quarter, plus a $4.07 customer charge per quarter.
The property image will show the impervious area analysis for the property you have requested. This analysis has primarily been done with a computer, so some errors may have occurred. The following pervious materials might be interpreted by the computer as impervious:
Please note that driveways are impervious regardless of the material, unless it is constructed with permeable pavers, permeable asphalt, or permeable concrete (these permeable system installations are rare).
If you have reason to believe that the impervious area has been incorrectly identified, please take the following steps:
We will review your revisions, and return the results of the analysis to you. Please remember that if you are a one or two-family residential property, you will need to reduce your impervious area by an amount sufficient to enter a lower tier. For example, if you are currently at 4,775 square feet, you will need to lower your impervious area by 600 square feet (to 4,175) in order to enter a lower tier.
You can take advantage of credits to lower your storm water bill.
Under the Post Construction Stormwater Management control measure, the City of Ann Arbor has a program requiring new and redevelopment projects to implement on-site controls that will reduce pollutant loads in stormwater run-off. The City of Ann Arbor follows the rules of the Washtenaw County Water Resources Commissioner for post construction controls. These rules are incorporated by reference into Chapter 63 of the City Code - Stormwater Management and Erosion and Sedimentation Control.
City staff review site plans for compliance with regulations governing stormwater management.
Chapter 63 (5:658) requires all site plans to include a plan for the long-term maintenance of stormwater controls:
"A program proposal for the continued maintenance of all permanent soil erosion and sedimentation control measures that remain after project completion, including the designation of the person or party responsible for the maintenance. Maintenance responsibilities shall become a part of any sales or exchange agreement for the land on which the permanent soil erosion and sedimentation control measures are located."
Low impact development (LID) is the industry standard for green infrastructure. The LID Manual for Michigan provides the latest tools for implementing post construction stormwater controls.
What is LID? In short, it is a type of development that uses a basic principle modeled after nature - to manage rainfall using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source. LID provides a host of stormwater benefits, including groundwater recharge and cleaner streams.
Keep the following in mind if you are implementing a LID project:
Implementing LID practices can:
Best Management Practices for Stormwater A Developer's Guide for Ann Arbor (PDF)