Systems Planning

Commercial Stormwater Credits

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Commercial properties exclude single and two-family dwellings and are billed at the rate of $851.44 per impervious acre per quarter, plus a $4.15 customer charge per quarter. The following actions can be undertaken to receive credits on the quarterly stormwater bill.

Commercial credit options 

Community Partners for Clean Streams

Community Partners for Clean Streams (CPCS) is a program with the Washtenaw County Water Resources' Office to help identify practical, cost effective ways to protect Washtenaw County waterways through pollution prevention. CPCS is a cost-free initiative that provides information, technical advice and recognition to participants. 

This option reduces the customer charge by 25.83%.  

Chapter 63 Compliant Stormwater Control

Locations may be able to install a stormwater management system that meets the standards outlined in Chapter 63 (changed to Stormwater Management, Section 5.22 of the Unified Development Code).  This option is potentially also a credit option for one- and two-family residences. For more information, email

This option reduces the customer stormwater discharge rate by 28.87%.  

Other Approved Stormwater Controls

A variety of options are listed below and described in Best Management Practices for Stormwater: A Developer's ​Guide for Ann A​rbor (PDF).  For more information, email
  • Vegetated Swales and Filter Strips 
  • Infiltration and Percolation Basins and Trenches
  • Porous Pavement 
  • Extended (Dry) Detention Basins 
  • Retention (Wet) Ponds 
  • Constructed Wetlands 
  • Media Filtration
  • Other Stormwater Treatment System

This option reduces the stormwater discharge rate by 8.17% and the customer charge by 25.83%.  


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