Residential stormwater code requirements
Examples of impervious surfaces include, but are not limited to, rooftops, walkways, patios, courtyards, driveways, parking lots, storage areas, concrete or asphalt paving, gravel roads, or any cleared, graded, graveled or compacted surfaces, or other surfaces which similarly impede the natural infiltration of surface water into the soil.
All grading permit applicants for projects creating new impervious areas must complete an impervious area worksheet (PDF) and submit it to the Planning and Development Services Unit along with their grading permit application. If the new impervious area is greater than 200 square feet then stormwater management must be provided. If the new impervious area is less than 200 square feet then no further information is necessary for stormwater management.
How will I know if my home improvement project is impacted by these code changes?
The Systems Planning Unit created an
Impervious Area Worksheet (PDF), that enables a homeowner or contractor to determine if the new impervious area to be added is greater than 200 square feet in which case stormwater management must be provided. If the new impervious area is less than 200 square feet then no further information is necessary to obtain a grading permit. This worksheet must be submitted along with the grading permit application and is reviewed by Planning and Development staff.
What are my stormwater treatment options to comply with the code requirements?
Impervious Area Worksheet (PDF) provides the conversion formulas to determine storage volumes for treatment measures such as rain barrels, rain gardens/bioretention areas, drywells, cisterns, swales, storage basins, and porous pavement. Also, the
Residential Stormwater Credits page has specific information about some of these treatment measures.
Who do I contact if I have questions?
For general permit questions, contact the City's Permit Desk at 734.794.6267.
Specific permit or project questions:
Land Development Coordinator
Residential stormwater code requirement program:
Stormwater and Floodplain Programs Coordinator
Why were changes to the stormwater code necessary?
In August 2007, City Council charged the Mallet Creek Coordinating Committee with prioritizing and implementing the April 2007 Watershed Recommendations of the Mallets Creek Association (Resolution R-393-8-07). On June 2, 2008, the Mallets Creek Coordinating Committee communicated its priorities to City Council in the form of a revised Mallets Creek restoration activity schedule with the top priority being regulation for stormwater management for new impervious surfaces added to single-family and two-family properties. Impervious surface means that part of a developed parcel has been modified to reduce the land’s natural ability to absorb and hold rain fall. This includes hard surfaces which cause water to run off the surface in greater quantities or at an increased rate of flow from the flow that existed under natural conditions prior to development.
The Mallets Creek Coordinating Committee has worked with city staff and the Environmental Commission Water Committee to draft amendments to the Storm Water and Soil Erosion and Sedimentation Control Ordinance, in order to improve water quality and help to reduce minor drainage issues.
What are the amendments?
The amendments to Chapter 63
(changed to Stormwater Management, Section 5.22 of the Unified Development Code)require control of stormwater runoff from the “first flush” storm event on single and two-family residential property when adding 200-square feet or more of impervious area to the property. The “first flush” is the runoff from the first inch of rain during any storm and carries approximately 90 percent of pollutants. The new requirement would only apply to the increase in impervious area.
What are other storm water resources?