SharePoint

Permits

Residential Storm Water Code Requirements

Skip Navigation LinksHome » Departments » Building, Rental and Inspection Services » Construction and Building » Permits » Residential Storm Water Code Requirements
 

Impervious Area Worksheet for Residential New Construction (PDF)

Residential Storm Water Code Requirements

On Nov. 4, 2010, City Council approved an ordinance (Ordinance No. ORD-10-36) to amend the proposed storm water code (Chapter 63) changes to require storm water management on single and two-family residential properties when properties increase impervious area by 200 or more square feet. 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 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 storm water management must be provided. If the new impervious area is less than 200 square feet then no further information is necessary for storm water management. 

I am planning a home-improvement project in the spring. How will I know if my project is impacted by these code changes? 

The Systems Planning Unit created an Impervio​us 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 storm water 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 storm water treatment options to comply with the code requirements?

The 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 Resident​​​ial Storm Water 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.

For specific permit or project questions contact:

Peter Stephens

Land Development Coordinator

PStephens@a2gov.org

734.794.6000 ext. 42592

 

For questions about the residential storm water code requirement program, call:

Jerry Hancock

Storm Water and Floodplain Programs Coordinator

JHancock@a2gov.org

734.794.6430 ext. 43709​

Why were changes to the storm water 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 storm water 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 Chapter 63, the Storm Water and Soil Erosion and Sedimentation Control Ordinance, in order to improve water quality and help to reduce minor drainage issues.  

When were changes approved? 

On September 24, 2009, the Environmental Commission passed a resolution recommending Council approve the amendments to the storm water code ordinance (Chapter 63). A public meeting was held in November 2009 to present the proposed amendments to the public and receive feedback. On Nov. 4, 2010, City Council approved the proposed amendments to the storm water code (Chapter 63).  The new provisions took effect on March 1, 2011. 

What are the amendments to Chapter 63? 

The amendments to Chapter 63 require control of storm water 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 event 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?