Based on existing and proposed land cover, sites may need to meet redevelopment standards, new development standards, or a mixture of the two.

A stormwater permit is required for the following activities:

• The cumulative addition of 20,000 square feet of impervious surface.

• Development that requires a subdivision plat or a certified survey map.

• Land disturbance exceeding four thousand square feet on a commercial, industrial, institutional or multifamily site.

• Development deemed an environmental risk by the department.

New development performance standards apply to the following:

• Sites that have added 20,000 square feet, or more, of impervious surface since August 21, 2001.

Redevelopment performance standards apply to the following:

• Sites that have added less than 20,000 square feet of impervious surface since August 21, 2001.

• Redeveloping of existing impervious surface.

If the site is a mixture of new development and redevelopment, the redevelopment performance standards apply only to “redeveloped impervious” surfaces. New development performance standards apply to all other pervious and impervious surfaces. Removing existing impervious to maximize “redeveloped impervious” surfaces is acceptable when the surfaces generate similar pollutant loads.