FAQ Stormwater/Drainage Plans for Residential Properties
What is a stormwater or drainage plan?
A stormwater or drainage plan is a site plan that shows where water will flow. This can be shown with
arrows and/or with ground elevations. An engineered stormwater or drainage plan includes calculations
indicating how much water will be retained on site as well elevations of high points and low points and
water retention areas on the property. An engineered drainage plan must be signed and sealed by an
engineer or professional, qualified in the state of Florida.
What do I need to submit to the Town?
If your project is proposing 500 square feet, or more, of impervious surface on a parcel, your
plan will need to submit an engineered drainage plan. This plan must include calculations
showing that 1 inch (if a landlocked property) or 1.6 inches (if adjacent to water) of stormwater
will be maintained on site. In addition to showing stormwater storage, in the correct amount (1
or 1.6 inches), the plan must also illustrate that no water will leave the site due to directional
flow. The plan should also indicate the total impervious surface percentage for the parcel. The
Town does not allow more than 67% of impervious surface on a residential property.
If your project is proposing less than 500 square feet of impervious surface, your plan will need to
show, where water will be directed from the proposed impervious surface. For example, a
driveway paving permit must show that water will not be directed to the right-of-way or to an
adjacent property. The plan should indicate that the slope of the driveway will retain water on
the property which is being improved or that a drainage system is being installed to direct water
towards an appropriate storage location on site. The plan should also indicate whether there is
any increase in impervious surface. If there is any increase in impervious surface, an impervious
surface percentage must be provided.
