Why Stormwater Management?
Stormwater management is necessary to prevent the loss of life and property due to flooding, to reduce expenses related to flood control and maintenance of storm drain systems, and to minimize the adverse impact of development and related construction activities. The rights of other landowners must be respected with regards to the volume and rate of discharge from a project site. This includes upstream and downstream impacts in collection, storage and conveyance systems, and impacts to other hydraulically connected areas. Special consideration must also be given to sediment generated during construction and impacts to “volume sensitive” areas which may have limited or no drainage outlet.
A stormwater permit is required from the St. Johns River Water Management District for almost any work that affects natural or man-made drainage systems or changes the use of a property or the structures on it. The following is a summary of the requirements from the St. Johns County Land Development Code. This is presented as informational only, and persons planning a project should refer to the Code for details or contact one of the county technical review engineers. There are levels of stormwater design requirements depending on the type, size and impact of a project. There are exempt projects, minor projects and those requiring full design and code compliance.
Exempt projects are those associated with agricultural activities, maintenance of drainage canals and existing stormwater systems, pavement or buildings. Isolated single and two family dwelling units are also exempt. However, they must meet finished floor elevations and lot grading requirements.
Minor Project Requirements
Minor projects are not required to limit post-development peak rate of discharge to the pre-development rate for the standardized 5 year and 25 storm event, but must meet all other requirements. They must however, provide retention of the first one inch of rainfall resulting from the developed area, or where conditions require, detention of the same volume which must be released between 24 and 72 hours after the event.