Currently, each water management district has its own Applicant’s Handbook Volume II, applicable only within the district. Volume II is applicable only to those ERP activities that involve the design of a stormwater management system that requires a permit under Chapter 62-330, F.A.C. More specifically, it provides specific, detailed design and performance methodologies designed to meet the water quality and quantity requirements of stormwater management systems.
A stormwater management system is defined in sections 373.403(10) and 403.031(16), F.S., and in section 2.0 of Handbook Volume I, as a system that is designed and constructed or implemented to control discharges which are necessitated by rainfall events, incorporating methods to collect, convey, store, absorb, inhibit, treat, use or reuse water to prevent or reduce flooding, overdrainage, environmental degradation, and water pollution or otherwise affect the quantity and quality of discharges from the system.
Unmanaged urban stormwater creates a wide variety of effects on Florida’s surface and ground waters. Urbanization leads to the compaction of soil; the addition of impervious surfaces such as roads and parking lots; alteration of natural landscape features such as natural depressional areas that hold water, floodplains and wetlands; construction of highly efficient drainage systems; and the addition of pollutants from everyday human activities. These alterations within a watershed decrease the amount of rainwater that can seep into the soil to recharge our aquifers, maintain water levels in lakes and wetlands, and maintain spring and stream flows. Consequently, the volume, speed and pollutant loading in stormwater that runs off developed areas increases, leading to flooding, water quality problems and loss of habitat.
To manage urban stormwater and minimize these impacts to our natural systems, Florida was the first state in the country to adopt a rule requiring the treatment of stormwater to a specified level of pollutant load reduction for all new development. Florida’s original stormwater rule was adopted in 1981 and went into effect in February 1982.
The stormwater rule is a technology-based rule that relies upon four key components:
- A performance standard or goal for the minimum level of treatment.
- Design criteria for best management practices (BMPs) that will achieve the performance standard.
- A rebuttable presumption that discharges from a stormwater management system designed in accordance with the BMP design criteria will not cause harm to water resources.
- Periodic review and updating of BMP design criteria as more information becomes available to increase their effectiveness in removing pollutants.
Florida’s stormwater rules were developed to meet a performance standard of reducing the average annual post-development stormwater pollutant loading of Total Suspended Solids (TSS) by 80%, or by 95% for stormwater discharges directly into Outstanding Florida Waters. This level of treatment was selected for two reasons:
- To establish equitability in treatment requirements between point and nonpoint sources of pollution. The minimum level of treatment for domestic wastewater point sources was “secondary treatment” which equated to an 80% reduction in TSS.
- The costs of stormwater treatment greatly increased as the level of treatment rose above 80%.
In 1990, in response to legislation, the department developed and implemented the State Water Resource Implementation Rule (originally known as the State Water Policy rule). This rule sets forth the broad guidelines for the implementation of Florida’s stormwater program and describes the roles of DEP, the water management districts and local governments.
The rule provides that one of the primary goals of the program is to maintain, to the degree possible, during and after construction and development, the predevelopment stormwater characteristics of a site. The rule also provides a specific minimum performance standard for stormwater treatment systems: to remove 80% of the post-development average annual stormwater pollutant loading of pollutants “that cause or contribute to violations of water quality standards.” This performance standard is significantly different than the original one used in Florida’s stormwater treatment rules.
