40C-44.066. Water Quality Practices

The practices listed below are set forth in this rule for the purpose of evaluating compliance with this chapter. It is presumed the water quality practices implemented in accordance with this section will provide reasonable assurance that the system will comply with the performance standards described in rule 40C-44.065, F.A.C. The water quality practices or other alternatives shall be implemented to the extent necessary to comply with the performance standards described in rule 40C-44.065, F.A.C. In some cases, the implementation of these practices may not result in compliance with the performance standards for issuance of an individual environmental resource permit for an agricultural system. In those cases, the applicant shall provide for implementation of such additional water quality practices and/or treatment methodologies as necessary to provide reasonable assurance that the discharge will comply with the performance standards described in rule 40C-44.065, F.A.C.

(1) Reduce the volume of stormwater and associated wastewater discharged to waters of the state by:

(a) Implementing management practices designed to reduce the volume of water discharged off-site, including Water Table Control in Open Channels, Irrigation Land Leveling and Irrigation Water Management, and

(b) Maximizing onsite recycling to satisfy irrigation, freeze protection and pest control needs. The applicant may demonstrate maximum stormwater harvesting by using all the practically available water from reservoir storage prior to using groundwater.

(2) Implement and maintain a Conservation Plan, which includes a Nutrient Management Plan and Pesticide Management Plan.

(3) Provide treatment of the pollutants generated by the agricultural operation. The treatment method required depends on the intensity of land use and associated pollutants.

(a) Wet detention ponds, designed and operated in accordance with paragraph (b) or (c) below, are presumed to satisfy the requirements of paragraphs (1)(b) and (3), for those portions of an agricultural operation described below:

1. Citrus, row crop, sod, hayland or improved pasture which discharge to Class I, Class II, or Outstanding Florida Waters, or

2. Citrus, row crop, sod, hayland or improved pasture on predominantly organic soils.

(b) Detention ponds which are part of an existing surface water management system, and which comply with following design and performance criteria are presumed to provide treatment.

1. Wet detention treatment volume is equal to the first inch of runoff.

2. The permanent pool volume provides an average residence time of 21 days during the wet season (June through October). This volume may be determined by estimating 13.82% of the wet season average runoff. The permanent pool volume should be recycled, pursuant to paragraph 40C-44.066(1)(b), F.A.C.

3. No more than half the treatment volume is drawn down in the first 60 hours following a storm event, and the entire treatment volume is drawn down within 168 hours.

4. Pond depths below the water control elevation shall not exceed an average of 5 feet or a maximum of 10 feet, unless the applicant affirmatively demonstrates that the deeper depths will not cause anaerobic conditions in the water column.

5. For ponds where interior borrow canals are likely to result in short-circuiting of flows between the inlet and outlet, the effective flow path shall be increased by adding diversion structures such as canal plugs or baffles.

(c) Detention ponds proposed as part of a new surface water management system which are designed, constructed and operated in accordance with the following design and performance criteria are presumed to provide treatment.

1. Wet detention treatment volume is equal to the first inch of runoff.

2. The permanent pool volume provides an average residence time of 21 days during the wet season (June through October). This volume may be determined by estimating 13.82% of the wet season average runoff. The permanent pool volume should be recycled, pursuant to paragraph 40C-44.066(1)(b), F.A.C.

3. No more than half the treatment volume is discharged in the first 60 hours following a storm event, but at least half of the treatment volume is discharged within 72 hours following a storm event.

4. Pond depths below the water control elevation shall not exceed an average of 4 feet or a maximum of 10 feet, unless the applicant affirmatively demonstrates that the deeper depths will not cause anaerobic conditions in the water column.

5. The treatment volume should not cause the pond level to rise more than 18 inches above the control elevation unless it is demonstrated that the littoral zone vegetation can survive at greater depths and that the pond area ratio (drainage area/pond area) is still sufficient to provide adequate treatment.

6. The pond design shall incorporate a littoral zone or an alternate method to promote sedimentation. Littoral zones shall be gently sloped (6:1 or flatter) to a point 2-3 feet below the bleed-down or control elevation and extend to the top of the treatment volume. The littoral zone and vegetation should be concentrated at the inflow (adjacent to the sump, if required) and at the outfall.

7. The alignment and location of inlets and outlets shall be designed to maximize flow paths in the pond. The pond shall have a length to width ratio of a minimum of 2:1. If short flow paths are unavoidable, the effective flow path should be increased by adding diversion barriers such as islands, peninsulas or baffles to the pond. Inlet structures should be designed to dissipate the energy of water entering the pond. Pumped inflows must provide a sump to promote sedimentation and reduce water velocities.

8. Pond design must include permanent access for maintenance.

9. The bleed-down orifice invert elevation shall be at or above the estimated wet season water table elevation. If the orifice is proposed to be set below the wet season water table elevation, groundwater inflow must be considered in orifice drawdown calculations, calculation of average residence time, and estimated normal water level. For ponds with pumped inflows, the applicant must demonstrate that the water table of wetlands within the drainage area will not be significantly lowered.

(d) Other water quality practices in lieu of wet detention, such as overland flow, vegetative filters and detention in isolated wetlands, are presumed to satisfy the requirements in subsection (3), for low intensity agricultural operations such as rough or semi-improved pasture, when the practice(s) is designed, operated and maintained using accepted engineering principles.

(e) Agricultural surface water management systems may incorporate overland flow, vegetative filters and detention in isolated wetlands as water quality practices. Existing canals and conveyance systems may be incorporated into a wet detention treatment system, when appropriate. The applicant must provide reasonable assurance, through plans, test results or other information, that the practice will provide an adequate level of treatment to meet the performance standards above.

(4) Applicants who propose to satisfy the performance standards in rule 40C-44.065, F.A.C., by employing a treatment methodology or device other than those described in subsections 40C-44.066(1) through 40C-44.066(3), F.A.C., may seek approval for an equivalent alternative through the District’s permit process. The applicant must provide reasonable assurance, through plans, test results or other information, that the alternative will provide an adequate level of treatment to meet the performance standards above.

Rulemaking Authority 373.044, 373.113, 373.171, 373.4131, 373.416, 373.418 FS. Law Implemented 373.016, 373.4131, 373.416 FS. History–New 8-11-91, Amended 10-20-92, 10-3-95, 10-1-13, 6-1-18.