62-610.523. Design and Operation Requirements

(1) Hydraulic loading rates shall be developed on the basis of representative percolation tests (drainfield percolation tests described in Chapter 64E-6, F.A.C., are inappropriate) which simulate actual loading conditions that will prevail during the design life of the rapid-rate system. This shall involve bench-scale or pilot-scale hydraulic testing with either the actual reclaimed water to be applied, or other water properly adjusted to correspond to the composition of the reclaimed water to be applied. The design loading rate shall allow for the expected gradual reduction in percolation rate due to long-term application of reclaimed water.

(2) The design hydraulic loading (and application) rate shall be related to the hydraulic conductivity and transmissivity and of the geologic formations at the project site which shall be evaluated in-depth by the permittee, with assistance from organizations or individuals qualified by training or experience in soil science, geology, and hydrology.

(3) Initial average annual hydraulic loading rates shall be limited to 3 inches per day, or 1.9 GPD/FT2, as an annual average where hydrogeologically feasible and as applied to the total bottom area of rapid infiltration basins, percolation cells, or absorption fields. For absorption fields, the bottom area shall be calculated by multiplying the bottom width of the absorption field trench by the length of the absorption field application/distribution lines. An applicant may request higher average annual loading rates based on justification provided in the engineering report, but such rates shall not exceed 9 inches per day (5.6 GPD/FT2), unless the requirements of Rule 62-610.525, F.A.C., are met. The average annual hydraulic loading rate shall be related to the clear water saturated vertical hydraulic conductivity for the most restrictive layer in the unconsolidated medium underlying the site. However, application rates during the loading cycle for individual rapid infiltration basins, percolation cells, or portions of the absorption field comprising the system will depend on the average annual hydraulic loading rate and the loading/resting cycle for the system. Application rates during the loading cycle shall be conservative and shall not exceed 25 percent of the documented vertical hydraulic conductivity, as described above, to control ground water mounding and ensure hydraulic performance of the system. Application rates during the loading cycle may exceed the maximum average annual hydraulic loading rates specified above. Justification for the use of selected design hydraulic criteria shall be required in the engineering report. These design criteria shall be based on the pollutant load in the reclaimed water to be applied, the characteristics of the underlying soil and aquifer system, loading and resting cycles to be used, and other process design considerations (including denitrification reactions that may be incorporated into the facility’s design).

(4) Hydraulic loading and resting cycles shall be developed so as to restore operating percolation rates of the pond system to design levels by the end of the resting period. Hydraulic loading periods of 1-7 days with resting periods of 5-14 days to dry the cell bottoms and enable scarification or removal of deposited solids are required. Design loading and resting cycles and other maintenance measures required to ensure system performance shall be described in the engineering report. Systems which achieve restoration of design operating percolation rates on a diurnal cycle shall meet the requirements of Rule 62-610.525, F.A.C. Loading and resting cycles are required for absorption fields. Loading and resting periods for absorption fields may vary from the requirements for rapid infiltration basins, if the applicant provides an affirmative demonstration that the alternative loading and resting cycle will enable compliance with the ground water criteria at the edge of the zone of discharge.

(5) A ground water mounding analysis based on site-specific information shall be included in the engineering report. This analysis shall demonstrate acceptable long-term hydraulic performance of the system. The ground water mounding analysis shall demonstrate that the ground water mound will not intercept the ground surface during any portion of the loading cycle during any time of the year. The ground water mounding analysis shall demonstrate that increases in ground water elevations shall not interfere with reasonable uses of adjacent properties.

(6) Rapid infiltration basins, percolation ponds, basins, trenches, or cells shall be routinely maintained to control vegetation growth and to maintain percolation capability by scarification or removal of deposited solids.

(7) Rapid infiltration basin, percolation pond, and trench bottoms shall be designed, constructed, and maintained to be level.

(8) Provisions shall be made in the design to ensure reasonably uniform distribution of reclaimed water across the entire bottom area of rapid infiltration basins, percolation ponds, basins, or cells. Multiple discharge points (normally three or less) may be needed to accomplish this. Elaborate sprinkler distribution systems shall not be required for rapid infiltration basins. Absorption fields shall be designed and constructed to ensure reasonably uniform distribution of reclaimed water across each portion of the absorption field system.

(9) The physical characteristics of unconsolidated materials overlying the bedrock shall be such that direct rapid movement (short-circuit) of the applied reclaimed water to underlying aquifers does not occur, unless the requirements of Rule 62-610.525, F.A.C., are met.

Rulemaking Authority 403.051, 403.061, 403.087 FS. Law Implemented 403.021, 403.051, 403.061, 403.062, 403.085, 403.086, 403.087, 403.088 FS. History–New 4-4-89, Amended 4-2-90, Formerly 17-610.523, Amended 1-9-96, 8-8-99, 4-1-21.