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1975). For projects of less than 12.0 acres, the rational method of runoff computation is satisfactory. The rainfall intensity - duration curves provided in Appendix A. attached hereto, are hereby incorporated as a part of this ordinance and shall be used in making all required hydrologic computations. (3) Retention or detention with filtration of the runoff from the first 1" of rainfall shall be provided on site. Detention with filtration or retention shall be provided on site for additional stormwater runoff generated by the development project over and above that generated by the site prior to the proposed development unless there is a legal positive outfall available which has sufficient capacity to accept the additional runoff. (4) Retention or detention facilities shall be constructed in such a manner as to maximize utilization of available perco- lation capabilities on the site for recharge enhancement and to minimize mosquito breeding by being shallow, shall be easy to maintain, and shall have a skimmer mechanism if required by the SJRWMD. Stormwater Management facilities shall not penetrate the groundwater table unless the following criteria are met: (a) The application provides a water quality certifi- cation from the SJRWMD or Florida DER that the direct connection to the groundwater table, as proposed, will not significantly detract from the quality of the groundwater. If the size of the development project is below SJRWMD or DER thresholds, this certification can be waived; (b) Dry retention/detention at the site is not appro- priate. The applicant's engineer or groundwater hydrologist shall provide a certified statement that soils are not suitable for dry retention/detention. Site supporting soils testing shall be included, (c) The, site is not located on the primary sand ridge or designated aquifer recharge area as delineated by the County's Environmental Planner, (d) Side slopes are 4' horizontal to 1' vertical and properly vegetated to 2' below the control elevation. (5) Discharges from the development project shall be handled to a point of legal positive outfall. Tailwater stages of the receiving waters, as reported in the Master Plan or as generated from data in the Master Plan, must be taken into account in design. Enlargement of existing downstream facilities may be required. (6) The bottom of dry retention areas shall be sloped at a minimum .2% to a permeable drain. A dry detention area shall have an outlet device, and shall not be lower than the elevation of the off-site receiving channel or water body.