A.    Existing Stormwater Storage. Existing sinkhole stormwater storage volume will be maintained and the volume of stormwater storage provided to meet the requirements of this chapter of the city’ s municipal code shall be in addition to existing stormwater storage at the sinkhole and sinkhole area.

    B.    Stormwater Drainage into Sinkholes. Sinkholes shall be protected from damaging modifications and adverse changes in stormwater runoff quantity and quality associated with land developments. In addition to the other requirements of this code, the following requirements shall be met for all development whose drainage flows into a sinkhole:

    1.    Stormwater Detention in Sinkholes. Existing stormwater storage areas shall not be modified for the purposes of stormwater detention unless it is demonstrated that the proposed modification will maintain or improve its habitat and ability to perform beneficial functions. Existing storage and release rate characteristics of sinkhole storage areas shall be maintained and the volume of detention storage provided to meet the requirements of this section of this chapter of the city’ s municipal code shall be in addition to that existing storage.

    2.    Sediment Control. The existing sinkhole storage areas shall be protected during construction and shall not be filled or sediment allowed to deposit therein.

    3.    Alteration of Drainage Patterns. Site drainage patterns shall not be altered to substantially decrease or increase the existing area tributary to a sinkhole.

    4.    Detention/Sedimentation. If a detention/ sedimentation basin is required for site development, it shall be designed to capture the critical storm event and hold it for a minimum of twenty-four (24) hours. This basin shall be maintained throughout the construction process.

    5.    Vegetated Buffer Strip. A buffer strip of at least twenty-five (25) feet in width, preferably vegetated with native plant species, shall be maintained or restored around the periphery of a sinkhole.

    6.    Loessal Soils. Care should be taken to avoid open flow discharges of stormwater over silt (loessal) soils due to high potential for erosion.

    7.    Sinkholes in Karst Areas. Sinkholes in karst areas should be considered as receiving waterways and all predetention and erosion requirements shall apply. The filling, grading, and excavating of sinkholes is prohibited unless an erosion control site plan is approved by the city engineer in accordance with Section 17.51.030 of this chapter and any development in the sinkhole area is in compliance with Section 17.51.040 of this chapter. (Ord. 1872 § 2 (part), 2000)