(A) The following standards apply to construction within sinkholes and over karst springs. The Planning Director or designee may approve the construction of impervious surfaces (such as structures, parking areas, and driveways) over sinkholes and springs in accordance with the following requirement: The applicant shall obtain the services of an engineer (geotechnical engineer) licensed in the state with experience in the review and analysis of karst geologic features, practicing in accordance with KRS 322 to conduct a geological assessment report to recommend treatment and construction method. The Planning Director or designee may confer with other appropriate agencies (USGS (U.S. Geological Survey), KGS (state’s Geological Survey), Hoffman Environmental Research Institute (Western Kentucky University), NRCS (National Resource Conservation Service), and MSD (Metropolitan Sewer District)) in determining the significance of the feature(s) in question as well as the appropriateness of the proposed treatment. If the proposed treatment and construction method is approved then the licensed geotechnical engineer shall be on the construction site to observe and verify that the correct treatment was applied during construction. The licensed geotechnical engineer shall submit a letter to Planning and Design Services stating that the approved treatment method was applied.
(B) The following standards apply to sinkhole collapse features (including sinking stream sink-point and cave entrances):
(1) The Planning Director or designee may approve the construction of impervious surfaces (such as structures, parking areas, and driveways) with the exception of principal residential structures over sinkhole collapse features in accordance with the following requirement: The applicant shall obtain the services of an engineer (geotechnical engineer) licensed in the state with experience in the review and analysis of karst geologic features, practicing in accordance with KRS 322, to conduct a geological assessment report to recommend treatment and construction method. The Planning Director or designee may confer with other appropriate agencies (USGS (U.S. Geological Survey), KGS (state’s Geological Survey), Hoffman Environmental Research Institute (Western Kentucky University), NRCS (National Resource Conservation Service), and MSD (Metropolitan Sewer District)) in determining the significance of the feature(s) in question as well as the appropriateness of the proposed treatment. If the proposed treatment and construction method is approved, then the licensed geotechnical engineer shall be on the construction site to observe and verify that the correct treatment was applied during construction. The licensed geotechnical engineer shall submit a letter to Planning and Design Services stating that the approved treatment method was applied; and
(2) Where sinkhole collapse features are retained the applicant’s engineer (geotechnical engineer) licensed in the state with experience in the review and analysis of karst geologic features, practicing in accordance with KRS 322, shall determine the appropriate karst feature buffer based on their analysis of the particular collapse feature. At a minimum, this analysis shall take into account surrounding evidence of instability such as surrounding soil subsidence. The karst feature buffer shall be measured starting from the last closed contour line of the sinkhole collapse feature or from the downstream-most point of the sinking stream, or from the cave entrance dripline as determined in the field by the applicant’s licensed engineer or geologist. The filling of sinkhole collapse features may be approved by the Planning Director or designee based on an approved filing method designed by the applicant’s engineer (geotechnical engineer) licensed in the state with experience in the review and analysis of karst geologic features, practicing in accordance with KRS 322. No activities are permitted within the karst feature buffer except for regular maintenance of landscaping. Buffers located downslope of construction areas shall be physically screened with soil erosion and sediment controls approved by the MSD. The buffer shall include ground cover and tree plantings as follows.
(a) Trees listed on the preferred planting list (see § 155.178) may be planted within the buffer with approval from the Planning Commission staff landscape architect.
(b) Native ground cover in accordance with the preferred planting list (non-invasive) shall be planted within the buffer.
(C) The following standards apply to sinkholes (sinkhole watershed areas).
(1) Flow of surface water into a sinkhole low point or sinkhole collapse feature shall not be increased from predevelopment conditions as calculated within the geologic assessment report.
(2) The applicant shall ensure, to the satisfaction of the Metropolitan Sewer District, that there will be no increase in soil erosion and sediment pollution directed toward any cave entrance, sinkpoint of a perennial or intermittent sinking stream, or sinkhole collapse feature.
(3) Stormwater drainage from a land use that stores, manufacturers, processes, or distributes hazardous or potentially hazardous materials shall not be directed toward a sinkhole.
(4) Stormwater drainage from streets, parking lots, loading and unloading areas, and fuel service stations shall not be directed toward a sinkhole unless the water is pretreated prior to entry into a sinkhole or the drainage is part of a low impact development (LID) plan approved by the MSD for the site.
(D) If utilities are to be constructed within a sinkhole, the utilities shall be so constructed so as not to permit the flow of water along the utility line trench, and shall be imperviously diked at 30-foot intervals.
(E) Cave entrances shall not be modified except for the placement of a bat accessible gate to prevent human access.
(LDC § 4.9.5) Penalty, see § 155.999