(A) Grading plan. The final grading plan for the subdivision shall be submitted to and approved by the Planning and Zoning Board, the Planning Director, Highway Department, and the County Commission. The plan shall include the following:
(1) Final Site Grading Plan. The grading plans shall show the contours with intervals acceptable to the Planning Director. The site grading plan shall also show drainage arrows for each lot; and
(2) Final Grading Plan. The road grading plan shall show percent slope for all proposed roads, drainage arrows, and location and size of culverts.
(3) Planning and Zoning Board, Planning Director, Highway Department, and County Commission may require engineered stamped plans.
(B) Drainage Plan. All drainage facilities including on-site detention, drainageways, detention ponds, and drainage channels shall be shown on the drainage plan and are subject to the approval of the Planning and Zoning Board, Planning Director, Highway Department, and County Commission. The plan shall provide the following information:
(1) Existing and proposed contour lines and the surface water drainage system, including any major alteration of the existing drainage pattern. Drainageways and detention ponds shall be designed for a 25-year storm occurrence. The contour interval shall be of such detail that the final drainage pattern is adequately illustrated;
(2) The boundaries of all drainage easements and detention ponds. A maintenance agreement for upkeep of the detention ponds shall be filed as a separate agreement in conjunction with the plat;
(3) Individual lot drainage shall be coordinated with the general surface water drainage pattern for the area. Drainage shall be designed so as to avoid a concentration of storm drainage water from each lot to adjacent lots;
(4) Driveways shall not inhibit or restrict the flow of surface water. It shall be the responsibility of each lot owner to install and maintain a properly sized culvert under the driveway when construction commences to handle a 25-year storm occurrence, if needed; and
(5) Planning and Zoning Board, Planning Director, Highway Department, and County Commission may require engineered stamped plans.
(C) Erosion Control Plan. Stripping of vegetation, and cut and fill operations should be kept to a minimum, as should the amount of land and the duration of exposure. Whenever feasible, development plans should be made in conformance with topography in order to create the least erosion potential. Similarly, as much as possible, natural vegetation shall be retained, protected, and supplemented. Every effort shall be made to retain the natural vegetation on all ditches and drainageways. Ditches and drainageways will not be disturbed without the approval of the County Commission. The plan shall include the following:
(1) All proposed land disturbance including areas of excavation, grading, filling, removal, or destruction of topsoil and spreading of earth material;
(2) Provisions for erosion control during construction will include the sequence of the operations listed above, with an estimated time of exposure. The proposed temporary measures to control erosion will be designed to withstand two-year rain and be shown on the plan;
(3) Existing natural features which would add value to residential development or to the community as a whole, such as trees, watercourses, and similar irreplaceable assets, should be preserved in the design of the subdivision; and
(4) Compliance with South Dakota Department of Agriculture and Natural Resources with disturbance greater than an acre.
(Ord. 14-04, passed 6-30-2015, Ch. 7, Art. 5; Ord. 24-01, passed 5-14-2024)