Dams for water impoundments, pools, ponds, reservoirs and small lakes shall be planned, designed and constructed under the supervision of a qualified engineer and shall meet the approval of the Department of Conservation of the state.
(A) Earth dams. Minimum requirements for earth dams shall be as follows.
(1) Foundations. A minimum thickness of at least 24 inches of an impervious material is required for dams up to 12 feet. The entire area in which the dam is to be founded shall be free from all top soil, roots, vegetation, stones, rock or debris, and shall be plowed and roughed up to provide an interlocking tight bond with the new fill.
(2) Cores. Cores should have a width of 30% to 50% of the water head and shall be constructed of materials which will not lead to core failure and leaks.
(3) Crest. The crest shall be at least ten feet wide to allow adequate space for maintenance equipment and shall have sufficient height above the water surface (freeboard) to prevent waves from going over it.
(4) Slopes. The upstream slope shall not be steeper than three feet horizontal to one foot vertical and shall be sufficiently protected from ice and wave action by an impervious earth blanket, riprap or concrete. The downstream slope shall not be steeper than two feet horizontal to one foot vertical and shall be protected against erosion by a growth of permanent sod.
(5) Drainage. Sufficient drainage and “reverse filtering” facilities to insure the permanent stability of the dam and its foundation shall be provided. Proper precautions shall be taken to prevent any seepage along drain pipes running through the dam.
(6) Spillways. Facilities for handling the maximum normal surplus waters shall be provided, together with a sodded relief spillway constructed 18 inches above the normal water level. Proper precautions shall be taken to prevent seepage along any of the spillways facilities constructed within the dam.
(7) Materials. All materials, equipment and construction methods shall conform to the requirements of the American Association of State Highway Officials Specifications for Highway Bridges and the Standard Specifications.
(8) Test and analysis. Results of the following tests and analysis shall accompany all plans for dams:
(a) Tests of the foundation material showing compressibility, shear strength and permeability;
(b) A complete stability analysis of the proposed dam using any of the available analysis techniques; and
(c) Permeability tests of the proposed core materials.
(B) Masonry dams. Minimum requirements for masonry dams shall include provisions to insure proper foundation bearing and for the prevention of slippage, excessive seepage, “piping” and scouring. The structure shall be designed by a registered structural engineer. The design and construction requirements shall conform to the American Association of State Highway Officials Specifications for Highway Bridges and the Standard Specifications.
(C) Existing dams.
(1) An engineering report shall be submitted to the Plat Officer on all existing dams within a proposed subdivision.
(2) Any dam found to be structurally unsafe shall be reconstructed or reinforced in accordance with the above standard.
(2007 Code, § 34-7-9)