Minimum requirements for earth dams shall be as follows:
(A) A minimum thickness of 24 inches of an impervious clay or equivalent is required for dams up to 12 feet in height. The entire area of the foundation shall be free of 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.
(B) A clay core shall be constructed within the middle one-third of the dam, and extending into a ten- foot wide trench excavated at least 12 inches into impervious clay.
(C) The crest shall meet the following requirements:
10 feet wide for dam under 15 feet in height
12 feet wide for dam 15 feet to 25 feet in height
14 feet for dam over 25 feet in height
and shall provide for a minimum of one foot of free board above the water surface in the reservoir with the emergency spillway flowing at design depth. In all cases the top of the dam must be at least two feet above emergency spillway crest.
(D) The upstream slope shall not be steeper than two feet horizontal to one foot vertical and shall be sufficiently protected from ice and wave action by an impervious earth blanket, ripraps, concrete, or berms constructed at the normal pool elevation. The downstream slope shall not be steeper than two and one-half feet horizontal to one foot vertical and shall be protected from erosion by a growth of permanent sod.
(E) 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 drainpipes running through the dam.
(F) Facilities for handling the maximum normal surplus waters shall be provided, together with a sodded relief spillway constructed 12 inches above the pool level. Proper precautions shall be taken to prevent seepage along any of the spillway facilities constructed within the dam. All dams over five feet high shall be sodded.
(G) All materials, equipment, and construction methods shall conform to the standards of the County Public Works Department.
(H) In those cases where failure of the structure could result in loss of life or extensive property damage, additional requirements may be made.
(Ord. 76-O-10, passed 9-21-76)