(a) Filter sand shall be a hard, uniformly graded, silica material with effective particle sizes between 0.45 and 0.55 millimeters in diameter, with a uniformly coefficient of 1.45 to 1.69. There shall be no limestone, clay or deleterious matter present.
(b) Filter sand shall be no less than nineteen inches in depth with a freeboard of no less than nine inches or more than twelve inches.
(c) There shall be no less than four grades of rock, which shall be clean, noncrushed, rounded, nonporous, noncalcareous material.
(d) The total depth of the rock supporting bed shall be no less than fifteen inches and each grade shall be two inches or greater in depth. Each layer of rock shall be leveled to prevent intermixing of adjacent grades.
(e) The top layer shall vary in size between one-eighth and one-fourth inch. The next layer shall vary in size between one-fourth and one-half inch. The next layer shall vary in size between one-half and three-fourths inch. The bottom layer shall vary in size between one and one-half inches.
(Ord. B-751. Passed 7-9-62.)
(Ord. B-751. Passed 7-9-62.)