(B) A subsurface sand filter shall have a minimum filter area of two hundred-forty square feet per bedroom unless the filter is dosed. When dosed the filter shall have a minimum filter area of three hundred square feet or one hundred twenty square feet per bedroom, whichever is greater. The total filter area shall be divided into two beds, each with a separate distribution system. Provision shall be made for alternating from one bed to the other by gravity or pumping.
(C) A dosing tank shall have a minimum working volume of seventy-five gallons, shall extend to grade, and shall be provided with secured covers.
(D) When a subsurface sand filter is dosed, the distribution system shall be vented to the surface of the ground at the lower end of each bed by one or more vented caps having a minimum inside diameter of four inches.
(E) All distribution lines shall have a minimum diameter of four inches and shall have a relatively level grade. The grade shall not exceed a fall of three inches in fifty feet.
(F) The distribution lines shall be installed within a minimum of twelve inches of clean gravel or stone three-fourths inch to one and one-half inches in size which covers the entire bed. The lines shall be laid on three foot centers, and eighteen inches from the sidewalls of the filter.
(G) The filtering material shall be a minimum of eighteen inches in depth and the sand shall be an effective size of four-tenths to one millimeter with a uniformity coefficient not to exceed three.
(H) The lower or collecting line shall have a minimum diameter of four inches and shall be laid the full length of the bed. The grade shall have a minimum fall of six inches in fifty feet.
(I) The collecting line shall be installed within a minimum of twelve inches of clean gravel or stone three-fourths to one and one-half inches in size which underlies the entire bed.
(J) The top of the filter shall be covered with a pervious material such as untreated paper or a two inch layer of hay, straw, or similar material before being covered with earth.
(K) The earth cover shall not exceed eighteen inches.
(L) A sampling well with a minimum inside diameter of eight inches shall be installed on the subsurface sand filter discharge line within six feet of the filter bed, accessible from the surface of the ground, and provided with a secured cover.
Promulgated Under: 119.04
Statutory Authority: Sec. 120.02 of Am. Sub. HB 119 (127th G.A.)
Rule Amplifies: Sec. 120.02 of Am. Sub. HB 119 (127th G.A.)
Prior Effective Dates: 7/1/1974, 7/1/77, 7/2/07