§ 30-265. Design and construction.

All conventional private on-site wastewater systems shall be constructed and designed to comply with the following requirements:

(1)

Materials. The septic tank shall be constructed of structurally sound, reinforced concrete and shall be watertight. Use of other materials may be permitted, if, in the opinion of the health officer, they are equal to, or better than, reinforced concrete.

(2)

Liquid capacity. The minimum liquid capacity shall be two and one-half times the daily wastewater flow using 150 gallons per bedroom or 1,000-gallon tank, whichever is greater.

(3)

Liquid depth. The tank liquid depth (distance from outlet invert to bottom of tank) shall be at least three feet but shall not exceed six and one-half feet.

(4)

Inlets. The invert of the inlet shall be located at least three inches above the invert of the outlet. The inlet shall be provided with a tee-fitting or baffle, which shall extend at least six inches below the liquid level and above the liquid level to one inch below the top of the tank lid.

(5)

Outlet baffles. There shall be a baffle or tee-fitting at the outlet end of the tank. The baffle or tee-fitting shall extend at least eight inches above the liquid level and 18 inches below the liquid level in the tank.

(6)

Air space. At least ten inches of air space shall be provided between the top of the liquid level and the bottom of the tank lid.

(7)

Access. Septic tanks shall have an access manhole with 20 inches minimum dimension for each compartment. All below grade attachments to the tank, fittings, risers, extensions and lid shall be watertight. The manhole shall be child and tamper resistant; lids weighing at least 65 pounds, locks or anchors that are not removable without special tools may be used to accomplish this.

(8)

Minimum cover. The top of the tank shall not be located less than four inches below finish grade.

(9)

Inspection risers. Risers no larger than six inches in diameter shall extend to the surface grade and be centered over the inlet and outlet tees.

(10)

Inlet/outlet inserts. All septic tanks shall be manufactured with a flexible insert for the inlets and outlets.

(11)

Subsurface absorption field. The subsurface absorption field shall be designed and constructed to conform with the standards in this section.

(12)

Area. No subsurface absorption field shall have less than 500 square feet of effective absorption area. The health officer may increase the effective absorption area required based upon the percolation test and potential water usage.

(13)

Minimum trench width. The absorption trench shall be of uniform width and shall not be less than 24 inches or more than 36 inches wide.

(14)

Maximum trench length. No single trench shall be more than 100 feet in length.

(15)

Trench spacing. Absorption trenches shall have at least 12 feet of undisturbed soil between them.

(16)

Depth of trenches. No absorption trench shall be less than 27 inches or more than 39 inches deep unless approved in writing by the health officer.

(17)

Trench bottom. The bottom of the trench shall be level from end to end.

(18)

Gravel. A minimum of 15 inches of clean gravel or crushed stone three-fourths inch to two inches in size shall be placed in all absorption trenches.

(19)

Lateral trench. A lateral trench shall be installed on top of at least six inches of clean gravel, sized from three-fourths inch to two inches. Perforated pipe shall be laid on the top of and in the center of the six inches of clean gravel. An approved standard trench pipe of rigid PVC ten feet in length shall be used. The pipe shall be covered with six inches of the same type of clean gravel. All pipe shall be four inches in diameter and have at least a 3,000-pound crush rating.

(Code 1988, § 30-304; Ord. No. O-46-05, § 1, 6-2-2005; Ord. No. O-51-18 , § 8, 12-6-2018)