- (a) Soil absorption areas utilizing pipe and gravel provide for a trench twenty-four inches (24”) wide, with a standard trench depth of eighteen inches (18”) from the bottom of the trench to the finished settled grade.
- (b) Systems designed with trench depths up to twenty-four inches (24”) may be utilized.
(c)
(1) There shall be a minimum of:
- (A) Six inches (6”) of gravel below the pipe; and
- (B) Two inches (2”) of gravel above the pipe.
- (2) A minimum of six inches (6”) of cover is required above the gravel bed or gravel substitute.
(d)
- (1) The trench depth may vary in those instances where the soil absorption area was designed to overcome limiting soil characteristics.
(2) Trench depths shall be:
- (A) Specifically called for in the designated representative’s design; and
- (B) Approved by the authorized agent.
- (e) The absorption area in square feet is twice the total length of the trenches.
- (f) The minimum spacing between the trenches shall be six feet (6’) between the trenches and eight feet (8’) center to center.
- (g) Increased separation between trenches is encouraged to enhance the effectiveness of the trenching system.