(a)

1. (1) Careful construction is important in constructing a satisfactory absorption area.
2. (2) Attention shall be given to the protection of the natural absorption properties of the soil.
3. (3) Care shall be taken to prevent sealing of the surface on the bottom and sides of the trench.
4. (4) Trenches shall not be excavated when the soil is wet enough to smear or compact easily.
5. (5) When significant smearing of the sidewalls or bottom of the absorption trench occurs during installation, construction shall be halted and the local authorized agent shall be contacted for guidance.
6. (6) During the wet season periods of the year or after any significant rainfall event, failure to obtain authorization from the local authorized agent for beginning construction of an onsite wastewater system may void the onsite wastewater system permit.
7. (7) Open trenches shall be protected from surface run-off to prevent the entrance of any silt and debris.
8. (8) If it is necessary to walk in the trench, a temporary board laid on the bottom will reduce damage by compaction.
9. (9) Smeared or compacted surfaces shall be raked to a depth of one inch (1”), and loose material removed, before the gravel is placed in the trench.
10. (10) Perforated pipes shall be bedded on undisturbed earth to prevent settling.

11. (11) Lateral lines shall be surrounded by:

    1. (A) Clean, graded gravel;
    2. (B) Washed rock; or
    3. (C) Other authorized aggregate.
12. (12) The aggregate material may range in size from one-fourth inch (1/4”) to one and one-half inches (1 1/2”).

(b)

1. (1) The top of the gravel shall be covered with untreated building paper or other authorized materials before placing the earth backfill.
2. (2) This will help prevent the gravel from becoming clogged with the earth.
3. (3) An impervious covering shall not be used, as this interferes with evaporation.
4. (4) The cover over a new absorption trench shall be adequately overfilled to allow for settling.

(d) Distribution boxes/devices.

1. (1) A distribution box/device is required for every standard absorption system.
2. (2) Distribution devices shall be designed for serviceability, including but not limited to, risers to grade.
3. (3) The purpose of the box/device is to ensure equal distribution of septic tank effluent to the lateral lines.
4. (4) It is important that the entrance to each lateral line from the distribution box be set at the same elevation to attempt to ensure equal flow into all lines.
5. (5) The design of the distribution box and absorption system can be varied to meet most topographical conditions encountered while giving proper grade and alignment for all laterals.

6. (6) Distribution boxes shall be:

   1. (A) Sealed;
   2. (B) Bedded in concrete or gravel on undisturbed ground; and
   3. (C) Water leveled with leveling devices.

7. (7) Distribution boxes shall have an easily removable cover to facilitate:

   1. (A) Leveling;
   2. (B) Inspection; and
   3. (C) Repairs.
8. (8) Inlet and outlet lines at the distribution box shall be installed in such a manner as to be firmly supported and adequately sealed as approved by the authorized agent.

9. (9)

   1. (A) Where the elevation across the absorption area is greater than six inches (6”), the outlet invert (flowline) of the distribution box shall be installed at an elevation equal to or greater than the finished ground elevation of the highest line of the absorption area.
   2. (B) See Appendix G, Figure 2.

(e) Septic tanks.

1. (1) On sites that do not have sufficient slope to allow the distribution box to be installed as in subsection (d) of this section, the flow line of the septic tank outlet shall be at an elevation equal to or greater than the finished ground elevation of the highest line of the absorption area.
2. (2) See Appendix G, Figure 1.

(f)

1. (1) Absorption trenches shall not start closer than five feet (5’) from the distribution box.
2. (2) A horizontal separation of five feet (5’) shall be required between the absorption area and tight line trench.
3. (3) In systems utilizing a distribution box, lateral lines shall be of the same length.
4. (4) Distribution devices used in conjunction with soil absorption systems shall be approved by the Department of Health prior to their use or installation.

(g)

1. (1) The tight line or manifold trench shall not be excavated lower than the flow line of the trench media to be installed.
2. (2) However, in no case will the tight line trench be excavated lower than twelve inches (12”) from the ground surface.

(h)

1. (1) Materials used in the construction of the onsite wastewater system shall meet the following requirements.
2. (2) New products may be authorized by the department as technology allows.