Okla. Admin. Code § 252:641-12-2

Current through Vol. 42, No. 7, December 16, 2024

Section 252:641-12-2 - Conventional subsurface absorption fields

(a)Location. All conventional subsurface absorption fields shall be:

(1) located in the identified dispersal site; and

(2) installed more than five feet (5') from the septic tank or aerobic treatment unit.

(b)Fall. Unless a pump is utilized, there shall be a minimum fall of two inches (2") from the bottom of the outlet of the septic tank to the:

(1) highest point of the storage media in the conventional subsurface absorption field; or

(2) highest point of the permeable sidewall of amanufactured media system used in the conventional subsurface absorption field.

(c)Minimum linear length. All conventional subsurface absorption fields must meet the minimum length requirements set forth in Appendix H, Figures 1-6.An optional reduction of the required minimum length is available as set forth in Appendix H, Figures 3 and 4. A reduction of fifteen (15) percent is established for Net Evaporation Zones 6-8 and a reduction of thirty (30) percent is established for Net Evaporation Zones 9 and 10. If perforated pipe is used between distribution structures and installed in accordance with the trench requirements of this Section, it may be counted as part of the overall required length of the conventional subsurface absorption field.

(d)Trench length limitation. Conventional subsurface absorption fields shall be constructed so that no sewage flows through more than a total of one hundred fifty linear feet (150') of perforated pipe or manufactured media system in any given path.

(e)Trench spacing. The trenches in a conventional subsurface absorption field shall be spaced at least eight feet (8') apart, center to center.

(f)Trench width. All trenches in a conventional subsurface absorption field shall be twenty-four inches (24") wide.

(g)Trench depth. Each trench in a conventional subsurface absorption field shall have a uniform depth of at least eighteen inches (18"), and no more than thirty inches (30"). The bottom of the trenches shall be level.

(h)Dispersal and storage. Each trench in a conventional subsurface absorption field shall contain a zone for the dispersal and storage of effluent with a total depth of at least ten inches (10"), comprised of either perforated pipe and storage media or a manufactured media system.

(i)Retention structure. Retention structures must be used between trenches of different elevations in conventional subsurface absorption fields. When a retention structure is used:

(1) the bottom of the outlet pipe of a retention structure or the bottom of the outlet pipe of a manufactured media system being used as a retention structure shall be ten inches (10") above the trench bottom; and

(2) the line from the outlet of a retention structure to the next distribution point shall be constructed of solid pipe and shall be backfilled with compacted native soil.

(j)Backfill. For conventional subsurface absorption fields:

(1) the depth of the backfill shall be consistent and shall not vary more than four inches (4"); and

(2) the backfill shall consist of at least eight inches (8") of topsoil.

(k)Layout examples. There are examples of conventional subsurface system layouts in Appendix K, Figures 1, 2, and 4; examples of retention and distribution structures in Appendix L; and examples of trench installation in Appendix M, Figures 1 and 2.

Okla. Admin. Code § 252:641-12-2

Added at 25 Ok Reg 2318, eff 7-11-08

Amended by Oklahoma Register, Volume 37, Issue 24, September 1, 2020, eff. 9/15/2020

Amended by Oklahoma Register, Volume 38, Issue 10, February 1, 2021, eff. 1/4/2021

Amended by Oklahoma Register, Volume 38, Issue 24, September 1, 2021, eff. 9/15/2021