Okla. Admin. Code § 252:641-12-5

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

Section 252:641-12-5 - Evapotranspiration/absorption (ET/A) fields

(a)Location. All ET/A 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 ET/A field; or

(2) highest point of the permeable sidewall of a manufactured media system used in the ET/A field.

(c)Minimum linear length. All ET/A fields must meet the minimum length requirements set forth in Appendix H, Figures 11 and 12. 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 ET/A field.

(d)Trench length limitation. ET/A fields shall be constructed so that no sewage flows through more than a total of one hundred fifty linear feet (150') of perforated pipe in any given path.

(e)Trench spacing. The trenches in an ET/A field shall be spaced at least eight feet (8') apart, center to center.

(f)Trench width. All trenches in an ET/A field shall be twenty-four inches (24") wide.

(g)Trench depth. Each trench in an ET/A field shall have a uniform depth of at least eighteen inches (18") and no more than twenty-four inches (24"). The bottom of the trenches shall be level.

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

(i)Retention structure. Retention structures must be used between trenches of different elevations in ET/A fields. When a retention structure is used:

(1) the bottom of the outlet pipe of 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 ET/A fields:

(1) the trenches shall be backfilled with at least six inches (6") of clean sand to within two inches (2") of the ground level;

(2) the sand used to backfill the trenches shall be separated from the storage media by material that allows the flow of water but prevents the flow of sand; and

(3) after a trench is backfilled with sand, two to four inches (2"-4") of sandy loam soil shall be mounded over the trench.

(k)Layout examples. There are layout examples located in Appendix K, Figures 1, 2, and 4, Appendix L, and Appendix M, Figure 2.

Okla. Admin. Code § 252:641-12-5

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