SECTION 252:641-3-2. Soil Percolation test

(a)   Use of percolation tests. A percolation test may only be used to identify dispersal sites for conventional subsurface absorption fields. Percolation tests, including pre-existing ones, may not be used to identify dispersal sites for on-site sewage systems:

(1)   in scenic river corridors, unless documentation that the site is not located within the scenic river watershed is provided to DEQ; and

(2)   in Zone 2 of a water body protection area.

(b)   Test hole requirements. The following test hole requirements shall be met for percolation tests:

(1)   Configuration. Three test holes shall be placed in the proposed dispersal site at the approximate corners of an isosceles triangle having two (2) sides fifty feet (50') long and one side seventy-five feet (75') long. If the dispersal field will cover an area larger than ten thousand square feet (10,000 ft), then one additional test hole shall be used for each additional five thousand square feet (5,000 ft). Additional test holes shall not be placed within fifty feet (50') of any other test hole and shall be located between fifty to seventy-five feet (50'-75') from one of the other test holes. The DEQ may approve or require alternative configurations.

(2)   Size. Test holes shall be dug or bored, four to twelve inches (4"-12") in diameter with vertical sides to a depth of at least twenty-four inches (24") and no more than thirty-six inches (36"). All test holes in the proposed dispersal site shall be the same depth. Test holes shallower than twenty-four inches (24") may be used to design conventional subsurface absorption fields under the alternative system approval process.

(3)   Soil surfaces. The bottoms and sides of the test holes shall be scratched with a sharp-pointed instrument to relieve any smeared soil surfaces. Loose material shall be removed from the hole prior to commencing the presoak.

(4)   Prohibitions. Test holes dug through animal burrows, root channels or soil that is cracked due to dry weather conditions shall not be used.

(c)   Presoak period. The presoak period shall commence no earlier than twenty-four (24) hours prior to the start of the percolation test procedure. Each test hole shall be presoaked by filling them with water and refilling them as necessary to maintain a water depth of at least twelve inches (12") for at least four (4) hours. When it is impossible to maintain a water depth of at least twelve inches (12") during the entire presoak period due to an excessive percolation rate, then the hole is deemed unacceptable and may not be:

(1)   used to calculate the percolation rate for the dispersal site; and

(2)   located in the dispersal site for a conventional subsurface absorption field.

(d)   Calculating the percolation rate for each hole. At the completion of the presoak, the depth of the water shall be adjusted to ten inches (10") above the bottom of each test hole. A fixed reference point shall be established at or above the initial water level. Using the fixed reference point, the level of the water in each hole shall be measured and recorded. After seventy-five (75) minutes, the number of inches the water level has dropped in each hole shall be measured and recorded. To calculate the percolation rate for each individual hole, divide seventy-five (75) minutes by the number of inches the water level has dropped. Any hole that exhibits a percolation rate of greater than seventy-five (75) minutes per inch is deemed unacceptable and may not be:

(1)   used to calculate the percolation rate for the dispersal site; and

(2)   located in the dispersal site for a conventional subsurface absorption field.

(e)   Calculating the percolation rate for the dispersal site. If the rates of any two (2) test holes in the proposed dispersal site vary by more than fifteen (15) minutes, the percolation rate for the dispersal site shall be considered the rate of the slowest test hole. Otherwise, the percolation rate for the dispersal site shall be determined by averaging the percolation rates for the three (3) test holes and then rounding the result to the nearest whole number. If there are more than three (3) test holes in the proposed dispersal site, then the percolation rate must be calculated using the three (3) slowest percolation rates.

(f)   Sizing the dispersal field. The percolation rate for the dispersal site shall be used in conjunction with the charts in Appendix H, Figures 1 and 4 to size the conventional subsurface absorption field. The chart in Appendix H, Figure 2 may be used to size conventional subsurface absorption fields utilizing chambers when designed using a percolation test.

(g)   Information to be reported. The following information must be reported to the DEQ on DEQ Form 641-581P, "Report for On-Site Sewage Treatment" or in a format approved by the DEQ:

(1)   Property owner's name(s);

(2)   Address or finding directions for property;

(3)   Legal description of property, including lot and block number when available;

(4)   Lot size in square feet or acres;

(5)   Whether the system will be an individual or small public on-site sewage treatment system;

(6)   The estimated or actual average daily flow for the system as certified on DEQ Form 641-581Cert "Certification Documentation Form";

(7)   Whether the water supply for the property is public or private;

(8)   The location of each test hole (identified from two fixed reference points);

(9)   The depth and percolation rate, along with the depth to groundwater if encountered, for all test holes in the proposed dispersal field;

(10)   The percolation rate for the dispersal site;

(11)   The size of the septic tank, the minimum length of the conventional subsurface absorption field, and the minimum and maximum depth of the trenches;

(12)   The name and signature of the person performing the pre-soak;

(13)   The name, signature and registration number of the person conducting the percolation test; and

(14)   The date the percolation test was conducted.

[Source: Added at 16 Ok Reg 1895, eff 6-11-99; Amended at 19 Ok Reg 45, eff 8-17-01 (emergency); Amended at 19 Ok Reg 1027, eff 6-1-02; Amended at 21 Ok Reg 1618, eff 6-11-04; Amended at 25 Ok Reg 2318, eff 7-11-08; Added at 28 Ok Reg 1278, eff 7-1-11; Amended at 29 Ok Reg 1053, eff 7-1-12; Amended at 37 Ok Reg 1296, eff 9-15-20]