(A) Required. Percolation tests may be required to be conducted in the presence of a designated county official and shall be required in all areas where septic tanks or other soil absorption systems proposed. Where grading is to be done, these tests shall be made in the soil after a finished grade has been constructed. At least three separate percolation tests shall be performed at the site of each proposed disposal area. More than two percolation tests will be required when the soil structure may vary or where large disposal areas are required. Preliminary tests for subdividing large tracts shall be made in the amount of one test hole per acre or as prescribed by this Department. Percolation tests shall not be made in frozen ground. The test shall not be made in filled ground unless the soil has been compacted or allowed to settle to the satisfaction of this Department.
(B) Procedure for conducting percolation tests. Percolation tests shall be performed in accordance with the following procedures:
(1) Type of test hole. Dig or bore a hole with horizontal dimensions of approximately four or six inches in diameter to the depth of the proposed seepage field or seepage bed.
(2) Preparation of a test hole. Carefully scratch the bottom and sides of the hole with a knife blade or sharp pointed instrument to provide a natural soil interface into which water may percolate. Remove all loose material from the hole. Add two inches of coarse gravel to protect the bottom from scouring and sediment.
(3) Saturation and swelling of the soil. Pre soak the hole four hours before conducting the test by carefully filling the hole with clear water to the ground surface. At the time of the test, refill the hole to a level 12 inches above the gravel. Allow the level to fall six inches and then commence measuring the drop in water level at 30-minutes’ intervals for the last six inches of seepage. The results of the percolation tests shall be given to the homeowner in writing or shall be retained by the contractor for at least five years.
(C) Recording of results. Record results of all tests as the total minutes required for the last six inches of seepage. The results of the percolation tests shall be given to the homeowner in writing or shall be retained by the contractor for at least five years.
(D) Soil classification systems. In areas where soil maps, soil charts, and soil descriptions are available, information regarding the type of soil present may be used as a guide.
(E) Calculation of seepage field area required. Subsurface seepage fields, if found to be acceptable by percolation tests, shall be designed and constructed in accordance with § 93.062(F), (G), (H).
(F) Subsurface seepage field; dosage rate.
Time required for water to fall six inches (minutes)
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Effective absorption area required in bottom of seepage fields (square feet per bedroom)
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Maximum rate of sewage application (gallons per square foot per day) for subsurface seepage fields, seepage beds
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Time required for water to fall six inches (minutes)
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Effective absorption area required in bottom of seepage fields (square feet per bedroom)
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Maximum rate of sewage application (gallons per square foot per day) for subsurface seepage fields, seepage beds
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30 | 130 | 2.2 |
60 | 165 | 1.6 |
90 | 210 | 1.3 |
120 | 235 | 1.1 |
150 | 265 | 1 |
180 | 290 | 0.9 |
240 | 320 | 0.8 |
300 | 350 | 0.7 |
360 | 385 | 0.6 |
(1) Absorption area is figured as trench bottom area.
(2) Over 180 is unsuitable for seepage pits.
(3) Over 360 is unsuitable for absorption systems.
(G) Minimum standard for seepage field construction.
The following are minimum standards.
Seepage Field Construction Standard
| Minimum
|
Individual lines, maximum length | 100 feet |
Trench bottom, minimum width | 18 inches |
Trench bottom, maximum width | 36 inches |
Field tile, minimum diameter | 4 inches |
Field tile lines, maximum slope | Level |
Variation of the above requirements is subject to approval by the department. | |
(H) Seepage field construction minimum standard.
(1) The following are minimum standards.
Width of trench at bottom (inches) | Recommended depth of trench (inches) | Center to center spacing tile lines* (feet) | Absorption area per lineal foot of trench (square feet) |
18 | 24 to 36 | 6 | 1.5 |
24 | 24 to 36 | 6 | 2 |
30 | 24 to 36 | 7.5 | 2.5 |
36 | 24 to 36 | 9 | 3 |
* A greater spacing is desirable where available area permits * Variation of the above requirements is subject to approval by the Department | |||
(2) These requirements for sewage disposal installations are as per the Private Sewage Disposal Licensing Act and Code, State of Illinois, Department of Public health, 1974. The remainder of the requirements can be found in this publication.
(Ord. 2014-18, passed 4-16-2014)