Illinois Administrative Code
Title 77 - PUBLIC HEALTH
Part 905 - PRIVATE SEWAGE DISPOSAL CODE
Appendix A - Illustrations and Exhibits
ILLUSTRATION H - Subsurface Seepage System Size Determination
Exhibit A - Gravel System
Time (minutes) required for last 6 inches of water to fall |
FOR RESIDENTIAL USE Required Absorption Area (sq ft)/bedroom) |
FOR INSTITUTIONAL OR COMMERCIAL USE Allowable application rate (GPD/sq ft) (5) |
Recommended depth from bottom of the trench to the limiting layer |
|
18 - 60 |
200 |
1.0 |
||
90 |
210 |
.95 |
3 feet |
|
120 |
235 |
.85 |
||
150 |
265 |
.75 |
||
180 |
290 |
.69 |
||
240 |
320 |
.62 |
||
300 |
350 |
.57 |
2 feet |
|
360 |
385 |
.52 |
||
NOTE: |
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1. |
Absorption area is figured as trench bottom area in absorption trenches and bottom area in seepage beds. |
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2. |
Seepage beds require 11/2 times the seepage field absorption area specified. |
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3. |
Over 360 is unsuitable for subsurface seepage systems. |
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4. |
Under 18 is unsuitable for subsurface seepage systems. |
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5. |
Divide the required total gallons per day by this number to get the number of square feet required |