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Illinois Administrative Code (Last Updated: March 27, 2024) |
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TITLE77. PUBLIC HEALTH |
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PART905. PRIVATE SEWAGE DISPOSAL CODE |
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Section905.APPENDIX A. Illustrations and Exhibits |
§905.ILLUSTRATION M. Soil Suitability for On-Site Sewage Design
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Section 905.APPENDIX A Illustrations and Exhibits
Section 905.ILLUSTRATION M Soil Suitability for On-Site Sewage Design
Section 905.EXHIBIT A Loading Rates in Square Feet Per Bedroom and Gallons/Square Feet/Day
Design Group
Soil Group
(Most Limiting
Layer)
Minimum Separation To Limiting Layer1
Permeability Range
Size of System
Residential Reg. Absorption (ft2/bedroom)
Institutional/Commercial Allowable Application Rate (GPD/ft2)
I
1A
NR3
Very Rapid
NR3
NR3
II
2A; 2B; 2K
3 feet
Rapid
200
1.0
III
3B; 3K
3 feet
High Moderately Rapid
220
0.91
IV
3A; 3L; 4D; 4K
3 feet
Low Moderately Rapid
240
0.84
V
4A;; 4B; 4H; 4L; 5D
3 feet
Very High Moderate
265
0.75
VI
4F; 4M; 5B
3 feet
High Moderate
290
0.69
VII
4N; 5A; 5C; 5H; 5K; 6D
2 feet
Moderate
325
0.62
VIII
4O; 5E; 5I; 5L; 6A; 6B; 6E; 6H; 6K
2 feet
Low Moderate
385
0.52
IX2
5F; 5M; 6C; 6L; 7D; 7F
2 feet
High Moderately Slow
445
0.45
X2
5G; 6F; 6I; 7E; 7C; 7H
2 feet
Low Moderately Slow
500
0.40
XI2
5N; 6G; 6J; 6M; 7F; 7I
2 feet
Slow
740
0.27
XII2
7G; 7J; 7L; 8E; 8I
2 feet
Very Slow
1000
0.20
XII2
5O; 6N; 6O; 7M; 7N; 7O; 8J; 8M; 8O
NR3
NR3
NR3
0.00
XIII
9
SUBSURFACE DISPOSAL NOT RECOMMENDED
NOTES:
1 Limiting layers include fragipans; bedrock; compact glacial tills; seasonal high water table or other soil profile features that will materially affect the absorption of liquid from the disposal field.
2 Soils in this group are less than the minimum percolation rate established in Appendix A, Illustration H as suitable for subsurface seepage systems.
3 NR = Subsurface disposal system not recommended.
(Source: Amended at 37 Ill. Reg. 14994, effective August 28, 2013)
Section 905.APPENDIX A Illustrations and Exhibits
Section 905.ILLUSTRATION M Soil Suitability for On-Site Sewage Design
Section 905.EXHIBIT B Key for Determining Sewage Loading Rates (Gallons/Square Foot/Day)
Structure and
Parent Material
Single grain; Weak ;
Platy2
Granular, Angular and Subangular Blocky; Prismatic
Structureless or Massive
Loess: Outwash; Alluvium; Lacustrine8
Till3
Week
Moderate; Strong
Strong
Moderate; Strong
Loess; Outwash; Alluvium; Lacustrine8
Till3
Moist Consistence
lo vfr fr
vfr fr
fi
vfr
fi
vfr fr
fi
fr
fi
vfi
vfr
fr
fi
vfr fr
fi vfi
Texture
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
1.
Fragmental; Ext. or Very gravelly sand
> 1.004
N/A5
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2.
Sand; Loamy course sand; Loamy sand; Gravelly sand; Coarse sand; Gravelly loamy sand
1.00
1.00
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1.00
N/A
N/A
N/A
N/A
3.
Fine sand; Loamy fine sand; Coarse sandy loam
0.84
0.91
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.91
0.84
N/A
N/A
N/A
4.
Sandy loam; Fine sandy loam; Gravelly sandy loam; Gravelly loam; Gravelly silt loam
0.75
0.75
N.A
0.84
N/A
0.69
N/A
N/A
0.75
N/A
0.84
0.75
0.69
0.62
0.52
5.
Loam; Silt loam; Very fine sandy loam; Sandy clay loam; Silt; Very fine sand; Loamy very fine sand; Gravelly clay loam
0.62
0.69
0.62
0.75
0.52
0.456
0.406
0.62
0.52
N/A
0.62
0.52
0.456
0.276
N/R7
6.
Silty clay loam (<35% c); Clay loam (< 35% c)
.052
0.52
0.456
0.62
0.52
0.408
0.276
0.52
0.406
0.276
0.52
0.456
0.276
N/R
N/R
7.
Silty clay loam (>35% c); Clay loam (>35% c)
N/A
N/A
0.406
0.456
0.406
0.276
0.206
0.406
0.276
0.206
N/A
0.206
N/R
N/R
N/R
8.
Sandy clay; Clay
N/A
N/A
N/A
N/A
0.206,9
N/A
N/A
N/A
0.206,9
N/R
N/A
N/A
N/R
N/A
N/R
9.
Organics; Fragic; Lithic; Paralithic
–––SOIL PROPERTIES HAVE VERY SEVERE LIMITATIONS; SUBSURFACE DISPOSAL NOT RECOMMENDED–––––
FOOTNOTES:
1 Disturbed soils are highly variable and require special on-site investigations.
2 Moderate or strong platy structure for the soil textures in Groups 4, 5 and 6 have a loading rate of 0.40 g/sq.ft/d. Platy structure having firm or very firm consistency or caused by mechanical compaction has a loading rate of 0.0 g/sq.ft/d.
3 Basal glacial tills structured by geogenic processes have the same loading rates as structureless glacial till.
4 This soil group is estimated to have very rapid permeability and exceeds the maximum established rate in Illustration H, Exhibit A.
5 N/A means not applicable.
6 These soil groups are estimated to have moderately slow to very slow permeability and are less than the minimum established rate in Illustration H, Exhibit A.
7 N/R means not recommended. These soils have loading rates considered too low for conventional subsurface disposal.
8 In some areas, lacustrine material may have physical properties similar to glacial till and should be placed in the glacial till columns.
9 Non-swelling (1:1 lattice) clays formed in bedrock residuum have a loading rate of 0.27 g/sq.ft/d. Swelling (2:1 lattice) clays are not recommended for subsurface disposal.
(Source: Amended at 37 Ill. Reg. 14994, effective August 28, 2013)