Ill. Admin. Code tit. 77, pt. 906, app A, exh. A

Current through Register Vol. 49, No. 2, January 10, 2025

Exhibit A - Soil and Site Factors that Restrict Mound Systems

Soil Group
Slowly Permeable Soils	Permeable Soils With Pervious Bedrock	Permeable Soils With High Water Tables
Percolation rate a	180-360 min.	18-180 min.	18-180 min.
Depth to pervious rock	24 in.	24 in.	24 in.
Depth of high water tables	24 in.	24 in.	24 in.
Minimum depth to impermeable soil layer or rock strata	60 in.	60 in.	60 in.
Depth to 50% by volume rock fragments	24 in.	24 in.	24 in.
Slope	6%	12b	12% b

^a Percolation test depth at 24 in., 12 in., and 24 in., for slowly permeable, shallow soils and high water table soils, respectively, unless there is a more restrictive horizon above. If perched water is at 24 in., test depth should be held to 16 in.

^b For percolation rate of 18-90 minutes max. slope is 12% and for 18-360 minutes, max. slope is 6%.

Ill. Admin. Code tit. 77, pt. 906, app A, exh. A