Section 905

Section 905.APPENDIX A Illustrations and Exhibits

Section 905.ILLUSTRATION I Seepage Field Construction

Section 905.EXHIBIT A Gravel System

Trench length, maximum length from point of discharge into seepage trench	100 feet
Trench bottom, minimum width	8 in.
Trench bottom, maximum width	36 in.
Trench bottom, minimum depth	18 in.
Trench bottom, maximum depth	36 in.
Trench bottom, slope	level
Distribution line, minimum diameter	4 in.
Distribution line, minimum earth cover	6 in.
Distribution line, maximum earth cover	24 in.
Distribution line, maximum slope	level

(Source: Amended at 20 Ill. Reg. 2431, effective March 15, 1996)

Section 905.APPENDIX A Illustrations and Exhibits

Section 905.ILLUSTRATION I Seepage Field Construction

Section 905.EXHIBIT B Size and Spacing Gravel System

Width of Trench at Bottom	Minimum Center to Center Spacing of Distribution Lines	Effective Absorption Area Per Lineal Foot of Trench
Inches	Feet	Square Feet
8	6.0	0.67
12	6.0	1.0
18	6.0	1.5
24	6.0	2.0
30	7.5	2.5
36	9.0	3.0

(Source: Amended at 9 Ill. Reg. 20738, effective January 3, 1986)

Section 905.APPENDIX A Illustrations and Exhibits

Section 905.ILLUSTRATION I Seepage Field Construction

Section 905.EXHIBIT C Gravelless System

STANDARDS FOR SEEPAGE FIELD CONSTRUCTION (GRAVELLESS)
Trench Length, maximum length from point of discharge into system	100 feet
Trench Bottom, minimum width	18 inches
Trench Bottom, maximum width	24 inches
Trench Bottom, minimum depth	18 inches
Trench Bottom, maximum depth	36 inches
Trench Bottom, slope	level
Distribution Line, minimum inside diameter	8 inches
Distribution Line, maximum inside diameter	10 inches
Distribution Line, minimum earth cover	6 inches
Distribution Line, maximum earth cover	24 inches
Distribution Line, maximum slope	level

(Source: Amended at 20 Ill. Reg. 2431, effective March 15, 1996)

Section 905.APPENDIX A Illustrations and Exhibits

Section 905.ILLUSTRATION I Seepage Field Construction

Section 905.EXHIBIT D Spacing − Gravelless and Chamber Systems

SPACING FOR SEEPAGE FIELD CONSTRUCTION

(GRAVELLESS AND CHAMBER SYSTEMS)

Gravelless and Chamber Dimensions	Minimum Center to Center Spacing of Distribution Lines
8 Inch Inside Diameter of Gravelless Pipe System	7.0 feet
10 Inch Inside Diameter of Gravelless Pipe System	7.0 feet
12 Inch Wide Chamber System	7.0 feet
18 Inch Wide or Wider Chamber System	9.0 feet

(Source: Amended at 37 Ill. Reg. 14994, effective August 28, 2013)

Section 905.APPENDIX A Illustrations and Exhibits

Section 905.ILLUSTRATION I Seepage Field Construction

Section 905.EXHIBIT E Chamber Sizing Requirements

Example: Chamber systems shall be sized on the absorption area of the chamber that is equivalent to the bottom area of a gravel system. The equivalent chamber absorption area per lineal foot is equal to the average inside width of the chamber times an equivalency factor of 2.5. For example, a chamber that has an average inside width of 1.25 feet provides an equivalent absorption area of 3.125 square feet per lineal foot. (1.25 feet times the 2.5 equivalency factor equals 3.125 square feet per lineal foot.

To determine the length of chambers required, first calculate the absorption area required for a gravel system based on Appendix A, Illustration H, Exhibit A or Appendix A, Illustration M, Exhibit A. Then divide this area by the equivalent chamber absorption area per lineal foot. For example, if a 3 bedroom house requires 870 square feet of absorption field and chambers 1.25 feet wide are being used, then the length of chambers needed is 278 feet. (870 square feet divided by 3.125 square feet per lineal foot equals 278 feet.)

Chamber systems with an average inside dimension equal to or greater than 20 inches shall not be designed to receive an equivalent absorption area of greater than 54 square feet per lineal foot.

(Source: Amended at 37 Ill. Reg. 14994, effective August 28, 2013)