Statutes, codes, and regulations
Illinois Administrative Code
Title 77 - PUBLIC HEALTHPart 905 - PRIVATE SEWAGE DISPOSAL CODEAppendix A - Illustrations and Exhibits
Subsurface Seepage System Size Determination
Exhibit A - Gravel System

Ill. Admin. Code tit. 77, pt. 905, app A, ILLUSTRATION H, exh. A

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Current through Register Vol. 48, No. 45, November 8, 2024
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:

1.

Absorption area is figured as trench bottom area in absorption trenches and bottom area in seepage beds.

2.

Seepage beds require 11/2 times the seepage field absorption area specified.

3.

Over 360 is unsuitable for subsurface seepage systems.

4.

Under 18 is unsuitable for subsurface seepage systems.

5.

Divide the required total gallons per day by this number to get the number of square feet required

Ill. Admin. Code tit. 77, pt. 905, app A, ILLUSTRATION H, exh. A

Amended at 20 Ill. Reg. 2431, effective March 15, 1996