University of Illinois Extension

Quiz

Practice Problems: Sizing Residential Subsurface Seepage Systems 1

Sizing of subsurface seepage systems is done by applying the soil loading rate to the average daily flow, or the number of bedrooms for residential settings.

The soil loading rate can be calculated by using either a percolation (perc) test or a soil evaluation.  The procedure for conducting percolation tests is found in section 905, Appendix A, Illustration G of the administrative code.

Information on using soil evaluations and loading rates is found in Section 905, Appendix A, Illustration M

Information on calculations for gravel trenches is found in Appendix A, Illustration H, Exhibit A.  Exhibit B is used for gravelless pipe.

Residential Practice problems.

A perc test average is 240 minutes.  The residential 4 bedroom house is being built.

  1. Practice Problems: Sizing Residential Subsurface Seepage Systems 1
    Determine the number of square feet of gravel trench required: 1280 sq. ft.
    • 320 square feet/bedroom 320 x 4 = 1280 total square feet required
  2. Practice Problems: Sizing Residential Subsurface Seepage Systems 1
    Determine the linear feet of 24 inch gravel trench required: 640 linear feet
    • 1280/2 = 640 linear feet required
  3. Practice Problems: Sizing Residential Subsurface Seepage Systems 1
    Determine the linear feet of 22 inch chamber required: 320 linear feet
    • 1280/4 = 320 linear feet required
  4. Practice Problems: Sizing Residential Subsurface Seepage Systems 1
    Determine the linear feet of 10 inch gravelless pipe required: 440 feet
    • 110 feet per bedroom = 110 × 4 = 440 ten inch pipe required