University of Illinois Extension

Quiz

Practice Problems: Sizing Residential Subsurface Seepage Systems 2

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 4 bedroom residential house has a soil evaluation of Group 5D for 0 to 30 inches, 6D for 30 to 48 inches, and Group 5L for 48 to over 60 inches.

  1. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What is the loading rate for Soil Group 5D?

    265 square feet/bedroom
  2. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What is the loading rate for Soil Group 6D?

    325 square feet/bedroom
  3. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What is the loading rate for Soil Group 5L?

    385 square feet/bedroom
  4. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What is the number of square feet of gravel trench required?

    1540 square feet
    • 385 × 4 bedrooms
  5. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What is the linear feet of gravel trench required, using a 2 foot bucket for excavation?

    770 feet
    • 1540/2
  6. Practice Problems: Sizing Residential Subsurface Seepage Systems 2

    What are the linear feet of chamber required for a 22 inch chamber?

    385 feet
    • 1540/4