University of Illinois Extension

Quiz

Practice Problems: Sizing Commercial Subsurface Seepage Systems 3

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.

Commercial practice problems.

Size a private sewage disposal system for a Sanitary Dump Station for a campground with 30 unsewered sites:
  1. Practice Problems: Sizing Commercial Subsurface Seepage Systems 3

    What is the estimated average daily flow?

    600 gallons
  2. Practice Problems: Sizing Commercial Subsurface Seepage Systems 3

    What is the minimum sized septic tank required?

    900 gallons
    • 600 X 1.5 = 900 gallons
  3. Practice Problems: Sizing Commercial Subsurface Seepage Systems 3

    How many feet of 22 inch chamber needed if the perc rate is 240 minutes?

    242 feet
    • 600/.62 = 968 ft² /4 = 242 feet
  4. Practice Problems: Sizing Commercial Subsurface Seepage Systems 3

    How many linear feet of 36 inch wide gravel trench would be required?

    323 feet
    • 968/3 = 323 feet