Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 570 - DESIGN AND MAINTENANCE CRITERIA REGARDING RUNOFF FIELD APPLICATION SYSTEMS › Subpart B - DESIGN CRITERIA › Appendix C - Procedure to Estimate Soil Infiltration Rate

Current through Register Vol. 48, No. 28, July 12, 2024
Procedure to Estimate Soil Infiltration
				  Rate
Soil infiltration rate for a runoff field application area
				  can be determined by using:
1. Any of three methods given in EPA Process
				  Design Manual - Land Treatment of Municipal Wastewater dated October, 1981;
				  Chapter 3.4 - Infiltration Rate Measurements.
2. The following modified cylinder infiltrometer
				  method:
Procedure
A. Preparing the test site
Drive a rigid, leak-proof container approximately
				  6 inches into the ground taking car to avoid disturbing the soil as much as
				  possible. This container should be approximately 2 feet long by at least 10
				  inches wide, and may be of any suitable material. A metal pipe is recommended
				  (see Figure 1).
B. Saturation and Swelling of the Soil
Before conducting the test, saturate the soil for
				  at least four hours, but preferably 8 hours, by refilling the container with
				  clean water as needed.
C. Testing
At the time of the test, adjust the water level to
				  12 inches above the soil surface. Allow the water level to drop six inches and
				  then commence measuring the drop in water level at 15 minute intervals until
				  the water has infiltrated. Repeat part C.
D. Recording Results
Record results of all tests as the total minutes
				  required for the last six inches of water to infiltrate (minutes/inch). Average
				  the two tests at each site. For example:
Site 1 - Data Recorded
min
inch
min
inch
0
6.0
45
2.5
15
4.5
60
2.0
30
3.5
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E. Soil Infiltration Rate
The soil infiltration rate (SI) is calculated at
				  each site:
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Example
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F. Average the soil infiltration rates from each
				  testing site to calculate the SI value for the runoff field application area.
These tests must not be made on frozen ground and
				  include a safety factor in Part E to compensate for inherent inaccuracies in
				  this procedure.
3. Data from a modern U.S.D.A. - S.C.S. soil
				  survey for the county where the runoff field application system will be
				  installed. Use the Table of Engineering Properties - Physical and Chemical
				  Properties for Permeability of the surface soil layer as follows:
1. Locate the soil name and map symbol for the
				  field application area on the map sheets (example - 386A, Downs).
2. On the Physical and Chemical Properties Table
				  locate the surface layer permeability rate.
Example
Table 15 - Physical and Chemical Properties of
							 Soils
Soil and map symbol
Depth (inches)
Permeability (in/hr)
386A, 386B
0 - 7
0.6 - 2.0
Downs
7 - 30
0.6 - 2.0
30 - 60
0.6 - 2.0
3. At the surface layer (0 - 7 inches for the
				  example) use the average value of the permeability range to obtain SI.
Example
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Figure 1:
Cylinder
				  Infiltrometer
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				  image