Illinois Administrative Code
Title 77 - PUBLIC HEALTH
Part 905 - PRIVATE SEWAGE DISPOSAL CODE
Section 905.55 - Subsurface Seepage System Design Requirements
Universal Citation: 77 IL Admin Code ยง 905.55
Current through Register Vol. 48, No. 12, March 22, 2024
After January 1, 2014, when designing a subsurface seepage system, the absorption capacity of the soil shall be determined by subsection (a). After January 1, 2014, subsection (b) shall not be used to determine design requirements for a subsurface system.
a) Soil Investigation
1) Soil investigations shall be conducted in
the following manner:
A) Determination of soil
characteristics on sites proposed for development with private sewage disposal
systems shall be based on soil boring data collected by a soil classifier or an
Illinois licensed Professional Engineer.
B) There shall be a minimum of 3 borings per
soil absorption system site. The soil borings shall be at least 50 feet apart,
and the proposed subsurface seepage system shall be located within the area
where the soil borings were located. More soil borings may be necessary for
accurate and appropriate evaluation of a site where there is some concern about
the consistency of the soil materials. One of the borings shall be made at the
lowest elevation of the proposed absorption field area. Borings shall extend a
minimum of 60 inches below the natural ground surface. An observation pit shall
be used in gravelly materials.
C)
Observation and determination of soil characteristics may also be determined
from a pit dug by a backhoe or other excavating equipment. The Department or
local authority may require soil pits (backhoe excavation) in cases where
ground is frozen, where the soil materials are considerably varied in texture,
where there has been previous or current fill material or cutting of soils, or
where gravelly soils are encountered. Soil pits shall be prepared at the
perimeter of the expected soil absorption area to minimize damage to natural
soil structure. Soil pits shall extend a minimum of 60 inches below the natural
ground surface.
D) Site
characteristics to be described include zones of seasonal and permanent water
saturation, United States Department of Agriculture (USDA) soil textural
changes; USDA soil structural features for each horizon, slope, compaction and
depth; soil coloration; consistence; coatings; depth of limiting layer; depth
of soil mottling; internal drainage classification; permeability range; and
other limiting soil characteristics that may reduce permeability. The following
reference materials shall be used as a guide for describing and classifying
soil: Field Book for Describing and Sampling Soils, Soil Taxonomy, and Soil
Survey Manual.
2) The
following persons are qualified to conduct soil investigations:
A) any person who meets the definition of
soil classifier in Section
905.10;
B) an Illinois licensed Professional
Engineer;
C) an employee of a local
health department who has 3 years of experience in designing or approving
private sewage disposal systems using soil classification information and 6
semester hours of soils-related coursework;
D) an employee of a local health department
with 5 years of experience reviewing the design and approving private sewage
disposal systems using soil classification information under the direct
supervision of those persons listed in subsection (a)(2)(A), (B) or
(C).
3) If conflicting
soils investigation information is provided about a given site, a third Soil
Classifier may be requested to provide additional information or help to
resolve the conflict. A National Resources Conservation Service (NRCS) Soil
Scientist who is also a Soil Classifier may be contacted for technical
information or interpretation.
b) Percolation Tests
1) Performance of Percolation Tests. At least
3 separate percolation tests, a minimum of 50 feet apart, shall be performed at
the site of each proposed subsurface seepage system.
2) Procedure for Performing Percolation
Tests. Percolation tests shall be performed in accordance with the procedure
outlined in Appendix A, Illustration G. Alternate procedures for performing
percolation tests may be submitted to the Department for review. If determined
to be as stringent as that described in Appendix A, Illustration G, the
alternate procedure will be approved.
3) The Department or its agent may choose not
to accept percolation data results and may require a soil investigation if
soils information, permits for private sewage disposal systems in proximity to
the proposed site, direct observation or other information shows conditions
that will have an impact on the design, construction, installation,
modification or performance of the private sewage disposal system.
Disclaimer: These regulations may not be the most recent version. Illinois may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
This site is protected by reCAPTCHA and the Google
Privacy Policy and
Terms of Service apply.