Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.03 - INDIVIDUAL/SUBSURFACE SEWAGE DISPOSAL RULES AND RULES FOR CLEANING OF SEPTIC TANKS
Section 58.01.03.013 - LARGE SOIL ABSORPTION SYSTEM DESIGN AND CONSTRUCTION
Current through August 31, 2023
01. Site Investigation. A site investigation for a large soil absorption system by a soil scientist and/or hydrogeologist may be required by the Director for review and approval and shall be coordinated with the Director. Soil and site investigations shall conclude that the effluent will not adversely impact or harm the waters of the State. (3-31-22)
02. Installation Permit Plans. Installation permit application plans, as outlined in Subsection 005.04, for a large soil absorption system submitted for approval shall include provisions for inspections of the work during construction by the design engineer or his designee and/or by the Director. (3-31-22)
03. Module Size. The maximum size of any subsurface sewage disposal module shall be ten thousand (10,000) gallons per day. Developments with greater than ten thousand (10,000) gallons per day flow shall divide the system into absorption modules designed for ten thousand (10,000) gallons per day or less. (3-31-22)
04. Standard Large Soil Absorption System Design Specifications. (3-31-22)
TABLE -- EFFECTIVE SOIL DEPTHS |
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Site Conditions |
Design |
Soil |
Group |
Limiting Layer |
A |
B |
C |
Impermeable Layer |
8 |
8 |
8 |
Fractured Bedrock, Fissured Bedrock or Extremely Permeable Material |
12 |
8 |
6 |
Normal High Groundwater Level |
12 |
8 |
6 |
Seasonal High Groundwater Level |
2 |
2 |
2 |
(3-31-22)
TABLE -- SEPARATION DISTANCES |
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Feature of Interest |
Design |
Soil |
Group |
A |
B |
C |
|
All Domestic Water Supplies |
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Sewage Volume - 2,500-5,000 GPD |
250 |
200 |
150 |
Sewage Volume - 5,000-10,000 GPD |
300 |
250 |
200 |
Property Lines |
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Sewage Volume - 2,500-5,000 GPD |
50 |
50 |
50 |
Sewage Volume - 5,000-10,000 GPD |
75 |
75 |
75 |
Building Foundations - Basements |
|||
Sewage Volume - 2,500-5,000 GPD |
50 |
50 |
50 |
Sewage Volume - 5,000-10,000 GPD |
75 |
75 |
75 |
Downslope Cut or Scarp |
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Impermeable Layer - Below Base |
100 |
50 |
50 |
Separation Distance - Between Modules |
12 |
12 |
12 |
(3-31-22)
05. Large Septic Tanks. Large Septic Tanks shall be constructed according to Section 007, except as outlined in this Subsection: (3-31-22)
06. Monitoring and Reporting. Before an installation permit is issued, a monitoring and reporting plan shall be approved by the Director and shall contain the following minimum criteria: (3-31-22)
07. Operation and Maintenance. Before an installation permit is issued, an operation and maintenance plan shall be approved by the Director and shall contain the following minimum criteria: (3-31-22)