Q-2, r. 22 - Regulation respecting waste water disposal systems for isolated dwellings

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87.25.4. Construction standards: A leaching field installed in the conditions described in section 87.25.2 must be built with a low pressure feed system,
(a)  applying a maximum hydraulic loading rate to the soil at the disposal site that does not exceed the rates in the following table based on the hydraulic conductivity or percolation time and the soil characteristics at the disposal site:
Hydraulic conductivity (cm/s)Percolation time (min/cm)Maximum hydraulic loading rate L/(m2.d)
4X10-3 to 4 X10-44 to 1533
4X10-4 to 2 X10-415 to 2524
2X10-4 to 6 X10-525 to 4512
Soil characteristics at disposal siteMaximum hydraulic loading rate L/(m2.d)
Textural classStructure
 TypeGrade
Silt loamPrismatic, blocky or granularModerate or strong33
Weak24
Silt, clay loam or silty clay loamPrismatic, blocky or granularModerate or strong24
Weak12
Sandy clay, silty clay or clayPrismatic, blocky or granularModerate or strong12
(b)  applying a maximum linear hydraulic loading rate to the soil at the disposal site that does not exceed the rate in the following table based on the soil characteristics and grade at the disposal site as well as the thickness of the soil at the disposal site above the level of bedrock, underground water or any layer of impermeable soil available under the leaching field’s seepage surface:
Soil characteristics at disposal siteLinear hydraulic loading rate L/(m.d)
Textural classStructureGrade at disposal site
TypeGrade< 5 %≥ 5 %
< 10 %
≥ 10 %
< 30 %
 Thickness of disposal site (cm)Thickness of disposal site (cm)Thickness of disposal site (cm)
 30-6060-12030-6060-12030-6060-120
Silt loamPrismatic, blocky or granularModerate or strong374143504753
Weak343737414350
Silt, clay loam or silty clay loamPrismatic, blocky or granularModerate or strong364237414350
Weak313734403642
Sandy clay, silty clay or clayPrismatic, blocky or granularModerate or strong313734403642
If the leaching field consists of trenches, it must meet the standards in subparagraphs b, c, d, e, f, g, g.1 and g.2 and subparagraph i of subparagraph i of the first paragraph of section 21 and in subparagraphs a and b of the second paragraph of that section, those in sections 23 to 25 and those in the third paragraph of section 87.22, with the necessary modifications.
If the leaching field consists of a seepage bed, it must meet the standards in subparagraphs d, e, f, g, g.1 and g.2 of the first paragraph of section 21 and in subparagraphs a and b of the second paragraph of that section, those in sections 24 and 25, those in subparagraphs a and c and in subparagraph i of subparagraph b of the first paragraph of section 27 and those in the fourth paragraph of section 87.24, with the necessary modifications.
1156-2020O.C. 1156-2020, s. 67.