25.1.Construction standards: A gravity feed soil absorption field built under a non-watertight secondary treatment system must comply with subparagraphs c and h.1 of the first paragraph of section 21 and with the following requirements:
(a) the secondary treatment system must be able to cover and uniformly distribute water over the entire seepage surface of the soil absorption field;
(b) the maximum length of an absorption trench installed under a non-watertight secondary treatment system must comply with the maximum length of the secondary treatment distribution system. The maximum length must be provided in the manufacturer’s manuals and have been certified by an engineer who is a member of the Ordre des ingénieurs du Québec;
(c) if the width of the treatment system units is greater or lesser than 60 cm without exceeding 1.2 m, the total length of the absorption trenches required by section 22 must be rectified according to the width of the secondary treatment system so as to cover the same absorption area, considering that the length is valid for a trench 60 cm wide. If the absorption trenches are wider than the units of the secondary treatment system, a minimum 15 cm layer of gravel or crushed stone complying with subparagraph f of the first paragraph of section 21 must be spread over the entire absorption trench; and
(d) the bottom of the treatment system or the layer of crushed stone must be at least 60 cm above bedrock, impermeable or low permeability soil or underground water.