17. Installation conditions: Where the effluent of a treatment system is carried towards a soil absorption field, the disposal system must be connected to a soil absorption field where all the following conditions are met:
(a) the soil must be a high permeability or permeable soil;
(b) the bedrock, underground water or any layer of impermeable soil or low permeability soil must be at least 1.2 m below the surface of the disposal site if the effluent is from a primary treatment system and at least 90 cm below the surface of the disposal site if the effluent is from a secondary treatment system;
(c) the grade of the disposal site must be less than 30%.