(b) to serve an existing isolated dwelling, where all the following conditions are met:
i. a soil absorption system, a standard sand-filter bed, a privy or a biological system that complies with any of Divisions VI to XI and XIII or a system that complies with any of Divisions XV.2 to XV.5 cannot be built;
ii. the isolated dwelling served is not supplied by pressurized water pipes;
iii. the haulage of a holding tank cannot be carried out because it is not accessible;
iv. the bedrock, underground water or any layer of impermeable soil or low permeability soil is between 60 and 120 cm below the surface of the natural ground.