Western Australian Current Regulations

HEALTH (TREATMENT OF SEWAGE AND DISPOSAL OF EFFLUENT AND LIQUID WASTE) REGULATIONS 1974 - SCHEDULE 8

[Reg. 49(3)]

        [Heading inserted: Gazette 15 Dec 1989 p. 4552.]

Method of determining absorptive capacity of a soil

        [Heading inserted: Gazette 15 Dec 1989 p. 4552.]

1.                 Dig a hole with dimensions of 300 mm square and vertical sides to the depth of the proposed absorption trench.

2.                 Carefully scarify the bottom and sides of the hole in order to remove any smeared soil surfaces and to provide a natural soil interface into which the water may percolate. Remove all loose material from the hole. Add 50 mm of blue metal, or screened gravel, to protect the bottom from scouring and sediment.

3.                 Fill the hole with water and allow it to soak away. Preferably keep the hole filled overnight, possibly by means of an automatic siphon.

4.                 The following morning, fill or adjust water level to a depth of 150 mm above blue metal or gravel, insert measuring stick (as shown in the diagram at the end of this Schedule) and note time taken for water to fall 25 mm.

                The amount of effluent which can be disposed of per square metre of infiltrative area per day is given by the following Table —

Table

Time for water to fall 25 m (minutes)	Soil type	Loading infiltration rate litres per m 2 per day
		Alternating system	Non‑alternating system
1 to 5 more than 5 to 60 more than 60	Sand Loams or gravels Impervious clays, etc	30 20	15 10
		As approved by the Chief Health Officer (see clause 5)

5.                 This soil type in its natural state is unsuitable for on site disposal, however the Chief Health Officer may approve of a loading infiltration rate in a particular case if satisfied that system design and site modification to justify the loading rate will be carried out.

Diagram

        [Schedule 8 amended: Gazette 29 Jun 1984 p. 1781; 15 Dec 1989 p. 4552‑3; 10 Jan 2017 p. 287‑8.]