Septic and on-site sewage around Richmond

Two approvals, then inspections

The NSW Office of Local Government puts the rule simply: as the owner, you are responsible for making sure the system is approved by your council and working properly. In Hawkesbury City Council’s area the steps run in this order.

1. Approval to installThe application is made under section 68 of the Local Government Act 1993, on the council’s form (May 2019). The form asks for plans to scale showing the house, the proposed effluent disposal area, any bore holes, the contours of the land, and any buildings or environmentally sensitive areas within 100 metres of the system or its disposal areas. It also asks for the system’s specifications, a site assessment of the topography, soil and vegetation, and sizing calculations for the disposal area.
2. Inspection before backfillingThe council inspects external drainage once the pipework is in and the septic tank is installed, before backfilling. The plumber should book it at least 48 hours ahead.
3. Approval to operateAfter a satisfactory inspection, the council issues the owner an approval to operate. It sets out the renewal date and the conditions for operating and maintaining the system safely.
4. Inspections on a scheduleEvery system must be registered with the council. Once passed, each is categorised as low, moderate or high risk, based on the type of system, its age and the health and environmental risks of the site. Councils can charge fees for these inspections.

The council’s form (May 2019) names the standards an installation has to meet, among them the Australian Standard for on-site domestic wastewater management, AS/NZS 1547:2012, and the effluent disposal section of the Hawkesbury Development Control Plan. Changing an existing system goes through the same form, which has a box for an amendment.

Why the council inspects

Hawkesbury City Council says improperly managed sewage on private properties has led to dangerous levels of water and food contamination and to outbreaks of disease. It cites a NSW Government survey that found up to 70% of on-site systems were experiencing some type of failure, and estimates there are over 9,000 systems in its area. Its program for finding inefficient systems and helping keep them working well is called Septic Safe.

Getting ready for an inspection

The council asks owners to have three things in place when its officer arrives:

• Safe access to the tank or tanks and to the effluent disposal area.
• The grass mown around the tanks and the disposal area.
• Dogs, other animals and stock secured or locked up.

How a septic system works, and how it fails

The Easy Septic Guide, first published in 2000 by the NSW Department of Local Government and linked today from the Office of Local Government’s page, explains the basic design. The tank holds back the solid scum and sludge and lets liquid effluent flow out to the trenches; the solids stay behind and build up.

1. 1The pipe from the house.
2. 2The septic tank: scum floats at the top, sludge settles at the bottom, and both stay in the tank.
3. 3Liquid effluent leaves the tank for the trench.
4. 4The absorption trench, where the effluent soaks into the soil.

The guide’s main points for a tank with absorption trenches:

• Have the tank pumped out every 3 to 5 years. Without it the solids build up, flow into the trench and clog it. The guide calls a missed pump-out the most common cause of problems.
• Go easy on chemicals. Solvents, paints, disinfectants, bleaches and cleaning products can kill the bacteria the tank relies on.
• Additives are no cure. The guide says no additive will help a septic system that needs pumping out or whose trench is failing.
• Keep the trench clear. No cars or grazing animals on it, no buildings, concrete or pavers over it, and no sprinklers flooding it. Small trees at least 5 metres away and large trees over 20 metres away, or their roots can harm the trench.

If a system is failing

The council says an officer will work with you so you understand why the system is failing and how to fix it. If the problem is not put right, the council may issue an order under the Local Government Act 1993 or act in other ways.

A system also matters to anyone drawing water from the ground nearby. NSW Health says a groundwater source should be uphill from, and at least 250 metres away from, any wastewater disposal system such as a septic tank and trenches. More in bores and groundwater.