HEALTHY WATER & WASTER WATER 

The Shire of Carnarvon’s Environmental Health Officers works with a vast network of specialists and agencies. Such as the Department of Health, Water Authority, Water Corporation and Gascoyne Water Co-operative Ltd and many others to ensure that the water within the Shire is of a reasonable standard for healthy living and well-being.  Water quality, waste and treatments are inspected and sampled regularly as per Department of Health standards and regulations.

Some of the tasks undertaken by the Environmental Health Officer in relation to healthy water and wastewater are:

  • Assessing wastewater disposals to ensure each property has the required infrastructure required to facilitate the disposal of liquid waste. Waste disposal is legislated and there are strict regulations that need to be complied with.  This includes, but is not limited to the development of an industrial site, building a home, upgrading facilities, ensuring adequate healthy waste disposal is in place to cope with occupants' needs such as in lodging houses, hotels and caravan parks.
  • Sampling, testing and inspecting waterways.  Such as inlets, rivers, dams, creeks and water tanks.
  • Checking and sampling water for mosquito larvae
  • Sampling and testing water for contaminants and disease.
  • Inspections of septics, leach drains and tanks
  • and more

Water Sampling

  • Amoebic Meningitis Precautions
  • Inspections
  • Foreign Objects
  • Sewerage - Septic Tanks and Effluent Disposal
  • Pest Management
  • Mosquitoes
  • Australian Encephalitis
  • Local Laws
  • Environmental Health Approvals
  • Waste Disposal Sites

Onsite wastewater treatment and disposal

Local government assesses proposed systems for the onsite treatment and disposal of wastewater and inspects them prior to use in accordance with the Health Act and Health (Treatment of sewage and disposal of effluent and liquid waste) Regulations 1974 in conjunction with Department of Health guidelines. For systems treating waste for more than a single dwelling, applications are required to be decided by the Department of Health and in most cases, the applications are made to the Local Government who forwards the application on with a Local Government Report.

Most of Carnarvon is sewered whereby sewage from houses and developments goes through underground piping to the wastewater treatment plant operated by the Water Corporation. However, in parts of South Carnarvon, most of East Carnarvon and all other areas further out are unsewered and rely on onsite treatment and disposal of effluent.

Onsite wastewater systems are typical of one of two main types: septic systems and aerobic treatment units (ATUs). Septic systems combined with leach drains is the most commonly used type in Carnarvon and are typically passive without the need for electrical connections while ATUs typically require electrical installations but treat the effluent to a higher standard that allows the effluent to be safely used for surface or sub-surface irrigation. There are various other less commonly used types of systems.

For information on applying to install a wastewater system, including access to the application form, information on approved wastewater system products and calculation of loading rates, please refer to the Department of Health information page: 

Apply to install a wastewater system 

Maintaining your onsite wastewater system

Once you have applied to install a wastewater system, you are required to maintain it, the Shire of Carnarvon Environmental Health Officers have prepared this useful information on how to maintain an on-site sewage treatment and disposal system, septic tank and leach drain system and aerobic treatment unit (ATU) and effluent irrigation systems. 

Maintaining your on-site sewage treatment and disposal system (all domestic types)

In the kitchen: Keep out fats, oils and food scraps as these will increase maintenance costs and potentially reduce the life of the system. Scrape plates before washing. Collect fats and oils into suitable receptacles and dispose of them in the general rubbish once cool. Do not use food waste disposal units/grinders, but put all food scraps in the general rubbish or a mulching bin instead. Don’t use excessive detergent. Only use the dishwasher when it is full to reduce water loading.

In the laundry: Choose front loaders over top loaders as they use less water and detergent. Choose a ‘low’ or ‘no’-phosphorus washing detergent (look for the symbols P or NP). Wait for a full load before starting the washing machine. Spread out your loads over the week to even out the water volume loading.

In the bathroom: Put only human waste and toilet paper into the toilet. Do not dispose of sanitary wipes or napkins into the toilet as they will not break down in the system. This also applies to so-called flush-able wipes, which have been found to be the most common non-soluble object causing problems in septic tanks. Use water-saving showerheads.

Keep out harsh chemicals: Your system relies on the bacteriological breakdown of sewage to function effectively. Avoid releasing large quantities of bleach or other harsh chemicals into the house drains. Domestic mop water can be emptied into the yard away from plants and drains. Do not use drain cleaning chemicals.

Do not interfere with the system: It is an offence for any person to interfere with an on-site sewage treatment or disposal system without prior written approval from the local government.

Do not build structures over the system: It is an offence to build a structure over a system if the structure has 4 walls or obstructs access to the system for maintenance.

Look out for signs of malfunctioning: Call a plumber or the maintenance provider if there are any obvious signs of malfunctioning. Signs include: leach drain area wet and soggy, the smell of effluent near the septic tank or leach drain, drains not working properly, irrigation systems clogged, misdirected or causing ponding.

For further information, contact the Shire office (08 9941 0000) or your local plumber.

Maintaining your septic tank and leach drain system

Annual inspections for septic tanks: Have your septic tank inspected by a professional every year.

Alternate your leach drains: Your leach drains are of the alternating type. A diverter is in place to allow the drainage to be diverted from one leach drain to the other. Know where your diverter is located and ensure the leach drains are alternated every 6-12 months to give the soil time to recover and aerate. The full lifespan of the leach drains will not be achieved without regular alternation of drains. If your property is rented out, ensure this still happens, either by the tenant or by other arrangements. Keep tree roots away from leach drains: Avoid planting trees near leach drains where the roots may interfere, as this is a frequent cause of malfunctioning leach drains.

Do not pave or seal the ground above leach drains: Leach drains require an unsealed ground surface to allow evaporation. Non-compliance is an offence unless special approval is obtained.

Do not drive over leach drains: Leach drains may not be within 1.2m of a trafficable area. This is to prevent compression of the soil which will reduce drainage capacity and may crush the drains.

Seal against mosquitoes: Large numbers of mosquitoes can breed in septic tanks if they can get in. Ensure all openings are tightly capped and air vents sealed with insect-proof mesh. 

Maintaining your aerobic treatment unit (ATU) and effluent irrigation system

Service your aerobic treatment unit at least every 3 months: Your system is an aerobic treatment unit (ATU) with an effluent irrigation system. ATUs treat sewage to a higher standard than septic tanks but require additional maintenance. Owners of ATUs are obliged by law to ensure arrangements are in place at all times for the maintenance of the unit (and irrigation system) by an authorised person. An authorised person is a person authorised by the Department of Health to carry out maintenance work on that type of unit (usually a plumber). Maintenance intervals must be at least every 3 months. Owners may not undertake maintenance work on their aerobic treatment unit and may not arrange for non-authorised persons to undertake maintenance work on the same.

Refer to the operation manual which should be provided with your ATU system for detailed information from the manufacturer and installer about your specific system.

Helpful advice for designing Carnarvon residential systems