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ITEM 28    Yeoval Sewage Management................................................. 2

Confidential Items


Clause 240(4) of the Local Government (General) Regulation 2005 requires Council to refer any business to be considered when the meeting is closed to the public in the Ordinary Business Paper prepared for the same meeting.  Council will discuss the following items under the terms of the Local Government Act 1993 Section 10A(2), as follows:



(d) (ii) commercial information of a confidential nature that would, if disclosed, confer a commercial advantage on a competitor of the council


(d) (i) commercial information of a confidential nature that would, if disclosed prejudice the commercial position of the person who supplied it   






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ITEM 28 - Yeoval Sewage Management



Reason For Report

Provide Council with information on Yeoval sewage management and option.

Policy Implications


Budget Implications

Dependent on Council decision.



File Number






THAT Council:


1.   Note the report on the Yeoval sewage management; and


2.   Provide the information contained in the report to the Yeoval Progress Association and other interested individuals or groups.


Director of Engineering and Technical Services' REPORT


The Yeoval community meeting held in Yeoval on March 28 resulted in a number of actions for council to undertake.

One action was to consider the options if the reticulated sewerage system proposed for Yeoval did not proceed. The following provides this scenario.



The western urban area of Yeoval has allotments in a rectangular layout with areas ranging between 1800-2000 sqm. The Residential blocks to the eastern area of the main street are typically 800-1000sqm. Topography varies between gently sloping to low flat lying land. The soil type is typically sandy loam to clay. Rocky outcrops are prominent in some areas.

Allotment size, topography and soil type are factors for consideration in the management of household waste water.

Typically the existing onsite systems in Yeoval are septic systems comprising of septic tank and absorption trench.  Due to the decision by the Yeoval community to proceed with sewage, Council has not undertaken regular inspections of the septic systems from the time the Four Towns Sewerage Reticulation Scheme was initiated. The condition and serviceability of these systems is therefore uncertain.

Should reticulated sewerage not be provided, these properties would have to have complying on site sewerage systems.



As mentioned previously the systems generally in place are septic tank with absorption trench. Existing systems that are functional would not require an up grade. However if found to be non-compliant/non-functional, i.e. the absorption trench is not working as it should, than an up-grade that meets current EPA, NSW Health and Council regulations would be  required.

Typically, septic system consists of the septic tank combined with a sewer absorption system. All of the waste water from the house hold enters the tank most of the solids settle at the bottom and are retained in the tank forming a sludge layer whilst fats and grease collect at the top in a scum layer. Bacteria in the septic tank break down the solid matter in the sludge and scum layer. Material that cannot be broken down gradually in the tank, must be pumped out periodically. From the septic tank the transformation of absorption trenches take the effluent away and are absorbed in to the soil.

Such application systems have the potential to contaminate ground water and are not recommended in sensitive locations or high density developments. In other cases the effluent treatment requires a pump out as the property does not allow for a suitable absorption trench, pump outs would be required regularly.

When septic systems become old and absorption trench become clogged there are a number of warning systems. Warning systems that signal troubles with septic tank include:


1.   Water that drains too slowly;

2.   Drainpipes that gurgle or make noises when air bubbles are forced back to the system;

3.   Sewerage smells, this indicates a serious problem;

4.   Water backing up into your sink which may indicate your system is already failing;

5.   Water surfacing over the land application area.

Odour problems from vents can be a result of slow or inadequate breakdown of solids, this again requires servicing by a technician. Poorly maintained septic tanks are serious source of water pollution and present a health risk, and attract vermin and insects.

There is reports of effluent discharge/transportation into laneways and streets which is a sign of the absorbent trenches being non functional.


There are a number of residences and businesses in Yeoval where existing septic tank and absorbent trenches would not be suitable, the land area, soil type or drainage would not be suitable for absorption trenches.

The continued use of on property septic systems to manage household effluent, would require many of these systems to be either completely overhauled or replaced by an Enviro system or similar.



There has been growing evidence that shows an increasing number of on-site sewage management systems (OSMS) fail to meet environmental and public health requirements. It has become practice to adopt four principles which are:


1.   Ecologically Sustainable Development (ESD)

The principles of the ESD had been adopted into the Protection of the Environment Administration Act 1991 (Section (6) (2), (a)-(d)). It emphasises the conservation (health, productivity and diversity) of the environment (Biological and Ecological) for the benefit of future generations. An important statement it makes is based on the precautionary principle whereby the lack of scientific evidence should not be used as a reason for postponing measures that would prevent environment degradation of a serious and irreversible nature.

2.   Total Catchment Management (TCM)

Catchment management protects water resources from dangerous pathogens which may enter into our water supply and increases the risk of transmittance if there is inadequate treatment processes in place.

3.   Total Water Cycle Management (TWCM)

TWCM is also known as the Integrated Water Cycle Management as an approach to manage our water resources. It is broken up into Natural (rainfall, river, groundwater etc) and Managed (water supply, treatment and release of sewage and stormwater) components. Failed OSMS will impact the TWCM by introducing pathogens and nutrients into the Natural and Managed components. It is also important to note that the pathogen infiltration from OSMS may have a large impact on public health as the viruses will most certainly be transmittable to other humans (unlike pathogens from stock).

4.   Protection of Public Health

Studies had shown that the provision of adequate and safe public water supply through TCM, water treatment, disinfection and distribution to house hold as well as the removal of human waste products using reticulation and transfer system for sanitary management have lead to a decrease in mortality and morbidity rates which have led to an increase in life expectancy in the least century.

A recent study conducted by Deere and Billington (On-Site Watewater Management: Mount Lofty Ranges, South Australia, 2012) showed that upgrading of failed septic systems in a Mt Lofty Ranges, SA (~30% failure rate) over a period of 10 years reduced the risk of viruses in natural waters by 4 fold, which shows the impact failed OSMS can have on the environment and public health.

These four principles were used to establish the NSW guidelines for long-term on-site sewage management for domestic wastewater and sewage. The guideline had been adopted by Council and is used in the maintenance and monitoring of OSMSs. The Local Government Act 1993 and the Environmental Planning and Assessment Act 1979 provide Council with the legislative frame work needed to implement management strategies for OSMS.


The design, installation and operation of domestic on-site sewage management systems are regulated under the Local Government Legislation.  Under the Local Government Act (S 68), council approval is required for the installation, construction or alteration of a human waste treatment device.

Local Government Act 1993 S124 gives the council the power to issue the following orders:


1)   Comply with approval

2)   Take action to maintain a premises in a healthy condition

3)   To store, treat or dispose of waste

4)   Not to use or permit a human waste storage facility to be used

5)   To connect premises to a public sewer when the sewer is within 75m.

Orders can be issued to the owner or occupier or person responsible for the waste or the container in which the waste is stored. Failure to comply with such an order is an offence of up to 20 penalty units.  As part of the On-site Septic Management Strategy, each OSMS installed at any house hold must comply with the following performance targets:


1)   Prevention of public Health risk.

2)   Protection of lands.

3)   Protection of surface waters.

4)   Protection of ground waters.

5)   Conservation and reuse of resources.

6)   Protection of Community amenity.

7)   OSMS should be operated and maintained in a way that does not affect the quality of life.

The Local Government (Approvals) Regulation 1993 had set out specific requirements for onsite sewage management approvals. The site assessment would include the following:


1)    Effluent studies.

2)    Soil testing.

3)    Site geography and geology.

4)    Flood potential.

5)    Site drainage.

6)    Erosion potential.

7)    Identifying Buffer distances.

NSW Health is responsible for the accreditation of human waste treatment devices or human waste storage facilities that are intended to receive domestic waste water or human waste.  A certificate of accreditation might include specific requirements for the installation, operation and maintenance of the tested system.


Pollution of water is an offence under the Clean Water Act 1970 where on the spot fines can be issued. Environmental Offences and Penalties Act 1989 can be used to prosecute pollutants. The maximum penalty for water pollution is $120,000 for individuals and $250,000 for corporations. This includes the pollution of stormwater, rivers, creeks, groundwater under NSW law.




Site assessments are required by Council to determine if OSMS are suitable for the site. This would involve a soil assessment and be assessed based on its impact to the ESD, TCM, TWCM and protection of public health.

The Council has OSMS management strategy in place which is used to assess sites for OSMS. These locations are identified as either “High Risk” or “Medium Risk.” The site assessment is at the cost of the applicant. The site assessment is assessed by Council to determine the suitability of the type of OSMS based on a risk assessment. This process would also apply to existing systems whereby the original OSMS has been deemed by Council to have failed due to non-compliance with environmental and health standards.


Table 1 Site Assessment

High Risk

Medium Risk

·    Within unsewered village zones

·    Land area less than 2 hectares

·    Less than 200 metres from a watercourse, lake or water body (water course includes any defined drainage line)

·    Flood prone land

·    Defined water catchment protection area


·    Rural residential (between 2-10 hectares)

·    Aerated waste water treatment system used

·    Any premises with a reticulated water supply not in a high risk category

·    Less than 400m from a water course


In general, the households within the Yeoval Village Zone would be considered as High Risk.



It is important to ensure that the lot sizes are adequate and meet the requirements for OSMS. The Environmental Protection Agency (EPA) has developed a model to estimate the land requirements for effluent irrigation based on soils, water and public health. (NSW Environmental Protection Authority 1995). The model indicates that the OSMS generally require a minimum land area of between 4000 m2 to 5000 m2 total area per house hold to reduce impacts in the medium to long term.



Absorption trenches are used to distribute waste water into the soil. The length of the trench is dependent on the amount of waste water generated in a home. The AS/NZS 1547 4.2D have a model that is used to determine the length of each trench should not exceed 20m. Each trench was assumed to be 0.6m x 0.6m (width x height). The following table shows the required total length of trench for different sized households under the current guidelines. It is common practice for allowances to be made to account for rainfall and evaporation-transpiration rates. This was not included in the data shown in the following table and it is expected that the minimum absorption area required would be larger than the areas shown in the following table. 


Table 2 Absorption Trench Lengths


1 Bedroom

2 Bedroom

3 Bedroom

4 Bedroom

Absorption Area





Length of trench





Number of 20m rows








Buffer zones are required to prevent pollution of sensitive environments on and off site, ensure protection of community health, environment and community amenity. Buffer distances must be maintained between OSMS and premises boundaries, driveways, buildings, swimming pools, groundwater, bores drainage and water courses.


The following are Buffer Distances recommended in the OSMS Guidelines and are adopted by Council in the OSMS Strategy.


Table 3 Minimum Buffer Distances


Buffer Distances

Land Application Systems

·    10 m from permanent surface water (eg. River, streams and lakes)

·    250m from domestic ground water well (bore)

·    40m to other waters (eg. Farms, dams, intermittent waterways and drainage channels)

Surface Spray Irrigation

·    6 metres if area up-gradient and 3 metres if area down-gradient of driveways and

·    property boundaries

·    15 metres to dwellings

·    3 metres to paths and walkways

·    6 metres to swimming pools

Surface Drip and Trickle Irrigation

·    6 metres if area up-gradient and 3 metres if area down-gradient of swimming pools, property boundaries, driveways and buildings

Subsurface Irrigation

·    6 metres if area up-gradient and 3 metres if area down-gradient of swimming pools, property boundaries, driveways and buildings

Absorption Systems

·    12 metres if area up-gradient and 6 metres if area down-gradient of property boundary

·    6 metres if area up-gradient and 3 metres if area down-gradient of swimming pools, driveways and buildings




The following table shows the list of issues that have to be considered when operating an OSMS in the Yeoval Village zone.


Table 4


Key Issue



Age of OSMS

1.   Absorption trenches typically have a limited life. The rate of biological growth that forms around the trench is known to be a major factor in reducing soil permeability. The reduction in soil permeability would lead to accumulation of effluent and therefore overload the trench reducing the rate of biological processes. Poor soil permeability can also lead to effluent remaining close to the surface and even lead to effluent resurfacing which would increase the environmental impact and risk to public health. Effluent resurfacing would also mean that the soil processes where the pathogens and nutrients are broken down would not occur before entering the wider environment.

2.   The OSMSs located on majority of the households had not been maintained or monitored by Council for ~ 10 years. Furthermore, it is likely that the OSMSs located in Yeoval have been in operation for greater than 20 to 25 years. NSW Division of Local Government state that recent studies show that ~ 70% of OSMS fail to meet community expectations for public health and environmental standards.


Ground/Soil Saturation

1.   Yeoval is a town that experiences high rainfall. Rainfall at Yeoval is measured on a weekly basis by Council. The total rainfall from July 2011 to May 2012 (44 weeks) was 769.7mm. The rainfall data indicates that ~20% of the rainfall exceeded 30mm in any week and there was >0 mm rainfall on 68% of the 44 weeks. Low rainfall and high evaporation transpiration rates are desired for OSMS systems making use of absorption trenches

2.   High rain fall would also result in the soil getting saturated with water which could potentially reduce the water permeability.


Land Size

1.   The typical land size in Yeoval is between 800m2 to 1000m2. Based on the length of absorption trenches required of the typical 3 bedroom home and compliance with buffer distances, it would be difficult or impossible to have absorption trench type OSMS installed without having an impact on amenity and health and safety of the public or the occupants of the household

2.   The land size, buffer zone and High Risk classification of the households in the Yeoval Village Zone would limit their waste water options to septic tank with pump out or Aerated Wastewater Treatment Systems (AWTS). The AWTS would reduce the risk of environment impact and hazard to public health and safety by offering significant treatment of wastewater. However, the AWTS require large amounts of land for irrigation. The land available for irrigation would likely not be sufficient in the typical block size of 800m2 to 1000m2, therefore pump outs will likely still be required although not as frequent as septic tank pump outs.


Flood Prone

1.   Flood studies have not been done at Yeoval, however the NSW guidelines for OSMS (Jan 1998) that all components of the OSMS be located above the 1 in 100 year probability flood contour. There has been a significant increase in rainfall in the last two years. The Buckinbah Creek receives water from a catchment area which had also had a significant increase in rainfall in the last two years. This was evident at Yeoval when mild flooding was experienced on two occasions. Although the flooding was mild, it would have been sufficient to cause environmental and risk to public health due to poorly operating OSMS (expected due to age of the system).




It is expected that the majority of the OSMS systems located in Yeoval would not be operating in a manner that would meet current health and environmental standards (found in the ESD, TWCM, NSW Health). This would be a non-compliance with Councils OSMS management strategy and repair (if possible) or replacement of an OSMS would be required. As majority of the households within the village would not be able to operate an absorption trench while meeting requirements in the guidelines, alternative technologies of waste water treatment would be required. Options are limited and the Aerated Wastewater Treatment System (AWTS) would be required.


The process of installation of a new OSMS system would involve a site assessment which would be at the cost of the householder. The installation and purchase of the AWTS would be at the cost of the householder. If the site is suitable, the council will conditionally grant approval for an AWTS. The typical conditions relate to the operation and maintenance of the AWTS. The householder must comply with conditions issued by Council. It is the responsibility of the householder to operate and maintain the OSMS. The Council will regulate the OSMS through inspections.



AWTS make use of biological processes to breakdown domestic wastewater. The process typically involves the following processes.

1)   Primary solid settlement;

2)   Oxidation of organic matter;

3)   Secondary solid settlement;

4)   Disinfection (typically using chlorine);

5)   Regular sludge removal;


There are various AWTS processes to choose from but the process must be certified by NSW Health before it can be used to process wastewater.


AWTS is a small sewage treatment plant and will therefore require regular maintenance. It is a requirement that the system be serviced quarterly at a cost of ~$300 (2012 price of the contractor approved by council) per service ($1,200/year) for the life of the unit. The householder will enter into an annual service contract with a service agent authorised by Council. The service agent will service all mechanical, electrical and functioning parts of the AWTS including the following components:


·    Chlorinator

·    Replenishment of disinfectant

·    Pumps

·    Air blower

·    Alarm system

·    Effluent irrigation area including spray outlets

·    Biological growth on filter media

·    Sludge return system

·    Water quality testing including free chlorine, pH, dissolved oxygen.

·    Sludge accumulation


Council will also asses performance of the system by monitoring water quality of the effluent from the disinfection chamber. This would require testing of Biological Oxygen Demand (BOD5), suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), Faecal Coliforms and dissolved oxygen (DO).

Cost associated with operating a typical AWTS is shown in the following table

Set Up Cost

Site Assessment (includes soil testing and effluent studies)


Installation and unit cost


Operational Cost

Cost associated with effluent quality monitoring. Can be Included in service fee.


Energy requirement ($/yr)

AWTS (pump and aerator) operates continuously 24hrs/day


Service Agent Quarterly Maintenance ($/yr).

Including parts, repairs and tests as required.


Council Inspection  ($/yr)


Pump Out Cost ($/yr)


1based on $13.85 c/kwh peak and shoulder, $4.65 c/kwh off peak for 1kwh pump and aerator system

2Pump out cost estimated at $180/ pump out once every 30 days.

The cost estimates indicated that a typical AWTS would cost at least $4,270/year. With the energy cost expected to dramatically increase by as much as 20%, it would become a major operating cost of an AWTS.

Septic systems with pump out only option would typically require pump outs every 10 days. Septic tank pump out cost is ~$180 per pump out and would therefore cost ~$6,570/year in pump out cost. This cost estimate excludes the cost of Council inspections of the OSMS. This is anticipated to be the highest cost OSMS option.



·    NSW statistics indicate that a large number of households in the Yeoval Village Zone would require upgrades to their existing on-site sewage management systems to meet current health and environmental standards.  The existing systems are old and many not maintained and would therefore likely fail to comply with guideline requirements.

·    Based on the site limitations of the blocks in the Yeoval Village Zone as well as rainfall and evaporation-transpiration considerations, the only two suitable on-site wastewater management systems are septic tank with pump out (no absorption trench) and aerated wastewater treatment system. The operating cost of septic tank with pump out and AWTS are estimated to be $4,270/year and $6,570/year respectively.

·    In cases where household on-site wastewater management system are found to be non-compliant, the existing OSMS would have to be decommissioned, a new site assessment by Council would have to be undertaken at the cost of the household and a new on-site wastewater management system would have to be installed and commissioned at the expense of the household.



Conventional Gravity.


One of the options considered is the conventional gravity system. While this system has a low operational cost where pumping stations are not requited of minimal, the initial capital cost is high. Mains reticulation has a high cost due to the level control required and pipe size. these systems also have high environmental risk in land subject to overland stormwater flow and flooding. There is also a much higher cost to the resident for on-property works as Government funding does not include work past the property boundary for gravity systems.

Low Pressure System.


The low pressure system is considered to be the preferred system for small catchments. The are fully contained and therefore have a low environmental risk in flood areas. Nil stormwater infiltration. There is also no noticeable odour associated with this system.

All on-property works with the exception of the decommissioning of the existing septic tank and the grey water connection (in some cases) is funded by the scheme.



Council has also been asked to provide some information on what works have been completed for the Yeoval reticulation scheme, to date council has completed;

Ø the on-property audits and design, 

Ø the reticulation design,

Ø specification, design for the sewerage treatment plants,

Ø the environmental assessment for the Sewerage Treatment Plants and the effluent reuse,

Ø land acquisition processes,


These are works completed and costed, to date the cost including project administration is $526,000. Committed expenditure for the supply of pumps, wells and associated works is $581,000, totalling $1.1 million dollars.