Guidance for the use of sewage holding tanks associated with temporary ablution blocks

A Sewage Holding Tank (SHT) is an alternative to a conventional on-site sewage system with special and limited applications. The SHT provides a means to collect and temporarily store sewage from a facility, for subsequent removal and transport to an approved treatment and disposal site thus no on-site wastewater disposal should occur with the use of the SHT. Depending upon the facility served or the particular set of circumstances surrounding the use of a SHT, the expense of sewage pumping, hauling, and disposal at an approved facility can be very costly. In addition, the potential for operational/management problems with resulting public exposure to raw sewage is significant. For this reason, the SHT is only approved for commercial and temporary use only and usage is limited to a maximum of 12 months. The use of the SHT must be approved by the Department of Health (DOH) or the local government for the area in accordance with Regulation 4 or 4A of the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974.

Performance standards

The SHT must provide safe and adequate temporary storage of sewage, with scheduled and approved pumping service followed by approved off-site treatment and disposal of the stored sewage. By design, installation, and operation and maintenance SHT must not contaminate ground or surface waters, expose the public to untreated sewage or be a source of nuisance odours.

Application for use

Prior to installation

Before installing and using a SHT, an approval that addresses installation, operation and maintenance must be obtained from the DOH or the local government. The application should include specific information and requirements for pumping service frequency and approved disposal of holding tank contents. The local government may permit SHT only in the following cases:

• Controlled, temporary, commercial usage; 
• The development complies with the provisions of the Government Sewerage Policy. This means that sewer connection may be necessary and the number of people may be limited to the lot size of an unsewered lot.
• Repair of failing on-site sewage systems - but only where no other option is feasible. 

The local health officer must first determine that the following options are not feasible:

• On-site sewage system; and
• Connection to sewer.

Inspection prior to use

The SHT installation must be inspected by the Environmental Health Officer (EHO) before use. The EHO may inspect various items, including, but not limited to, the following:

• Water-tightness of the tank, tested at site after installation, by filling with water;
• Non-buoyancy in high groundwater areas or conditions;
• Leak-proof nature of the service access(es), access ports, risers, lids, and covers;
• Methods to secure the lids and covers from inappropriate or unapproved access;
• Methods of venting provided by the design and the installation; 
• Impervious surfaces around the access ports, equipment and methods for cleaning sewage spills; and
• Alarm functions.

Design Standards

Tank Design / Material Requirements

Holding Tanks must be approved by the Chief Health Officer to the requirements of Regulation 50 (1) (b) of the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974.The design and construction of the tanks shall be certified by a structural engineer confirming the structural adequacy and constructed of material that complies with the relevant Plumbing Codes, Health Regulations and Australian Standards. The DOH website maintains a list of DOH approved holding tanks and a compilation of Australian Standards for water holding tanks.

Sizing

Establishing the holding tank capacity requires consideration of both design and operational aspects. The required storage capacity depends upon two factors: daily sewage flow, and available or optimal pumping service frequency.

Design Considerations

In general, holding tanks requiring regular service should be pumped once or twice each week. Some commercial facilities may require more frequent service while some low-use facilities may function quite satisfactorily with less frequent service. However, pump outs should occur at least weekly because less frequent removal may lead to odour-related nuisance problems.

Alarms

Both audible and visual alarms are required.

• The alarms must be set to signal at the "time-to-pump" and "exceeding reserve storage volume" level

• The audible and visual alarm enunciators must be located outside the facility.

Venting and Odour Control

• Special care will be necessary however to assure that pumping and service access port lids are leak-proof so all sewage gases will vent through the facility waste vent pipes.
• Vent pipes should terminate high enough and away from area of human activity to avoid vent stack odours and related nuisances. To assure that the sewage gases vent through the vent stack, pumping and service access port lids must be leak proof.

Operation and Maintenance

Before a permit is issued for use of a SHT, the owner of the system must submit to the EHO complete documentation in a manner prescribed by, and address these items to the satisfaction of, the EHO:

• Service contract with a certified and licensed sewage system pumping firm; and
• Frequency of pumping, by schedule.

Operational Permit

The EHO must require a service agreement to over see operation of the SHT. The service agreement must include as a minimum:

• Pumping, hauling, and disposal must be by a licensed sewage pumping contractor;
• Disposal of sewage from a holding tank system must be at a site or sites approved by the EHO in the jurisdiction where the sewage is disposed;
• Operational records must be maintained by the owner and service provider which include information about pumping frequency, sewage volume, disposal site(s), proof of acceptance by the disposal site operator, alarms, and system servicing and repairs;
• Copies of operation records must be submitted to the local government.

Disposal of Contents

Contents of the holding tank must be pumped, hauled and disposed of in a manner approved by the local government. No sewage from the holding tank system must be applied onto the ground surface, into ground water or surface