Urgent action needed to stop septic tank leakages
A report issued in March 2011 on audit in 2010 of 101 sanitation systems on Rarotonga selected at random by the Ministry of Health, has revealed that 90% of the systems failed the audit.
It was intended to include Aitutaki in the audit but this was cancelled due to Cyclone Pat.
It is both a damning report as well as a wake -up call for serious action to be taken. 50% of the tanks were found to be leaking. The findings indicate poorly constructed and incompetently installed septic tank systems.
The audit was done because lagoon water quality monitoring studies by the Ministry of Marine Resources show that coastal lagoon water quality is gradually deteriorating. While there are several sources of lagoon pollution including livestock wastewater, sediment from excavated building sites and road cuttings, horticultural fertilizers and laundry wastewater, failed on-site sanitation systems such as septic tank and secondary/advanced treatment systems are a contributing factor.
With some 86% of land application systems are soak pits, the findings indicate poorly constructed and incompetently installed septic tank systems. Low awareness about how sanitation systems function is apparently widespread.
Little consideration is given by some installers, builders and homeowners about the effects of storm water on sanitation systems. Some home-owners are also unaware of the importance of gaining access to the septic tank for regular de-sludging and maintenance.
The report is quite technical and space does not permit a full report to be done here. However some of the main points to emerge from the report are mentioned below.
The sanitation industry and inspectors are inadequately trained. Most septic tanks are undersized and with current development densities, soak pits are no longer an acceptable system for applying septic tank effluent to land. Trade training and the registration of expertise under the Public Health (Sewage) Regulations 2008 is imperative.
Improving on site sanitation systems is not just a case of replacing septic tanks. Fixing or replacing a failed septic tank on its own will not significantly reduce the risk to public health or the lagoon. For on-site sanitation systems, dosing the effluent to a well designed land application system is the only engineering solution to reduce these risks.
A sanitation system upgrade programme will only be successful in the long term if the knowledge and skill of the industry and regulators is significantly improved and if there is a co-ordinated, integrated and co-operative effort by key players: government agencies, sewage system designers, suppliers, installers and servicing agents, training institutions and private consultants. At present, many individuals are working to their own standards and with little technical knowledge.
It is recommended that the industry start by agreeing to a programme that will achieve an effective and sustainable on-site wastewater service.
Audit findings on condition of tanks
A large proportion of septic tanks (42%) need urgent repair or replacement. Of the accessible tanks (78 tanks) 49% require desludging. Of the tanks that were accessible to assess for leaking (91 tanks) 50% were leaking. Of the accessible tanks for which information on the number of bedrooms was available (45 tanks) 55% were undersized. Other results were:
• 97% of treatment units are septic tanks and 3% are secondary treatment units
• 86% of septic tanks were installed before 1980
• Only 5.2% of septic tanks have an effluent outlet filter
• 72% of septic tanks have a single chamber, 18% have a double chamber, and 5.2% have three chambers
• 93% of septic tanks were built by the owner or supplied by someone who is not a registered septic tank manufacturer.
• 25% of tanks and tank lids were not structurally sound
• Several tank inlets, outlets and openings were not to standard.
• Of 45 septic tanks for which all information is available, 86% need replacing either because they are leaking, undersized and/or suffer from structural failure.
What the report recommends
Stakeholders meet to discuss developing a programme that will address sanitation issues on Rarotonga and Aitutaki. Such a discussion could include:
1. Suggestions for the review of the Public Health (Sewage) Regulations 2008 and Public Health Sewage Code
2. Training needs for registration
3. Ways to build immediate capacity
4. Coordination and mechanisms of communication between and within industry and government
5. Public education
6. Work plan, timeline, indicators and means of verification
7. Budget (including the establishment of a revolving fund or some other financial support mechanism for upgrades).
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