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On-site Wastewater Management in New Zealand Wastewater Servicing Practice
By Ian Gunn, academic and professional engineer.
On-site wastewater servicing has traditionally been associated with septic tank and soakage trench systems as a temporary measure in urban fringe, rural residential or holiday area development. The expectation is that on-site wastewater systems will have a short life, will eventually clog up and fail, and thus inevitably require connection to a sewerage system.
This traditional perception is currently being turned around by the availability of modern technologies together with new standards and practices for investigation, design, construction, operation, maintenance and monitoring. This is driven by a focus on management of the implementation and approval processes for design and installation, followed up by operation, maintenance and performance monitoring procedures all delivered by well informed and trained practitioners.
The framework for this new management focussed approach has been the joint Australia-New Zealand Standard AS/NZS 1547:2000 “On-site Domestic Wastewater Management”. This standard recognises that in spite of the availability of design rules and system sizing guidelines from earlier standards and design manuals, a significant level of ongoing system failures and poor performance of on-site systems is due to a deficiency in the overall procedures associated with system implementation, approval, supervision and monitoring.
There are in fact no superior design rules for sizing, for example, trench systems according to soil type and effluent discharge quality. However, if robust procedures are in place for land use planning, site investigation, design, installation, approval and ongoing performance monitoring, backed up by good user guidelines and homeowner awareness, then on-site systems can deliver a sustainable wastewater servicing solution.
A key to delivering outcomes
A key to delivering such an outcome is the level of training and experience associated with the range of practitioner groups involved in on-site wastewater servicing. These include planners, site and soil assessors, designers, equipment manufacturers and installers, drainage contractors, pumpout operators, performance monitoring inspectors together with regional council environmental officers and district council building consents officers.
Currently training programmes for on-site wastewater practitioners are run on an adhoc basis. The Australian Centre for Environmental Training (cet) has developed a range of courses which have been delivered in NZ over the last five years.
More recently (2006) BOINZ in association with On-Site NewZ presented a two-day introduction and design course on eleven occasions at nine centres throughout the country. Of the 300 attendees one third were consultants (involved principally in design), one third were district council officers (involved in approvals and building consents) and one fifth were contractors, installers and equipment manufacturers.
Meanwhile, Water Industry Training is developing a set of unit standards for on-site wastewater management which once approved by NZQA will provide a basis for future training course development and practitioner competency assessment. These unit standards are expected to be registered later in 2007. NZWETA through accredited NZQA private training Opus Environmental Training Centre will be offering the unit standards when registered.
Ian Gunn is an academic and professional engineer who has specialised in on-site wastewater systems for over 35 years as a designer, peer reviewer, Standards Committee member, and design manual/guidelines author. For the last 10 years he has published “On-Site NewZ”, a newsletter and information service for the on-site domestic wastewater management industry.
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