Gravelless Trenches and Fabric/Textile Wrapped Distribution Pipes

Posted on February 27, 2013 by Ian Gunn

This technology associated with domestic wastewater septic tank effluent soakage trench systems has been around in the USA for many years, and recently entered the Australia and New Zealand market. Following an enquiry re the status of this system in the local context, On-Site NewZ has prepared a review of gravelless trench effluent dispersal systems and added it to the Pages sidebar of this blog under the title of this post.

The issue that arose in the enquiry to On-Site NewZ was whether the wrapped pipe distribution technology was a “treatment and dispersal system” or just a “dispersal system”.

Greywater Management and Water Reuse

Posted on January 30, 2013 by Ian Gunn

On-Site NewZ recently had an enquiry re the availability of suppliers of treatment systems for reclaiming water from domestic greywater sources for toilet flushing and garden watering. The best advice On-Site NewZ was able to give was to go to the “Greymatters” website at www.greymatters.org.nz which provides links to eight companies supplying greywater treatment systems and components.

The “Greymatters” website has been set up as a point of reference “for all matters concerning greywater reuse”. [Actually greywater is neither "used" or "reused", but can be a source of reclaimed water following treatment.] The origins of the website and the names of the councils supporting it are cited in the “About” pages.

The website explains “what is greywater” and also has pages re the latest reasearch (six projects), technical information (110 reference publications), links to all NZ councils, and lists of websites and advisors/consultants involved in greywater matters.

[NOTE: The original copy of this post earlier today included an incorrect link address to the "greymatters" website which has prompted several responses. The above link is now the corrected one (the extra "t" in "matters" has been deleted).]

Greywater Management and Water Reuse

Posted on January 30, 2013 by Ian Gunn

Design Reporting Provisions in AS/NZS 1547:2012 On-site domestic wastewater management

Posted on December 14, 2012 by Ian Gunn

The provisions within AS/NZS 1547:2012 (AS/NZS 1547) dealing with design reporting cover a vast range of topic areas scattered throughout the Standard, some of them overlapping. The question arises, what is an appropriate structure and content for a design report conforming to the provisions of AS/NZS 1547?

Incorporating content dealing with every aspect of the design process considered in the Standard would seem to be a complex undertaking, and could indeed be unnecessary for many small scale projects. Hence, a decision needs to be made by the designer as to the level of detail necessary to ensure design adequacy, and to confirm the recommended system covers all relevant design elements in presenting an outcome appropriate to the site, soil, environmental conditions, design and operational risks, and the client’s expectations.

Those provisions dealing with “designer” and “design reporting” in the Standard have been extracted into Table B of the document “Design Reporting Provisions – AS/NZS 1547:2012 On-site wastewater management” which can be accessed from the pages sidebar to this blog post. Table B is preceded by Table A which sets out suggested topic and sub-topic headings for a typical design report, and links these to the relevant provisions in the Standard by reference to Table B.

Overall there are five sections in the suggested report content, these being supported by five appendices.

Introduction
Site and soil evaluation
System design
Installation and commissioning requirements
Operation and maintenance requirements

Appendix A: SSE report
Appendix B: Design calculations
Appendix C: Risk management summary
Appendix D: Loading Certificate
Appendix E: Site plans and construction details

The host of provisions re content of a design report as detailed in the Standard would appear to require very detailed and complex reports. However, what the Standard does is set out a comprehensive set of factors which need to be addressed in any design, but without providing guidance on how those factors are to be reported on. The challenge is to identify those factors which are important within a specific design.

The best approach for a designer may be to compile a checklist of items essential to covering all aspects of design, and then to use this for specific design projects to confirm which are relevant to the particular site and design brief. Table B provides the essential items for compiling such a checklist. Individual designers can thus draw up checklist appropriate to their area of on-site wastewater management practice and ensure that all relevant provisions in AS/NZS 1547 are not overlooked.

It has to be borne in mind that design reports have to be thorough, clear, concise and economical. Over reporting increases costs to the client and diminishes competitive edge where several consultants may be quoting for a project. However, although a design report which conforms to the provisions of the Standard may, on the face of it, be more costly than a non-conforming report, the AS/NZS 1547 compliant consultant should be able to emphasise that any extra cost provides quality and value in terms of a sustainable design solution.

On-site Wastewater Systems – Improving Performance via Remedial Actions

Posted on October 31, 2012 by Ian Gunn

During 2011 On-Site NewZ prepared a schedule of remedial maintenance and remedial upgrade actions following an enquiry from a NZ council re dealing with poorly performing and older systems. Essentially the advice sought was how to address potential “failure” from systems which may not have been maintained appropriately (if at all) and are showing signs of “stress”.

On-Site NewZ has subsequently updated the “Review of Potential Remedial Actions”, and a copy is now available on the “pages” sidebar to this blog under the same title as this post “On-site Wastewater Systems – Improving Performance via Remedial Actions”.

AS/NZS 1547:2012 On-site Domestic Wastewater Management – Changes and Revisions from the 2000 Version to 2012 Version

Posted on September 8, 2012 by Ian Gunn

On-Site NewZ has prepared a detailed overview of the changes to the 2000 version of AS/NZS 1547 as published in the new 2012 version. This incorporates an outline of the substantive changes supported by three reference documents which set out comparisons in content between the two versions of the Standard. The expanded contents listing of the 2012 Standard (published on 6 May in the pages sidebar to this Blog) has been used as the basis for detailing the comparisons.

To acess the PDF files setting out the changes and revisions, go to the pages sidebar under the topic “AS/NZS 1547:2012 On-site Domestic Wastewater Management – Changes and Revisions from 2000 Version”.

Loading Certificate in On-site Domestic Wastewater System Design and Operation

Posted on August 12, 2012 by Ian Gunn

Over many years On-Site NewZ has been aware of the problem that arises when an apparently code complying on-site wastewater system shows symptoms of poor performance and/or failure. First, the owner is likely to blame the drainlayer, who will then question the adequacy of the design and blame the designer. The owner is also likely to blame the regulatory authority (usually a regional or district council) who approved the design and installation. Manufacturers of on-site domestic wastewater treatment units can also get caught up in this “blame game” when treatment quality deteriorates and irrigation lines or soakage fields become blocked.

Designs are usually developed around a dwelling capacity translated into an occupancy level and design flow, then configured in terms of sizing and location of the wastewater treatment and land application system to fit the on-lot site and soil conditions. If the design is appropriate to capacity requirements and site and soil conditions, and its integrity is ensured by high quality installation (certified by the designer as being in compliance with the design), verified by a regulatory authority through a certificate of compliance, and supported with detailed operation and maintenance instructions, and the system still performs poorly or fails, then questions arise as to when, how and why? Has the owner, through deliberate or inadvertent omission, or neglect, or overload, or misuse, contributed wholly or in part to the poor performance or failure?

Unwittingly (or in some cases deliberately) owners can contribute significantly to system failure through changing the loading or misusing the system beyond the design and operational parameters originally set and signed off on. Examples of detrimental owner actions are:

Extending (without permit) the size of the dwelling with extra bedrooms to accommodate an increased family or occupancy size. It may well be a “granny flat” is added to the property, or an extra family moves in.
Converting non-bedrooms or garages to sleeping areas to accommodate temporary or permanently increased occupancy.
Erecting buildings (outhouses) over land application systems.
Positioning tents, caravans or other holiday accommodation over land application areas for extended occupancy periods.
Changing dietary habits (such as taking up vegan menus).
Using medications detrimental to treatment unit operation and land application system performance.
Developing medical conditions requiring higher than normal water use (such as extra baths).
Installing high water use fixtures not allowed for in design (such as garbage grinders/food waste disposal units; dishwashers; high use washing machines; fish scaling and gutting sinks; spa baths and/or pools)
Replacing flow restrictor fixtures and installing high water use fixtures.
Changing from rainwater supply to bore water or reticulated community water supply.
Switching off electricity to the aerated treatment unit in order to save on power costs.
Overlooking or ignoring operation and maintenance instructions.
Failing to carry out recommended operation and maintenance requirements.
Failing to renew annual maintenance contract.

Another issue is when a property is sold and the new owner is unaware that the dwelling is serviced by an on-site wastewater system, or has received no information from the previous owner re the type, capacity and maintenance requirements of the system.

To deal with the matter of owner responsibility in use of their on-site wastewater system, the concept of a “loading certificate” was introduced into New Zealand design practice some years back and has now been incorporated into the latest version of the Australia/New Zealand Standard AS/NZS 1547:2012. The purpose of the loading certificate is to set out the design and operational limits of the installed system so that the owner/occupier and users of the dwelling have a clear indication of the limits to system use, and their operational and maintenance responsibilities. The clear message is, go beyond the capacity of the system and/or neglect its maintenance, and poor performance and/or failure may result.

Where diligent adherence to the provisions of a loading certificate can be demonstrated and a system has still failed, then the owner may quite rightly look for a reason to blame someone associated with design, manufacture, installation or regulatory oversight as the main contributor(s) to the performance/failure issues.

AS/NZS 1547:2012 covers the matter of a “loading certificate” in several sections:

definitions – loading certificate is defined on page 15 of the Standard;
designer’s role in providing a loading certificate in the design report and operating instructions (page 27);
property owner/occupier role in adhering to the limits of the loading certificate (page 29);
estate agents role in passing on the loading certificate to a new owner/occupier (page 29);
content of a loading certificate as set out in the design report (page 70); and
inclusion of a loading certificate within the operation and maintenance instructions (page 196).

Ideally the loading certificate should be also provided as a stand-alone document displayed in a prominent place in a dwelling – one suggestion received by On-Site NewZ is that it should be produced as a laminated A4 sheet and fixed to the inside of the door of the toilet compartment at knee height!

For an extract of the provisions in AS/NZS 1547:2012 relating to loading certificate and its content, go to ”Loading Certificate in On-site Domestic Wastewater System Design” in the pages sidebar of this blog.

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