The discussion forum, held in Auckland on 22 November 2007, was organised by ProjectMax Ltd on behalf of the Australasian Society of Trenchless Technology. The forum was attended by representatives from territorial local authorities, contractors and consultants.

Steve Apeldoorn from ProjectMax said “The discussion forum provided an opportunity for attendees to share experiences and to gain insights from peers working on the issues and dilemmas that are commonly being faced on this technical and legally complex subject.”

Private sewer laterals are often in bad condition and can have a significant impact on the performance of sewer systems. Defects in private sewer laterals can contribute to overflows and blockages, both in the private and public portions of the system, as well as impacting on the operation of pump stations and wastewater treatment plants. The size, materials used, construction practices and ownership responsibilities of sewer laterals are normally different than that of the publicly owned and managed sewer collection system. As such the techniques used for investigation, repair and funding of improvements to main sewer pipes are not normally applicable to private sewer laterals and different approaches are required.

The topics discussed at the forum included:

* Identifying and locating private sewers * The impact of private sewers on an I/I/E program * Inspection and identification of defective private sewers * Management and approaches to remediation of defective private sewers * Trenchless Technologies that are available for the repair of defective private sewers * Results that can be achieved through the repair of private sewers

The issues faced in New Zealand with regard to private sewer laterals are not unique. The framework for the forum was based on findings in the United States produced WERF (Water Environment Research Fund) report on ‘Methods for Cost-Effective Rehabilitation of Private Lateral Sewers’. Reviewing this report highlighted that the same issues encountered in New Zealand are also being faced in the United States.

Some of the main points discussed at the forum included:

* Typically 40 per cent of the total inflow and infiltration into a sewer system originates from private sewer laterals. * The majority of the problems experienced with private laterals originate from the initial construction. * The definition of what is a private sewer varies significantly from council to council. * Most councils do not know where private laterals are located. * Currently there is no common standard for determining the ‘Pass’ or ‘Fail’ grading of a private lateral. * A significant amount of leakage can occur from new subdivisions due to poor workmanship and construction loads. * Most property owners do not have the knowledge or resources to proactively manage their private sewer laterals and do not understand why they need repair. * Most property owners undertake repairs when presented with good information and an understanding of the reasons why their sewers should be repaired. * The best response to defective drainage notices is when the property is up for sale. * The amount of leakage entering into a sewerage system can vary significantly from area to area. The leakiest catchments provide the best opportunities for improvement.

The forum identified the need for national standards and ‘common practice’ policies. Issues that should be explored further in the development of the national standards include:

* The definition of a private sewer lateral. * Best practice procedures for inspection and testing of private laterals, including a legal definition of what is a defective drain. * The enforcement of pre-sale CCTV inspections or owner-supplied property condition reports. * A national qualification for investigation practitioners. * Practices to prevent inflow and infiltration occurring in new subdivisions. * Options for funding improvements to private sewers. * Options for communication and education of the public on matters relating to private sewers.

This discussion forum is intended to be the first in a series of such forums on topics that are relevant to the industry. The next forum is planned for 13 March 2008 and will cover what constitutes the appropriate quality of investigations and diagnosis for sewer rehabilitation. People who wish to attend the next forum can register their interest by sending an email to info@projectmax.co.nz.

ProjectMax, which is organising these forums for ASTT, has for the last 7 years worked with councils to help them address problems with private laterals. The company has helped councils develop a road map as to the assessment, analysis, program development, method selection and legal and financial implementations in undertaking a lateral rehabilitation program. ProjectMax can help and facilitate your council to start such a program.