Performance Testing of Non-Pressure Stormwater Pipelines – A review and Update of CPAA Guidelines
In many cities around the world, infiltration and exfiltration in sewerage networks present a challenge for engineers to address when planning a new network construction. Hydrostatic pressure, or the more convenient, air pressure or vacuum testing are usually specified to assure pipeline capability to handle wastewater without allowing infiltration or exfiltration. Typically this infiltration or exfiltration is via joints or defects and is independent of the pipe material used.
For Stormwater pipelines and culverts, watertightness is often a secondary requirement as lines are often designed with lateral connections. These connections are typically to various subsoil drains, making the pipe system open in both directions to the ground water system. For this reason non-watertight pipes such as flush joint pipes are acceptable in such installations.
In some specific Stormwater installations, watertightness of the pipeline is essential for the pipeline to achieve its design serviceability goals of collecting surface water only. Extensive infiltration may affect the capacity of the line or cause migration of the surrounding soil, whilst extensive exfiltration might affect the geotechnical stability of some installations or cause damage to adjacent properties. Where watertightness is critical, either hydrostatic or air testing may be appropriate for quality assurance.
However, it is generally understood that the level of watertightness required for most Stormwater pipelines is less than that required for wastewater and it is appropriate to specify different acceptance criteria to those specified for wastewater lines.
Typically, Steel Reinforced Concrete Pipes in Australia and New Zealand are designed, manufactured, and factory tested to AS/NZS 4058:2007, with the jointing system providing a watertight pipeline when properly installed. New Zealand industry generally specifies visual inspection or CCTV inspection to evaluate the conformance of installation of Stormwater concrete pipes to project or TA specifications. Some TA’s prefer watertightness or air testing as a quantitative test for installation quality assurance rather than the qualitative CCTV test. Whilst appropriate in principle, there is considerable variability in acceptance criteria, test procedures specified and interpretation of the test results. Furthermore, there is often no differentiation between Sewer and Stormwater installations, or various pipe materials.
The existing Concrete Pipe Association of Australasia (CPAA) Technical Bulletin Field Testing of Pipelines and Joints, last reviewed in 1995, does not distinguish between sewer and stormwater applications. The CPAA is aware that significant changes have occurred since 1995, in overseas Standards and Specifications to account for changes in technology and Health and Safety requirements for site testing.
In early 2016 the CPAA initiated a comprehensive review to develop a Guideline for Performance Testing of Non-Pressure Stormwater Pipelines. This Guidelines were proposed to be based on review of specifications and field testing experience from both Australia and New Zealand and on the latest overseas and local experience. The new guidelines as published by the CPAA present the results of this review work and the details of the updated acceptance criteria and test procedures developed from both theory and field testing experience.
Click here for the full guideline: CPAA Engineering Guideline: Performance Testing of Installed Non-Pressure Rubber Ring Jointed Concrete Stormwater Pipelines
Written by Husham Issa Al- Saleem , Humes – CPAA Member Company