Using the Versatility of the CIPP System to address challenges

Abstract

It is a well-known fact that Cured in Place Pipe (CIPP) Lining is a trenchless methodology for the rehabilitation of deteriorated pipes and that it can extend the design life of the rehabilitated assets by at least 50 years. But the CIPP system is much more than that. There are wide choices of resins with different physical and chemical properties. There are different varieties of felt liners such as plain or reinforced. There are different methodologies of installation, the typical method, over the (man) hole liner impregnation or pull and inflate and there are different methodologies of resin curing. By utilising all these different alternatives, CIPP becomes a very flexible system and is able to answer many challenges that other systems cannot answer. In this presentation two case studies will be considered. The first one will show how the resin’s physical properties can be utilised to address earthquake movements and to minimize the installation cost and disturbance to the stakeholders and the client. The second case study will show how the type of liner felt and the installation methodology can be applied to enable the installation in a small, inaccessible and environmentally high risk area. 1. Case Study One (CIPP Lining of Christchurch WWTP Earthquake Damaged Clarifiers) In September 2010 Christchurch was struck by a 7.1 magnitude Earthquake. Aftershocks, often very severe, continued for a few years after that event. The Challenge The February 2011 Christchurch aftershock was a powerful event that severely damaged New Zealand's second-largest city, killing 185 people in one of the nation's deadliest peacetime disasters. Paper 21132- 1 Figure 1 Extent of damage due to seismic events in Christchurch The February earthquake caused additional damage to the Bromley Waste Water Treatment Plant which is the main facility in the city. The damage was dramatic and significant and instantly put a large part of the plant out of commission. The four Clarifiers which are each 60m in diameter, had severe damage to their flooring due to liquefaction (both uplift and settlement). The inlet pipes under the Clarifiers had suffered significant damage too. Figure 2 Bromley wastewater treatment plant The influent pipes under the clarifiers are RCRRJ Class Z pipes with an Internal Diameter of 1,800mm. These pipes needed to be inspected to quantify the damage. They were full of sewage and could not be emptied due to the risk of uplifting caused by the very high ground water table. Divers were utilised to do underwater inspections. The survey was undertaken using a handheld CCTV system. The underwater visibility was very poor, at a less than 1m at the entrance and quickly deteriorating to about 200mm. The renovation methodology and solution for repairs required answering three main concerns: Movement, Strength and Constructability. One of the main challenges in considering the repair options was the ability to work under water in order to avoid having to drain the pipes. A number of options were considered for the repair work: Open Cut replacement, Slip Lining, Coating, Joint repairs and CIPP. After careful consideration and consultation with the different parties involved, only the CIPP option took care of all the requirements while the other options fell by the wayside for one reason or another Paper 21132- 2

Techniques