Overview

Corrosion and gas attack to sewerage access chambers is a huge problem facing municipal councils around the world. Over time, gas buildup inside the system corrodes the chamber walls, eventually leading to total system failure. Conventional treatment methods are costly and often require the interruption of essential services while chamber repairs are carried out.

McRobert Contracting Services recognised the need for an effective solution and developed processes and methodologies resulting in the MCS Access Chamber Relining System.

The MCS Access Chamber Relining System offers the following benefits:
The MCS Access Chamber Relining System not only restores but improves the structural integrity of the existing chamber providing a safer working environment

• Minimum disruption to services
  The Utilization of purpose made systems such as our plug and release and internal bypassing systems that minimize disruption
• Restoration of Structural Integrity
  Our method provides a 100% (10mm thick) gas tight PVC structural lining that includes the benching, chase, walls, roof and lids
• Low cost and expediency
  Our relining methodologies have been developed to ensure we maintain a safe working environment that enables us to complete each task more efficiently while spending the minimum amount of time within the chamber

The MCS Structural Relining system enables projects to be carried out within tight timeframes at significantly lower costs than other available methods Major PVC components are fabricated in kit form at our factory and transported to site as required MCS has a team of fully trained staff competent in all aspects of our operations including confined space certification

Case Study: Coral Bay, Western Australia

In July 2004 a new wastewater scheme was commissioned at Coral Bay. By February 2009 (just 4 years later) it was discovered that every one of the schemes 12 access chambers had been severely corroded by gas attack from the high concentrations of sulphide gas in the towns water supply. In most cases, reducing chambers wall thickness by up to 50%. One of these access chambers actually ruptured, resulting in seawater intrusion and significant overloading to the pump station

If traditional access chamber replacement methods were to be used, bypassing and dewatering would have been the only option due to the close proximity of the sewer system to Ningaloo Reef and the danger of wastewater contamination.

Replacing the three most critically affected access chambers was estimated by the Water Corporation to cost $795,000.

MCS was invited by the Water Corporation to tender for the contract to repair the three most critically affected access chambers The relining process was carried out utilizing our plug and release systems to contain and control sewer flows during operations

MCS completed the entire project ahead of schedule saving the Water Corporation in excess of $450,000 MCS provided a 50 year guarantee on all works at Coral Bay

MCS's work at Coral Bay won the 2009 Australian Award for Engineering Excellence

Lifting the Lid on a Sleeping Giant

Australia, along with many countries worldwide is literally sitting on a sleeping giant that slowly but surely grows larger day by day. Major problems are being found within systems where unprotected internal surfaces have been exposed to gas attack Left unchecked, this corrosion can lead to eventual system failure, interruption of essential services and contamination of the environment.

How Big is the Problem?

Gas attack can affect any gravity sewerage system that has unprotected internal surfaces As towns and cities expand so must their sewerage systems requiring the sewerage to travel longer distances through more pumping stations, these actions cause a substantial increase to the volume of gasses released due to the increased turbulence In Western Australia alone, there are an estimated 10,000 access chambers and recent CCTV surveys indicate many thousands of these require urgent attention. These problems are Australia wide.

How Long Does it Take?

The time required can vary considerably depending on such things as the type of gas and the amount of turbulence generated For example in a recent contract MCS completed at Coral Bay the sewers were only 4 years old when it was discovered the entire 12 access chambers had corroded to less than 50% of their original thickness due to the high concentration of sulphide gas within the towns domestic water supply

The Consequences of Inaction

Corroded access chambers left to degrade will eventually fail. As the extent of corrosion increases the structural integrity of the chamber decreases at a faster rate Failure to address these important issues will result in a breakdown of the system and disruption to essential services Corroded access chambers present a dangerous working environment for municipal employees and contractors who need to gain access to the systems.

What Can Be Done

(A) Complete Replacement
The entire access chamber can be excavated and replaced. The cost and disruption to services make this impractical for most cases.

(B) Spray On Coatings
Various spray-on technologies are available for relining access chambers including:

• Multilayered poly resin
• Grouting/rendering
• Polyurethane coating

Spray-on technologies have proven to be unsuitable for use in restoring severely corroded chambers where the structural integrity could be at risk of being compromised. Also, limited warranties apply to most of these techniques.

(C) Structural Relining
McRobert Contracting Services have developed a process and methodologies (patent pending) for the low cost, expedient relining of corroded access chambers. MCS also provide an unconditional 50 year guarantee

Contact McRobert Contracting Services today for more information.