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Sewerage Rehabilitation For Extended Infrastructure Life

by Richard Powell on October 04, 2019

Situation

Plumbing and Pipeline Solutions were initially contacted by Essential Water Broken Hill to exhibit what our capabilities were in the field of sewerage infrastructure rehabilitation.

The organisation were having issues with concrete that was affected by H2S Gas in both their sewer pump stations in their network and storage tanks within their sewer treatment plant.

PPS completed a thorough inspection of the waste water treatment plant and the pump stations within the network. It was identified in the wet wells of the sewer pump stations that a previous product applied by another contractor had failed in places and this would need to be removed.

Problem

During the site inspections PPS were informed that Essential Water Broken Hill had plans to build a new wastewater treatment plant in approximately 5-7 years, so our focus was to ensure that any solution provided would be able to last the duration, meeting client expectations while delivering within budget.

Photos and measurements were taken onsite, and meetings were conducted with Essential Water personnel to determine the required outcome so that PPS could put together a proposal that met with all expectations of the client.

Challenges to PPS

One of the challenges that was faced was access to the sites and the co-ordination of works. As the structures identified requiring rehabilitation needed to continue to play a role in the operation of both the treatment plant and the network.

Other issues requiring consideration were access to the tanks in the wastewater treatment plant which were 10 metres in diameter and 6 metres deep. All works were to be conducted under confined space entry conditions, both in the network and the waste water treatment plant with continuous air quality monitoring to ensure safety and timely delivery as promised to Essential Water.

Solution 1

Plumbing and Pipeline Solutions has a number of rehabilitation products suitable for use on sewer infrastructure.

It was decided on the wastewater treatment plant that we would complete minor concrete repair using RenoCrete.

RenoCrete is the ideal product to re-surface degraded concrete. Once applied it creates an effective barrier against waterborne salts and atmospheric gases. It is a hardwearing, seamless, waterproof membrane that is safe for potable water. This will surely protect your sewerage system and thus was ideal for this project.

RenoCrete is a water based, environmentally friendly product that is solvent and VOC free. Once the concrete repair was finalised the complete tank was sealed with RenoSeal.

RenoSeal is a spray-on application that creates a monolithic, seamless lining that conforms to any shape and size. Its elastic properties allow it to tolerate vibration, expansion, contraction, movement, abrasion and impact.

RenoSeal is also tack-free within seconds of application. In the wastewater treatment plant only minor concrete repairs were completed and then tanks were fully sprayed. This was to ensure we met with Essential Water’s budget and life expectance of 5-7 years.

Our polymer based concrete repair was used in areas of tanks that has severe gas attack to prevent any further damage.

Problem 2

As all site inspections could only be completed while the tanks were full and operational, there were issues identified when we arrived onsite and as such the first tank was emptied.

It was noted that the control joint was failing in sections and we were required to provide an urgent solution to seal the joint to ensure no leakage from the tank. The support for our product supplier Axon Noble recommended to leave the control joint as is and apply Intercrete 4872. This is a tear-resistant, flexible, waterproofing sealant tape with good resistance to a wide range of chemicals, which provides an impermeable waterproof seal over wall/floor tank intersections, ‘live’ cracks and expansion or construction joints and is bonded to concrete using our range of cementitious coatings (Intercrete 4840, 4841 & 4842).

Solution 2

The recommended method for installation was to leave the centre of the fabric un-coated (top and underside) to allow for future expansion and contraction. This proposal was accepted by Essential Water and applied to the control joints in the tanks prior to application of RenoSeal.

In the network PPS provided a comprehensive repair of the wet wells by first removing the previous failed product. It was decided that we would use high pressure water to remove the material from the walls of the wet well and then vacuum out.

As the sewer pump stations were needed to keep running we worked in one half of the wet well at a time with the other half being live still, pumping sewer from the network to the treatment plant. This meant that all works were completed using breathing apparatus with continuous monitoring of the H2S gas levels.

A full repair of concrete was completed in the pump station wet well and finished off with a coating of RenoSeal.

While the rehabilitation of the works was challenging the co-ordination of the works proved to be the most important part of the project. We should note too that PPS had to present a fixed schedule to Essential Water to ensure that we could meet the timelines proposed so that they could continue to process the wastewater in the treatment plant and operate the pump stations in the network.

The large size of the tanks meant we needed to access areas at a height of 6 metres but due to time restraints we could not have downtime building and removing scaffold. The client accepted our proposal to use an elevated work platform (EWP) which could be craned in and out within an hour, hence we were able to complete the tank and remove the EWP and have the tank back online within 2 hours.

Timeline

The works were completed within the schedule and budget applied for the works. PPS tooled their purpose-built rehabilitation Pantech to site with required equipment and had the material delivered directly to the site. The crews worked on a 3 week on 1 week off roster and were flown in and out of Broken Hill until the completion of the project which was approximately 10 weeks in total.

Result

At the completion of the project PPS had completed the following on the sewerage:

For more information on wastewater structures repair and sewerage rehabilitation,  please take a look at our service offering here.

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