Maintenance Hole Rehabilitation – Mildura

Project Summary Sheet

Customer: Lower Murray Water

Location: Mildura, VIC

Delivered: June 2015

The Challenge

An inspection in Mildura showed that several maintenance holes required some degree of rehabilitation.

While for most, recommendations for rehabilitation ranged from coatings to protect the surfaces of maintenance holes in good condition, through to thick re-build coatings to restore structural strength, two maintenance holes were found to be beyond repair, needing total re-building. They were deep maintenance holes in a built up part of the city.

The Solution

Interflow has a range of maintenance hole coatings to meet different requirements and so was able to propose a program matching the type of coating with the maintenance hole rehabilitation needs.

The Project

The two maintenance holes requiring re-building were over 10 metres deep, located in the roadway near the Quality Hotel Mildura Grand, a Mildura landmark. It was proposed to re-build these maintenance holes with steel reinforced calcium aluminate cement to provide structural strength and corrosion resistance.

A vital part of any maintenance hole coating project is thorough cleaning to remove all acid attacked concrete. On this project, cleaning was completed using a 25,000 psi hydro-demolition unit which ensure the surface was cleaned under strict safety procedures to a suitable condition to be coated.

An internal scaffolding tower was erected to allow safe access in the deep maintenance hole. This was a considerable achievement in a maintenance hole with an internal diameter of only 1.2 metres. The Calcium Aluminate Cement (CAC) wall required two layers of steel mesh reinforcement. Anchor holes were drilled in the remains of the existing maintenance hole wall in a grid with spacings between 400mm and 600mm.

Reinforcing bars cut to lengths of 120mm were epoxied into these holes to a depth of 50mm. Reinforcing mesh was tied to these epoxied bars.

Temperatures during the day approached 40°C. Coating was carried out at night in cooler conditions to guard against the CAC curing prematurely in the heat. Spraying of Interflow’s Interchem® CAC mortar was undertaken in three layers to build up the specified thickness of 90mm. The reinforcing bars provided a guide to the applied thickness.

Conclusion

The project was successfully completed in these demanding conditions. The corrosion resistance of Interflow’s Interchem® CAC in these harsh sewer conditions means that these maintenance holes will have a long effective life.

Interflow is committed to offering its customers optimum solutions of the highest value for pipeline rehabilitation.