The Priority Sewerage Program (PSP) has been established to improve sewerage services, including sewer reticulation, transfer, treatment and discharge schemes within unsewered communities and townships in New South Wales. Specifically, the scheme is designed to improve public health and protect the environment especially local waterways and catchments and is part of Waterplan 21, Sydney Water’s long-term vision for sustainable wastewater management.

The program involves the undertaking of investigations, works and activities primarily to provide reticulated sewerage services to properties currently using on-site sewage treatment or collection systems.

In May last year, Codmah started PSP works in the Upper Blue Mountains region. The scope of the contact involved installation of a low pressure sewer system and gravity sewer pipelines. It involved a range of activities from the excavation, horizontal directional drilling, under-boring, pipe installation, positioning and fitting of sewer lines and junctions to the supply and compaction of bedding concrete and side support overlay.

Scope of works

The low pressure sewer system reticulation works were focussed on the townships of Medlow Bath, Blackheath and Mt. Victoria and involved the installation of approximately 20 km of polyethylene pipe of various diameters ranging from 63 mm to 250 mm.

Construction of gravity sewer works in the catchments GR770, GR767 & GR800 in the township of Blackheath used PVC pipe. GR770 involved trenching of 1,220m of DN150 PVC and 540 m of DN225 PVC and also included installation of approximately 49 pre-cast and in-situ access chambers while GR767 and GR800 involved trenching of 4,615 m of DN150 PVC and 460 m of DN225 PVC and included installation of approximately 118 pre-cast and in-situ access chambers.

In addition, day works crews installed the boundary kits’ associated works and were assisted by a utility crew that provided traffic control and non-destructive potholing for existing underground services. To date, the day works crews have installed approximately 700 boundary kits.

Major challenges

Installation of the sewer system reticulation works involved excavation and drilling of both road reserve and grass verge in residential streets, while construction of the gravity sewer system was carried out in road reserve, grass verge, bushland and private properties.

One of the major challenges associated with the project concerned minimising the impact of the construction’s works on the neighbouring World Heritage National Park, which included water catchment areas and hanging swamps. In order to do this, Codmah used HDD to minimise any visual impact.

In order to ensure that the water catchment was not contaminated or the hanging swamps drained, the company used large vacuum tanks to remove all construction fluids. The bores through the hanging swamps were also grouted with concrete, sealing the bore and preventing water run off.

Both components of the project involved some challenging excavation and HDD works because of the relative prominence of sandstone rock in the region. The Codmah crew overcame these conditions by employing specialist techniques, like the use of particular rock heads on the HDD equipment.

Safety, environmental and community issues were considered high priority factors in the project. The Codmah crew set the standard with their performance on the project by instituting customer ‘home plans’ for each individual property that outlined the layout and requirements of each homeowner, which allowed for a property-specific plan prior to the commencement of works. Additionally, an environmental work method statement was developed for each area of works, outlining the specific environmental needs for the area. The implementation of these plans was audited regularly.

Codmah has completed work on the project, with all pipe and associated works having recently been successfully being hydrostatic tested and inspected by CCTV before being handed over to the client. Codmah is currently completing extended works until September and is looking at continuing its relationship with the alliance for future works.

Throughout the process, Codmah has enjoyed an excellent relationship with the PSP partners, Blue Mountains Council and the local community. The company’s efforts in minimising and effectively managing construction risks and environmental impact have culminated in Codmah being recommended by the Upper Blue Mountains PSP to other arms of the PSP Alliance, with negotiations progressing regarding new contracts.