Qatar’s Public Works Authority (Ashghal) has tendered the design-and-build contract for its treated sewage effluent (TSE) distribution system.

The deadline for proposals is 8 June.

This is the last construction package of the $2.7bn Inner Doha Resewerage Implementation Strategy (Idris) project.

The package has been issued as an open tender, as works will take advantage of existing TSE pipelines. Less than the originally planned 70 kilometres of pipelines will be required.

The bulk transfer system package has been delayed until after 2022.

Ashghal has selected contractors for three design-and-build contracts for main trunk sewers in the Idris deep sewerage system.

The award for the 45km of 3,500-millimetre and 4,000mm pipeline, divided into northern, central and southern sections, is expected to be announced soon. Construction work is scheduled to start on 1 June.

Two bids for the lateral trunk sewers have passed technical evaluation. An award is expected in the second quarter of 2015. The 65km of 400-2,400mm pipeline are split into three sections in Doha Central, Al-Wakrah and Mesaieed Industrial City.

The bid deadline for the terminal pump station, which represents about half the value of the project, was in April. The only pumping station on the scheme will have a capacity of 12 cubic metres a second and be located 65 metres underground.

It will pump sewage to the 500,000-cubic-metre-a-day New Doha South sewage treatment works. The client has also tendered the contract for the sewage treatment plant, which will be built under a 20-year design, build and operate deal covering 20 years

Post-contract consultancy services for the main trunk sewer and lateral trunk sewer packages are under evaluation. The construction supervision contracts for the pumping and wastewater treatment plant contracts will be issued shortly, followed by supervision on the TSE pipelines.

The project manager is US firm CH2M.