Tieri WWTP – Key Block Retaining Wall Repair

⁠⁠⁠ BACKGROUND/SCOPE

CHRC seeks to engage a suitably qualified contractor for the design and repair of an existing key block retaining wall, approximately 10 to 12 metres in length, and 1.5 to 1.6 metres in height, located at the Tieri Wastewater Treatment Plant.

The retaining wall has sustained damage during previous significant weather events, leading to sand washout between the key blocks. To restore structural integrity, the wall is to be assessed to determine if it has to be fully demolished and reconstructed, using the recovered key blocks. A compliant handrail is also to be installed along the top of the wall, if required.

Upon completion, the retaining wall must be certified by a suitably qualified engineer to confirm compliance with all relevant standards.

TECHNICAL/FUNCTIONAL REQUIREMENTS

Mandatory requirements

1. Compliance with Insurance requirements specified in Section 1, Part 4

2. Compliance with Conditions of Contract specified in Section 1, Part 3

3. Site briefing meeting attendance – 24 September 2025 @ 10am.

Buyer to describe requirements/scope of work

• Structural integrity assessment.

• Design of retaining wall and provision of RPEQ certified documentation.

• Demolish retaining wall and stack recovered blocks.

• Prepare site for reconstruction.

• Reconstruct retaining wall.

• Install handrail (if required).

• Provide as-built documentation.

• Reinstate site.

Buyer to insert Key Deliverables and Milestones (if applicable)

The Contractor will be required to provide the following deliverables:

• Present assessment outcome and recommendation to CHRC.

• Present design for CHRC review and approval.

• Mobilisation, establishment of site facilities, insurances, permits.

• Careful removal and stacking of existing key blocks for reuse.

• Foundation preparation (excavation, trimming, compaction, base course).

• Supply and installation of drainage system (geofabric, drainage aggregate, agricultural drain).

• Reconstruction of key block retaining wall with salvaged blocks.

• Supply and installation of compliant handrail along top of wall.

• Testing, certification, and provision of as-built documentation.

• Demobilisation and site reinstatement.

The following indicative milestones are expected:

• Milestone 1 – Project Commencement: Contract award, mobilisation, and provision of program of works.

• Milestone 2 – Design Submission: Delivery of design documentation for approval prior to commencement of site works.

• Milestone 3 – Site Preparation: Removal and stacking of key blocks, foundation preparation, and drainage installation.

• Milestone 4 – Wall Reconstruction: Rebuilding of retaining wall and installation of handrail.

• Milestone 5 – Certification: Submission of engineer’s certification and asbuilt documentation.

• Milestone 6 – Practical Completion: Final inspection and acceptance of works

Delivery address (if applicable): Tieri Wastewater Treatment Plant

The other evaluation criteria that will be used to evaluate offers are:

1. Capability and Experience

2. Ability to meet the timeframes

3. Cost and Value for Money