Background

High gas levels of hydrogen sulphide (H2S) were recorded at the Waste Water Treatment Plant in late 2023. Investigations were carried out as to the causes, source, and downstream Health & Safety (H&S) effects of the gas. Subsequently, several areas at the Waste Water Treatment Plant (WWTP) were also identified as requiring renewal and or significant maintenance works.

Overview

Contract 2665 – Wet Well Existing Upgrade
The existing wet well receiving industrial waste requires renewal and maintenance work. As the wet well is a critical part of the WWTP operation, long term shutdowns are not an option. A second wet well is being designed to future proof the WWTP for resilience, peak flows, maintenance, and the flow/discharge increases that will come with industrial expansion.

Contract 2666 – Wet Well New 2 Pump Stand-alone
The new wet well is expected to be approximately half the size of the existing wet well and will house 2 pumps, located beside the existing wet well. It will be designed to be free of personnel access, eliminating the H&S Confined Space, Gas Issues and specifically for operations and Operator Safety. When the new wet well is commissioned, the existing wet well can be drained, cleaned, and necessary remedial work to be performed safely and with minimal operational constraints on the plant.

Contract 2667 – Odour Bed Existing Media Replacement
The existing Odour Bed requires a total refurbishment being at the end of design life. The odour bed media had greatly decayed and broken down.

Contract 2669 – Ventilation Industrial
An investigation of the existing Industrial Ventilation (IV) system identified 12 issues with the existing IV. Upgrades will be undertaken.

Contract 2671 – Ventilation Amenities
An investigation of the existing Amenities Ventilation (AV) system by BECA and TDC identified that the system does not deliver the required minimum air change rate and needs upgrade. This reflects the increased wastewater flows and strength that the plant
now receives.

Contract 2672 – Ventilation Amenities Roof Access

Roof access to the existing AV services is below current codes/standards and will require upgrading.

Contract 2674 – Electrical Industrial & Contract 2675 – Electrical Controls

The existing equipment in the pictures below is now outdated and needs to be replaced.



Contract 2677 – Gas Detection & Monitoring
The existing Wet Well Gas Detection system is outdated and does not cover the types of gases nor the range and concentration of gases that required by current standards. This will be replaced.

Project Update

Contract 2665 – Wet Well Existing Upgrade
The existing wet well condition assessment has taken place using a drone. Deterioration inside the wet well walls and beam structures have been captured. The pump options and specifications have been reviewed and assessed to the current wet well conditions and
chemical coating requirements. Heat requirements from the inflows have also been taken into consideration. The existing pumps were replaced recently are fit for purpose so not requiring replacement.

Contract 2666 – Wet Well New 2 Pump Stand-Alone
Existing Plant services mark out has been investigated and located to ensure there is enough room for the new wet well construction and design preparation.



Contract 2667 – Odour Bed Existing Media Replacement
A renewed preliminary design will be completed in the next 2 to 3 weeks to enable detailed pricing and procurement.



Contract 2669 – Ventilation Industrial
A contractor is yet to be engaged for this work.

Contract 2671 – Ventilation Amenities
Currently the air conditioning units have been purchased and will be installed by the end of November 2024. We are also investigating the need for a building compliance consent as the new units will need to be consented as new structures will be installed on the roof of the building. Consent requirements to be confirmed.

Contract 2672 – Ventilation Amenities Roof Access
Currently we are investigating options for alternative roof access and possible upgrading the existing roof entry and installing new rails and walkways on the existing roof.

Contract 2674 – Electrical Industrial
The New Motor Control Centre (MCC)and Programme Logic Controller (PLC) work has commenced for this specialised work. Cables and units have been assessed and will require upgrades.

Contract 2675 – Electrical Controls
This project will be completed in conjunction with contract 2674 as the commissioning of the new controls, MCC and PLC will require a multiple stage commissioning approach as the plant cannot be switched off due to continuous inflows and operation requirements.

Contract 2677 – Gas Detection & Monitoring
A new system that is fit for purpose and future proofed is being priced and Materials and equipment to be installed into new and existing wet well.

Project Timeline

Contract 2665 – Wet Well Existing Upgrade
Initial investigative works have been carried out, upgrade will be carried out in later financial years as funding permits.

Contract 2666 – Wet Well New 2 Pump Stand-alone
Construction is due to start late October and is expected to be complete by the end of May 2025.

Contract 2667 – Odour Bed Existing Media Replacement
Construction has started and is due to be complete by the end of November 2024.

Contract 2669 – Ventilation Industrial
Construction is due to start in late August and be complete by the end of November 2024.

Contract 2671 – Ventilation Amenities
Construction has started and is expected to be complete by the end of November 2024.

Contract 2672 – Ventilation Amenities Roof Access
Construction has started and is expected to be complete by the end of November 2024.

Contract 2674 – Electrical Industrial
Construction has started and is expected to be complete by the end of December 2024.

Contract 2675 – Electrical Controls
Construction has started and is expected to be complete by the end of December 2024

Contract 2677 – Gas Detection & Monitoring
Construction is due to start in September and is expected to be complete by the end of May 2025.

Project Financials

• Total Budget: FY23/24 $1.4M FY24/25 $3.5M FY25/26 $1M FY26/27 $1M
• Total Projected Costs: $6,745,008.00
• Total Spend to Date: FY23/24 $730,008.00

Project Risks

Review the piping and instrumentation diagram and programme to ensure a safesite during each project stage.

Gas related issues, including the engagement with the companies that discharge tothe WWTP that their discharge is within the approved and agreed levels.

Planning to ensure Plant Operation is maintained.

Mitigating or eliminating the project related H&S, construction, and operational risk.