PROJECT COMPLETION REPORT
SV1BC1FN30 – Subcontract for Mechanical Installation Works
Installation of Permanent 1000 mm Diameter Air Recirculation Line
Core Drilling at Shaft DS/NB/2/1/1 – PS30 (Below Ground Level)
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- Project Overview
This report outlines the successful execution of core drilling works and installation of a permanent 1000 mm diameter air recirculation line between the vortex chamber and downstream chamber at PS30, as part of package SV1BC1FN30 – Subcontract for Mechanical Installation Works.
The scope involved creating a circular core opening between two existing underground shafts and installing a 1000 mm Ø GRP/HDPE air duct to facilitate continuous air recirculation and odour extraction within the pumping station system.
The works were executed in accordance with approved drawings titled:
“Coring Works and Installation of 1000mm Ø Concrete Duct at PS-30”
Drawing No.: CZ002-MET-OAM-0001
Project: Civil Rehabilitation Work at AR/01/IV
Scale: 1:50 / 1:25
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- Scope of Work
The scope included the following major activities:
• Setting out and verification of core opening location.
• Core drilling of a 1000 mm diameter circular opening through reinforced concrete wall between:
• Vortex Chamber
• Downstream Chamber
• Installation of permanent 1000 mm Ø air recirculation duct.
• Structural anchoring and fixing.
• Water sealing and joint treatment.
• Concrete reinstatement and finishing works.
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- Technical Description of Works
3.1 Location & Structural Details
• Work Area: Shaft DS/NB/2/1/1
• Level: Below Ground Level
• Structure Type:
• Precast reinforced concrete shaft segments
• Cast in-situ reinforced concrete wall
• 2100 mm ID precast rings to vortex structure
• Temporary 12000 mm ID shaft (as per drawing reference)
• GRP liner (7 mm / 10 mm as indicated in drawings)
• Waterproofing membrane / coal tar epoxy coat
All dimensions were verified on site prior to commencement.
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3.2 Core Drilling Works
A specialized heavy-duty diamond core drilling machine was mobilized to execute a 1000 mm diameter precision core opening through the reinforced concrete wall separating the two chambers.
Key execution details:
• Diameter: 1000 mm
• Method: Stitch core drilling for full circular precision
• Cutting through reinforced concrete (SRC 20 Concrete)
• Controlled cutting to avoid structural vibration impact
• Continuous monitoring to maintain alignment accuracy
• Core depth executed as per structural thickness indicated in drawings
All works were performed ensuring:
• Structural integrity preservation
• No damage to adjacent GRP lining
• Controlled debris management and safe disposal
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3.3 Duct Installation
After completion of the core opening, the permanent air recirculation duct was installed:
• Type: GRP Inspection Pipe / 1000Ø ID HDPE Odour Extraction Duct
• Diameter: 1000 mm ID
• Position: Between vortex chamber and downstream chamber
• Alignment: As per section and detail A (Scale 1:25)
Installation included:
• Precise positioning and leveling
• Anchoring using:
• HIT-RE 500-SD chemical anchors
• HIS-RN M16 or equivalent threaded rods
• Anchored length 200 mm
• Reinforcement integration (T16-250 bars as indicated)
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3.4 Sealing & Waterproofing
To ensure complete water tightness and structural durability, the following measures were implemented:
• Application of hydrophilic sealant at joint interfaces
• Installation of 250 mm PVC water stop where required
• In-situ GRP lamination at connection interface
• Application of waterproofing membrane / coal tar epoxy coat
• External joint sealing and surface finishing
All sealing materials were applied in accordance with manufacturer specifications and project technical standards.
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- Safety & Confined Space Controls
Given the below-ground shaft environment, strict confined space procedures were followed:
• Gas testing prior to entry
• Continuous ventilation system
• Breathing apparatus readiness
• Standby rescue personnel
• Permit to Work (PTW) compliance
• Mechanical lifting control for equipment
Zero incidents were recorded during execution.
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- Quality Control & Inspection
Quality assurance measures included:
• Verification of opening diameter (1000 mm ± tolerance)
• Alignment checks between both chambers
• Anchor pull-out verification
• Sealant inspection prior to backfilling
• Final visual and dimensional inspection
• Engineer approval prior to closing works
All works were executed in compliance with approved drawings and project specifications.
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- Completion Status
The coring works and installation of the 1000 mm Ø permanent air recirculation line at PS30 have been successfully completed.
The installed duct now provides:
• Continuous air recirculation
• Odour extraction pathway
• Structural integration with existing shaft system
• Long-term durability with full waterproof protection
The system is ready for mechanical operation and integration within the pumping station air management network.
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- Conclusion
The project was delivered with:
• High precision core drilling execution
• Professional mechanical installation
• Full structural and waterproof integration
• Compliance with safety and quality standards
• No structural compromise to existing assets
This report is submitted for:
• Project handover documentation
• Client approval
• Technical portfolio / website presentation
Temporary Flow Isolation
Prior to commencement of coring works, the station line was safely isolated using an inflatable rubber plug (balloon plug) to prevent airflow and potential backflow during execution.
The rubber plug was:
• Installed before starting the coring works
• Monitored throughout the activity
• Safely removed upon completion of installation and sealing works
This ensured safe and controlled working conditions inside the shaft.
