Contract No. PR/2023/17 - Rehabilitation and Replacement of Sewer and Stormwater Drain in
Mainland South (Package 4)
2024 - 2026
Before
After
Project Overview
Client
Drainage Services Department
Contract No.
PR/2023/17
Location
Mainland South, Hong Kong
Total Length
55.65 m
Pipe Diameters
150 mm – 300 mm
Completion
March 2026
This comprehensive rehabilitation package addressed ageing and defective sewers and stormwater drains across Mainland South by seamlessly integrating traditional open‑cut excavation with advanced trenchless pipe rehabilitation techniques – including precision coring and UV Cured‑In‑Place Pipe (CIPP) lining – to restore critical network features such as FWD4062582 and SWD4010713. The works were carefully planned to maximise structural renewal while minimising disruption in dense urban streetscapes.
Scope of Works & Work Procedures
1. Temporary Traffic Management & Flow Diversion: Approved TTA plans were implemented to ensure safe, efficient traffic flow around all work locations. Concurrently, temporary water diversions were set up to enable completely dry operations for the pipeline works.
2. Pre-Works CCTV Condition Survey: High-resolution visual inspections were conducted to accurately assess pipe conditions and confirm the most appropriate repair method. High-precision ROV tractors, center-aligned to the pipe axis (±10%), surveyed the lines at controlled speeds of 0.1–0.15m/s to generate MSCC/UTI CCEC 2022 compliant structural reports.
3. Mechanical Cleaning & Desilting: Heavily silted pipes were prepared for lining using high-pressure water jetting. Tailor-made mechanical scraper buckets and winching systems were deployed to extract hardened deposits efficiently without requiring man-entry.
4. Open-Cut Excavation & Manhole Modification: Severely deteriorated pipe sections were replaced by open-trench excavation, installing new pipes of matching or upgraded diameters. Where borehole space was insufficient for trenchless equipment, manhole walls were temporarily demolished. Steel-plate soil supports were secured via eye-bolts and hydraulic jacks, followed by full concrete and formwork restoration.
5. Trenchless Coring Installation: To navigate hard blockages, a CABEL CSN-6A Coring Machine jacked 273mm OD (250mm ID) pipes along a 4-8mm guiding wire. Once cleared, 600mm uPVC sections were jacked in to serve as a temporary host structure for the new lining.
6. Trenchless Pipe Rehabilitation (UV CIPP Lining): Where existing pipe conditions permitted, Cured-In-Place Pipe (CIPP) lining was utilized to create a jointless structural liner, avoiding full excavation. Factory-impregnated IMPREGLiners were secured, inflated, and held at working pressure for 10 minutes. An IMS Robotics UV 7800 unit then cured the liners, utilizing strict thermal monitoring to maintain laminate temperatures optimally between 80°C and 140°C.
7. Post-Installation Verification: All renewed pipes underwent a final video CCTV inspection and material sampling to verify structural integrity and ensure full compliance with DSD engineering standards.
Professional Highlights
Flexible use of open‑cut and trenchless methods to suit actual pipe condition on site
All work fully compliant with confined space safety regulations
Strict rodent control and waste management plans executed throughout the contract
Smart Site Safety System (SSSS) deployed to enhance on‑site monitoring
Completed on programme while maintaining pedestrian and vehicular access in busy urban areas
Contract No. PR/2023/16 - Rehabilitation and Replacement of Sewer and Stormwater Drain – Mainland South (Package 3)
2024 - 2025
Before
After
Project Overview
A hybrid rehabilitation programme restored seven critical sewer and stormwater drains across Sham Shui Po and Mongkok. Open‑cut replacement was used only where pipes had fully collapsed; all remaining sections received a structural CIPP liner installed from manhole to manhole, keeping road openings to a minimum in busy urban corridors.
Project Title
Rehabilitation and Replacement of Sewer and Stormwater Drain – Mainland South (Package 3)
Client
Drainage Services Department
Contract No.
PR/2023/16
Location
Yen Chow Street, Yuen Ngai Street and adjacent areas, Sham Shui Po / Mongkok
Pipe Diameters
150 mm – 300 mm
Total Length
95.35 m
Completion
December 2025
Key Techniques
1. Pre‑Works CCTV Survey
High‑resolution crawler surveys produced MSCC‑compliant defect reports, identifying which pipes required open‑cut replacement and which could be rehabilitated by lining alone.
2. Selective Open‑Cut Replacement
Where pipes had lost cross‑sectional integrity, short excavations were carried out under approved TTA. New uPVC/HDPE pipes were laid and connected to existing manholes, forming a sound host structure for the CIPP liner.
3. Flow Diversion & Cleaning
Live flows were temporarily diverted or plugged to provide dry working conditions. High‑pressure water jetting and mechanical cleaning removed silt and debris prior to lining.
4. Temporary Carrier Pipe
In some sections a corrugated spiral hose was jacked through the host pipe to act as a protective temporary carrier, ensuring a smooth, dimensionally stable substrate for the liner.
5. UV CIPP Lining
Factory‑impregnated IMPREGLiners® were inserted, inflated and cured using an IMS Robotics UV 7800 light train. A jointless, fully structural liner was created inside the existing pipe from manhole to manhole.
6. Post‑Rehabilitation Verification
Final CCTV inspection confirmed liner integrity. Lateral connections were reopened robotically where required, and complete as‑built records were delivered to the client.
Highlights
95 m of drains renewed with a hybrid approach that kept open‑cut works to the absolute minimum
CIPP lining restored full structural grade across diameters 150 mm – 300 mm
Dense urban utility environment managed with zero utility strikes
Full confined‑space compliance achieved with zero safety incidents
Programme completed on schedule, allowing early handover to the Drainage Services Department