Restoration of submerged stormwater pipeline

Overview 

Desilting Solutions, a specialist contractor in underwater dredging, partnered with the Brisbane City Council to address a critical infrastructure issue. The project focused on desilting a 160 m section of a submerged stormwater pipeline at the corner of Castlemaine St and Chippendall St in Milton, QLD, adjacent to Suncorp Stadium. This pipeline serves over 3,000 properties and plays a vital role in the flood resilience of the surrounding area.  

The project, executed between July 2023 and November 2023, required cleaning the pipeline to reinstate at least 95% of its design capacity. A remotely operated vehicle (ROV) and GEOTUBE^® technology were chosen to meet the unique challenges posed by the confined site footprint and public location. The successful completion improved flood resilience, benefitting both the client and the community. 

Challenge 

The desilting process involved unique challenges stemming from the project’s location and technical requirements. The site’s proximity to Suncorp Stadium posed logistical difficulties, especially during the Women’s Soccer World Cup, which increased public activity and scrutiny. Additionally, the pipeline remained fully submerged throughout the project, complicating traditional dredging approaches. 

The installation began with constructing a bunded area to contain the dewatered material. The ground was leveled to desired grades, and plastic sheeting was laid and welded to create a watertight enclosure. A GEOTUBE GT500D 183 174 B1P08 was placed within this bunded area to serve as the dewatering unit.  

The desilting process utilized an ROV deployed into the pipeline via a purpose-built manhole. This ROV tracked along the pipeline, agitating silt and sediment, which was pumped to a polymer dosing unit. This step ensured proper flocculation of fine particles before depositing the slurry into the GEOTUBE. The dewatering process allowed water to escape while retaining the solid material. Once the material was sufficiently dewatered, the GEOTUBE was cut open, and the spoil was loaded into trucks and disposed of at Fisherman’s Island at the Port of Brisbane. 

The confined footprint of the project site necessitated innovative solutions to manage space efficiently. Moreover, ensuring minimal disruption to the surrounding community during a high-profile event like the Women’s Soccer World Cup added complexity. Despite these challenges, no public complaints were recorded, and the GEOTUBE system emitted no odors during operation.  Another unique aspect was the always-submerged pipeline, which required specialized equipment and expertise to clean effectively.  

Solution

The success of this project relied on the strategic use of GEOTUBE technology and Solmax’s tailored approach to the challenges at hand. The GEOTUBE was selected for its capacity to fit within the confined site footprint while offering sufficient storage volume for the dewatered material.  GEOTUBE technology offers a reliable, space-efficient method for dewatering large volumes of dredged material. Its performance in this project was supported by careful polymer selection, determined through laboratory analysis by Geofabrics. The polymer ensured optimal flocculation of the suspended solids, maximizing dewatering efficiency.  Advantages of using GEOTUBE technology included: 

• A wide range of available sizes, enabling flexibility to adapt to site constraints. 

• Efficient dewatering capabilities that minimized water retention in the spoil. 

• Environmental compliance, as the retained material was safely disposed of without incidents. 

The GEOTUBE GT500D was the largest unit that could be accommodated on-site, making it the ideal choice for the project’s requirements.  The pipeline was restored to 97% of its design capacity, exceeding the specified target of 95%. The project was completed on time, under budget, and without any safety or environmental incidents, reflecting a commitment to excellence. These outcomes highlight the reliability of Solmax’s solutions and the technical expertise of Desilting Solutions.  The project underscored the importance of tailoring solutions to meet site-specific challenges. The use of GEOTUBE technology demonstrated its adaptability in confined spaces and its effectiveness in achieving high dewatering efficiency. Additionally, the collaboration with Geofabrics to determine the appropriate polymer highlighted the value of technical support in ensuring optimal product performance.