Housing Department
Marine Mud Green Process Pioneer

Exemplary Services@Gov
2011

An innovation in marine mud treatment

Marine mud, excavated from reclaimed land during construction, is very difficult to use in reclamation or other construction projects due to its high water content and soft, bouncy texture and contamination. Marine mud, as a result, is usually dumped into landfills or marine dumping sites, adding costs to construction projects and the environment. Not surprisingly, the engineering sector sees marine mud as a headache.

However, a group of engineers from the Housing Department, who are known as "Marine Mud Green Process Pioneer", recently found a way to turn this otherwise useless material into a valuable resource.

Recycling marine mud for backfilling

While working on the Public Housing Development Project at Kai Tak Development Site, the Housing Department estimated that developing the area would excavate approximately 27,000 tons of marine mud from Site 1A alone. This large amount of marine mud was equivalent to the volume of the total solid waste dumped into all the landfills in Hong Kong for three days.

Faced with this large amount of marine mud, Housing Department engineers pondered, "How can marine mud be treated in a more environmental-friendly and economical way?" Working together during a team meeting, the engineers came up with an innovative solution to this problem. By mixing marine mud with sand and cement, the engineers found a way to increase the mud's strength and to stabilise the contaminants and heavy metals that may otherwise make the mud polluted. After going through this process, the strengthened marine mud can stand the same amount of force as ordinary soil and be able to use for backfilling at the Kai Tak site. This marine mud treatment process is more eco-friendly than dumping and can reduce the cost of transportation and purchasing normal backfilling materials.

Turning theory into practice

As in the research and development of any innovative technology, rigorous testing and verification processes had to be undertaken before the new treatment process was put into practice.

The project team conducted multiple studies on this new mud treatment process and found that implementing it would be feasible, said Ir John Pak, Chief Structural Engineer of the Housing Department. In order to promote the development of this technology, the project team worked out a set of new acceptance criteria for this new filling material, and then met tenderers on the Site 1A foundation contract to explain the new technology and created design and work provisions that required contractors to take part in related tests and use treated marine mud for backfilling on Site 1A.

During construction at Site 1A, the team worked closely with the contractor to identify the right mixture for marine mud, sand and cement, or, as they called it, the "magic formula". After completing comprehensive studies, trials and refinements, the engineers found the most cost-effective and environmental-friendly mixture that also complies with all quality requirements. By using a 16:3:1 ratio of mud, sand and cement, the contractor recycled all the marine mud and used it for in-situ backfilling at Site 1A without dumping to landfill sites.

This marine mud treatment technology is the first of its kind in Hong Kong and is the result of uninhibited innovation and a passion for protecting the environment. These "green pioneers" won the 2011 Environmental Paper Award from the Hong Kong Institution of Engineers. The Environmental Protection Department has also considered this successful technology as a good reference case for the engineering sector to recycle and reuse marine mud, instead of disposing the waste off site in the future.

The marine mud green treatment technology is the first of its kind in Hong Kong and is the result of the Housing Department's 'Marine Mud Green Process Pioneer.'
The marine mud green treatment technology is the first of its kind in Hong Kong and is the result of the Housing Department's "Marine Mud Green Process Pioneer".
Stockpiling marine mud from excavation.
Stockpiling marine mud from excavation.
Mixing marine mud with sand and cement.
Mixing marine mud with sand and cement.
Backfilling and compacting green-treated marine mud.
Backfilling and compacting green-treated marine mud.