Prolonged dry weather and extreme precipitation require a different kind of stormwater management. RCE examines how Hong Kong is working to deal with low flow conditions and tackle water pollution.
The monsoon season is well known in Hong Kong and its storm water systems are designed to accommodate it. But managing the pollution caused by light rains, known as low flows, between these periods has proven more difficult.
Work is underway to build a series of Dry Weather Flow Interceptors (DWFIs) to deal with the problem and improve water quality around the island.
Courses for other cities
Using DWFIs is a new approach underway in Hong Kong and China, but it is an approach that developed cities around the world could learn from as they work to mitigate the effects of climate change. . Ultimately, Hong Kong aims to install 11 priority next-generation DWFIs.
The delivery of the EDWF network by the Hong Kong government’s Drainage Services Department has shown that it is not the engineering design that is the difficult aspect. Gaining public acceptance can be no longer an obstacle.
Binnies Hong Kong was recently appointed to undertake engineering consultancy work for the latest DWFI project, located in Shau Kei Wan on the east side of Hong Kong Island overlooking Victoria Harbor.
This latest program – which is part of the new generation of EDW – aims to improve the environmental quality of the coastal areas of Victoria Harbor, in line with Binnies recommendations from a four-year strategic feasibility study that explored the means to further improve the environmental quality of the port’s coastline. waters.
Binnies has completed two previous first generation DWFI projects and is working on three other similar next generation DWFI projects on the Hong Kong Island and Kowloon sides of the port. He plans to put the lessons learned into the Shau Kei Wan project.
The first generation DWFIs intercept and divert the flow of dry weather from the stormwater collection system to the sewage system which ultimately treats it in wastewater treatment plants.
The next-generation scheme developed by Binnies involves intercepting the flow of dry weather from the stormwater collection system at or near its outlet to the port and filtering it on site in a dedicated “filter station” for subsequent discharge. In the harbour. This approach will help preserve valuable capacity in the deep tunnel-based port area treatment system that is dedicated to the collection and treatment of wastewater from both sides of the port.
Binnies Hong Kong Managing Director Andy Kwok said there is a wide range of sources of pollution in dry weather, including poor connections of infective sewers to stormwater drainage systems, especially in more areas. old. There are also surface pollutants from multiple urban activities.
During prolonged hot and dry periods, the dry weather flow from the outlets of drainage culverts is a source of pollution along the waterfront. This is a significant concern due to government initiatives to improve the port facade on both sides and to make it more accessible to the public.
Binnies Hong Kong’s job is to assess filter technology, undertake design, assist with procurement, and oversee construction and commissioning.
The design philosophy adopted for the DWFI is to place as many plant parts and equipment underground as possible.
“The emphasis is on co-use with a high-end open waterfront space and it will be finished with a high level of artistic and architectural design to enhance the overall value proposition of the project,” Kwok said.
“It is our wish to create a beautiful open space in the form of a park or a promenade so that people are not aware of what is below when the work is finished.”
Despite the site’s increased amenity value upon completion, Kwok says there is often competition for land use and resistance from local communities to have a DWFI at a waterfront site. .
It is difficult to find a suitable location for DWFIs due to pressure on land space and the high cost of land in Hong Kong
“Each site presents unique obstacles and design elements are essential to gain acceptance,” he says.
Kwok says the work is still in its early stages and the focus is on the types of filtering technology that will be used at Shau Kei Wan DWFI.
He adds that pilot projects using models to evaluate the systems that could be used are underway, as are cost and efficiency evaluations.
The types of filters currently under consideration include mechanical meshes and cloths.
Kwok says he expects initial work, which began this spring, to take another 14 months, after which a planning request will be submitted. He predicts – everything is going well with planning – that construction could start in 2024 and be completed in two to three years.
“It is difficult to find a suitable location for DWFIs due to pressure on land space and the high cost of land in Hong Kong,” Kwok explains. “Even when a site has been found, it is also difficult to build the necessary plant within the available footprint.”
He adds that the main risks to the project are local objections and regulatory approvals rather than the engineering itself. Nonetheless, despite the challenges and the financial cost, it is clear that the Hong Kong government is committed to making this environmental improvement.
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