Drainage & Sewage

-AT Tse Pui Hei

Keywords: Rainwater Interception, Illegal Drainage, Harbour Sewage Treatment



0. Drainage System in Kwai Chung


The Drainage System in Kwai Chung components: the upstream Tsuen Wan Drainage Tunnel, the downstream underground drainage System, and the coastal Preliminary treatment Works at Ramblers Channel. 



1. Rainwater Interception

The Tsuen Wan Drainage Channel is a draining strategy to intercept hillside rainwater from the upstream hillside area to prevent flooding in the downstream Kwai Chung urban district. The draining speed of the Drainage Tunnel is 223m^3 per second, which means it is able to drain a swimming pool amount of rainwater within 11 seconds. There are a total of 3 rainwater intakes along the Drainage Tunnel and the location also considered the affect acting on the local residents since Kwai Chung consists of 500,000 citizens. Such construction was also well known as a sustainable and long term strategy of the Drainage Department in 2010s.





2. Underground Drainage System


The underground Drainage system in Kwai Chung was built following the housing project in the 1970s. The complicated underground system consists of complex land lease ownership and is not capable of facing increasing rain water challenges. In light of  the heavy traffic on the surface level, excavation of underground drainage seems expensive and not preferred.

The most serious issue concerning urban drainage is the 1. Illegal drainage connection and the lack of drainage in the Alley area.


2.1 Illegal Drainage Connection


Till the statistics in 2019, there are a total of 16 drainage mismatches of sewage and rainwater pipes. Since the land lease constraints limited the action of government departments, drainage channels are being contaminated and emitted directly towards the ramblers without any treatments. Under such circumstances the sewage treatment is not able to maximize its purifying ability and as a result water contamination can be observed along the coast.

2.2 Missing drainage in Alley area


It is remarkable that Kwai Chung consists of a wide range of industrial buildings, while the alley area is supposingly as public spaces. The lamentable fact is, such alley areas lack sewage drainage nor collection points. This leads to the accumulation of waste and undesirable scent and causes the problem of mosquitoes. Indeed the mosquitoes are also caused by the illeagal dumping of certain owners, yet the lack of drainage in certain areas catalyzed the problem of bad public health.


3. Harbour Area Treatment Scheme HATS



The Kwai Chung Preliminary Treatment Works is one of the main components of the Harbour Area Treatment Scheme (HATS) designed by the Hong Kong government to improve the overall water quality of the Victoria harbour. Sewage collected from underground drainage pipes would be purified in the facilities and sent to the Secondary Treatment facilities in Stonecutters Island. Since 1995. The most obvious achievement of the Treatment Works is to reduce the levels of Escherichia coli bacteria (E.Coli) to 1/10 of the original level. 


4. Opportunities and Constraints

As mentioned in the system above, we can notify that the current drainage system is sufficient yet not able to solve specific problems like illegal disposal and bad public health. Since drainage is an overall issue among the site, improving drainage systems are believed to catalyze the overall quality of life of residents.


The opportunities of drainage come from developing the waste collection industry, as well as utilizing flyover bottoms and green morphologies since the area consist of blank spaces and involve draining potentials. Meanwhile, hiring local unemployed population and improving heat island microclimate are also feasible opportunities.


Meanwhile the main constraints would be the complicated human activities in every zones, as well as the intensive traffic, complicated land lease ownership and uneven land use distribution across Kwai Chung may largely constraint the development of construction and development work.



1Drainage Service Department(2000).Kwai Chung Sewage Screen Plant. Retrieved from

2Drainage Service Department(2005). Agreement No. CE 80/2001(DS) Drainage Improvement in Tsuen Wan and Kwai Chung – Tsuen Wan Drainage Tunnel Environmental Impact Assessment (Revised Final). Retrieved from

3Water Service Department.(2019)Sustainability and Conservation report 2018/19. Retrieved from