Case study: Sentul City

Sentul City is a high-end estate developed by a private company. Located in a mountainside region, close to Mount Salak and Mount Mas, it is conveniently close to the toll road and is home to 8000 permanent residents who live and work in Jakarta or Bogor. It also functions as a resort, with approximately 1000 residents living in Jakarta during the week and using Sentul City as a weekend retreat. Nine villages are also located within the Sentul City area, and many local villagers are employed to farm the land banks. The city is projected to grow five-fold from its current area of 3020 hectares to cover an area of 15,000 hectares.

High-quality, sustainable and green living is an integral part of Sentul City’s development plan. The overall aspiration is to become a pioneering Global Green City embodying water-sensitive urban design (WSUD). Set in a hillside location, the development is surrounded by greenery from forests to agricultural land. The land banks for future development are currently farmed and house local villages. Despite the plans for high growth and expansion, Sentul City management aim to maintain green open space at 60 per cent, including blue open space. 

The vision is for the city to be green, eco-friendly and sustainable. More specifically, the sustainable city will focus upon three aspects; Agropolitan, Technopolis, and Aquapolitan. The key issues that Sentul City is now facing to become a more water-sensitive estate are: unstable soils and landslides; high stormwater runoff; limited water supply; and management of future growth.

Sentul City already incorporates a number of green or environmentally sustainable systems. Some have been implemented for reasons such as aesthetics but have the potential to be adapted to provide water treatment and retention functions. The initiatives include green roof and green wall implementation, green technology usage, V-drains, vegetated drains and artificial creeks, urban farming, retention lakes (situ) and development of water for recreation purposes. 

As the community is considered as an important factor in becoming a Water Sensitive City (WSC), the community of Sentul City should also be empowered to support the leapfrogging of Sentul City and Greater Bogor toward WSC through training, simulation and socialisation. In addition, the community should be involved in the drafting of regulations for Sentul City so that it gains a sense of belonging and a willingness to obey the regulations. 

Water supply is a critical issue. Currently, Sentul City is dependent on water resources supplied by the central water utility, PDAM. The supply is not sufficient to meet demand, especially in the dry season, so around 8000 permanent residents living in Sentul are facing water shortages. With this in mind, the development of a diversity of water supply options is urgently required. 

Private companies are also involved in water supply as the PDAM service does not provide coverage to the entire community. In particular, industry and hotels tend to use companies to supply them with water from deep wells. Although ground water is accessible in the area, in Sentul City households are prohibited from digging wells. 

Stormwater is drained from the city via a network of channels, largely open rectangular concrete drains of various sizes. These were originally constructed as an irrigation distribution network in the colonial times. Thus, they were not constructed for the purpose of drainage, leading to issues with a lack of connectivity within the network, inefficiency and a non-ideal drainage configuration. At small scales, people often construct their own drainage infrastructure and manage it themselves.

The drainage network also suffers from a high sediment and litter load. It carries untreated urban stormwater runoff and household greywater discharges. In terms of wastewater management, a treatment plant was constructed by Sentul City’s private management to service the community. However, the relatively small facility is currently not functioning. It is utilised for emergencies only and is only capable of treating a small proportion of wastewater (about 10 per cent). Instead, new houses have individual septic tanks and commercial buildings are required to construct their own wastewater treatment plants. For solid waste, roughly seven tonnes per day are currently generated.

The research team utilised several analysis tools, including community or stakeholder and site analysis tools, green technology solutions and water balance models.

Results and achievements

• Commercial opportunities have been realised through the innovative approach to water management within Sentul City. Water serves as a key feature of the Ah Poong Floating Market, while green walls provide notable aesthetic features at the Aston Hotel and Savana Hotel.
• The upmarket private development provides opportunities for individual households to shoulder the cost of system construction and maintenance.
• Green water treatment technologies can be a motivation for buyers, both private and commercial.
• Many of the existing systems provide scope for modification to provide water treatment and retention benefits. For example, the conversion of V-drains into swales and bioretention systems.
• The existing open space and greenery will facilitate future technology adoption. Unlike many parts of Bogor, land availability for systems is not a critical limitation.
• There is high potential for widespread technology adoption as part of the large future growth in Sentul City. If system design is incorporated into projects from the outset, it also greatly reduces costs relative to retrofit situations.
• Traditional preference and reliance on certain water sources (such as the PDAM supply, or also groundwater in other parts of Bogor) should not provide a barrier to the adoption of alternative water supplies (such as rainwater harvesting schemes) which will diversify supply and enhance resilience against future changes in supply. Community education, supporting research (such as demonstrating the water quality of roof runoff) and demonstration projects will help to promote the adoption of new water supply options.