Common Utility Tunnel for Utility Services at Putrajaya, New Water Science and Technology: Supply Administrative Centre of Malaysia
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Common utility tunnel for utility services at Putrajaya, new Water Science and Technology: Supply administrative centre of Malaysia S.M. Adnan and T.K. Heng SMHB Sdn. Bhd., Consulting Engineers, 38, Jalan 1/76D, Desa Pandan, 55100 Kuala Lumpur, Malaysia (E-mail: [email protected]) Abstract With the requirement for utilities to be installed in a protected environment at Putrajaya, the new Administrative Centre for the Federal Government of Malaysia, a common utility tunnel has been developed, designed and is currently under construction. The common utility tunnel (CUT) complements the “No Dig” policy of Putrajaya and offers year-round access for inspection and maintenance of utilities laid inside the tunnel. The design of the CUT incorporates features for phased construction of the CUT and installation of utilities. The utilities to be housed inside the CUT are electrical power cables, water pipe, chilled water pipes, gas pipe, multimedia cables and telecommunication cables. This paper discusses the move behind Vol 3 No 1–2 pp 29–34 the implementation of the CUT and describes the planning and design of the CUT. This is the first time that an effort has been made in Malaysia to get all the utility providers to agree to have the various utilities in a common tunnel and also on cost-sharing of the capital and maintenance expenditure. Keywords Common utility tunnel; inspection; maintenance; year-round access Introduction Putrajaya, located about 50 km south of Kuala Lumpur, is being developed to be the new © 2003 IWA Publishing and the authors Administrative Centre for the Federal Government of Malaysia similar to Canberra, Australia, and Brasilia, Brazil. Located within the Multimedia Super Corridor, the develop- ment of Putrajaya marks a new chapter in the history of modern city planning in Malaysia. It is set to be a model garden city with sophisticated information network based on multi- media technology. The “No Dig” policy implemented in Putrajaya, has resulted in the development and implementation of a Common Utility Tunnel (CUT). The policy advocates no further dig- ging after development and imposes stringent conditions for further digging. The CUT is being implemented only on the Putrajaya Core Island which is a 460 hectare man-made island and when completed will be the cultural and commercial hub of Putrajaya and is the most high profile precinct of the new administrative centre. It covers Precinct 2, 3, 4 and 18 of the new township. The decision to implement the “No Dig” policy in Putrajaya and hence the implementa- tion of the CUT which is both cost effective and innovative was due to the following reasons: (a) to prevent/minimise open digging in busy street for initial and future laying and mainte- nance of utilities; (b) to minimise interruption and disturbance to the public particularly traffic; (c) to protect utilities from potential damage/interference due to future excavation; (d) to minimise utility reserves on either side of the road and resulted in more land that can be released for development. The utilities housed inside the CUT are electrical power cables, telecommunication cables, multimedia cables, gas pipes, water supply pipes and chilled water pipes. The cost of implementing and maintenance of the CUT is being shared between the Government and utility providers. 29 30 S.M. Adnan and T.K. Heng T.K. and Adnan S.M. Figure 1 CUT layout on Putrajaya Core Island Design of the common utility tunnel (CUT) The CUT on the core island as shown in Figure 1 comprises a 7.0 km primary CUT loop encircling the central boulevard and commercial district, secondary cross links and tertiary CUT and branches leading to main lot parcels in Precinct 2, 3 and 4 of the core island. The total length of the CUT on the core island is approximately 15.0 km. The primary loop is situated along low profile roads away from the central boulevard of the core island. This is to facilitate workmen and their vehicle on routine maintenance and inspection of the CUT. S.M. Adnan and T.K. Heng Numerous options have been developed for consideration together with utility providers before arriving at the final compact arrangement of the CUT. It is driven mainly by economic consideration and yet need to be practical enough to allow for installation and maintenance of the utilities inside the CUT. The adopted CUT configuration is an unsym- metrical twin box tunnel constructed 2.0 m below ground and within the specified road reserve as shown in Figure 2. The clearance of 2.0 m below ground is to meet landscape requirement and to allow for crossing of minor drains above the CUT. The larger compartment of the “CUT” is double-decked and houses the twin chilled water pipe in the lower deck, potable water supply pipe, fibre optic, telecommunication and multimedia cables in the upper deck. The other compartment houses only the electrical power supply cables up to 33 kV with gas pipeline in a separate sand-filled channel above. The gas pipeline is put in an external channel filled with sand and covered with precast concrete planks. In the larger compartment, removable galvanized mild steel grating sepa- rates the upper and lower deck and forms the mid level walkaway along the CUT. An I- beam fixed to the soffit of the roof serves as a “monorail” transportation system for transporting of pipes and equipments along the CUT. As shown in Figure 3, the CUT is constructed within the road reserve and therefore eliminates the requirement for the normally practiced utility reserve. It is a cast-in-situ reinforced concrete structure designed to BS 8007 for water tightness with expansion and contraction joints placed at designated locations. All joints are treated with rubber water- stop and water proof sealant. As an added precaution, water proofing compound is painted on the external surface before backfilling. Expansion joints are located at spacing of not more than 50.0 m with construction joints at every 10.0 m. Contraction joints are provided at every 10.0 m in treated soft ground to allow for the envisaged differential settlements. With consideration of shrinkage, CUT members are cast in alternate panels. Personnel access points for maintenance and inspection crew are provided at about 500 m interval. Entry to the personnel access is via an aboveground structure with steps leading into the CUT. It is wide enough for crews carrying hand tools to undertake routine maintenance and inspection works inside the CUT. For lowering pipes and bulky equipment, Construction Access points are provided at about 500 m interval. For this purpose the Construction Access has a top opening of 2.5 m × 15.0 m and has been successfully used for lowering the 800 mm and 600 mm diameter chilled water pipe and potable water pipe respectively. As the CUT follows the road profile there will be several low points inside the CUT. Drainage sumps with automatically operated submersible pumps are provided at desig- nated locations to cater for any possible ingress of ground water, cleaning water and initial minor leakages of water pipes. The junctions between the primary, secondary and tertiary CUTs are complicated struc- tures that have been designed to allow for weaving of utilities. Numerous discussions were held with various utility providers to arrive at an acceptable junction configurations. Each junction configuration is unique and has to be treated separately with detailed drawings prepared accordingly. Modified structures were also designed at points of entry and exit of trunk utilities. The point where the utilities leave the CUT and enter the parcel at the lot boundary is called Mini Utility Hub. Size and position of openings have been designed on 31 32 S.M. Adnan and T.K. Heng T.K. and Adnan S.M. Figure 2 Typical cross section of CUT Figure 3 CUT in 25 m road reserve 33 Heng T.K. and Adnan S.M. the end-wall and sealed-off with temporary end cap which can be easily removed for future connection. Generous spare outlets are provided as the demand for utilities on some parcels are still uncertain. There are two Tunnel Management System Local Action Centres on the Core Island to monitor the CUT. The information sent to the Local Action Centres will also be relayed to the main City Control Centre which monitors the overall Putrajaya infrastructure facilities. S.M. Adnan and T.K. Heng The CUT is lit by fluorescent tubes of the corrosion resistant type suitable for tunnel environment. Switching can be done locally or remote from the Local Control Centre via the Tunnel Management System. Emergency Lighting fixtures are provided to provide suf- ficient lighting for the personnel to exit in the event of power failure. General purpose switched socketed outlets are also provided at designated locations along the CUT for use by utility providers during maintenance. A ventilation system comprising exhaust air fans, sound attenuators and air intake points is installed along the tunnel to reduce humidity, temperature and to provide sufficient fresh air for personnel working in the tunnel. Multiple speed exhaust fans are used to cater for normal and emergency conditions. Although the fan can be operated manually it is also activated automatically upon detection of low oxygen level or high methane level inside the CUT. The ventilation system is also used as smoke spill system whereby upon detection of smoke the fans will be activated automatically. The CUT will be monitored continuously for the presence of methane and sufficiency of oxygen. Detectors are installed and will send alarms to the Local Central Centre via the Tunnel Management System. CCTV surveillance using fixed cameras at personnel and construction access points pro- vides images to the Local Control Centre.