Vol 20 No 2 (10-2010)
Development at Anderson Road-Site Formation and Associated Infrastructure Work


The Development at Anderson Road - site formation and infrastructure project

Background

To meet the long-term public housing demand, the government has identified a 58 hectares site between Anderson Road and Sau Mau Ping Road for development of public housing, schools, district open spaces and related government, institution and community facilities.

The proposed development, covered by the Kwun Tong (North) Outline Zoning Plan, comprises about 10 hectares of land zoned as "Residential (Group A)" for the proposed public housing development, about 15 hectares of land zoned as "Green Belt", about 5 hectares of land zoned as "Open Space" for recreational uses, about 5 hectares of land zoned as "GIC" for various Government, institution or community facilities mainly include primary and secondary schools to satisfy the needs of local residents and those in the nearby districts and about 10 hectares of land for road use.

Scope

The public housing development to accommodate a population of about 48,000 by the Housing Authority is planned to complete in stages for population intake in 2015 and 2016 respectively. Before developing housing units, related site formation and associated infrastructure works have to be carried out in advance. The Development at Anderson Road - site formation and infrastructure project is a large scale multi-disciplinary project commissioned by the Civil Engineering and Development Department (CEDD) for forming platforms and construction of the associated infrastructure works. Ove Arup and Partners Hong Kong Ltd is the consulting engineer appointed by CEDD to carry out the detailed design and supervision of the constructions works. Upon completion of the detailed design, tenders were invited in 2007 and construction contract no. CV/2007/03 of about $2 billion was awarded to the China State-Construction Engineering (Hong Kong) Ltd in January 2008.

To match with the public housing development programme, land platforms will be formed from 2011 to 2013 in stages for handing over to the Housing Authority for building works. The associated infrastructure works will be completed by end-2014 to tie-in with the population intake.

Project's Major Works:

The project mainly comprises:-

(1)Formation of about 20 hectares of platforms with construction of related slope works and retaining walls;

(2)Road works of about 4.7 km in length, including related footpath and junction improvement works;

(3)Construction of vehicular bridges, footbridges and pedestrian subway;

(4)Construction of storm water drainage system including an underground storm water storage tank, sewerage system and water mains;

(5)Landscape works; and

(6)Environmental impact mitigation measures and environmental monitoring and audit.

There are four temples within the site that are affected by the site formation works and have to be cleared for the development. In view of the long existence of the temples and the support from the community, the Government reached an agreement with the temple operators that the Government will form a site at the junction of Po Lam Road and Sau Mau Ping Road and the operators will relocate the temples to the new site.

The site formation works will generate about 5.5 million cubic metres of surplus construction and demolition materials of which about 2 million cubic metres of rock will be excavated by blasting. Some of the excavated rock will be delivered to the adjacent Anderson Road Quarry for recycling and the rest will together with other surplus excavated material be delivered by dump trucks to a temporary barging point set up at the former Kai Tak runway for disposal by barges. In order to minimize impact to the public, dump trucks can only haul within non-peak hours. The time of blasting is also constrained to be less than 4 days per week excluding Saturday, Sunday and Public Holidays.

Since the project site is close to residential estates and schools, a Resident Liaison Group (RLG) is set up to maintain close communication with the local residents, District Council members and the local schools. There is also a 24-hour hotline for public enquires, plus a project website to provide updated information on works progress, environmental and traffic issues to the public.

Construction

The project site is complicated in geological structure. Extensive excavation and slope improvement works are necessary for forming the platforms. The soft ground is excavated using conventional backhoe type hydraulic excavators. Rock will be excavated mainly by blasting. Rock crushing plant or backhoe mounted hydraulic breakers will be used to break the resulting rocks into permissible size afterwards. Extensive soil nailing is carried out to reinforce soil slopes and reinforced earth technology is being used for several very large retaining structures.The highest one reaches 40 m., which on completion will be one of the highest of its type in Hong Kong.

The benefits of choosing these construction methods and machinery are that they can minimize the disturbance to the nearby residents and road users. Blasting under careful control has proven to be less disturbance and acceptable to the nearby residents as few complaints are received. On the other hand, soil nailing allows steep soil cut slopes to be formed thus maximizing the platform area. Reinforced earth retaining walls maximize the use of on-site materials and reduce transportation of bulk materials.

Blasting

The total blasting volume involved in the project is about 2 million cubic meters of rock. About 2,500 cubic meters of rock are blasted per day.

With a view to minimizing noise impact to the nearby residents, two silenced drilling rigs are deployed for drilling blast holes in surface open blasting works, resulting in a maximum reduction of 10 dBL noise as compared with ordinary drilling rigs. A team of professional supervisory staff is stationed full time on site to advise on blasting-related geological issues. Before blasting, the contractor will identify the blasting area first and the geological features of the rock are then checked by the Resident Geologist (RG). Afterwards, Resident Blasting Supervisor (RBS) will decide whether the rock is suitable for blasting. If required, laser profiling will be adopted to check for defective front row burden. If adverse geological conditions are spotted, such as weak seams, sheeting joints in rock, core stones and boulders, an amended blasting design is needed, for example, one with less amount of explosive involved.

Afterwards, the blasting proposal is submitted to Engineer's Representative (ER) to check the potential intensity and vibration of the blast and decide if any unfavorable effect is going to inflict on the critical sensitive areas like road utilities and slope features. After the proposal, including the blasting procedures and necessary protective measures, is examined carefully, drilling of blast holes and installation of protective devices, such as blast cages, blasting mats and vertical screens will then be carried out according to the amended blasting design.

Three 80-tonnes crawler mounted mobile cranes are employed for transporting the protective measures to three specific blasting areas when necessary, since the maximum plan distance of the whole site is more than 2 km. On the blast day, explosives are delivered by Mines Division of CEDD from the Government Explosive Depot, and arrive on site at noon. Shotfirers will charge the explosives and connect the detonators according to the carefully designed blast plan. Final check on the protective measures by the RBS will be carried out before the actual blast, plus the installation of seismographs to monitor vibration at critical areas, air-overpressure monitoring and road closure are also carried out for safety ground prior to the actual blast if required.

Supervisory Measures

Due to the proximity of the project site to the residential estates, plus the tight project time frame, the following supervisory measures are carried out:

- Blasting works are limited to a maximum of 4 days per week (no blasting work on Saturday, Sunday and Public Holidays)

- Two to three blastings will be carried out concurrently within short period of time to minimize disturbance

- The weekly blasting schedule will be sent to the Estate Management Office one week in advance (including the time and locations)

- If necessary, verbal confirmation on the blasting time will be sent to the Estate Management Office by phone in the morning of the blasting day

- Siren is sounded before each blast.

- Blasting time is preferred to be around 2:30pm to avoid being in conflict with the off-school hours.

- No blasting will be carried out during school examination period.

- The permitted periods for haulage are restricted within 10:00 and 16:00 hours to avoid inducing traffic impact during peak hours.

Progress and Conclusion

Site formation and construction of infrastructure commenced on 31 January 2008 for completion in end-2014. Progress was satisfactory as of today. Upon completion in phases, the sites will be handed over to the Housing Authority in stages for the development of public housing to meet the long term public housing demand.


Courtesy acknowledgement:
Civil Engineering and Development Department
The Government of the Hong Kong SAR
for the information and pictures provided