The government has announced plans for a HK$678 million flood abatement program, to increase flood protection in some of Hong Kong Island's most vulnerable area. Assistant Director of Drainage Services Chan Kin-kwong said the project is necessary to ensure that flood-prone areas are well protected even in the face of the worst storm in half a century. During historical heavy rainfall periods in August 2000, April 2006 and June 2008, severe flooding occurred in Happy Valley and adjacent areas.

The project will be constructed in two phases, the first of which is scheduled for completion in early 2015, and the second by early 2018.

An underground storm-water storage tank will be built beneath the Happy Valley racecourse to alleviate flooding in the nearby low-lying areas. Chan said the tank will store water from upstream, thus to reduce the volume of water being spilled into the lower drainage areas.

The storage tank, with a 60,000 cubic meters capacity - equivalent to 24 standard swimming pools - will store water temporarily during peak rainfalls. Chan said, on completion, the storage tank will be able to cope with downpours exceeding 130 millimeters per hour - an international standard. He noted that Hong Kong issues a few black rainstorm warnings a year, when rainfall exceeds 70 millimeters an hour.

Chan, however, admitted that finding a site to build the tank was not easy, since the surrounding area is densely-populated and congested with underground utilities.The only option was to seek a location beneath government facilities.

Luk Wai-hung, chief engineer of Drainage Services, vowed to minimize serious disruption to the public during construction, adding that jogging tracks and the Jockey Club's racing schedule will remain normal.

The project earned an International Water Association Project Innovation Award in July.

The special design is a movable crest weir system, together with real-time monitoring of water and tidal levels. With data feedback, the storage tank can be monitored and its volume can be adjusted to save power and construction costs.

The Drainage Services Department has adopted a new engineering contract (NEC) to carry out the mega project, saying the NEC assures that cost effectiveness and timely completion can be achieved through mutual trust and collaboration. Both the government and the contractor will share risks, savings and shoulder additional costs.

"By using the old forms of contracts, we normally see projects being delayed or over the budget and the contracting parties often looking at the matter as an adversarial issue," remarked Wai Chi-sing, permanent secretary for development (works). "As construction costs keep going up, I hope the NEC projects will help increase effectiveness and control budgets."

The Happy Valley storm-water storage tank is the biggest NEC scheme thus far. Wai said the government will commence some 20 construction projects amounting to HK$8 billion over the next three years.

The government has also has inaugurated one other major flood prevention measure. The Hong Kong West Drainage Tunnel, designed to intercept 40 percent of rainfall upstream in the mid-levels, was completed last month. Meanwhile work is still underway on upgrading of pipes downstream in Wan Chai.

mingyeung@chinadailyhk.com

(HK Edition 09/06/2012 page1)