Date, time & venue 
2012-02-25;08:45 am to 12:30 pm;High Island Reservoir and gathering at Entrance of Romantic Hotel at Kowloon Tong

Gathering Point

Meet at front of Romantic Hotel at Kowloon Tong MTR Station (see map below).  Latecomers will NOT be entertained.

Highlight

The High Island Reservoir, located in Sai Kung Country Park, is the largest reservoir in Hong Kong with a capacity of 280 million cubic metres. The reservoir was formed by constructing two main rock dams rising some 64m above mean sea level at the eastern and western approaches of the channel.  Work began in 1971 and was completed in 1979. The reservoir occupies an area which was previously the Kwun Mun Channel (官門海峽) which separated High Island and the eastern end of the Sai Kung Peninsula. 

The reservoir was designed by Binnie & Partners as a part of the High Island Water Scheme which included pipeworks and other supporting infrastructure as well as the reservoir itself.  One of the main rock dams was built at the west of High Island connecting it with the Sai Kung Peninsula at Yuen Ng Fan (元五墳).  The other main dam was built at the Southeast of High Island, connecting it with the Sai Kung Peninsula near Po Pin Chau, a stack island.  Three smaller dams were also constructed in valleys around the reservoir.  Aqueducts totaling 5 miles in length were also constructed to transfer water from streams around Sai Kung Peninsula to the reservoir.

Attendees to the site visit will gain unique information on the reservoir safety inspection to the maintenance aspects of the dam and reservoir.

Rundown

8:45 -9:00        gather and board bus(see map attached)

9:00 – 10:00    bus travel to High Island Reservoir

10:00 – 11:15  walk the Reservoir (East Dam) + WSD presentation

11:15 – 12:00  walk the Reservoir (West Dam & Overflow Structure) + WSD presentation

12:00 – 12:30  distribute CPD certificates; back to Gathering Point

Safety Equipment

Attendees do not need to bring any Personal Safety Equipment.

Registration and Enquiry

The event is free of charge. The number of participants is limited to 25 on a first-come first-served basis. Please visit HKIE website http://cv.hkie.org.hk for online registration. The successful applicant would be confirmed on or before 18 February 2012. For enquiry, please contact Ir. C. S. Lam at Tel: 91527659

Report

By Ir Kate NG and Ir Warren CHAN

A technical site visit to High Island Reservoir was held on 25 Feb 2012. The representative, Ir Edmund. S L Li of the Water Suppliers Department briefed us the background of High Island Reservoir with a tour to the West Col Dam, a pumping station and the East Dam.

High Island Reservoir is the largest reservoir in Hong Kong consisting two major rock dams (East Dam & West Dam) rising 64m above mean sea level. The construction works of reservoir began in 1971 and completed in 1979 with cost of HK$1.35 billion.

The special facilities in the reservoir were introduced such as (i) Draw-off Tower which draws off water from reservoir by means of an intake tower of dry well type, and (ii) Bell-mouth Siphon Spillway which discharges overflow to a 6m dia. vertical shaft, then to a 5.5m dia. tunnel and finally into the sea shore at a flip bucket in the form of a ramped baffle wall.

For maintaining the stability of water dams, different kinds of monitoring system are carried out periodically to ensure their safety. The survey marker, inclinometer and inverted pendulum equipment are for monitoring the vertical and horizontal movement; while the drainage gallery with the V-notches outside the gallery entrances at toe of dam is for gauging the seepage.

Method of remedying the leakage problems of West Col Dam was explained. The rockfill with clay core embankment dam (300m long & 45m high) was founded on residual soil overlaying bedrock and leakage was found to reach 480 l/min when the reservoir filled for the first time in Sept 1983. As such, investigation works with boreholes were carried out for trial grouting and tracking tracers. After that, multi-rows of grout curtain using grout materials of OPC, superfine PC, ultrafine PC and chemical grout were installed along the dam. Monitoring of drainage discharges during the investigation & grouting works and preliminary & final impoundment tests were carried out. The leakage was finally reduced steadily to about 40% of original leakage during the first filling of reservoir, which was considered to be acceptable for the remedial works.

Throughout the site tour, we were able to gain better understanding about reservoir operation and maintenance in Hong Kong. On behalf of the Civil Division and participants, we thank Ir Edmund Li and his colleagues to lead us the reservoir visit with giving the introduction of reservoir maintenance safety.

Photos of the visit

Please visit photo album 20120225 High Island Reservoir