PETALING JAYA: The soil at the location of the Bukit Antarabangsa landslide, which occurred in December  2008, had shown signs of instability as early as January 2008.

According to the declassified “Final Landslide Investigation Report” on the Bukit Antarabangsa landslide of Dec 6, 2008, a geomorphologic map produced by the Ulu Klang Ampang Hazard Assessment Study carried out in late January 2008 revealed arcuate and alligator cracks on the road shoulder of Jalan Wangsa 9, depression on the road shoulder above the slope, gullies on the slope below some abandoned houses near the site and several failure scars on the slope.

The abandoned link house project by Superview Sdn Bhd is situated between Jalan Wangsa 9 at the crest of the landslide and Jalan Bukit Antarabangsa at the toe of the landslide. The project has been abandoned since 1985. The construction of the project was marred by slope failures and saw the collapse of two blocks of houses on Nov 8, 1985. Almost 23 years later, the Dec 6, 2008 Bukit Antarabangsa landslide took place at the same location of the two collapsed blocks.

G&P Geotechnics Sdn Bhd had also reported signs of distress in its geotechnical design report dated 2006.

The report stated that it was clear that the drainage system on the slope was in bad condition and the soil at the landslide location was creeping and showing signs of instability.

While water leakage from an active water pipe along the abandoned houses near the landslide site has been identified as the most probable trigger of the landslide that took five lives and destroyed 14 bungalows, the 17-member investigating team attributed the landslide to a combination of factors:

* Prolonged soil creep that widened existing cracks and opened new tension cracks;

* Loose soil from earth dumping on the slope during the development of the area;

* Poorly maintained/damaged system on the failed slope and its surroundings;

* Prolonged rainfall during the months of October and November; and

* Heavily leaking active water pipe along abandoned houses

The landslide can be classified as a deep-seated slide, which is generally caused by high-pore water pressure, the report stated.

The 78-page Bukit Antarabangsa landslide investigation report was prepared by a committee led by the Public Works Department’s Slope Engineering Branch director Datuk Dr Ashaari Mohamad.

The committee interviewed 21 eyewitnesses for accounts of the events leading to the landslide and the history of the site.

The committee also made several recommendations in the report to prevent a reoccurrence of similar landslides in future:

* Undertake detailed inspection and assessment of slopes with signs of distress. Areas with prolonged soil creep must be inspected regularly and preventive works must be immediately undertaken;

* All the water and sewer utilities on slopes should be inspected periodically for leakage and damage;

* Repair and upgrade damaged and undersised drains within the vicinity of Bukit Antarabangsa;

* Install subsoil drains at areas where water seepage and high ground water table are located;

* Identify areas with similar non-compacted filled/dumped ground;

* Undertake instrumentation monitoring as an early warning system at high-risk areas;

* All water pipes adjacent to slopes shall be exposed;

* Ensure all hillside developments strictly follow the development guidelines of the local authorities.

An officer from Ampang Jaya Municipal Council (MPAJ) told that 50 copies of the report is available for sale today (Dec 8) at the council’s office at Pandah Indah, based on a first-come first-served basis. The report priced at RM80 per copy contains two volumes and a summary. The report was declassified by the Federal Government on Dec 4.

Volume 1 features the main report while Volume 2 consists of appendices of geomorphologic maps and data obtained from the Ulu Klang slope assessment study (before the failure), authority letters and witnesses accounts summary, aerial photographs, detailed drainage, water reticulation plan and sewerage plan, geological mapping, and slope stability analyses among others. Volume 1 and 2 are in English while the summary is in Bahasa Malaysia.

Every report comes with a serial number and the reason for the limited copies is to enable MPAJ to track the number of copies sold and to know who are buying them, explained the officer. Once all the copies are sold, further copies would be made available. Members of the public can register themselves at the MPAJ counter and they will be notified once the next batch is ready for purchase.

At press time, a total of 36 copies of the report have been sold since MPAJ’s counters opened at 8am on Dec 8. Those who bought the report included members of the media and government agencies while less than 10 copies were sold to private individuals. A local developer bought 10 copies, said the officer.