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Clearing up underground: An Atlas Copco Wagner Scooptram ST-7.5Z carries out its work in a tunnel at the San Roque project in the Philippines.

Dam project speeds ahead
to beat the typhoon season

RACE AGAINST
THE RAINS

A large fleet of Atlas Copco underground vehicles is winning high praise for its performance on a multi-purpose dam project in the Philippines.

The fleet played a vital role in putting the project back on schedule after precious time was lost last year when typhoons caused disastrous flooding at the site.

The 22 Atlas Copco Wagner trucks and loaders were temporarily diverted from their main task of loading and hauling blasted rock to the more urgent job of removing flood silt so tunnelling could continue. Now the fleet is working at top speed to make the site flood-proof before this year's typhoon season starts.

Thurlo Hooper, R.E.O.L.'s deputy site construction manager: "The high availability of the Atlas Copco Wagner equipment has helped us to make up the time lost from last year's setback."

Thurlo Hooper, Deputy Site Construction Manager for the US contractor Raytheon Ebasco Overseas Ltd. (R.E.O.L.), says: "We've got to have the main upstream cofferdam construction up to an initial height of 23 metres and complete two diversion tunnels before the summer rainy season starts. When the river rises, the high water will flow through the two tunnels - otherwise we could lose the cofferdam.

"The Wagner equipment has performed real well, and we're very happy with it. Its high availability has helped us to make up the time lost from last year's setback."

Vast reservoir

The USD 1.19 billion San Roque dam project is located on the River Agno in the Cordillera Mountains of Pangasinan province, about 250 km north of Manila, the Philippine capital.
The massive dam is believed to be the biggest in Asia and is the twelfth largest in the world. It will create a vast 14 km2 reservoir for recreation, provide downstream irrigation to 87 km2 of farmland and supply power to the national grid from the dam's integral 345MW hydro-electric power station.

About 45M m3 of graded and processed material will go into the 188 m-high main embankment, which has a crest length of around 1,100 m. R.E.O.L. is working two shifts around the clock, seven days a week, to build the huge embankment at the rate of 4,000 m3/h of material delivered by dump trucks.

But the top priority is to complete the remaining two flood diversion tunnels - the first and smallest of three tunnels was ready in March and diverted the river so that work on the upstream cofferdam could start.

The three diversion tunnels have been designed to accommodate a flood flow of 4,600 m3/sec. The two largest high-level tunnels are 16.5 m high, 11 m wide and horseshoe-shaped. They will each cater to flows up to 2,100 m3/sec. The remaining 400 m3/sec of flood water will go through the smallest low-level tunnel, which is 817 m long, 6m x 6m and also horseshoe-shaped. It will normally have a flow of about 120 m3/sec.

Cadillac of tunnelling

R.E.O.L.'s General Equipment Manager Don Johnson: "Atlas Copco Wagner vehicles are the Cadillacs of tunnelling, and we have what is probably the world's finest fleet at San Roque."

The Atlas Copco fleet comprises 22 versatile, underground, Scooptram loaders and Mine Trucks - the first in the Philippines. Don Johnson, R.E.O.L.'s general equipment manager, comments: "We evaluated the options and eventually went for Atlas Copco Wagner, based on good experiences with the equipment in the past and the fact that it was by far the best overall package. We bought everything brand-new and we have what is probably the finest Atlas Copco Wagner fleet in the world at San Roque.

"For the main tunnels, we went for six of the ST-7.5Z loaders matched by the same number of MT-436B mine trucks. These were supported by a further 10 of the smaller ST-2D units for use in the dam's grout gallery tunnels. These proved too small when the size of the tunnels was increased, so we've replaced six of them with the larger ST-3.5 units."

Mr Johnson says he would have no hesitation in buying the same equipment again, adding: "Wagner is undoubtedly the Cadillac of the tunnelling industry. Everyone on site is really happy with the exceptional availability of between 92-96% - about 13% better than the 85% guaranteed by Atlas Copco. It's an unheard-of and unreal availability figure - and I'm sure that the initial training by Atlas Copco has a lot to do with it."

He says that training and Atlas Copco Wagner's comprehensive preventative maintenance programme, which is part of the company's on-site full service package, is the key to the equipment's success.

Strict servicing

The full service contract was set up last summer by Atlas Copco Wagner in co-operation with the local subsidiary Atlas Copco (Philippines) Inc. The responsibility is now solely with the local company's Maintenance Supervisor Julius Sison, who looks after the workshops, a USD 2 million stock of spares and a team of 10 mechanics who work two, 12-hour shifts.

He says: "We service all 22 machines in strict accordance with Atlas Copco's recommendations. We also carry out scheduled oil sampling of all the main reservoirs every 150 hours, which helps to indicate any potential faults so we can repair them before any breakdowns and loss of production can happen."

R.E.O.L. started work at the site in April, 1998, and by the time the first and smaller low-level tunnel was finished at the end of February this year, the larger tunnels had progressed 1,740 m.

Tunnel Area Manager Kevin Miller: "Atlas Copco Wagner vehicles are top-of-the-line and the best available. I've been using them for more than 25 years - and I wouldn't have anything else."

"We initially worked all six faces at once, using the ST-7.5Z units to load the Mine Trucks in the top headings and load and haul out of the small tunnel to dump in the trucks outside the portal," explains Tunnel Area Manager Kevin Miller of Woodward Construction, the U.S.-based company which is supervising tunnel construction for R.E.O.L.

"We work two shifts round the clock and - depending on ground conditions and the supports, shotcrete and rockbolts required - achieve an average advance of about seven metres per day for each face.

"We try to get two four-metre pulls per day, each leaving a muck pile of around 500 cubic metres, which is cleared in about two hours by a couple of the Scooptram ST-7.5Z vehicles and two trucks. We use a third truck when the haul gets longer."

After drilling, blasting and mucking out, the exposed rock is sprayed with an initial 50-75 mm-thick layer of fibre-reinforced concrete in preparation for another Atlas Copco product - Super Swellex rock reinforcement bolts. The bolts, up to 4-m long, are strategically placed in the roof and walls of the headings before a second spraying of shotcrete achieves a smooth tunnel lining 350 mm thick.

Quality control

Swellex has been selected by the designer, Golder and Associated of Georgia, USA, as the regular pattern bolt. This hydraulically-expanded bolt can give immediate rock support and full column bond, and has an excellent quality control procedure during its installation.

These features are specially important when facing soft and unstable rock, as at San Roque. Moreover, in soft rock, reinforcement is a bottleneck in the excavation cycle - so the contractor was pleased with the opportunity to use a fast and trouble-free bolt like Swellex to speed up production.

The contractor has been removing the remaining 11 m wide, 8 m high benches in the two large tunnels - which are on schedule for completion before the start of the typhoon season.

On target

When the current tunnels are completed, the Atlas Copco Wagner fleet will be moved on to muck out two 1,500 m long tunnels at the site - a 7 m diameter irrigation tunnel and a 9 m diameter tunnel to the main powerhouse.

R.E.O.L. is on target to complete the project in 2001. San Roque Power Corporation will sell and supply electricity to the national grid for 25 years before transferring ownership to the Philippines National Power Corporation.