Multi-purpose challenge

Built under a BOT contract, the San Roque multi-purpose project in the Philippines has entered commercial operation. The plant was built on an aggressive five-year schedule, and has added 345 MW to the Philippine national grid.

Robert Resch, P.E., Washington Group International, Inc.

The $1.2 billion San Roque multi-purpose project on the Agno River on the Island of Luzon in the Philippines was built to supply 345 MW of hydroelectric power to the Philippine National Power Corporation (NPC) grid, to help control flooding, provide water for irrigation year-round, and improve water quality. Commissioned by Philippine President Macapagal Arroyo and former President Ramos in Manila on May 29, 2003, San Roque represents a remarkable international engineering and construction response to site, logistics, and schedule challenges.

Located in a remote, largely undeveloped mountainous region, the project was privately developed by San Roque Power Corporation (SPRC), a special purpose company formed by Sithe Philippines Holdings Inc., Marubeni Corporation, and KPIC Singapore Pte Ltd., a subsidiary of Kansai Electric Power Company. NPC was responsible for constructing an 8 km-long, 230 kV transmission line to the site.

Upon completion, ownership of the dam, spillway and low-level outlet tunnel transferred to NPC. SPRC will own and operate the generating facilities for 25 years.

Figure 1. Aerial photo of the completed San Roque Multi-purpose project indicates the size of the massive project. From left to right, shows the 400 m-long spillway and 200 m-high earth and rockfill dam with the 1300 ha reservoir behind it and the switchyard below it (Photo courtesy of Washington Group International)
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Aggressive schedule

Through contracts with two of its subsidiaries totalling $705 million, Washington Group International provided engineering, procurement and construction services for the San Roque project. San Roque was built on an aggressive five-year schedule and achieved commercial operation on May 1, 2003.

Achieving this aggressive schedule was possible only through the design/build turnkey approach. An execution plan was developed during the period prior to the notice to proceed, and it served as the baseline approach for the life of the project. Washington Group engineers, designers, and procurement specialists in the USA worked closely with the company’s site construction organization to avoid schedule delays and mitigate the impacts from unforeseen events. The Washington Group engineering/construction team jointly and effectively resolved engineering and/or construction challenges. The design/build approach was particularly effective in dealing with the varying subsurface conditions, which were the responsibility of Washington Group. Having the design and construction performed by the same entity allowed the required design changes to be implemented with a minimum of delay.

The San Roque multi-purpose project, located on the Island of Luzon in the Philippines, was in development for nearly 20 years. It was first packaged in the late 1970s by the National Power Corporation (NPC), and its consultant, Electroconsult of Italy. NPC desired to take advantage of the Build-Operate-Transfer (BOT) contract format that was popular for independent power projects at the time. Development of the San Roque project did not follow a routine path, however. It would take many years until Sithe Energies assembled the complex financing structure needed to launch the project. In mid-1997, Sithe Energy USA invited Washington Group International to assist in finalizing the conceptual design for this major undertaking.

A substantial portion of the project cost was covered by a non-recourse financial model. It required a lump sum design-supply-build contract format with an extremely tight 60-month schedule. The contract was executed and the notice to proceed issued on March 6, 1998.

Challenging site

The 20 km2 San Roque site was remote, nearly an hour’s drive to the nearest city and virtually devoid of any infrastructure such as housing, power for construction, or potable water. Washington Group had to build about 25 km of access roads, plus a 22 MW power plant and a 13.8 kV construction power distribution system.

The project required a local work force of more than 5000 people and perhaps the largest fleet of heavy construction equipment employed in the Philippines at the time. A major effort involved creating a village for 150 management personnel with housing, dining facilities, commissary, infirmary, school, recreation facilities, laundry, water purification system, and sewage treatment facilities. The project also provided housing for up to 800 craft labourers who did not obtain local off-site housing. In essence, Washington Group had to build a small town to support the five-year construction programme.

Permanent plant equipment, heavy construction equipment and materials often had to be barged from ocean terminals to an area landing on the coast, then hauled to the site. Keeping the construction equipment available and operable was fundamental to keeping the project moving. At any given time, the project had on hand $8 million in spare parts. Planned maintenance and repairs took place seven days a week, 24 hours a day.

The aggressive schedule, coupled with the remoteness of the site, increased the project’s vulnerability to unforeseen delays. To address this concern, Washington Group created a construction infrastructure that maximized independence from external events. The 22 MW construction power plant and distribution system, along with a 1 893 000 litre (500 000 gallon) diesel fuel storage terminal basically eliminated all delays from utility power outages and delayed fuel deliveries during and after typhoons. The fuel facility was sized to store two week’s supply at peak usage.

Figure 2. Shown during construction from the erection bay, the San Roque powerhouse structure is six levels deep below ground level (Photo courtesy of Washington Group International)
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Key dam structures

San Roque’s signature structure is its 200 m-high, 1200 m-long main earth and rockfill dam, the 12th highest of its kind in the world. The gated concrete spillway, sized to handle the Probable Maximum Flood of 12 800 cms, is 400 m long by 100 m wide. Its ogee is approximately 170 m above its plunge pool elevation.

The San Roque reservoir, which has a surface area of 1300 ha, stores water for both power and irrigation. It was designed to improve water quality below the dam by trapping sediment above the dam.

Powerhouse and tunnels

The three river diversion tunnels, power tunnel and low-level outlet tunnel totalled more than 5.2 km in length. Various shafts were also provided at the power and low level tunnels. The largest shaft was the surge chamber, measuring 20 m in diameter by 115 m deep.

The horseshoe-shaped diversion tunnels varied in length from 779 m to 851 m. The two largest measured 10.4 m wide by 15 m high. The third tunnel measured 6 m by 6 m. Originally conceived as concrete lined conveyances, the existing rock properties suggested a more economical approach. Fiber-reinforced shotcrete was applied to the tunnel walls with the understanding that yearly inspections during the construction period following each rainy season would be conducted and necessary repairs implemented. In the worst-case scenario, concrete lining would be installed. The decision was a good one as confirmed by the very minimal repairs required over the duration of the project.

The power tunnel is 8.5 m in diameter and 1200 m long. The final section approaching the powerhouse is steel lined. A concrete surge shaft that measures 20 m in diameter and extends 100 m down from the ground surface to intersect the power tunnel protects the tunnel from water pressure surges produced by sudden unit shutdowns. The low-level outlet tunnel is 5.5 m in diameter and 1300 m long and is utilized for maintaining river flow during rare periods when power production is interrupted.

Figure 3. Each of the three Toshiba turbines at San Roque delivers 115 MW (Photo: Alfredo E. Belen, Jr.)
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Grouting and inspection galleries were also tunnelled under the core of the dam and into the left and right abutments. These galleries facilitated the fast-track construction schedule by permitting the grouting of the foundation under the core to continue while the dam was being constructed above them. They will enable the San Roque operators to inspect the dam for the life of the facility.

Powerhouse construction began in 2000. The powerhouse, excavated using shaft construction techniques, measures 28 m wide by 59 m long by 43 m deep. The powerhouse box required the removal of more than 70 000 m3 of material using conventional excavation and blasting to reach a depth of more than 50 m. The powerhouse box then required more than 25 000 m3 of concrete. Toshiba International supplied and installed the three 115 MW hydro units and associated equipment.

Water enters the plant from the reservoir through a concrete-lined power tunnel, which splits into three steel-lined penstocks directing flow into the three turbine-generators. The exiting water re-enters the Agno River through tailrace tunnels and continues downstream for irrigation. The units are controlled by a computer-based Allen Bradley control system which can be operated manually or automatically; locally or remotely. Man-Machine Interface (MMI) screens are provided in the plant control room for the operation and monitoring of the units.

Each of the three vertical hydraulic turbines in the powerhouse can be operated independently in ‘unit control mode’ or combined, in ‘plant control mode’. The control system design ensures that the three units are independent, and the failure of the controls of one unit does not affect the operation of the other two units. The plant can be operated manually, automatically, or remotely dispatched by NPC.

The site 230 kV switchyard converts San Roque electric output for long-distance transmission to the San Manuel substation and into the Philippine power grid.

Final test results

The San Roque test and start-up period began in November 2002, when NPC completed the transmission interconnection, and was concluded in February 2003 with outstanding results. The facility passed output and reliability guarantees with flying colours. A severe restriction on total water seepage from the reservoir was also achieved successfully.

Successful approach

Staff turnover is a common problem on international projects at remote sites. The high quality of living conditions at the San Roque project village and the challenging work were likely the dominant reasons that the project experienced almost no turnover in supervisory staff.

The San Roque project team adopted an informal ‘partnering’ approach to the work to build a climate of cooperation and efficiency. To resolve technical issues on the project, the project team also created a consulting panel of three recognized experts in the field of water resources and hydroelectric developments.

The panel reported directly to the owner. It consisted of one member from Washington Group’s senior staff, one from the owner’s engineering oversight firm and a third independent member selected by the first two. The panel generally held formal inspections and review meetings at the site on a quarterly basis, or at other times as dictated by project activities.

Besides reviewing all aspects of the design and construction techniques, the panel made itself available to respond to questions or issues presented to it by the owner, owner’s engineer and/or the contractor. The consulting panel provided prompt resolution of any technical issues.

Figure 4. The steel-lined, 8.2 m-diameter power tunnel during construction (Photo: Alfredo E. Belen, Jr.)
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Safety and security

Heavy civil construction work is inherently dangerous. The extensive tunnelling, fast-moving 100 ton dump trucks, 300 m high dam abutments, and 100 m deep shafts at San Roque presented challenges to the Washington Group safety manager and his staff. This was compounded by US and Far East cultural differences in the treatment of workers.

An educational consultant in Manila was hired to conduct cross-cultural training for US and Filipino supervisors and managers. This resulted in a marked improvement in understanding between the two cultures and a remarkable change in attitude with respect to safety. With the added motivation of project incentive gifts, handed out upon reaching various safety milestones to every individual employed on site including Washington Group, owner, consultant, and subcontractor personnel, San Roque achieved a remarkable nine million hours without a lost-time accident over a several month stretch. The new attitude towards safety produced the added benefit of improved productivity and reduced downtime for unscheduled equipment repairs.

Since the San Roque site covered more than 2000 ha, it was virtually impossible to cordon off the work site to achieve security. Washington Group’s security personnel were trained to be in a constant state of alertness and always ready to respond to any emergency. They coordinated with the local, regional, and national law enforcement agencies to provide on-site and off-site protection for all personnel, visitors, and equipment.

Environmental protection

Compliance with the conditions of the Environmental Impact Assessment and environmental permits for the San Roque project was required for all engineering and construction. Compliance parameters covered silt restrictions, noise limits, equipment emissions, dust control, accidental oil spills, reclamation, and reports generation, sewage treatment, garbage disposal, and other categories. An environmental inspection group was formed to educate, inspect, monitor compliance, report, mitigate, and interface with the Department of Environmental Natural Resources (DENR), the Philippine organization equivalent of the US Environmental Protection Agency (EPA). Compliance with all aspects of the environmental requirements was maintained throughout the construction.

Examples of Washington Group’s commitment to environmental protection included the revegetation of approximately 110 ha of land that had been cleared for borrow and construction operations; heavy construction equipment specified to US EPA emission standards; sound barrier walls along the earth and rock conveyors and crushing stations; settling ponds to capture construction-produced silt; sound attenuation construction for the temporary powerhouse; recycling programmes to reduce garbage disposal; continuous watering of haul roads to control airborne dust; and collection and storage of removed topsoil for reclamation at the completion of construction.

Any major project can benefit from being perceived as a positive force among the local population. San Roque Power Corporation and Washington Group implemented several programmes for the benefit of the local citizens as a way of promoting civic awareness and positive local support. SPRC embarked upon livelihood programmes for the local unemployed. Washington Group conducted book drives in the US for the benefit of local Philippine schools lacking recent textbooks of any kind. Washington Group also conducted monthly medical weekends or open clinics for towns surrounding the project.

Perhaps the most outstanding element of the good neighbour policy was the extensive labour-training programme developed for the purpose of maximizing the utilization of local labour while minimizing the use of imported supervision. Each expatriate supervisor was responsible for naming at least five Filipinos under his direction as candidates for advancement. These candidates received additional training, and many moved up into positions originally allocated to expatriates.

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