The Engineer, the Dam and the Canatuan Experience

International expertise makes TVIRD’s Sulphide Dam “world class”

Overseeing this green project is Engineer Shaun Persaud – a six-foot tall American of Middle Eastern descent. He works for Knight Piésold & Co, an international consulting firm of engineers and scientists providing engineering and environmental services for mining, power, water, transportation and construction industries worldwide. Knight Piesold was retained by TVIRD in 2008 to provide design and construction management services for the Sulphide Tailings Storage Facility.

As a part of the Denver, Colorado, USA office of Knight Piesold, Shaun made his first visit to Canatun in 2008 and has been returning ever since. Among his other projects and assignments at Knight Piesold, Canatuan – the Subanon homeland – has become his favorite destination.

Located within the ancestral domain of the Subanon tribe, the Sulphide Tailings Storage Facility is a key operations and environmental management component of the Canatuan mining operations. Consisting of an earth and rock dam to contain the tailings from the operations and an outflow spillway to maintain the Canatuan Creek streamflow, the project has been constructed in four stages. Stage 4 is under construction now and is scheduled to be completed in early 2012. Watching the project being built and providing design services, Shaun is well aware of the importance of “doing it right” to protect the environment and the people who have become his friends.

Engr. Shaun is well loved in Canatuan. He is friendly, humble and has sense of humor that sets an atmosphere of openness and mutual respect between him and all the Filipino TVIRD construction and engineering team members. Over the years he has developed a strong appreciation of the Filipino and Subanon cultures and enjoys the personal and professional interaction. The opportunity to pass on some of his technical knowledge and in turn learn from his Filipino counterparts has always been one of his most enjoyable activities.

However, not too many know that engineering was not his first career choice. When he was growing up, he dreamt of becoming an airline pilot so he could see the world.

Although he never became a pilot, he has fulfilled his dream of going places, thanks to his engineering profession. He has visited more than 15 countries, either for work or leisure, in the Americas, Europe and Asia. So when you ask him where he lives, he would reply, in jest, that he lives like a gypsy.

“When you cannot see me working in our head office in Denver, Colorado, I am somewhere else in the world. I might be overseeing a construction project in Alaska, in Mexico or in other countries of Asia, like the Philippines,” Engr. Shaun says.

In the Philippines, Engr. Shaun, along with a Filipino crew, is working hard to make the TVIRD Sulphide dam, which sits amid the lush greens of Canatuan Valley, well engineered and constructed to the highest quality to meet international standards. At the same time, they are ensuring that environmental protection is assured in the dam construction.

Stage 4 of the Sulphide dam and spillway is the final expansion. The dam is being raised from its current height of 70 meters to its maximum height of 85 meters. The completed dam and impoundment will have a total storage capacity to hold about 4.6 million cubic meters of water, sediment and tailings deposition. This will be more than enough storage for the remaining mine life.

In addition to raising the dam height, a final overflow spillway is being built to safely pass the streamflows of Canatuan Creek around the dam and back into Canatuan Creek downstream of the dam. This includes the normal daily streamflow of Canatuan Creek and the high streamflows resulting from less frequent flood events.

As explained by Engr. Shaun, the earth-fill dam that extends across the Canatuan Valley is constructed of locally sourced soil and rock. The materials are placed in specific locations within the dam to form four primary zones, with each zone performing a specific engineering function.

The outer zone of the dam provides erosion protection on the upstream face and is constructed from competent rock materials generated from the mining operations. Located immediately behind the rock fill zone, is a low permeability core zone constructed from extremely weathered overburden materials excavated from selected locations. This is the red clay seen throughout the Canatuan area. The purpose of this zone is to limit the seepage of water from the upstream impoundment into the internal portion of the dam structure.

Downstream of the core zone is sand and gravel drainage blanket and a network of pipes that intercepts and collects any seepage water within the dam and the abutments. The water is then conveyed to the downstream toe of the dam and released back into Canatuan Creek.

The final zone is composed of soil and rock fill materials which form the downstream structural shell of the dam. This zone supports the drainage blanket and core zone and adds to the strength and stability of the dam. The downstream face of the random fill zone is benched and rip-rapped with larger rocks and boulders for runoff control and erosion protection.

When asked how long the dam is expected to last, Engr. Shaun says that with proper maintenance dams can last forever. The operational life of the facility is a function of the available storage volume within the impoundment behind the dam. Once Stage 4 is completed the available volume will be sufficient for the remaining 1 to 2 years of mine life.

Working with Engr. Shaun to complete the Stage 4 expansion is the Civil Engineering Services (CES) Department headed by Engr. Ed Nercuit. The team is composed of 40 Filipino crew that use 11 earth-moving heavy equipment units and 20 dump trucks. There are also two Filipino quality control inspectors who regularly test the different zones to ensure the construction meets the specifications and standards set by Engr. Shaun and Knight Piesold.

Speaking to a group of visitors, Engr. Nercuit said, “I am a native son of Siocon, and my people have entrusted to me their health and safety, the nourishment of their farms and the cleanness of our water tributaries. I will not fail them.”

Both Engrs. Shaun and Nercuit are working round the clock to finish the final stage of the dam,. As explained by Engr. Shaun, when finished, the dam and spillway will be as good or better than the other dams he has worked on throughout his international assignments. He is proud to have been a part of this work and will fondly remember his time in Canatuan and his Filipino friends. (Joseph Arnel Deliverio)