Mining company belies Zambo dam collapse

A Mines and Geosciences Bureau (MGB) inspection team has officially verified that there is no truth to reports that there has been a collapse of the sulphide dam currently under construction at Canatuan – site of TVI Resource Development Philippines  Inc.’s (TVIRD) gold-copper project – in Siocon, Zamboanga del Norte, the mining company said in a statement yesterday.  

The MGB-Region 9 team, according to TVIRD, also validated the company’s earlier statement that exceptionally strong rains that lasted for about 12 hours over Canatuan last July 10 and 11 “caused erosion at the downstream portion of the construction area and the temporary spillway section of the unfinished sulphide dam.”

The TVIRD is building the sulphide dam to impound tailings of copper-zinc concentrates to be produced around the second quarter of 2008.

Members of the DIOPIM Committee on Mining Issues – a church-based anti-mining network that disseminated the reports that one of TVIRD’s dams allegedly collapsed last April and again last July – accompanied the MGB-Region 9 inspection team in its Canatuan ocular inspection last July 25 to 27, the company said.

The TVIRD quoted the verification report filed by MGB-Region 9 engineer Leo Ver as stating that heavy rains “caused the impounded large volume of rainwater from the dam to swell.”

The report added that soil erosion generated an unusual volume of earth materials coming from the sulphide dam construction site, “causing fear and alarm (among) residents downstream (who) concluded that the dam had collapsed,” it added.

Jay Nelson, TVIRD vice president for environment and civil works, said, “The materials that were eroded as a result of the July 10 and 11 downpour were ‘random fill’ materials placed for the future construction activity planned for the dam.”  

“The erosion did not in any way affect the structural integrity of the current construction stage of the dam, nor did it cause the release of toxic waste materials,” he added.

“During the time of the rainfall, the downstream slope of the construction area was being readied for rock riprap placement in anticipation of the heavy rainfall season of August, September and October based on site-specific rainfall data and observations over the past four years,” Nelson continued.  

“However, the work had not been completed in time for this early storm, resulting in erosion damage,” he said.

The TVIRD said it has already submitted to MGB-Region 9 an erosion control action plan for the sulphide dam construction. 

The first three elements of the plan – runoff conveyance, surface stabilization, and topographic modifications – are preventive measures to reduce erosion and soil loss, while the fourth element – sedimentation controls – is a structural control measure.  

All four aspects have been implemented at the construction site, the TVIRD said.

The sulphide dam is located on Canatuan creek near the southeast corner of TVIRD’s 508-hectare mineral production sharing agreement area. It has a tributary watershed of 585 hectares.

Nelson said only the first stage of the sulphide dam is under construction. Once finished, it will provide storage for copper and zinc for three to four years of mine operations beginning next year.

The TVIRD said it began its Canatuan gold and silver operations in mid-2004. Tailings from these mineral extracts are impounded in a separate dam, called the gossan dam.