SF3’s open spillway, with two of its three chutes done; the third one will be undertaken during the next dry season | BF (Sept. 2, 2013)

Philex to raise TSF3’s tails beach to 608 ML for more stability

Saturday, November 9, 2013

Open spillway would be able to channel up to 1,500 mm of rain over 24 hours  

Philex Mining Corp. aims to raise to between 602 and 608 meters the tailings beach in a storage facility at Padcal Mines, as part of its move to further stabilize this for the continued production of gold and copper in Benguet.  

The beach at the Tailings Storage Facility No. 3 (TSF3), where Philex Mining has been dumping about 26,000 tons of tails daily from March 8, is currently at 597 meters above sea level (masl), according to Libby Ricafort, vice president at Philex Mining and resident manager of Padcal.  

€œWe must continue with our operations at the current pace, in order to bring our TSF3 at its former condition before the Aug. 1, 2012 accident,•€ he stressed. •€œAt 602 masl, little water will go into Penstock B while at 608 masl, the latter may be decommissioned.•€  

Building an open spillway at and creating a beach in TSF3 are part of the government-approved urgent remediation measures for the pond. The beach is done by filling up the void created by a sinkhole when TSF3 discharged nontoxic water and sediment onto Balog Creek after historically unprecedented rains brought about by two successive typhoons.  

Since August, water has been flowing onto the open spillway from TSF3, whose two chutes were done in June while the third and last one will be undertaken during the next dry season. Upon full completion, the spillway, whose each chute measures 12 meters wide and 300 meters long, will be able to channel up to 1,500 millimeters (mm) of rain over 24 hours•€”or more than thrice the 455 mm of rain that Typhoon Ondoy dumped over a 24-hour period in 2009.  

According to government regulation, an open spillway must be designed in such a way that it could withstand a flood event having an unusual rainfall with a 1-percent chance of occurring at any given time. For TSF3 and its open spillway, this unusual rainfall would be equivalent to 1,000 mm in 24 hours.  

€œPadcal•€™s urgent remediation measures have progressed significantly since government regulators allowed Philex Mining to resume operations,•€ Michael Toledo, SVP for Corporate Affairs at Philex Mining, said.  

Mr. Ricafort said the 602 meter level (ML) of tails at TSF3 can be achieved in between nine and 12 months from July, while having the 608 ML may take another two years, emphasizing that the less than 100-hectare pond is cone-shaped and, therefore, becoming wider from bottom to top.  

He added that there is now a limited amount of water going into the pond•€™s Penstock B, which may be decommissioned once the tails beach rises to between 602 ML and 608 ML while the offset dike, which is being reconstructed, reaches 615 ML from its current 611 ML.  

It may be recalled that Philex Mining had condemned TSF3•€™s Penstock A and its connecting Tunnel A and sealed these off with concrete after the accident. Penstock B and Tunnel B, on the other hand, may still be used if needed.

The quality of water at tributaries near the Padcal mine site, including Balog Creek and Agno River, and even downstream to the irrigation canal in Pangasinan, has passed regulatory limit and remained below the effluent standards set by government, while fish samples were within the criteria imposed by foreign environmental commissions.  

Scientists, environmentalists, and engineers earlier said the filling and beaching process at TSF3 as well as the building of a spillway were the safest and fastest way of bringing the pond•€”designed to hold solids, not liquid•€”back into its stable condition before Aug. 1, 2012.