To make its assessment, Tetra Tech had used a Risk Based Prioritization Strategy (RBPS) that considered four major criteria: waste generation and management, pathways, receptors, and compliance. The higher the score a mine got, the higher the risks it presented. (see Tables 2 and 3)

Table 2: Criteria Codigo — Tetra Tech’s Risk Scorecard Source: Tetra Tech
CRITERIA	LINE ITEM OF CRITERIA	DESIGNATED SCORE
Waste Generation and Management	Airborne Liquid Solid	6 14 13
	Subtotal	33
Pathways	Air Solid and Liquid	1 20
	Subtotal	21
Receiving Media/Receptors	General Air Surface Water Groundwater Other Ecological Social Environmental	4 2 12 6 5 5
	Subtotal	34
Compliance	Violations Number of Valid Complaints	9 3
	Subtotal	12
TOTAL		100

The Philippine Pyrite mine in Bagacay, which topped the MGB list, garnered a risk rate of 82.53 percent in the Tetra Tech study. It ranked second among the 20 mines that Tetra Tech looked into, the top slot being occupied by Benguet Corporation-Dizon Copper/Gold Mines (BCD) in San Marcelino, Zambales, which scored 83.93 percent. The BCD mine had no community residing anywhere near its mine site, hence its exclusion from the MGB list.

The Philippine Pyrite mine, which extracted pyrite and copper for 36 years, is now the government’s flagship mine-rehabilitation project. The Mining Environment and Safety Division (MESD) of the MGB has pointed out that the mine not only exhibits many environmental problems, it is also located at the border of a nature reserve.

The threats at the Philippine Pyrite mine include the formation of an acid mine drainage, which may lead to the spread of potentially toxic metals. In addition, its tailings ponds are unstable and may collapse, spilling toxic contents. Its mill and laboratory facilities are also decrepit.

	Oil slick at Bued River downstream of quarrying operations at former Benguet Exploration mine site. [Photo courtesy of Tetra Tech EM Inc.]

Three of the six mines selected from the Tetra Tech study had no physical hazards, but they nevertheless made it to the MGB list because they had significant problems in other areas. Palawan Quicksilver, which mined mercury in Puerto Princesa for more than two decades, was among the three without physical hazards. Yet it apparently had considerable waste generation and management issues, scoring 29 points out of the possible 33 points in that category.

The two other mines that posed no physical risks were those of Benguet Exploration and Black Mountain. Sediment samples from these gold mines, however, showed that they exceeded screening standards for concentrations of all chemicals “of concern”: arsenic, lead, zinc, copper, and cadmium.

IN ITS report, Tetra Tech had acknowledged that a detailed rehabilitation and full implementation of engineering technology may not yet be feasible. But, it said, there are selected controls that need to be implemented especially for sites posing high physical risks to the surrounding population. These include the structural enhancement of tailings ponds and dikes to prevent collapse and contain waste rock in order to reduce acid mine drainage.

The report also highlighted the importance of understanding the source, pathway, and exposure scenario of potential contaminants. Tetra Tech recommended as well a full-blown site and ecological risk assessment after a few years of operation for a mine. This could help detect potential environmental damage early, it said.

In the meantime, MGB’s latest attempts to assess which idle mines need most attention have yielded only four mines “for further evaluation” so far: those of Atlas Consolidated Mining and Development Corporation (ACMDC)/Uldom Pit in Cebu, Hinatuan Mining Corp. (HMC) Manicani in Eastern Samar, North Davao Mining Corp. (NDMC) in Davao, and the Española mine in Palawan.

MGB’s newest assessment strategy requires each regional office to use these impact categories to gauge the level of risks presented at abandoned mines within its area: acid mine drainage hazard, safety hazard, impact to vegetation, erosional hazard, visual intrusion, and heritage value. MGB would then compile and evaluate each region’s assessment results to come up with a new list of mines to rehabilitate.

Choosing which mine to rehabilitate and how to go about that task have proved difficult and daunting, the MGB says. For instance, explains MESD engineer Marcial Mateo, each plan must be site specific, depending on the type of mine. And this takes a great deal of time, he says.

As for idle mines that now have lease applicants, Mateo admits that there is no way of knowing if those who have expressed interest in the mines would eventually assume responsibility over the environmental liabilities they would inherit. This is why, he says, the government is now considering the inclusion of rehabilitation and/or environmental liabilities as conditionality in lease applications for abandoned mines.

Mateo says that another option is to require the investor to pay the government for whatever expenses it would incur for the rehabilitation and remediation of a mine site. But whether or not there is an application to reopen an abandoned mine, he says, an in-depth evaluation of the current condition of the mines must be done.

Interestingly, for all the dangers posed by the abandoned mines, people interviewed by Tetra Tech for its report had called for their reopening. After all, these had provided employment for residents of the host communities when they were in operation, as well as for those in nearby areas. Mining companies were seen as stable sources of income compared to farming and fishing, which were among the more common means of livelihood of towns that also had mining sites.

Now if only someone would clean up the mess afterward.