Legal basis and related issuances invoked
- The Order is issued pursuant to Section 63 of Republic Act No. 7942 (Philippine Mining Act of 1995) (Preamble).
- The Order is also issued pursuant to Section 166 (General Provision on Environmental Protection) of DENR Administrative Order No. 96-40 (Preamble).
- The Order is issued with reference to DENR Administrative Order No. 96-40, Series of 1996 for tailings fees, reporting, and penalties (Section 31).
- The Order invokes compliance alignment with the Revised Implementing Rules and Regulations of RA 7942 (Preamble).
- The Order cites Presidential Decree No. 3931 of 1976 (Preamble), and invokes the Pollution Control Law of the Philippines and Presidential Decree No. 1152 (Philippine Environmental Code), Section 19 (Preamble).
Policy, purpose, governing principles
- The State’s policy requires that mine wastes and mill tailings produced by mining operators, permittees and contractors be managed in a manner that is technically, financially, socially, culturally and environmentally acceptable, effectively safeguarding the environment and protecting the rights of concerned communities (Section 3).
- Mine wastes and mill tailings management must adhere to sustainable development as a governing principle (Section 4).
- Sustainable development is implemented through two required emphases:
- Management must follow current best practices to ensure control over impacts and efficient environmental protection (Section 4.1).
- Management must give due and equal emphasis on economic and environmental considerations, and also on safety, health, social and cultural concerns (Section 4.2).
- The objectives are to manage mine wastes and mill tailings in an environmentally sustainable manner, with environmentally acceptable health, safety, social and cultural concern (Section 5).
Scope and regulated coverage
- The guidelines govern all mine wastes and mill tailings management within the territory and exclusive economic zone of the Republic of the Philippines (Section 2).
- The Order covers management from planning through operation and rehabilitation/decommissioning, including storage and placement facilities across mine life cycle stages (Chapters II–IV; Section 26).
Definitions expressly established
- “Angle of repose” is the angle of steepest slope at which material remains stable when loosely filed (Section 6).
- “Camber” means the crest settlement during construction and operation (Section 6).
- “Crest of Dam” means the top of the dam, generally sloped toward the reservoir to prevent water ponding (Section 6).
- “Design Basis Earthquake (DBE)” is the earthquake liable to occur at least once during the expected life of the structure (also called Operating Basis Earthquake (OBE)) (Section 6).
- “Deep Sea Tailing Placement” (DSTP) is a technology where mill tailings are discharged through an engineered outfall at a selected location and depth to minimize environmental impacts (Section 6).
- “Euphotic Zone” is the ocean’s highest biological productivity zone where light allows photosynthesis and reproduction of marine plants to occur, with its base operationally defined as the depth reached by only 1% of light transmitted from the surface (Section 6).
- “Flood Cycle” is a period of time during which floods or sequence of floods occur (Section 6).
- “Free Board” is the vertical distance between a specified reservoir water surface and the top of the dam without allowance for camber (Section 6).
- “Maximum Credible Earthquake (MCE)” is the maximum earthquake event conceived to affect the dam, considering potentially active faults near the dam (Section 6).
- “Mill tailings” are materials (solid, liquid, or both) segregated from ores during concentration/milling operations with no present economic value to the generator (Section 6).
- “Mill tailings placement facilities” are structures and equipment used in handling, transporting, disposing and/or impounding mill tailings (Section 6).
- “Mine wastes” are solid and/or rock materials from surface or underground mining operations with no present economic value to the generator (Section 6).
- “Mine Waste Dump” is a designated place where mine waste are accumulated or collected (Section 6).
- “Mine Wastes Placement Facilities” are structures and equipment used in handling, transporting, disposing and/or impounding mine wastes (Section 6).
- “Mixing Zone” is the zone where concentrations of potential contaminants may exceed ambient water quality criteria, with compliance at the boundary requiring a site-specific mixing-zone dimension established based on oceanographic and geochemical studies (Section 6).
- “Operation Base Earthquake (OBE)” is the earthquake liable to occur at least once during the expected life of the structure (also called Design Basis Earthquake (DBE)) (Section 6).
- “Rock Mass Rating (RMR)” is an empirical method to predict support requirements based on six properties: uniaxial compressive strength, Rock Quality Designation (RQD), joint spacing, quality of joints, groundwater conditions, and joint orientation (Section 6).
- “Rock Quality Designation (RQD)” is a quantitative index based on core recovery determined by incorporating only pieces of core equal to or more than 100 mm; the stated formula includes RQD = length of core in pieces >100 mm and requires that only core of at least NX size (53 mm in diameter) be used (Section 6).
- “Secretary” means the Secretary of the DENR (Section 6).
- “Surface mixed layer” is the ocean’s upper layer kept well mixed by wind and waves; its bottom is marked by an abrupt density discontinuity that prevents tailings from rising upwards when discharged below that discontinuity (Section 6).
- “‘g’” is expressed as horizontal acceleration divided by acceleration of gravity (9.81 cm/second²), producing a dimensionless ratio called “k” or horizontal seismic coefficient (Section 6).
- “Unconfined/Uniaxial Compressive Strength (UCS)” is a material’s ability to resist longitudinal stress without being confined at its sides (Section 6).
- “Unified Soil Classification System (USCS)” is a method classifying soil material based on grain size using sieve-based procedures (Section 6).
Mine wastes storage standards and rules
- Mine wastes storage must be selected, designed, constructed, operated and rehabilitated/decommissioned so it can be returned/converted to productive long-term and agreed land use (Section 7).
- Mine waste storage must be located far from listed sensitive areas: old growth or virgin forest, proclaimed watershed forest reserves, wilderness areas, mangrove forests, mossy forests, national parks, greenbelts, game refuge, bird sanctuaries, areas proclaimed as marine reserves/marine parks, and tourist zones (Section 8).
- A required buffer of not less than 500 meters from the perimeter must be maintained for mine waste storage near areas defined by law (Section 8).
- Mine waste storage must be located away from water bodies so that water flow after rehabilitation/decommissioning is reduced (Section 8).
- Mine waste storage close to the coast must be above the maximum storm surge level and must maintain a buffer of not less than 500 meters from the mean low tide level along the coast (Section 8).
- Mine waste storage site selection must consider: expected life of mine, geology, hydrology, geochemistry, ecology, land use, topography, possible mineralization, and climate (Section 8).
- Mine waste storage should be able to accommodate mine waste produced over the entire life of mine operation (Section 8).
- Mine waste storage must not be located on areas that might promote acid mine drainage (ARD) (Section 8).
- Mine waste storage must be designed and constructed above the maximum flood level (Section 8).
- In-pit dumping of mine waste must be used/promoted whenever applicable (Section 8).
- Mine waste dump design must consider expected mine life, geology, local and regional seismicities, hydrology, geochemistry, ecology, land use, topography, climate, available land area, and vegetation—covering design parameters like height, slope, and area (Section 9).
- A drainage system must be built to handle heavy rainfall, using a 50-year flood (return period) for minimum design purposes (Section 9).
- ARD potential for mine wastes intended for impoundment must be established (Section 9).
- Mine wastes with ARD potential and/or classified as hazardous or with toxic leachates must be contained separately from materials with no or lower ARD potential or non-toxic leachates (Section 9).
- ARD-characterized hazardous material must be neutralized or treated by blending with waste materials of higher neutralizing potential or less hazardous/toxic-leachate materials (Section 9).
- Construction must limit site disturbance to conform to the proposed design (Section 10).
- Drainage must be constructed during dump build-up to shed runoff without causing erosion (Section 10).
- Pre-stripped vegetation matter must be stockpiled separately (Section 10).
- The company must submit an “as-built-report” to the Bureau after completion of construction (Section 10).
- Stripped topsoil must be contained and protected from erosion for future rehabilitation (Section 10).
- Mine waste with potential ARD and hazardous leachates must be contained so it does not degrade adjacent areas and existing underground and surface waters (Section 10).
- Operation must maintain mine waste storage slopes below the angle of repose (Section 11).
- Mine waste characteristics must be established; materials with the same characteristics must be impounded separately from those with different characteristics for progressive/future rehabilitation (Section 11).
- Monitoring devices such as extensometers, movement hubs, and survey stations must be installed/provided during construction, active operation, and even storage decommissioning (Section 11).
- Drainage system must control siltation caused by surface runoff (Section 11).
- Run-off must be collected/contained and monitored and must meet existing standards before it flows to tributaries or wa