Definitions of Key Terms
- Variance: Temporary suspension or relaxation of water quality standards to allow for study and implementation of proper control systems.
- Geothermal Exploration: Preliminary drilling and testing activities to confirm geothermal resource viability and assess reinjection capacity.
- Geothermal Fluid: Substances derived from geothermal resources.
- Geothermal Resource: Heat from geothermal fluids usable for various purposes.
- Geothermal System: Complete subsurface hydrologic system related to geothermal resource.
- Geothermal Prospects: Geographic areas where geothermal resources may exist.
- Geothermal Well: Cased borehole for production or reinjection of geothermal fluid.
- Reinjection: Process of returning separated brine back to the reservoir.
- Reinjection Constraints: Conditions making reinjection unfeasible.
Rationale for Issuance of Water Quality Variance
- Geothermal energy is vital to Philippine energy self-reliance.
- Exploration involves drilling and discharging geothermal fluids to assess resources.
- Reinjection is ideal but often constrained by technical or economic factors.
- Constraints include absence of reinjection wells, high pipeline costs, rapid reinjection returns, and mineral deposition.
- No cost-effective treatment exists for geothermal brine’s high boron and arsenic content.
- Therefore, water quality variances for boron and arsenic are necessary.
Prescribed Water Quality Variance
- Regulated discharge of geothermal brine with temporary suspension of arsenic and boron effluent standards.
- Boron criteria relaxed from 0.75 mg/L to 2 mg/L for Class "D" waters, if no citrus plants are present downstream.
- Arsenic criteria relaxed from 0.05 mg/L to 0.1 mg/L for Class "B", "C", and "D" waters.
- Extension of mixing zone up to 10 meters upstream from critical water use points.
Restrictions and Conditions
- Variance subject to annual DENR review; valid for 5 years per project.
- Variance activated upon project proponent notification and excludes inactivity periods.
- If drinking water sources or citrus plantations are downstream, the area must be bypassed or alternative water supplied.
- Project proponent responsible for damages and must provide compensation and remediation.
- Appropriate regional permits must cover the variance period (e.g., Authority to Construct, Permit to Operate).
- Project proponents must determine mixing zones to aid monitoring.
- DENR tasked with monitoring compliance.
- Immediate effectivity upon issuance.