The Tujuh Bukit Gold Mine utilizes water from six rainwater catchment dams for operational and domestic purposes, as well as groundwater from three boreholes with Water Extraction Permits (SIPA) for other domestic needs and plant propagation.

These dams are highly effective in capturing rainfall in the mining area, which experiences high rainfall (3,000 mm/year). Dam 6, located upstream, collects rainwater and allows sediment to settle, fulfilling domestic water needs. When Dam 6 reaches capacity, the excess rainwater flows into Dam 5. After sediment settlement in Dam 5, the water is gradually directed to Dam 3, which then flows water to Dam 2 and Dam 1.

Tujuh Bukit Gold Mine has established a compliance point (CP-1) between Dam 1 and Katak River to monitor the flow rate and water quality when it needs to be released into the river. This ensures that the water received by Katak River meets the government’s quality standards. CP-1 compliance point is in accordance with the Liquid Waste Disposal Permit (IPLC) issued by the Environmental Agency (DLH) of Banyuwangi Regency. The water monitoring facility is equipped with an automatic water monitoring device known as SPARING (Continuous and Networked Monitoring System for Wastewater Quality), as mandated by Ministerial Regulation No. P.80/MENLHK/SETJEN/KUM.1/10/2019. The SPARING device is connected to the server of the Ministry of Environment and Forestry (KLHK), allowing direct access to monitoring data on the flow rate and water quality released from Dam 1 to Katak River by KLHK.

Dams 1, 2, 3, 5, and 6 are frequently visited by Javan Pond Heron (Ardeola speciosa) and Great Egret (Egretta alba) for drinking and foraging. During certain seasons, flocks of Lesser Whistling-Ducks (Dendrocygna javanica) also visit the dam area. The presence of these wildlife species indicates that the water in these dams is safe for the environment.

The only dam that functions to collect process water, including runoff rainwater, in the leaching area is Dam 4, also known as the Storm Water Pond (SWP). The water in Dam 4 contains a low concentration of cyanide (a chemical used in the mineral leaching process) and is subsequently recycled or reused for mineral leaching. To prevent bird access, the water surface in Dam 4 is covered with floating bird balls, serving as a barrier. Dam 4 or SWP is constructed with compacted clay soil as the base and dam walls, lined with Linear Low-Density Polyethylene (LLDPE) that is impermeable to prevent process water leakage into the surrounding soil, ensuring environmental safety. In the event of heavy rainfall, excess water from Dam 4 undergoes detoxification treatment before being directed to Dam 3, ensuring its safety before flowing into Dam 2 and Dam 1.

In 2021, Tujuh Bukit Gold Mine added two compliance points. The first is CP-2, located at the sediment settling pond in the mining area, with occasional discharge to Pasir Pendek River during the rainy season. Some of the water collected in the settling pond is also pumped to Dam 3 for operational use or recycling purposes. The second compliance point is CP-3 at the surface facilities of the underground Tujuh Bukit Copper Project, with discharge to Dadapan River. Both CP-2 and CP-3 compliance points comply with the Wastewater Discharge Permit issued by the Banyuwangi Regency Government on January 28, 2021.

Wetar Copper Mine manages water within a closed circuit system. The managed water comes from mineral processing residues and runoff water. Water from mineral processing residues is collected in Storm Water Ponds (SWP) 3, SWP 2, and KK SWP, utilizing former mining pits. Runoff water is collected in sediment ponds Sump 3, Sump 4, Sump 5, Wetland, and the newly added sediment ponds in 2022: sediment ponds SP-1 and SP-2.

Both runoff and mineral processing residue collection points are connected to several rivers. Sump 3, Wetland, and SWP 3 are connected to the Kuning River; SP-1 and SP-2 are connected to the Lurang River; and Sump 4 and 5 are connected to the Wetuk River and Koreng River, respectively. If it is necessary to release water into the river, the water collected in the sediment ponds is neutralized beforehand to ensure it meets the government’s quality standards when discharged. Each release at the compliance points is measured, monitored, and reported to the government on a quarterly basis.

Wetar Copper Mine also monitors the water quality in the rivers within the mining area and the coastal areas near the river estuaries. River and coastal monitoring is conducted quarterly by a third party, and the results are reported to the government.