Arsenic Mining Remediation
Wenshan
This project was initiated in late 2006 in Yunnan, China through dialogue between Blacksmith Institute and the Yunnan Environmental Protection Bureau (EPB). The primary problem at the site was the contamination of local water supplies with arsenic and other metals, which originated from small abandoned metal mines and processing facilities. The local pollution problems were severe and, because heavy metals do not degrade in the environment, the erosion of these materials added to the cumulative pollution load on the river system. The objective was to develop practical approaches for this type of situation in collaboration with the Yunnan and local EPBs, which would be a model for other mountain villages with similar problems. The project was structured to provide direction and momentum for a wider effort by the Province to address mining pollution and water contamination challenges.
Project Strategies
In May 2007, a technical team from Blacksmith, together with officials from Yunnan EPB and local governments, made visits to the three mine areas in the mountains. Engineers and technical staff from the different government agencies joined the visiting specialists for the visits. A detailed report was prepared covering a number of sites in the three mining areas, and it was agreed that the pilot remediation would be implemented at one particular site, known as Wenshan No.4.
The strategies for remediation included the construction of a retaining wall to create a stable tailings storage area along with the installation of an impermeable lining for the zone. The dumped arsenic residues were then moved to this secure area and placed in compacted layers to ensure stability. The surface of the completed storage area was vegetated using local species suited to the environmental conditions, and drainage ditches were installed along the sides of the final storage area to divert surface water flows. Controls were also put in place to prevent unauthorized access and to deter the scavenging of remaining structures.
Outcomes and Follow-Up
Surface water drainage samples were taken by the Wenshan County EPB at the request of Blacksmith in order to provide a baseline level against which the post-remediation contamination data could be compared. The reported arsenic concentration in the drainage from the site before the project was 1.07 mg/L, which is more than twenty times above the suggested safe level (0.05 mg/L). The arsenic content in the drainage systems after remediation was 0.048 mg/L, which is just within safe consumption limits. The authorities planned a program of sampling during the rainy season in order to provide a better picture of the project’s success in containing the contamination and reducing off-site transport.
The success of the pilot project has been recognized by authorities in Yunnan, and has reinforced the value of the approaches and the potential for developing the broader program. A large part of the success of the pilot project was due to the commitment and efforts of the Wenshan County Government with the backing of Wenshan Prefecture and the Province.
According to the Wenshan County EPB, there are at least five old smelters in the county that need to be addressed, and there are an estimated one million tons of polluted material that needs to be controlled. Wenshan Prefecture is preparing a comprehensive plan to address related issues in all the affected counties. The new national policy on environmental protection in rural areas is providing a favorable context to progress with remediation efforts. Blacksmith and the Yunnan EPB are continuing the dialogue with Wenshan Prefecture and County about possible ways to provide technical and financial support to the remediation efforts. The team will also follow up with the Provincial authorities on the lessons learned from the project, and how these lessons can be applied more broadly.
