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close this bookConducting Environmental Impact Assessment in Developing Countries (United Nations University, 1999, 375 p.)
close this folder10. Case studies to illustrate environmental impact assessment studies
View the documentCase study 10.1 Tongonan Geothermal Power Plant, Leyte, Philippines
View the documentCase study 10.2 Accelerated Mahaweli Development Programme
View the documentCase study 10.3 Tin Smelter Project in Thailand
View the documentCase study 10.4 Thai National Fertilizer Corporation Project
View the documentCase study 10.5 Map Ta Phut Port Project
View the documentCase study 10.6 EIA at Work: A Hydroelectric Project in Indonesia
View the documentCase study 10.7 The Greater Cairo Wastewater Project

Case study 10.3 Tin Smelter Project in Thailand

Notes: This case study can be used by trainees to make mitigation plans and discuss post-project monitoring.

Name of the project: Environmental impact assessment for tin smelter project.

Type of environmental analysis: EIA.

Type of project: This is a metal-refining industry. The manufacturing process essentially involves heating the ore and utilizing the difference in melting point temperature (alloy formation involves slightly different methods) for obtaining the separation of the various components including the production of the tin metal of over 99.9 per cent purity from the original ore concentrate of approximately 73-75 per cent purity.

This is the only tin-smelting and refining plant in Thailand. It is capable of producing about 40,000 Mt/year of refined tin, which is 20 per cent of current total world production. A number of by-products are also produced, including tin-lead.

The industry produces three types of waste: namely liquid, solid, and gas. Domestic wastewater, laboratory wastewater and plant surface run-off are the main liquid wastes. Heavy metals such as Fe, Pb, Ta, Nb, Ti, Sn, Al, Zi, and Cn are the main heavy metal pollutants. Solid waste management does not pose any significant problem. Some amounts of toxic heavy metals, including Pb, As, Sb, and Bi, are emitted to the atmosphere. Also the sulphur present mainly in the fuel can generate significant quantities of SOx. Thus air pollution is the most threatening hazard at a tin smelter.

Project location

The tin smelter is located at the southern promontory of Ao Kham Bay on the southeast shore of Phuket Island, which is about 6 km south of Phuket town though 12 km by road. The plant is located adjacent to the tin ore processing facility. The plant is bounded on the east and south by the sea and the west and southwest by coconut groves. The total area of the plant is 5.8 acres.

Reports on pertinent studies

See References 1-4, page 305.

Environmental study area

The study area includes the land mass within approximately a 5 km radius of the plant. This area has been determined to cover more than adequately any resources which may be significantly affected by the tin smelter operation.

EIA team

The EIA team consists of two co-managers, with one project field engineer, two air quality experts, one socio-economist, one water quality expert, and one ecologist, with support staff.

EIA budget adequacy

Adequate budget was provided.


The methodology for preparing the EIA is that recommended by NEB (Ref. 5, p. 305). It is based on the methodology developed by the Battelle Institute/United States Army Corps of Engineers. In this methodology environmental resources are classified and evaluated in four general headings, namely: (a) natural physical resources, (b) natural ecological resources, (c) human use of economic development resources, and (d) quality-of-life values. In addition to estimating effects of the tin smelter operations on these resources, and identifying, delineating, and quantifying adverse effects, the method includes preparation of recommendations for minimizing unavoidable adverse effects and for offsetting these by positive enhancement measures.

To supplement the data from different sources, a number of field surveys were made covering all specialized environmental impacts (including socio-economics, wildlife, flora, and fauna, plus a sampling analysis of wastewaters, drinking water quality, health status of the workers, etc).

Existing environmental conditions


Based on discussions with long-time residents of Phuket, it appears that prior to the construction of the tin smelter (about 20 years ago), the study area was sparsely populated, with land use including some coconut groves, rubber plantations, and secondary forest. Agricultural development coupled with population growth has resulted in increases in cultivated crops as well as coconut and rubber plantations and thus created a more densely populated agricultural zone.

Environmental concerns

During the past 20 years (the duration of tin smelter operations), several new families have moved into what was previously a sparsely inhabited area. This can be expected as a result of increased economic opportunities from the industrial development, improvements in transport/access, etc. It may also be expected that the increased population may result in increased frequency and opportunities for complaints. Complaints on record cover blasting noise and smoke.

Blasting noise from slag granulation: frequently 2-3 times/day, mostly occurring during night; continuous blasting noises (> 100 times in each duration); disturbs relaxation time of surrounding people, patients, children, and babies; and caused different levels of vibration to houses depending on distances - creating damage to items, e.g. mirrors, window panes, and roof tiles.

Smoke from blasting and stacks: aesthetic nuisance (clothes and houses got dirty, bad odours); and fear of illness due to bad odours.

Environmental base map

The environmental base map (EBM) shows the plant and its environs. The EBM shows all potentially sensitive environmental resources, that is any resource which might be significantly impaired by the plant operations, including waste emissions.

Environmental effects from project

Adverse effects on physical resources

Air quality: odour and dust nuisance during certain hours on some days (though the modelling and stack emissions indicate that the tin smelter may not be the source); reduced yields from fruits from coconut plantations; and visible damage to leaves.

Noise pollution: noise has affected most of the residents of the villages.

Adverse effects on water resources

The wastewaters discharged from the laboratory and canteen without any treatment are unsightly and these waters exceed Ministry of Industry (MOI) standards for some parameters.

Adverse effects on human use values: agriculture

The smelter air emissions have caused significant reductions in yields of coconut plantations. Also the toxic effects of groundwater and soil polluted by tin dredge tailings which have been panned or stored in the coconut groves by local villagers have caused the plants to yield less.

Adverse effects on quality-of-life values: socio-economics

About 90 per cent of the respondents at Ban Ao Makhan and 100 per cent at Ban Laem Phan Wa Wee were negatively affected by noise and dust emissions.

Positive effects on human use values

Water supply: the tin smelter operations created beneficial impacts on water supply in that the smelter made arrangements for local villagers to utilize the groundwater supply developed by the tin smelter.

Mining/mineral resources: the operation of the tin smelter has an obvious beneficial impact on local, regional, and national mineral resource development and subsequent beneficial economic impacts.

Quality-of-life values: wage earning forms the major proportion of household income in the area. The smelter has created job opportunities and other related employment opportunities for the local villagers. These indicate long-term benefits for the people in the area.

Land prices in the vicinity have increased because of the presence of the industry. Economic benefits include benefits of increased earning and creation of jobs for the workers and their families as well as the gross regional product, and overall economic benefit to the nation.

Summarized projected effects

The impacts of the smelter operations are both beneficial and adverse, with the beneficial impacts outweighing the adverse. The primary beneficial impact is the economic benefit which is believed to play a major role in the villagers' good primary healthcare. In addition, the provision of water supply for many villagers is a primary beneficial impact.

The adverse impacts are related to air and noise pollution from the plant. Apprehension naturally results regarding health when one believes that air pollution is causing damage to vegetation, leaving deposits of dust at the living quarters, and may be damaging to human health. These fears may or may not be justified. The health data from the local clinic do not indicate any difference in the health condition.

Measures for offsetting adverse effects

Air quality

The cyclones, baghouses, and electrostatic precipitator are generally performing well. Consideration should be given to undertaking the corrective maintenance measures for the electrostatic precipitators (ESP) recommended by Research Cottrell as these measures will ensure a longer and more efficient operating life of the ESPs and should further reduce the frequency of tripping of the ESPs; bag replacement and maintenance should be improved, and the performance closely monitored; and consideration should be given to upgrading the old ventilated baghouses, so that the emissions are from a stack or stacks which can be monitored and also will reduce local dust deposition during calm periods.

Stack emissions from liquidator 3 resulting from dross production need additional pollution control in order to reduce the arsenic trioxide emission concentration. It has been proposed that by cooling the gas prior to baghouse filtration, the efficiency of filtration would increase. This cooling could be accomplished by installation of a medium efficiency dry cyclone with modification for air cooling in the exhaust line prior to the baghouse. It may also be necessary to install a second baghouse in series or vent the baghouse to an ESP. The approach here should be step-by-step to minimize unnecessary expenditures. This means that air cooling on a pilot scale should be tested first to determine the potential increase in arsenic removal efficiency of the existing baghouse. Further steps would be dependent on the results of the pilot testing. In addition it would be a good idea to only operate liquidator 3 on windy days to increase dispersion.

A general "tightening-up'' and possibly some modifications are needed for improving shop-floor ambient air quality. This is particularly true for the electric furnaces during charging, the refining and casting area, the hardhead tank, and the area around the AI/As dross storage room and liquidator 3 (particularly during liquidating). An analysis of needs for improvement in hygiene lines, exhaust fans, protective structures, etc., is needed to enable detailed design of cost-effective facilities. A corrosion control analysis should be incorporated in the study in order to prevent further corrosion-related gas line leakage.

The baghouse and hygiene system engineering study and improvement planning is completed and detail design is underway. The construction was expected to begin in the second half of 1986.

Water pollution

The water pollution analysis shows that the only pollutants exceeding MOI effluent standards are from the laboratory and canteen. Because of the small volume of wastewater and the vast dispersion/dilution effect of the tides and currents, it is evident that the effluent does not significantly impact on the local ecology. However, the smelter could easily meet MOI standards by routing the canteen wastewater flow to a septic tank/oil trap system and pumping the laboratory wastewater to the septic tanks system rather than directly discharging to the sea. This will eliminate any direct discharge of undiluted or diluted laboratory wastewater (this is the same disposal method as is commonly used by laboratories in Bangkok).

Noise pollution

The effect of noise pollution has been evaluated by noise level measurements at various locations in-plant and in surrounding communities. Noise pollution was shown not to be an occupational hazard for workers. The normal plant operation does not have any significant effect on sound levels in nearby villages. However, periodically, there are explosions due to slag granulation which are reported to cause nuisance conditions at nearby residences. The smelter has been and is continuously making every possible effort to reduce the frequency of such explosions. The frequency has been reduced from the occurrence of explosion in 18 per cent of tappings in 1983 to 14 per cent in 1985. This results in an average of less than two explosions per week. It is possible that this is the best achievable under present processing circumstances and is thus an unavoidable impact. It is not feasible to shift processing times to ensure that the slag explosions occur during the day. The smelter is continuing to modify its processing to reduce the number of slag explosions. One of the expansion plans is a new cooling water system, for the improvement of the water pressure and water flow rate of the slag granulation system. The high pressure and the high flow rate of granulating water will reduce the chance of slag explosion and therefore reduce the frequency of slag explosion. The installation of the cooling water system is planned within 1986/87 smelter budgets.

Solid wastes

Solid waste pollution control is not a significant factor in the assessment of environmental impacts of the tin smelter because the process solid wastes are either recycled or sold as slag or dust.

Environmental monitoring

The monitoring activities are planned to provide confidence in the continuous improvements in pollution control at the smelter and to ensure that the objectives of environmental protection are met.

The plan includes monitoring of both the natural environment and public and occupational health-related parameters. The monitoring will include systematic measurement of air and wastewater discharges from the smelter as well as special periodic ambient environmental quality measurements.

The implementation of the monitoring plan will serve to provide the following:

(a) establish a database to confirm meeting applicable MOI and National Environment Board criteria and standards;

(b) ensure worker health and safety;

(c) assist in the efficient operation of the smelter by providing feedback on operation/maintenance.

The monitoring programme includes point-source sampling for all significant air and wastewater discharges and ambient air quality sampling for the shopfloor and at the two nearby villages. The monitoring programme also includes continued monitoring of drinking water quality, recording of operational problems of air pollution control facilities, recording of blast occurrences, and continuing safety/health checks. The smelter monitoring programme will commence when appropriate equipment has been identified and obtained. Periodic reports will be issued to the MOI as required.

Concluding remarks

From the overall assessment it can be concluded that, while the tin smelter operations do cause minor effects on the local environment as a result of wastewater and noise, the only significant adverse effects may be caused by air emissions. These problems can be readily overcome so that the overall adverse impacts of the smelter will be minor or possibly insignificant, especially when compared to the major social and economic benefits derived during the past 20 years of operation and which are expected to continue in the future. These benefits are enjoyed by the local population, the Upper South Region, and the nation.


1 Metal Levels Associated with Tin Dredging and Smelting and their Effects upon Intertidal Reef Flats at Ko Phuket, Thailand, Coral Reef, Chapter 1, pp. 131-137, 1982.

2 Environmental Guidelines for Coastal Zone Management in Thailand/Zone of Phuket, H. F. Ludwig/SEATEC, 1976.

3 Inception Report: Environmental Impact Assessment for Thailand Tin Smelter, prepared by SEATEC Consortium, October 1984.

4 First Progress Report, Environmental Impact Assessment for Thailand Tin Smelter, prepared by SEATEC Consortium, March 1985.

5 Manual of NEB Guidelines for Preparation of Environmental Impact Evaluations, National Environmental Board, 1979.