dwellings, new port facilities, new road and rail links, new asphalt plants at quarry sites.
Cumulative impacts can result in the context of the regional environment in which a project is to be placed and the possible build up of impacts. Cumulative impacts related to the effluent discharge from sewerage schemes are discussed in Guidelines for “Major Sewerage Schemes” and cumulative issues for atmospheric emissions are covered in the Guidelines for “Thermal Power Stations”.
For industrial estates with many individual users of water and the potential generators of large quantities of effluent, it is important to have a full understanding of the existing capacity of natural systems to absorb new levels of discharge. In many cases where river flows are smalI, and particularly if the flow of a receiving stream is at anytime less than the quantity of effluent produced by the estate, there can be costly mitigation required. Unless the effluent can be treated (or cooled in the case of cooling water) to be of equal or better quality than the receiving water, disturbance of the aquatic ecosystem is inevitable. Such treatment, if technically achievable at all, is likely to be extremely costly. Alternative sites with receiving waters capable of accepting properly treated effluent without significant degradation, could lead to lower costs over the life of the facility. The same can be true of sites where water supply is limited or where meteorological conditions (e.g. frequent atmospheric inversions) would necessitate unusually stringent treatment practices.
Another relevant aspect in relation to assimilation ability is the impact of non-routine operations such as process upsets, failure of pollution control systems and accidental releases. Proximity to sensitive natural areas or human settlement may necessitate extraordinary measures to prevent or respond to such events.
Employment opportunity on a large scale draws in immigrant workers and thus the growth of local communities. The community may well experience induced land development and it may be ill-prepared to manage its impact. Such impacts range from overloading of municipal infrastructure and services to cultural conflicts between existing residents and immigrant workers. Particular care is needed to prevent unplanned settlements immediately adjoining the new estate and this has to be done through the institution strengthening of local government and the development of zoning rules and their enforcement. Industrial estates require full EIA reports and full public participation; the involvement of the local community is essential to assist in minimising such induced adverse impacts.
NEGATIVE IMPACTS AND MITIGATION MEASURES
Negative impacts are considered in these guidelines in four distinct areas.
site selection stage
To assist proponents putting together an Environmental Report, impacts and mitigation are discussed in a systematic way under the four distinct project stages identified above. Appendix I is a checklist for proponents of the impacts and relevant mitigation, which are