Environmental Engineering Reference
In-Depth Information
characteristics specific to the project. The identification of sources of potential significant
impacts may lead to changes in layout and process.
Data about the project can be presented in different ways. The life cycle of a project
can be illustrated on a linear bar chart. Particular stages may be identified in more detail
where the impacts are considered of particular significance; this is often the case for the
construction stage of major projects. Location and physical presence are best illustrated
on a map base, with varying scales to move from the broad location to the specific site
layout. This may be supplemented by aerial photographs, photo-montages and visual
mock-ups according to the resources and issues involved (Figures 4.3-4.6).
A process diagram for the different activities associated with a project should
accompany the location and site-layout maps. This may be presented in the form of a
simplified pictorial diagram or in a block flow chart. The latter can be presented simply
to show the main interconnections between the elements of a project (see Figure 4.4 for
socio-economic processes) or in sufficient detail to provide a comprehensive picture.
Figure 4.5 shows a materials flow chart for a petroleum refinery; it outlines all the raw
materials, additives, end products, by-products and atmospheric, liquid and solid wastes.
A comprehensive flow chart of a production process should include the types, quantities
and locations of resource inputs, intermediate and final product outputs and wastes
generated by the total process.
The various information and illustrations should clearly identify the main variations
between a project's stages. Figure 4.6 illustrates a labour-requirements diagram that
identifies the widely differing requirements, in absolute numbers and in skill categories,
of the construction and operational stages. In addition, more sophisticated flow diagrams
could indicate the type, frequency (normal, batch, intermittent or emergency) and
duration (minutes or hours per day or week) of each operation. Seasonal and material
variations, including time periods of peak pollution loads, can also be documented.
4.7 Establishing the environmental baseline
4.7.1 General considerations
The establishment of an environmental baseline includes both the present and likely
future state of the environment, assuming that a proposed project is not undertaken,
taking into account changes resulting from natural events and from other human
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