Page 117 - Plant design and economics for chemical engineers

GENERAL DESIGN CONSIDERATIONS 93

facilities are widely used and can serve as a useful supplement to rail and water
facilities. If possible, the plant site should have access to all three types of
transportation, and, certainly, at least two types should be available. There is
usually need for convenient air and rail transportation facilities between the
plant and the main company headquarters, and effective transportation facilities
for the plant personnel are necessary.
Water supply. The process industries use large quantities of water for cooling,
washing, steam generation, and as a raw material. The plant, therefore, must be
located where a dependable supply of water is available. A large river or lake is
preferable, although deep wells or artesian wells may be satisfactory if the
amount of water required is not too great. The level of the existing water table
can be checked by consulting the state geological survey, and information on the
constancy of the water table and the year-round capacity of local rivers or lakes
should be obtained. If the water supply shows seasonal fluctuations, it may be
desirable to construct a reservoir or to drill several standby wells. The tempera-
ture, mineral content, silt or sand content, bacteriological content, and cost for
supply and purification treatment must also be considered when choosing a
water supply.

Waste disposal. In recent years, many legal restrictions have been placed on the
methods for disposing of waste materials from the process industries. The site
selected for a plant should have adequate capacity and facilities for correct
waste disposal. Even though a given area has minimal restrictions on pollution,
it should not be assumed that this condition will continue to exist. In choosing a
plant site, the permissible tolerance levels for various methods of waste disposal
should be considered carefully, and attention should be given to potential
requirements for additional waste-treatment facilities.

Labor supply. The type and supply of labor available in the vicinity of a
proposed plant site must be examined. Consideration should be given to
prevailing pay scales, restrictions on number of hours worked per week, compet-
ing industries that can cause dissatisfaction or high turnover rates among the
workers, and variations in the skill and productivity of the workers.

Taxation and legal restrictions. State and local tax rates on property income,
unemployment insurance, and similar items vary from one location to another.
Similarly, local regulations on zoning, building codes, nuisance aspects, and
transportation facilities can have a major influence on the final choice of a plant
site. In fact, zoning difficulties and obtaining the many required permits can
often be much more important in terms of cost and time delays than many of
the factors discussed in the preceding sections.

Site characteristics. The characteristics of the land at a proposed plant site
should be examined carefully. The topography of the tract of land and’ the soil