An environmental impact is an event or effect which results from a prior event (Wathern, 1989).

An assessment of the likely changes in the environmental parameter over a certain period and within a defined area, resulting from a particular activity therefore demands an understanding of the specific aspects of the development. It may be therefore appropriate to first consider the likely events occurring in different phases of the proposed LPG Plant Project.

Construction phase activities

Construction phase would require a vide variety of both on and off site preliminary activities which need to be completed before the operation for the recovery of LPG can begin.

These activities include­:

i. Construction of site access roads and internal roads.

ii. Marking of the site boundaries.

iii. Positioning hedges and fences at the site parameter.

iv. Construction of processing plant and recovery unit.

v. Construction of site office building and storage sheds.

vi. Construction of labours camps.

vii. Advance planting in green belt zones.

viii. Laying of pipelines for transport of feedstock for LPG and the lean gas to and from the plant.

ix. Development of utilities like heating and cooling systems, compressed air systems, fuel gas systems, flare systems and LPG storage and transfer systems.

x. Development of effluent treatment facilities in the LPG Unit for operational phase.

Operational phase activities

The operational phase of the project involves the processing of feedstock received from Bombay for recovering LPG. The process involves expansion of gas entropically through turbo expander. The gas gets chilled to about -50°C. The fraction condensed due to chilling is separated and fractionated to recover LPG (Appendix-II).

LPG Recovery Unit process is relatively a clean operation and no hazardous or toxic wastes are produced regularly. However, during emergency condition like power failure or blocked discharge, total feed gas would have to be disposed off to prevent pressurisation of plant. For this purpose, provisions of a flare stack has been made to incinerate the gas and discharge the flue gases at environmentally safe heights.

The LPG recovery produces small quantities of water which may contain some heavier hydrocarbons. Adequate provisions for the treatment and disposal of waste waters are incorporated in the plant design.

• Prediction of Project Related Impacts