High cost of time requirements and environmental impact
While Natural gas is relatively cleaner and cheaper fuel relative to other fossil fuels, the pipeline infrastructure has a severe impact on the environment. Its demand has been increased in past few decades to meet the energy short falls. Natural gas is produced from oil gas wells in gaseous state. Oil and gas wells are mostly located in remote areas. On the other hand the consumption of natural gas is mostly in urban areas. The most convenient method adopted for the distribution of gas is by means of pipeline network that is laid down and connects gas producing fields with the gas consuming sites.
Pipelines are complex structures to be laid. So, pipelines should be effectively designed which can reduce the pipeline lying cost and also ensures in the uninterrupted gas supplies to the customers. Designing of pipeline network includes route planning, selecting the appropriate pipe grade according to weather conditions of the area and composition of natural gas and cost estimates. Appropriate pipeline installation plan also reduces the time required which makes it cost effective. Pipelines can also be a cheaper mode of transportation if there are giant producing fields and huge demand at the consumption sites.
As the pipeline design is ready then environmental risk assessment of that design is done to avoid or minimize any environmental risk that can be generated due to installation of that pipeline network. In case of gas pipelines, environmental risk is defined as result of any change that is caused by the pipeline project to the
environment, ecosystem, socio- economical things and to the cultural heritage. While doing the environmental risk assessment for pipelines it should be kept in mind that this assessment neither involves the environmental risks associated with the exploitation of reserves nor the risks associates with burning of that fuel. It only involves the assessment of risks that are related to the transport of fuel.
The major environmental risks associated with gas pipelines generally come across during the pipeline construction or in case of pipeline rupture. The most common environmental impacts caused during pipeline installation are discussed here. Air quality of area is greatly disturbed during the construction of pipelines because of dust and greenhouse gases emission by construction machinery.
It can be controlled by using water and covering the area during construction. Noise is also produced during the operation of construction machinery to minimize its impact staff should be provided with protective instruments and proper maintenance of equipment should be done that reduces the noise and also increases its efficiency. If the construction activities are going on over the slope this may cause the slope instability, which must be handled with care to avoid greater losses. Some methods like blasting impose a great risk over environment. It can cause the instability of ground and can also contaminate the ground water if the aquifer is laying at shallow depths. So, these types of methods are only used when necessary.
Vegetation and wild life are badly effected during the pipeline construction. To, minimize the effect of this pipeline route should be planned in such manner that minimum or no habitat loss of wild life occur and as the construction of pipeline is complete the vegetation cover of ground should be restored by planting vegetation. During pipelines construction soil is disturbed on massive scale that would lead to increase in soil erosion. Increased soil erosion has an adverse impact on natural land scape and also increases the sediment influx into the stream and hence decreasing their discharge capacity.
Increased sedimentary influx also disturbs the aquatic life. Soil erosion can be minimised by planting vegetation as early as possible. If any water body came across the pipeline route then minimum disturbance should be done there to avoid water contamination and ecosystem disturbance.
In addition to the risks associated with pipeline construction there are some other factors that can effect the environment after the installation. As pipelines are installed for longer periods of time so their routes should be adopted wisely. So it should not block the passage of wildlife.
One of the major and common risks associated with pipelines is rupturing or leaking. Rupturing or leaking of pipeline releases toxic compounds into the air. Because natural gas sometimes contains compounds of Sulphur, nitrogen and oxygen that can be a risk to life dwelling near the pipeline and affect the air quality due to these pollutants. Rupture or leaking can be caused by many factor but main factors are corrosion and natural disasters like earthquakes, floods etc.
So, while designing pipeline project and selecting pipe material the weather conditions of area, hazard map and history of area along with composition of gas must be considered to make pipeline durable and long lasting. Pipes are subjected to weather conditions from outside and chemical environment created by gas from inside. So, if the pipes are made of reactive material they corrode rapidly and life of pipeline will be reduced. Some times gas contains high concentration of oxygen that corrodes the pipe by making iron oxide because pipes are mostly made up of iron. To avoid this true material must be selected for pipes according to gas composition. Effect of weather can be reduced by using protective coating on pipes like tar coating etc.