Environmental Engineering Reference
In-Depth Information
The site of extraction is not the only area impacted by oil production. Oil is mostly
transported via two routes: by sea in tankers or over land through pipelines. As trade in oil
has grown, so too have the ships used to transport it. Up to the end of the Second World
War, oil tankers typically carried between 10,000 and 20,000 tonnes of crude oil. By the
1970s, the new class of 'ultra large crude carriers' had capacities exceeding 500,000 tonnes
ever, the sheer size of modern tankers, plus the number of tankers plying the oceans at any
given time, makes them a serious threat to the coastal and marine environment. The largest
ship-based oil spill to date was the 276,000 tonnes of crude from the Atlantic Empress near
Trinidad in 1979. Though this released nearly eight times as much oil as the Exxon Valdez
spill off Alaska a decade later, it failed to catch headlines in the same way because most of
the oil did not reach land.
Although more oil is traded today than ever before, in the last two decades spills from
oil tankers have become far less frequent and, where they occur, less serious, thanks to
improvements in ship design and safety regulations, and to the ever-expanding networks
of oil pipelines. Pipelines might seem a more environmentally sound way of transporting
oil, yet they are also more susceptible to spillages because of sabotage or theft. Secondly,
migrating animals, from hedgehogs to caribou, experience oil and gas pipelines as barriers,
preventingthemfrommovingtowinteringorbreedingareas.Forthatreason,somemodern
pipelines are elevated to allow animals to pass underneath (see
Figure 6.6
)
.
