Hi, help me please to make this text sound more English. Thanks in advance. I marked what I spotted, is there anything else?


The extreme Sakhalin environment presented several challenges for the heavy Sakhalin II topsides. At 21,000 tonnes each, they are the largest ever built, and will operate in conditions of extreme cold and heat, wave and ice pressure, and high seismicity.

The western Pacific has long, rolling waves rather than high ones, which built (that build?) up a lot of energy by the time they hit the platform. The Sakhalin cold is notorious – temperatures drop to - 40 degrees Celsius in winter. But less well known are the summer temperatures in the 30s. This large temperature differential can cause the topsides to move. The need to winterize the topsides so that they would be (are?) safe and warm for year-round use added up to a top-heavy structure set on top of a concrete base lashed by waves, pressured by ice and threatened by some of the world’s severest earthquakes.

(shouldn't there be something that relates to 'added up', I mean I add up something, not just add up to something).

The AMEC engineering team adapted a design developed in the US for buildings in earthquake zones that used specially developed pendulum bearings to help isolate seismic loads. Using leading-edge seismic design expertise from Russia and California, coupled with their own mathematical prowess, they generated a simulation of the platform’s response to an earthquake. Some of AMEC’s experts in this area started in the aerospace industry and enjoy the greater diversity of technical challenges that the offshore industry generates in both conventional structures and those of the frontier projects.

The result is a set of unique bearings used to isolate the seismic loads on the topsides. They are each two to three metres in diameter, the largest ever made. Another design innovation was the placement of the topsides much higher than usual on the gravity bases. A 15 metre gap is standard between platform and base; AMEC set a gap of 27 metres. This in turn created a problem for the floatover- the barge manoeuvre to mate the topsides with the bases. A purpose-built barge had to be designed and constructed for the operation. The floatover was accomplished in less than 24 hours in June 2006- an industry record.