Complex sentence: Most natural pumping stopped during the 1970s, and from the mid- 1980s until its closure in 2006, New Cheshire was the only salt works in the UK to use the natural brine pumping method.
Split into simpler sentences: Most natural pumping stopped during the 1970s, but New Cheshire continued to use the process. From the mid- 1980s until its closure in 2006, it was the only salt works in the UK to use the natural brine pumping method.