Complex sentence: The Columbia Generating Station features six low-profile fan-driven cooling towers, in which water warmed by heat exchange with the steam after it leaves the turbine is cascaded down the tower and cools by a combination of evaporation and heat exchange with the surrounding air.
Split into simpler sentences: The Columbia Generating Station features six low-profile fan-driven cooling towers. Each tower cascades warmed water, a byproduct of water heat exchanging with steam after leaving a turbine, down itself and subsequently cools the warmed water via a combination of evaporation and heat exchange with the surrounding air.