Complex sentence: At 11.20 a.m. on April 7, when the lake level had reached a height of 11.07 feet above the crest of the dam, the dam gave way at a point about 300 feet from the east end of the dam.
Split into simpler sentences: At 11.20 a.m. on April 7, when the lake level had reached a height of 11.07 feet above the crest of the dam, the dam gave way at a point. About 300 feet from the east end of the dam.