▁ 6 th ▁min el ay ing ▁exc urs ion ▁on ▁ 1 8 ▁August , ▁ ▁plant ed ▁ 3 1 0 ▁mines ▁during ▁the ▁ 7 th ▁min el ay ing ▁exc urs ion ▁on ▁ 2 6 ▁August , ▁ ▁plant ed ▁ 2 9 0 ▁mines ▁on ▁ 3 0 ▁August ▁to ▁complete ▁the ▁ 7 th ▁mine field ▁after ▁USS ▁ ▁was ▁unable ▁to ▁lay ▁its ▁mines , ▁ ▁plant ed ▁ 3 2 0 ▁mines ▁during ▁the ▁ 9 th ▁min el ay ing ▁exc urs ion ▁on ▁ 2 0 ▁September , ▁ ▁plant ed ▁ 3 3 0 ▁mines ▁during ▁the ▁ 1 0 th ▁min el ay ing ▁exc urs ion ▁on ▁ 2 7 ▁September , ▁ ▁plant ed ▁ 3 3 0 ▁mines ▁during ▁the ▁ 1 1 th ▁min el ay ing ▁exc urs ion ▁on ▁ 4 ▁October , ▁and ▁ ▁plant ed ▁ 3 4 0 ▁mines ▁during ▁the ▁final ▁ 1 3 th ▁min el ay ing ▁exc urs ion ▁on ▁ 2 4 ▁October . ▁This ▁effort , ▁nearly ▁completed , ▁was ▁the ▁major ▁operation ▁of ▁the ▁U . S . ▁Navy ▁in ▁European ▁waters ▁during ▁World ▁War ▁I , ▁and ▁it ▁came ▁to ▁an ▁end ▁on ▁ 1 1 ▁November ▁ 1 9 1 8 ▁with ▁the ▁Arm ist ice ▁with ▁Germany ▁and ▁the ▁end ▁of ▁fighting ▁in ▁World ▁War ▁I . ▁USS ▁A ro ost ook ▁ste amed ▁ ▁home ▁to ▁the ▁East ▁Coast ▁in