Far left of the house, where you call the boat, there is a rock that you can get on to which stops tanks appearing and only a handful of infected can get there.

Watch out for smokers, but that's about it.

Once the second tank has gone (music only) you can bolt under the house at the back to the jetti (pier) and use a pipe bomb, or as Bill would say "A Black Powder Bomb" if you need to.