I was born in Oshawa and grew up there and Bowmanville. There is a nice farmer bottle dump that I dug as a kid on Concession road in Bowmanville. Go down Concession and just before the old training school, which was actually a German POW camp in W.W.2, there is a small bridge that you cross. The small ridge on your right immediately after the bridge, and going up to a farm field was a farmers dump. I found neat stuff in there as a kid. So the bridge, training school on left, farmer dump to the right immediately after crossing. The trick for bottles is to look for brown rusty cans etc. Look up the sides of hills in the spring, no leaves on brush. Find rusty cans and junk, you may hit a sweet spot, bring a shovel.