I have a sloping vegetable garden with landscape bricks used as border. Because of the huge slope all soils are getting washed away through the landscape bricks. I plan to add top soil to bring up the level on the slope and level off the ground - Landscape brick does not seem to stop the soil erosion. I was planning to have someone put railroad ties but somebody told me that since the woods are pressure treated I should not use them for vege garden. what kind of material should I use on the sides as walls and is there something I can lay by myself (I can not do railroad ties)?