The photo above shows a low wall made of stacked wooden railroad ties. Almost all wooden retaining walls I've seen in Seattle are made of railroad ties, but there are a few execptions out there.
As you can see, the color of the wood is black. This is because railroad ties are treated with creosote, which is a wood preservative derived from coal tar. In my opinion, this makes for a particularly ugly facade, as the texture of the wood is always coarse, and the blackness looks, well, like it should be on a railbed!
Seattle is renowned for its "green" culture, and a strong emphasis on environmental issues. Thus it seems to me particularly ironic that the city of Seattle allows the use of creosote in an outdoor setting, as it contains polycyclic aromatic hydrocarbons, which are know carcinogens.
The woodwork in the photo above is very well done. Clearly dimensional lumber was used to create these terraced boxes, which to my eye is much nicer than the coarse creosote finish of railroad ties. I can't tell if the lumber in this photo is treated or not. If not, it's a lock that it will rot and decay in a most undignified way in just a few years. I also wonder if the corners of the boxes have any kind of reinforcement or bracing, as that's where they would tend to come apart.
Sadly no material, including wood, is immune from the "Seattle Slump." Even this low wall made of railroad ties is bowed out. Not quite Hall of Shame material, but disconcerting nontheless.
