Our 25 year old house is built on pressure treated piligs in a flood zone along the river. We're the third owner so don't know, but the pilings appear to be penta, pressure-treated, 12 inch posts that we understand are four feet deep in the ground and were surrounded by concrete when placed. The pilings support the main floor of the house, which is really the second story, and the roof. When we cut out one post, the treatment appears to have penetrated to all but about a 2 inch core in the middle of the post.
The question is - should we not place landscaping that will be watered around these posts? Living in CA, the ground is moist from rain, and the river about six months a year and dry the remainder.