While Copper is an essential micro nutrient in soil excess quantities, just like any other nutrient, can result in problems, poor growth, plant diseases, etc. Copper could accumulate in more than micro nutrient quantities if used in the gaden, but it would take a long time and be in a very limited area since it would not move about in the soil.
If copper was a real problem organic gardeners would not be using copper strips for slug control, moving water to the garden, or one of the many other things gardeners often use copper for. I have a tutour made of copper pipe as well as coils used to help support some plants that tend to flop around and the soil tests do not indicate an increase in copper in the soil, at least yet.

Thanks for the response, that's very helpful. It does seem like whatever trace amounts could come from copper would be hard to be concentrated enough to cause the damage you are referring to. I may take extra precaution where the pipe enters the soil

I have a site in fla with high levels of copper in the ground due to the use of copper sulfate on the citrus trees, formerly.

Over 4 -7 ppm is considered high, depending on ph and soil type. You can figure out roughly how many pounds of soil are around your trellis (there are about 2 million pounds in the top half-foot of an acre), and the approximate weight of the trellis, and then calculate that if the entire thing dissolved (which would take hundreds of years or more in the absence of some reaction) how many ppm would it amount to?