The problem with fiberglass is the section modulas is very low compared to steel. The simple way of it is, it bends to easy. I have tried to use fiberglass sheet piles in a couple applications for permenant instalation. It all comes back to how much of it will be sticking out of the ground, and how far in the ground they will need to be installed to get bearing load.

Your best bet is to tell the owner that to do what he wants, you are going to have some upfront costs. First, meet with an engineer that is familar with this type of work. Keep in mind, that is not just any engineer. In general, the engineer will not be able to tell you to much with out soil borings or the load of the building and its size. With out these he can not do much.

You can probally get a soil boring for $750 to $1,500 on the bank. After that you have to come up with a weight and size of building.

With that he can come up with what size, length, and number of piles. Penatration and soil will have lot to do with your lateral loads. As an example, if you only have 10' in soft, wet soil and 10' out and it hits rock, you will get great end bearing load, but it will not resist any lateral loads, you could push it over. But if you have only 5' above soil, it will resist more lateral loads. If it drives 25' and does not hit rock, you can still get bearing load by skin friction, considering the small loads you will be looking for, this will probally be the case, unknown with out soil borings. But if you have 25' of the pile in soil and then 10' out, you can understand how this would resist lateral loads.

One more for your understand about pile loads, it is nothing more than a force calculation. The simplest form is a drop hammer, used for ever. If you pick a certain weight up a certain distance and drop it, it will create a certain donward force. When the object you drop it on stops moving, what ever that force of drop is what the pile is rated at. This is making it very simple, but used for centuries.

This is probably more than anybody wants to know about it, but i get to feel like i actually helped somebody on the board!