Ask them for a clothing list. I do not know if you are a guy or gal - I suspect from your forum name that you are female. If not, the following suggestions still apply, but I did target them to a female.

Trail work is very dirty and rough on clothes. You will want at least two changes of clothing - one to wear while the other is drying from being washed. I used to work in a coal mine- safety regulations require that you have arms and legs covered. A long sleeve shirt with sleeves that roll up is good. This will save you from numerous scratches and sunburn. Same with shorts. May be better to have long pants. Do not try to be stylish -- have plenty of room for bending. Somewhat loose, but not so loose that you will get clothing caught on branches and brush. Also, forget the low-riders - bend down and expose flesh and you will get eaten by bugs and dirtier than ever. I would not go for the super-light weight backpack variety of clothes -- get something that is a little more tough that still dry quickly. I think Columbia makes some reasonable priced tough clothing.

Bring something to keep your hair out of your face when wearing a hard hat. A handkercheif that is large enough to wrap around your head works and you can also wet it when it gets hot. It looks dorky, but feels a lot better than hair hanging out.

A good pair of work gloves that fit properly will make a huge difference. They will probably have gloves, but my experience is that they seldom will fit. It is worth it to buy your own. The cotton work gloves with little grippy dots work well.

Bring a little repair kit - needle and thread, a few exta buttons.

Even if rinsing clothes in cold water does not get them clean, it will get out the sweat and dust and they will feel a LOT better.

If they require steel toed shoes, I find that low-cut shoes are a lot more comfortable than boots. They even make steel toed tennis shoes!

Take at least 2 kercheifs - it is nice to have something to wipe your hands on. A kercheif can easily be dipped in a stream and put around your neck - sort of natural air condioning.

Take all opportunities to dip in the stream. If you are not in a social situation that approves of skinny dipping, bring a light weight swimsuit or bikini. No matter how cold the water is, it will feel wonderful when you get out! Ask if your base camp will provide solar showers. If not, you may think of bringing your own small solar shower collapsable bag.