The olive caddisfly hatch is very heavy now. However, the trout can trick you in the way they feed. You see a riseform in the pool upstream and you assume the trout is taking adult caddisflies...maybe? He could be taking the emerging caddis pupa just beneath the stream surface. A very effective technique is to fish a Murray's Olive Caddis Pupa size 14 on an 18-inch 6X dropper below a Mr. Rapidan Olive Delta Wing Caddis size 14.
You will have better water levels by coming into the streams off the Skyline Drive or upper reaches of the streams in the Shenandoah National Park. There are many streams to explore in the Park so if you see alot of cars parked in one area try to go to a different area so that you are not fishing behind someone.
My book Trout Fishing in the Shenandoah National Park has the hatch charts, a chapter on reading the water and lists all of the streams in the alphabetical order with access directions. You can also see my digital download video on these streams.
The native brook trout streams in the George Washington National Forest are in great shape so take advantage of them before the water levels get to low in the summer.