There is a chance your turtle is OK. Turtles can survive in the wild in the UK. It's too cold for them to hatch eggs, so they don't breed, but some live in ponds near me. They hibernate in the winter. So there's a chance your turtle is living in a drainage ditch or pond somewhere!
There would also be a chance of her getting picked up and rescued at a treatment plant.
They can hold their breath and stay under water for a long time, and most of the pipes are not full of water, so she could have survived going through the pipes.
Of course it's not a good idea to release them (too many can be a problem for our native wildlife).
