Pub 590 link call your county USDA office and get a hard copy. I have also seen em on Ebay. I would try to wrestle one for nix from the govt.
edit: clean-up means removal of not only the trees, but the reason that they are recipes for leaks....the roots. I will admit, tho, that I cannot vouch for the need to do so if the water level and qty in your structure is minimal...I only know that a fundamental in embankments is no veg at the dam....period.
