I have a pond overflow pipe nearly clogged with grass. It is a 60' horizontal run of 8" ID double-wall poly pipe terminating in a catch basin. It is 25%-75% full of grass, but still has significant flow through it. The grass is growing throughout the length of the pipe like a "beard" and is not discreetly located at the pipe couplings. Chemical treatment last summer killed ~10% of the grass, but was essentially ineffective. The pipe is ~3' below finished grade and the surface is planted in Timothy hay and clover. The nearest tree is a Weeping Willow ~50 feet away. I am looking for advice as to what type of cutter(s) I should recommend to the owner to use with his rodding equipment to clear this clog. Since this will most likely be an annual maintenance activity, what cutter(s) should be employed to keep the grass in check? This grass is very tough and I can yank out (break) one or two strands bare handed. If I twist three or more strands together like a rope, a winch is required to break it. I am inclined to think this grass should be chopped/ground up beginning at the catch basin to allow it to be flushed out as it is cut. Please advise. Thank you in advance for sharing your expertise.