So heres what im looking at. There is a major downhill flowage into a potential customers yard. currently there is a 12" catch basin with 4" connectors at the top edge of his property and im assuming a french drain underneath all of the river rock. he tells me the water runs right past the catch basin and it pretty much does not work, and he also tells me he would like to remove all of the river rock to regain a bit of his yard. so the water is too much/running right past a 12" basin and or the whole drain system is clogged up. i have personally done some drainage work but not much with french drains, not that i cant but i have some questions about where to go from here. i have been told that if you try to do a french drain underneath grass, it will dry out the grass too much. what is the truth to this is it going to kill the seed/sod or is there a trick to it? if i end up not going the french drain route i thought about adding an extra basin and setting up both basins with an extra drain outside the backside of the hill. or maybe a combination of both... what would you guys do?