Dave, Luckily on the second day of digging on the tunnel, that night it rained for a couple hours. when Igot up in the morning to go back out and dig the tunnel was full of water. I had to use my shop vac to empty it. My soil is solid clay once you get to about 2 feet down so it holds the water. I am so glad that happened, but I was pissed the day that it happened, I emptied my shop vac 20 times, so there was about 160 gallons of water in there and I wasn't even halfway done with the tunnel. but what was good about it was it made me realize that I had to do something for drainage or else every time it would rain the tunnel would fill up with water. So after I got the whole tunnel dug. at each end of the tunnel before I put the pipe in. I dug down another 3 feet and filled those holes with gravel. the holes are about 2 feet wide and 3 feet deep. It rained then a few days after I got the tunnel finished and the water drained immediately. no standing water whatesoever in there. so the holes with gravel did the trick. Now, we've had 2 very bad downpours since then where it just rained so hard and so fast in a short amount of time and the drains weren't able to keep up, and the tunnel did fill up about halfway both times, and then it took about an hour for the water to drain. but I can live with that. we don't get those kind of rains very often. and I know in just a normal rain it's going to drain properly. but if it didn't rain that first night of digging I probably would not have though about making drains, and it would have been so much harder to add drains after the pipe was in and everything done. so. I'm really happy about that.