The cattle watering pipe likely had some sort of anti-seep collar (one or two of them) around the pipe to keep water from following the pipe and causing a leak. It can be tricky getting proper compaction around the collar as it usually has to mostly be done by hand. I know the two we put in around my overflow pipe were a PIA. A water source pipe for a cattle water source would be lower in the dam and subject to higher head pressure so even more critical to get it installed right.
I have heard (I'm no expert, just a farmer with some construction equipment) that the ideal dam material is not pure clay, but the proper mix of both clay and soil. The reason being clay has such high shrink/swell ratio that it can crack if it dries out too much.
When we were building our dam we used a ruber tired scraper for compaction. Not the perfect implement, because the smooth tires can cause the compaction in layers, whereas a sheepsfoot roller has the sheepsfeet to knead and knit the layers of clay together. In our case the dam was designed with a "bench" for bank erosion control that was supposed to be 5' wide. It ended up more like 10' wide and we ended up making it a road along side the water instead of what it was originally designed for (we used crushed rock along the bank for shore line erosion control so the "bench" became redundant). The point I am trying to make is that our dam is at least 5' thicker than the original design parameters and the original design was pretty robust to begin with. We did it ourselves with a 12 yard scraper pulled by a Challenger track tractor and a Cat D6N XL that we own for our farm use. Needless to say, as we learned to build a pond, we hauled a lot more dirt around than I would have ever been able to afford a contractor to do. The dam is robust, so even if we screwed up a little with compaction layers, there was adequate over build to take care of it. It is dry as a bone on the back side.
Any way, wishing you the best on getting it fixed.
