I respectfully question the wisdom of a concrete pour between 2 anti-seep collars. The collars do nothing more than to stop the lateral flow of a trickle along the drain pipe...kinda like following a tree root. It creates a zone to force the flow to divert directly away from this easy route. As it is forced away, it is faced with finding a way to get back to this "pipe highway" to continue it's journey. A 48" sq collar hinders this return to the pipe by forcing the trickle to follow 24" directly away from the pipe, then 24" back (180 degree turn) to try to find it and continue. Creating a monolithe with concrete defeats 48" of travel, particularly the severe change of travel direction to get back to the "highway". Also, and I can't provide the hydrological answer here, but how good is the seal between concrete and clay, particularly if it is rough finished (compared to the seal against a very smooth medium like neoprene or PVC)?
