On your team, Eddie...engineering vicariously thru your project to help me on mine this coming summer.
Pub 590 gets into the "seepage control of pipes thru the dam" issue to substantial detail. It does, indeed, speak of a concrete diaphragm to contol seepage, but is is used as a sole unit (not in conjunction with an anti-seep collar). It goes on to say that a collar can be used in lieu of a concrete diaphragm. "If an antiseep collar is used, it should extend into the fill a minimum of 24" perpendicular to the pipe.". All of this (and much more) verbiage is related to installation of a "thru dam principal spillway pipe system". This is where I extrapolate the need for a 48" sq collar.
I fully agree with you on the ability of wet concrete to fill the voids. I think Pub 590 agrees. Consider this idea: Antiseep collars are typically installed as singular units, spaced out along the run of the pipe. Take a look at this solid unit. It is the way I am leaning. I have had discussions with my contractor and he agrees that the neoprene collars with the temporary wood frame are a pain to work with and compact around. When I told him about this product, he was impressed and thinks it will be the answer. Drop down to the antiseep collar (it is within "conventional products"):
Easywayplastics If you haven't done so yet, I highly recommend that you start a nice fire in the fireplace, open a bottle of wine, and spend some quality time with Pub 590. There is alot of technical help in there...I found this link:
Pub 590 link
