Thank you for the quick and thorough response! And glad to be on the forum!
You definitely raised my biggest fear - that the muck would act like lava and not sit in one place. I even thought about putting in coir logs as well, and then putting the muck in between the logs and my current shoreline - but I think it will ultimately be just too wet to work with or stay put.
I think you convinced me that I definitely need a plan B before we commit to bringing the excavator over
