Russ,
An embankment dam is typically constructed with a center (vertical) clay core that is trenched 2 to 3 feet into the clay subsoil to prevent water from leaking through or under the dam. A blanket core consists of the same clay mixture as the center core, only it is built on a 3:1 slope of the dam, either on the outside or inside (water side) of the dam. In either case, center core or blanket core, they must be trenched into the subsoil base otherwise more than likely they will leak. I don't have alot of knowlege on the blanket core, but in my situation I do not see why it would not work. If you would like to see a picture of the cross-section of a blanket core, I will send you the website that shows it.
Steve,
