There can be one or two layer of concrete underneath the ice – one for cooling and one for heating. Immediately below the ice is a layer of concrete. A system of pipes, similar to what is used for refrigeration, is used to cool the chilled concrete layer, and is what keeps the ice, icy. Below the first layer of concrete, there is a layer of insulation, and then sometimes a second heated layer of concrete. Often beneath the heated concrete, there is a base layer of sand and gravel, and below that a ground water drain.
In this case, PRI completed the testing program for the top layer of concrete only, and where creating a flat surface becomes of greater importance to laying a smooth ice surface.