BENEDICT SMARTMIX®10 BIOFILTRATION TRANSITION SAND Benedict SmartMix® 10 Biofiltration Transition Sand is manufactured to comply with CRC Adoption Guidelines for Stormwater Biofiltration Systems (July 2015) as the transition sand (middle layer). It is a medium to coarse washed sand with a targeted particle range to assure excellent hydraulic conductivity (that is higher than the biofiltration filter media that sits above it).